氯氧化处理对Pt-Sn-Na/ZSM-5丙烷脱氢催化剂再生性能的影响

Effect of oxychlorination treatment on the catalytic properties of the regenerated Pt-Sn-Na/ZSM-5 catalyst for propane dehydrogenation

分别采用烧炭法和烧炭-氯氧化法对积炭后的Pt-Sn-Na/ZSM-5丙烷脱氢催化剂进行再生(以下分别简称试样1和试样2)。借用X射线衍射法、透射电子显微镜、H2-程序升温还原法、NH3-程序升温脱附法等分析了催化剂物理化学性质,并在固定床反应装置上,考察了催化剂的丙烷脱氢性能。结果表明:试样1的Pt分散度明显下降;氯氧化处理可有效促进烧炭后催化剂Pt的再分散,并且增加了催化剂表面酸性,因此,试样2的丙烷转化率较高,但丙烯选择性较低;此外,由于氯氧化处理中水蒸气的存在,导致催化剂的机械强度下降,以及Pt-Sn合金的生成,因此,试样2经二次再生后,丙烯收率明显降低。

Pt- Sn- Na / ZSM- 5 catalyst of carbon deposit for propane dehydrogenation were regenerated by oxilization and oxilization- oxychlorination methods（ referred to sample 1 and sample 2,respectively）. The physicochemical properties of the catalysts were characterized by X- ray diffraction,transmission electron microscope,H2- temperature programmed reduction method,NH3- temperature programmed stripping method,and so on. The propane dehydrogenation performance of catalyst was investigated in a fixed bed reactor. The results showed that the Pt dispersion of sample 1 declined obviously,while the oxychlorination treatment could effectively improve the redispersion of Pt after the coke burning,and increased the amount of acid of sample2. Therefore,the propane conversion of sample 2 increased and the propene selectivity decreased. Besides,the existence of stream during the oxychlorination treatment led to the decrease of mechanical strength and formation of Pt- Sn alloy. Consequently,the propene yield of sample 2dropped obviously after the second regeneration.