Benzene hydroxylation using N2O as oxidant over Fe –Zeolites - Literature Compilations.

Introduction

Conventional process

Direct oxidation process

Catalyst employed Nature of active site : Role of Al and Fe Method of preparation & Method of treatment

Other catalyst employed

New phenol process :AlpoXTM process

Conclusion

Plan of work

Contents

Introduction: Importance of benzene hydroxylation with N2O

Phenol used in Manufacture of phenolic resins

Synthesis of chemicals like caprolactam and adipic acid

N2O is a efficient oxygen donor

Substitution of dioxygen by N2O increase the selectivity over zeolites

N2O is green house gas and ozone depleting agent Catalyst N2O as oxidant Oxygen as oxidant

X(%) S(%) X(%) S(%)

FeZSM-5 Fe2.15 25.6 96.0 3.3 0.0

FeZSM-5 Fe-Al 27.0 99.0 <0.1 -

Fe2O3 5.5 0.0 24.5 0.0

5 mol % C6H6, 20 mol% N2O(O2) +He, T=350C, Ref: Appl.Catal.A,98(1993)1-20

(reproduced from Appl.catal.A.98(1993)1-20

Benzene hydroxylation : Conventional process

cumene

cumenehydroperoxide

1.Alkylation of benzene to cumene

2.Oxidation of cumene to cumene hydro peroxide

3.Decomposition of the hydroperoxide to phenol and acetone

Multistage synthesis,

Intermediate cumene hydro peroxide is explosive,

Co- production of acetone

Demerits

Direct oxidation with O2

Low phenol selectivity and destruction of aromatic ring

N2O as oxidant

1983: Iiwamoto et al developed this process

Catalyst : V2O5/SiO2 ,T= 55O ºC , Selectivity = 70%

However, this process pilot permofermance not met the expectations.

New Catalyst for direct oxidation

1988, E. Suzuki and M.H.Gubelmanm and G.I .Panov were developed HZSM-5 catalyst independly .

Catalyst Temp Reactant ration

Phenol yield

Selectivity Ref

HZSM-5(0.5g)

430 C6.9 kPa:5 kPa

C6H6:N2O

8.1 Chemistry letter 953-956,1988

HZSM-5

(SiO 2/Al2O 3=120

400 C C6H6/N2/N2O

2/5/8

16 95 US Patent 50012801991

HZSM-5 G.I.Panov Russian patent 1988

Direct oxidation with N2O Over HZSM-5

Na-ZSM-5, Co2+,Cu 2+ -ZSM-5 were found to be not active for this reaction.

Hence SuzuKi Gubelmanm ( except G.I.Panov) proposed that bronsted site are active site for the benzene oxidation with N2O.

Catalyst employed

Benzene N2O

Fe-[Al, B]MFICatalysis Today 110(2005)211-220 20 vol % 3 vol % 77 vol % 400 °C 0.5 g 3 l/h 0.6 s g/ml

Fe-BEACatalysis Today,  91-92(2004)17-26 20 vol % 3 vol % 77 vol % 400 °C 0.5 g 3 l/h 0.6 s g/ml

Fe MFIJournal of Catalysis, 221(1) (2004)119-126 1 mol % 3 mol % 36 mol % 400 and 450 ° for 3 h,P= 3 bar

250 mg +500mg

SiO2 C6H6/He (20 ml/min N2O/He (60 ml/min)

Fe/ZSM-5t

Journal of Catalysis 254, 2, (2008) 383-396 1 vol % 4 vol % 9 5 % 350 °C

50 mg catalys 100 ml/min

GHSV of 30,000 h−1.

Fe-MFI

Journal of Catalysis, 233 (1)(2005)136-146

1 vol % 4 vol % 9 5 % 350 °C 100 ml/min GHSV 30,000 h−1).

Fe–Ga–SBA-15Journal of Catalysis article in press 1 vol % 4 vol % 95% 350 °C 0.1 g 100 ml/min GHSV 30,000 h−1).

HZSM-5Applied Catalysis A 210 (2001)103-109 3.8-16.4 mol %0.4–16.7 mol% rest N2 350 °C 1.45 g 60 ml min−1.

Fe-Al-MFI

Journal of Catalysis, 227 (2004) 138-147

1 vol % 5vol % 94% 237-327 °C 0.3-1.0 60 ml/min(STP) GHSV 30,000 h−1).

Temperature(deg C)

Catalyst employed Contact time Journal Name

Catalyst amount Flow rate Helim

Reactants ratio

Representative table for catalysts, ( Many of them not tabulated)

Fe-ZSM-5 prepared by isomorphous substitution, Chemical vapor deposition and ion exchange method were employed

Reaction mechanism and nature of active sites

Bronsted sites Extra framework Fe(-site)

Suzuki (1988),Gublemann(1988)proposed that Bronsted site are active sites

Since Na-ZSM-5,Co-ZSM-5 and Cu-ZSM-5 are not active for the benzene hydroxylation

Protonation N2O

Then react with benzene

G.I. Panov and coworkers proposed that -site are active.

N2O on Fe-ZSM-5 produces -oxygen , which will react with benzene to phenol.

Correlation between -site and catalytic activity was established

Catalytic activity of HZSM-5 attributed to the presence Fe impurity

During the synthesis. (source materials).

Concept is widely accepted

Reduction of no of Bronstead acid site by (steaming) increases alpha-site and reaching maximum.

Further decreases in Bronstead site decrease the alpha-site in the catalyst.

Certain reduction of Bronstead site leads to higher phenol production

Optimum level of Bronstead site can lead to that optimum for given level of Iron in the catalyst.

Steaming reduces the Bronstead site and probably create the specific arrangement of extra frame work acidic Aluminum atoms.

Topics in Catalysis 13(2000) 387-394

Reaction pathway

Properties of -sites

1. -sites is formed on Fe – ZSM -5 & Loosely bound to the system.

2. Thermally stable up to 300ºC, above that it desorbs irreversibly.

3. Only produced from N2O,highly reactive.

4. Benzene conversion increases with concentration of -sites and attains a plateau at high concentration due to the inhibiting affect of product.

-sites are binuclear iron complexes stabilized in the zeolites miropore of zeolite.

-site binuclear iron species confirmed by 18 O labeling.

Formation of -sites and -oxygen

Assumed mechanism of -sites

Structure (i) is formed by leaching from Fe-ZSM-5

At high temperature treatment oxygen desertion take place and Fe 3+ reduced to Fe2+ (complex). reversible step.

For the formation of -site Fe 2+ should be converted to new stable state loss their ability to react with O2 (thus step is (i) irreversible).

Fe 2+ stabilization appeared to be depends on chemical composition of matrix and it is strongly facilitated by the presence of water vapor.

Reversible redox transition Fe 2+ ( ) <-> Fe 3+ ( ). This provides selective transfer of oxygen atom from N2O to Benzene

Catalyst activity per gram of iron increases as the iron concentration decreases

Reactivity of generated oxygen species from nitrous oxide over Fe-Al-MFI

Phenol productivities per gram iron as a function of reaction time of various steam-treated samples (■) [Fe,Al]MFI (1:4), (□) [Fe,Al]MFI (1:8), ( ) [Fe,Al]MFI (1:16), and (○) [Fe,Al]MFI (1:32). [Fe,Al]MFI (1:24) is similar to [Fe,Al]MFI (1:32), and is not shown

Catalysis today 110(2005)221-227

Catalytic activity data indicates that only a fraction of iron is catalytically active in the direct oxidation of benzene to phenol.

Not all oxidized Fe 2 + to Fe 3+ species were able to generate active oxygen species needed for the oxidation of benzene to phenol

The Mössbauer parameters of the high-spin Fe component are very similar to the high-spin Fe complex observed by Panov and coworkers which they attributed to binuclear iron complexes.

[Fe,Al]MFI

Mössbauer spectra of all samples show a single high-spin Fe component.

However, Various iron species are active. These species are most likely a distribution of isolated extra-framework.

Highly dispersed extra-framework iron species are the active centers (low concentration of iron) Catalysis today 110(2005)221-227

Initial N2O conversions and (□) initial phenol productivities as a function of Fe ions (wt.%) in various steam-treated samples

Binuclear oxygen bridged Fe-ox ions are catalyzing N2O decomposition.

Mono nuclear iron is active for benzene hydroxylation.

Mononuclear Fe ion supported at the AlO4 site of the FeZSM-5 zeolite is the active center .

Though Panov group postulated Binuclear site, They did not exclude the possibility of mono nuclear Fe species

Feoxide nanoparticel catalyzing the deep oxidation

J.Phy.Chem B 107,11404, J.Phy.Chem B 104,734, Journal of catalysis 221(2004) 119-126

Nature of active site

Role of Al

Role of Al in the selective oxidation of benzene to phenol by N2O

Steaming: 10 ml/min H2O,18ml/min O2 72 ml/mi N2 at 973K for 3 h

Reaction :C6H6/N2O/He = 1/4/95 flow rate = 100 ml/min T=623 K

Catalyst Fe

(wt %)

Al (wt %)

Treatment Phenol

Fe-MFI 0.55 0.005 steaming 0.2

Fe-Al MFI 0.51 0.94 steaming 6.8

Fe-MFI +Me3Al 0.55 1.4 steaming 4.9

Silicalite 1 - 0.005 steaming 0.0

Silicalite Fe imp 0.62 0.005 steaming 0.3

Silicalite Fe,Al imp 0.61 0.98 steaming 4.9

Formation of extra framework Fe-O-Al active species confirmed by XANES

J.Catal,226(2004)466-470

Role of Aluminum in the activity

Fe-Si samples required 10 -30 % higher Fe content compared to Fe-Al-Si

Aluminum does not effect the composition & properties of iron containing active site, but helping for more favorable distribution of iron in the zeolite matrix.

Phenol productivity [Fe,Al]MFI (  ), steam-activated silicalite-1-Imp(Fe,Al) (●), steam-activated [Fe]MFI (■), and silicalite-1 (  ).

There is a distinct difference in the reducibility of Fe in steam-activated [Fe]MFI and [Fe,Al] MFI zeolites

Reduction of Fe in presence of Al is taking place ,where as in absence of Al there is an almost negligible part of iron is reduced.

This difference implies the involvement of Al in the formation of Fe centers.

Fe-MFI Edge energy

Ferric

I (Centroid)

Ferrous

I (Centroid)

RT, wet 7123.5 0.14(7113.7) -

723 K 7123.0 0.13(7113.7) 0.006(7112.3)

RT, dry 7123.2 0.13(7113.7) -

Fe-Al-MFI

RT, wet 7124.2 0.079(7113.7) 0.005(7112.2)

723 K 7120.0 0.070(7113.7) 0.072(7112.4)

RT, dry 7120.4 0.080(7113.7) 0.053 (7112.4)

A )Intensities (I)±10%; centroid position (eV)

±0.5 eV.

J.Catal226(2004)466-470

Benzene selectivity for steamed silicalite-1-Imp(Fe,Al) is close to 100% from starting.

Simple dispersion of Fe,Al on silicalite appear to be more stable and durable catalyst

Effect of Al and Iron

Rate of phenol formation as a function of reaction time for (■) [Al]MFI(st), (●) [Fe]MFI(st), (  ) [Fe,Al]MFI, (  ) [Fe,Al]MFI(st)

(reaction temperature 623 K, feed composition: 1 vol % benzene, 4 vol % N2O, 95 vol % He, GHSV 30,000 h).

Highly dispersed or mononuclear Fe species stabilized by extra framework Al species.

Denoted as Fe O Al It may be that these extra framework Fe O Al species are stabilized at defect sites of the zeolite.

Active site is mixed iron and Aluminum oxide species (Fe-O-Al )which is Stabilized on the zeolite micropore .

J.Catal 233(2005) 123-135

Nature of active site ( Fe-Al-O ) :

Fe-MFI, Al-MFI, Fe-Al-MFI, Fe-Al-MFI st and HZSM-5 were employed as catalyst

Steam activation: O2/H2O/He (18/10/72)at 973 K for 3 h

IR study of NO adsorption of Fe-Al-MFI and Fe-MFI+me3Al shows the band at 1630,1636 cm-1, which reveal the formation of Fe-Al-O species.

Extra framework Fe-Al-O stabilize on zeolite structure active for benzene oxidation with N2O

Fe-MFI, Al-MFI, and Fe-Silicalite are not active for benzene oxidation

Phenol productivities (mmol g h) as a function of the reaction time for (●) [Fe]MFI-st, (▪) [Al]MFI-st, (  ) [Fe,Al]MFI, and (  ) [Fe,Al]MFI-st.

was 623 K. C6H6/N2O/He = 1/4/95 flow rate = 100 ml/min T=623 K

IR spectra of the region 1500–1800 cm. Catalyst samples were calcined at 823 K and cooled to room temperature in vacuo. Subsequently, they were exposed to 5 mbar NO for 30 min and evacuated. Spectra were recorded at 298 K.

J.Catal,220(2003)260-264

Appearance of strong new bands around 1620 and 1635 cm-1, which are linked to the presence of extra framework Fe- O- Al.

Method of preparation : different route

1. Isomorphous substitution

2. Me3Al+Fe-MFI

3. FeCl3+MFI,

Isomorphous substitution showing promising activity and steaming further improve the activity

The degree of full combustion

Sublimation of FeCl3 to [Al]MFI > steam-activated Fe-Al-MFI > Me3Al+Fe-MFI > Fe-Alimpregnated silicalite-1.

Catalysts prepared by grafting of molecular species have activity similar to hydro thermally synthesized catalysts with lower selectivity

Steaming of silicalite-1 impregnated with Fe and Al catalyst with high selectivity and a rather low deactivation rate.

Journal of Catalysis, Volume 233, Issue 1, 1 July 2005, Pages 136-146

Method of preparation of catalyst

I. Yuranov et al. / Applied Catalysis A: General 319 (2007) 128–136

Low activity of post synthesis zeolites attributed to Fe2O3 particle occurring in large quantity,

which may limit the access of benzene to the active site

Effect of high temperature treatment

Fe/ZSM-5 by sublimation of FeCl3 on HZSM-5

(i) Fe/ZSM-5 was calcined in an artificial air flow (200 ml min, 20 vol% O2 in He) at 973 K for 3 h (denoted as Fe/ZSM-5(HTC); HTC, high-temperature calcined) and

(ii) Fe/ZSM-5 was steamed (200 ml min, 20 vol% O2 and 10 vol% water vapor in He) at 973 K for 3 h (Fe/ZSM-5(HTS); HTS, high-temperature steamed).

(iii) (HZSM-5), HZSM-5(HTC) and HZSM-5(HTS),Fe/SiO2 also prepared

FT-IR shows 15% of the original Brønsted acid sites persist in Fe/ZSM-5(HTC ) and 10% is remaining after steaming

Al-NMR confirm the reaction between iron oxides and bronsted protons upon high temperature heating and steaming extract the Al from the framework .

High temperature steaming results in the formation extra framework mixed iron –Alum oxo species

HT Steaming & calcinations increase the pore size and surface area

This is due the extraction of Al from lattice position and migration small iron from micropore to external surface

J.Catalysis 221(2004)560-574

Steaming results in the formation larger agglomerates, may be due effect of water induces a higher mobility of iron oxide species( micropore volume increases)

J.Catalysis 221(2004)560-574

Catalyst Surface area(m2/g

)

Pore volume(cm

3/g)

N2O decomposition (no of sites(g-1)

523 K

HSZM-5 440 0.16 -

Fe/ZSM-5 334 0.12 8.8X1018

Fe/ZSM-5HT 341 0.12 1.6X1019

Fe/ZSM-5HTS 371 0.13 2.0X1019

Catalyst Time =5 min Time =1 h

Xc6H6 Sc6H6 X N2O SN2O

X c6H6

Sc6H6 XN2O S

N2O

Fe/ZSM-5 23 47 35 7.8 11 18 32 1.5

Fe/ZSM-5HT 32 60 36 13 14 27 40 2.3

Fe/ZSM-5HTS 39 82 21 38 12 >99 5 66

HSZM-5 18 60 4 60 7 >99 2 >98

HSZM-5 HTS 32 61 5 94 13 >99 3 >98

J.Catalysis 221(2004)575-583

1 Vol% Benzne: 4 vol % N2O: 95 He,100 ml/min

Effect of steaming

Catalyst Benzene(5min ) N2O(5min) Benzene (1h) N2O(1h)

Con(%)

Sel

(%)

Con

(%)

Sel (%)

Con

(%)

Sel

(%

Con

(%)

Sel

(%)

Fe AlMFI 22 69 10 36 7 >98 3 59

Fe AlMFI steam

38 68 16 42 14 >98 5 71

Steaming: 1 g +20 vol % 02 in He + 10 vol % water at 973 K

Calcination and steaming improve the catalytic activity of catalyst.

Fe,Al] MFI(st) had a higher rate of phenol formation than [Fe,Al]MFI.

The similar reaction parameters suggest that the difference is due mainly to the larger amount of active sites in the steamed catalyst.

Steaming treatment induces the migration of fraction of iron oxide particle to the external surface.

Steam treatment facilitated the extraction of Al from frame work which leads to the formation of Fe-Al-O

HZSM-5(Fe:0.024%) steam treated shows stable activity compared to HSZM-5

At high temperature reconstruction of Fe specie taking place and stabilized by extra frame work Al.

J.Catalysis 221(2004)575-583

Effect of Steaming

Deactivation and regeneration of Fe-ZSM-5 catalyst

Deactivation occurs due to coke formation :Condensation/polymerisation of product Surface acidity causes the condensation of phenol and polymerization of phenol

3.5 to 4 % coke concentration completely reduced the -site

Kinetics and Catalysis ,41(2000)

Influence of coke on catalytic activity

Coke content T max(C) C x 10 -18.g-1 Phenol productivity (mmol/gh)

0.0 - 2.6 6.3

0.8 528 2.0 5.1

1.4 528 1.6 4.1

1.8 531 1.3 3.6

2.5 532 1.0 2.5

3.5 528 0.4 1.8

Deactivation Effect:

1.Deceasres the no of active sites

2. Quality of active site also decreased

3.Accessibity of pore space decreased. (15 % of pores blocked after20 h of reaction).18 % blocked deactivated completely

Regeneration method

1. 1.7 %O2/He ,at 450º C

2. 2 %N2O/He ,at 425º C

3. Regeneration time 2,6, and 10 h

Method Temp Complete restoration of activity

O2 450º C After 60-65 % coke is removed

N2O 425º C After 30-35 % coke is removed

Appl .Catal. 241(2003)113-121, Kinetics and Catalysis ,41(2000)

Influence of coke on -site

Reaction at benzene excess condition.

Feed Ration: 1 Vol % Benzene: 5 % N2O: 94 He

Benzene hydroxylation is highly exothermic reaction

Liberates (62 kCal/mol per mol of benzene

Decrease the catalyst life by uncontrolled heating

Leads to undesired side products

Hence, benzene concentration increase in the feed

Feed: 5O vol % Benzne : 5 % N2 O : 45 % He (*) High Benzene concentration increases the heat capacity of the reaction mixture by several time thus providing some important advantage. (1) Reduces the uncontrollable heating. (2) Decreases the side reaction. & Selectivity increased (3) Increases the catalyst stabilities

Other Catalysts for Benzene Hydroxylation : Fe-Beta as Catalyst

Fe-Beta generate Fe(II) active sites able to decompose N2O producing surface atomic oxygen and molecular nitrogen

The reaction rate per active site was found to be 2 fold lower than that of Fe-ZSM-5 for benzene hydroxylation.

The low activity attributed to “ the geometry of the ensemble of active sites stabilized in Fe-ZSM-5 compared to Fe-Beta”

Conversion of phenol over Fe-Beta ,1.0g ,1:5:94 =C6H6:N2O:He

FePO4 as Catalyst

FePO4 – prepared from ferric nitrate and ammonium dehydrogen phosphate

Catalyst amount 0.3 g , Flow rate: 30 ml/min, Benzene:0.22gg/h

Table : Catalytic activity of Catalyst: 5 wt % / SiO2

C6H6: N2O molar ratio

Temperature (C)

Conversion benzene

(%)

Selectivity

(%)

Coke content

(wt %)

1:4 400 2.3 93.4 1.82

1:4 450 6.9 89.1 1.68

1:4 500 5.4 73.1 2.44

1:1 450 4.0 88.5 1.79

1:8 450 5.5 78.3 2.18

1:12 450 2.4 75.9 1.20

Appl.Catal,A 244(2003)11-17

TS-1 and Metal modified TS-1 TS-1 , Al,V,Cr,Fe,Co,Ru modified TS-1 prepared by Hydrothermal method T=400 C, Flow rate=7.2 l/h, C6H6: 50 mol% N2O: 5 mol% He = 45 mol% Catalyst volume :1g, Calcined at 550 C, Steam activated at 650 C with 50 % water in Ar fro 2 h TS-1, Al,V,Cr,,Co,Ru modified TS-1 are not active Fe-TS1 found to be active ( 1 wt % found to be optimum )

Microporous Mesoporous Material 48(2001)345-353

Phenol productivity (a) and N2O Conversion (b) on Fe content in Fe-TS-1 sample (o)calcined at 550 C ()steam activated at 650C

Reaction rate of phenol formation (■) calcined Fe–Ga–SBA-15(0.01)), (□) Fe–Ga–SBA-15(0.03) and (○) Fe–Al–SBA-15 as a function of reaction time.

Fe-SBA-15,Ga-SA-15,FeAl-SBA-15,Fe-Ga-SBA-15 were prepared by hydrothermal synthesis. Catalyst amount:0.1 g, Feed=1 vol % benzene+ 4 vol % N2O +He 95%Flow rate=100ml/minGHSV 30,000 h-1

Catalyst No of alpha sie Benzene conversion

1at 0.5h

Selectivity

Fe-SBA-15 0 >0.1

Ga-SBA-15 0 No convesrion

Fe-Ga-SBA-15 0.88 X 10-3 2.3 47

Fe-Al-SBA-15 0.90 X 10-3 5.0 27

Fe-SBA-15 as Catalyst

Chem.Commun,2008,774 -776, J.Catal,255(2008)190-196

Active site density of Fe-Ga-SBA-15 nearly equal toFe-Al-SBA-15

Intrinsic hydroxylation activity of catalytically active site is somewhat lower in Fe-Al-SBA-15.

Catalytic active Fe sites have different chemical properties when bound to Ga or Al

Higher selectivity: lower tendency of Fe-Ga-SBA-15 to hydroxyl ate the phenol to products that do not leave the catalyst surface.

Only small fraction of Fe is active compared to Fe-ZSM-5 (about 15 % active)

Lower selectivity and conversion of Fe-Al-SBA-15 compared to Fe-ZSM-5 due to absence of micro porous environment.

More open surface around the active sites in Fe-Al-SBA-15 doest not limit the formation more bulky reaction product that remain on the surface .

Chem.Commun,2008,774 -776, J.Catal,255(2008)190-196

Fe-SBA-15 as Catalyst

Fe-Silicalite catalyst for the oxidation of benzene with N2O

1.Fe-silicalite- prepared by hydrothermal method

2. Fe-silicalite steam treated at 550C with 75 % steam in N2

3. Fesilicalite treated with Na2SO4/NaCl and HNO3 /NH4NO3 buffer calcined at 550C

Reaction condition: C6H6/N2O/He = 5/20/75 Contact time = 0.5 s (volume of catalyst/overall flow rate) T= 350 C

Na2SO4/NaCl and HNO3 /NH4NO3 redistributing the Fe in much smaller crystals within the zeolite network.

Steam treatment + Na2SO4/NaCl and HNO3 /NH4NO3 leads to in the higher activity

Higher active catalyst has the ratio of LAS/BAS=1.08 , which is more selective to phenol.

Catalyst Time=3h Time=6h

Conv (%) Sel(%) Conv (%) Sel(%)

Fe-silicalite 16 36 18 24

Fe-silicalite steam treated 10 97 11 54

Fe-silicalite Na2So4/NaCl and HNO3 /NH4NO3 treated

12 98 5 100

Ref: APCAT A G 205(2001)93-99,Phy.chem.chem.phy200,2,3301-3305

Selective oxidation of benzene to phenol over FeAlPO-5 using N2O

Catalyst =0.5 g T=653 K, C6H6: N2O:He =1:3.6:5.4,contact time =0.5s

FeAlPO-5 with (1 % Fe ) most active reach 13.4 conversion at 653 K

Phenol yield = 13.0 % .

Chem.Comm,2006,4955-4957

Fe-MCM-22 as catalyst: ( in Abescence of Al)

Fe-MCM-22 hydro thermally prepared.

Benzne :N2O = 1: 4 T= 673 K

Conversion < 5 % (decreases with time on stream) selectivity = 95 %

Calayst employed other than Fe -ZSM-5 are showing lower activity compared to Fe -ZSM-5.

MFI Structure stabilized the active site more than other matrices. (Suits for Active site).Mesoporous materials apparently do not generate the required intimate contact between potentially active Fe sites and reactant molecules.

Promising activity of Fe-ZSM-5

Development of New Phenol Process: The AlphOxTM process

Monosanto and the Boreskov Institute of catalysis (G.I.PANOV) lab RUSSIA developed this process.

Adipic acid production had been modified by directly oxidize benzene to phenol.

T= 482 º C, Feed: 3 Vol % +55 % C6H6+ N2 , Time = 24 h, W/F= 4.52 cat/mol-h

CONVERSION = 1- 4.3 %,BENZENE TO PHENOL = 96 – 98 %N2O TO PHENOL = 87 %, PHENOL PRODUCT = 5 mmol g cat.h

Topics in Catalysis 13(2000) 387-394

Nitrous oxide selectivity to phenol has been dramatically raised from about 40% to above 80% by switching to Benzene rich feed

The AlphOxTM process

Route Direct oxidation with N2O Pd-membrane reactor with O2

Reaction Pathway N2O produces over Fe-ZSM-5 -oxygen which react with benzene forming phenol

H2dissociates react with O2 produce oxygen which react with benzene forming phenol

Reaction Condition 5.5 mol % N2O:50 mol % C6H6.T=400 C 150C-200C,

O2/H2 = 0.5

Phenol productivity

5 mmol/g 0.31 mmol/g

Status Near/Commercial stage Far from economic method

Comparing two new routes for benzene hydroxylation

Possible Conclusions:

Fe-ZSM-5 Most promising catalyst for benzene hydroxylation with N2O.

MFI-Zeolite network suits well for stabilizing the active spices. Confinement of the iron species in pores of suitable geometry (structure and size) is essential to originate active site

Binuclear Fe3+ sites are appears to be active species, however mononuclear possibility not excluded.

Presence of Al in the extra framework is essential for the activity for the formation of (Fe-O-Al) species.

Method of preparation and high temperature steaming influence the activity of the catalyst.

Mass flow controller

Liquid metering pump

N2O/He Evap

orator

Reactor

GC

Benzene

Benzene hydroxylation with N2O