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用程序升温热脱附(TPD)技术,研究了五种 HNM(H-型天然丝光沸石)及 HM(合成 H-型丝光沸石)的表面酸性质,用氨作检测酸中心的分子探针,在六个 TPD谱图上均有两个脱附峰,第一峰的峰顶温度约为210℃,该峰代表了弱酸中心,第二峰的峰顶温度约550℃,代表强酸中心,两类不同酸中心的强度可用氨脱附活化能大小来表征。另外,按照非均匀表面处理,氨的脱附活化能 E_d是表面覆盖度θ的函数,本文用 Tokoro’s 计算机模拟热脱附曲线的方法,求得脱附活化能 E_d 并描绘出 E_d～θ关系图,用来表征酸中心强度及酸强度分布,结果表明 HNM 酸强度分布要比 HM 不均匀。计算还表明,4N HNM 样品的强酸中心的酸强度要比9N HNM 样品的大得多。本研究还给出了酸强度与 C_7催化裂解的转化率之间的关系。
The surface acid properties of five HNM (H-type natural mordenite) and HM (synthetic H-mordenite) were studied by using programmed temperature-programmed desorption (TPD). Ammonia was used as the molecular probe to detect the acid sites. There are two desorption peaks in each of the six TPD spectra. The first peak has a peak top temperature of about 210 ° C. This peak represents a weak acid site and the second peak has a peak top temperature of about 550 ° C, representing a strong acid site. Two The strength of different acid centers can be characterized by the size of the ammonia desorption activation energy. In addition, according to the non-uniform surface treatment, the activation energy of ammonia desorption E_d is a function of the surface coverage θ. In this paper, Tokoro’s computer simulates the thermal desorption curve to obtain the desorption activation energy E_d and plot E_d ~ θ , Used to characterize the acid center strength and acid strength distribution, the results show that the HNM acid strength distribution than the HM is not uniform. Calculations also showed that the 4N HNM sample had a much stronger acid at the center of the acid than the 9N HNM sample. This study also gives the relationship between acid strength and C_7 catalytic cracking conversion rate.