异丁烷脱氢制异丁烯反应过程Pt-Sn-K/γ-Al_2O_3催化剂的失活分析

Deactivation reason analysis of Pt-Sn-K/γ-Al_2O_3 catalysts during the dehydrogenation of isobutane to isobutylene

研究了Pt-Sn-K/γ-Al2O3催化剂在异丁烷脱氢-器内再生循环过程中脱氢反应性能,采用N2物理吸附、CO脉冲吸附、NH3-TPD和TG对催化剂进行表征,提出了催化剂的失活原因。结果表明,新鲜Pt-Sn-K/γ-Al2O3催化剂上异丁烯初始收率为39.5%,脱氢反应24 h后异丁烯收率降至20.6%。经2次脱氢-再生循环后,催化剂上异丁烯收率降至11.1%,72 h反应结束时异丁烯收率降至7.9%。积炭覆盖催化剂的活性位是导致催化剂失活的主要原因。Pt烧结及Pt-Sn合金形成使催化剂上Pt分散度降低,导致再生后催化剂活性明显下降。

The dehydrogenation performance of Pt-Sn-K/γ-Al2O3 catalysts during the isobutane dehydrogenation-in-situ regeneration cycles was investigated.The catalysts were characterized by N2 physisorption,CO pulse chemisorption,NH3 temperature-programmed desorption and thermogravimetry,and their deactivation reasons were proposed.The results showed that isobutylene yield over fresh Pt-Sn-K/γ-Al2O3 catalyst was 39.5％ and decreased to 20.6％ after reaction for 24 h.After two dehydrogenation-regeneration cycles,isobutylene yield over the catalyst was 11.1％ and decreased to 7.9％ when the 72 h reaction was completed.Coking which covered the active sites of the catalysts was the main cause of the catalyst deactivation during the dehydrogenation reaction.Pt sintering and formation of Pt-Sn alloy,which reduced Pt dispersion on the catalysts,led to obvious decrease of the regenerated catalyst activity.