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Regulation of Brønsted acid sites in H-MOR for selective methyl methoxyacetate synthesis
Authors:Jie Yao  Yan Wang  Suleiman Sabo Bello  Guangwen Xu  Lei Shi
Institution:1. Institute of Industrial Chemistry and Energy Technology, Shenyang University of Chemical Technology, Shenyang, 110142 China

College of Applied Chemistry, Shenyang University of Chemical Technology, Shenyang, 110142 China;2. Institute of Industrial Chemistry and Energy Technology, Shenyang University of Chemical Technology, Shenyang, 110142 China

Key Laboratory on Resources Chemicals and Materials of Ministry of Education, Shenyang University of Chemical Technology, Shenyang, 110142 China;3. Institute of Industrial Chemistry and Energy Technology, Shenyang University of Chemical Technology, Shenyang, 110142 China

Abstract:As it is well known, Brønsted acid sites in 8-MR of H-MOR (mordenite) are selective for dimethyl ether (DME) carbonylation to methyl acetate, whereas those in 12-MR are more prone to methanol to olefin reaction. Interestingly, we observed that the Brønsted acid sites in 12-MR of H-MOR are highly active for dimethoxymethane (DMM) carbonylation to methyl methoxyacetate (MMAc), whereas those in 8-MR led to the formation of DME. A series of modified H-MOR catalysts with accurate regulation of Brønsted acid sites in 12-MR or 8-MR were successfully synthesized by selective Na+ exchange or pyridine (Py) adsorption. Fourier-transform infrared (FT-IR) spectra, NH3-temperature-programmed desorption, Py-FT-IR, and inductively coupled plasma analyses suggested that Na+ first occupied Brønsted acid sites in 8-MR and then replaced those in 12-MR. All Na+-exchanged catalysts exhibited significant acceleration on MMAc selectivity, and the ratio of Brønsted acid amount in 12-MR/total had a positive correlation with MMAc selectivity. The MMAc selectivity (78%) of H-MOR-0.15Na was nearly 2.5 times more than that of untreated H-MOR (31%). However, H-MOR-Py showed almost no carbonylation activity (<1% MMAc) and a highest DME selectivity (98%), indicating that Brønsted acid sites in 12-MR were the only active sites for DMM carbonylation, whereas those in 8-MR tended to accelerate DMM disproportionation to DME.
Keywords:carbonylation  dimethoxymethane  methyl methoxyacetate  mordenite  regulation of Brønsted acid sites
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