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用静态程序升温热脱附方法研究了不同热处理条件对HZSM-5分子筛的酸性和催化活性时影响。测得了不同焙烧温度和不同抽空温度下氨在HZSM-5上的热脱附谱,计算了测定条件下所相应的HZSM-5的表面酸中心数。结果表明,在HZSM-5表面上存在的两种强弱不同的酸中心随热处理温度而变化的趋势是一致的。在小于650℃时,焙烧温度对异构化的活性中心的酸强度分布影响不大。不同焙烧温度的HZSM-5上邻二甲苯异构化活性与酸中心数有对应的关系,它们随焙烧温度的变化趋势颇为相似。
The effects of different heat treatment conditions on the acidity and catalytic activity of HZSM-5 zeolite were studied by static temperature programmed desorption. The thermal desorption spectra of ammonia on HZSM-5 at different calcination temperatures and different evacuation temperatures were measured. The number of acid sites on the surface of HZSM-5 was calculated. The results show that there is a consistent trend that the two acid sites with different strengths and weaknesses on the surface of HZSM-5 vary with the heat treatment temperature. When the temperature is less than 650 ℃, the calcination temperature has little effect on the acid strength distribution in the active center of isomerization. The isomerization activity of o-xylene on HZSM-5 at different calcination temperatures has a corresponding relationship with the number of acid sites, and their trends with the calcination temperature are quite similar.