Correlation of performance and structure of supported rhenium catalysts for methanol selective oxidation
- 化学化工－已发表论文 
Supported Re catalysts were prepared by impregnation of ammonium perrhenate precursor on oxide supports, followed by calcination at 673 K in He steam. Iron-oxides and V2O5 supported Re catalysts showed a higher activity and selectivity for the catalytic methanol oxidation to dimethoxymethane [3CH(3)OH + (1/2)O-2-->CH2(OCH3)(2)+2H(2)O]. The selectivity was as high as 90%-94% (molar fraction) at 513 K. The highest. reaction rate of 450 mmol. h(-1).g(-1) Re on alpha-Fe2O3 supported Re catalysts was achieved with the Re loading weight of 2% (mass fraction). The reaction rate gradually decreased with the increase of Re loading weight. Calcination of ammonium perrhenate alone at 673 K in He gave monoclinic ReO2 as a main produdt. However, the application of the iron-oxide may prevent Re7+ from reducting to Re4+ during the calcination at 673 K in He in the case of proper Re loading weight probably through the interaction of ammonium perrhenate with the supports, leading to the growth of Re6+ on the catalyst surface. Above the monolayer loading weight of ReO3, there was coexistence of Re6+ and Re6+ on the catalyst surface. A redox mechanism between Re6+ and Re4+ species on the catalyst surface was proposed to be responsible for the high performance in the methanol selective oxidation to dimethoxymethane.