Effects of steam on the structure of Pt-Sn/ZnAl2O4 catalysts

Steam is widely used in catalytic dehydrogenation process([1-6]). It has been considered as a dilluent, an oxidant, a coke remover and a heating medium([2 3]). However, it possibly interacts with the catalyst and influence on the performance of the catalyst. For example, Yang et al ([5, 6]) found that steam modified the surface of iron oxide in the oxidative dehydrogenation of butene. On these catalysts, hydroxyl surface is more active than their corresponding oxide surface. For catalytic dehydrogenation of light alkane, some processes have been developed and well documented. It has been reported that Phillips Star process is operated with steam dilution which improves conversion, suppresses coke formation and avoids high pre-heating temperature. Under operation and regeneration, the promoted platinum supported on zinc aluminate spinel has good activity and stability([3]). So far, however, study about Light alkane dehydrogenation in the presence of steam is scarce. Recently, we reported our finding that steam modified the catalytic performance of Pt-Sn catalysts in the dehydrogenation of propane([7]). Significant initial activity increase was observed over Pt-Sn/ZnAl2O4 and Pt-Sn/MgAl2O4, upon the introduction of steam to the reactor. In the present study, the effect of steam on the structure of Pt-Sn/ZnAl2O4 is reported.