Abstract:

Sr- and Na-modified ZnZrO _x metal oxides were prepared by the co-precipitation method. The influence of Sr and Na modification on ZnZrO _x /SAPO-34 bifunctional catalysts for the conversion of syngas to lower olefins was investigated. Characterization techniques such as XRD, BET, SEM, XPS and Py-FTIR were employed to investigate the influence of Sr and Na promoters on ZnZrO _x metal oxides, its surface oxygen vacancies, acidity and reducibility, etc. The results showed that the introduction of Sr and Na led to the increase of the surface oxygen vacancies of the ZnZrO _x oxides. Moreover, the Na-ZrO₂ interface promoted the formation of more oxygen defects on the surface of metal oxides and improved its Lewis acidity. Sr and Na modified ZnZrO _x /SAPO-34 bifunctional catalysts possessed a relatively high CO conversion of 21.4% and lower olefins selectivity of 80.7% in the conversion of syngas to lower olefins. Both the mass ratio and the intimacy between the Sr and Na modified ZnZrO _{xmetal oxide and the molecular sieve SAPO-34 played crucial roles. Specifically, a mass ratio of 1∶1 and a relatively high level of intimacy achieved by grinding and mixing the powders could give the best synergistic effect between the two active sites, thereby endowing the catalyst with good catalytic stability.}

Key words: syngas, lower olefins, catalyst, interface, oxygen vacancy, stability

摘要：

通过共沉淀法制备了Sr、Na改性的ZnZrO _x 金属氧化物，考察了Sr和Na助剂的引入对ZnZrO _x /SAPO-34催化剂在合成气制低碳烯烃反应中性能的影响。采用XRD、BET、SEM、XPS和Py-FTIR等表征手段，系统研究了Sr和Na助剂对ZnZrO _x 金属氧化物表面氧空位、酸性和还原性等影响规律。结果表明，Sr和Na提高了ZnZrO _x 氧化物表面氧空位浓度，并且通过Na-ZrO₂界面促进了金属氧化物表面有更多氧缺陷的形成，同时提高了其路易斯酸性，因此在合成气制低碳烯烃反应中，具有较高的CO转化率（21.4%）和低碳烯烃选择性（80.7%）。此外，Sr和Na改性ZnZrO _x 金属氧化物与SAPO-34分子筛混合比例及“亲密度”对CO转化率和低碳烯烃选择性都有重要影响，合适的质量比（1∶1）和较高的“亲密度”（粉末研磨混合）能够使两种活性位点的协同作用达到最佳，且具有较好的催化稳定性。

关键词: 合成气, 低碳烯烃, 催化剂, 界面, 氧空位, 稳定性