Hydrogen adsorption and hydrogen-deuterium equilibration on sulfided ruthenium and bulk ruthenium sulfide catalysts

Journal Article · Sat Apr 01 04:00:00 EST 1989 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(89)90104-8· OSTI ID:6224840

Lu, K; Kuo, Y J; Tatarchuk, B J ^[1]

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1. Auburn Univ., AL (USA)

The effect of presulfidization on hydrogen adsorption over ruthenium catalysts has been studied using volumetric adsorption and H{sub 2}-D{sub 2} equilibration. On reduced ruthenium catalysts (101 kPa of H{sub 2} at 673 K for 8 h) 10.2 {mu}mol of H{sub 2}/M{sub 2} of ruthenium (measured at 373 K) was irreversibly adsorbed, the activation energy for adsorption was negligible and the initial heat of adsorption was estimated to be between {minus}109 and {minus}126 kJ/mole H{sub 2}. On mildly sulfided ruthenium catalysts (101 of kPa 10% H{sub 2}S/H{sub 2} at 673 K for 2 h, S{sub a}/Ru{sub (s)} = 0.25) both reversible and irreversible hydrogen adsorption were suppressed at temperatures below 473 K. Results of H{sub 2}-D{sub 2} equilibration kinetics on these catalysts (508 {le} T {le} 623 K) revealed an activation energy of 71 {+-} 2 kJ/mole. On extensively sulfided ruthenium catalysts (101 kPa of 100% H{sub 2}S at 673 K for 2 h, i.e., crystalline RuS{sub 2} at the surface) partial restoration of the H{sub 2} adsorption capacity was observed (6.5 {mu}mol/m{sup 2} at 373 K). H{sub 2}-D{sub 2} exchange rates at 573 K were Ca. two orders of magnitude faster than those over mildly sulfided samples. The activation energy for hydrogen adsorption was 32 {+-} 2 kJ/mole (on RuS{sub 2}-like surfaces) and the heat of adsorption was calculated to be {minus}269 kJ/mole H{sub 2}. It is suspected that this large heat of adsorption may result in higher hydrogen coverages at HDS reaction conditions. The above noted differences in hydrogen accommodation provide a unique means for understanding the selectivity toward hydrogenated products which extensively sulfided ruthenium catalysts possess. 28 refs.

• OSTI ID: 6224840
• Journal Information: Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 116:2; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

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ADSORPTION HEAT
CATALYSTS
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