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Micro-Structured Monolithic-Catalyst Bed as C d Hi h Th h RCompact and High Throughput Reactor
System for Conversion of Syngas to Liquid F lFuels
Wei LiuWei LiuPacific Northwest National Lab
Richland, WA
Presentation at Technical Session of Syngas Production and Gas-to-LiquidsAIChE Annual MeetingAIChE Annual Meeting
Nov. 11th, 2010Salt Lake City, UT
Acknowledgment
Colleague at Pacific Northwest National Lab
Yong Wang, John Hu, Wayne Wilcox, Shari Li, David King
Thi k t d d l b t di t d h dThis work was supported under laboratory‐directed research and development (LDRD) program of PNNL by Energy Conversion Initiative and Energy & Environmental Directorate.
Pacific Northwest National Laboratory (PNNL) is operated by Battelle for the Department of Energy.
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Syngas Conversion Critical to Production of Chemicals or Liquid Fuels from Various Carbon Sources
Coal
Heavy oil, tar sand
Biomass
GasificationMethanol
Suitable H2/CO ratio
Wastes
N t l Steam-
Gas cleanup & conditioning
Catalytic conversion of
syngas (H2/CO)
Oxygenates
HydrocarbonsNatural gas
CO2 + H2O
Steamreforming
Hydrocarbons
Solar photochemical
FT reactionCO2 + H2O photochemical
electrochemicalthermochemical
FischerFischer--Tropsch type of Tropsch type of SynthesisSynthesis
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Catalysis chemistries studied extensively
Main reaction:
Highly exothermic and complex reaction paths
*222 )(2)( CHOHgHgCO
)(22 paraffinHC nn
+H2Chain growth
Main reaction: (H ~ -10 MJ/kg-product)
222 )()( gg)(2 olefinHC nn
CokeSide reaction: Coke
422 )(3)( CHOHgHgCO
222 )()( COHgOHgCO
Side reaction:
• Co-based catalysts for fixed beds
F b d t l t f l b d
4
• Fe-based catalysts for slurry beds
Step‐out reactor needed to overcome “scale‐economy” barrier for distributed gas‐to‐liquid conversion
• Current FT reactor commercialized for large-scale, integrated plants. Cost-prohibitive when processing capacities are one or two orders of magnitude smaller than refineries or petrochemical complexes.
• Most today’s needs of gas-to-liquid conversion are like distributed production at small capacity scales, coal gasification, biomass gasification, remote natural gases, solid wastes, other renewable energy sources.
Furnace Gas compressor Gas cleanup
P k d ll t b d
Conversion Cleanup & Catalytic Gas/liquid Liquid F d t k
Recycle of un-converted syngas gas and methane
Packed pellet beds or slurry reactor of catalyst fines
Conversion to syngas
Cleanup & conditioning
Catalytic reactor separator hydrocarbonFeedstock
5
Major portion of capital and operation costs is associated with the gas recycle system, beyond the reactor itself
Present objective: compact, high‐throughput, modular reactor unit
Recovery of residual gas as fuel gas
Planar heat exchanger-type reactor configuration:-- Hot zone is loaded with monolithic-structured catalyst bed
Cooling
Reaction
Conversion to syngas
Cleanup & conditioning
Novel catalytic
Gas/liquid separator
Liquid hydrocarbonFeedstock
g g
y g g yreactor
• Achieve nearly complete syngas conversion at one pass to dramatically simplify process flow diagram, and thus, capital and operation costs
Limitations of conventional reactors (packed or slurry beds):• CH4 selectivity is too high at deep CO conversion• Hydrodynamics, such as back mixing• Catalyst deactivation
6
A holistic approach toward catalyst & reactor design
Li & Kwauk “Exploring complex systems in chemical engineering – the multi-scale methodology”. Chem. Eng. Sci. 58 (2003) 521-535, a powerful approach to all catalytic reactor systems.
Address mass and heat transfer at
catalytic reactor systems.
• Reactor scale• Scale of individual reaction unit• Catalyst structure scale
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Reactor‐scale design to address heat management at macro‐scale
Catalyst structure insert1cm x 1m x 2m
Planar, heat-exchanger-type design: • Take away reaction heat by adjacent cooling 1cm x 1m x 2my y j g
streams
• Control temperature profiles by feed gas and cooling fluid distribution, flow rates, and heat gexchanging area
• Utilize existing reactor fabrication technologiesg
• Scale up by numbering up reactor modules
8 Cooling channel
Micro‐structured catalyst bed to address heat and mass transport at scale of individual reaction zone
Ceramic honeycomb as catalyst support structures• Structured catalyst bed comprises catalyst
coatings on a continuous inert support.S t t i id 3 D th l• Support matrix provides 3‐D thermal conduction network for rapid heat transfer from catalyst surfaces to the heat exchanging interface.g g
Cooling plateCooling plate
SyngasSyngas
9
Catalyst channel‐scale design to addresses gas/liquid/catalyst mass transport at reaction pointsBulk fluid
Channel surface
External surface of catalyst coating
Catalyst pore
H2OOilCH4
H2 (g)CO (g)
I IVIIIIICatalyst surface
St III &IV b ti i d b
surface catalyst coating p CH4CO (g)
H2OOilCH4
SyngasT l flDi d b bbl fl
Steps I & II can be controlled by channel geometries (size, shape) and flow conditions (Ul, Ug)
Steps III &IV can be optimized by thickness and pore structures of the catalyst coating layer
CH4
Inert support
Catalyst layerLiquid film
Sy gasTaylor flowMist flow
Dispersed bubble flow
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Experimental testing of key design principlesExperimental testing of key design principles
FT catalyst coating on ceramic monolith substrate of 1mm channel size
Coated catalyst channel
Coating texture of channel surface
Cross-sectional view of coating
channel
Al Si Co La Re
76.7% 2.5% 19.0% 0.8% 1.0% Al Si Co La Re
CompositionComposition
67.7% 1.4% 28.6% 1.1% 1.3%
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Reaction testing in a ½” OD stainless steel tube sheathed with silicone oil heat‐exchanging fluid
Thermocouple
Feed gas
All channels are open after 45-
day testing
Monolithic-
Feed gasday testing
Monolithic-structured bed
Af iSilicone oil
• After reaction was quenched, existence of wax was found in all channels on bottom of thechannels on bottom of thebed
Suggest uniform reaction among all channels
13
g
Steady‐state performance of monolithic‐structured catalyst bed (25 bar, 210oC)
Nearly complete H2 or CO conversion at base WHSV at CH4 selectivity <10 wt%. Stable temperature control
WHSV =base
80
90
100
ty, % 230
240
250WHSV =baseH2/CO=1.5
WHSV =baseH2/CO=2.0
WHSV =2xbaseH2/CO=2.0
50
60
70
CH
4 se
lect
ivi
200
210
220
ratu
re, o
C
30
40
50
conv
ersi
on o
r
180
190
200
Bed
tem
per
CO conversionCH4 selectivityT topT bottom
0
10
20CO
c
150
160
170T bottom
14
00 24 48 72 96 120 144 168 192 216 240 264 288
Time on stream, h
150
Impact of reaction temperature on performance of structured catalyst bed• At a given WHSV, CO conversion and CH4 selectivity increase with
temperature, as expected110 CO at WHSV=38.7 Feed H2/CO ratio =2
8090
100110
ty
CH4 at WHSV=38.7CO at whsv=77.4CH4 at WHSV=77.4
25 bar
50607080
or s
elec
tivit
20304050
Con
vers
ion
o
010
20
205 210 215 220 225 230
C
15
205 210 215 220 225 230
Temp, oC
Impact of feed gas superficial linear velocity on performance of structured catalyst bed
• CO conversion decreases with increasing Vg (= increasing WHSV), as expected.
• CH4 selectivity increases with Vg higher CH4 selectivity at lower CO conversion opposite to results of conventional slurry or packed particle beds opposite to results of conventional slurry or packed particle beds
100110
%
Feed H2/CO ratio =225 bar
60708090
sele
ctiv
ity, %
CO at 210oC
30405060
vers
ion
or s CO at 210oC
CH4 at 210oC
CO at 225oCCH4 at 225oC
01020
Con
v
16
0.00 0.05 0.10 0.15 0.20
Vg, cm/s
Steady‐state performance of crushed monolith catalyst particle• 60-200mesh (~170um), H2/CO = 2, 25 bar, 210oC• Very difficult to control temperature. CO conversion was unstable under const
conditions. Very high CH4 selectivity
80
90
100
ity, %
230
240
250CO conversion
CH4 selectivity
T top
WHSV = 0.5 x base
60
70
80
r CH
4 sel
ectiv
i
210
220
230
ture
, ºC
p
T bottom
30
40
50
O c
onve
rsio
n o
180
190
200
Tem
pera
t
0
10
20CO
150
160
170
17
0 24 48 72 96 120
Time-on-Stream, h
Comparison of structured bed to crushed monolith particle bed under same temperature• The structured bed shows CO conversion activity a few times higher than the
crushed particle bed.
• The structured bed enables <10% CH4 selectivity at nearly complete one-pass CO 4 y y p pconversion.
100 210oC, 25 bar1820 Typical particle bed
60
80
sion
% Structured bed
1012141618
ctiv
ity, % Paradigm shift
by structured bed
20
40
O c
onve
rs
Particle bed 468
10
CH
4 se
lec
210oC25 b
0
20
0 20 40 60 80 100
CO Particle bed
02
0 20 40 60 80 100
C 25 bar
18
WHSV, g/g/h CO conversion, %
Comparison of structured bed to crushed monolith particle bed at different temperature • Structured bed consistently provides CO conversion a few times higher
than the particle bed under the same reaction conditions
110 Feed H2/CO ratio =2
8090
100110 Feed H2/CO ratio =2
25 bar
607080
r sel
ectiv
ity CO monolith WHSV=38.7CH4 monolith WHSV=38.7CO particle whsv=35CH4 particle WHSV=35
304050
onve
rsio
n or CH4 particle WHSV 35
01020
20 210 21 220 22 230
Co
19
205 210 215 220 225 230Temp, oC
Proposed physical models for multiphase reaction in different catalyst beds
Packed particle bed or slurry bed may be uniform at macro-scale. Segregation of gas/liquid/solid (catalyst) is inevitable at individual particle scale
Micro-structured catalyst channel provides uniform contacting of gas/liquid/catalysty p g g q y
Catalyst surface coverage by a dynamic, thin liquid film favors for low CH4selectivity and high reaction rate.
SSyngas gas
Syngas gasCatalyst
layerLiquid film
Syngas Catalyst layer
Liquid film
Syngas
Inert supportInert support
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Structured catalyst channel Packed catalyst pellets Slurry bed
Concluding remark
For gas-to-liquid (FT) reaction, micro-structured catalyst bed designs lead to some unexpected, exceptionally good performance attributes with a common catalyst composition:
• >90% CO conversion at <10% CH4 selectivity• A few times of higher activity than the same catalyst material in crushed particle
form• Good temperature control in conventional sizes of reaction tubes (micro-channel
reactor is not necessary)• Catalyst bed free of plugging by wax• A compact, high throughput gas-to-liquid catalytic reactor is possible
Note: poor performances obtained with conventional catalyst particle or slurry beds b d t th t d i i th th d t t l t t i l it lfmay be due to the reactor design issues rather than due to catalyst material itself.
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