【摘要】 采用程序升温脱附(TPD)、真空重量吸附、ESCA和正己烷的裂化反应研究了水热处理对ZSM-5沸石表面性质及催化性能的影响。不同Si/Al比的ZSM-5沸石均有两类不同酸强度的TPD峰。随着水热处理温度升高,较强酸峰Ⅱ比较弱酸峰Ⅰ下降快,同时单位晶胞的酸性中心数、表面积、表面硅铝比和环己烷的吸附量均下降,正己烷裂化活性上随之下降。水热处理前,不同Si/Al比的ZSM-5沸石晶胞中酸中心数相差甚大,730℃水热处理后,它们的酸中心数接近相同,其较强酸峰Ⅱ消失。更多还原

【Abstract】 The effect of high temperature steam treatment on the surface property and the catalytic activity of HZSM-5 zeolite has been studied by TPD, ESCA/SAM, vacuum weight adsorption of n-hexane and cyclohexane as well as cracking reaction of n-hexane. In the TPD of adsorbed ammonia, two TPD peaks are found for HZSM-5 zeolites with different Si/Al ratios. Peak I and II denote weaker acid sites and stronger acid sites respectively. When the temperature of steam treatment is increased, the decrease of the amount of stronger acid sites is quicker than weaker acid sites, TM of peak I shifts to the higher temperature side and TM of peak II to the lower temperature side. The peak II disappears as the treating temperature is reached to 730℃.The number of acid sites in each unit cell, surface area, surface Si/Al ratio and the amount of cyclohexane adsorbed decrease as the steam treating temperature is increased. The number of acid sites of HZSM-5 zeolites with different Si/Al ratios is quite different before treatment, but their number of acid sites is nearly the same after steam treated at 730℃.The cracking activities for n-hexane over HZSM-5 zeolite decrease as the steam treating temperature is increased, but the stabilities increase obviously.更多还原