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US06CICV02 Unit -1 Dr. N. K. Patel

Natubhai V. Patel College of Pure & Applied Sciences

B.Sc. Semester VI

Industrial chemistry (Vocational)

US06CICV02: Heavy and fine organic chemicals

UNIT – 1 SYLLABUS

Fischer-tropsch synthesis- Examples, Chemicals derived from acetylene, propargly alcohol, 1,

4-butanediol, acrylates, vinyl esters, vinyl chloride. Pyridine and picolines, phenol, acetone,

resorcinol, phthalic anhydride,

1.0 VINYL CHLORIDE

1.0.1 From Acetylene and Hydrogen chloride

1.0.1.1 Raw materials

Basis-1 ton vinyl chloride

Acetylene 880 lb

Anhydrous hydrogen chloride 1200 lb

Mercuric chloride 2 lb

1.0.1.2 Reaction

1.0.1.3 Manufacture

The vapour-phase reaction between acetylene and hydrogen chloride in the

presence of a mercuric chloride catalyst yields vinyl chloride. Anhydrous hydrogen chloride

(slight excess) and dry, purified acetylene gas (free from ammonia, hydrogen sulfate,

phosphine, and arsine) are mixed and fed to a reactor containing carbon pellets

impregnated with mercuric chloride. The reaction is exothermic, so a coolant is circulated

around the tubes to hold the reaction temperature between 160 and 250°C.

Effluent gases from the reactor are cooled first by heat exchange with cold reactants

and finally condensed and fractionated in a refrigerated column from which unreacted

acetylene and hydrogen chloride go overhead. The acid-free monomer or "crude" is further

fractionated in a second refrigerated column in which vinyl chloride goes overhead, and by-

product ethylidene chloride and aldehydes are removed as bottoms. The condensed vinyl

chloride is stabilized with a small amount of phenol before going to storage.

Re

acto

r

Re

frig

era

ted

co

lum

nm

Co

lum

n

Catalyst Acetylene and HClVinyl chloride

(stabilized)

Phenol

Bottoms to

pot still

Hydrogen

chloride

Acetylene

Figure: From Acetylene and Hydrogen chloride


1.0.2 By Pyrolysis of ethylene dichloride


Basis- 1 ton vinyl chloride

Ethylene dichloride 3300 lb

1.0.2.2 Reaction

1.0.2.3 Manufacture

Vaporized ethylene dichloride is dried and passed over a contact catalyst (e.g.,

pumice or charcoal). The catalyst usually packed in stainless steel tubes directly heated in a

cracking furnace. At 50 psig, with the effluent gases at 900 to 950°F, a 50 per cent conversion

and 95 to 96 per cent yield is attained.

The hot effluents gases from the furnace are quenched by direct contact with a

stream of ethylene dichloride uncondensed gases are sent to an indirect (surface)

condenser to recover the remainder of the condensable vapor; the non-condensable are

scrubbed with water to recover hydrogen chloride.

The combined liquid streams from the quencher and condenser are fed to a

fractionation tower operated sufficient pressure to yield vinyl chloride by condensing the

overhead vapors in a water condenser. The vinyl chloride is sent to storage. The bottoms from

the still are sent to a second still where ethylene dichloride is separated from "heavy ends"

and passes overhead. Condensed ethylene dichloride is recycled, part to the quencher and

part to the process feed tank.

In most plants the vinyl chloride facilities are built adjacent to the ethylene dichloride

plant so that the vinyl chloride raw materials are essentially ethylene and chlorine.

In one large, plant where large amounts of ethyl chloride are made, some of the

ethyl chloride is dehydrochlorinated to produce vinyl chloride in a process similar to that

described starting with ethylene dichloride.

1.0.3 By Reaction between ethylene dichloride and Caustic soda

A process similar to the thermal process just described involves heating the ethylene

dichloride in the presence of caustic soda. Ethylene dichloride is mixed with a water solution

containing 6 per cent NaOH in a 2 to 1 mole ratio of dichloride to alkali. This mixture is

charged to a steel reactor at 150 psig where it is allowed to react for 2 to 3 min at 290"F. The

reaction is:

An almost quantitative yield is attained at a 90 per cent conversion of the ethylene

dichloride.

DryerCracking

furnaceQuencher

Co

lum

n

Dis

till

ati

o

n t

ow

er

Ethylene

dichloride

HCl to absorber

Vinyl chloride

Heavy ends

Recycle etylene dichloride

Figure: By pyrolysis of ethylene dichloride


Overflow from the reactor is cooled and pumped to a pressurized column where vinyl

chloride goes overhead to storage; the bottoms are distilled to separate unconverted

ethylene dichloride and some water vapour from the valueless bottoms (a mixture of high

boiling organics and brine). The ethylene dichloride is separated from accompanying water

in a decanter and recycled. The overall yield of vinyl chloride based on ethylene dichloride is

90 per cent.

Considerable interest has been shown recently in ethylene oxy-chlorination processes

in which the chlorinating agent is oxygen and hydrogen chloride. The process has not yet

been standardized and may involve either chlorine production prior to contacting ethylene

or in the presence of ethylene.

1.0.4 Uses

Per Cent

Flooring 14.5

Sheet 14.5

Adhesives, coating and bonding 13.3

Wire and cable (extrusion) 13.1

All other extrusion, e.g. garden hose 10.6

Film 5.7

Records 5.5

Slush and rotational molding 2.8

Miscellaneous and export 20.0

100.0

Vinyl chloride monomer has only one general end-use -in plastics. At one time the

vinyl plastics were the most important of all synthetic plastics. They are now surpassed by

polyethylene, but far ahead of all others.

The largest uses of PVC are iii sheeting; moulding and extrusion (e.g. for phonograph

records and garden hose); and in construction, particularly in flooring. All of these uses

appear destined to grow, with use in building leading the way, especially if rigid vinyl panels

are more widely accepted.

1.1 VINYL ACETATE

1.1.1 From Acetylene and Acetic acid


Basis-1 ton vinyl acetate

Acetylene 650 lb

Acetic acid 1420 lb

Vaporizer

Re

acto

r

Co

lum

n

Vin

yl

ace

tate

co

lum

n

Ace

tic a

cid

co

lum

nAcetylene

Acetic acid

Light

ends Vinyl acetate

Heavy

endsAcetic acid (recycle )

Figure: From acetylene and acetic acid


1.1.1.3 Reaction

1.1.1.4 Manufacture

The vapour-phase reaction between acetylene and acetic acid in the presence of a

zinc acetate catalyst yields vinyl acetate.

Acetylene is specially purified to remove hydrogen sulfide and phosphorus

compounds. It is then mixed in slight excess with vaporized acetic acid and fed to a multi-

tubular fixed-bed reactor containing catalyst of zinc acetate deposited on activated

carbon (10 per cent Zn). Reaction is exothermic so the rector is cooled by circulating oil

around the tubes. Reactor temperature is maintained at 350 to 4000F.

The reactor effluent is condensed and fed to a light ends column, where acetylene, methyl

acetylene, propadiene, and other light ends are removed from the top of the column. The

acetylene must be re-purified before it may be recycled.

Vinyl acetate is distilled overhead in vinyl acetate column. Recycle acetic acid is

separated from heavy ends in a recovery column.

Conversion per pass is 60 to 70 per cent. Yield is 97 to 99 per cent based on acetic

acid; 92 to 95 per cent based on acetylene.

1.1.2 Other processes

Vinyl acetate was formerly made by a liquid phase process in which acetylene and

acetic acid were reacted in the presence of a mercury catalyst Yields (75 to 80 per cent)

were considerably lower than is now attained in the vapour-phase process.

A somewhat similar process is used by one manufacturer starting with acetaldehyde

and acetic anhydride to produce to produce ethylidine diacetate.

The ethyIidine diacetate is then pyrolysed to form vinyl acetate and acetic acid:

One new plant makes vinyl acetate from ethylene and acetic acid by a process similar to

that for making acetaldehyde from ethylene (see Acetaldehyde). The overall reaction is as

follows:

As in the acetaldehyde process, cuprous chloride is used to oxidize the palladium metal

back to the palladous ion.

1.1.3 Uses

Per cent

Polyvinyl acetate 52

Polyvinyl alcohol 18

Polyvinyl butyral 10

Polyvinyl copolymers 15

Miscellaneous 5

100

Vinyl acetate is utilized entirely in its polymerized form (polyvinylacetate) or

derivatives thereof. Polymers of varying molecular weight (usually between 50,000 and

100,000 may be made comparatively easily. The polymers are colorless, transparent, and

tough, and they form films of good heat-sealing qualities.

The use of vinyl acetate lattices in emulsion paints (so-called plastic paints) is

extremely promising and may result in tremendous volume. Public acceptance has been

excellent, and may except PVA-based paint to overtake the popular butadiene-styrene

type. PVA -based paints are not only cheaper than other latex paints, but they have better

outdoor weatherability.

1.2 ACRYLATES

Acrylic acid (CH2 = CHCO2H) (propenoic acid), a moderately strong carboxylic acid,


is a colourless liquid with an acrid odor. Acrylates are derivatives of both acrylic and

methacrylic acid (CH2 = CH (CH3) CO2H).

1.2.1 Manufacture

Various methods for the manufacture of acrylates are summarized in Figure, which

shows their dependence on specific hydrocarbon raw materials. For a route to be

commercially attractive, the raw material costs and utilization must be low, plant investment

and operating costs must not be excessive, and the waste-disposal charges must be

minimal. The favorable supply and cost projections for propylene suggest that all new

acrylate paints will employ propylene oxidation technology for at least the next two

decades. This two-stage process gives first acrolein and then acrylic acid.

The most important factor in the oxidation process is catalyst performance. The

overall yield of acrylic acid oxidation reaction steps of this process is in the range of 76-86%,

depending on the catalysts and conditions employed. In the separations step, about 95% of

the acrylic acid is extracted from the absorber effluent with a solvent chosen for high

selectivity for acrylic acid and low solubility for water and by-products. Acrylic acid esters are

produced in minimum purity of at least 98.5-99%.

Process based on acetylene-the high pressure Reppen process (BASF) and the

modified Reppen process (Rohm and Hass)- or on acrylonitrile were still being used in the late

1970s for the production of acrylic acid and esters. The original Reppe reaction uses nickel

carbonyl with acetylene and water or alcohols to give acrylic acid or esters. The original

Reppen reaction requires a stoichiometric reaction of nickel carbonyl to acetylene. The

Rohm and Hass modified or semi catalytic process provides 60-80% of carbon monoxide from

a separate carbon monoxide feed and the remainder from nickel carbonyl. The reactions for

the synthesis of ethyl acrylate are as follows:

The stoichiometric and the catalytic reactions occur simultaneously, but the catalytic

predominates the process is started with stoichiometric amounts, but afterward, carbon

monoxide, acetylene and excess alcohol give most of the acrylate ester by the catalytic

reaction. The nickel chloride is recovered and recycled to the nickel carbonyl synthesis step.

Methane

CH4

Synthesis gas

CO + H2

CO Methanol

CH3OH

Formaldehyde

HCHO

Ketene

C2H2O

Acetic acid

C2H4O2

Propiolactone

C3H4O2

Acrylic acid

C3H4O2

Acetylene

C2H2

Propionic acid

C3H6O2

Acrylic acid

C3H4O2

Ethylene

C2H4

Propylene

C3H6

Acrylonitrile

C3H3N

Acrolein

C3H4O

Acrylic acid

C3H4O2

Methyl acrylate, Ethyl acrylate, Butyl acrylate

ROH

CH2O

ROH ROH ROH

O2

O2

CO

H2

CO

O2

Pd

CO

O2

ROH

Pd

O2

NH3

CO

H2O

Ni

CO

ROH

Ni

ROH

H2SO4(- H2)

Figure: Acrylates manufacturing process


The main by-product is ethyl propionate which is difficult to separate from ethyl acrylate.

However, by proper control of the feeds and reaction conditions, it is possible to keep the

ethyl propionate content below 1%. Even so, this is significantly higher than the propionate

contents of the esters from the propylene oxidation route.

BASF used a high pressure, catalytic route based on the Reppen process at 200 0C

and 13.9 MPa in the presence of tetrahydrofuran as an inert solvent. This process gives

acrylic acid directly Nickel carbonyl creates a safety and pollution control problem since it is

volatile, has little odor, and is extremely toxic.

The acrylonitrile route, based on the hydrolysis of acrylonitrile, is also a propylene

route since acrylonitrile is produced by the catalytic vapour phase ammoxidation of

propylene.

The yield of acrylonitrile based on propylene is similar to the yield of acrylic acid

based on the direct oxidation of propylene.

More than one-third of the 1977 worldwide manufacturing capacity for acrylic acid

and esters was based on the acetylene process. However, raw material supply and cost

trends indicate that this process been phased out in favour of propylene-based plants. All

new plants use propylene oxidation. The acrylonitrile route is commercially unattractive

because in addition to high raw material cost, large amounts of sulfuric acid-ammonium

sulfate wastes are produced; these wastes can be treated in waste acid plants for recycling;

however, the investment is relatively high compared with the cost of the rest of the process.

1.2.2 Specialty acrylic esters

Higher alkyl acrylates and alkyl-functional esters are important in copolymer product,

in conventional emulsion applications for coatings and adhesives, and as reactants in

radiation cure coating and inks. In general, they are produced in direct or transesterification

batch processes because of their relatively low volume. Most important higher alkyl acrylates

is 2-ethylhexylacrylate prepared from available oxo alcohol2-ethyl-1-hexenol.

1.2.3 Storage and handling

Acrylic acid and ester are stabilized with minimum amount of inhibitors such as MEHQ

(monomethylether of hydroquinone) consistent with stability and safety. Acrylic esters may

be stored in mild or stainless steel or aluminum. Acrylic acid is corrosive to many metals and

can be stored only in glass, stainless steel, aluminum, or polyethylene-lined equipment. The

relatively low flash points of some acrylates create a fire hazard, and the ease of

polymerization must be borne in mind in all operations. The lower and upper explosive limits

for methyl acrylate are 2.8 and 25 vol%, respectively. Corresponding limits for ethyl acrylate

are 1.8 volume/% and saturation, respectively. All possible sources of monomers must be

eliminated.

1.2.4 Health and safety factors

The toxicity of common acrylic monomers ranges from moderate to slight. They can

be handled safely by established practices; the TWA for all is 10 ppm in air over an 8-h shift.

The cornea is particularly sensitive. The lower acrylate esters can be skin sensitizers.

Allergic reactions of sensitive individual may include smarting of the eyes, headache, and

skin eruptions. Threshold limit values (TLVs) for an 8-h day have been recommended by the

ACGIH as 10 and 25 ppm for methyl and ethyl acrylates, respectively. Vapours of the higher

acrylates are appreciably less irritating than those of methyl and ethyl acrylates.

Acrylic acid is strongly corrosive to the skin and eyes. Its oral toxicity is similar to that of

methyl acrylate, but it may also cause severe intestinal burns and damage to the gastric

tract. It is also moderately toxic in skin absorption tests; superficial destruction of tissues may

occur, but the skin subsequently heals. High vapour concentrations are very irritating to the

eyes and nasal passages. There are few toxicity data on functional acrylate monomers.

Without specific information, precautions should be taken to prevent contact with the liquid

or any undue exposure to the vapor of any acrylic ester. Further-more, some derivatives, such as the alkyl-α-chloroacrylates, are powerful vesicants and can cause serious eye injuries. Thus,

although the toxicities of commonly available commercial acrylates are moderate to slight,

this should not be assumed to be the case for compounds with chemically different

functional groups.


1.2.5 Uses

They are used primarily to prepare emulsion and solution polymers with wide industrial

applications: Acrylate polymer emulsions are used in coatings, finishes, and binders for

leather, textiles, and paper, as well as in the preparation of paints, floor polishes, and

adhesives. Solution polymers are used in the industrial coatings. The polymeric products vary

widely in physical properties, depending upon the controlled variation in the ratios of

monomers used in their preparation, cross-linking, and molecular weight. All the polymeric

products are resistant to chemical and environmental attack and have excellent clarity and

strength. Table gives properties for commercially important acrylic esters.

1.3 PROPARGYL ALCOHOL

2-propyn-1-ol, the only commercially available (acetylenic primary alcohol, is a

colorless, volatile liquid with a mild geranium like odour. It is miscible with water and many

organic solvents. It has three reactive sites, i.e., a primary hydroxyl group, a triple bond, and

acetylenic hydrogen, making it an extremely versatile chemical intermediate.

It can be esterified in a normal manner with acid chlorides, anhydrides, and

carboxylic acids. It reacts with aldehydes or vinyl ethers in the presence of acid catalysts to

form acetals. Using low temperature conditions, oxidation with chromic acid gives propynal

(HC=CCHO) or propynoic acid (CH=CCOOH), which may also be prepared by electrolytic

oxidation. Various halogenating agents have been used for replacement of hydroxyl with

chlorine or bromine. Hydrogenation gives allyl alcohol, its isomer propionaldehyde, or

propanol. In the presence of acidic mercuric salts, water adds to form acetol (1-

hydroxyacetone). Under similar conditions, alcohols give ketals which hydrolyse to acetol.

Halogens add stepwise to give almost exclusively dihalo allyl alcohol (CHX=CXCH2OH).

Propargyl alcohol combines with aldehydes in the presence of copper acetylide catalysts to

give acetylienic glycols. (RCH(OH)C=CCH2OH). In the presence of dialkylamines and

pormaldehyde (methylolamines), dialkylaminobutynol (R2NCH2C=CCH2OH) are formed. Two

equivalents of organomagnesium halide give a Grignard reagent of propargyl alcohol

capable of further reactions. Cuprous salts catalyze the oxidative dimerization of propargyl

alcohol to 2,4-hexadiyne-1,6-diol.

1.3.1 Manufacture

Propargyl alcohol is a by-product of butynediol manufacture (Butynediol is

manufacture by the ethynylation of formaldehyde). In the usual high pressure butynediol

process, about 5% of the product is propargyl alcohol. The commercial product is specified

as 97% minimum purity, determine by acetylation or gas chromatography.

It is shipped in unlined steel container and handled in standard steel pipe or brainded steel

hose; rubber is not recommended.

1.3.2 Toxicity

Although propargyl alcohol is stable, violent reactions can take place in the

presence of contaminants, particularly at elecated temperatures. Avoid heating with

alkaline or strongly acidic catalysts. Weak acids, eg, carboxylic acids, are used as stabilizers.

The usual precautions against ignition of vapours must be observed. Propargyl alcohol is a

primary skin irritant and a severe eye irritant; it is toxic and good ventilation when being used.

1.3.3 Uses

Propargyl alcohol is a component in oil -well acidizing composition. Corrosion and

hydrogen Embrittlement of mild steel in mineral acids are inhibited. It is employed in metal

pickling and plating operations, and is used as an intermediate in the preparation of the

miticide Omite, and sulfadiazine.


1.4 ACETONE

1.4.1 From Isopropyl alcohol


Basis-1 ton acetone

Isopropyl alcohol 2,435 lb

1.4.1.2 Reaction

1.4.1.3 Manufacture

Acetone is produced by the catalytic dehydrogenation of isopropyl alcohol.

Isopropyl alcohol vapors are preheated (by heat exchange with hot effluent gases from the

reactor) and passed into a reactor containing a brass or copper catalyst. Reaction

conditions are usually 5000C and 40 to 50 psi. The hot reaction gases containing acetone,

isopropyl alcohol, and hydrogen pass through a water-cooled condenser and then into a

water scrubber, where final traces of isopropyl alcohol and acetone are removed from the

non-condensable hydrogen. The water solution from the bottom of the scrubber is mixed

with condenser product and fed to a fractionating column. Concentrated acetone is taken

overhead, and an isopropyl alcohol-water mixture is removed from the bottom of the

column. To recover isopropyl alcohol, the bottoms are led to a column, where a binary

constant boiling mixture containing 91 per cent isopropyl alcohol is taken off the top and

water is discharged at the bottom. The 91 per cent isopropyl alcohol may be recycled

without further purification. The water from the bottom of the alcohol concentrating column

is reused in the scrubber.

One plant using the dehydrogenation process uses a catalyst of zinc oxide (7 to 8 per

cent) deposited on pumice. The reaction is carried out at 3800C to give a claimed

conversion of 98 per cent per pass. In order to retain catalyst activity, hydrogen is recycled

through the reactor with the isopropyl alcohol feed (1:1 molar ratio). Every ten days the

catalyst is regenerated at 5000C with gas containing 2% oxygen and 98 per cent nitrogen.

The catalyst is said to have a life of six months.

In another modification of the processes described, a combined oxidation-

dehydrogenation process is used. Air saturated with isopropyl alcohol vapors is passed

through a reactor containing a catalytic bed of silver or copper maintained at a

temperature of4000C to 6000C. The hot gases are partially cooled and scrubbed with water;

nitrogen is released to the atmosphere. The remainder of the process is similar to the straight

Vaporizer Reactor

Scru

bb

erAir

(optional)

Isopropyl

alcohol

Water

Figure: From Isopropyl alcohol

Co

lum

n

Co

lum

n

Isopropyl alcohol and water

Water

Nitrogen or Hydrogen

Acetone


dehydrogenation process. The yield (85 to 90 per cent) is also about the same.

It is possible to carry out both processes at atmospheric pressure, but by using 40 to 50

psi in the reactor – condenser - scrubber system, both equipment size and amount of water

required are significantly reduced.

1.4.2 Other methods

Acetone is recovered as one several products resulting from the vapor phase

oxidation of butane. It is also produced as a co-product with phenol in the oxidation of

cumene, in the manufacture of hydrogen peroxide from isopropanol and in the

manufacture of synthetic glycerin. A small amount of acetone is still produced as a co-

product with butanol by a fermentation process.

Acetone may also be produced directly from propylene by oxidation in the presence

of a palladium chloride- copper chloride catalyst. The process is similar to the Wacker

process for the oxidation of ethylene to acetaldehyde.

1.4.3 Uses

Per Cent

Methyl isobutyl ketone 25

Methyl methacrylate 15

Methyl isobutyl carbinol 07

Miscellaneous chemicals 20

Solvent 25

Miscellaneous 08

100

1.5 PHENOL

1.5.1 Benzenesulphonate process


Basis-1 ton phenol

Benzene 2,000 lb

Sulfuric acid (93%) 3,500 lb

Caustic soda 3,400 lb

Steam 4,000 lb

Electricity 80 kwhr

Vaporizer Sulfonator

Neutralizing

tank Filter

Fusion

potAcidifier

Crystallizer

Va

cu

um

co

lum

n

Ste

am

stil

l

Benzene

Sodium

sulfate

Water

Sulfuric

acidCaustic soda

Water

Water

Phenol

Dilute phenol

wash water

Sodium

sulfite

Sodium

salfate

Recovered sodium sulfite sludge

Figure: Benzenesulfonate process

Sulfur

dioxide


1.5.1.2 Reaction

1.5.1.3 Manufacture

Benzenesulfonic acid is prepared in a sulfonator by the action of concentrated

sulfuric acid on benzene. Water is formed during the reaction and must be removed

because of its diluting effect on the acid. When the concentration of the sulfuric acid drops

below 78 per cent H2SO4, the sulfonating action ceases. In order to circumvent this, the

sulfonation is carried out continuously in the vapor phase by passing benzene vapors up

through a reaction zone countercurrent to concentrated (93%) sulfuric acid. The benzene

reacts with the acid and also azeotropically removes the water of reaction. The reaction

zone is maintained at an approximate temperature of 1500C. The sulfonation proceeds until

only a few per cent of free sulfuric acid remains, which is then directly neutralized in the

neutralizing tank. The benzene, water and acid vapors are condensed, and the benzene is

recovered.

The sulfonation product is added as rapidly as possible to the neutralizing tank, which

contains a solution of sodium sulfite. Sodium carbonate also may be used. Sulfur dioxide is

boiled off and piped to the acidifiers. The resultant mixture of sodium benzenesulfonate and

sodium sulfate is filtered at boiling temperature. The sodium sulfate precipitates out of the hot

liquors and remains on the filter; the sodium benzenesulfonate mother liquor is pumped to a

fusion pot.

The eacted-iron fusion pot is charged with fused caustic soda and heated to 3000C

by a gas or oil fire. At this temperature (300 to 3200C) the sodium benzenesulfonate is

introduced under the surface of the caustic melt. About 3moles of alkali per mole of

sulfonate are employed. The temperature is maintained at 300 to 3100C for several hours and

finally at about 3800C for 1 hr. After the fusion is completed (5 to 6 hr), the pot is emptied,

and the melt is diluted with water or dilute phenol wash water from the previous charge. The

sodium phenate-sodium hydroxide-sodium sulfate solution is acidified with sulfur dioxide

obtained from the sulfonic acid neutralization. A small amount of sulfuric acid is generally

needed to complete the acidification. The crude phenol separates as the upper layer over

an aqueous solution containing sodium sulfite and sodium sulfate. The phenolic layer is

decanted and distilled under vacuum to yield refined phenol. The aqueous layer is treated

with steam to remove residual phenol, and this distillate is used as make-up water Part of the

sulfite sludge is used for neutralizing the Benzenesulfonic sulfuric acid mixture, and the

remainder may be re-crystallized and dried to yield anhydrous sodium sulfite (by-product).

Phenol of USP quality is obtained in about an 85 per cent by weight yield based on benzene.

In some plants the fusion melt is diluted with a minimum amount of water so that all

the sodium sulfite does not go into solution. Undissolved sodium sulfite is separated by settling

and centrifuging, and the clarified sodium phenate solution is sent to the acidifiers.

1.5.2 Cumene peroxidation process


Basis- 1 ton phenol and 1,220 lb acetone

Cumene 3,400 lb

Air 10,000 cu ft

Sulfuric acid Small

Emulsifying agent Small

1.5.2.2 Reaction


1.5.2.3 Manufacture

The Cumene peroxidation process for the manufacturing of phenol involves the liquid

– phase air oxidation of Cumene to Cumene hydroperoxide, which in turn is decomposed to

phenol and acetone by the action of hot acid.

The Cumene (isopropyl benzene) may be manufacture by either liquid or vapor-

phase alkylation of benzene with propylene. In the liquid phase, the alkylation catalyst is

usually sulfuric acid, vapor phase it is phosphoric acid absorbed on a carrier.

Purified cumene is mixed with purified recycle cumene and fed to the oxidation

vessel where it is emulsified with a dilute soda ash solution. To maintain best reaction

conditions the cumene is dispersed in the aqueous alkaline phase held at pH 8.5 to 10.5. The

water-oil ratio may vary from 2.0 to 5.0. Other additives are small amounts of an

emulsification agent, e.g., sodium sterate, and some cumene hydroperoxide to eliminate the

induction period of the cumene peroxidation reaction. The emulsion is contacted with air

and held at 1300C until 35 to 50 per cent of the cumene is converted to the hydroperoxide.

Catalysts and promoters are often used in the peroxidation step to the extent of 0.2

to 0.5 per cent of the total material present. Catalysts may be copper, manganese, or

cobalt salts; promoters include formats, amines, and terephthalic acid. Yields of cumene

hydroperoxide may be improved by operating at lower temperatures (100 to 1100C) and

accepting lower conversions. In one modified process, sequence of 3 to 4 reactors are

operated at successively lower temperatures.

The crude mixture from the oxidizer, about 80 per cent cumene hydroperoxide, is fed

to acidifier containing a 10 per cent solution of sulfuric acid. Here, with good agitation to

keep the two liquid phases in intimate contact, the cumene hydroperoxide is cleaved to

phenol and acetone. The reaction is usually carried out under conditions of mild temperature

(45-65°C) and pressure. A typical analysis of the resulting product is as follows: acetone-9.1 per cent; phenol-15.2 per cent; acetophenone-0.8 per cent; α-methylstyrene-1.5 per cent;

and cumene-73.4 per cent.

The products may be separated either by distillation or by a combination of

distillation and extraction. In the process shown in the How diagram, acetone is removed

overhead in the first column. The bottoms from this column are then vacuum-distilled to send unreacted cumene and by-product α-methylstyrene would lower the peroxidation

overhead. If this impure cumene were recycled as such, the methylstyrene would lower the

peroxidation yield. Hence the recycle cumene must be purified. This can be done by catalytic hydrogenation of the α-methylstyrene to cumene, or by careful fractionation. In the

latter case, α-methylstyrene is available foe by-product disposal.

The bottoms from the vacuum still are further distilled to separate by-product

acetophenone from phenol is the overhead product.

Figure: Cumene peroxidation process

Hydrogenator

Oxidizer

Acidifier

Separator

Emulsifier

Impure cumene recycle

Phenol

Acetophenone

Acetone

Recycle acid

Sulfuric

acid Dis

till

ati

on

co

lum

n

Va

cu

um

co

lum

n

Fin

ish

ing

co

lum

n

Cumene

Hydrogen

Air


In the combination distillation-extraction process (not shown in the flow diagram) the

bottoms from the acetone still are extracted at 70 to 900C with water (1 lo 6 weight ratio).

Most of the phenol and about 25 per cent of the acetophenone are extracted. The residual

cumene may be freed of residual acetophenone by distillation and is then hydrogenated to convert α-methylstyrene to cumene. Phenol and acetophenone may be separated by butyl

acetate extraction of the phenol followed by distillation of the extract to yield phenol and

butyl acetate; distillation of the raffinate yields acetophenone and water.

1.5.3 Uses

Per Cent

Phenolic resins 50

Caprolactam 10

Alkyl phenols 10

Bisphenol-A 07

Miscellaneous and export 23

100

There is an increase in demand for new phenol derived plastics and for speciality

chemicals. Three classes of phenol derived plastics, epoxies, caprolactam, and

polycarbonates have great potential for growth. Phenolic resin use is also expected to grow,

at least moderately, for plywood and particleboard adhesives and for laminating resins. In

the chemical field, the manufacture of alkylated phenols, for nonionic surfactants, is

expected to require considerably larger quantities of phenol. Use in adipic acid

manufacture may also increase moderately.

1.6 PYRIDINE AND PICOLINES

Pyridine, C5H5N, is a six-membered heterocyclic compound containing nitrogen

atom. Pyridine and its homologues are commonly called pyridine bases. The first pyridine derivative, 2- methyl pyridine (α - picoline) was isolated from coal tar in 1846 by Anderson. In

185, Anderson obtained pyridine and dimethyl pyridine form bone oil.

Compounds containing a pyridine ring, such as vitamin B6 (pyridoxine), nicotinamide,

nicotinic acid, the coenzymes nicotinamide adeninedinucleotide (NAD) and reduced NAD

(NADH), and many alkaloids play important roles in metabolism. Pyridine bases are widely

used in pharmaceuticals including nicotinamide and nicotinic acid. Similarly, pyridine

derivatives are important insecticides and herbicides due to their high bioactivity. Further,

they are used as adhesives for textiles and as chemicals, solvent and catalysts.

1.6.1 Pyridine and alkyl pyridine

Pyridine and alkyl pyridine are produced commercially by synthesis well as by

isolation from natural sources such as sources such as coal tar. Commercially important

compounds are pyridine 2-methyl pyridine, 3-methyl pyridine, 4-methyl pyridine, 2,6-

dimethylpyridine, 3,5-dimelhylpyridine, and 5-ethyl – 2 – methyl pyridine.

1.6.1.1 Manufacture

a) Separation from Tar

Pyridine bases are constituents of tars, they were isolated from coal tar or coal gas

before synthetic manufacturing processes became established. The amounts contained in

coal tar and coal gas are small, and the pyridine bases isolated from them are a mixture of

many components. Thus, with a few exceptions, isolation of pure pyridine bases was

expensive. Today, almost all pyridine bases are produced by synthesis.

b) From aldehydes or ketones with ammonia

The reaction of aldehydes or ketones with ammonia is the most general synthetic

reaction for the manufacture of pyridine bases and allows the preparation of various

pyridines. This reaction was first studied in detail by CI CHICHIBABIN in 1924 and since then

been studied extensively for industrial manufacturing because of cheap access to raw

materials. The reaction is usually carried out 350-5500C and a space velocity of 500-1000 h-1 in

the presence of a solid acid catalyst (e.g., silica alumina)

Table, Synthesis of 2- and 4-methyl pyridine from acetaldehyde and ammonia


Company Catalyst Yield%

2-Methylpyridine 4-Methylpyridine

Koei Chemical Co3Al3(PO4) 45 9

Nippon Kayaku AL2O3-SiO2-CdCl2 35 44

Aldehydes react with ammonia as follows:

For example, acetaldehyde and ammonia give 2-methylpyridine (Eq.1) and 4-methylpyridine

(Eq.2).

With α,β-unsaturated aldehydes the reaction occurs according to the following schemes;

For example, acrolein and ammonia give 3-methylpridine (Eq.3), pyridine is

simultaneously formed by demethylation. Examples of this synthesis are given in table 3.


Acrolein and acetaldehyde react with ammonia mainly to form pyridine:

Acrolein and propionaldehyde react with ammonia to give primarily 3-methylpyridine

(Eq. 5)

Acetaldehyde and formaldehyde react with ammonia to give mainly pyridine (Eq.6)

they appear to form acrolein and then acrolein and formaldehyde react with ammonia to

give pyridine. Simultaneously 2, 3-, and 4-methylpyridines are formed, as shown in Equations

(1)-(4). This method is one of the most widely used for pyridine production. Table 4 lists some

examples of this process, and Figure 1 illustrates the flow sheet of the plant.

A preheated gaseous mixture of acetaldehyde, 36% formaldehyde, and ammonia is

passed through reactor (a) packed with the catalyst at 400-4500C. The reaction mixture is

separated from ammonia and hydrogen by a collector (b) and extracted with solvent, e.g.,

benzene (c), the solvent is removed from the extract (d) and pyridine and 3-methylpyridine

are isolated in continuous distillation columns (e). The catalyst is periodically regenerated by

air.

Figure: Pyridine and Methyl pyridine production from

acetaldehyde and formaldehyde with ammonia

Collector

Ex

tra

cto

r

Re

acto

r

So

lve

nt

dis

till

ati

on

Dis

till

ati

on

Dis

till

ati

on

NH3

Acetaldehyde

36% Formaldehyde

Nitrogen

Air

To

purification

High-boiling

pyridine bases

3-Methylpyridine

(4-Methylpyridine)

Pyridine

(2-Methylpyridine)Solvent

To NH3

purification


Propionaldehyde and formaldehyde react with ammonia to give 3,5-dimethylpyridine (Eq.8).

Benzaldehyde and acetaldehyde give 2-phenyl pyridine and 4-phenyl pyridine (Eq.10).

Ketones and aldehydes react with ammonia according to the following general scheme:

Typically, acetone and formaldehyde with ammonia give 2,6-dimethylpyridine.

α,β-unsaturated ketones or aldehydes react with ammonia according to the

following scheme:

For example, acrolein and acetone react with ammonia to give 2-methylpyridine:


As a variant, acetone with ammonia gives 2,4,6-trimethylpyridinewilh simultaneous

demethylation. Cyclopentanone and acrolein with ammonia give 2,3-cyclopentenopyridine.

Using aniline instead of ammonia results in formation of quinoline.

As shown above, various pyridines can be obtained by using different combinations

of aldehydes, Ketones from ammonia and amines.

c) From Acrylonitrile and Ketones

Synthesis from acrylonitrile and Ketones is one of the current processes for

manufacturing 2-methylpyridine. This process gives 2-methylpyridine selectively, in contrast to

the process using acetaldehyde ammonia, which gives 4-methylpyridine as a byproduct.

First, the reaction of acrylonitrile and acetone, catalyzed by a primary aliphatic amine such

as isopropylamine and a week acid such as benzoic acid, occurs in the liquid phase at

1800C and 2.2 MPa to give 5-oxohexanenitrile, with 91% selectivity. The conversion is 86%.

Then cyclization and dehydration of the initial product are carried out in the gas phase in the

presence of hydrogen over a palladium, nickel, or cobalt-containing catalyst at ca. 2400C to

give 2-methylpyridine in 84% yield , 4-Methyl-5-oxohexanenitrile, formed from acrylonitrile

butanone, gives 2,3-dimethyl-pyridine in 89% yield.

d) From Dinitriles

In a vapor-phase reaction over a nickel containing catalyst in the presence of

hydrogen, 2-methylglutaronitrile gives 3-methylpiperidine, which then undergoes

dehydrogenation over palladium-alumina to give 3-methlpyridine:


A one-step gas-phase reaction over a palladium-containing catalyst is reported to give 3-

methylpyridine in 50% yield.

1.6.2 Dealkylation of Alkylpyridines

Alkylpyridines of low commercial value, obtained as byproducts of pyridine base

synthesis, are occasionally converted into useful pyridine bases by dealkylation. The methods

for dealkylation involve oxidative dealkylation by air over a vanadium oxide catalyst, steam

dealkylation over a nickel catalyst and hydrodealkylation over a silver or platinum catalyst.

Examples are listed in Table.

1.6.3 Synthesis of 5-Ethyl-2-methylpyridine from paraldehyde and ammonia

Reaction of paraldehyde with aqueous ammonia in the liquid phase is carried out ay

200-3000C and 12-13 MPa in the presence of an ammonium salt (e.g., ammonium

phosphate) to give 5-ethyl-2-methylpylidine (MEP) in about 70% yield (Eq. 20). Figure 2 shows

the reaction route and Figure 3 illustrates the manufacture of MEP by the Montecatini-Edison

process.

Figure: 2 Mechanism of 5-ethyl-2-methylpyridine formation [45]


Dealkylation of Alkylpyridines

Starting material Catalyst Additives Yield of pyridine

3-Methylpyridine V/CR/Ag-Al2O3 Air, H2O 82

3-Methylpyridine Ni-SiO2 H2, H2O 93

2-Methylpyridine Ni-ZrO3 H2O 50

Alkylpyridine Ag H2 58

Paraldehyde, produced from acetaldehyde and sulfuric acid reacted with 30-40%

aqueous ammonia acetic acid at 220-2300C and 10-20 MPa. The reaction mixture is

separated into two phases in a separator (c). Ammonia is recovered from the aqueous layer

by a stripper (d). MEP, 2-methylpyridine and 4-methylpyridine are isolated from the organic

layer by distillation.

1.6.4 Synthesis from Nitriles and Acetylene

Liquid phase reaction of nitriles with acetylene is carried out at 120-1800C and 0.8-2.5

MPa in the presence of an organocobalt catalyst and gives 2-substituted pyridines:

For example, acetonitrile and acetylene react in the presence of cobaltocene as catalyst to

give 2-methylpyridine in 76% yield. Acrylonitrile and acetylene react in the presence of

cyclopentadienylcobalt-cycloocta-1,5-diene catalyst to give 2-vinylpyridine with 93%

selectivity.

1.6.5 Other synthetic methods

Ethylene ammonia reacts in the presence of a palladium complex catalyst to give 2-

methylpyridine and MEP. Pyridine can be prepared from cyclopentadiene by ammoxidation,

or from 2-pentenenitrile by cyclization and dehydrogenation. Furfuryl alcohol or furfural

reacts with ammonia in the gas phase to give pyridine. 2-methylpyridine is also prepared

from aniline.

Figure: 5-ethyl-2-methylpyridine (MEP) production by Montecatini-Edison process

Paraldehyde

productionReactor

Se

pa

rato

rF

ra c

tio

na

tin

g

co

lum

n

Str

ipp

er

De

wa

teri

ng

co

lum

n

Fra

cti

on

ati

ng

co

lum

n

Fra

cti

on

ati

ng

co

lum

n

Fra

cti

on

ati

ng

co

lum

n

NH3/H2O

Acetic acid

Acetaldehyde

Sulfuric acid

2-Methylpyridine

4-Methylpyridine

High-boiling

products

MEP

Water

Paraldehyde MEP recycling

Low-boiling

products


1.6.6 Standard specification of refined pyridine (ASTM)

Appearance Clear liquid, free of extraneous matter and

sediment

Odor pyridine, characteristic

d 15.56 0.985-0.990

Colour not darker than no.20 on platinum-cobalt

scale

Distillation at atmospheric pressure

Total distillation range < 20C

Initial distillation temp, (first drop) > 114.00C

End point (dry point) < 117.00C

Water <0.20 wt%

Water solubility clear solution, no turbidity or oil film

1.6.7 Quality specification, storage and transportation

Specifications of pyridine vary according to country but are usually > 99.8% purity by

gas chromatography analysis. Table lists the standard specification for refined pyridine

(ASTM) in the United States [54]. Pyridine bases should generally be stored under dark, cool

conditions. They are transported in drums, tank cars and bulk containers in accordance with

the following regulations:

1.6.8 Uses

Pyridine is an excellent solvent, especially for dehydrochlorination reactions and

extraction of antibiotics. Large amounts of pyridine are used as starting material for

pharmaceuticals and agrochemicals for example, herbicides such as diquat and paraquat,

insecticides such as chlorpyrifos, and fungicides such as pyrithione.

2-Methylpyridine

The major use of 2-methylpyridine is as a precusor of 2-vinylpyridine. The terpolymer of

2-vinylpyridine with butadiene and styrene is used as an adhesive for textile tire cord. 2-

Metylpyridine is also used as a material for a variety of pharmaceuticals and agrochemicals:

for example, chemicals such as nitrapyrin to prevent of ammonia from fertilizers, herbicides

such as picloram, and coccidiostats such as amprolium.

3-Methylpyridine

A considerable amount of 3-methylpyridine is used as a starting material

for pharmaaceuticals and agrochemicals: for example, insecticides such as chlorpyrifos,

feed additives such as nicotinic acid and nicotine carboxamide, and herbicides such as

fluazifop-butyl.

4-Methylpryridine

The primary use of 4-Methylpryridine is in the production of the the antituberculosis

agent isonicotinic hvdrazide. Polvmers containing 4-Methylpryridine, obtained ironi 4-

Methylpryridine used as anion exchangers.

Polyalkylpyridines

Large amounts of MEP are used as a starting material for nicotinic acid. 2,6-

dimethylpyridine is used for the antiarteriosclerotic pyridyl carbamate, while 3,5-

dimethylpyridine is used for producing the antiulcer medication omeprazole.

1.7 PHTHALIC ANHYDRIDE

1.7.1 From Naphthalene


Basis – 1 ton phthalic anhydride

Naphthalene (780) 2500lb

Air 830000 cu ft at 600F

1.7.1.2 Reaction


1.7.1.3 Manufacture

Naphthalene is melted and pumped to a vaporizer, where it is vaporized by bubbling

primary preheated air through the molten material. Additional (secondary) air is added to

tlie primary air-naphthalene vapor steam in a mixing section in the exit pipe from the

vaporizer to bring the air-naphthalene ratio to 18-22:1 b weight. This vapor mixture is then led

to a converter consisting of multiple tubes filled with supported vanadium pentoxide catalyst.

Heat (8,000 to 10,000 Btu per lb of naphthalene) is removed outside of the fixed catalyst,

either by boiling mercury under suitable pressure or by pumping molten salt across the tube

bank. In the converter the naphthalene is oxidized to phthalic anhydride, carbon dioxide,

and water (temperature, 675 to 8500F; contact time 0.1 to 0.6 sec).

Exit gases pass through a vapor cooler that reduces the gas temperature to just

above the dew point (about 2600F) and then enter the recovery system. Formerly these were

large air-cooled condensers, called “hey barns" where the crude phthalic anhydride

crystallized on the walls. Modern plants use fine tube condensers, cyclones or water

scrubbers. In any case the crude product or solution is purified by in a stainless steel vacuum

still. The purified phthalic anhydride is usually melted and flaked for storage and packaging.

Maleic anhydride, formed as a by-product, may be removed by working up the crystals in

the last compartment of the condenser box system or by scrubbing the tail gases from the

condenser boxes. Most commercial phthalic anhydride contains 0.25 to 0.40 per cent maleic

anhydride.

The vanadium pentoxide catalyst possesses a long life, acting satisfactorily for several

years of continuous operation. The amount of phthalic anhydride produced is at least 20,000

times the weight of the catalyst present before reactivation is necessitated.

A German-developed process now in use in the United States makes use of a V2O5 on

silica gel catalyst containing 20 to 30 per cent K2SO4. The process operates at a lower

temperature (650 to 7250F) and higher contact time (-1 to 5secs) than the conventional V2O5

on alumina catalyst. However, higher yields are claimed (104 lb phthalic anhydride per lb

naphthalene vs. 80lb for conventional process).

Phthalic anhydride is also produced using a fluidized catalyst (10 per cent V2O5 on an

inert support). Preheated air at 45 to 60 psi enters the base of the reactor through a

distribution plate. Molten naphthalene (1lb per 10 to 12lb air) is introduced into the reactor

and is vaporized by direct contact with the catalyst charge (7000F). The vapors become

admixed immediately with the air-catalyst mixture, owing to the severely agitated nature of

the catalyst bed. The air-naphthalene is converted to phthalic anhydride, carbon dioxide,

carbon monoxide, and water vapor. The reaction gases, after leaving the dense catalyst

phase, pass through a settling zone and into an internal cyclone system for removal of most

of the catalyst. The vapors containing a small amount of catalyst dust are cooled and then

passed through catalyst-recovery system consisting of a series of specially designed filters. It is

reported that 100 per cent recovery of catalyst with no poisoning, so that it is unnecessary to

replenish the catalyst at any time. About 25lb catalyst is required in the reactor per lb

naphthalene fed per hr. Any carbon formed is burned off the catalyst in situ. A separate

Melting

kettle

Vaporizer Rector

Cooler

Vapor

cooler

Condenser

box

Melt

tank

Flaker

Co

lum

n

Figure: Production of Phthalic anhydride from Naphthalene

Cooled

fused

salt

Naphthalene

Primary air Secondary airWaste

Phthalic

anhydride

Slak gases

Hot

fused

salt


regenerator of the type used in fluid petroleum cracking operation not required.

The product gases containing phthalic anhydride are sent to a waste heat boiler

where the gases are cooled to 3000F, still above the phthalic anhydride dew point (2650F).

Phthalic anhydride is recovered in switch condensers, i.e., product is being removed from

one condenser by melting while the on the stream.

Contact time in the reactor is 10 to 20 sec, the air-naphthalene ratio is 10:1 to 12:1 by

weight and the yield of98 per cent phthalic anhydride is 80lb per 100lb naphthalene

charged. The product is said to be purer that that obtained in the fixed bed process, but

usually higher-grade naphthalene feed is required. The potassium-modified vanadia catalyst

mentioned previously is also used in the fluid bed process. Yields with this catalyst are

claimed to be 100 lb phthalic anhydride per 100 lb naphthalene charged.

1.7.2From Orthoxylene


Basis-1 ton phthalic anhydride

Orthoxylene 1950lb

Air 744000 cu ft at 600F

1.7.2.2 Reaction

1.7.2.3 Manufacture

Orthoxylene is vaporized and mixed with preheated air. About ten times the

theoretical requirement of air is used in order to avoid operating within the explosive limits.

The mixture is then fed into the reactor, which is similar to the one described previously for the

oxidation of naphthalene. A vanadium pentoxide base catalyst is used, and the heat of

reaction is removed by circulating molten salt outside the catalyst tubes. The conversion

temperature is greater than 1,000°F, and the contact time is of the order of 0.1 to 0.15 sec.

The reaction gases, consisting of phthalic anhydride, carbon dioxide, and water, are

cooled in heat exchangers, condensed, distilled, flaked, and packaged, in a manner similar

to the purification of the naphthalene oxidation reaction product. The finished material is of

high purity, analyzing about 99.7 per cent phthalic anhydride.

A phthalic anhydride yield equivalent to that for conventional naphthalene-oxidation

plants (85 to 95 lb product per 100 lb raw material) has been claimed.

Terephthalic acid has its two carboxyl groups in the para position rather than the

ortho. Consequently the acid is stable and manufactured and sold as such. It is made by the

liquid-phase air oxidation of p-xylene. The reaction is carried out at 1300C in the presence of

an oil-soluble cobalt salt (metal content 0.002 to 0.2 per cent by weight of xylene). Solid

terephthalic acid crystals separate as they are formed and removed from the reaction mass

by filtration a side stream from the reactor. Water vapor formed in the reaction is separated

from accompanying xylene vapors and the latter are returned to the rector. The crude

terephthalic acid crystals (77 per cent pure) may be purified by solvent extraction (aqueous

Figure: Production of Phthalic anhydride from Orthoxylene

Vaporizer

Mixer

Preheater

Filter

Rector

Salt

cooler

Vapor

cooler

Condenser

box

Melt

tank

Flaker

o-Xylene

Air

Slack

gases

Waste

Co

lum

n

Phthalic

anhydride


methanol) or by esterification (methyl ester).

One large company uses nitric acid as the oxidant instead of air. Another uses a two-

stage process in which p-xylene is air oxidized to toluic acid in a first stage, then esterified to

methyl toluate and oxidized stage to monomethyl terephthalate. Further esterification yields

the dimethyl ester.

Isophthalic acid is made by a method similar to that used for terephthalic acid,

except that the raw m-xylene. The liquid phase oxidation may be carried out at 2,500 psi and

high temperature in presence of sulfur, ammonia, and ammonium salts, in which case

amides and ammonium salts are formed. Latter in the process these are hydrolyzed to the

acid.

Mixed phthalic acids are manufactured by one company by liquid-phase oxidation

of mixed xylenes. Because acid products are solids the oxidation is carried out in the

presence of a solvent. Typical process conditions are 2000C, 400 psi, 1.5 to 2 hrs reaction time,

10 to 15 per cent excess air. The catalyst is a heavy-metal salt together with some form of

bromine. When the oxidation is essentially completed, the product acids are separated from

the solvent by centrifugation. The cake is washed and dried; filtrate is distilled to remove

water and is then recycled. With 95 per cent conversion, a yield of 80% acids based on

xylene is obtained.

Paracymene may also be oxidized to a high-purity terephthalic acid, but overall cost

is higher than the p-xylene process.

1.7.3 Uses

Per cent

Phthalate plasticizers 40

Alkyl resins 38

Polyesters 13

Miscellaneous 09

100

1.8 RESORCINOL

Resorcinol C6H6O2 is a white crystalline compound with a weak odour and a

bittersweet taste. Other names are 1,3-(or meta-) benzenediol, 1,3-dihydroxybenzene or

dioxybenzene and 3-hydroxyphenol. Resorcinol does not occur in nature as such. The first

syllable of the name resorcinol is derived –from the word resin because HLASIWETZ and

BARFM obtained it by the destructive distillation of a natural resin 1864. The structure of

resorcinol is similar to that of orcinol 5-methyl-1,3-benzendiol, which accounts for the second

part of the name. Resorcinol has been produced industrially for more than 100 years.

Resorcinol is a dihydric phenol and exhibits the typical reactivity of a phenol. Its most

important reaction with formaldehyde form phenolic resins.

The hydrogen atom surrounded by the two meta-hydroxyl groups can be substituted

much more easily than the other ring hydrogens compared to catechol and hydroquinone

resorcinol has the highest reactivity toward formaldehyde.

1.8.1 Manufacture

Resorcinol is produced commercially world-wide in only a few specialized plants. All

of these plants use benzene as the main feedstock. In Japan resorcinol is produced in two

plants (Sumitomo Chemical and Mistsui Petrochemical) Via 1,3-diisopropylbenzene. The

United States (INDSPEC Chemical Corp.) and Germany (Hoechst) each product it in one

plant, using the "classical" route via 1,3-benzenedisulfonic acid.


1.8.1.1 Via sulfonation of benzene

Reaction

Manufacture

The sulfonation of benzene formerly led to the production of considerable amounts of

waste because it was carried out with mixtures of sulfuric acid and sulfur trioxide, Excess

sulfuric acid was precipitated with lime to form gypsum, which had to be disposed of in

landfills.

In the process variation used in Germany today, the sulfonation of benzene is

carried out continuously with sulfur trioxide of sulfuric acid are contained in the sulfonation

mixture and the addition of lime is not required. After neutralization with sodium sulfite, soda

ash, or sodium hydroxide solution, the sulfonation product disodium benzene-1,3-disulfonate

is mixed with excess sodium hydroxide and fed to an alkali fusion reactor at 320-3500C. The

endothermic solid-state reaction yields a white powder, consisting chiefly of disodium

resorcinate, sodium sulfite, and some excess sodium hydroxide. Depending on the method

used, the product of the fusion reaction is trated with either a small quantity of water (in this

case, solid sodium sulfite which contains organic impurities, is obtained as by-product) or a

large quantity of water forming an almost saturated solution of the product. In both

processes the dissolved dissodium resorcinate is than reacted with sulfur dioxide, sulfuric acid,

or hydrochloric acid to give resorcinol. The dissolved resorcinol is extracted with an organic

solvent. The preferred solvent diisopropyl either, but benzene, 4-methyl-2 pentanone (methyl

isobutyl ketone) or others can also be used. The solvent is then distilled off, and crude


resorcinol is purified further by distillation in vacuum. The byproducts of this process are small

amounts light ends essentially phenol, as well as cresol and 3-mercaptophenol and small

amounts of heavy ends, mostly oligohydroxy biphenylenes.

The salt solution remaining after extraction is processed further. When sulfuric acid is

used to neutralize disodium resorcinate, sulfur dioxide and sodium sulfate can be recovered

as by products from this stream.

1.8.1.2 Via hydroperoxidation of m-Diisopropylbenzene

Benzene, together with a benzee-cumene mixture recycled from the alkylation

process, is alkylated with propene in the liquid phase by using an AlCI3-HCl complex as a

catalyst. After addition of p-diisopropylbenzene (p-DiPB) and triisopropylbenzene (TriPB), the

alkylate is subjected to isomerisation/transalkylation. In this step most of p-DiPB and TriPB

converted intom-Diisopropylbenzene (m-DiPB). The reaction mixture is then separated by

distillation into three fractions (benzene-cummene, m-DiPB and p-DiPB-TriPB). The subsequent

auto oxidation of pure m-DiPB proceeds according to a radical change mechanism. It is

accomplished in casacade of aeration reactors by using compressed air in an aqueous

alkaline medium at 90-110 0C an 0.5-0.7 MPa to yield [1,3-phenylenebis(1-methylethylidene)]

bis hydroperoxide (m-Diisopropyl benzene dihydroperoxide, DHP).

After an overall residence time 6-8 hr oxidate contains ca. 20% DHP and ca.35% m-

Diisopropylbenzene monohydroperoxide (MHP). The heterogeneous oxidate is subjected to

phase separation. m-Diisopropylbenzene dihydroperoxide is then crystallized, centrifuged,

dissolved in acetone, and fed to a cleavage reactor. Higher concentration of

hydroperoxides leads to the above average formation of by-product and increased safety

hazards. The main by-product of oxidation are meta substituted acetophenones and

Sulfonation

Neutralization

Alkali fusion

Dissolution

acidification

Extraction

Solvent recovery

Product

distillation

SO2

production

Na2SO4

production

Solvent

cycle

Resorcinol

Light endsHeavy ends

Liquid SO2

Pure

Na2SO4Waste water

to Bio pond

Water vapors

H2O

H2SO4

NaOH

NaOH

SO3

Benzene

Figure: Resorcinol production via sulfonation


dimethyl phenyl carbinols. The later are converted to recyclable m-DiPB by acid catalyzed

dehydration and hydrogenation in downstream unit operations.

The cleavage of DHP to resorcinol and acetone is carried out under acid catalysis

(preferably with ca. 1% H2SO4) in boiling acetone with reaction time of 30 min. After

neutralization, acetone is distilled off at normal pressure and resorcinol under vacuum.

Further purification of resorcinol can be achieved by recrystallization or extraction. The

overall process yield is ca. 75% based on benzene. Alternatively cleavage of the oxidate can

be carried out in the presence of hydrogen peroxide. In this case the carbinols formed as

byproducts are subsequently oxidized to DHP and thus eventually also converted to

resorcinol.

1.8.2 Other processes

Koppers in the united states and Mitsui Toatsu in Japan have developed a process for

manufacturing resorcinol from 1,3-diamino benzene, which is produced by the

hydrogenation of dinitrobenzene. The dehydrogenation of 1,3- cyclohexanedione to

resorcinol, described by British Oxygen, was further developed by Hoechst in Germany to a

four stage process. The starting materials are acetone m-methylacrylate or acrylonitrile.

Niether process has been commercialized the direct hydroxylation of phenol with hydrogen

peroxide, for example, has been investigated extensively, but it yields only catechol and

hydroquinone.

Appearance White flakes, crystals or powder

Freezing point Min. 109.5 0C

Purity Min. 99.5% (wt%)

Water content Max. 0.1% (wt%) (Karl Fischer)

Phenol Max. 0.1% (area/area) (Capillary GC)

o-Cresol Max. 0.1%

m-,p- Cresols Max. 0.1%

Catechol Max. 0.1%

3 mercapto phenol Max. 0.2%

Heavy ends Max. 0.3%

1.8.3 Uses

Resorcinol is used in industry as an intermediate. Worldwide consumption is about 40

000 t/a (1990), the primary consumer (more than 50 %) is the rubber industry. In the

production of tires and other reinforced rubber products (conveyor belts, driving belts),

resorcinol-phenol-formaldehyde condensates are used to enhance adhesion between cord

and rubber (dip formulations, dry bonding agents). Furthermore rubber- mixtures contain

resorcinol to improve some properties after curing

The second largest market for resorcinol (ca. 25%) is in high-quality wood adhesives,

which are made from resorcinol, phenol, and formaldehyde. These resorcinol-phenol-

formaldehyde resins are especially suitable for the manufacture of laminated wooden

beams-which must be to some extent waterproof at ambient temperature. The first such use

was in the manufacture of wooden aircraft propellers (propeller glue).

Further uses include

A new process for producing the intermediate m-aminophenol

Production of light stabilizers for plastics

Production of sunscreen preparations for the skin

Production of dyes (fluorescein, eosin)

Manufacture special pharmaceuticals (e.g., acne preparations)

1.9 FISCHER - TROPSCH SYNTHESIS

Aliphatic hydrocarbons and oxygenated compounds can be synthesized from

mixtures of hydrogen and carbon monoxide by reaction over suitable catalysts. Since Franz

Fischer and Hans Tropsch first synthesized liquid hydrocarbons over an alkalized iron catalyst

in 1923, considerable research and process development has been done in many parts of

the world. Because the synthesis reaction is highly exothermic, many methods have been


investigated for removing heat liberated in a catalyst bed.

Usually, hydrocarbons are the principal products of the Fischer-Tropsch synthesis, with

about 5-15 per cent of the total products being oxygenated hydrocarbons. However, by use

of selected catalyst and operating conditions, the yield of oxygenated hydrocarbons can

be increased considerably. Production of oxygenated compounds (other than water and

carbon dioxide) without hydrocarbon by-product has been attained only in the

hydroformylation reaction in which an olefin is reacted with mixture of hydrogen and carbon

monoxide. In the oxo process, hydroformylation of the olefin to an aldehyde occurs by

addition of a hydrogen atom and a formyl group to the double bond. Other variations often

Fischer-Tropsch synthesis are the Synol process for the production of relatively high

concentration of alcohols and the Isosynthesis process for the production of branched-chain

hydrocarbons.

1.9.1 General synthesis scheme

A schematic diagram of a plant producing synthetic liquid fuels and chemicals from

coal via the Fischer-Tropsch synthesis is shown in Figure. Gasification of coal with steam and

oxygen is followed by a purification step to eliminate solids, sulfur compounds, and most of

carbon dioxide. Two stages of synthesis are employed to attain a high conversion of the

synthesis gas. Recovery and treatment of primary products to refined products is carried out

in several conventional steps.

1.9.2 Production of synthesis gas

Synthesis gas for the Fischer-Tropsch reaction consists of mixtures of hydrogen and

carbon monoxide in ratios of from 0.7H2: 1CO to 2.5H2: 1CO. Mixtures of hydrogen and

carbon monoxide have been made in the past by water-gas generators operated cyclically,

usually using coke as a fuel. The coke is first heated by an air blow (1) to heat the bed, and

then, during the make cycle, steam is blown through the hot coke bed (2) to produce

hydrogen and carbon monoxide:

C + O2 CO2 ΔH= -94555 cal(15000K)…………………(1) C + H2O H2 + CO ΔH= +32265 cal(15000K)…………………(2)

Reaction (2) is endothermic; when the temperature of the coke bed becomes too

Ga

sifi

ca

tio

n

Raw

synthesis

gas

Ga

s

pu

rifi

ca

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n

Re

acto

r

Wa

ter

wa

she

r

CO

2

scru

bb

er

CO2

Water

Re

acto

r

1st stage

synthesis

2nd stage

snthesis

Wa

ter

wa

she

r

Water

Tail gas

Steam

Oxygen

Coal

Sulfur recovery

Oil

scru

bb

er

Ch

em

ica

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ve

ry

Dis

till

ati

on

Po

lym

eri

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Re

form

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CO2

SulfurFuel gas

Chemicals

Liquified

petroleum gasGasoline

Diesel oil

Fuel oil

Wax

Heavy

distillate

Light

distillate

Oil condensate

Water and

chemicals

C3 & C4

Water

Figure: Flow diagram of Fischer Tropsch process

Ca

t.

cra

ckin

g


low, the make cycle is ended and air is blown to heat the bed to high temperatures again.

Water-gas generators have been widely used to make heating gas of about 300 Btu per cu

ft as well as gas for the production of hydrogen to be used in ammonia synthesis. Because of

the cyclic nature of this method, the high cost of coke in relation to coal, and the relatively

low productive capacity, water-gas generators are not sufficiently economical to be

considered for the manufacture of synthetic fuels. Other processes are available for the

continuous productions of synthesis gas from natural gas, liquefied petroleum gas, high-

boiling oils, or solid fuels. Natural gas and liquefied petroleum gas can be reformed with

steam and carbon dioxide over a nickel catalyst at high temperatures. Recently, processes

have been developed for producing synthesis gas by the partial combustion of gaseous and

liquid hydrocarbons or solid fuels with commercially pure oxygen (95-98 percent oxygen) and

steam. Coal, which costs only one-fourth as much as coke on a Btu basis, is readily

converted to synthesis gas in this manner The partial combustion can be carried out at

pressure of 400-450 psi, with the advantage that synthesis gas is produced at a pressure

preferable for synthesis, thus avoiding the expense of compressing the gas. In addition,

gasification of coal under pressure allows considerably greater throughputs in a given piece

of euipment, thereby decreasing capital costs.

Pressure gasification can be accomplished with fine coal in suspension and in

fluidized beds or with lump coal in fixed beds. Reactions (1) and (2) occur continuously, and

at the high temperature attained by the use of oxygen, reaction (3) occurs:

CO2 + C 2CO ΔH= +39460 cal(15000K)…………………(3) Heat required for reactions (2) and (3) is supplied by reaction (1). Other reactions

occur in the gasification zone, but the three shown are the principal one involved.

Where pulverized coal is gasified with oxygen and steam, the gases leave the

combustion zone at a high temperature; a typical analysis of the gas produced is shown in

the first column of Table.

Consumption Pulverized coal Fixed bed-Lurgi

H2 35 41.1

CO 50 22.4

CO2 10 24.6

H2S 1.5 0.5

N2 1.7 3.5

CH4 0.9 7.6

O2 - 0.1

Illuminates - 0.2

Table - Composition of crude synthesis gas from coal. Gasification with Steam and

Oxygen.

The second set of data in Table is an analysis of a raw gas produced by a coal-

gasification process developed by Lurgi Gesellschaft. This process employs a noncaking type

of coal in pressurized fixed bed. Fresh coal is charged to the top of the bed by a pressurized

hopper arrangement, and steam oxygen are fed to the bottom of the gasifier. Coking of the

coal occurs at top of the bed, producing by-product tar. The gases have a relatively high

content of methane, as its formation is favored in fixed bed high-pressure gasification. This

gasification process is employed in the 5,000-bbl per day synthesis plant in South Africa.

1.9.3 Purification of synthesis gas

The raw synthesis gas must be purified to remove solids such as unburned carbon and

fine ash. This is generally done by water washing the gas in packed or spray towers, cooling

as well as cleaning the gas.

Hydrogen sulfide and organic sulfur are catalyst poisons and must be removed to an

extremely low value generally less than 0.1 grain of total sulfur per 100 cu ft of gas. Carbon

dioxide is harmful to the catalyst in high concentrations, and in addition is a diluent. Up to

about 2 percent of carbon dioxide usually can be tolerated in the purified gas. Acidic

constituents of raw synthesis gas, carbon dioxide and hydrogen sulfide can be removed

either by water or rectisol scrubbing or by an alkaline wash such as monoethanolamine,


diethanolamine, or a hot potassium carbonate solution. Regeneration of these alkaline

solutions is accomplished by steam stripping of the spent solution in the regenerator column.

The main cost is that for steam required in the regeneration step, the hot-carbonated

process requiring less steam than the amine-scrubbing operation. The later process has the

advantage also in removing carbonyl sulfide, usually the only organic sulfur compound

present in the gas, when the exit temperature of gasification is relatively high, such as is the

case in gasification of pulverized coal. Because the synthesis gas is under pressures of 300-450

lb, it can also be scrubbed with water. In as water scrubbing depends upon physical solubility

of carbon dioxide and hydrogen sulfide in water rather than upon chemical reaction, several

times the rate of solvent circulation rate is require. No heating steam is required, but the main

disadvantage of water washing is that 3-5 percent of the carbon monoxide and hydrogen is

lost by solution in water. Investment costs for water washing are considerably higher than for

the alkaline-wash processes.

In connection with water washing and hot-carbonate or amine scrubbing, iron oxide

boxes are usually added in the purification train, similar to those long used for purifying coke-

oven gas. Iron oxide impregnated on wood shavings effectively reduces the concentration

of hydrogen sulfide to trace amounts acceptable for Fischer-Tropsch synthesis. Iron oxide is

converted to sulfide, which is then oxidized by small amounts of oxygen in the gas; free sulfur

is formed, When organic sulfur is not removed with the carbon dioxide and hydrogen sulfide,

it must be eliminated by hot alkalized iron oxide, as was done in the German synthesis plants,

or-probably more adavantageously by adsorption on activated carbon, Nickel, cobalt, and

iron catalysts are commonly used for the Fischer-Tropsch synthesis. Nickel catalyst has been

prepared by precipitation from a nitrate solution with potassium carbonate in the presence

of thoria and kieselguhr in the proportions 100Ni:18ThO2:100 kieselgulir. It is not desirable to

employ nickel catalysts at low temperatures and elevated pressures because the formation

of nickel carbonyl is excessive. In the temperature range of 170-2200C at low pressures, both

liquid and gaseous products are obtained. As the temperature is increased to 300-3500C and

the pressure increased to 300-400 psi, Nickel catalysts produce only methane. Thus, these

catalysts can be used for making a gas from coal comparable in heating value to natural

gas. Cobalt catalysts are preferable to nickel when greater yields of liquid products are

desired. The standard German cobalt catalyst during World War II had a composition of

100Co:5ThO2:8MgO:200 kieselguhr. Insoluble metal carbonates or hydroxides were

precipitated by addition of sodium carbonate to the solution of nitrate. Kieselguhr was then

added, the slurry filtered, and the cake formed into granules of 1-3 mm in diameter. The

dried granules were reduced with a mixture of 75 percent hydrogen and 25 percent nitrogen

(ammonia synthesis gas for convenience) at about 4000C for about 50 min at a space

velocity (volumes of gas/hr/volume of catalyst) of 10,000. The catalyst was used at

atmospheric pressure at 7-10atm and at 180-2000C. Because of the expense and scarcity of

cobalt, emphasis has shifted to the use of iron. Iron catalysts may prepared for commercial

applications by precipitation from solution, from magnetite (Fe3O4) ore, or magnetite

obtained by fusion of iron oxides, or by oxidation of metallic iron with steam.

1.9.4 Commercial operation

In1939 there were 14 commercial Fischer-Tropsch plants operating throughout the

world. Nine of these were in Germany, one in France, and the others in Japan. About three-

fourths of the total annual output of about a million tons of synthetic fuels came from

Germany. most of the German plants were destroyed during World War II, and operation has

been resumed at only two plants in West Germany, These are Chemische Werke Bergkamen

A.G. at Essen a 50,000-ton-per year plant, and Krupp Kohlechomie G.m.b.H. at Wanne-Eickel.

Since the economics of producing liquid fuels are unfavorable, principally waxes and high-

boiling aliphatic alcohols are produced, the latter for use in detergents and fatty acids. A

third Fischer-Tropsch plant in operation is that of Courrieres-Kuhlmann at Harnes, France; its

capacity is about 20,000 tons a year. Other plants probably are operating in soviet-

controlled lands. Plants have recently been constructed at Brownsville, Tex., and Sasol, South

Africa, that have incorporated the newest operating techniques.

1.9.5 Brownsville plant

The first American synthetic-fuels plant was constructed at Brownsville, Tex., by the


Carthage Hydrocol Company in 1951. Reactor design was based on a fixed fluidized bed of

iron catalyst to convert carbons and chemicals. The rated capacity of the plant is 7,000bbl of

products per day but this production was never reached because of operating difficulties.

A simplified flow sheet of the original plant is shown in Fig. About 64 million cu ft per

day of natural gas is required, including that used as fuel for processing the products. An

oxygen plant supplies about 1800 tons per day to the gas generator where the partial

combustion of natural gas occurs at a pressures of about 400-450 psi in accordance with the

following equations:

CH4 + 0.61O2 0.96CO + 1.82H2 + 0.04 CO2 + 0.18H2O ΔH= -21.7

Approximately 180 million cu ft per clay of synthesis gas is produced; high pressure

steam is generated by heat recovery from the hot synthesis gas. This steam is utilized in the

oxygen plant. Carbon dioxide is scrubbed from the synthesis gas at elevated pressure.

Purified synthesis gas and recycled end gas flow to the two synthesis reactors. These vessels

have a maximum diameter of 17ft, are approximately 80ft high, and contain about 200 tons

of catalyst. Bayonet tubes carrying cooling water are located in the catalyst bed, and the

heat evolved in the synthesis is used to generate Steam. Gas and products leave the top of

the reactors, and any fine catalyst entrained in the gases is removed by cyclones, filters, or

other devices. Condensable oxygenates and hydrocarbons are removed by cooling and

water scrubbing. Lighter hydrocarbons are removed in an absorption-recovery system, and

C3 and C4 olefins are polymerized catalytically to gasoline. The primary gasoline is treated by

conventional refinery techniques, including a bauxite treatment to decompose oil-soluble

oxygenates. The distribution of liquid products from this plant was expected to be about 25%

oxygenated compounds and 75% hydrocarbons. Of the hydrocarbon liquids, about 85% is

gasoline, 10% distillate fuel, and 5% heavier fuel oil. The finished gasoline is highly olefinic, with

a research octane number of about 85 unleaded. The schedule annual production of water-

soluble chemicals is shown in table.

Scheduled annual production of oxygenated compounds from Hydrocol plants (Millions of

Pounds per year)

Methanol 0.5 Acetone 17.9

Ethanol 61.2 Methyl ethyl ketone 3.6

Isopropanol 1.3 Acetic acid 25.2

n-Propanol 19.6 Higher ketones 2.0

Acetaldehyde 11.2 Higher acids 11.0

Higher aldehydes 4.4 Higher hydrocarbons 8.5

Recovery and sale of these oxygenated chemicals would yield an appreciable part

of the plant revenue.

1.9.6 Sasol plant

A commercial Fischer-Tropsch plant using coal as raw material was put a stream late

in 1955 at Sasolburg in South Africa. Large quantities of coal are located in the area, the cost

of the mined coaI being about $1.00 per ton. This coal is the weakly caking type and

contains about 25% ash 10% water, its heating value is 9000 Btu per lb.

The daily capacity of the plant is about 5,000 bbl of total liquid products. Coal consumption

is 5,000 tons per day, of which 1,800 tons is for the power plant and 3,200 tons for gasification.

A block diagram the synthesis plant is shown in Fig.

Raw coal is crushed and classified into three sizes. The finest portion is used in the

power plant, which has four boilers, each having a capacity of 160 tons of steam per hour. A

total of about 7 million cu ft per hr of raw gas is supplied at 25atm from nine Lurgi fixed-bed

gasifiers. A Linde air liquefaction plant supplies about 70 tons per hr of oxygen for the

gasification. Carbon dioxide and sulfur compounds are removed in a Restisol plant

The purified gas at elevated pressure is divided into two streams: one flows to the so-

called Arge synthesis sections, which consists of the modernized Ruhrchemie-Lurgi fixed-bed

tubular reactors, and flows to Kellogg fluid-bed units, which also use gas obtained from

reforming the C1 and C2 hydrocarbons produced in the Arge section. There are five fixed-

bed reactors, each with a heat exchanger, cooler and recycle blower. The reactors are

almost 10 ft in diameter and approximately 40ft in height.


Refinery products Planned Production

Gasoline, bbl/day 4,300

Diesel oil, bbl/day 335

Fuel oil, bbl/day 180

Paraffin waxes, 105-240F imp, ton/year 18,000

Liquefied petroleum gas, imp. gal/day 720

Pitch and tar road primers, imp, gal/day 2,685

Chemical products

Ethanol, imp. gal/year 4,000,000

Propanol, imp, gal/year 2,000,000

Butanol, imp, gal/year 525,000

Acetone, imp, gal/year 210,000

Methyl ethyl ketone, imp, gal/ycar 260,000

Mixed solvents, imp. gal/year 60,000

Benzene, imp. gal/year 500,000

Toluene, imp. gal/year 280,000

Xylene and olvent naphtha, imp. gal/year 500,000

Creosote and preservative, imp, gal/year 1,000,000

Crude phenols, ton/year 6,000

Ammonium sulfate, ton/year 35,000

Synthesis is conducted at about 2200C and about 25 atm. Each rector is supplied with

about 700000 cu ft per hr of synthesis gas, and about 50-60% conversion is achieved. The gas-

recycle ratio is 3 vol. of end of gas per volume of fresh gas. Precipitated iron catalysts are

used in this section. Each synthesis section has its own product-treating units, much of the

product of the Argo units is high-boiling hydrocarbons, while the product from the fluidized

reactors is chiefly gasoline. The production of refinery and chemical products is listed in

Table. The pour point of -50C, a flame point of 820C and acetane number of 90.

1.10 1,4-BUTANEDIOL

1,4-ButanedioI, tetramethylene glycol, 1,4-butyIene glycol, is produced by the

hydrogenation of butynediol. It is miscible in water, ethanol, and acetone, and soluble to the

extent of 3.1 g/100 g in ethyl ether, 0.3/100 g in benzene, and 01 g/100 g in hexane.

The chemistry of butanediol is determined by the two primary hydroxyls. Esterification

is normal. For transesterification a nonacidic catalyst is used since strongly acidic catalysts

promote cyclic dehydration. With excess phosgene, bischloroformethyl ether is obtained with

formaldehyde and hydrogen chloride. The bischloromethyl ether is obtained with

formaldehyde and hydrogen chloride. The formation polyurethanes is a commercial

important reaction. Carbon monoxide and a nickel carbonyl catalyst good yields of adipic

acid. Heating with acidic catalysts cyclizes butanediol to tetrahydrofuran.

The three main butynediol producers use most of their production for butanediol.

Additional small quantities are also produced by other processes. The principal producers

are BASF, GAF, and Chemische Werke-Huels.

1.10.1 Manufacture

Refer manufacture of THF Unit: 4 (Industrial solvent)

1.10.2 Uses

Substantial amounts of butanediol are used in the manufacture of tetrahydrofuran,

butyrolactone and polyurethanes. It is increasingly being used in the manufacture of

polybutylene terephlhalate and PBT.

1.11 ACETYLENE

Acetylene manufacture by following processes

1. From calcium carbide

2. From paraffin hydrocarbons by pyrolysis (Wulff process)

3. From natural gas by partial oxidation (Sachasse process)


Nowadays acetylene is mainly manufactured by the partial oxidation of natural gas

(methane) or side product in ethylene stream from cracking of hydrocarbons. Acetylene,

ethylene mixture is explosive and poison Zigler Natta catalyst. There so acetylene is

selectively hydrogenated into ethylene, usually using Pd-Ag catalysts.

Acetylene was the main source of organic chemicals in the chemical industry until

1950. It was first prepared by the hydrolysis of calcium carbide, a reaction discovered by

Friedrich Wöhler in 1862.

CaC2 + 2H2O Ca(OH)2 + C2H2

Calcium carbide production requires extremely high temperatures, ~20000C,

necessitating the use of an electric arc furnace.

Also hydrocarbon cracking is carried out in an electric arc furnace. In which electric

arc provides energy at very high flux density so that reaction time can be kept at a minimum.

There so the design of the electro-thermal furnace is one of the important factors.

In one design (Huels process) gaseous feedstock enters the furnace tangentially

through a turbulence chamber, then passes with a rotary motion through pipe in which the

arc is passed between a bell shaped cathode and anode pipe. The rotary motion of the gas

causes the arc to rotate and thus reducing fouling. The arc is operated at 8000kw D.C. at

7000volts and 1150amp cathodes are said to last 800hours while anodes only 150hours.

In other design, fresh hydrocarbon and recycle gas are fed to the arc. The effluent

reaction gases are quenched and purified. 35%w purified acetylene along with 17%w

ethylene and 10%w carbon black, H2 and other products in minor amount is obtained in one

pass through furnace.

The difference is that the arc is rotated by means of an external magnetic coil, and

quenching is carried by propane and water in 1st and 2nd step respectively. Some propane

cracking improves the yield of acetylene. The propane quench cools the arc gases to

10950C in 0.0001 to 0.0004 sec while the water quench cools the mixture to 3000C in 0.001 to

0.003 sec. Power consumption is 12.36kwhr/kg of pure acetylene. 21-22%v acetylene is

obtained in the product gases.

1.11.1 Manufacture from natural gas by partial oxidation (Sachasse process)


Basis: 1000kg acetylene (99.5%) plus 340000 Cu ft. off gas (345 Btu/Cu ft.)

Natural gas = 190000 Sef

Oxygen (95%) = 5400kg

Solvent = 2.3kg

Carbon black = 22.7kg

Acetylene = 4.53kg

Power = 15000kWH

Steam = 4535.9kg

Water (cooling) = 22710 liter

1.11.1.2 Reaction

CH4 + 2O2 CO2 + 2H2O

2CH4 C2H2 + 3H2 ΔH = + 79.8 kcals

1.11.1.3 Manufacture

Acetylene may be produced from a variety of hydrocarbon feed stocks (natural gas,

LPG, naphtha, fuel oil, even crude oil) by high-temperature cracking. Heat for the cracking

operation is developed by partial oxidation of the feed stock with oxygen. The heat evolved

cracks the excess hydrocarbon to acetylene. After rapid quenching with water, the

acetylene is separated from the gas stream by absorption-desorption in a suitable solvent.

The process is known as Sachasse process using natural gas as raw material.

Natural gas (1mole) and low purity oxygen (0.65moles 95%O2) are preheated

separately to 5100C and fed to a specially designed burner.


The converter is vertical cylindrical unit built in three sections

Mixing chamber

Flame room

Quench chamber

After rapid and through mixing of oxygen and methane in the mixing chamber, the

gases are fed to the flame room through the portal in a burner block designed to prevent

back travel or blow-off. The heat of combustion heats the gases to 15500C to allow cracking

of the excess methane to acetylene. The residence time is 0.001 to 0.01 seconds. The

decomposition of acetylene is prevented by rapid quenching of the resulting gases with

water to 380C. The cooled effluent gases on the dry basis contain 8% acetylene, 54% H2, 26%

CO, 5% CH4, 4% CO2 and 3% N2 and higher acetylenes. These gases are run to a filter where

using carbon black, acetylene of 99.5% or higher purity is produced (23.5kg/1000kg of

acetylene is separated and purified in a manner as described for the Wulff process).

1.11.1.4 Properties

Molecular formula : C2H2

Molecular weight : 26.04 gm/mole

Appearance : Colourless gas

Odour : Odourless gas

Boiling point : -840C (sublimation point)

Melting point : -80.80C @1.27atm

Density : 1.097 kg/m3

Solubility : Soluble in acetone and DMF

It is transported under high pressure in acetone soaked on porous material packed in

steel cylinders

It is lighter than air

It is somewhat poisonous in nature

It burns with luminous flame and forms explosive mixture with air

1.11.1.4 Uses

In the chemical manufacture of acrylonitrile, vinyl chloride, vinyl acetate, acrylates

etc.

In manufacture of acetaldehyde, trichloroethylene, acetic acid, polyvinyl alcohol,

perchloroethylene etc.

In manufacture of propagryl alcohol, butyrolactone, vinyl pyrrolidine etc.

In metallurgy industries for welding and cutting

Rec

tify

ing

Co

lum

n

Oxygen

Natural Gas

Water

Recycle Water

Water

Soot Filter

Soot

Off Gas

Acetylene

PolymerSolvent

Cooler

Str

ipp

er

Filter

Figure: Manufacturing of Acetylene from Natural Gas

Re

ac

tor

Preheater

Preheater

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