Catalysis in Petrochemical production Lecture 3

CONTENTS 1.Petroleum feedstocks 2.Petrochemicals from different hydrocarbons 3.Alkylation reactions 4.Shape-selectivity 5.Isomerization reactions 6.Disproportionation 7.Catalytic reforming 8.Selective oxidation reactions 9.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

 C 2 H 6 - C 3 H 8 – C 4 H 10 - naphtha  C 2 H 4 ; C 3 H 6 ; C 4 H 8 (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 Cumene Ethylbenzene AROMATIC COMPOUNDS

Chemicals from toluene Xylenes are also important petrochemical products / feed stocks

MeOH  acetic acid  Vinyl acetate Ethylene  ethylene oxide  ethylene glycol Ethylene  acetic acid Ethylene  ethyl alcohol Ethylene  vinyl chloride Propylene  propylene oxide  Propylene glycol Propylene  acrylic acid ; acrylonitrile Propylene  allyl chloride  epichlorohydrin  propylene oxide Petrochemicals – some more examples Butenes  Maleic anhydride OLEFINS ARE NOT PRESENT IN PETROLEUM

Benzene  Maleic anhydride Benzene  Chlorination; nitration etc. p-Xylene  Terephthalic acid o-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 + cyclohexanone Cyclohexanone  Cyclohexanoneoxime  Caprolactam  Nylon-6 Cyclohexanol  adipic acid  Nylon-6,6 Cumene  Phenol + acetone Ethylbenzene  styrene

Major reactions in petrochemical production 1.Alkylation 2.Isomerization 3.Disproportionation 4.Selective oxidation 5.Dehydrogenation

1.Replace mineral acids by solid acids 2.Green selective oxidation reactions a) Adipic acid b) Propylene oxide c) Oxidation of alkanes d) Phenol e) Alkane oxidations with air 3. 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 ReactantsProductCatalystProcess licensors Benzene + ethylene /EtOHEBZSM-5 Mobil-Badger /NCL etc Benzene + propyleneCumene H-Y; H-M; H-  DOW, UOP etc Toluene + methanolP-XyleneModified ZSM-5Mobil Benzene + C 11 – C 13 olefinsLABSolid acid/ RE-YUOP / NCL EB + EtOHP-DEBModified ZSM-5NCL / IPCL Naphthalene + propylene2,6-DIPNH-mordeniteChiyoda Naphthalene + methanol2,6-DMNZeoliteRütgerswerke Biphenyl + propylene4,4’-DIPBH-mordeniteDOW

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 formation  Alkylation 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

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 AlO 4 and SiO 4 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 ~ 7.4Å A large cage (~ 12Å) formed in A and X,Y Example of building zeolite structures 4 & 6 membered rings [SiO 4 ] 4- [AlO 4 ] 5-  -cages LTA 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  Mobil-Badger process is based on ethylene and uses ZSM-5;  Other licensors are UOP, CDTECH etc; use other zeolites  CDTECH process uses reactive distillation Mobil-Badger process Catalyst is Encilite – pentasil (ZSM-5) type

Mobil-Badger process  Uses ethylene as the alkylating agent  T = °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 trays  A transalkylation reactor converts the di-iprBz. Features

Comparison of two different zeolites in the alkylation of benzene by propene _____________________________________________________________________ ParametersCatalystCatalyst MCM-22MCM-56 _____________________________________________________________________ Temperature, o C Propene flow, WHSV, h Propene conversion, % Selectivity, % - Cumene Diisopropyl benzene Triisopropyl benzene C 3 Oligomers n-Propyl benzene, ppm7090 _____________________________________________________________________ (J.C. Chang et al., US Patent. 5,453,554 (1995))

Catalyst Diisopropyl benzene transalkylation

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

LINEAR ALKYL BENZENE

UOP Evolution of LAB processes; Becoming GREENER Benefits in product quality - use of solid acid Green Catalyst AlCl 3 HF Solid acid

Production of LAB Alkylation of benzene with C 11 – C 13 olefins

Heavy alkylates H 2 rich off gas Distillation N-paraffin recycle Paraffin Recovery Benzene Recovery Alkylation Solid-acid CATALYST Make up H 2 PACOL Dehydrogenation Pt/Al 2 O 3 Selective Hydrogenation DEFINE Fresh n-paraffin H 2 recycle Fresh benzene Benzene recycle LAB Linear alkyl benzene (LAB) using a solid-acid catalyst Detal process for Linear Alkyl Benzene production

Feed: mixed olefins (C 10 - C 13 ) Temp. (°C) = Press. = bars WHSV (h -1 ) = Conversion > 99.99%; product BI 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: (%) AlCl 3 – HClZSM-5Modified ZSM-5 Toluene conv Ethyltoluene Other aromatics Ethyltoluene: Para Meta Ortho

P-Diethylbenzene Product shape-selectivity in a zeolite NCL Process operated in a commercial scale (500 tpa)

Alkylation of naphthalene  2,6-dicarboxy naphthalene is a valuable monomer for the synthesis of PEN polymers  This can be produced from the oxidation of alkyl naphthalenes  Direct alkyklation yields ten isomers that are difficult to separate  Indirect routes have, therefore, been adopted for their synthesis

BP-Amoco route for synthesis of 2,6-dimethylnaphthalene [Lillwitz, Appl. Catal. A 231 (2001) 337]

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 ? FAU MOR BEA 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

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  Three monoalkyl and six dialkyl biphenyls are possible

Reaction conditions: Temp.= 250 o C; C 3 = 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 types Typical examples: Pt-ZSM-5, Pt-mordenite & Pt-(silica)-alumina

Xylene isomerization Catalyst: ZSM-5, Mordenite; MAPO; SiO 2 -Al 2 O 3 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, °C) Reforming (Pt-Re-Sn/ Alumina ) Fraction- ation Xylene iso- merizatrion (Pt-ZSM-5; Pt-Mord.; Pt-MAPO) Fraction- ation Arom. Extraction Transalkylation Pt/Mordenite Mol. Sieve Separation (PAREX) Benzene Toluene Xylenes + EB C 9 +Arom. Disproportionation Pt/Mordenite Naphtha o-Xylene p-Xylene m- + EB Raffinate Production of xylenes

Catalyst Toluene disproportionation C 9 + aromatics transalkylation Catalyst Disproportionation and transalkylation reactions

Catalytic reforming for aromatics production Desired reactions in Catalytic reforming  60-90°C cut for benzene  °C cut for toluene  °C for xylenes The reactions are:

Selective oxidation reactions  Current method is the oxidation of cyclohexanol with HNO 3 producing N 2 O  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

Current process for adipic acid

Enviro-friendly routes for adipic acid 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: CH 4  H 2 + CO  CH 3 OH (+CO)  CH 3 COOH -- (1) C 2 H 6  C 2 H (2) C 2 H 4 + CH 3 COOH  CH 2 CHOCOCH 3 (VA) (3) Direct vapour-phase catalytic oxidation of ethane to HOAc and ethylene and vinyl acetate: C 2 H 6  CH 3 COOH + C 2 H 4  CH 2 CHOCOCH 3 SABIC - Avoiding multi-step processes - Alterante cheaper raw materials Oxidation of alkanes

Use of alternate raw materials selective 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)

Phenol production

TS-1 MFI Sumitomo Production of Caprolactam w.o. (NH 4 ) 2 SO 4 co-production - Less polluting - Less number of steps - Benign reagents

Environmentally safe route to polycarbonate Conventional routes to polycarbonate

PC prepolymer (n=10~20) The green Asahi-Kasei Polycarbonate process O