水蒸气对PtSn/ZnAl_2O_4催化剂结构的影响(英文)

Effects of Steam on the Structure of Pt-Sn/ZnAl_2O_4 Catalysts

利用X-射线衍射研究了经氢还原及还原后又经高温水蒸气处理的PtSn／ZnAl2O4催化剂，结果表明，催化剂的相结构是Sn载量的函数．还原态的Pt／ZnAl2O4催化剂中Pt以金属态存在，Pt／Sn原子比为1：1、1：3及1：10的PtSn／ZnAl2O4催化剂还原后分别生成PtZn、PtSn、尽Sn及Pt物相；高温水蒸气处理对Pt／ZnAl2O4样品的相结构及Pt晶粒尺寸无明显影响，但却使Ptsn／ZnAl2O4催化剂的相结构发生显著变化；对于1：l及1：3的Ptsn／ZnAl2O4，水蒸气使各自还原态中的PtZn、PtSn合金重构为Pt3Sn合金，同时使1：10PtSn／ZnAl2O4的民β-Sn及Pt物相消失，而生成了新的PtSn合金相．

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.