Characterization and Performance of Pd/CeO2 Catalysts as a ... · 10 wt% Pd/CeO2 foil coatings: 1....
1
10 wt% Pd/CeO 2 foil coatings: 1. CeO 2 sol-gel prepared from cerium ammonium nitrate 2 , 2. CeO 2 sol-gel dripped uniformly over microchannels, followed by drying (70 ºC, overnight) and calcination (500 ºC, 5 h, air). 3. CeO 2 layer dripped with PdCl 2 solution until 10 wt. %, dried and calcined as before. 10 wt% Pd/CeO 2 50-120 μm catalyst particles: Deposition – precipitation, using CeO 2 nanopowder (Sigma Aldrich, d < 25 nm) and PdCl 2 solution as precursors. Characterization and Performance of Pd/CeO Characterization and Performance of Pd/CeO 2 Catalysts as a Powder in Fixed Catalysts as a Powder in Fixed- bed bed Reactor and as a Coating in a Stacked Foil Reactor and as a Coating in a Stacked Foil Microreactor Microreactor for the Methanol Synthesis for the Methanol Synthesis Xuyen Kim Phan 1 , John Walmsley 2 , Hamidreza Bakhtiary-Davijany 1 , Rune Myrstad 2 , Peter Pfeifer 3 , Anders Holmen 1 and Hilde J. Venvik 1 1. Department of Chemical Engineering, Norwegian University of Science and Technology (NTNU), Sem Sælands vei 4, N-7491, Trondheim, Norway 2. SINTEF Materials and Chemistry, Sem Selands vei 2A, N-7465 Trondheim, Norway 3. Karlsruhe Institute of Technology, Institute for Micro Process Engineering, D-76344 Eggenstein-Leopoldshafen, Germany Results and discussion Results and discussion Introduction Introduction Experiments Experiments 14 structured and coated foils stacked and sealed inside alloy 800 housing graphite (Frentzelit) [4] References References [1] M.L. Poutsma, L.F. Elek, P.A. Ibarbia, A.P. Risch and J.A. Rabo, J. Catal., 52 (1978) 157. [2] W.J. Shen, Y. Ichihashi, M. Okumura and Y. Matsumura, Catal. Lett., 64 (2000) 23. [3] W.-J. Shen, Y. Ichihashi and Y. Matsumura, Catal. Lett., 79 (2002) 125. [4] X. K. Phan, H. D. Bakhtiary, R. Myrstad, J. Thormann, P. Pfeifer, H. J. Venvik, A Holmen, Ind. Eng. Chem. Res. 49 (2010) 10934. [5] N. Ozer, J. P. Cronin, S. Akyuz, in Switchable Materials and Flat Panel Displays; SPIE: Denver, CO, 1999; p 103. [6] A. Trovarelli, Catal. Rev. - Sci. Eng., 38 (1996) 439 Acknowledgements Acknowledgements Conclusions Conclusions The Pd/CeO 2 catalysts show extremely high initial activity but deactivate significantly Transition from high S CH4 and low S CH3OH to decreased CH 4 formation and improved S CH3OH upon stabilization. Activity of Pd/CeO 2 foil coating (sol-gel synthesis) substantially better than of Pd/CeO 2 particles (deposition-precipitation) Significantly higher Pd dispersion of Pd/CeO 2 powder than of Pd/CeO 2 foil coating Effects attributed to the Pd nanoparticles being covered by a ceria during the preparation and subsequent reduction [6] Objectives Explore the properties of Pd-based catalyst coatings for methanol synthesis in microstructured reactors Reaction mechanism over Pd to facilitate unconventional synthesis gas [1] High activity potential with particular supports [2] ? Figure 1: The stacked foil microreactor (SFMR) under operation (a), opened (b). Preparation of Pd/CeO 2 catalysts: Pd/CeO 2 catalyst activity and stability Solution for Remote Natural Gas Fields or Biofuels? Microstructured reactors have recently been proposed as alternatives to the conventional reactor technology in compact applications due to their heat and mass transfer properties Reactors and reaction conditions SS tube fixed-bed reactor (FBR, Φ=10mm). Reduction at 1 bar and 300 ºC in 10 vol.% H 2 in N 2 . Methanol synthesis at 220-350 ºC and 80 bar (H 2 /CO/CO 2 /N 2 = 65/25/5/5). Pd/CeO 2 powder catalyst characterization Steam/O 2 ref/ gasification Natural gas/biomass Syngas Product Methanol Synthesis This publication forms a part of the Remote Gas project, performed under the Research Council of Norway PETROMAKS program (168223/S30). The authors acknowledge the partners; Statoil, UOP, Aker Kværner, DNV, and Bayer Gas for support. Glasgow, Scotland 28 August - 2 Sept 2011 (a) (b) Characterization S BET by N 2 adsorption (-196 ºC Micromeretics Tristar 3000). XRD Bruker AXS D8 Focus (CuKα, 20-90º, 0.03º step, 0.6s/step.. Volumetric CO chemisorption at (313 K) of prereduced sample. D, %, calculated assuming Pd/CO=1 SEM (Zeiss Ultra 20 kV) and SEM EDS (Bruker Quantex). TEM (JEOL 2010F, 200 kV) and TEM EDS (Oxford Instruments INCA). Gas Recycle TOS [h] 0 50 100 150 200 250 300 350 400 r MeOH [mmol/h/g cat ] 0 20 40 60 80 100 120 140 X CO [%] 0 10 20 30 40 50 60 70 rMeOH-FBR r MeOH -SFMR r MeOH -eq XCO-FBR X CO -SFMR r MeOH -eq r MeOH -SFMR X CO -SFMR r MeOH -FBR X CO -FBR TOS [h] 0 50 100 150 200 250 300 350 400 r CH4 [mmol/h/g cat ] 0 20 40 60 80 100 120 140 160 180 FBR SFMR Pd/CeO 2 foil coating characterization Figure 6: SEM pictures of the fresh Pd/CeO 2 coated foil at low (a) and high (b) magnification. Figure 7: SEM pictures of the fresh (a-b) and the used (c-d) Pd/CeO 2 coated foil at 10 4 -10 5 magnification. STEM Pd Ce (a) (b) (c) (d) O STEM Ce Pd (c) (d) (a) (b) O 2-Theta - Scale 26 30 40 50 60 70 80 90 Pd CeO2 Used Pd/CeO2powder Fresh Pd/CeO2 powder CeO2 support a BET surface area. b Average pore size and pore volume calculated by using BJH method. c Pd dispersion calculated from CO chemisorption at 313 K. d Pd particle size based on CO chemisorption at 313 K. SBET [m 2 /g] a dpore [nm] b Pore volume [cm 3 /g] b D [%] c dp [mn] d CeO2 32 21 0.178 - - Pd/CeO2 52 14 0.183 32 3.4 Pore with [nm] 1 2 5 10 20 30 50 70 90 99 100 Pore volume [cm 3 /g.nm] 0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 CeOsupport fresh Pd/CeOpowder Figure 3: XRD diffractograms (a) of the CeO 2 support and the Pd/CeO 2 powders before and after testing in FBR and bright-field TEM micrographs (b) of the fresh Pd/CeO 2 powder at different magnifications. Figure 4: Dark-field STEM micrograph (a) and complementary EDS Ce (b), Pd (c), and O (d) mapping of the fresh (left panels) and used (right panels) Pd/CeO 2 powder catalyst. Figure 2: CO conversion and rate of CH 3 OH (a) and CH 4 by- product (b) formation with time on stream (TOS) for Pd/CeO 2 powder catalyst (FBR) and Pd/CeO 2 foil coating in SFMR. T = 300 ºC, contact time W/F = 110 [ms·g cat /cm 3 ], pressure 80 bar and syngas composition H 2 /CO/CO 2 /N 2 = 65/25/5/5. STEM Figure 5: BET and chemisoption data Fresh catalyst Used catalyst (b) (a) (b) (a) (a) (b) (a) (b) (c) (d)
Transcript of Characterization and Performance of Pd/CeO2 Catalysts as a ... · 10 wt% Pd/CeO2 foil coatings: 1....
10 wt% Pd/CeO2
foil coatings: 1.
CeO2
sol-gel prepared from cerium ammonium nitrate2,
2.
CeO2
sol-gel dripped uniformly over microchannels, followed by
drying (70 ºC, overnight) and calcination
(500 ºC, 5 h, air).
3.
CeO2
layer dripped with PdCl2
solution until 10 wt. %, dried and
calcined
as before.
10 wt% Pd/CeO2
50-120 μm
catalyst particles:
Deposition –
precipitation, using CeO2
nanopowder
(Sigma Aldrich, d < 25 nm) and PdCl2
solution as precursors.
Characterization and Performance of Pd/CeOCharacterization and Performance of Pd/CeO22
Catalysts as a Powder in FixedCatalysts as a Powder in Fixed--bed bed
Reactor and as a Coating in a Stacked Foil Reactor and as a Coating in a Stacked Foil MicroreactorMicroreactor
for the Methanol Synthesisfor the Methanol Synthesis
Xuyen
Kim Phan1, John Walmsley2, Hamidreza
Bakhtiary-Davijany1, Rune Myrstad2, Peter Pfeifer3, Anders Holmen1
and Hilde J. Venvik1
1.
Department of Chemical Engineering, Norwegian University of Science and Technology (NTNU), Sem
Sælands
vei
4, N-7491, Trondheim, Norway
2.
SINTEF Materials and
Chemistry, Sem
Selands
vei
2A, N-7465 Trondheim, Norway
3.
Karlsruhe Institute of Technology, Institute for Micro Process Engineering, D-76344 Eggenstein-Leopoldshafen, Germany
Results and discussionResults and discussion
IntroductionIntroduction Experiments Experiments
0
1
2
3
4
5
200 250 300 350 400 450 500
Contact time, ms
gr
Pro
du
ct/g
r ca
taly
st/h
r
Microstructured reactor: 255°C, 80 bara
14 structured and coated foils stacked and sealed inside alloy 800 housing graphite (Frentzelit) [4]
ReferencesReferences[1]
M.L. Poutsma, L.F. Elek, P.A. Ibarbia, A.P. Risch and J.A. Rabo,
J. Catal., 52 (1978) 157.
[2] W.J. Shen, Y. Ichihashi, M. Okumura and Y. Matsumura, Catal. Lett., 64 (2000)
23.
[3] W.-J. Shen, Y. Ichihashi and Y. Matsumura, Catal. Lett., 79 (2002) 125.
[4]
X.
K. Phan, H.
D. Bakhtiary, R.
Myrstad, J.
Thormann, P.
Pfeifer, H.
J. Venvik,
A
Holmen, Ind. Eng. Chem. Res. 49 (2010) 10934.
[5]
N. Ozer, J. P. Cronin, S. Akyuz, in Switchable Materials and Flat Panel Displays; SPIE: Denver, CO, 1999; p 103.
[6]
A. Trovarelli, Catal. Rev. -
Sci. Eng., 38 (1996) 439
AcknowledgementsAcknowledgements
ConclusionsConclusions
The Pd/CeO2
catalysts show extremely high initial activity but deactivate significantly
Transition from high SCH4
and low SCH3OH
to decreased CH4
formation and improved SCH3OH
upon stabilization.
Activity of Pd/CeO2
foil coating (sol-gel synthesis) substantially better than of Pd/CeO2
particles (deposition-precipitation)
Significantly higher Pd dispersion of Pd/CeO2
powder than of Pd/CeO2
foil coating
Effects attributed to the Pd nanoparticles
being covered by a ceria during the preparation and subsequent reduction [6]
Objectives
Explore the properties of Pd-based catalyst coatings for methanol synthesis in microstructured
reactors
Reaction mechanism over Pd to facilitate unconventional synthesis gas [1]
High activity potential with particular supports [2] ?
Figure 1: The stacked foil microreactor
(SFMR) under operation (a), opened (b).
Preparation of Pd/CeO2
catalysts:
Pd/CeO2
catalyst activity and stability
Solution for Remote Natural Gas Fields or Biofuels?
Microstructured
reactors have recently been proposed as alternatives to the
conventional reactor technology in compact applications due to their heat and mass transfer properties
Reactors and reaction conditions
SS tube fixed-bed reactor (FBR, Φ=10mm).
Reduction at 1 bar and 300 ºC in 10 vol.% H2
in N2
.
Methanol synthesis at 220-350 ºC and 80 bar (H2
/CO/CO2
/N2
= 65/25/5/5).
Pd/CeO2
powder catalyst characterization
Steam/O2
ref/
gasification
Natural gas/biomass
Syngas ProductMethanol Synthesis
This publication forms a part of the Remote Gas project, performed under the Research Council of Norway PETROMAKS program (168223/S30).
The authors acknowledge the partners; Statoil, UOP, Aker Kværner, DNV, and Bayer Gas for support.
Glasgow, Scotland
28 August -
2 Sept 2011
(a) (b)
Characterization
SBET
by N2
adsorption (-196 ºC Micromeretics
Tristar
3000).
XRD Bruker
AXS D8 Focus (CuKα, 20-90º, 0.03º
step, 0.6s/step..
Volumetric CO chemisorption
at (313 K) of prereduced
sample. D, %, calculated assuming Pd/CO=1
SEM (Zeiss
Ultra 20 kV) and SEM EDS (Bruker
Quantex).
TEM (JEOL 2010F, 200 kV) and TEM EDS (Oxford Instruments INCA).
Gas Recycle
TOS [h]
0 50 100 150 200 250 300 350 400
r Me
OH [m
mol
/h/g
cat]
0
20
40
60
80
100
120
140
XC
O [%
]
0
10
20
30
40
50
60
70
rMeOH-FBR
rMeOH-SFMR
rMeOH-eq
XCO-FBR
XCO-SFMR
rMeOH-eq
rMeOH-SFMR
XCO-SFMR
rMeOH-FBR
XCO-FBR
TOS [h]
0 50 100 150 200 250 300 350 400
r CH
4 [m
mo
l/h/g
cat]
0
20
40
60
80
100
120
140
160
180
FBRSFMR
Pd/CeO2
foil coating characterization
Figure 6:
SEM pictures of the fresh Pd/CeO2
coated foil at low (a) and high (b) magnification.
Figure 7:
SEM pictures of the fresh (a-b) and the used (c-d) Pd/CeO2
coated foil at 104-105 magnification.
STEM
Pd
Ce
(a) (b)
(c) (d)
O
STEM Ce
Pd
(c) (d)
(a) (b)
O
2-Theta - Scale
26 30 40 50 60 70 80 90
Pd CeO2
Used Pd/CeO2 powder
Fresh Pd/CeO2 powder
CeO2 support
a
BET surface area.b
Average pore size and pore volume calculated by using BJH method.c
Pd dispersion calculated from CO chemisorption
at 313 K.d
Pd particle size based on CO chemisorption
at 313 K.
SBET [m2/g]a dpore [nm]b Pore volume [cm3/g]b D [%]c dp [mn]d
CeO2 32 21 0.178 - -
Pd/CeO2 52 14 0.183 32 3.4
Pore with [nm]
1 2 5 10 20 30 50 70 90 99 100
Po
re v
olu
me
[cm
3 /g.n
m]
0.000
0.001
0.002
0.003
0.004
0.005
0.006
0.007
CeO2 support
fresh Pd/CeO2 powder
Figure 3:
XRD diffractograms
(a) of the CeO2
support and the Pd/CeO2
powders before and after testing in FBR and bright-field TEM micrographs (b) of the fresh Pd/CeO2
powder at different magnifications.
Figure 4:
Dark-field STEM micrograph (a) and complementary EDS Ce
(b), Pd (c), and O (d) mapping of the fresh (left panels) and used (right panels) Pd/CeO2
powder catalyst.
Figure 2:
CO conversion and rate of CH3
OH (a) and CH4
by-
product (b) formation with time on stream (TOS) for Pd/CeO2 powder catalyst (FBR) and Pd/CeO2
foil coating in SFMR.
T = 300 ºC, contact time W/F = 110 [ms·gcat
/cm3], pressure 80 bar and syngas
composition H2
/CO/CO2
/N2
= 65/25/5/5.
STEM
Figure 5:
BET and chemisoption
data
Fresh
catalyst Used catalyst
(b)
(a) (b)(a)(a) (b)
(a) (b)
(c) (d)
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