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Introduction to Fischer Tropsch Synthesis Rui Xu Department of Chemical Engineering Auburn University Jan 29 th, 2013 CHEN 4470 Process Design Practice.

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Presentation on theme: "Introduction to Fischer Tropsch Synthesis Rui Xu Department of Chemical Engineering Auburn University Jan 29 th, 2013 CHEN 4470 Process Design Practice."— Presentation transcript:

1 Introduction to Fischer Tropsch Synthesis Rui Xu Department of Chemical Engineering Auburn University Jan 29 th, 2013 CHEN 4470 Process Design Practice

2 CHEN 4470 Process Design Practice Coal Biomass Natural Gas Fuel & Chemicals Gasification Syngas Processing Fischer- Tropsch Synthesis Syncrude Refining & Upgrading X L G XTL Technology

3 CHEN 4470 Process Design Practice Natural Gas Gasification Steam Reforming CH 4 + H 2 O CO + 3H 2 (Ni Catalyst) H 2 /CO = 3 Endothermic Favored for small scale operations Partial Oxidation CH 4 + ½O 2 CO + 2H 2 H 2 /CO 1.70 Exothermic Favored for large scale applications Autothermal Reforming A combination of Steam Reforming and Partial Oxidation

4 CHEN 4470 Process Design Practice Coal Gasification H/C Ratio Produces Leaner Syngas (Lower H 2 :CO Ratio) Ash Non-flammable material in coal complicates Gasifier design Impurities (Sulfur) Necessitates greater syngas cleanup 2(-CH-) + O 2 2CO + H 2

5 CHEN 4470 Process Design Practice Biomass Gasification H/C Ratio Similar issues to coal Ash Biomass aggressively forms ash Impurities ( Sulfur, Nitrogen) Necessitates greater syngas cleanup Moisture High moisture levels lower energy efficiency Size Reduction The fibrous nature of biomass makes size reduction difficult 2(-CH-) + O 2 2CO + H 2

6 CHEN 4470 Process Design Practice Syngas Processing Water Gas Shift Reaction CO + H 2 O CO 2 + H 2 Purification Particulates Sulfur (<1 ppm) - ZnO Sorbent Nitrogenates (comparable to Sulfur compounds) BTX (Below dew point)

7 CHEN 4470 Process Design Practice GTL Technology and Syngas Processing

8 CHEN 4470 Process Design Practice Fischer Tropsch Synthesis Introduction and History Reactions and Products Catalysts and Reactors Mechanism and ASF plot Economy

9 CHEN 4470 Process Design Practice Fischer Tropsch Synthesis Kaiser Wilhelm Institute, Mülheim, Ruhr 1920s Coal derived gases Aim to product hydrocarbons Commercialized in 1930s Franz Fischer Hans Tropsch

10 CHEN 4470 Process Design Practice FTS Industrial History Germany 1923, Franz Fischer and Hans Tropsch 1934, first commercial FT plant 1938, 8,000 barrels per day (BPD) U.S.A 1950, Brownsville, 5,000 BPD South Africa 1955, Sasol One, 3,000 BPD 1980, 1982, Sasol Two and Sasol Three, 25,000 BPD Malaysia and Qatar 1993, Shell, Bintulu, 12,500 BPD 2007, Sasol, Oryx GTL, 35,000 BPD China, Nigeria etc.

11 CHEN 4470 Process Design Practice Fischer Tropsch Synthesis CO + 2H 2 (CH 2 ) + H 2 O

12 CHEN 4470 Process Design Practice Fischer Tropsch Synthesis Introduction and History Reactions and Products Catalysts and Reactors Mechanism and ASF plot Economy

13 CHEN 4470 Process Design Practice Reactions in FTS

14 CHEN 4470 Process Design Practice Standard LTFT product distribution

15 CHEN 4470 Process Design Practice Fischer-Tropsch Products Hydrocarbons Types Olefins High chemical value Can be oligomerized to heavier fuels Paraffins High cetane index Crack cleanly Oxgenates Branched compound (primarily mono-methyl branching) Aromatics (HTFT)

16 CHEN 4470 Process Design Practice Fischer Tropsch Synthesis Introduction and History Reactions and Products Catalysts and Reactors Mechanism and ASF plot Economy

17 CHEN 4470 Process Design Practice Crushed in a ball mill Fischer-Tropsch Catalysts Fused Iron Catalysts – HTFT Alkali promotion needed Products are high olefinic Cheapest Reactor: Fluidized bed Iron oxide K2OK2O MgO or Al 2 O °C Air Molten Magnetite (Fe 3 O 4 ) Cooled rapidly Fused Iron

18 CHEN 4470 Process Design Practice Fischer-Tropsch Catalysts Precipitated iron catalysts - LTFT Co-precipitation method Alkali promotion is also important Cost more than fused iron catalyst Reactor: slurry phase or fixed bed pH = 7 Na 2 CO 3 Fe(NO 3 ) 3 WashingDryingCalcination Precipitate Iron Cat. K 2 CO 3

19 CHEN 4470 Process Design Practice Fischer-Tropsch Catalysts Supported cobalt catalysts - LTFT Incipient wetness impregnation method Oxide support: silica, alumina, titania or zinc oxide Products: predominantly paraffins Low resistance towards contaminants SupportDryingCalcination Supported Co Cat. Co(NO 3 ) 2

20 CHEN 4470 Process Design Practice Comparison of Co and Fe LTFTS Catalyst

21 CHEN 4470 Process Design Practice FTS Reactors

22 CHEN 4470 Process Design Practice FTS Reactors

23 CHEN 4470 Process Design Practice LTFT Reactors CO + H 2 (CH 2 ) + H 2 O kJ / mol 1800 o C Adiabatic Temperature Rise Fixed Bed (Gas Phase Reaction Media) – Shell SMDS – Excellent reactant transport – Simple design – Poor product extraction, heat dissipation – Limited scale-up – Potential for thermal runaway Slurry Bed (Liquid Phase Reaction Media) – Sasol SPR – Thermal uniformity – Excellent product extraction – Excellent economies of scale – Requires separation of wax (media) from catalyst – High development cost

24 CHEN 4470 Process Design Practice Fischer Tropsch Synthesis Introduction and History Reactions and Products Catalysts and Reactors Mechanism and ASF plot Economy

25 CHEN 4470 Process Design Practice Reactant adsorption Chain initiation Chain growth Chain termination Product desorption Readsorption and further reaction FTS Polymerization Process Steps

26 CHEN 4470 Process Design Practice Reactant adsorption Chain initiation Chain growth Chain termination Product desorption Readsorption and further reaction FTS Polymerization process steps

27 CHEN 4470 Process Design Practice FTS Mechanisms Alkyl mechanism Alkenyl mechanism CO insertion Enol mechanism FTS Polymerization Process Steps

28 CHEN 4470 Process Design Practice FTS Mechanisms The Alkyl mechanism 1i). CO chemisorbs dissociatively 1ii). C hydrogenates to CH, CH 2, and CH 3 2). The chain initiator is CH 3 and the chain propagator is CH 2 3i). Chain termination to alkane is by α-hydrogenation 3ii). Chain termination to alkene is by β-dehydrogenation

29 CHEN 4470 Process Design Practice FTS Mechanisms – The Alkenyl Mechanism 1i). CO chemisorbs dissociatively 1ii). C hydrogenates to CH, CH 2 1iii). CH and CH 2 react to form CHCH 2 2i). Chain initiator is CHCH 2 and chain propagator is CH 2 2ii). The olefin in the intermediate shifts from the 2 position to the 1 position 3). Chain terminates to alkene is by α-hydrogenation

30 CHEN 4470 Process Design Practice FTS Mechanisms – The CO Insertion Mechanism 1i). CO chemisorbs non-dissociatively 1ii). CO hydrogenates to CH 2 (OH) 1iii). CH 2 (OH) hydrogenates and eliminates water, forming CH 3 2i). Chain initiator is CH 3, and propagator is CO 2ii). Chain propagation produces RC=O 2iii). RC=O hydrogenates to CHR(OH) 2iv). CHR(OH) hydrogenates and eliminates water, forming CH 2 R 3i). CH 2 CH 3 R terminates to alkane by α-hydrogenation 3ii). CH 2 CH 3 R terminates to alkene by β-dehydrogenation 3iii). CHR(OH) terminates to aldehyde by dehydrogenation 3iv). CHR(OH) terminates to alcohol by hydrogenation

31 CHEN 4470 Process Design Practice FTS Mechanisms – The Enol Mechanism 1i). CO chemisorbs non-dissociatively 1ii). CO hydrogenates to CH(OH) and CH 2 (OH) 2i). Chain initiator is CH(OH) and chain propagator is CH(OH) and CH 2 (OH) 2ii). Chain propagation is by dehydration and hydrogenation to CR(OH) 3i). chain termination to aldehyde is by desorption 3ii). Chain termination to alkane, alkene, and alcohol, is by hydrogenation

32 CHEN 4470 Process Design Practice FTS Mechanisms - ASF Plot Propagation is exclusively by the addition of one monomer α i + i = 1 (by definition) Propagation probability is independent of carbon number

33 CHEN 4470 Process Design Practice FTS Mechanisms - ASF Plot

34 CHEN 4470 Process Design Practice Standard FTS Product Distribution

35 CHEN 4470 Process Design Practice FTS Kinetics

36 CHEN 4470 Process Design Practice Fischer Tropsch Synthesis Introduction and History Reactions and Products Catalysts and Reactors Mechanism and ASF plot Economy

37 CHEN 4470 Process Design Practice FTS Economics Overall Cost Capital Cost 50% to 65% of total production cost is due to capital cost $10 per BBL for Natural Gas feedstock, $20 per BBL for Coal or Biomass feedstock Operating Cost 20% to 25% of total production cost is due to operating costs $5 per BBL for Natural Gas, $10 per BBL for Coal or Biomass Raw Material Cost Waste or stranded resources are preferred At market value ($4.50 / MMBTU), natural gas costs $45 / BBL At market value ($70 / ton), coal costs $35 / BBL At market value ($30 / ton), biomass costs $30 / BBL

38 CHEN 4470 Process Design Practice XTL technology Economy Cost Distribution NTL case 1: 25% for the gas, 25% for the operations and 50% for the capital NTL case 2: 15% for the gas, 21% for the operations and 64% for the capital (28% reforming, 24% FTS system, 23% oxygen plant, 13% product enhancement and 12% power recovery) BTL capital (21% for biomass treatment, 18% for gasifier, 18% for syngas cleaning, 15% for oxygen plant, 1% for water-gas-shift (WGS, CO + H 2 O CO 2 + H 2 ) reaction, 6% for FTS system, 7% for gas turbine, 11% for heat recovery / steam generation, 4% for other) Recycle, power and heat integration CO 2 transport and storage

39 CHEN 4470 Process Design Practice Syncrude Upgrading Extraction and Purification Terminal Olefins, Oxygenates, and FT Wax have high value Hydrocracking Converts wax into liquid fuels Oligomerization Converts light olefins to liquid fuels Other Reactions Alkylation, Isomerization, Aromatization, etc. Polymerization HTFT ethylene and propylene can be made into polymers Hydrogenation Promoted fuel stability

40 CHEN 4470 Process Design Practice Reference Book: Fischer Tropsch Technology Review Articles: The Fischer-Tropsch process (Dry, 2002) High quality diesel via the Fischer–Tropsch process – a review (Dry, 2001) Kinetics and Selectivity of the Fischer–Tropsch Synthesis: A Literature Review (Gerard, 1999) Design, synthesis, and use of cobalt-based Fischer-Tropsch synthesis catalysts (Iglesia, 1997)

41 CHEN 4470 Process Design Practice


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