Petrochemicals & Processing Technology Heterogeneous Heterogeneou s catalysis Mark Saeys Room E5-03-12 Email:
[email protected]
Heterogeneous catalysis
CPT Chapter CPT Chapter 9 Ullmann : Ethylbenzene, styrene, phenol, ethylene Ullmann : oxide, ethylene glycol, propylene oxide, maleic and fumaric acids, ... Farrauto and Bartholomew: Bartholomew: Fundamentals of Industrial Catalytic Processes, Chapter 7
Acetic acid: homogeneous catalysis VAM: vinyl acetate monomer X PVOH: poly vinyl alcohol EPR, EBR: ethene propene rubber rubber,, ethene-butadiene rubber PU: polyurethane EO, EG: ethene oxide, ethene glycol X SM/PO: styrene, propene oxide X PG: poly-glycol PS, EPS: polystyrene, expanded PS
Xylenol: 1,3-dimethyl phenol PPE: poly phenylether phenylether,, PTBP: para-t-butyl phenol Acrylic acid SAP: superabsorbent polymers NPG: neopentyl glycol m-MMA: methylmethacrylate X INA: iso-nonane alcohol MBS: MMA-Styrene-butadi MMA-Styrene-butadiene ene
Impact of Heterogeneous catalysis Annual Catalyst Market: Catalyst cost (% of product value): Products via catalysis:
US$ 8 billion 0.2 % US$ 2 Trillion/year
Potential improvements:
Ethylene Oxide Terephthalic Acid Acrylonitrile Adipic Acid and Caprolactam Propylene Oxide Vinyl Acetate
Courtesy of
Assumed Selectivity Improvement 9% 2% 18% 7% 3% 12%
Global Annual Feed Stock Savings 365 35 390 215 300 70 1375 Million US $
Catalyst Performance: Paul Weisz Moles product per cm 3 reactor per second 10-14
10-12
Petroleum geochemistry
10-10
10-8
Biochemical processes
Technology
Description
Ethylbenzene
Aromatic Alkylation
Styrene
Dehydrogenation
Maleic Anhydride Isomerization
Oxidation Paraffin/Isomerization
Catofin
Paraffin Dehydrogenation
LC-Fining
Resid Hydrocracking
10-6
10-4
Industrial Catalysis
Space-Time-Yield gmol/second cm3 6.8 x 10-7 6.9 x 10-7 2.1 x 10-7 7.0 x 10-6 9.7 x 10-7 1.2 x 10-7
Styrene Styrene: 30 Mt/y, consumes more than 50% of benzene Found in: CD cases, yoghurt containers, insulation, ... Expanded PS foam (EPS) Acrylonitrile-butadiene-styrene (ABS) Styrene-butadiene rubber (SBR) Styrene-acrylonitrile (SAN) Production: 1. Alkylation of benzene with ethene using acid catalyst.
Catalyst: Lewis acids: AlCl 3 (Friedel-Crafts) – no more new plants Zeolites: ZSM-5 or MCM-22
Styrene 2. Dehydrogenation of ethylbenzene – 85%
Catalyst: K promoted Fe 2O3 Alternative: Oxidation route: coproduct of propylene oxide Oxidize EB to peroxide and react with propylene (Seraya, Singapore)
Alkylation to Ethylbenzene Side reactions: 1. Further alkylations 2. Oligomerization of ethene 3. Isomerization Recycle DEB and transalkylation DEB + B -> EB Alkylation: low T, high p Transalkylation: independent of T, p Excess benzene for selectivity to EB: B/E = 2-16
Ethylbenzene - Original AlCl3 process (Monsanto-Lummus)
Characteristics: Homogeneous catalysis, ethylchloride: promotor, Dry benzene (avoid corrosion) Process: 1. Liquid phase alkylator (B/E~2-3), 2. Transalkylator: Unreacted B and recycled DEB; 3. NaOH to neutralize Cl-; 4. Cat recovery is challenging (settlers)
Zeolites-shape selectivity Pore size of zeolites as compared to dimensions of some molecules EthylBenzene (EB) fits in ZSM-5, poly-EB (PEB) doesn’t
FCC: catalyst
Requirements: Strong acid, stable, can be regenerated O H O
Si
O
O
O
Al O
Zeolites SiO2 framework. Some Si are substituted by Al -> acid sites Crystalline, stable and porous material
Ethylbenzene - Zeolite vapor phase process (Mobil-Badger)
Heterogeneous catalytic (ZSM-5), gas phase process B/ E~8-15 (to reduce coking) – expensive B separation No benzene drying T=350 to 450°C, p=10-30 bar DEB goes to (small) transalkylator Exothermic – cooling by quench
EB dehydrogenation to Styrene Reaction: similar to steam cracking
Thermo: high T, low p, high steam dilution ( coking) 12-17 mol/mol Unlike SC, catalytic process to avoid side reactions Cat: Fe2O3 (K, Cr 2O3) Conditions: 600-650 °C pEB = 0.1 bar Selectivity: 90% Conversion: 50-70%
EB dehydrogenation to Styrene
Fixed bed reactor: adiabatic or isothermal multi-tubular
Difficult separation: Low T to avoid polymerization Vacuum distilation (special column) Polymerization inhibitor
Selective catalytic oxidation
Examples of selective catalytic oxidations Ethylene to ethylene oxide (EO) Ethylene to acetaldehyde (homogeneous catalysis) Propylene to propylene oxide (PO) Propene to acrylonitrile (AN, ammoxidation) Propene to acrylic acid (AA) i-butene to methyl methacrylate (MMA) Butane/butene to maleic anhydride (MA) Naphthalene or o-xylene to phthalic anhydride (PA) Benzene to phenol (selective oxidation not yet industrial) Methanol to formaldehyde (oxidative dehydrogenation)
Ethylene oxide
O
Production: Selective catalytic oxidation of ethylene, smallest epoxide Third largest consumer of ethylene (13%), 15 Mt/y (99) behind PE and PVC
Use: intermediate for glycol, polyesters (PET) and ethanolamines Two processes for epoxides: 1. Chlorohydrin process (old) 2. Selective oxidation
Ethylene oxide - chemistry
Overall reaction
1. Chlorohydrin process:
Chlorinated byproducts, CaCl 2 = “waste”
Ethylene oxide - chemistry 2. Selective catalytic oxidation:
Ea,1 < Ea,2 Hr,2| >>
Hr,1|
T-control crucial!
Path 1: desired Path 2 & 3: total combustion – lower yield Ag only catalyst with high selectivity (>90%) for selective oxidation of ethylene
Ethylene oxide-catalyst Silver deposited on porous support ( -Al2O3). Support is inert and has low surface area No hydroxyl groups: avoid isomerization to acetaldehyde Finely devided Ag particles (0.1-1 m) 0.05 wt% promotors (Cs, Rb) Promotor (Cl- ) added to feed
Ethylene oxide-process
Selective oxidation: T and selectivity control crucial Below explosion region: 7% oxygen, 20-40 % ethene Multi-tubular reactor – many small diameter tubes (2-5 cm) Inerts to control T Ethylene conversion/pass: 8-11 % - recycle Absorb EO (1-2 mol% in exit stream) in water (stripper) Side stream to CO2 absorption to prevent build-up
Ethylene oxide-process options
Air or pure oxygen?
Air : more purge, higher conversion, less selective Oxygen: CO2 absorption required
Ethylene glycol 60% of EO is converted to ethylene glycol (hydrolysis) HO O
+ H2O OH
Process: Non-catalytic, 200°C Excess H2O (20-fold) for selectivity Use: anti-freeze (50%) polyesters (PET) (40%)
Propylene oxide O
H3C
Production: 6 Mt/y (06) Singapore: Seraya Processes: 1. Chlorohydrin (50%) 2. Indirect oxidation with peroxides No successful direct selective oxidation
Propylene oxide-chlorohydrin process 1. Chlorohydrin route Cl2 + H2O -> HOCl + HCl CH3-CH=CH2 + HOCl -> CH 3-CH(OH)-CH2(Cl) 2. Dehydrochlorination of propylene chlorohydrin (PCH)
CaCl2 : waste! (DOW) Selectivity: 90-95 % Side reactions: Chlorinated products (dichloropropane)
Propylene oxide-indirect oxidation BASF-Shell Seraya Elba Eastern plant: 550 kt/y styrene (SM) and 250 kt/y propylene oxide (PO) 1. EB with air -> 12-14% EB hydroperoxide Byproducts -methyl benzyl alcohol acetophenone 2. “Catalytic” epoxidation Cat: homogeneous (Molybdate) heterogeneous (Ti-silicalite) Selectivity: 70-85% to PO
Propylene oxide-SM PO process
1
2
3
1. EB oxidation: 12-14% conversion; 2. propylene epoxidation. Unreacted propylene is recycled; 3. Dehydration of -phenylethanol over Al 2O3
Acrylonitrile H2C
CN
Production: 5.5 Mt/y (98) Use: Acrylic fibers (50%), ABS, SAN (30%), adiponitrile for nylon (10%)
Early processes from C2: EO + HCN HOCH2CH2CN H2C=CHCN CH!CH + HCN H2C=CHCN !
!
!
Modern process from C3 : ammoxidation of propene (SOHIO)
Acrylonitrile-Sohio process
1960: Standard Oil of Ohio (later BP) – 90 % of world capacity Mechanism: complex! Oxidative dehydrogenation Mars-van Krevelen NH addition Also total oxidation Very exothermic
Cat: Bi2O3.MoO3 in fluidised bed – T control
Acrylonitrile – catalyst High-resolution STEM image of a promising acrylonitrile and acrolein catalyst, MoVNbTeO. (Buttrey et al., JPCC 2008)
Acrylonitrile-Sohio process
Very exothermic: -760 kJ/mol (also some total oxidation) Fluidized bed, 420 to 450°C and added steam for T control Excess of air, stoichiometric NH 3 and propene. 80% conversion, 70-80% selectivity. No recycle Byproduct: HCN and CH CN (acetonitrile)
Acrylic acid H2C
O
Production: 2.9 Mt/y (99), large growth Use: coatings (paint), textiles, fibers, adhesives, superadsorbents,...
OH
Old processes: 1. Reppe: NiBr 2 (CuBr 2 promoted) – homogeneous cat
2. Acrylonitrile hydrolysis: H2C=CHCN + H 2SO4 + H2O
Byproduct (NH4HSO4)
New process: 3. Selective catalytic oxidation of propene CH2=CHCH3 + O2-> CH2=CHCHO (acrolein) + H2O CH2=CHCHO + " O2-> CH2=CHCOOH
Bi/Mo Mo/V
Acrylic acid-process
First step: propene oxidation with air (steam) to acrolein and some acrylic acid Multi-tubular reactor, 350°C, 2 bar Second step: acrolein oxidation to acrylic acid ~280°C Overall conversion: 90%, selectivity: 75-80% (based on propene)
Methyl methacrylate H3C
O
H2C
O
Production: 2.4 Mta (99) Use: polymers (Plexiglas) CH3
Processes: 1. Acetone cyanohydrin (ACH) route (80%) Base catalyzed, 40 °C High selectivity 2 steps: 1. Concentrated H 2SO4 80 to 140 °C 2. + Methanol
Acetone and HCN are byproducts: cheap
Methyl methacrylate Cyanohydrins: chemistry
Recycle ammonium bisulfate
Methyl methacrylate-from acetone
Second step and separation a: hydrolysis of CN group, 80-140°C, 98% H 2SO4 d: esterification with CH 3OH e: phase separator: organic (MMA) and H 2O/CH3OH/NH4HSO4 h: wash to recover CH 3OH and methacrylic acid (byprod) 1.6 kg H2SO4 consumption/kg MMA
Methyl methacrylate-from i-butene Process: 2. Two-step isobutene oxidation and esterification
1.
2.
t-butanol oxidation Mo/Bi/Fe/Ni oxides
Methacrolein oxidation Mo/P/Sb oxides Overall conversion 90%, selectivity >95%
3. CH2=C(CH3)-COOH + CH3OH -> MMA + H2O
Methyl methacrylate-from i-butene
Sumitomo (cf. acrylic acid from propene) a: oxidation reactors. a1: Bi/Mo oxide 420°C, S ~95 % a2: hetero poly acid b: quencher; c-e: unreacted methacrolein recycled f-h: methacrylic acid separation i: methacrylic acid esterification with methanol
Methyl methacrylate-economics MMA: ACH process vs. i-butene oxidation
BASF ethylene process – 20 to 40% cheaper than ACH
Maleic Anhydride O
O
Production : 1.4 Mt/y (99) Use: polyesters (50-60%), paints Processes: 1. Selective oxidation of benzene (20% in 2000)
O
2. Selective oxidation of C 4 (mostly butane)
3. Byproduct in other selective oxidations
Maleic Anhydride-Benzene oxidation
H2O
Multi tubular reactor – salt bath cooler – T control Catalyst: V2O5, Mars-van Krevelen mechanism Conditions: 400°C, 2-5 bar, short residence time (~0.1 s) Low selectivity (~65%), conversion ~90% Partial condensation (c) and Wash with water (d,e) – leads to maleic acid
Maleic Anhydride – Butane oxidation Mechanism: both butene and butane – from steam cracker
Catalyst: promoted V2O5 – both V4+ and V5+ Mars-Van Krevelen mechanism: butane reacts with latice oxygen from catalyst, not from air Reactor (Dupont): riser: butane oxidation regenerator: cat reoxidation, fluidized bed Selectivity: 70-80%, Conversion: 40% No O2-hydrocarbon mixtures Catalyst concern: attrition
Phenol OH
Production: 7.3 Mt/y (03) Second largest benzene consumer (20%) Use: bis-phenol A (polycarbonates) (37%), phenolic resins, (caprolactam (nylon 6))
Processes: Direct selective oxidation – under development Indirect: 1. Benzenesulfonic acid (oldest, no longer used) 2. Oxychlorination to chlorobenzene – still used 3. Toluene oxidation to benzoic acid 4. Cyclohexane oxidation to cyclohexanol 5. Benzene + propene -> cumene (Hock process) Cumene + O 2 -> phenol and acetone 95% of world capacity
Phenol-Hock process
1. Alkylation Similar to EB, but easier Cat: Friedel-Crafts or zeolites
2. Oxidation 1. Oxidation of cumene to cumene hydroperoxide (CHP) 2. Cleave CHP in acid medium (H2SO4) Both reactions exothermic, byproducts
Phenol-Hock process
Autocatalytic oxidation of cumene in bubble towers (R 1, R2) X1- X3: condensers to recycle cumene VC: vacuum distillation to increase CHP concentration Cleavage in series of heat exchangers (R3-R5) Neutralize product (Na-phenolate)
Phenol-new process
Fe-ZSM-5 catalyst, N 2O: byprod from adipidic acid
Bis-phenol A CH3 HO
OH CH3
Production : 2.7 Mt/y (03) Use: polycarbonates, high quality plastics and epoxy resins
Polycarbonates (1.5 Mt/y (02)): Reaction of BPA with COCl 2 or “(CH3O)2CO”
Process: Acid catalyst (HCl or ion exchangers)
Bis-phenol A – bit of chemistry Acid catalyzed electrophilic aromatic substitution Separation problem -> crystallization
Polycarbonates: avoiding COCl2 Equilibrium not as favorable as with COCl 2 Shift equilibrium: polymerization under vacuum and high T
Economics: Economics: Cash cost same Higher finance costs, because phosgene plant is more expensive (safety!)
Vinyl acetate O
H3C
O
CH2
Production: 4.3 Mt/y Production: Use:: PVA (paints); PVOH Use (adhesives/fibers)
Processes : 2 old processes Processes : 1. HC!CH + CH3COOH (acetylene) 20% of capacity decreasing
2. CH3CHO + (CH3CO)2O (acetaldehyde)
New:: 3. H2C=CH2 + CH3COOH + " O2 (e New (ethylene)
80%
Vinyl acetate – new process New process – process – ethylene based
Mechanism: C2H4 + 2* # H* + C2H3* CH3COOH + 3* # CH3COO** + H* " O2 + * # O* C2H3* + CH3COO** # VA +3* 2H* + O* # H2O + 3* Catalyst: Au modified Pd
Vinyl acetate-process
Heterogeneous catalytic process, Pd/Au Recycle gas stream (ethylene) is saturated with AA and mixed with oxygen (<8% - flammability), Multitubular reactor Conversion: E: 8-10%; AA: 15-35%, O 2: 90% l, e, m – remove 40-50% of the water (m: phase separation) f: recycle washing; h, i, j: purge and manage CO in recycle
Vinyl Chloride H2C Cl
Production : 31.1 Mt/y (00) Use: PVC
Process: Step 1. Ethylene + Cl 2 -> Ethylenedichloride (EDC) a. Direct Chlorination. Liq phase. cat: e.g. FeCl 3
b. Oxychlorination. Heterogeneous cat: CuCl 2 Mars-van Krevelen mechanism, very exothermic C2H4 + 0.5 O2 + 2 HCl -> CH 2Cl CH2Cl + H2O Hr =-240 kJ/mol
Vinyl Chloride Oxychlorination catalytic cycle
Vinyl Chloride Step 2. EDC dehydrochlorination via thermal cracking T: 500-600 °C, p: 25-30 bar (compare steam cracking) 50-60% conversion, S~98% PFR, 1000 m long
Combine 1a, 1b and 2 to minimize Cl 2 consumption Oxy-EDC
Vinyl Chloride
Schematically:
Balance on HCl
Vinyl Chloride-Direct Chlorination Liquid phase, FeCl 3 cat T: 100 °C Exothermic reaction Heat of reaction used to distillate EDC EDC from oxychlorination added and purified Cat recovery challenging (absorption process)
Vinyl Chloride-Oxychlorination
Multi tubular reactor : exothermic reaction Catalyst: CuCl2 on Al2O3 support Quench in d and cooling in heat exchanger e Wash with NaOH (h) Bottom of (i) to Oxy-DC for further purification
Vinyl Chloride-EDC cracking
EDC cracking furnace (a); quench (b, c) Separation (d, e). NaOH to remove residual HCl Mechanism: 1) ClCH2 – CH2Cl
!
2) Cl ! + ClCH2 – CH2Cl
!
3) ClCH2 – C!HCl
!
Cl ! + ClCH2 – CH2Cl
ClCH2 – C!H2 + Cl !
ClCH2 – C!HCl + HCl CH2 = CHCl + Cl ! ClCH2 – C!HCl + HCl
!
etc.
Course overview 1. Raw materials/ Fuels/ Base chemicals/ Intermediates/ speciality chemicals/ consumer products / bulk chemicals Raw material vs. Energy source – have idea about oil reserves, usage in petrochemical industry, alternatives, green house problem Refining Different processes: distillation, FCC, HDS, HC, CR, alkylation, flexicoking,... Objectives, main reactions, cat, reactor, process scheme (not too detailed), process conditions (from thermo) Idea of different cuts (naphtha, gasoline, gas oil, vacuum gasoil, kerosene) Octane/cetane number Refinery types (have an idea of the different components – why they are there) and future challenges
Syngas production and use Steam reforming: process, cat, conditions, reactor/furnace, main reactions, thermo, deactivation, different steps in process, autocatalytic, partial oxidation, shift reactions,... Coal gasification: main reactions Ammonia, methanol: use, production, reactions, thermo, kinetics, catalyst, process conditions, maximum rate curve, reactor concepts, process, kinetics and selectivity (methanol) Fischer-Tropsch: objective, reaction(s), Schulz-Flory, reactor design
Steam Cracking Process, feed and product, process conditionsrequirements Thermo/kinetics, severity/conversion (influence on product distribution) Process, Furnace (sections, heat flux...), reactor Coke formation and solutions Separation (block diagram – not exact T/p’s – concept) Cooling circuit - principle Idea of alternative processes (dehydro, MTO) Polymerization Chain-growth (Rad. and coord. mechanism), step-growth Derive MWD for step-growth, radical and coordination poly and relation to process conditions Different processes: what are the differences, challenges in process design, cat/initiator, idea of process conditions, types of PE
Heterogeneous catalysis EB and Styrene : thermo, processes (concept – recycle), process conditions (E/B,..), catalyst development Selective catalytic oxidation EO: process routes (SCO and chlorohydrin), cat, process (tubular reactor (why?), excess ethylene – recycle) PO: the chlorohydrin and co-production processes, reactions, process steps AN: ammoxidation: reactions, cat, idea of process (reactor type)-byproducts Acrylic acid: SCO propene (chemistry, cat, reactor) MMA: reactants, chemistry (ACH and i-butene oxidation, economics) MA, PA: process, mechanism, reactor choice, catalyst, selectivity issues Phenol:
