Liu Guodong, Liu Jiaxu, He Ning, Miao Cuilan, Wang Jilei, Xin Qin, Guo Hongchen
Department of Catalytic Chemistry and Engineering, State Key Laboratory of Fine Chemicals, Dalian University of Technology Dalian 116012 P. R. China
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences Dalian 116023 P. R. China.
RSC Adv. 2018 May 22;8(33):18663-18671. doi: 10.1039/c8ra02467g. eCollection 2018 May 17.
A series of Zn-modified Silicalite-1 (S-1) zeolites (Zn /S-1) were prepared by the wetness-impregnation method and applied in the catalytic conversion of isobutane. The structure and location of Zn species in Zn /S-1 were investigated using UV-Vis and N physical adsorption. The acidity and origin of the acid sites in Zn /S-1 were studied by NH-temperature programmed desorption and Fourier-transform infrared analysis. The catalytic performance of Zn /S-1 for isobutane conversion was investigated in a fixed-bed microreactor. In the experiments, the acidity of S-1 zeolite was dramatically increased by modification with Zn, with both Lewis and Brønsted sites identified in Zn /S-1. The relationship between Brønsted acid sites and Zn-OH groups on ZnO clusters of Zn /S-1 was also revealed for the first time. Furthermore, Zn /S-1 catalysts exhibited excellent catalytic performances in both isobutane dehydrogenation and butene isomerization reactions. A high selectivity of total butene products ranging from 84.6 to 97.2 was achieved on the catalysts with different Zn loadings. Moreover, the linear correlation between isobutane conversion and the acid amount (determined by NH-TPD) confirmed that the weak-to-medium acid sites in Zn /S-1 should play a key role in isobutane conversion.
通过湿浸渍法制备了一系列锌改性的Silicalite-1（S-1）沸石（Zn/S-1），并将其应用于异丁烷的催化转化。采用紫外可见光谱和N物理吸附对Zn/S-1中锌物种的结构和位置进行了研究。通过NH3程序升温脱附和傅里叶变换红外分析研究了Zn/S-1中酸位的酸性和来源。在固定床微反应器中研究了Zn/S-1对异丁烷转化的催化性能。实验中，通过锌改性显著提高了S-1沸石的酸性，在Zn/S-1中同时鉴定出了路易斯酸位和布朗斯特酸位。首次揭示了Zn/S-1的ZnO簇上布朗斯特酸位与Zn-OH基团之间的关系。此外，Zn/S-1催化剂在异丁烷脱氢和丁烯异构化反应中均表现出优异的催化性能。不同锌负载量的催化剂对总丁烯产物的选择性高达84.6%至97.2%。此外，异丁烷转化率与酸量（由NH3-TPD测定）之间的线性相关性证实，Zn/S-1中弱至中等强度的酸位在异丁烷转化中应起关键作用。
