Home – Home – Jornals – Chemistry for Sustainable Development 2017 number 2

A new gas-phase process of halogen-free dimethyl ether (DME) carbonylation to methyl acetate is a promising eco-pure preparation method of methyl acetate due to excluding methyl iodide, replacing methanol for cheaper raw materials that are DME and the removal of the separation stage of the reaction products of the catalyst and methyl iodide. The work presents studying an opportunity of using promoted by silver or copper as catalysts for this reaction. Catalysts with composition of 1 % Ag/Cs_1.5H_1.5РW₁₂O₄₀, 1 % Cu/Cs_1.5H_1.5РW₁₂O₄₀ и Cs_1.5H_1.5РW₁₂O₄₀ were studied by BET, X-ray phase analysis (XPA), scanning electron microscopy (SEM) and IR spectroscopy of adsorbed pyridine. It was demonstrated that the specific surface of samples was about 60 m²/g, the concentration of strong BrØnsted acid sites (BAS) was found at a level of 130 μmol/g, the phase composition of the promoted samples fully corresponded to the initial Cs_1.5H_1.5РW₁₂O₄₀ sample and represented a mixture of two phases that are heteropolyacids and acid cesium salt. High concentrations of BAS demonstrate superacid character of the resulting catalysts capable of activating a C-O bond in the DME molecule. Trials of the samples under industrial catalysis conditions (pressure of 10 atm, temperature of 200 °С, the composition of the initial mixture of DME/CO = 1 : 10) demonstrated that a 1 % Ag/Cs_1.5H_1.5РW₁₂O₄₀ catalyst exceeded the activity of the initial acid Cs_1.5H_1.5РW₁₂O₄₀ catalyst in 2 times, the selectivity by the target product methyl acetate is 60 %. The use of 1 % Cu/Cs_1.5H_1.5РW₁₂O₄₀ does not lead to a change in the activity of Cs_1.5H_1.5РW₁₂O₄₀, the selectivity reduces to 40 %. The data obtained can serve as a basis for elaboration of a silver-containing highly effective catalyst for eco-pure halogen-free DME carbonylation to methyl acetate.