A low-temperature approach to synthesize low-silica SAPO-34 nanocrystals and their application in the methanol-to-olefins (MTO) reaction. Issue 20 (14th September 2016)

• Record Type: Journal Article
• Authors: Gao, Beibei; Yang, Miao; Qiao, Yuyan; Li, Jinzhe; Xiang, Xiao; Wu, Pengfei; Wei, Yingxu; Xu, Shutao; Tian, Peng; Liu, Zhongmin
• Is Part Of: Catalysis science & technology. Volume 6:Issue 20(2016)
• Page Start: 7569
• Page End: 7578
• Publication Date: 2016-09-14
• Subjects: Catalysis -- Periodicals; 541.395
• DOI: 10.1039/c6cy01461e
• Languages: English
• ISSNs: 2044-4753

Abstract

Abstract : A facile low-temperature approach has been developed to synthesize low-silica SAPO-34 nanocrystals with excellent catalytic performance in the MTO reaction. Abstract : A low-temperature strategy is developed for the synthesis of low-silica SAPO-34 with a tunable Si content and relatively uniform Si distribution in the crystals, which is hitherto difficult to achieve. It is demonstrated that a lower crystallization temperature and a silicon source with relatively low reactivity are important factors leading to successful synthesis. The crystal size of SAPO-34 could be effectively decreased to 200 nm through a seed-assisted approach. The local atom environments of low-silica samples are investigated by solid state MAS NMR, which confirms the unique existence of Si(4Al) species in the framework. The obtained low-silica SAPO-34 exhibits excellent catalytic performance in the MTO reaction and the occurrence of catalyst deactivation varies with the acid properties. Through optimizing the Si content of the samples, a long catalyst life and a high initial/maximum selectivity to ethylene plus propylene could be achieved simultaneously over SAPO-34 with a Si content of Si/(Si + Al + P) = 0.047. This result would be valuable for the improvement of the catalytic properties of SAPO-34 used for a commercial MTO fluidized-bed reactor. However, SAPO-34 with a very low Si content ( e.g. Si/(Si + Al + P) = 0.039) exhibits a shortened catalyst life due to the insufficient Brønsted acid sites in spite of the high selectivity to light olefins.