Simultaneous isomerization of n-heptane and hydrogenation of benzene over bimetallic PtMe/Beta catalysts in the absence and presence of sulfur

摘要

Bifunctional bimetallic PtMe/Beta catalysts (Me = Pd, Ir, Ru) have been prepared and studied for the simultaneous isomerization of n-heptane and hydrogenation of benzene. In the absence of sulfur, PtPd samples were less selective to iso-C_7 than PtIr and PtRu. The extent of cracking increased with the Pd concentration in PtPd/Beta. The conversion of benzene was 100% for all catalysts. In the presence of 200 ppm sulfur, the n-C_7 conversion decreased while the cracking selectivity increased. The relative decrease of activity was lower for PtPd catalysts, suggesting a higher sulfur resistance as compared to PtIr and PtRu. Benzene conversion was much less affected by sulfur, but there was a loss of activity for isomerization of cyclohexane into methylcyclopentane. The better sulfur resistance of PtPd samples may arise from a stabilization of partially charged Pt~(δ+) species by interaction with Pd, which could be associated with a lower reducibility of Pt~(2+) in presence of Pd, as observed by TPR.