The role of copper chloride hydroxides in the oxidative carbonylation of methanol for dimethyl carbonate synthesis

• Published in: Journal of molecular catalysis. A, Chemical Vol. 203; no. 1; pp. 137 - 143
• Main Authors: Han, Man Seok, Lee, Byung Gwon, Ahn, Byoung Sung, Kim, Hoon Sik, Moon, Dong Ju, Hong, Suk In
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.09.2003; Elsevier
• Subjects: Atacamite; Catalysis; Catalytic reactions; Chemistry; Copper chloride hydroxides (Cu 2(OH) 3Cl); Dimethyl carbonate (DMC); Exact sciences and technology; General and physical chemistry; Oxidative carbonylation of methanol; Paratacamite; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Dimethyl carbonate (DMC); Paratacamite; Copper chloride hydroxides (Cu 2(OH) 3Cl); Oxidative carbonylation of methanol; Atacamite; Catalytic reaction; Organic carbonate; Transition metal Compounds; Alcohol; Supported catalyst; Sodium hydroxide; Heterogeneous catalysis; Carbonylation; Vapor phase; Activated carbon; Oxidation; Copper chloride hydroxides (Cu2(OH)3Cl); Catalyst activity; Copper chloride; Methanol
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/S1381-1169(03)00131-6

This is the SEM image of CuCl 2/NaOH/AC catalyst with molar ratio of OH/Cu = 1.0. An interesting crystal structure was observed and confirmed to be paratacamite (rhombohedral) by using various surface analyzers. It has shown a higher activity to DMC synthesis than CuCl 2/AC. This kind of crystal habit was not observed at all in the SEM image of CuCl 2/AC catalyst free of NaOH. Dimethyl carbonate (DMC) synthesis by oxidative carbonylation of methanol has been studied using vapor phase flow reaction system in the presence of CuCl 2/NaOH/AC (AC, activated carbon) catalysts. A series of CuCl 2/NaOH/AC catalysts have been prepared by the conventional impregnation method with varying the molar ratio of OH/Cu from 0.0 to 1.0. The catalytic activity of CuCl 2/NaOH/AC catalysts has been found to increase continuously with the increase of OH/Cu molar ratio as compared with CuCl 2/AC catalyst. The morphological analysis by X-ray diffraction, scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) has shown that the improved performance of CuCl 2/NaOH/AC catalysts was closely related with the existence of copper chloride hydroxides (Cu 2(OH) 3Cl). Two different crystal habits of Cu 2(OH) 3Cl were observed in the catalyst surface based on the OH/Cu molar ratio. One is α-Cu 2(OH) 3Cl (atacamite) which is orthorhombic, while the other is γ-Cu 2(OH) 3Cl (paratacamite) which is rhombohedral. The catalyst phase was revealed to change from α-Cu 2(OH) 3Cl to γ-Cu 2(OH) 3Cl with the increase of OH/Cu molar ratio. The catalyst phase was α-Cu 2(OH) 3Cl dominant at the molar ratio of OH/Cu=0.5, while at the molar ratio of OH/Cu=1.0, γ-Cu 2(OH) 3Cl dominant. The γ-type catalyst was found to be more favorable to DMC synthesis than the α-type catalyst. The CO temperature-programmed desorption (TPD) experiments on the employed catalysts also strongly supported these observations.