Dealumination of HMCM-22 by various methods and its application in one-step synthesis of dimethyl ether from syngas

• Published in: Microporous and mesoporous materials 2006-04, Vol.91 (1), p.33-39
• Main Authors: Xia, Jianchao, Mao, Dongsen, Tao, Weichuan, Chen, Qingling, Zhang, Yahong, Tang, Yi
• Format: Article
• Language: English
• Subjects: Acidity; Catalysis; Chemistry; Colloidal state and disperse state; Dealumination; Dimethyl ether; Exact sciences and technology; General and physical chemistry; Ion-exchange; MCM-22 zeolite; Methanol dehydration; One-step synthesis; Porous materials; Surface physical chemistry; Syngas; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Zeolites: preparations and properties
• ISSN: 1387-1811; 1873-3093
• DOI: 10.1016/j.micromeso.2005.11.014

A series of MCM-22 zeolites were prepared by hydrothermal synthesis and subsequent dealumination by oxalic/citric acid leaching and steaming. The structural and acidic properties of the prepared samples were characterized by methods of XRD, ICP-AES, 27Al MAS NMR, pyridine-adsorbed IR and NH 3-TPD. The results indicated that the sample treated by oxalic acid (MCM-22O) has the lowest aluminum content while the samples treated by steam have little change of the aluminum content. Unusually, sample MCM-22O possessed the strongest acidity among the dealuminated samples in spite of its lowest content of aluminum. It may be due to its least content of extraframework aluminum, which may lead to the weakening of acidity. Additionally, the prepared zeolites were mixed with a methanol synthesis catalyst and then applied in the process of syngas to dimethyl ether. Citric acid treated sample performed best with the least generation of byproducts, which have been well related to its structural and acidic properties.