Elementary steps in CO hydrogenation on Rh catalysts supported on ZrO[sub 2] and Mo/ZrO[sub 2]

Journal Article · Fri Apr 01 04:00:00 EST 1994 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1994.1080· OSTI ID:7036612

Guglielminotti, E; Giamello, E ^[1]; Pinna, F; Strukul, G ^[2]; Martinengo, S; Zanderighi, L ^[3]

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1. Universita di Torino (Italy)
2. Univ. di Venzia Dorsoduro (Italy)
3. Universita di Milano (Italy)

The first steps of CO activation and hydrogenation reactions on Rh catalysts have been studied in order to identify possible intermediates in the reaction pathway to C[sub 1] compounds. Rh catalysts were prepared by supporting Rh[sub 4](CO)[sub 12] or on ZrO[sub 2] after adsorption of Mo(CO)[sub 6]. The Rh content on all catalysts was 1% (w/w) while the Mo/Rh atomic ratio ranged from 0.0 to 2.0. The supported catalysts were decomposed in H[sub 2] at 523 K (LTR) and at 773 K (HTR). The samples were characterized by TEM, EPR, FTIR, and chemisorption of H[sub 2], O[sub 2], and CO. The catalytic activity was tested in the CO hydrogenation reaction at 493 K and 101 kPa. The total CO conversion increased with Mo/Rh ration on LTR catalysts while it was unaffected on HTR catalysts. By increasing the Mo content the amount of CO[sub 2] formed increased significantly. The CO carbon efficiency to methane and total hydrocarbon without CO[sub 2], did not depend on the Mo/Rh ratio for LTR catalysts while a constant decrease was observed for HTR catalysts. The carbon efficiency to methanol increased with the Mo content both on LTR and HTR catalysts, and that to ethanol changed with the Mo/Rh ratio and the activation temperature. The environment of Rh particles is strongly modified by the presence of Mo as evidenced by modification of the IR spectrum of chemisorbed CO both in the linear and in the bridged Rh-CO region. On the basis of the experimental results the reaction paths to CO[sub 2], CH[sub 3]OH, and CH[sub 4], and the effect of MoO[sub 3] promoter are discussed in detail. The methane formation through different pathways involving a bicarbonate and/or a formate intermediate are presented. 80 refs., 13 figs., 1 tab.

• OSTI ID: 7036612
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 146:2; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

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ABSORPTION SPECTROSCOPY
CARBON COMPOUNDS
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CHALCOGENIDES
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MOLYBDENUM COMPOUNDS
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OXIDES
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SORPTIVE PROPERTIES
SPECTROSCOPY
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ZIRCONIUM OXIDES