论文部分内容阅读
程序升温热脱附法测定HZSM-5和HM分子筛吸附氨的程脱谱均有两个峰。HZSM-5的峰Ⅰ和峰Ⅱ的T_M分别为199和418℃,HM的为207和526℃,它们代表了两种强弱不同的吸附中心。通过分析脱附的氨量,计算了强弱两种吸附中心数,并与两种分子筛中所含的理论酸中心数作了比较,得到了与两个峰相应的酸中心性质的信息。 另外用电子计算机模拟热脱附曲线的方法,测定了HZSM-5和HM分子筛上氨的脱附活化能E_d与覆盖度θ的函数关系,提出用E_d和E_d～θ表征酸强度和酸强度分布。结果表明:HM的强酸中心的强度较HZSM-5强,而且酸强度分布更不均匀。但两种分子筛的弱酸中心的性质从能量上看很相似,也较强酸中心均匀。
Temperature programmed desorption of HZSM-5 and HM zeolites adsorbed ammonia stripping spectrum has two peaks. The T_M of peak I and peak II of HZSM-5 were 199 and 418 ° C, respectively, and those of HM were 207 and 526 ° C, respectively. They represented two kinds of adsorption centers with different strengths and weaknesses. By analyzing the amount of ammonia desorbed, the number of strong and weak adsorption centers was calculated and compared with the number of theoretical acid centers contained in the two molecular sieves, and the information of the acid centers corresponding to the two peaks was obtained. In addition, the relationship between the activation energy E_d and the coverage θ of ammonia on HZSM-5 and HM zeolites was also investigated by computer simulation of the thermal desorption curve. It was proposed that the acid and acid intensity distributions were characterized by E_d and E_d ~ θ . The results show that the strong acid sites of HM are stronger than HZSM-5, and the distribution of acid intensity is more uneven. However, the properties of the weak acid centers of the two molecular sieves are very similar in energy and are also more uniform in the acid sites.