Producion Of Hydrogen Via Reforming Of Methanol Over Au/TiO₂Catalysts

Selective production of hydrogen by reforming of methanol over Au/TiO2catalysts, prepared by a deposition-precipitation method, was studied. Effects of preparation condition and reaction condition on the catalytic activity have been investigated and the catalysts were characterized by XRD, TEM, and XPS analyses.The study shows that the preparation condition has great influence to the catalytic activity of Au catalysts, the catalysts shows better performance when the gold loading reaches to5wt%, the uncalcined catalysts which dried at100℃exhibited highest activity, and the addition promoter of NiO and La2O3can enhance the catalytic activity of steam reforming of methanol over Au/TiO2catalysts, and the addition of La2O3promoter can decrease the production of CO and CH4evidently, and can increase the hydrogen selectivity; when the H2O/CH3OH molar ratio is1.0, weight hourly space velocity (WHSV) reaches to3.42h-1reaction temperature is in the range of250℃, the production of hydrogen via steam reforming of methanol over Au-La2O3/TiO2shows best performance, and the catalysts shows good stability when it is reviewed after180hours’reaction. On autothermal reforming reaction of methanol were investigated the catalysts showed best performance with the Boiloff temperature reaching to90℃and the reaction temperature rising to200℃, When the O2/CH3OH molar ratio in the feed is0.3, the Au-NiO/TiO2catalyst showed good activity. XRD observations show that no diffraction signals of gold is detected, because gold is highly dispersed on the support or the particle size is smaller than5nm; TEM observations show that the Au/TiO2catalysts exhibit hemispherical gold particles, which are strongly attached to the support at their flat planes, and in addition of NiO, La2O3promoter can improve the dispersion of nanometer TiO2support, and the gold particles becomes smaller and their mean particle size is about2～3nm. After180hours’reaction gold particles of Au-La2O3/TiO2catalytic not agglomerated. XPS analyses demonstrate that in uncalcined catalysts gold existed in three different states:metallic gold(Au0),non-metallic gold (Aud+)and (Au2O3), and in catalyses10%H2/90%N2activated6h at300℃only in metallic state(Au0), and in catalyses reacted180h at250℃gold existed in three different states too,(Au0、Au2O3and Aud+).