H2 production by steam reforming of methanol over Cu/ZnO/Al2O3 catalysts: transient deactivation kinetics modeling

Agarwal, Vandna; Patel, Sanjay; Pant, Kamal K.

doi:10.1016/j.apcata.2004.10.026

Cited by 106 publications

(58 citation statements)

References 14 publications

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“…Many studies [16][17][18][19][20][21][22][23][24][25][26][27][28] have focused on copper-based catalysts which exhibit a high reactivity and favorable selectivity to CO 2 and H 2 . However, the Cu-based catalysts can readily undergo deactivation at high temperature [29] (C553 K) due to metal sintering and their pyrophoric nature makes them undesirable for safe and efficient operation of PEM fuel cells.…”

Section: Introductionmentioning

confidence: 99%

CO/FTIR Spectroscopic Characterization of Pd/ZnO/Al2O3 Catalysts for Methanol Steam Reforming

et al. 2008

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An as-synthesized 8.8wt% Pd/ZnO/Al 2 O 3 catalyst was either pretreated under O 2 at 773 K followed by H 2 at 293 K or under H 2 at 773 K to obtain, respectively, a supported metallic Pd°catalyst (Pd°/ZnO/Al 2 O 3 ) or a supported PdZn alloy catalyst (PdZn/ZnO/Al 2 O 3 ). Both catalysts were studied by CO adsorption using FTIR spectroscopy. For the supported PdZn alloy catalyst (PdZn/ ZnO/Al 2 O 3 ), exposure to a mixture of methanol and steam, simulating methanol steam reforming reaction conditions, does not change the catalyst surface composition. This implies that the active sites are PdZn alloy like structures. The exposure of the catalyst to an oxidizing environment (O 2 at 623 K) results in the break up of PdZn alloy, forming a readily reducible PdO with its metallic form being known as much less active and selective for methanol steam reforming. However, for the metallic Pd°/ZnO/ Al 2 O 3 catalyst, FTIR results indicate that metallic Pd°can transform to PdZn alloy under methanol steam reforming conditions. These results suggest that PdZn alloy, even after an accidental exposure to oxygen, can self repair to form the active PdZn alloy phase under methanol steam reforming conditions. Catalytic behavior of the PdZn/ZnO/ Al 2 O 3 catalyst also correlates well with the surface composition characterizations by FTIR/CO spectroscopy.

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Section: Introductionmentioning

confidence: 99%

CO/FTIR Spectroscopic Characterization of Pd/ZnO/Al2O3 Catalysts for Methanol Steam Reforming

et al. 2008

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“…Liu et al [18] removed up to 1.7 wt.% coke from their Cu/CeO 2 catalyst by re-calcination in air and again reached the initial activity. Coke formation was also observed by XPS and even fitted with a kinetic model for a Cu/ZnO/Al 2 O 3 catalyst by Agarwal et al [39]. As a fourth reason, a change in the oxidation state of copper from Cu(II) to Cu(0) was made responsible for catalyst deactivation by Choi et al [17], who observed the copper reduction with XPS during the first 100 h of operation of their Cu/ZnO/Al 2 O 3 -catalyst.…”

Section: Catalyst Agingmentioning

confidence: 99%

Steam reforming of methanol over copper-containing catalysts: Influence of support material on microkinetics

Frank

Jentoft

Soerijanto

et al. 2007

Journal of Catalysis

181

135

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Steam reforming of methanol (SRM) was investigated over copper-containing catalysts supported on four different oxides and mixed oxides: Cu/ZnO/Al 2 O 3 , Cu/ZrO 2 /CeO 2 , Cu/SiO 2 and Cu/Cr 2 O 3 /Fe 2 O 3 . After observing slight differences in the way of catalyst aging and experimental exclusion of mass transport limitation effects, a detailed kinetic study was carried out at 493 K. The dependence of the reaction rate on the molar ratio of methanol and water was determined as well as the influence of addition of inert nitrogen and the main reaction products hydrogen and carbon dioxide to the reactant mixture. Although there were remarkable differences in the catalytic activity of the samples, the main mechanistic steps reflected in the rate law appeared to be similar for all catalysts. The reaction rate is mainly determined by the methanol partial pressure, whereas water is not involved in the rate determining step, except over Cu/Cr 2 O 3 /Fe 2 O 3 , where several differences in the chemistry were observed. Hydrogen and carbon dioxide were found to inhibit the reaction. These results were confirmed by a DRIFTS study at 493 K using an equimolar reactant mixture and an excess of 4:1 of water and methanol, respectively. The same surface species could be identified on each catalyst but neither kinetic modelling nor the DRIFTS spectra could give a clear answer if the reaction pathway occurs via a dioxomethylene or a methyl formate species as intermediate. Similar activation energies of SRM confirm the assumption, that the surface chemistry of SRM over copper-based systems is independent of the catalyst support material.

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“…The catalyst deactivation is mainly associated with the thermal sintering of small copper particles leading to a reduction of active surface area [53e55], the change in the oxidation state of copper from its oxidized form (Cu 2þ ) to the metallic form (Cu 0 ) [4], the variation in Cu þ /Cu 0 molar ratio [11,26e28] and the deposition of coke on the catalyst surface [56,57]. The continuous activity decrease in our long time on stream tests can be correlated to the formation of the reduced copper phases, namely Cu 0 and Cu2O.…”

Section: Discussionmentioning

confidence: 99%

Methanol steam reforming behavior of copper impregnated over CeO 2 –ZrO 2 derived from a surfactant assisted coprecipitation route

Das

Llorca

Domínguez

et al. 2015

International Journal of Hydrogen Energy

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H2 production by steam reforming of methanol over Cu/ZnO/Al2O3 catalysts: transient deactivation kinetics modeling

Cited by 106 publications

References 14 publications

CO/FTIR Spectroscopic Characterization of Pd/ZnO/Al2O3 Catalysts for Methanol Steam Reforming

CO/FTIR Spectroscopic Characterization of Pd/ZnO/Al2O3 Catalysts for Methanol Steam Reforming

Steam reforming of methanol over copper-containing catalysts: Influence of support material on microkinetics

Methanol steam reforming behavior of copper impregnated over CeO 2 –ZrO 2 derived from a surfactant assisted coprecipitation route

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