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Synthesis gas production by steam reforming of ethanol
Applied Catalysis A: General 220 (2001) 123–127
Synthesis gas production by steam reforming of ethanol V.V. Galvita a , G.L. Semin a , V.D. Belyaev a , V.A. Semikolenov a , P. Tsiakaras b , V.A. Sobyanin a,∗ a
b
Boreskov Institute of Catalysis, Prospekt Akademika Lavrentieva 5, 630090 Novosibirsk, Russia Department of Mechanical and Industrial Engineering, University of Thessaly, Pedion Areos, 38334 Volos, Greece Received 19 January 2001; received in revised form 13 June 2001; accepted 13 June 2001
Abstract A two-layer fixed-bed catalytic reactor for syngas production by steam reforming of ethanol has been proposed. In the reactor, ethanol is first converted to a mixture of methane, carbon oxides and hydrogen over a Pd-based catalyst and then this mixture is converted to syngas over a Ni-based catalyst for methane steam reforming. It has been shown that the use of the two-layer fixed-bed reactor prevents coke formation and provides the syngas yield closed to equilibrium. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Ethanol; Steam reforming; Syngas; Two-layer fixed-bed reactor
1. Introduction Ethanol is a renewable material as it can be produced from biomass [1,2]. Bioethanol — an aqueous solution containing ca. 12 wt.% ethanol — can be used as an alternative fuel or as a feedstock for the production of chemicals. In recent years, much attention has been focused on the study of ethanol steam reforming to syngas or hydrogen-rich gas [3–8]. The process is particularly attractive because it utilizes bioethanol without distillation and produces hydrogen, which is seriously considered as a feed for fuel cells [9,10]. Thermodynamic analysis of ethanol steam reforming has shown that methane is the main reaction product at moderate temperatures, whereas higher temperatures and high water/ethanol molar ratio favor the production of syngas or hydrogen-rich gas [3,4]. Experimental studies of ethanol steam reforming have ∗ Corresponding author. Fax: +7-383-2-3432-69. E-mail address: [email protected] (V.A. Sobyanin).
been performed using conventional flow reactors with cobalt supported catalysts [7] or potassium-promoted nickel–copper supported catalysts [5,6]. The main problems during these experiments were the catalysts’ coking and formation of undesirable products such as methane, acetaldehyde, etc. In order to overcome these problems, a two-layer fixed-bed reactor has recently been proposed in order to run ethanol-to-syngas steam reforming [8]. In this reactor, ethanol is converted to acetaldehyde and hydrogen over the Cu/SiO2 catalyst. Acetaldehyde is then converted to syngas over the Ni/MgO catalyst. In the present paper, the ethanol steam reforming to syngas or hydrogen-rich gas is studied in a modified two-layer fixed-bed reactor. In contrast to the reactor used in [8], in the present reactor ethanol decomposes to methane, hydrogen and carbon oxides over the first catalyst layer and then the gas mixture produced converts to syngas over the second catalyst layer. The first layer was made of Pd-based catalyst, which was chosen based on numerous publications [11–14]
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V.V. Galvita et al. / Applied Catalysis A: General 220 (2001) 123–127
reporting that ethanol easily decomposes over supported and bulk Pd catalysts. The second layer was made of Ni-based catalyst due to its high activity for methane steam reforming [15,16]. 2. Experimental
The compositions of the inlet and outlet gas mixtures were analyzed on-line by two gas chromatographs “Tsvet-500” (Russia) using Molecular Sieves and Porapak-Q columns and thermal conductivity detectors. The concentrations were measured within a ±5% error.
2.1. Catalysts
3. Results and discussion
Pd supported on Sibunit (a special porous carbonaceous material [17]) and industrial Ni-containing catalyst GIAP-16 for methane steam reforming [15] were used in this work. Pd supported on Sibunit (Pd/C) catalyst was prepared as described in [18]. The Pd content was 1 wt.%. The catalyst particles were spheres of size 1.2–1.5 mm, pore volume and the BET surface area were 0.74 cm3 /g and 400 m2 /g, respectively. XPS studies proved metallic Pd to form on Sibunit. According to TEM, both fresh and spent (after a 100 h operation in ethanol steam reforming) samples of the Pd/C catalyst contained Pd particles of size 40–60 Å. This catalyst will be described in more detail in a separate paper [19]. GIAP-16 containins 24–26 wt.% NiO, 55–59 wt.% Al2 O3 and 14–16 wt.% CaO. The particle size of the catalyst used in the present study ranged 1.2–1.5 mm.
3.1. Catalytic performance of Pd/C
2.2. Catalytic activity measurements The reaction of ethanol steam reforming was carried out under atmospheric pressure in a conventional flow reactor and in a two-layer fixed-bed reactor. The reactors were made of a quartz tube with i.d. 8 mm. Each layer consisted of 1 g of the catalyst mixed with 3 g of inert quartz powder. The catalyst layers were fixed by quartz wool. The distance between the two catalyst beds in the two-layer fixed-bed reactor was 100 mm. The catalyst activities were measured using two reaction mixtures: 11 vol.% C2 H5 OH+89 vol.% H2 O, and 49 vol.% C2 H5 OH + 51 vol.% H2 O. To prepare each mixture, a liquid water/ethanol solution (molar ratios 8.1/1 or 1.04/1) was supplied into a vaporizer and the vapor produced was fed in the reactor at a space velocity (WHSV) of 1600–2200 cm3 /h g. Before experiment, the GIAP-16 catalyst was reduced in situ by hydrogen for 1 h at 750◦ C. The Pd/C catalyst was used without any pretreatment.
With both feed compositions (water/ethanol molar ratios 8.1/1 and 1.04/1), only hydrogen, methane, carbon monoxide and carbon dioxide were produced on Pd/C catalyst in the temperature range 210–380◦ C. Fig. 1 demonstrates the effect of temperature on ethanol conversion and product concentrations for the inlet water/ethanol mixture with molar ratio 8.1/1. It is seen that the ethanol conversion increases with increasing temperature and attains 100% at 330◦ C. The CO concentration passes through broad maximum, whereas the CO2 , CH4 and H2 concentrations increase with increasing temperature. Analysis of the temperature dependencies of the CO, CO2 , CH4 and H2 concentrations proves that at all temperatures the concentrations obey the following equations: [H2 ] = [CH4 ] + [CO2 ]
(1)
[CH4 ] = [CO2 ] + [CO]
(2)
If so, the CH4 , CO and H2 are the primary products of the ethanol decomposition C2 H5 OH = CH4 + CO + H2
(3)
while CO2 is the secondary product and forms owing to water-gas shift reaction CO + H2 O = CO2 + H2
(4)
This suggestion is confirmed by the data presented in Fig. 2, which illustrates the effect of temperature on ethanol conversion and outlet product concentrations for the inlet water/ethanol mixture with molar ratio 1.04/1. The ethanol conversion increases with increasing temperature and attains 100% at 360◦ C. The concentrations of H2 , CO, CH4 and CO2 also increase
V.V. Galvita et al. / Applied Catalysis A: General 220 (2001) 123–127
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Fig. 1. Temperature dependencies of ethanol conversion and product concentrations upon steam reforming of ethanol over the Pd/C catalyst. Experimental conditions: WHSV = 2200 cm3 /h g, inlet molar ratio water/ethanol = 8.1/1.
with increasing temperature. Besides, in the temperature range 240–310◦ C, no CO2 is observed among the reaction products, while the concentrations of H2 , CO and CH4 are similar. This means that only reaction (3) proceeds in this temperature interval. As the temperature increases to 310–370◦ C, CO2 appears among the reaction products, and the concentration of H2 exceeds
that of CH4 , which in its turn exceeds the concentration of CO. The concentrations of H2 , CO, CO2 and CH4 obey equations (1) and (2). This means that CO2 forms by reaction (4). Thus, the results obtained confirm that Pd/C is an active and selective catalyst for ethanol decomposition to methane, hydrogen and carbon oxides gas mixture.
Fig. 2. Temperature dependencies of ethanol conversion and product concentrations upon steam reforming of ethanol over the Pd/C catalyst. Experimental conditions: WHSV = 1600 cm3 /h g, inlet molar ratio water/ethanol = 1.04/1.
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V.V. Galvita et al. / Applied Catalysis A: General 220 (2001) 123–127
This conclusion agrees with literature data [11–14]. Besides, Pd/C exhibited good stability as no catalyst decay was observed during 100 h on stream. The catalytic behavior of Pd/C will be discussed in more detail in a separate paper [19]. 3.2. Catalytic performance of GIAP-16 In contrast to the Pd/C catalyst, GIAP-16 produced acetaldehyde, methane, hydrogen and carbon oxides by reacting ethanol and steam and substantial amounts of coke/carbon were observed on the used catalyst. In particular, when water/ethanol mixtures (molar ratio 8.1/1 or 1.04/1) were fed to GIAP-16, a considerable carbon imbalance and increased pressure drop was observed in the temperature range 300–650◦ C. Moreover, as visual inspection showed, after a 0.5–2 h operation, the reactor was plugged with carbon. So, owing to low coking resistance, the GIAP-16 catalyst is unacceptable to run the ethanol steam reforming in the conventional flow reactor. Then, based on the idea of two-layer fixed-bed reactor, we decided to try GIAP-16 for steam reforming of the gas mixture (CH4 , CO, CO2 , H2 ) resulting from the ethanol decomposition over the Pd/C catalyst (see Section 3.1). The following section presents the results of ethanol steam reforming to syngas in the two-layer fixed-bed reactor.
3.3. Performance of two-layer fixed-bed reactor When water/ethanol mixture (molar ratio 8.1/1) was fed into the two-layer fixed-bed reactor, only H2 , CO, CO2 and CH4 were detected among the reaction products. Catalytic layers 1 and 2 in this reactor were made of Pd/C and GIAP-16, respectively. Catalytic layer 1 was operated at constant temperature 335 ± 5 K and WHSV = 2200 cm3 /h g. Reactions (3) and (4) proceeding under these experimental conditions provided a 100% conversion of ethanol to the H2 , CO, CO2 and CH4 gas mixture (see Section 3.1). The mixture produced passed to catalytic layer 2 (1 g GIAP-16), which performed the reaction of methane steam reforming in the temperature range 650–800◦ C. Fig. 3 presents the outlet concentrations of H2 , CO, CO2 , CH4 and H2 O as a function of the temperature of catalytic layer 2 upon ethanol steam reforming in the two-layer fixed-bed reactor under the specified experimental conditions. The ethanol conversion was 100% (not shown in Fig. 3). Thermodynamic equilibrium concentrations of H2 , CO, CO2 , CH4 and H2 O are also shown in Fig. 3. These values were calculated on the assumption that the equilibrium composition was controlled by the following reactions: C2 H5 OH = CH4 + CO + H2
Fig. 3. Product concentrations vs. the temperature of catalytic layer 2 upon the ethanol steam reforming in the two-layer fixed-bed reactor. Experimental conditions are specified in Section 3.3. Symbols — experiments, lines — thermodynamic equilibrium values.
V.V. Galvita et al. / Applied Catalysis A: General 220 (2001) 123–127
CO + H2 O = CO2 + H2 CH4 + H2 O = CO + 3H2 The experiment is seen to coincide with the calculated values. Note finally that neither carbon imbalance nor changes of the ethanol conversion and the outlet product concentrations were observed during the ethanol steam reforming in the two-layer fixed-bed reactor (about 100 h on stream). Thus, the data obtained prove appropriate operation of the two-layer fixed-bed reactor in the production of syngas by the ethanol steam reforming.
4. Conclusion The concept of the two-layer fixed-bed reactor seems to be quite promising for the steam reforming of ethanol to syngas. According to this concept, ethanol is first converted to the H2 , CO, CO2 and CH4 gas mixture over a suitable catalyst (for example, Pd/C) and then the mixture produced is converted to syngas over another appropriate catalyst (for example, Ni-based catalyst for methane steam reforming).
Acknowledgements The authors highly appreciate partial financial support provided by INTAS (Project No. 897).
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References [1] M. McCoy, C&EN, 7 December 1998, p. 29. [2] G.W. Barnard, D.O. Hall, Energy from renewable resources, in: H. Dellweg (Ed.), Biotechnology, Vol. 3, Vertlag Chemie GmbH, Weinheim, 1983, 593 pp. [3] K. Vasudeva, N. Mitra, P. Umasankar, S.C. Dhingra, Int. J. Hydrogen Energy 21 (1996) 13. [4] I. Fishtik, A. Alexander, R. Datta, D. Geana, Int. J. Hydrogen Energy 25 (2000) 31. [5] F.J. Marino, E.G. Cerrella, S. Duhalde, M. Jobbady, M.A. Laborde, Int. J. Hydrogen Energy 23 (1998) 1095. [6] F. Marino, M. Jobbagy, G. Baronetti, M. Laborde, Stud. Surf. Sci. Catal. 130 (2000) 2147. [7] F. Haga, T. Nakajama, H. Miya, S. Mashima, Catal. Lett. 48 (1997) 223. [8] S. Freni, N. Mondello, S. Cavallaro, G. Cacciola, V.N. Parmon, V.A. Sobyanin, React. Kinet. Catal. Lett. 71 (2000) 143. [9] Design News, 22 June 1998, p. 88. [10] G. Maggio, S. Freni, S. Cavallaro, J. Power Sources 74 (1998) 17. [11] N. Isawa, O. Yamamoto, R. Tamura, M. Nishikubo, N. Takezawa, Catal. Lett. 62 (1999) 179. [12] N. Takezawa, N. Isawa, Catal. Today 36 (1997) 45. [13] J.L. Davis, M.A. Barteau, Surf. Sci. 187 (1987) 387. [14] R. Shekhar, M.A. Barteau, Catal. Lett. 31 (1995) 221. [15] E.N. Emel’yanov (Ed.), Spravochnik Azotchika, Khimiya, Leningrad, Moscow, 1986, 512 pp. (in Russ.). [16] J.R. Rostrup-Nielsen, in: J.R. Anderson, M. Boudart (Eds.), Catalysis, Science and Technology, Vol. 5, Springer, Berlin, 1984, (Chapter 1). [17] US Patent 4978649, B01 J 20/20. [18] V.A. Semikolenov, Zhurnal Prikladnoi Khimii 70 (1997) 785 (in Russ.). [19] V.V. Galvita, V.A. Semikolenov, V.A. Sobyanin, in preparation.
Synthesis gas production by steam reforming of ethanol V.V. Galvita a , G.L. Semin a , V.D. Belyaev a , V.A. Semikolenov a , P. Tsiakaras b , V.A. Sobyanin a,∗ a
b
Boreskov Institute of Catalysis, Prospekt Akademika Lavrentieva 5, 630090 Novosibirsk, Russia Department of Mechanical and Industrial Engineering, University of Thessaly, Pedion Areos, 38334 Volos, Greece Received 19 January 2001; received in revised form 13 June 2001; accepted 13 June 2001
Abstract A two-layer fixed-bed catalytic reactor for syngas production by steam reforming of ethanol has been proposed. In the reactor, ethanol is first converted to a mixture of methane, carbon oxides and hydrogen over a Pd-based catalyst and then this mixture is converted to syngas over a Ni-based catalyst for methane steam reforming. It has been shown that the use of the two-layer fixed-bed reactor prevents coke formation and provides the syngas yield closed to equilibrium. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Ethanol; Steam reforming; Syngas; Two-layer fixed-bed reactor
1. Introduction Ethanol is a renewable material as it can be produced from biomass [1,2]. Bioethanol — an aqueous solution containing ca. 12 wt.% ethanol — can be used as an alternative fuel or as a feedstock for the production of chemicals. In recent years, much attention has been focused on the study of ethanol steam reforming to syngas or hydrogen-rich gas [3–8]. The process is particularly attractive because it utilizes bioethanol without distillation and produces hydrogen, which is seriously considered as a feed for fuel cells [9,10]. Thermodynamic analysis of ethanol steam reforming has shown that methane is the main reaction product at moderate temperatures, whereas higher temperatures and high water/ethanol molar ratio favor the production of syngas or hydrogen-rich gas [3,4]. Experimental studies of ethanol steam reforming have ∗ Corresponding author. Fax: +7-383-2-3432-69. E-mail address: [email protected] (V.A. Sobyanin).
been performed using conventional flow reactors with cobalt supported catalysts [7] or potassium-promoted nickel–copper supported catalysts [5,6]. The main problems during these experiments were the catalysts’ coking and formation of undesirable products such as methane, acetaldehyde, etc. In order to overcome these problems, a two-layer fixed-bed reactor has recently been proposed in order to run ethanol-to-syngas steam reforming [8]. In this reactor, ethanol is converted to acetaldehyde and hydrogen over the Cu/SiO2 catalyst. Acetaldehyde is then converted to syngas over the Ni/MgO catalyst. In the present paper, the ethanol steam reforming to syngas or hydrogen-rich gas is studied in a modified two-layer fixed-bed reactor. In contrast to the reactor used in [8], in the present reactor ethanol decomposes to methane, hydrogen and carbon oxides over the first catalyst layer and then the gas mixture produced converts to syngas over the second catalyst layer. The first layer was made of Pd-based catalyst, which was chosen based on numerous publications [11–14]
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reporting that ethanol easily decomposes over supported and bulk Pd catalysts. The second layer was made of Ni-based catalyst due to its high activity for methane steam reforming [15,16]. 2. Experimental
The compositions of the inlet and outlet gas mixtures were analyzed on-line by two gas chromatographs “Tsvet-500” (Russia) using Molecular Sieves and Porapak-Q columns and thermal conductivity detectors. The concentrations were measured within a ±5% error.
2.1. Catalysts
3. Results and discussion
Pd supported on Sibunit (a special porous carbonaceous material [17]) and industrial Ni-containing catalyst GIAP-16 for methane steam reforming [15] were used in this work. Pd supported on Sibunit (Pd/C) catalyst was prepared as described in [18]. The Pd content was 1 wt.%. The catalyst particles were spheres of size 1.2–1.5 mm, pore volume and the BET surface area were 0.74 cm3 /g and 400 m2 /g, respectively. XPS studies proved metallic Pd to form on Sibunit. According to TEM, both fresh and spent (after a 100 h operation in ethanol steam reforming) samples of the Pd/C catalyst contained Pd particles of size 40–60 Å. This catalyst will be described in more detail in a separate paper [19]. GIAP-16 containins 24–26 wt.% NiO, 55–59 wt.% Al2 O3 and 14–16 wt.% CaO. The particle size of the catalyst used in the present study ranged 1.2–1.5 mm.
3.1. Catalytic performance of Pd/C
2.2. Catalytic activity measurements The reaction of ethanol steam reforming was carried out under atmospheric pressure in a conventional flow reactor and in a two-layer fixed-bed reactor. The reactors were made of a quartz tube with i.d. 8 mm. Each layer consisted of 1 g of the catalyst mixed with 3 g of inert quartz powder. The catalyst layers were fixed by quartz wool. The distance between the two catalyst beds in the two-layer fixed-bed reactor was 100 mm. The catalyst activities were measured using two reaction mixtures: 11 vol.% C2 H5 OH+89 vol.% H2 O, and 49 vol.% C2 H5 OH + 51 vol.% H2 O. To prepare each mixture, a liquid water/ethanol solution (molar ratios 8.1/1 or 1.04/1) was supplied into a vaporizer and the vapor produced was fed in the reactor at a space velocity (WHSV) of 1600–2200 cm3 /h g. Before experiment, the GIAP-16 catalyst was reduced in situ by hydrogen for 1 h at 750◦ C. The Pd/C catalyst was used without any pretreatment.
With both feed compositions (water/ethanol molar ratios 8.1/1 and 1.04/1), only hydrogen, methane, carbon monoxide and carbon dioxide were produced on Pd/C catalyst in the temperature range 210–380◦ C. Fig. 1 demonstrates the effect of temperature on ethanol conversion and product concentrations for the inlet water/ethanol mixture with molar ratio 8.1/1. It is seen that the ethanol conversion increases with increasing temperature and attains 100% at 330◦ C. The CO concentration passes through broad maximum, whereas the CO2 , CH4 and H2 concentrations increase with increasing temperature. Analysis of the temperature dependencies of the CO, CO2 , CH4 and H2 concentrations proves that at all temperatures the concentrations obey the following equations: [H2 ] = [CH4 ] + [CO2 ]
(1)
[CH4 ] = [CO2 ] + [CO]
(2)
If so, the CH4 , CO and H2 are the primary products of the ethanol decomposition C2 H5 OH = CH4 + CO + H2
(3)
while CO2 is the secondary product and forms owing to water-gas shift reaction CO + H2 O = CO2 + H2
(4)
This suggestion is confirmed by the data presented in Fig. 2, which illustrates the effect of temperature on ethanol conversion and outlet product concentrations for the inlet water/ethanol mixture with molar ratio 1.04/1. The ethanol conversion increases with increasing temperature and attains 100% at 360◦ C. The concentrations of H2 , CO, CH4 and CO2 also increase
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Fig. 1. Temperature dependencies of ethanol conversion and product concentrations upon steam reforming of ethanol over the Pd/C catalyst. Experimental conditions: WHSV = 2200 cm3 /h g, inlet molar ratio water/ethanol = 8.1/1.
with increasing temperature. Besides, in the temperature range 240–310◦ C, no CO2 is observed among the reaction products, while the concentrations of H2 , CO and CH4 are similar. This means that only reaction (3) proceeds in this temperature interval. As the temperature increases to 310–370◦ C, CO2 appears among the reaction products, and the concentration of H2 exceeds
that of CH4 , which in its turn exceeds the concentration of CO. The concentrations of H2 , CO, CO2 and CH4 obey equations (1) and (2). This means that CO2 forms by reaction (4). Thus, the results obtained confirm that Pd/C is an active and selective catalyst for ethanol decomposition to methane, hydrogen and carbon oxides gas mixture.
Fig. 2. Temperature dependencies of ethanol conversion and product concentrations upon steam reforming of ethanol over the Pd/C catalyst. Experimental conditions: WHSV = 1600 cm3 /h g, inlet molar ratio water/ethanol = 1.04/1.
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This conclusion agrees with literature data [11–14]. Besides, Pd/C exhibited good stability as no catalyst decay was observed during 100 h on stream. The catalytic behavior of Pd/C will be discussed in more detail in a separate paper [19]. 3.2. Catalytic performance of GIAP-16 In contrast to the Pd/C catalyst, GIAP-16 produced acetaldehyde, methane, hydrogen and carbon oxides by reacting ethanol and steam and substantial amounts of coke/carbon were observed on the used catalyst. In particular, when water/ethanol mixtures (molar ratio 8.1/1 or 1.04/1) were fed to GIAP-16, a considerable carbon imbalance and increased pressure drop was observed in the temperature range 300–650◦ C. Moreover, as visual inspection showed, after a 0.5–2 h operation, the reactor was plugged with carbon. So, owing to low coking resistance, the GIAP-16 catalyst is unacceptable to run the ethanol steam reforming in the conventional flow reactor. Then, based on the idea of two-layer fixed-bed reactor, we decided to try GIAP-16 for steam reforming of the gas mixture (CH4 , CO, CO2 , H2 ) resulting from the ethanol decomposition over the Pd/C catalyst (see Section 3.1). The following section presents the results of ethanol steam reforming to syngas in the two-layer fixed-bed reactor.
3.3. Performance of two-layer fixed-bed reactor When water/ethanol mixture (molar ratio 8.1/1) was fed into the two-layer fixed-bed reactor, only H2 , CO, CO2 and CH4 were detected among the reaction products. Catalytic layers 1 and 2 in this reactor were made of Pd/C and GIAP-16, respectively. Catalytic layer 1 was operated at constant temperature 335 ± 5 K and WHSV = 2200 cm3 /h g. Reactions (3) and (4) proceeding under these experimental conditions provided a 100% conversion of ethanol to the H2 , CO, CO2 and CH4 gas mixture (see Section 3.1). The mixture produced passed to catalytic layer 2 (1 g GIAP-16), which performed the reaction of methane steam reforming in the temperature range 650–800◦ C. Fig. 3 presents the outlet concentrations of H2 , CO, CO2 , CH4 and H2 O as a function of the temperature of catalytic layer 2 upon ethanol steam reforming in the two-layer fixed-bed reactor under the specified experimental conditions. The ethanol conversion was 100% (not shown in Fig. 3). Thermodynamic equilibrium concentrations of H2 , CO, CO2 , CH4 and H2 O are also shown in Fig. 3. These values were calculated on the assumption that the equilibrium composition was controlled by the following reactions: C2 H5 OH = CH4 + CO + H2
Fig. 3. Product concentrations vs. the temperature of catalytic layer 2 upon the ethanol steam reforming in the two-layer fixed-bed reactor. Experimental conditions are specified in Section 3.3. Symbols — experiments, lines — thermodynamic equilibrium values.
V.V. Galvita et al. / Applied Catalysis A: General 220 (2001) 123–127
CO + H2 O = CO2 + H2 CH4 + H2 O = CO + 3H2 The experiment is seen to coincide with the calculated values. Note finally that neither carbon imbalance nor changes of the ethanol conversion and the outlet product concentrations were observed during the ethanol steam reforming in the two-layer fixed-bed reactor (about 100 h on stream). Thus, the data obtained prove appropriate operation of the two-layer fixed-bed reactor in the production of syngas by the ethanol steam reforming.
4. Conclusion The concept of the two-layer fixed-bed reactor seems to be quite promising for the steam reforming of ethanol to syngas. According to this concept, ethanol is first converted to the H2 , CO, CO2 and CH4 gas mixture over a suitable catalyst (for example, Pd/C) and then the mixture produced is converted to syngas over another appropriate catalyst (for example, Ni-based catalyst for methane steam reforming).
Acknowledgements The authors highly appreciate partial financial support provided by INTAS (Project No. 897).
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References [1] M. McCoy, C&EN, 7 December 1998, p. 29. [2] G.W. Barnard, D.O. Hall, Energy from renewable resources, in: H. Dellweg (Ed.), Biotechnology, Vol. 3, Vertlag Chemie GmbH, Weinheim, 1983, 593 pp. [3] K. Vasudeva, N. Mitra, P. Umasankar, S.C. Dhingra, Int. J. Hydrogen Energy 21 (1996) 13. [4] I. Fishtik, A. Alexander, R. Datta, D. Geana, Int. J. Hydrogen Energy 25 (2000) 31. [5] F.J. Marino, E.G. Cerrella, S. Duhalde, M. Jobbady, M.A. Laborde, Int. J. Hydrogen Energy 23 (1998) 1095. [6] F. Marino, M. Jobbagy, G. Baronetti, M. Laborde, Stud. Surf. Sci. Catal. 130 (2000) 2147. [7] F. Haga, T. Nakajama, H. Miya, S. Mashima, Catal. Lett. 48 (1997) 223. [8] S. Freni, N. Mondello, S. Cavallaro, G. Cacciola, V.N. Parmon, V.A. Sobyanin, React. Kinet. Catal. Lett. 71 (2000) 143. [9] Design News, 22 June 1998, p. 88. [10] G. Maggio, S. Freni, S. Cavallaro, J. Power Sources 74 (1998) 17. [11] N. Isawa, O. Yamamoto, R. Tamura, M. Nishikubo, N. Takezawa, Catal. Lett. 62 (1999) 179. [12] N. Takezawa, N. Isawa, Catal. Today 36 (1997) 45. [13] J.L. Davis, M.A. Barteau, Surf. Sci. 187 (1987) 387. [14] R. Shekhar, M.A. Barteau, Catal. Lett. 31 (1995) 221. [15] E.N. Emel’yanov (Ed.), Spravochnik Azotchika, Khimiya, Leningrad, Moscow, 1986, 512 pp. (in Russ.). [16] J.R. Rostrup-Nielsen, in: J.R. Anderson, M. Boudart (Eds.), Catalysis, Science and Technology, Vol. 5, Springer, Berlin, 1984, (Chapter 1). [17] US Patent 4978649, B01 J 20/20. [18] V.A. Semikolenov, Zhurnal Prikladnoi Khimii 70 (1997) 785 (in Russ.). [19] V.V. Galvita, V.A. Semikolenov, V.A. Sobyanin, in preparation.