Catalysis in Petrochemical production

Lecture 3

CONTENTS

1. Petroleum feedstocks2. Petrochemicals from different hydrocarbons3. Alkylation reactions4. Shape-selectivity5. Isomerization reactions6. Disproportionation7. Catalytic reforming8. Selective oxidation reactions9. Green polycarbonate synthesis

INTRODUCTION

Feed stocks for petrochemicals are gas and light to middle petroleum liquids Nearly all the petrochemicals are produced over catalysts Both homogeneous and heterogeneous catalysts are involved

Chemicals from methane

C2H6 - C3H8 – C4H10 - naphtha C2H4; C3H6; C4H8 (steam cracking) + Pyrolysis gasoline

Ethane, propane, butane, isobutane, naphtha and kerosene are also feed stocks for many chemicals

Pyrolysis gasoline BTX

Naphtha BTX (Catalytic reforming)

Kerosene n-paraffins n-olefins LAB (separation and alkylation)

Uses of benzene

Nitrobenzene

Cyclohexane

CumeneEthylbenzene

AROMATIC COMPOUNDS

Chemicals from toluene

Xylenes are also important petrochemical products / feed stocks

MeOH acetic acid Vinyl acetate

Ethylene ethylene oxide ethylene glycolEthylene acetic acid Ethylene ethyl alcoholEthylene vinyl chloride

Propylene propylene oxide Propylene glycolPropylene acrylic acid ; acrylonitrilePropylene allyl chloride epichlorohydrin propylene oxide

Petrochemicals – some more examples

Butenes Maleic anhydride

OLEFINS ARE NOT PRESENT IN PETROLEUM

Benzene Maleic anhydrideBenzene Chlorination; nitration etc.p-Xylene Terephthalic acido-Xylene Phthalic acid

Many polymers are derived from the above petrochemicals Hundreds of other chemicals are derived from olefins, BTX, phenol, acetic acid, methanol etc.

Cyclohexane cyclohexanol + cyclohexanoneCyclohexanone Cyclohexanoneoxime Caprolactam Nylon-6Cyclohexanol adipic acid Nylon-6,6

Cumene Phenol + acetoneEthylbenzene styrene

Major reactions in petrochemical production

1. Alkylation2. Isomerization3. Disproportionation4. Selective oxidation5. Dehydrogenation

1. Replace mineral acids by solid acids2. Green selective oxidation reactions a) Adipic acid b) Propylene oxide c) Oxidation of alkanes d) Phenol e) Alkane oxidations with air3. Caprolactam production

Examples:

Petrochemical production has been a major polluting industry Recently, there is an increasing effort to make petrochemical production greener

Greening of petrochemical production

Alkylation of Aromatics

Some important industrial alkylation reactions over acidic zeolites

Reactants Product Catalyst Process licensors

Benzene + ethylene /EtOH EB ZSM-5 Mobil-Badger /NCL etc

Benzene + propylene Cumene H-Y; H-M; H- DOW, UOP etc

Toluene + methanol P-Xylene Modified ZSM-5 Mobil

Benzene + C11 – C13 olefins LAB Solid acid/ RE-Y UOP / NCL

EB + EtOH P-DEB Modified ZSM-5 NCL / IPCL

Naphthalene + propylene 2,6-DIPN H-mordenite Chiyoda

Naphthalene + methanol 2,6-DMN Zeolite Rütgerswerke

Biphenyl + propylene 4,4’-DIPB H-mordenite DOW

Industrial alkylation Processes

Alkylation is the introduction of an alkyl group into a molecule It may involve a new C-C, O-C, N-C bond formationAlkylation is catalyzed by acidic or basic catalysts

INTRODUCTION

Acid catalysts are used mainly in aromatics alkylation at ring-C

Basic catalysts are used in alkylation at side-chain-C

CH3

+ MeOH

CH3

CH2CH3

CH3

Acid Catalyst

Basic Catalyst

(p-Xylene)

(Ethylbenzene)

Example of an alkylation mechanisms

Because the Sec-C+ is more stable, mostly cumene is (> 99.9 %)is produced and not n-propyl benzene (requires the Prim-C+)

Mechanism 1; Sec-C+ is formed

Cumene production:

What are ZEOLITES ?- Aluminosilicates- Crystalline- Framework of AlO4 and SiO4 Td-units- Possess ordered pore systems- Acidity arises from Al-ions

The most important solid acid catalysts in industrial use are ZEOLITES

Sodalite(SOD)Pores ~3Å

Zeolite - A(LTA)pores ~ 4Å

Zeolite - X, Y(FAU)pores ~ 7.4ÅA large cage (~ 12Å)

formed in A and X,Y

Example ofbuilding zeolite

structures

4 & 6 membered rings

[SiO4 ]4- [AlO4]5-

-cagesLTA FAU

ETHYL BENZENE

kg

Data as of year 2000

NCL

Main use of EB: Manufacture of styrene

Albene process(NCL)

15,000 tpa plant was in commercial operation for some years

+ + H2O

CH2 CH3

CH2CH3 OH

Mobil-Badger process is based on ethylene and uses ZSM-5;Other licensors are UOP, CDTECH etc; use other zeolitesCDTECH process uses reactive distillation

Mobil-Badger process

Catalyst is Encilite – pentasil (ZSM-5) type

Mobil-Badger process

Uses ethylene as the alkylating agentT = 370 - 420°C; P = 7 – 27 bars;

[Degnan et al. Appl. Catal. A 221 (2001) 283]

Kg

> 40 SPA units have been licensed (UOP

CUMENE

Main use of cumene: in the production of phenol

CUMENE

NCL processes for alkylation and transalkylation are available

Benzene + propylene Cumene

Process licensors: UOP, CDTECH, Enichem, Mobil-Badger, DOW

Zeolite processes involve a transalkylation (with benzene)step to convert >10 % di i-pr-Bz into cumene

Yield of cumene in zeolite processes is more as transalkylation is not possible with SPA catalysts

CDcumene process (CDTECH)

Reaction is done in catalytic distillation reactor The catalyst is held in distillation traysA transalkylation reactor converts the di-iprBz.

Features

Comparison of two different zeolites in the alkylation of benzene by propene _____________________________________________________________________Parameters Catalyst Catalyst

MCM-22 MCM-56_____________________________________________________________________Temperature, oC 112 113Propene flow, WHSV, h-1 1.3 10.0Propene conversion, % 98.0 95.4Selectivity, %

- Cumene 84.35 84.98- Diisopropyl benzene 11.30 13.20- Triisopropyl benzene 2.06 1.28- C3 Oligomers 1.8 0.52

- n-Propyl benzene, ppm 70 90_____________________________________________________________________

(J.C. Chang et al., US Patent. 5,453,554 (1995))

CH3

+i-Pr

i-Pr

i-PrCatalyst

Diisopropyl benzene transalkylation

Influence of zeolite-type on m/p ratio of DIPrB

LINEAR ALKYL BENZENE

UOP

Evolution ofLAB processes;BecomingGREENER

Benefits in product quality - use of solid acid

Green

Catalyst

AlCl3

AlCl3

HFSolid acid

Production of LAB Alkylation of benzene with C11 – C13 olefins

Heavy alkylates

H2 rich off gas

Distillation

N-paraffin recycle

ParaffinRecovery

BenzeneRecovery

Alkylation Solid-acidCATALYST

Make up H2

PACOL

DehydrogenationPt/Al2O3

SelectiveHydrogenation

DEFINE

Fresh n-paraffin

H2 recycleFresh benzene

Ben

zene recycle

LAB

Linear alkyl benzene (LAB) using a solid-acid catalystLinear alkyl benzene (LAB) using a solid-acid catalyst

Detal process for Linear Alkyl Benzene production

Feed: mixed olefins (C10 - C13) Temp. (°C) = 130 - 180Press. = 5 - 10 barsWHSV (h-1) = 2 - 3 - Conversion > 99.99%; product BI < 50 ppm- The catalyst life was >50 days in a single cycle- Catalyst could be regenerated many times

Operated in RIL in a semi-commercial scale (~ 800 tpa)

NCL alkylation process for LAB using solid acid catalyst

Shape-selective alkylation reactions

1. p-Ethyl toluene

2. P-Diethyl benzene

3. 2,6-Dialkyl naphthalene

4. 4,4’-Dialkyl biphenyl

Product shape selectivity – most useful in aromatic aklkylation

Alkylation of toluene with ethylene (Mobil)

Catalyst:

(%)

AlCl3 – HCl ZSM-5 Modified ZSM-5

Toluene conv. 51.7 25.6 13.8

Ethyltoluene 35.9 22.0 12.3

Other aromatics 15.8 3.0 1.5

Ethyltoluene:

Para 34.0 26.8 96.7

Meta 55.1 60.6 3.3

Ortho 10.9 12.6 0

P-Diethylbenzene

Product shape-selectivity in a zeolite

NCL Process operated in a commercial scale (500 tpa)

+ CH2CH3 OH Zeolite

CH2 CH3

CH2 CH3

CH2 CH3

Alkylation of naphthalene

1-IPN

2-IPN

1,4-DIPN 1,5-DIPN 1,8-DIPN

1,2-DIPN 1,3-DIPN 1,6-DIPN 1,7-DIPN

2,3-DIPN 2,6-DIPN 2,7-DIPN

Scheme 1. The two mono and ten isomeric diisopropyl naphthalenes formed during the isopropylation of naphtalene

2,6-dicarboxy naphthalene is a valuable monomer for the synthesis of PEN polymers This can be produced from the oxidation of alkyl naphthalenesDirect alkyklation yields ten isomers that are difficult to separate

Indirect routes have, therefore, been adopted for their synthesis

CH3

CH3

+ CH2=CH-CH=CH2

Alkali Metal CatalystNaK

Alkenylation

CH3

CH2-CH2-CH=CH-CH3

OPT

CH3

CH3

Zeolite Catalyst

Cyclisation

1,5-DMT

Pt / Al2O3

Dehydrogenation

1,5-DMN

Zeolite Beta

Isomerization2,6-DMN

BP-Amoco route for synthesis of 2,6-dimethylnaphthalene

[Lillwitz, Appl. Catal. A 231 (2001) 337]

CH3

+ C5H10

Zeolite Y

Alkylation

CH3

C5H11

TPs

CH3

C5H11

Pt / Re / Al2O3 / Cl

ReformingDMNs

Pd / Beta

Hydroisomerization

DMTs

Pd / Beta

Hydroisomerization

2,6-DMT

Dehydrogenation

Pt / Na-ZSM-5

2,6-DMN

Chevron-Texaco route for synthesis of 2,6-dimethylnaphthalene

[Lillwitz, Appl. Catal. A 231 (2001) 337]

The 2,6-dialkyl isomer is narrower than the other isomers Can the product shape selectivity of zeolites be applied for the selective alkylation of naphthalene to the 2,6-isomer ?

FAUMORBEA

6.4 x 7.6 Å/ 3D 7.4 Å/ 3D

Cages, 13.2 Å

6.5 x 7 Å / 1D

Framework structures and pore characteristics of some conventional zeolites

Table 3 Isopropylation of naphthalene over conventional zeolites (from Ref. 22) _______________________________________________________________________ Catalyst SiO2/Al2O3 Conversion Product Distribution of di-isopropyl naphthalene,% Ratio % 1,3- 1,4- 1,5- 1,6- 1,7- 2,6- 2,7- _______________________________________________________________________ HZSM-5 70 1.0 - - - -- - HY 7.3 96.1 23.7 0.6 0.2 6.8 4.9 32.6 31.2 HL 6.1 95.1 39.9 7.9 6.7 15.3 16.3 6.7 7.2 HM 25.3 68.3 5.3 3.8 1.9 7.1 6.1 50.8 24.9

A comparison of the activity and selectivity of conventional Zeolites in the isopropylation of naphthalene

* HY and HL zeolites are extremely active, but not selective to 2,6 DIPN* HL has a wider product distribution, rather a poor selectivity to 2,6 and 2,7 DIPN* HM is the most selective (for both 2,6 and 2,7 DIPN), but less active under identical Conditions of reaction

[Y. Sugi et al., Recent Res.Dev.Mat.Sci.Engg., 1 (2002) 395]

Isopropylation of naphthalene over conventional zeolites

Isopropylation of Biphenyl

2-IBP

3-IBP

4-IBP

+

3,2'-IBP 3,3'-IBP

+

2,4'-IBP 2,2'-IBP

4,4'-IBP

3,4'-IBP

+

Three monoalkyl and six dialkyl biphenyls are possible

0

20

40

60

80

100

CIT

-1

CIT

-5

SS

Z-3

1

SA

PO

-5

UT

D-1

SS

Z-2

4

ZS

M-1

2

HM

ZS

M-2

2H

HL

HY

Sele

ctiv

ity o

f 4,4

'-DIP

N (%

)

Reaction conditions: Temp.= 250oC; C3= pressure = 0.8 Mpa

(Y. Sugi et al., Catal. Surveys Japan, 5 (2001) 43)

Selectivity for 4,4’-DIPB over various zeolites in the isopropylation of biphenyl

ISOMERIZATION REACTIONS

Xylene isomerization

Catalysts are usually bifunctional typesTypical examples: Pt-ZSM-5, Pt-mordenite& Pt-(silica)-alumina

Xylene isomerizationXylene isomerization

CH3

CH3

CH3

CH3+

CH3

CH3

+

CH3

CH3

Zeolite

Catalyst: ZSM-5, Mordenite; MAPO; SiO2-Al2O3 loaded with Pt

XYLOFINING developed by NCL-ACC-IPCL in 1986

Mechanism

Restricted transition state shape-selectivity

RTS selectivity is also responsible for: - Resistance of medium pore zeolites to coking

In the isomerization of m-xylene, bimolecular disproportionation into benzene and TMB also take place

Use of zeolites with the right pore-size or cavities to prevent the bimolecular transition state formation increases isomerization selectivity

(bp, 110 - 140°C)

Reforming(Pt-Re-Sn/Alumina)

Fraction-ation

Xylene iso-merizatrion(Pt-ZSM-5; Pt-Mord.;Pt-MAPO)

Fraction-ation

Arom. Extraction

TransalkylationPt/Mordenite

Mol. SieveSeparation(PAREX)

Benzene

Toluene

Xylenes + EB

C9+Arom.

DisproportionationPt/Mordenite

Naphtha

o-Xylene

p-Xylene

m- + EB

Raffinate

Production of xylenes

CH3

CH3

CH3

Catalyst Toluene disproportionation

C9+ aromaticstransalkylation

CH3

CH3

CH3

+

CH3

CH3 CH3

Catalyst

Disproportionation and transalkylation reactions

Catalytic reforming for aromatics production

Desired reactions in Catalytic reforming

60-90°C cut for benzene90-110°C cut for toluene110-140°C for xylenes

The reactions are:

Selective oxidation reactions

Current method is the oxidation of cyclohexanol with HNO3 producing N2O

Noyori’s method is oxidation of cyclohexene in biphasic medium (commercially attractive)

Frost’s method uses an enzyme and a renewable raw material – glucose

Oxidation of n-hexane or cyclohexane over MAPOs

Adipic acid

OH

+

O

O2

-H2

H2

HNO3

COOH

COOH+N2O

Current process for adipic acid

COOHCOOH COOH

COOH O

OH

OH

OH

OHOH

(current route)

(Noyori's route)

adipic acid muconic acid

D-glucose

(Biocatalysis; Frost's route)

Enviro-friendly routes for adipic acid

O2 COOH

COOH

O2

R. Noyori, Science 281 (1998) 1646 K.M. Draths & J.W. Frost, JACS 120 (1998)10545

J. M. Thomas & R. Raja, Chem. Commun. Feature Article, 675 ( 2001)

The present route for acetic acid and vinyl acetate

manufacture is:

CH4 H2 + CO CH3OH (+CO) CH3COOH -- (1)

C2H6 C2H4 ------ (2)

C2H4 + CH3COOH CH2CHOCOCH3 (VA) ----- (3)

Direct vapour-phase catalytic oxidation of ethane to HOAc and ethylene and vinyl acetate:

C2H6 CH3COOH + C2H4 CH2CHOCOCH3

SABIC

- Avoiding multi-step processes - Alterante cheaper raw materials

Oxidation of alkanes

Use of alternate raw materialsselective oxidation reactions that need to be commercialized

1. Propane to acrolein and acroleic acid (presently use propylene)2. Butane to methacrylic acid (presently butene is used)3. Propane to acrylonitrile (propylene used at present)4. Ethane to vinyl chloride (ethylene is used at present)5. Methane to methanol to HCHO and HCOOH(Syn gas used at present)6. n-Hexane to adipic acid(Cyclohexanol and nitric acid used)

H3PO4/zeolite

[O]

N2O

FeZSM-5

TS1

O

OOH

OH

H2O2/

+

(Benzene) (Cumene) (Cumene hydroperoxide)

(phenol)

Phenol production

TS-1 MFI Sumitomo

Production of Caprolactam w.o. (NH4)2SO4

co-production

- Less polluting - Less number of steps- Benign reagents

Environmentally safe route to polycarbonate

Route 2

CO O

O

CH3H3C H2O

DMC+ OH2Transesterification

DPC+ CH3OH

2 CH3OH + CO + 1/2 O2+

DMC

OHHO

BPA

+ CO O

O473 - 593 K

Catalyst BPC + 2

DPC

OH

Route 1

OONa Na + COCl2

NEt3CO O

O

( )n

Bisphenol-A (BPA) (Na salt)

Bisphenol-A Polycarbonate (BPC)

Conventional routes to polycarbonate

PC prepolymer (n=10~20)

CH 2CH 2

+ 1/2 O 2CH 2

CH 2

O (EO)

1

CH 2CH 2 + CO 2

CH 2CH 2

O OC

O

2

(EC)

CH 2CH 2

O OC

O (EC)

+ 2 MeOH MeOCOMe

O

+ HOCH 2 CH 2 OH 3

(DMC) (MEG)

MeOCOPh

O

2

(MPC)

PhOCOPh

O(DPC)

MeOCOMe

O(DMC)

+ 4

PhOCOPh

O(DPC)

+ HO C HO

CH 3

CH 3

O C O

CH 3

CH 3

C

O

OPhH + PhOH 5

n

The green Asahi-Kasei Polycarbonate process

   

O