Hydrogen from Renewable Fuels by Autothermal Reforming: Alcohols, Carbohydrates, and Biodiesel

Transcription

1 Hydrogen from Renewable Fuels by Autothermal Reforming: Alcohols, Carbohydrates, and Biodiesel Lanny D. Schmidt Department of Chemical Engineering and Materials Science University of Minnesota Minneapolis MN

2 Steam reforming Producing Hydrogen Fuel + H 2 O H 2 + CO Water Gas Shift CO + H 2 O CO 2 + H 2 95% of H 2 is made by this process Endothermic process Requires tube furnace Does not scale down Catalytic Partial Oxidation Fuel + O 2 H 2 + CO Need H 2 for large and small applications Gas to liquids refineries Fueling station Portable power

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4 Catalytic Partial Oxidation Heat Shields Reactants Quartz Tube Catalyst Converts hydrocarbons into valuable chemicals: syngas (H 2 & CO), olefins, oxygenates, etc. Exothermic process Runs auto- thermally Short contact times (Milliseconds) Vapor phase reactions Products

5 Hydrogen and Chemicals in Millisecond Reactors Hydrogen Economy Distributed power Fuel cells Pollution abatement Renewable energy Renewable chemicals

6 Reactions CH 4 H 2 + CO H 2 synfuels methanol hydrogen economy gasoline H 2 portable power diesel H 2 alcohols H 2 renewable energy carbohydrates H 2 biodiesel H 2 olefins renewable chemicals

7 Renewable Hydrogen Biomass Wastes Heat Syngas Hydrogen Methanol Dimethyl ether FT liquids Hydrolysis Sugar Fermentation catalyst Ethanol Propanol H 2 Glycerol Wind Electrolysis H 2 +O 2 Power Ammonia

8 fuel Fuel Injector air Reactor Heating Mixer Thermocouple Catalyst Insulation Thermocouple Products

9 Methane to Syngas Rh Catalyst, 5 SLPM Total Flow, no preheat Conversion/Selectivity Temperature CH 4 H 2 CO Temperature C C/O 650

10 Gasoline and Diesel to Syngas High boiling points, >300 o C Pyrolysis before vaporization Polycyclic aromatics Mixtures

11 Hexadecane Partial Oxidation 80 ppi α-al 2 O 3, ~3 wt% γ-al 2 O 3, ~3 wt% Rh

12 Reactor Tunability Syngas Ethylene α-olefins C/O ~ 1 ~ 1.3 ~ 2.0 S(%) ~ 85 ~ 36 ~ 60 Reactants 45 or 80 ppi α-al 2 O wt% γ-al 2 O 3 wash-coat ~1-5 wt% Rh Syngas Ethylene α-olefins

13 Steam Addition 80 ppi α-al 2 O 3 monolith ~4 wt% γ-al 2 O 3 washcoat ~2 wt% Rh 4 SLPM Steam to Carbon ratio of 1 -)#!"#$, )#)+#!"#$ )#* %&'$"$( )#$

14 Steam Addition / X. 0 S. / 1. /. / 80 ppi α-al 2 O 3, ~4 wt% γ-al 2 O 3, ~2 wt% Rh, 4 SLPM, S/C = 1

15 Catalysis Surface area not important all ~2 m 2 /g γ-al 2 O 3 converted to a after heating to 1000 o C metals form films 1 µm thick All conversions 100% mostly complete in first mm Selectivities dominate wash coat and small channels makes hydrogen no wash coat and large channels makes olefins

16 10% Rhodium Before and After Use

17 Spatial and Transient Analysis microcapillary Side hole sampling No void behind the capillary Minimal disruptions to the flow field Capillary can move in and out Spatial temporal profiles 80 ppi 45 ppi.05 sec, 0.3 mm resolution

18 Spatial Analysis: Experimental Results Catalyst: Rhodium Washcoat 80 ppi Methanation observed in simulations Repeatable

19 Transient Switch C/O

20 Spatial-temporal profiles monolith heat shield

21 Spatial-temporal profiles

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23 Hydrogen and Chemicals from Biomass biodiesel alcohols glycols glycerol sugar carbohydrates trees

24 Renewable Chemicals From Biodiesel Soy oil + CH 3 OH biodiesel + glycerol methyl linoleate 52% C-O-CH 3 O isomers with 1, 2, and 3 double bonds 2% in Minnesota diesel pool in 2005

25 Renewable Chemicals biodiesel H 2 80% olefins 90% ethylene, propylene 50%

26 2-Propanol 1-Propanol CH 3 CHOHCH 3 Autoignition : 399 C Boiling Point : 82 C Flammability Limits : % in air Ethanol CH 3 CH 2 OH Autoignition : 363 C Boiling Point : 78 C Flammability Limits: % in air CH 3 CH 2 CH 2 OH Autoignition : 371 C Boiling Point : 97 C Flammability Limits: % in air Methanol CH 3 OH Autoignition : 464 C Boiling Point : 65 C Flammability Limits: % in air

27 Fuel Conversion and Temperature X Methanol Ethanol 1-propanol propanol T X 70 2-propanol T( o C) Ethanol 1-propanol Methanol C/O C/O 2-propanol is least reactive Temperature increases with increase in chain length

28 Syngas propanol H Methanol CO 80 Ethanol 80 Ethanol S H Methanol 60 Sco 40 1-propanol 20 2-propanol 20 2-propanol C/O C/O Syngas production increases with increase in chain length Straight chain alcohols produce more syngas than 2- propanol

29 1-Propanol and 2-Propanol Products Partial Oxidation 2-Propanol Dehydration Dehydrogenation H 2 and CO C 3 H 6 C 2 H 4!

30 Energy Diagram for Ethanol C 6 H 12 O H 2 O 2 CO C 2 H 5 OH + 4 H 2 O H o = +20 G o = -210 H o= -140 G o = CO H 2 O 2 H o = G o = O 2 5 O 2 photosynthesis hν sugar fuel cell H o = G o = reformed ethanol fuel cell 6 CO H 2 O 6 CO H 2 O

31 Carbohydrates Methanol Boiling Point = 65 o C H-(CH 2 O)-H Ethylene Glycol Boiling Point = 195 o C H-(CH 2 O) 2 -H Glycerol Boiling Point = 290 o C H-(CH 2 O) 3 -H

32 Mechanism Surface ROH RO(s) H 2 + CO surface alkoxy makes syngas only C 1 species Homogeneous H. H 3 C - C- CH 3 H 3 C - C- CH 3 H 3 C - C- CH 3 OH OH O chemistry very selective no secondary products

33 Mechanism Reactants C 10 H 22 + O 2 Rh C 10 H 22 CO H 2 CO 2 H 2 O Oxidation zone surface chemistry hotter no carbon makes mostly C 1 products Products C 2 H 4 α olefins H 2 CO CO 2 H 2 O Pt Reforming zone no oxygen homogeneous chemistry contains carbon makes olefins

34 Why Does it Work? High flow velocities High T High T gradients Fastest reactions dominate Inhibit homogeneous reactions Successive reactions inhibited Inhibits carbon buildup Challenges mixtures sulfur modeling

35 Summary Higher alkanes can be converted to H 2 and olefins >80% H 2 >140% H 2 with steam added 80% olefins 50% ethylene and propylene Alcohols and carbohydrates can be converted to H 2 steam reforming and partial oxidation 4 H 2 per C 2 H 5 OH Biodiesel can be converted to olefins and olefinic esters 80% H 2 40% ethylene and propylene ester linkage preserved >20% olefinic esters