Effects of pretreatments on the catalytic hydrogenation of dimethyl maleate over Ru/Al2 O3 catalyst
Ru / Al2 O3 catalyst with Ru mass fraction of 1. 0% was prepared via adsorption-precipitation method. The catalysts obtained with various pretreatments were characterized by H2-TPR,XRD and TEM. The effects of the pretreatment condition on the catalytic performance of the catalysts were investigated by using selective hydrogenation of dimethyl meleate(DMM)to dimethyl succinate(DMS)as a probe reac-tion. The results showed that the higher the calcination temperature,the lower the catalyst activity;and the activity of the catalyst prepared via direct reduction was better than that of the catalyst obtained by calci-nation-reduction process in the air. Under the reaction condition of methanol as the solvent,reaction tem-perature 70 ℃ ,and reaction pressure 1. 0 MPa,DMM conversion and the selectivity to DMS were both nearly 100% over Ru / Al2 O3 catalyst obtained by direct reduction,while DMM conversion was nearly 25% over Ru / Al2 O3 catalyst prepared by calcination-reduction process in the air in the same time and had little change as the time prolonged. The results of characterization indicated that the better perform-ance of Ru / Al2 O3 catalyst prepared via direct reduction process could be ascribed to the better dispersion of Ru and the calcination process caused the sintering of Ru which was responsibe for the catalytic result of the calcination-reduction sample.
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