Characterization of silica-supported ruthenium catalysts by hydrogen chemisorption and nuclear magnetic resonance of adsorbed hydrogen

• Published in: Journal of catalysis Vol. 118; no. 1; pp. 238 - 254
• Main Authors: Wu, X., Gerstein, B.C., King, T.S.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.07.1989; Elsevier
• Subjects: 400201 - Chemical & Physicochemical Properties; CATALYST SUPPORTS; CHALCOGENIDES; CHEMICAL REACTIONS; CHEMISORPTION; Chemistry; COMPARATIVE EVALUATIONS; CRYSTAL STRUCTURE; ELEMENTS; Exact sciences and technology; General and physical chemistry; HYDROGEN; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; MAGNETIC RESONANCE; METALS; MINERALS; NONMETALS; NUCLEAR MAGNETIC RESONANCE; OXIDE MINERALS; OXIDES; OXYGEN COMPOUNDS; PARTICLE SIZE; PLATINUM METALS; RELAXATION; RESONANCE; RUTHENIUM; SEPARATION PROCESSES; SILICA; SILICON COMPOUNDS; SILICON OXIDES; SIZE; Solid-gas interface; SORPTION; SPIN-LATTICE RELAXATION; Surface physical chemistry; SURFACE PROPERTIES; TRANSITION ELEMENTS; Inorganic adsorbate; Ruthenium; Hydrogen; Adsorption isotherm; NMR spectrometry; Inorganic adsorbent; Experimental study; Physisorption; Silica; Supported catalyst; Gas solid adsorption; Gas solid interface; Physical method
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/0021-9517(89)90314-X

Adsorbed hydrogen on four silica-supported ruthenium catalysts was measured quantitatively by proton magnetic resonance (PMR). The PMR technique revealed two distinct adsorbed states of hydrogen on the metal: reversible and irreversible. The results from PMR and those from conventional hydrogen chemisorption measurements were compared directly. The observed discrepancy between the PMR and volumetric techniques in the case of total adsorption is attributed to spillover of reversibly adsorbed hydrogen from ruthenium onto the silica support. Good agreement was obtained between the two techniques in the case of irreversible adsorption. The relatively narrow line of PMR spectra on the reversibly adsorbed hydrogen indicates rapid motion for this state of hydrogen on ruthenium surfaces. The variation of spectral lineshift and of the spin-lattice relaxation times for the adsorbed hydrogen with ruthenium particle size suggests a stronger interaction between the adsorbed hydrogen and defect-like ruthenium adsorption sites. The results from PMR intensity measurements also suggest that the reversibly adsorbed hydrogen is at least in part associated with the defect-like ruthenium adsorption sites.