Zeolite is a microporous crystalline material with well-defined channels or cavities that has been widely used in the petrochemical industry over the past few decades. The uniform pore structure gives it unique shape-selective catalytic properties. How to achieve Al selection of specific T bits in zeolite channels is a hot topic in the zeolite field. In particular, FER and MOR type zeolites have been shown to be effective catalysts in DME carbonylation reactions. MOR-type zeolites show high activity but short life.
In contrast, FER zeolites show good catalytic stability but relatively low activity. How to improve the carbonylation active zeolite of FER, although controlling the Al site at a specific T site, has received increasing attention. Although a great deal of work has been done on FER zeolites in this reaction, improvements in catalytic performance are still limited. In addition, accurately identifying and controlling more Al atoms at different T positions of FER zeolites is also a big challenge.
Recently, Professors Zhu Xiangxue, Guo Peng and Li Xiujie of the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences used the Rietveld refinement method to control powder X-ray diffraction (PXRD) data to reveal the constrained Al crystal positions in FER-type zeolites. In this work, they deliberately synthesized a series of FER zeolites using cyclic (cyclohexylamine, piperidine, pyrrolidine and pyridine) and linear (ethylenediamine) organic structure-directing agents in hydroxide and fluoride media, respectively. Rietveld refining combined with simulated annealing algorithm was applied to study the Al sites in prepared and adsorbed FER zeolite samples at the atomic level.
Interestingly, no matter what structure-oriented agents and synthetic media are used in FER's Al atoms, β-zeolites are confined to the T1 and/or T3 sites. Unfortunately, the Brownsted acid site associated with the T1/T3 site is the inactive center in the DME carbonylation reaction. Therefore, compared with MOR-type zeolites, FER-type zeolites exhibit lower carbonylation activity. This is a good explanation for why the improvement of the catalytic properties of FER-type zeolites is limited by different synthesis methods. Their unprecedented discoveries and methods of characterization may shed light on the study of structure-activity relationships in zeolite-related research areas.
The Journal of Catalysis is co-sponsored by the Dalian Institute of Chemical Physics, Chinese Academy of Sciences and the Chinese Chemical Society, and is currently published by Elsevier Group. This monthly journal publishes original and rigorously vetted manuscripts in English in a timely manner, covering all areas of catalysis. The journal publishes highly scientifically valuable reviews, accounts, newsletters, articles, highlights, opinions and perspectives that help to understand and define new concepts that catalyze fundamental problems and practical applications. Chinese Journal of Catalysis Currently has a SCI impact factor of 8.271, ranking among the top six in applied chemistry. The editor-in-chief is a professor. Li Can and Zhang Tao.