The effect of lanthanum promoter on the selectivity of Pd/zeolite-X in methanol synthesis

Journal Article · Sun Apr 01 04:00:00 EDT 1990 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(90)90286-S· OSTI ID:6404723

Choudary, B M ^[1]; Matusek, K; Bogyay, I; Guczi, L ^[2]

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1. Regional Research Lab., Hyderabad (India)
2. Institute of Isotopes, Budapest (Hungary)

The promoting effect of various amounts of lanthanum on Pd/zeolite-X in enhancing selectivity in CO hydrogenation toward methanol/oxygenates has been investigated. The catalysts were characterized by temperature-programmed reduction, O{sub 2}-H{sub 2} titration, and temperature-programmed desorption. The dispersion and H{sub 2} chemisorption of Pd/zeolite-X catalysts were almost unchanged on La promotion. The virtually unchanged chemisorption capacity of the Pd/zeolite-X catalysts on La promotion is attributed to the cationic exchange method adopted to introduce La after Pd introduction into the zeolites. The La{sub 2}O{sub 3} formed during calcination was partially reduced during reduction with hydrogen due to its contact with palladium. PdLaO{sub x} entities formed thereby trigger the activation of coordinated CO/H{sub 2} and facilitate the hydrogenation of CO to methanol/oxygenates at low temperature. Thus, the Pd sites responsible for methanol synthesis are stabilized by La at low and high pressures. Dimethyl ether, dominant for low La content Pd/zeolite-X catalysts, may be ascribed to the acid sites developed, but other mechanisms cannot be ruled out. The effect of the zeolite matrix lies in the stabilization of PdLaO{sub x} entities, but otherwise it behaves in a similar fashion to other supports. The zeolite lattice, however, ensures the maintenance of small PdLaO{sub x} particles. The turnover frequency values obtained with the optimum La promotion on Pd/zeolite-X are consistent with the reported values observed on Pd/La{sub 2}O{sub 3} catalysts. The zeolites are therefore potential alternative supports in the preparation of suitable bimetallic systems.

• OSTI ID: 6404723
• Journal Information: Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 122:2; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

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ALCOHOLS
BIMETALS
CALCINATION
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
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METHANATION
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