改性HZSM-5分子筛对二甲醚制丙烯反应的影响

Effect of modification of HZSM-5 on dimethyl ether conversion to propylene

分别采用水热处理和等体积浸渍法对制备的HZSM-5分子筛进行改性,并在连续流动固定床反应器上考察了其用于二甲醚制丙烯(DTP)反应的催化性能,同时考察了CO2作反应气氛对改性催化剂用于DTP的影响。结果表明:在400℃,常压,GHSV=1440h-1,n(DME)∶n(N2)=1∶5条件下,水热改性HZSM-5分子筛比未改性的寿命有所增加,但降低了低碳烯烃的选择性;CaO改性HZSM-5能够提高催化剂寿命,增加低碳烯烃的选择性,并有效抑制了低碳烷烃的选择性。此外CO2气氛对于DTP过程中延缓积碳的生成速率有良好的效果。

A HZSM-5 zeolite was prepared and modified by hydrothermal treatment and incipient wet impregnation with calcium nitrate solution,respectively.Their catalytic properties for dimethyl ether conversion to propylene（DTP） and the effects of dilution gases on the reaction were investigated in a continuous flow fixed bed reactor.The results showed that under the reaction conditions of 400 ℃,GHSV=1 440 h-1,nitrogen as dilution gas and n（DME）/n（N2）=1：5,the catalyst hydrothermally treated had better stability but lower selectivity to light olefins and the catalyst modified with calcium oxide had better stability and higher selectivity to light olefins but lower selectivity to light alkanes than the unmodified HZSM-5 catalyst;under the same conditions but carbon dioxide was used to substitute nitrogen as dilution gas,Ca-HZSM-5 catalyst exhibited better stability.