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Catalytic zeolite membrane reactors for the selective CO oxidation
Desalination 200 (2006) 702–704
Catalytic zeolite membrane reactors for the selective CO oxidation Paola Bernardoa, Catia Algieria, Giuseppe Barbieria*, Enrico Driolia,b a
Institute for Membrane Technology ITM – CNR, Via Pietro Bucci, c/o The University of Calabria, Cubo 17/C, 87030 Rende CS, Italy Tel. +39 0984 492029; Fax +39 0984 402103; email: [email protected] b Department of Chemical Engineering and Materials, The University of Calabria, Cubo 44/A, Via Pietro Bucci, 87030 Rende CS, Italy Received 29 October 2005; accepted 4 March 2006
1. Introduction CO selective oxidation (Selox) is known as an interesting and economic approach for the purification of H2-rich gas streams. A selective catalyst, typically Pt-supported [1], is necessary to avoid H2 consumption. Most of these catalysts have been studied over fixed bed or monolith; the use of catalytic membrane reactors (MRs) was investigated only in a few papers [2–4]. In the present work CO Selox was studied using catalytic Pt-Y zeolite membranes (tubular) prepared by ion-exchange as reported in [4]. Catalytically active particles are entrapped in a thin zeolite layer (a few microns thick), avoiding the by-pass problems, generally, shown in catalyst pellets.
mixture forced through the membrane), using the experimental apparatus described in [4]. Two feed compositions (no CO2 and with 15% CO2) and different pressures were considered at 200°C. The CO content was ca. 1%, simulating a reformate shifted gas mixture (H2 ca. 60%); the CO2 in the feed was added for a more realistic evaluation. The CO and the O2 conversion were calculated as: X CO =
Feed Permeate FOFeed - FOPermeate FCO - FCO 2 2 , X = O2 Feed FCO FOF2eed
The oxygen selectivity (S) is defined as the ratio of O2 consumed for the CO oxidation reaction over the total O2 consumption:
( (F
Feed Permeate 0.5 FCO - FCO
)= 1 X ) λX
CO
2. Theory and experimental
S=
The catalytic MR tests were performed with a flow-through MR configuration (the reactant
where l is the O2/CO stoichiometric equivalent
*Corresponding author.
Feed O2
ratio λ = 2
-
FOFeed 2 Feed FCO
FOPermeate 2
.
Presented at EUROMEMBRANE 2006, 24–28 September 2006, Giardini Naxos, Italy. 0011-9164/06/$– See front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2006.03.513
O2
P. Bernardo et al. / Desalination 200 (2006) 702–704
The yield of CO2 (produced by CO oxidation) is
YCO2 =
Formed FCO 2
FOFeed 2
703
4. Conclusions CO Selox for the purification of H2-rich streams was studied in MRs using Pt-loaded catalytic membranes. An almost complete CO removal (ca. 10 ppm) was achieved operating at 200° C and 4 bar starting from 1% CO in the feed with l = 2.2 and no CO2. The increase in operating pressure (up to 4 bar) was effective in improving the MR CO conversion and CO2 yield. The CO2 presence in the feed (ca. 15%) slightly reduced the MR performance. The results obtained confirm the interest in catalytic membranes for CO Selox.
F Reacted 2 = COFeed = 2 X O2 S = X CO λ FO2
3. Results and discussion The reaction pressure has a positive effect on both CO conversion and CO2 yield (Fig. 1). The CO2 presence in the feed (ca. 15%) slightly reduced the MR performance. A more pronounced CO2 effect was observed at 1 bar, while the difference in the CO content measured in the MR outlet stream was reduced at higher reaction pressures (Fig. 1a). Fig. 1b reports the CO2 yield as a function of the CO conversion. The experimental data are lined up on the line with a slope 2/l. An efficient and selective system should be located in the diagram upper part (total CO conversion and high reaction yield). Therefore, the increase in the reaction pressure is useful in improving the CO removal.
Acknowledgements This work was performed also with the contribution of the “Ministero degli Affari Esteri, Direzione Generale per la Promozione e la Cooperazione Culturale” and CNR-KOSEF agreement. The authors thank Mr. F. Cofone (Istituto per l’Inquinamento Atmosferico – CNR, Rende CS, Italy) for the atomic adsorption spectrometry analyses. 100
1500
3, 4 bar
120
YCO2, %
COout, ppm
80
100 80
1 bar
60
40
60 20
With CO2 No CO2
40 20
0
0 0 (a)
1
2
3 P, bar
4
0
5 (b)
20
40
60
80
100
XCO, %
Fig. 1. Measured (a) CO in the MR outlet stream versus the reaction pressure and (b) CO2 yield versus the CO conversion. T = 200° C. O2:CO:H2:N2:CO2 = 0.99:0.92:59.5:38.6:0 No CO2 Feed molar composition O2:CO:H2:N2:CO2 = 0.99:0.92:60.2:22.7:15.2 With CO2
704
P. Bernardo et al. / Desalination 200 (2006) 702–704
References [1] [2]
M. Brown and A. Green, Treatment of gases, US Patent, 3,088,919, 1963. Y. Hasegawa, A. Ueda, K. Kusakabe and S. Morooka, Oxidation of CO in hydrogen-rich gas using a novel membrane combined with a microporous SiO2 layer and a metal-loaded g -Al2O3 layer, Applied Catalysis A, 225 (2002) 109–115.
[3]
[4]
Y. Hasegawa, K. Kusakabe, S. Morooka, Selective oxidation of carbon monoxide in hydrogen-rich mixtures by permeation through a platinumloaded Y-type zeolite membrane, J. Membr. Sci., 190 (2001) 1–8. P. Bernardo, C. Algieri, G. Barbieri and E. Drioli, Catalytic (Pt-Y) membranes for the purification of H2-rich streams, Catal. Today, (2006) accepted.
Catalytic zeolite membrane reactors for the selective CO oxidation Paola Bernardoa, Catia Algieria, Giuseppe Barbieria*, Enrico Driolia,b a
Institute for Membrane Technology ITM – CNR, Via Pietro Bucci, c/o The University of Calabria, Cubo 17/C, 87030 Rende CS, Italy Tel. +39 0984 492029; Fax +39 0984 402103; email: [email protected] b Department of Chemical Engineering and Materials, The University of Calabria, Cubo 44/A, Via Pietro Bucci, 87030 Rende CS, Italy Received 29 October 2005; accepted 4 March 2006
1. Introduction CO selective oxidation (Selox) is known as an interesting and economic approach for the purification of H2-rich gas streams. A selective catalyst, typically Pt-supported [1], is necessary to avoid H2 consumption. Most of these catalysts have been studied over fixed bed or monolith; the use of catalytic membrane reactors (MRs) was investigated only in a few papers [2–4]. In the present work CO Selox was studied using catalytic Pt-Y zeolite membranes (tubular) prepared by ion-exchange as reported in [4]. Catalytically active particles are entrapped in a thin zeolite layer (a few microns thick), avoiding the by-pass problems, generally, shown in catalyst pellets.
mixture forced through the membrane), using the experimental apparatus described in [4]. Two feed compositions (no CO2 and with 15% CO2) and different pressures were considered at 200°C. The CO content was ca. 1%, simulating a reformate shifted gas mixture (H2 ca. 60%); the CO2 in the feed was added for a more realistic evaluation. The CO and the O2 conversion were calculated as: X CO =
Feed Permeate FOFeed - FOPermeate FCO - FCO 2 2 , X = O2 Feed FCO FOF2eed
The oxygen selectivity (S) is defined as the ratio of O2 consumed for the CO oxidation reaction over the total O2 consumption:
( (F
Feed Permeate 0.5 FCO - FCO
)= 1 X ) λX
CO
2. Theory and experimental
S=
The catalytic MR tests were performed with a flow-through MR configuration (the reactant
where l is the O2/CO stoichiometric equivalent
*Corresponding author.
Feed O2
ratio λ = 2
-
FOFeed 2 Feed FCO
FOPermeate 2
.
Presented at EUROMEMBRANE 2006, 24–28 September 2006, Giardini Naxos, Italy. 0011-9164/06/$– See front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2006.03.513
O2
P. Bernardo et al. / Desalination 200 (2006) 702–704
The yield of CO2 (produced by CO oxidation) is
YCO2 =
Formed FCO 2
FOFeed 2
703
4. Conclusions CO Selox for the purification of H2-rich streams was studied in MRs using Pt-loaded catalytic membranes. An almost complete CO removal (ca. 10 ppm) was achieved operating at 200° C and 4 bar starting from 1% CO in the feed with l = 2.2 and no CO2. The increase in operating pressure (up to 4 bar) was effective in improving the MR CO conversion and CO2 yield. The CO2 presence in the feed (ca. 15%) slightly reduced the MR performance. The results obtained confirm the interest in catalytic membranes for CO Selox.
F Reacted 2 = COFeed = 2 X O2 S = X CO λ FO2
3. Results and discussion The reaction pressure has a positive effect on both CO conversion and CO2 yield (Fig. 1). The CO2 presence in the feed (ca. 15%) slightly reduced the MR performance. A more pronounced CO2 effect was observed at 1 bar, while the difference in the CO content measured in the MR outlet stream was reduced at higher reaction pressures (Fig. 1a). Fig. 1b reports the CO2 yield as a function of the CO conversion. The experimental data are lined up on the line with a slope 2/l. An efficient and selective system should be located in the diagram upper part (total CO conversion and high reaction yield). Therefore, the increase in the reaction pressure is useful in improving the CO removal.
Acknowledgements This work was performed also with the contribution of the “Ministero degli Affari Esteri, Direzione Generale per la Promozione e la Cooperazione Culturale” and CNR-KOSEF agreement. The authors thank Mr. F. Cofone (Istituto per l’Inquinamento Atmosferico – CNR, Rende CS, Italy) for the atomic adsorption spectrometry analyses. 100
1500
3, 4 bar
120
YCO2, %
COout, ppm
80
100 80
1 bar
60
40
60 20
With CO2 No CO2
40 20
0
0 0 (a)
1
2
3 P, bar
4
0
5 (b)
20
40
60
80
100
XCO, %
Fig. 1. Measured (a) CO in the MR outlet stream versus the reaction pressure and (b) CO2 yield versus the CO conversion. T = 200° C. O2:CO:H2:N2:CO2 = 0.99:0.92:59.5:38.6:0 No CO2 Feed molar composition O2:CO:H2:N2:CO2 = 0.99:0.92:60.2:22.7:15.2 With CO2
704
P. Bernardo et al. / Desalination 200 (2006) 702–704
References [1] [2]
M. Brown and A. Green, Treatment of gases, US Patent, 3,088,919, 1963. Y. Hasegawa, A. Ueda, K. Kusakabe and S. Morooka, Oxidation of CO in hydrogen-rich gas using a novel membrane combined with a microporous SiO2 layer and a metal-loaded g -Al2O3 layer, Applied Catalysis A, 225 (2002) 109–115.
[3]
[4]
Y. Hasegawa, K. Kusakabe, S. Morooka, Selective oxidation of carbon monoxide in hydrogen-rich mixtures by permeation through a platinumloaded Y-type zeolite membrane, J. Membr. Sci., 190 (2001) 1–8. P. Bernardo, C. Algieri, G. Barbieri and E. Drioli, Catalytic (Pt-Y) membranes for the purification of H2-rich streams, Catal. Today, (2006) accepted.