Abstract
Mordenite (H-MOR) catalysts were synthesized by a hydrothermal method, and silver-modified mordenite (Ag-MOR) catalysts were prepared by ion exchange with AgNO3 at different concentrations. The performance of these catalysts in the carbonylation of dimethyl ether (DME) to methyl acetate (MA) was also evaluated. The catalysts were characterized by Ar adsorption/desorption, XRD, ICP-AES, SEM, HRTEM, 27Al NMR, H2-TPR, NH3-TPD, Py-IR, and CO-TPD. According to the characterization results, Ag ion exchange sites were mainly located in the 8-membered ring (8-MR) channels of Ag-MOR; evenly dispersed Ag2O particles were also present. The acid site distribution was changed by the modification of Ag, and the amount of Brønsted acid sites increased in 8-MR and decreased in 12-MR. The CO adsorption performance of the catalyst significantly increased with the modification of Ag. These changes improved the conversion and selectivity of the carbonylation of DME. Over 4Ag-MOR in particular, DME conversion and MA selectivity reached 94% and 100%, respectively.
Highlights
Because of the increasing serious environmental problems caused by the use of fossil energy, ethanol, a promising alternative, has received more and more attention [1]
H-MOR was synthesized via a hydrothermal synthesis, while 1Ag-MOR, 2Ag-MOR, 3Ag-MOR, 4Ag-MOR, and 5Ag-MOR were obtained by a low-concentration AgNO3 ion exchange process
According to the H2-TPR and high-resolution transmission electron microscopy (HRTEM) analyses, Ag atoms mainly entered 8-membered ring (8-MR) and partly entered 12-membered ring (12-MR); Ag2O particles were uniformly dispersed in Ag-MOR
Summary
Because of the increasing serious environmental problems caused by the use of fossil energy, ethanol, a promising alternative, has received more and more attention [1]. The process of dimethyl ether (DME) carbonylation to methyl acetate (MA) and MA hydrogenation to ethanol has gained the attention of researchers owing to its high atom utilisation and environmental friendliness. Catalysts for this process are mainly divided into two types: zeolite catalysts (such as mordenite (MOR) [5], ZSM-35 [6], ZSM5 [7], and HFER [8,9]) and heteropoly acid catalysts [10,11]. Owing to its unique structure and properties, MOR occupies an important position in the DME carbonylation reaction
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