Transcript
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
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