Ethanol is used as an alternative fuel to improve combustion properties and reduce emissions. Recently, a new route of ethanol synthesis from syngas including carbonylation of dimethyl ether (DME) to methyl acetate (MA) and subsequent hydrogenation of MA has attracted much attention. The advantages such as high atom economy, moderate conditions, diverse sources (e.g. biomass, coal, natural gas) as well as low energy consumption, makes this technique implementable in industry. As a key reaction in this process, carbonylation of DME can be catalyzed by H-MOR with excellent initial activity and selectivity (&gt; 99%). Metal dopant, especially Cu, significantly accelerate MA formation. However, both H-MOR and Cu/H-MOR suffer a rapid deactivation, restricting the commercial implementation of MOR based catalysts. Moreover, controversial observations have been reported in terms of the effect of Cu species on deactivation. Some researchers suggest the addition of Cu inhibit the coke formation, while the others consider coke amount is almost unchanged upon Cu modification. In this work, to shed light on the mechanism of coke formation and compare deactivation behaviors of H-MOR and Cu/H-MOR catalysts, the nature and evolution of the carbonaceous deposits have been fully characterized using TGA, 13C NMR spectroscopy, FTIR, UV-vis and N2 physisorption. The results reveal that the carbonaceous species are mainly alkylated aromatic species and the micropore volume of the spent catalysts decrease with increasing the coke content. Meanwhile, the amount of Brønsted acid sites in the 12 membered ring (B12-MR) decreases during the reaction with no significant change of Brønsted acid sites in the 8 membered ring (B8-MR). As the B8-MR is generally accepted as active sites for this reaction, it is conclusive that the deactivation would be resulted from the coke deposition in the 12-MR channels and block of the main channels. Furthermore, a kinetic model for coke formation is proposed to compare the deactivation behaviors of H-MOR with Cu/H-MOR. In terms of activation energies for the formation of carbonaceous species, the presence of Cu accelerate the formation of non-condensed single aromatics species, but inhibit them to be more condensed. This work will contribute to the deactivation mechanism of reactions on zeolites, especially carbonylation reaction. Furthermore, it will contribute to the commercial implementation of this novel fuel ethanol synthesis route from syngas.

Carbonylation of dimethyl ether over MOR and Cu/H-MOR catalysts: comparative investigation of deactivation behavior

2019 Spring National Meeting

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