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Chemicals and materials from coal in the 21st century

H.H. Schobert, C. Song*

The Energy Institute and Department of Energy & Geo-Environmental Engineering, The Pennsylvania State University,

209 Academic Projects Building, University Park, PA 16802, USA

Dedicated in honor of the late Professor Frank Derbyshire who passed away on 16 August 1999

Received 29 February 2000; revised 11 November 2000

Abstract

Coal may become more important both as an energy source and as the source of organic chemical feedstock in the 21st century. Thedemonstrated coal reserves in the world are enough for consumption for over 215 years at the 1998 level, while the known oil reserves are

only about 39 times of the world's consumption level in 1998 and the known natural gas reserves are about 63 times of the world's

consumption level in 1998. Coal has several positive attributes when considered as a feedstock for aromatic chemicals, specialty chemicals,

and carbon-based materials. Substantial progress in advanced polymer materials, incorporating aromatic and polyaromatic units in their main

chains, has created new opportunities for developing value-added or specialty organic chemicals from coal and tars from coal carbonization

for coke making. The decline of the coal tar industry diminishes traditional sources of these chemicals. The new coal chemistry for chemicals

and materials from coal may involve direct and indirect coal conversion strategies as well as the co-production approach. Needs for

environmental-protection applications have also expanded market demand for carbon materials. Current status and future directions are

discussed in this review. q 2001 Elsevier Science Ltd. All rights reserved.

Keywords: Chemicals; Materials; Coal

1. Introduction

Coal has played a key role as a primary source of organic

chemical feedstocks in the world till the 1950s, and main-

tained its large share as a primary energy source in the 20th

century. Table 1 shows the worldwide use of coal and other

energy sources, world population and per capita energy

consumption in the 20th century, estimated based on

published data [13]. Although the percentage contribution

of coal decreased from 55% in 1900 to 22% in 1997, the

amount of coal consumption in 1997 has increased to 424%,

and the per capita energy use has risen to 319% of the

world's 1900 levels, as can be seen from Table 1.Coal, as well as the other fossil fuels petroleum,

natural gas, bitumens, and oil shales are hydrocarbon

resources. In the past several decades, the dominant use of

coal has been combustion in power plants to generate elec-

tricity. In principle, there are many potential ways of using

valuable hydrocarbons. Combustion, of course, is one

choice; but other utilization strategies, the so-called non-

fuel uses, also deserve attention. Adams, for example,

argues that oil and coal used as fuel have allowed us to

work wonders, but they are too valuable as complex hydro-

carbons that can be converted into all sorts of forms (such as

plastics) to be so rapidly burned in automobiles, power

plants, and furnaces [4].

The known worldwide reserves of petroleum (1033.2

billion barrels in 1999) [5] would be consumed in about

39 years, based on the current annual consumption of petro-

leum (26.88 billion barrels in 1998). On the same basis, the

known natural gas reserves in the world (5141.6 trillion

cubic feet in 1999) would last for 63 years at the current

annual consumption level (82.19 trillion cubic feet in 1998)

[5]. While new exploration and production technologies willexpand the oil and gas resources, two experts in the oil

industry, Campbell and Laherrere, have indicated that

global production of conventional oil will begin to decline

sooner than most people think and they have warned the

world about the end of cheap oil in early next century [6].

Table 2 shows the recoverable coal reserves in the world

in 1999 and the annual consumption of coal in the world in

1998 in million short tons [5,7]. The worldwide coal

production and consumption in 1998 were 5042.7 and

5013.5 million short tons, respectively [7]. The known

world recoverable coal reserves in 1999 are 1087.19 billion

Fuel 81 (2002) 1532

0016-2361/02/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved.

PII: S0016-2361(00) 00203-9

www.fuelrst.com

* Corresponding author. Tel.: 11-814-863-4466; fax: 11-814-865-3248.

E-mail address: [email protected] (C. Song).

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application of a resource, as with coal shown in Fig. 2, it is

easy to lose sight of the fact that other alternatives even

exist. Fig. 3 shows the changes in coal consumption for

coke production and for industrial, residential and transpor-

tation uses in the US during 19491999 [7,10].

Coal has several positive attributes when considered as a

feedstock for aromatic chemicals, specialty chemicals, and

carbon-based materials [11,12]. The non-fuel uses of coalsinclude: (1) high-temperature carbonization of bituminous

and subbituminous coals to make metallurgical coke

(Table 3, Figs. 36); (2) use of coal in manufacturing

carbon materials such as activated carbons (AC), carbon

molecular sieves (CMS), and carbon for production of

chemicals such as phosphorus (phosphoric acid); (3) the

use of coal to make specialty carbon materials such as

graphite, fullerene and diamond; (4) pyrolysis of coals to

make aromatic chemical feedstocks along with other

products; (5) gasication of coal to make synthesis gasesand other chemicals; (6) the use of coal tars from carboniza-

tion, gasication and pyrolysis for making aromatic and

H.H. Schobert, C. Song / Fuel 81 (2002) 15 32 17

2005199519851975196519551945

0

200

400

600

800

1000

1200

Bituminous

Subbituminous

Lignite

Anthracite

Tota l Prod

Year

Production(MillionShortTon)

Fig. 1. Production of coal by type in the US during 19491999 (1 short ton 0.907 metric tonne).

2005199519851975196519551945

0

200

400

600

800

1000

1200

Coke Plants

Industry

Residential & Commercial

Electric Utilities

Transportation

Total Consum

Year

Consumption(Millio

nShortTon)

Fig. 2. Consumption of coal by end-use sectors in the US during 19491999 (1 short ton 0.907 metric tonne).

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phenolic chemicals; (7) the use of coal tar pitch for making

binder pitch, mesocarbon microbeads, carbon bers, and

activated carbon bers; (8) the use of coal for making

humic materials such as humic acids and calcium humates

which can be used as soil modiers and fertilizers; (9) the

use of coal for making composite materials such as coal/

polymer composites and coal/conducting polymer compo-

sites; and (10) other non-fuel uses of coal and coal-derived

byproducts (carbon in ash, materials from coal ash, etc.).Evaluation of the potential for coal in future chemical

production, as well as energy generation, presents a good

news/bad news story. The good news is that the immense

reserve base of coal implies that it can be a signicant

contributor to the world's energy, and chemical, markets

for decades, and likely centuries. The aromatic molecular

structures present in coals could be ideal feedstocks for the

aromatic polymers and engineering plastics (described

below) that have burgeoning applications and markets.

The bad news is that the traditional source of coal chemi-

cals, liquids from by-product coke ovens, is steadily

decreasing. So, as opportunities increase for applications

and markets for coal chemicals, the traditional source of

those chemicals is in steep, and likely irreversible, decline.

Coal has several advantages as a feedstock for aromaticspecialty chemicals and carbon materials. In most coals the

major fraction of carbon is in aromatic structures, which are

dominated by polycyclic as well as monocyclic aromatic

ring systems. van Krevelen [13] has discussed the aromatic

nature and macromolecular nature of coal. This structural

feature is no longer speculated, but has been established by

solid-state 13C NMR [1416], and by ash pyrolysis-GC-

MS coupled with CPMAS 13C NMR [17,18]. Some struc-

tural details of the aliphatic linkages between the aromatic

rings and the ring structures in coal have been claried by a

new chemical probe reaction, RICO (ruthenium ion-cata-

lyzed oxidation), rst reported by Stock and coworkers for

US coals [1923], and by Nomura and coworkers forChinese and Japanese coals [2426].

Thus coal may be better for aromatic chemicals produc-

tion than alternative feedstocks in which much of the carbon

is aliphatic, and especially because naphthalene derivatives

are likely to be important monomers for the coming genera-

tion of new polymer materials. Since carbon dominates the

composition of coals, one could say that coals are already

carbon-based materials. Appropriate processing conditions

could make conversion to active carbons, graphites, or other

carbon materials straightforward. Therefore, the non-fuel

uses of fossil fuels particularly coal may also become

H.H. Schobert, C. Song / Fuel 81 (2002) 15 3218

2005199519851975196519551945

0

20

40

60

80

100

120

140

Coke Pl a nt s

I n d u s t r y

Re s i d e n t i a l & C om me rc i a l

Transportation

Year

Consumption(MillionShortTon)

Fig. 3. Changes in coal consumption for coke production and for industrial, residential and transportation uses in the US during 19491999 (1 short

ton 0.907 metric tonne).

Table 3

Production of coke in the world during 1985 1999 in million metric tonnes

(1 metric tonne 1.102 short tons) (data for 1999 are estimated values)

Country 1985 1988 1992 1995 1997 1999

World total 363 372.2 332.9 369.0 360.3 324.4

Asiaa 133.3 148.1 203.5 202.9 182.5

China 48 61 79.8 135.0 139.0 121.1

Japan 52 50.7 44.5 42.6 37.7 35.5

North Americaa 35.9 27.1 27.2 25.9 23.5

US 26 29.4 21.2 21.5 20.1 18.1

FSUa 84 81.9 60.5 47.7 44.4 40.5

Russia NA NA 30.4 27.7 25.6 22.5

Ukraine NA NA 26.7 18.2 16.4 16.3

a Data for 19881999 reported by International Iron and Steel Institute,

Brussels, in Cokemaking International (1995, 1997, 1999, 2000).

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more important in the future, particularly in coal-producing

countries such as US and China.

3. Strategies for chemicals and materials from coal

Four broad strategies allow for making chemicals from

coals. The rst is gasication, followed by a sequence of C1chemistry. This is unquestionably feasible, and is the most

likely route to synthetic liquid fuels and commodity chemi-

cals from coal for the near-term future. A successful exam-

ple of this approach is the commercialization of the Eastman

process [27]. The catalytic chemistry and technologies have

been discussed at some length in a recent review [28]. At

SASOL plants in South Africa, coal is gasied to produce

synthesis gas (a COH2 mixture) with a Lurgi gasier,

which is then converted to parafnic liquid fuels and chemi-

cal feedstocks by Fischer Tropsch synthesis (FTS) over

iron-based catalysts. The SASOL process has been operat-ing successfully for several decades on a commercial scale

[29,30]. The status of various FTS processes and historical

developments have been described in open literature [31].

However, in terms of coal-derived chemicals, the gasica-

tion approach destroys completely any molecular structural

features of the coal. The chemical composition of synthesis

gas from coal and that from natural gas can be identical with

the same H2/CO ratio. Despite its technical and economic

attractiveness, it is not the route to take for chemicals that

derive directly from the coal structure.

The second strategy is conversion of coals to liquids or

tars followed by conversion of components in the liquids to

higher value products. Carbonization, pyrolysis, extraction,

or liquefaction could produce the tars or liquids. Then, an

appropriate sequence of separation or conversion operations

would yield products of interest. This second strategy has

been the basis of the coal tar industry. Like the rst strategy,it works. But, much of the coal is simply thrown away (at

least from the standpoint of chemicals production) as char or

coke. Certain coal gasication processes, such as the Lurgi

process used by SASOL of South Africa, also produce

byproduct coal tar. Such tars are expected to be different

in composition from those generated from metallurgical

coke oven, due to differences in feed coals and conditions,

particularly the carbonization temperature.

Direct liquefaction, or some variant of it, is a possible

approach. Phenol, naphthalene, phenanthrene, pyrene,

biphenyl, BTX (benzene, toluene, xylene) and their deriva-

tives are present in relatively high concentrations in various

products [32,33]. Many of the aromatic and polarcompounds in coal-derived liquids can be converted into

valuable chemicals. For example, phenolic compounds

could be obtained from naphtha distillates of liquefaction

products by aqueous extraction [33,34].

A signicant problem facing the use of such liquids, as a

source of chemicals is that, like coal tar, they contain

hundreds of components. Separation can be time-consuming

and expensive. A concept that may eliminate some time and

cost combines liquefaction with catalytic dealkylation to

produce aromatic monomers [35,36]. Dealkylation or dehy-

drogenation can simplify the composition, leading to simple


200019961992198819841984

0

20

40

60

80

100

120

140

China, Total Prod

Japan, Total Prod

U.S., Total Pro d

Year

CokeProd(MillionMetricTons

)

Fig. 4. Coke production in selected countries during 19851999 in million metric tonnes (1 metric tonne 1.102 short ton).

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200019961992198819841984

0

20

40

60

80

100

120

140

China , Total Prod

Ma c h i n e r y Ov e n

Primitive Oven

Year

CokeProd(MillionMetricTon

)

Fig. 5. Coke production in China during 19851999 in million metric tonnes (1 metric tonne 1.102 short ton).

2005199519851975196519551945

0

20

40

60

80

100

Co a l Co n s u m p a t Co k e Pl a n t s

Co k e P r o d u c e d

Year

Consumor

Prod(MillionShortTon)

Fig. 6. US coal consumption at coke plants and metallurgical coke production during 19451999 (1 short ton 0.907 metric tonne).

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separation of individual components by distillation. Dehy-

drogenation of naphtha and light oil from coal-derived

liquids is an effective route to naphthalene and methyl-

naphthalene [37]. Non-catalytic hydrodealkylation of

middle distillates from liquefaction produces unsubstituted

and methyl substituted one- to three-ring aromatics:

benzene, toluene, indene, naphthalene, methylnaphthalene,

biphenyl, acenaphthylene, uorene, and phenanthrene

[38,39]. Catalytic cracking of middle distillates gives oils

that consist mainly of alkylnaphthalenes; hydrodealkylation

then yields high-purity naphthalene and methylnaphthalene.

Pyrolytic methods can also be used in combination with

swelling and/or oxidation [40,41].

The third strategy is direct conversion of coals to chemi-

cals or materials. A reaction would be carried out to cleave

only a set of bonds selected in advance and to carefully

remove the structural fragments of interest. This highly

selective removal of certain structures could lead to valu-

able monomers or to precursors of these monomers. This

approach is an endeavor to apply the concept of conductingan organic synthesis to the chemical reactions of coals. In

doing an organic synthesis one selects a starting material for

which the structure, and, usually, the stereo-chemistry, are

known, applies a reagent for which the mechanism of reac-

tion is known; and chooses reagent and reaction conditions

to provide the desired product as the only material formed in

high yield. This is a bold and daring approach to coal chem-

istry. Not so many years ago it would have been regarded as

hopeless. However, the continuing probing of coal structure

with a wide array of instrumental techniques coupled with

specic probe reactions such as RICO [19,23,25,26], and

the recent emergence of powerful computer-based structuralmodeling applied to coals provides a signicant base of

knowledge [37,42]. Reasons for giving credence to some

of the newer computer-based models include the fact that

they are energy-minimized and the noteworthy observation

that in many cases they predict rather accurately the physi-

cal properties, such as helium density. Modeling is also in

progress on macerals or lithotypes of coals.

The analytical characterization of coal by combining

RICO and instrumental analysis can now be used to quanti-

tatively determine the amount and length of aliphatic

connecting linkages between aromatic structures, and the

amount and type of polycyclic ring systems in coal

[19,23,25,26]. Computational reaction pathway analysisand experimental tests have shown that certain aromatic

aliphatic CC bonds are selectively cleaved over specic

catalysts, and such bonds are typically stronger bonds than

those that would cleave preferentially in non-catalytic

thermal reactions [4345]. Combination of such information

offers a new direction of site-specic cleavages by tailoring

the reagents including catalysts and reaction conditions.

One of the rst successful applications of the computer-

based structural modeling approach to the reaction chemis-

try of coal was in following the processes of char formation

during the devolatilization process in pulverized coal

combustion [46,47]. There are no drawbacks that would

hinder the extension of this pioneering study to the related

area of chemical synthesis. Recent work has shown some

possible applications of hydroboration chemistry long

the province of the synthetic organic chemist to reactions

of coals at very mild conditions [48]. Valid structural

models will allow moving toward the rational planning of

direct routes from coals to chemicals.

The fourth strategy is co-production of chemicals or

materials and fuels along with electricity, which was

discussed in a recent conference [49]. The essence of this

strategy is to tie the chemicals/materials into existing or

emerging high-volume applications that have large markets

such as power industries and fuel industries. Depending on

how co-production is done, this approach may be based on

gasication and co-production, in which case it is related to

the above-mentioned rst or second strategies. An example

of approaches with this strategy is the pioneer plant concept

proposed by Neather and coworkers [50], which is based on

gasication and IGCC. Alternatively, coal pyrolysis couldbe employed as the rst step where the coal tar from pyro-

lysis is used to make aromatic chemicals as in the above-

mentioned second strategy, while the char is either burned

for electricity generation or gasied to produce synthesis

gas.

A related approach in this category is the US DOE's

Vision 21 EnergyPlex concept [51]. In Vision 21 plant,

co-production of chemicals or materials is considered by

the US DOE, although the specic routes for producing

chemicals or materials are not specied. One route indicated

is gasication followed by subsequent synthesis of fuels and

chemicals using synthesis gas [51].

4. Chemicals from coal

4.1. Aromatic chemicals from coal

Coal tars remain an important source of aromatic chemi-

cals, even though the chemical industry is nowadays domi-

nated by petroleum. At present, coal tar accounts for about

1015% of the benzene, toluene, and xylene (BTX) produc-

tion and about 95% of the larger aromatics [5255]. Brief

overviews have been published on coal tar chemical proces-

sing [56 58], and historical developments [59]. The world-wide production data in Table 3 clearly show that coal

utilization for coke making has decreased signicantly

worldwide [6063], and it is projected to decline further

[64].

Despite the earlier success of coal tar as a source of feed-

stocks for the organic chemical industry, and despite a

growing demand for aromatic chemicals for high-value-

added products, the future of the coal tar industry seems

dim. The coke industry, at least in the US, may return to a

similar version of an earlier technology, a variant of the

beehive oven. Much of the heat for these ovens is generated


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by burning the volatiles the oven works by burning the

very materials one would want to save (from the perspective

of the organic chemical business). Furthermore, coke

demand is decreasing, due to improvements in furnace tech-

nology that reduce the coke burden and to a steady shift to

electric furnace use.

Phenol, naphthalene, phenanthrene, pyrene, biphenyl,

BTX (benzene, toluene, xylene) and their derivatives are

present in relatively high concentrations in various liquid

fractions [32,65]. Many of the one- to four-ring aromatic

and polar compounds in coal-derived liquids can be

converted into valuable chemicals. For example, phenol,

one of the top 20 organic chemicals, is currently produced

in a multi-step process involving benzene isopropylation,

oxidation of isopropylbenzene, and separation of phenol.

Phenol can be used for making phenolic resins or converted

to monomers for aromatic polymers and engineering plas-

tics, such as bisphenol A and 2,6-xylenol. Phenolic

compounds (mainly phenol and cresols) can be obtained

from naphtha distillates of liquefaction products bysurfactant-mediated [66] or methanol-mediated [34]

aqueous extraction. Separation of the phenolics can, not

only produce useful chemicals, but also can eliminate the

need for down-stream hydrodeoxygenation, which consumes

costly hydrogen to produce useless water byproduct.

Of course, a signicant problem facing the potential use

of coal liquids as a source of valuable chemicals is that they

contain hundreds of components. Separation of coal liquids

into individual compounds can be time consuming and

expensive. An emerging concept that may eliminate some

of this time and cost is that of combining short-contact-time

liquefaction with catalytic dealkylation to produce aromatichydrocarbon monomers [35,36]. Dealkylation or dehydro-

genation can signicantly simplify the composition, leading

to simple separation of individual components by distilla-

tion. Aromatics can be made via catalytic dehydrogenation

and dealkylation of liquefaction products. Dehydrogenation

of heavy naphtha and light oil from coal-derived liquids is

effective for producing naphthalene and methylnaphthalene,

respectively [37]. The dehydrogenation of light distillate

fraction from catalytic hydroprocessing of coal-derived

liquids can simplify the composition because many compo-

nents at low concentrations can become one compound of

higher concentration. For example, 2-methyl-1,2,3,4-tetra-

hydronaphthalene, 6-methyl-1,2,3,4-tetrahydronaphthalene,cis-2-methyl-decahydronaphthalene, and trans-2-methyl-

decahydro-naphthalene can all be converted to 2-methyl-

naphthalene. Non-catalytic hydrodealkylation of middle

distillates from liquefaction produces mainly unsubstituted

and methylsubstituted one- to three-ring aromatics, includ-

ing benzene, toluene, indene, naphthalene, methylnaphtha-

lene, biphenyl, acenaphthylene, uorene, and phenanthrene

[38,39]. Catalytic cracking of middle distillates produces

oils that consist mainly of alkylnaphthalenes; hydrodealk-

ylation then provides high-purity naphthalene and methyl-

naphthalene.

The development of many aromatic polymer materials

with superior properties has sparked a great demand for

the appropriate aromatic monomers. The demands for

many aromatics of one to four rings have increased, a

trend that is expected to continue. Since production of

coal tar, an important source for two- to four-ring aromatics,

has declined signicantly in the past decade, there is a need

for developing alternative sources of aromatic chemicals.

One opportunity is to explore the potential of developing

value-added chemicals and specialty materials from liquids

obtained from coal liquefaction. Liquids from coal could be

used as feedstocks for organic chemicals and various carbon

materials, in addition to their use for transportation fuels.

4.2. Aromatic monomers targets for specialty chemicals

There is an increasing demand for monomers based on

aromatic and phenolic compounds, a result of signicant

growth of markets for existing aromatic polymer materials,

and the rapid development of advanced aromatic polymers

engineering plastics, polyester bers, polyimides, and

liquid crystalline polymers (LCPs) [67].

Poly(ethylene terephthalate) (PET) has applications in

bottles, lms, and tapes. Compared to PET, poly(ethylene

naphthalate) (PEN) provides a better oxygen and moisture

barrier, as well as having a 50% greater modulus and higher

thermal resistance. Poly(butylene terephthalate) (PBT) is a

major engineering plastic, sometimes referred to as the

high-performance version of PET [68]. Poly(butylene

naphthalate) (PBN) outperforms the high-performance

PBT in chemical and thermal resistance and tensile strength.

The superior properties of PEN and PBN, derived from

naphthalene-based monomers, give them signicantcommercial potential.

Most LCPs are made from naphthalene-based and biphe-

nyl-based monomers, as shown in Scheme 1 (examples of

advanced aromatic polymer materials). The global market

for LCPs is about 4540 t, about 50% in the Asia-Pacic

region [69]. Celanese's Vectra is made from 6-hydroxy-2-

naphthoic acid, 4-hydroxybenzoic acid, and terephthalic

acid. Vectra's tensile strength is about 10-fold greater than

regular engineering plastics such as polycarbonate resins. Its

heat deection temperature is also fairly high, up to 2408C,

and its linear expansion is similar to that of metal. Amoco's

Xydar is synthesized from 4,4

0

-biphenol, p-hydroxybenzoicacid, and terephthalic acid [70]. Xydar's heat deection

temperature is the highest of the thermoplastic engineering

plastics, < 3508C. Its heat-resistance is comparable to high-

temperature heat-resistant polyimides. Despite their cost,

LCPs are enjoying 25% annual growth worldwide and are

likely to maintain that growth rate.

4.3. Value-added chemicals via selective catalysis

Recently it has become an important subject of research

to develop more value-added chemicals or specialty

chemicals using the components that are relatively more


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abundant in coal-derived liquids [7173]. It has been

reported both in early [52,7476] and recent literature

[56,77] that the contents of representative two- and three-

ring aromatic compounds in coke oven tars generally

decrease in the order of naphthalene (811 wt.%).

phenanthrene (47 wt.%). anthracene (12 wt.%).

biphenyl (0.31.2 wt.%). There are many components in

coal tar, but certain ones are concentrated more in narrow

cuts of distillate fractions [77]. Naphthalene and alkyl-

naphthalenes, as well as biphenyl and alkylbiphenyls, repre-

sent important two-ring structures in the aromatic fraction of

liquids from coal carbonization [74,78], from coal lique-

faction [79], and from pyrolysis and gasication (in Lurgi

gasiers) [74,80,81]. Among the heteroatom-containing


Scheme 1.

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compounds, phenol is the most abundant structure. 1-

Naphthol is one of the components in tar acids extracted

from coal tars, whose content is about 2 wt.% of the taracids fraction in high-temperature coke-oven tars [78].

Quinoline is the dominant component in tar bases extracted

from coal tar distillates [74,78].

Phenanthrene and its derivatives are rich in coal-derived

liquids such as tars from carbonization or pyrolysis, but their

commercial use is still very limited [76]. On the other hand,

anthracene and its derivatives have found wide industrial

applications [76]. Some catalysts selectively promote the

ring-shift isomerization of sym-octahydrophenanthrene

(sym-OHP) to sym-octahydroanthracene (sym-OHAn) [82].

Under mild conditions, some zeolites afford over 90% selec-

tivity to sym-OHAn with high conversion ofsym-OHP [83].This could provide a cheap route to anthracene and its deri-

vatives from phenanthrene. Potential applications of sym-

OHAn includes production of anthracene (for dyestuffs),

anthraquinone (pulping agent), and pyromellitic dianhy-

dride (the monomer for polyimides such as Du Pont's

Kapton).

Shape-selective alkylation of naphthalene over molecular

sieve catalysts produces 2,6-dialkyl substituted naphthalene

(2,6-DAN). 2,6-DAN is needed as feedstock for monomers

for such advanced polyester materials as PEN, PBN and

LCPs shown in Scheme 1. With shape-selective catalysts,

regioselective alkylation of naphthalene can be achieved

with over 65% selectivity to 2,6-DAN, using isopropanol[84,85] or propylene [8587] as the alkylating agent. Shape-

selective alkylation of biphenyl can produce 4,4 0-dialkyl

substituted biphenyl (4,4-DAB) [86], the starting material

for monomers of LCP materials such as Xydar (Scheme 1).

Commercial decalins from naphthalene hydrogenation

are almost equimolar mixtures of cis-decalin and trans-

decalin. cis-Decalin isomerizes to the trans-isomer at low

temperatures (2508C) over some zeolite catalysts [82].

Some zeolite-supported metal catalysts were found to be

more effective than zeolites alone [88]. trans-Decalin has

thermal stability substantially higher than the cis-isomer at

temperatures above 4008C. Possible applications are high-

temperature heat-transfer uids and advanced thermally

stable jet fuels, which can be used as heat sinks for thermal

management on aircraft.

Zeolite-supported metal catalysts can selectively promote

the naphthalene hydrogenation and the formation of cis-

decalin or trans-decalin [89]. For example, we can now

produce cis-decalin, with over 80% selectivity (or, alterna-

tively, over 80% trans-decalin) at 100% conversion using

zeolite-supported catalysts at 2008C [89]. cis-Decalin may

have potential industrial application as the starting material

for making sebacic acid. Sebacic acid can be used on a large

scale for manufacturing Nylon-6,10 [55]. It has some inter-

esting new applications in pharmaceuticals, such as the

production of biodegradable polymers for surgical implants

in the treatment of brain tumors [68].

More recently, we have extended our catalysis work to

selective catalytic hydrogenation of heteroatom-containing

polycyclic aromatics. Hydrogenation of 1-naphthol can

produce a number of products, including tetralone, 5,6,7,8-tetrahydro-1-naphthol, 1,2,3,4-tetrahydro-1-naphthol and

tetralin [90]. Among them, the formation of tetrahydro-

naphthols, particularly 1,2,3,4-tetrahydro-1-naphthol, is

highly desirable because it can serve as a stabilizer for jet

fuels at temperatures up to 4808C [91]. Monometallic and

bimetallic catalysts were evaluated and titania-supported

PdPt bimetallic catalysts were found to be more selective

towards 1,2,3,4-tetrahydro-1-naphthol [90].

4.4. Phenolic compounds from petroleum and coal

Phenol is one of the major industrial organic chemicals,and ranked among the top 20 in the US. Table 4 shows the

development of phenol production in the US, Western

Europe, and Japan during 19851995 [55,92]. It is currently

produced mainly from a multi-step process starting from

benzene. Benzene is separated from the BTX fraction

extracted from catalytically reformed naphtha or pyrolysis

gasoline. The puried benzene is converted to cumene

(isopropylbenzene) by catalytic isopropylation over an

acidic catalyst. Subsequently, cumene is converted to

cumene hydroperoxide, which produces phenol and acetone

upon acid-catalyzed cleavage. About 97% of the total

synthetic phenol in the US (until 1987), and over 90% in

Western Europe, and 100% in Japan (until 1990) was manu-factured by this process. The world capacity for phenol

using the cumene process is currently about ve million

tonnes per year. In 19901991, a new process based on

toluene was introduced, and this route is now used for

about 91% of phenol production in Western Europe [55].

Phenol is still the largest-volume chemical derived from

benzene, and its production currently consumes about

20% of the total benzene production [55]. In addition to it

being synthesized, phenol is also produced in smaller quan-

tities from tar and coke-oven water from coal coking and

low-temperature carbonization of low-rank coals. Phenols,


Table 4

Phenol production in the US, Western Europe and Japan (in 1000 metric

tonnes). Sources: (a) Weissermel and Arpe [55]; (b) News-PhOH. C&EN,

Facts & Figures, June 24, 1996

Country Phenol source 1985 1991 1995

USA Synthetic phenol 1260 1553 1873

From tar and wastewater 24 27 27Total 1284 1580 1900

Western Europe Synthetic phenol 1157 1460 1493

From tar and wastewater 14 28 14

Total 1171 1488 1507

Japan Synthetic phenol 255 568 771

From tar and wastewater 2 2 N/a

Total 257 570 771

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cresols and xylenols are recovered by washing with alkaline

solutions and treating the acid solution with CO2.

By carefully designing the reactions, we can convert

coals into liquids that are rich in aromatic compounds andphenolic compounds, which are valuable chemical feed-

stocks. Phenol can be directly separated from liquids

produced from coals through pyrolysis, carbonization,

hydropyrolysis or liquefaction. It has been shown that

phenolic compounds are dominant components in the

products from pyrolysis of low-rank coals, as demonstrated

by ash pyrolysis-GC-MS of several subbituminous coals

[18,93]. Analysis of products from coal liquefaction also

indicated this trend [9498]. Phenols can be extracted

from coal-derived liquids by traditional or non-traditional

methods. They can be separated directly from the coal

liquids by liquid-phase extraction [33,34,65,66], and canbe used as is or converted into monomers such as bisphenol

A and 2,6-dimethylphenol for making aromatic polymers

and engineering plastics.

One may argue that the market for phenol is relatively

small and if there was one large coal liquefaction commer-

cial plant, the phenol from such a plant could saturate the

current market. The pessimistic view may take this consid-

eration as a show-stopper for further progress in phenol

utilization. However, it should be pointed out that proactive

actions could open up new opportunities and new applica-

tions. If phenol can be produced in larger quantities, other

applications of phenol may become attractive in addition to

its current uses, which may also become competitive tosome other industrial manufacturing processes that

currently do not use phenol.

4.4.1. Industrial uses of phenol

Table 5 shows the industrial uses of phenol in the world.

The current industrial uses of phenol include the production

of phenolic resins (Bakelite, Novolacs), bisphenol A, capro-

lactam, alkylphenols, and adipic acid, as well as some other

uses, as shown in Table 5 [55]. Bisphenol A, also known as

2,2-bis-(4-hydroxyphenyl)propene, produced from con-

densation of phenol and acetone, is widely used in the

manufacture of synthetic resins and thermoplastics, such

as polycarbonates.

Some industrial uses of phenol can increase signicantly

if an inexpensive and stable supply of phenol can be devel-oped from coal or petroleum. For example, caprolactam is

an important industrial organic chemical, with a worldwide

production capacity of 3.44 million tonnes in 1989 (with

0.96, 0.60, and 0.51 million tonnes per year in Western

Europe, US, and Japan, respectively). It is used for manu-

facture of Nylon-6. It is synthesized mainly from a multi-

step process with cyclohexanone as the key intermediate.

Most cyclohexanone is made from cyclohexane oxidation to

form a mixture of cyclohexanol and cyclohexanone, and

cyclohexanol in the mixture is isolated and then oxidized

to cyclohexanone. Cyclohexane is produced from benzene

hydrogenation [99]. A second route to cyclohexanone isthrough phenol hydrogenation. In 1990 about 63% of the

worldwide caprolactam production was based on cyclohex-

ane oxidation and with the remainder came from phenol

hydrogenation route and other routes.

Earlier phenol route involves a two-step process, ring

hydrogenation to cyclohexanol over nickel catalyst and

then dehydrogneation over Zn or Cu catalyst to cyclohex-

anone [100]. Some of the catalysts developed for commer-

cial operation of cyclohexanol dehydrogenation to cyclo-

hexanone are Cu/MgO and Cu/ZnO catalysts containing

alkali promoter [101]. However, recent research using

some noble-metal-based catalysts has made it possible to

selectively convert phenol to cyclohexanone in one step.For example, some recent results show that very high selec-

tivity to cyclohexanone can be obtained in a single step

under the conditions of phenol hydrogenation over

supported noble-metal catalysts modied in specic ways

[102].

Cresols and xylenols can be obtained from coal liquids or

from methylation of phenol. The demand for o-cresol and

2,6-xylenol has increased recently, so that the demand can

no longer be met solely from petroleum and coal tar sources

[55]. o-Cresol is favored in methylation of phenol at 300

3608C under 4070 bar over an alumina catalyst; at higher


Table 5

Industrial uses of phenol in the World, US, Western Europe and Japan (in 1000 tonnes)

Sources: (a) Weissermel and Arpe [55]; (b) News-PhOH. C&EN, Facts & Figures, June 24, 1996

Product World USA Japan Western Europe

1989 1995 1985 1995 1986 1994 1985 1994

Total (million metric tonnes) 4.70 5.23 1.07 1.79 0.25 0.50 1.05 1.25Distn (%)

Phenol resins 36 37 40 30 36 33 41 29

Caprolactam 7 15 18 17 17 16

Bisphenol A 20 32 22 35 29 39 22 27

Adipic acid 1 2 1 1 1 2

Alkylphenols 5 2 4 6 4 4 4 6

Miscellaneousa 21 12 15 11 26 24 24 20

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temperature and pressure, 2,6-xylenol is favored. 2,6-Xyle-

nol is the starting material for polyphenylene oxide

(Scheme 2; synthesis of polyphenylene oxide via condensa-

tion of 2,6-xylenol), a thermoplastic with high heat and

chemical resistance and excellent electrical properties

developed by General Electric [11,55].

One option for the coal chemicals community may be to

wait and let others take the rst step (and also the risk). The

result may be a further shift in market away from coal-based

chemicals. For example, while some researchers on coal

chemicals still think the market for phenol is too small for

coal-based chemicals, several new processes have beendeveloped in the petrochemical and chemical industries.

As an example, the earlier cumene process using the

Lewis acid, AlCl3, catalyst was replaced by new processes

using solid acid catalysts such as Al2O3-supported phos-

phoric acid. A recent development in the 1990s is another

new cumene process commercialized by Dow Chemical

Company that uses chemically modied mordenite as a

catalyst for benzene isopropylation. Even more recently, a

new type of process based on the direct oxidation of benzene

with nitrogen oxide to produce phenol over a molecular

sieve catalyst was developed and is being commercialized

by Solutia [103].

4.4.2. Possible new uses of phenol

One possible use is to make oxygenated compounds as an

alternative to current fuel additives such as methyl-tert-

butyl ether (MTBE). The use of MTBE for reformulated

gasoline is under increasing scrutiny for its possible health

and environmental effects, and may well be banned in the

US. As an alternative, methylcyclohexyl ether (MCHE)

may be a potential oxygenate additive for liquid fuels.

Phenol can be hydrogenated to cyclohexanol and its conden-

sation with methanol can produce methylcyclohexyl ether

(MCHE). Phenol can be selectively hydrogenated into

cyclohexanol over certain catalysts [102]. Methanol is a

larger-volume commodity chemical, and can also be

obtained from coal gasication followed by synthesis

from syngas over CuZn type catalysts.

Potential new markets for phenol including coal-

derived phenols can be developed by exploring more

environmentally benign syntheses that use phenol and

which can replace existing ones involving more corrosive

acids or toxic reagents. Several examples are given below.

The phosgene-free synthesis of diaryl carbonate is an

important research topic area, because phosgene, currently

used for making some industrial organic chemicals, is

highly toxic. Diphenyl carbonate is an essential starting

material for the phosgene-free synthesis of an importantengineering plastic material, polycarbonate resin, as

shown in Scheme 3 (synthesis of polycarbonate by phos-

gene-free route via trans-esterication of bisphenol A with

diphenyl carbonate). Direct synthesis of diphenyl carbonate

can be carried out using phenol. For example, oxidative

carbonylation of phenol can be carried out using carbon

monoxide and air over PdCu based catalyst to produce

diphenyl carbonate [104].

Aniline is an important industrial organic chemical, used

in, among other things, the manufacture of dyes, medicinal

agents, and resins. In 1993 the production of aniline was

537, 508, and 184 thousand tonnes in the Western Europe,US, and Japan, respectively. Aniline is currently synthe-

sized by a multi-step process: nitration of benzene, followed

by hydrogenation of nitrobenzene. Direct synthesis of

aniline from phenol and ammonia can be carried out using

MFI-type molecular sieve catalysts. For example, a gallium-

containing MFI type catalyst has been found to be effective

for the aniline synthesis from phenol [105].


C

Me

Me

OHHO

HO OH

Me

Me

C

C

Me

Me

OO

C

O

O

C[ ]n

Bisphenol A

O

C ClCl

Polycarbonate

OO

Scheme 3.

OH

MeOH

MeOH

Me

O

Me

Me

[ ]n

+

Scheme 2.

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4.4.3. Catechol-type compounds

Catechol is a useful industrial chemical (e.g. photo-

graphic materials), and can be synthesized from hydroxyla-

tion of phenol. Notari and coworkers have developed a new

process for hydroxylation of phenol to produce catechol

over microporous crystalline titanium silicate catalysts

[106]. Such a reaction can also be promoted by other cata-

lysts, such as a VZrO complex oxide [107]. On the other

hand, catechol is present in relatively high concentrations in

liquids derived from pyrolysis of low-rank coals [18,96].

Some catechol derivatives are also valuable chemicals.

For example, veratrole (ortho-dimethoxybenzene) is impor-

tant for the production of alkaloids and pharmaceuticals.

Veratrole can be synthesized in the vapor phase using cate-

chol and dimethyl carbonate over alumina loaded with

potassium nitrate [107].

5. Carbochemistry as organic synthesis

The aromatic nature of coals, and the prevalence of poly-

cyclic aromatic systems, is a key consideration in making

coals attractive feedstocks for the future production of

specialty chemicals and monomers. Existing markets for

aromatic chemicals, particularly two- to four-ring

compounds, rely heavily on coal tars generated as by-

products from making metallurgical coke [55].

As shown in Table 3 and Figs. 35, coke production from

coal has declined in most countries during 19881997, except

in China. There seems to be little prospect for a marked surge

in production of metallurgical coke particularly from by-

product coking ovens in the foreseeable future [12,108].Consequently, there is a need for developing an alternative

source of aromatic chemicals in the future. An alternative to

the reliance on liquids from direct liquefaction, discussed

above, would be the direct synthesis of chemicals from coal.

This direct approach is an endeavor to apply the concept

of conducting an organic synthesis to the chemical reactions

of coals. As is well known, in doing an organic synthesis one

selects a starting material for which the structure, and, very

often, the stereochemistry, are thoroughly known, applies a

reagent for which, usually, the mechanism of is known; and

tries to choose reagent and reaction conditions such that the

desired product is the only material formed in high yield, or

at least is easily separable from any co-products. Not somany years ago the application of this concept to coal chem-

istry would have been regarded as hopeless, and likely

preposterous. Various kinds of average structures have

been proposed for coals, some of which lose sight of the

fact that organic chemistry is a three-dimensional science,

and have bond strains or other steric constraints that would

prohibit even their forming. Mechanisms of coal reactions

are still subjects of vigorous debate. Reactions of coals are

notorious for producing products with dozens, if not

hundreds, of individual compounds, few of which are

present even at the 1% level. However, the continuing prob-

ing of coal structure with a wide array of instrumental tech-

niques, and the recent emergence of powerful computer-

based structural modeling applied to coals (as, e.g. in the

work of Nakamura and colleagues [42] and references

therein) provides a signicant base of knowledge. Reasons

for giving credence to some of the newer computer-based

models include the fact that they are energy-minimized, and

the noteworthy observation that in many cases they predict

rather accurately physical properties such as the helium

density. Modeling is also in progress on macerals or litho-

types of coals. Valid structural models will allow moving

building toward the rational planning of direct routes from

coals to chemicals and materials.

Substantial advances have been made in the past two

decades on analytical characterization of coal composition

(maceral, elemental, trace metals, etc.) and coal structure

(carbon skeleton, ring structure, protonated and non-proto-

nated carbons, connecting linkages, heteroatom distribution,

and three-dimensional structure) by combinations of spec-

troscopic characterization (NMR, IR, XRD, XPS, EXAFS),physico-chemical methods (adsorption, swelling, diffusion-

MRI), chemical probe reactions (hydrogen donoracceptor,

and RICO reactions) and computer modeling.

Today, it has become possible to quantitatively detect the

aromatic structures by measuring them and then cutting

them out, and to identify the ring types and the connecting

linkages between the aromatic structures through a combi-

nation of analytical techniques. The chemical probe reaction

RICO, coupled with solid-state NMR and ash pyrolysis-

GC-MS, allows for quantitative structural analysis, and no

longer just compilation of average structural parameters.

For heavy liquids, 2D HPLC using a normal-phase columncoupled with a photodiode array detector (rather than a

single-wavelength UV detector or refractive index detector)

can be used for both separating and identifying the polycyc-

lic aromatic components that contain up to nine condensed

rings [97].

The following questions were raised in a recent confer-

ence that needs to be addressed in future coal chemical

research [49,109]:

1. How can we make best use of this newly generated

knowledge in coal structural and compositional informa-

tion to design rational approaches for converting coal to

chemicals, fuels, and materials?2. What are the fundamentally important issues that we

need to explore with respect to coal composition

structurepropertyreactivity relationships?

3. What are the key elements of smart design for envir-

onmentally friendly conversion processing schemes that

depart from conventional cook and look approaches?

6. Carbon materials from coals

Since all coals are carbon-rich solids, they are potential


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starting materials for other, higher value materials via

conversion to new carbon-based solids. It is now well

known that various useful carbon-based materials and

composite materials can be made from coals, coal tars,petroleum pitch, and coal liquids from liquefaction and

coal pyrolysis, as shown in Table 6 [11].

6.1. Metallurgical coke

Today, the major non-fuel use of coal is carbonization to

make metallurgical coke. As shown in Table 3, about 324

million tonnes of coke are produced annually in the world

[7,10,6063]. The worldwide production data in Table 3

and the trends in Figs. 3 and 4 clearly show that the coke

production has decreased worldwide, except in China up to

1997. The coke production in China increased signicantlyuntil 1997, in contrast to the downward trends in the US and

Japan, as shown in Fig. 4. However, the major increase in

coke production in China does not mean a corresponding

increase in coal tar production. A close examination of

situations in China indicates that the majority of enhanced

coke production was due largely to the use of primitive coke

ovens, as shown in Fig. 5, where typically a high-quality

coking coal was used without blending and the coal tar was

burned for energy use [62,110]. Consequently the by-

product coal tar production has fallen off in step with the

drop in coke making in most countries. It has been reported

recently that the primitive coke production in China was

reduced dramatically from 67.2 million tonnes in 1997 to41.1 million tonnes in 1999, which resulted in a decrease in

total coke production from 139.0 to 121.1 million tonnes

[63,111].

Currently there are 25 coke plants in the US [112]. There

are developments in steel production and there are shifts in

materials that affect the future of coke production from coal,

both in terms of demand and production methods. A report

by IEA provided a review of developments in technologies

and social environments affecting metallurgical uses of coal

[113]. In the US, the projected decline in consumption of

coking coal at coke plants results from the displacement of

raw steel production from integrated steel mills (which use

coal coke for iron ore reduction and for energy input) by

increased production from mini-mills (which use electric

arc furnaces) and by increased imports of semi-nished

steels [64]. The amount of coke required per tonne of pig

iron produced is also decreasing, as process efciency

improves and direct injection of steam coal is used increas-

ingly in blast furnaces [64,113].

A number of new technologies for coke making are under

development. In general, they aim at being more environ-

mentally friendly, or providing alternative routes to iron

production, replacing both the coke oven and the blast

furnace. Two new processes are under development in the

US, the Calderon Coking Process and Antaeus Continuous

Coke Process [114]. The Calderon Energy Company is

developing a coking reactor under the sponsorship of US

Department of Energy; the reactor is characterized as a

completely closed coking unit that virtually eliminates tradi-

tional coke plant emissions. Antaeus Energy developed a

two-stage pyrolysis-based process to produce foundry andblast furnace coke [114].

6.2. Activated carbon

Production of activated carbons from coals has been of

interest for years. Excellent reviews, with abundant histor-

ical information, have been published by Derbyshire and

colleagues [115,116]. Activated carbons are used mainly

as adsorbents for liquid- and gas-phase applications. The

amount of coals used worldwide for producing activated

carbons is about 200,000 tonnes per year [117], a signicant

fraction of the world's annual production of activated

carbons, estimated to be about 450,000 tonnes from all feed-stocks. Signicant growth potential exists for this applica-

tion, primarily for water and air purication. The liquid-

phase applications of activated carbons produced from bitu-

minous coals by chemical activation include water purica-

tion, decolorizing, food processing, and gold recovery; the

gas-phase applications cover air purication, gas treatment,

and solvent recovery [118]. Activated anthracites produced

by air treatment prior to steam activation are microporous

with a signicant fraction of the pores having molecular

dimensions [119]. This suggests that molecular sieve mate-

rials could be produced from anthracites.

6.3. Molecular sieving carbons

The amount of coals used worldwide for producing mole-

cular sieving carbons (MSCs) was estimated to be 3000

tonnes per year in 1992; the growth in production of coal-

based MSCs in the past decade has been estimated to be

about 5% per year [120]. The application of MSCs for gas

separation by pressure-swing adsorption is now commer-

cially viable. In the US, MSCs are used for air separation

by Air Products and Chemicals Inc. It is likely that more

companies will be engaged in producing MSCs in the next

century.


Table 6

List of carbon-based materials from coal and coal-derived liquids

Materials from coal Materials from coal-derived

liquids

Metallurgical cokes Pitch-based carbon bers

Activated carbon adsorbents Mesocarbon microbeads

Molecular sieving carbons Carbon electrodesGraphite and graphite-based

materials

Carbon ber reinforced plastic

Composite (coal/polymer,

etc.) materials

Activated carbon bers

Fullerenes or bucky-balls Mesophase-based carbon bers

Carbon nanotubes Carbon whiskers or lament

Diamond-like lms Binder pitch

Intercalation materials Humic acid derivatives

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6.4. Graphites

Current graphite technology uses petroleum cokes as the

ller material. Molded graphite articles have a wide range of

applications, from high-tonnage uses as electrodes in elec-

tric arc furnaces, a $US2.2 billion business in 1991 [121], to

specialty graphites for high-technology uses in chemical

vapor deposition and epitaxial deposition devices.

Anthracites have been of interest as possible replace-

ments for petroleum coke as a ller material in the manu-

facture of specialty graphites. Anthracites are < 95%

carbon. The conventional wisdom of the structure of anthra-

cite is that virtually all of the carbon is in aromatic struc-

tures, and those aromatic structures are, in turn, in large

graphene sheets. Therefore it would seem that an appro-

priate chemical and thermal treatment of anthracite should

convert it to graphite. In her pioneering work, Franklin

classied anthracites as non-graphitizable to 25008C, but

found that they could become highly graphitized if heat-

treated above this temperature [122]. Evans and co-workersreported that graphite formation from anthracite could occur

at temperatures as low as 120013708C in the presence of

graphitization catalysts [123]. In France, considerable work

has been done on the graphitization of anthracites by

Rouzaud and colleagues [124 127].

Russian anthracites from the Donbas basin have been

shown to be useful in metallurgical electrode applications

[128]. Anthracites can also be partially substituted for petro-

leum coke in the manufacture of graphite electrodes [129].

Graphite rods produced from anthracite in laboratory testing

appeared to have higher electrical resistivity than those from

petroleum coke, possibly as a result of lower density [130].In the mid-1990s graphite artifacts were made in an indus-

trial test, but showed physical properties, such as densities

and strength, lower than control specimens made with petro-

leum coke [131]. However, subsequent work has recognized

that anthracites show remarkable differences in graphitiza-

tion behavior even when subjected to identical heat-treat-

ment regimes [132,133]. In 2000, a follow-up industrial trial

using anthracite shown in the laboratory to provide good

graphitization behavior did indeed produce artifacts having

physical properties in the range albeit at the low end of

the range acceptable for specialty graphites [134]. These

encouraging results suggest that with some further modi-

cations to the manufacturing process and careful selection ofthe appropriate anthracite, a market can be opened for

anthracites as replacements for petroleum coke.

Meta-anthracite, of very limited value (

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carbon artifacts. The ability to separate the unburned carbon

from the ash and convert it into a useful carbon product

reduces the carbon content of the ash to a point at which

the ash is once again useful in its own right, and provides a

useful carbon product that can be marketed [144].

Activation of unburned carbon separated from y ash can

tailor the inherent porosity of these carbons into a range

desired for specic applications [145,146]. The mesopore

volume accounts for about 66% of total porosity of the

parent carbons, but after steam activation micropore volume

accounts for some 60% of the total. Steam activation

provides higher surface areas than CO2 or KOH activation.

Solid yields are higher than those typically obtained for

coals under the same experimental conditions. Furthermore,

there are potential applications for this unburned carbon as a

ller material for carbon bodies. Laboratory-scale tests

show that pellets of the unburned carbon (with coal tar

pitch binder) have densities comparable to those using

conventional petroleum coke as the ller [147].

7. Concluding remarks

Ronald Breslow, past president of the American Chemi-

cal Society, recently emphasized that It will become

increasingly clear that it is a crime against the future to

take petroleum and burn it. Not just because of global warm-

ing, but because we are burning away materials that are

tremendously valuable for other uses [148]. A similar

statement is applicable to coal. George Olah, winner of

the 1994 Nobel Prize in Chemistry, pointed out that oil

and gas resources under the most optimistic scenarioswon't last much longer than through the next century.

Coal reserves are more abundant, but are also limited I

suggest we should worry much more about our limited and

diminishing fossil resources [149].

We must think and act based on the unique features and

advantages of coals and make use of them in a most effec-

tive, efcient and responsible way. There are signicant

challenges to researchers to develop efcient and environ-

mentally friendly reactions and processes for coal conver-

sion and utilization in the 21st century.

A new coal chemistry is dawning. The incentive comes

from the combination of the highly aromatic nature of coals

with the expanding opportunities for aromatic specialtychemicals and monomers especially those with polycyc-

lic ring systems and continuing demand for carbon-based

materials. At the same time, environmental concerns over

carbon emissions from combustion may provide a disincen-

tive for future construction of large coal-burning power

stations. Catalytic reactions of the components of coal-

derived liquids, or catalytic transformations of the solid

coals themselves, provide the crucial connection that will

make this new coal chemistry possible. Expansion of the

non-fuel uses of hydrocarbon resources, particularly coals,

is desirable, because coal has the potential to become more

important as source of both energy and chemical feedstocks

in the next century.

This situation represents a subtle, but signicant, shift in

thinking. Coal utilization in today's world is dominated by

combustion (not only direct combustion of the coal itself,

the combustion of coal products such as coke and synthetic

fuels). If some amount of useful byproducts can be made

along the way, doing so represents just a small added bonus.

We argue that, instead, coal should be viewed as a hydro-

carbon source having multiple prospective uses, all of which

are deserving of serious consideration as prospective uses

for this feedstock. That is, coal is a feedstock that can be

converted to chemicals and monomers (for polymers), to

carbon materials, or to energy. Combustion applications of

coal will dominate in the near-term and likely will remain

important for decades, but to ignore now the potential for

alternative uses is only to short-change us in the future.

Acknowledgements

We wrote this article in response to an invitation by the

late Frank Derbyshire, the former editor of Fuel and a friend

of ours. In addition to the dedication, we gratefully

acknowledge the helpful discussions that we had with him

in the past on the topic of non-fuel use and on coal conver-

sion and utilization. Various portions of our research were

supported through funding or donations of special samples

from the US Department of Energy, Pittsburgh Energy

Technology Center, the Pennsylvania Energy Development

Authority, PQ Co, Air Products and Chemicals Inc., and

Duracell Co.

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