Studies On The Synthesis And Applications Of MCM-22 Zeolite

Owing to its unique structure comprising both 10 member-ring (MR) and 12 MR channel system and special physiochemical properties, MCM-22 zeolite has shown many promising applications. This dissertation concentrated on its low-cost synthesis, adjusting of silica to alumina molar ratio (SAR) and catalytic applications in olefinic alkylation of thiophenic sulfur (OATS) of simulated FCC gasoline and aromatization of butene in liquefied-petroleum-gas (ABLPG) process.Firstly, studies on template function of two amines hexamethleneimine (HMI) and cyclohexylamine (CHA) in synthesis were carried out. It was found out that when using silica gel as the silica source, well crystallized MCM-22 could be obtained at quite a small amount of HMI owing to adding of CHA. While silica sol was used as the silica source, the crystalline type of product depended on the HMI to CHA molar ratios. This phenomenon could be explained by a theory of liquid-phase-nuclearation process. ERB-1, a boron-substitute of MCM-22 was intensively studied. Highly crystalline MCM-22 with SAR of 50~600 could be achieved by means of [B-Si-Al] system, which broke through the limit that it was hard to synthesize MCM-22 when SAR was greater than 80 under conventional [Si-Al] system.Then, the application of MCM-22 in OATS process was investigated. It was found out that with SAR increasing, thiophen conversion first increased and reached maximum at SAR of 75 (98.3%), and then reduced. A postulation was raised that the alkylation reaction mainly occurred at the external surface of MCM-22 zeoltie.The application of MCM-22 in ABLPG process was also investigated. The results indicated that the initial butene conversion could reach as high as 97% over all the catalysts. The aromatization activity declined with time on stream, and good reaction stability could be achieved on MCM-22 with SAR of 50~200. Three kinds of coke existed over the reacted catalysts, and the main reason for the deactivation of these catalysts depended on the SAR of MCM-22, which could be channel blockage or loss of strong acid sites or both.Finally, the process of MCM-22 transformation to ZSM-35 was investigated. MCM-22/ZSM-35 co-crystals with adjustable ZSM-35 content were obtained. It was found out that the MCM-22/ZSM-35 co-crystals, unlike the mechanical mixture of MCM-22 and ZSM-35, might be some intergrowth of them.