Investigación del mecanismo de adsorción-reacción de metanol sobre óxidos de galio por espectroscopia molecular y análisis TPSR in-situ

SEBASTIÁN E. COLLINS; MIGUEL A. BALTANÁS; ADRIAN L. BONIVARDI; LAURA E. BRIAND; LUIS A. GAMBARO

Santa Fe, Argentina

Congreso; XIV Congreso Argentino de Catálisis; 2005

Insights regarding methanol chemisorption and surface reaction over bulk gallium oxides (alpha, beta and gamma phases) were obtained through the investigation of the surface intermediate species and product desorption during the surface reaction of adsorbed methoxy species. Methanol chemisorbs both molecularly over Lewis acid sites and dissociatively over Ga3+-OH sites as methoxy (CH3O) species at 373 K. The quantification of the amount of chemisorbed methanol allowed to determine that the number of available surface active sites per unit area (NS) is 1-2 mmol m-2 for a fully oxidized oxide. However, reduced oxides drastically diminish their NS to ~ 0.2 mmol m-2. Methoxy species are further oxidized towards methylenbisoxi (H2COO) and formate (HCOO) species upon heating to 473 K. Surface formate species decompose towards CO(g) and CO2(g) at ~ 600 K, and regenerate OH and GaH species over the surface.