铈改性Silicalite-1分子筛催化剂上甲醇制丙烯反应性能研究

采用浸渍法制备了Ce改性的Silicalite-1分子筛催化剂,利用XRD、N2吸脱附、Py-FTIR和NH_3-TPD等手段对催化剂进行了表征;针对甲醇转化制丙烯(MTP)反应,在常压、450℃和质量空速为9.6 h-1的反应条件下,利用连续流动固定床微型反应评价装置,考察了CeO_2负载量对CeO_2/Silicalite-1催化性能的影响。结果表明,与HZSM-5分子筛(SiO_2/Al_2O_3(molar ratio)=200)相比,Silicalite-1分子筛具有更高的丙烯选择性和催化稳定性。Ce的引入可有效调节Silicalite-1分子筛的酸性质和孔结构;合适浓度的Ce改性处理(CeO_2负载量(质量分数)为5.0%)使得Silicalite-1的强酸量降低,其丙烯选择性(质量分数)和催化稳定性分别由原来的31.9%和51 h增加到38.2%和72 h。

Catalytic performance of cerium modified Silicalite-1 molecular sieves in the conversion of methanol to propene

A series of cerium modified Silicalite-1 molecular sieves were prepared by incipient wetness impregnation and used as the catalysts in the conversion of methanol to propene (MTP). The cerium modified Silicalite-1 catalysts were characterized by X-ray diffraction (XRD), N₂ sorption, pyridine adsorption Fourier transform infrared spectroscopy (Py-FTIR) and temperature-programmed desorption of NH₃ (NH₃-TPD); their catalytic performance in MTP was evaluated in a continuous flow fixed-bed micro-reactor at atmospheric pressure and 450℃, with a methanol weight hourly space velocity (WHSV) of 9.6 h^-1. The results showed that Silicalite-1 exhibits superior catalytic performance in MTP in terms of catalytic stability and selectivity to propene, in comparison with the HZSM-5 zeolite with a SiO₂/Al₂O₃ molar ratio of 200. The introduction of Ce can effectively adjust the acid properties and pore structure of Silicalite-1; modification with an appropriate concentration of Ce can reduce the amount of strong acid sites and then enhance the catalytic performance of Silicalite-1 in MTP. Over the cerium modified Silicalite-1 with a CeO₂ content of 5.0%, the selectivity to propene is increased from 31.9% to 38.2% and the catalytic lifetime is extended from 51 to 72 h, in comparison with those over the parent Silicalite-1.