Dimethyl Ether Carbonylation to Methyl Acetate over HZSM-35
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Dimethyl Ether Carbonylation to Methyl Acetate over HZSM-35 Junlong Liu • Huifu Xue • Xiumin Huang Yong Li • Wenjie Shen
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Received: 27 September 2009 / Accepted: 12 July 2010 / Published online: 22 July 2010 Ó Springer Science+Business Media, LLC 2010
Abstract Dimethyl ether (DME) carbonylation to methyl acetate (MA) was comparatively investigated over HZSM35 and mordenite (HMOR) zeolites. The HZSM-35 catalyst showed rather high selectivity and stability without obvious deactivation for 32 h on-stream at 473 K with a MA yield of *11%. On the other hand, the HMOR catalyst showed similar initial activity, but the yield of MA rapidly decreased to only 5% after 20 h on-stream. It was further revealed that the deposition rate of coke over the HZSM-35 catalyst was much lower than that on the HMOR zeolite, indicating that the formation rate of coke was strongly dependent on the pore sizes of the zeolites. The pore structure of HZSM-35 having a one-dimensional channel 10 member-ring (10-MR) and a perpendicularly intersected one-dimensional 8 member-ring (8-MR) channel effectively limited the formation of aromatic compounds which act as the precursors of coke. Keywords Dimethyl ether Carbonylation Methyl acetate HZSM-35 HMOR Stability
1 Introduction Acetic acid is mainly produced by carbonylation of methanol using Rh or Ir complexes and methyl iodide promoter (Monsanto and BP CativaTM homogeneous processes), which accounts for more than 60% of the world production capacity [1]. In order to avoid the use of corrosive halides and expensive precious metals, heterogeneous catalytic carbonylation of J. Liu H. Xue X. Huang Y. Li W. Shen (&) State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China e-mail: [email protected]
methanol and/or dimethyl ether (DME) using solid acid catalysts has attracted wide attention [2–4]. In this context, DME carbonylation to methyl acetate (MA) over heteropolyacids seems to be a quite promising route. For example, a RhPW12O40/SiO2 catalyst was reported to give 16% yield of MA at 498 K [4], and a Rh/CsxH3-xPW12O40 solid acid showed 33% conversion of DME with 94% selectivity of MA at 473 K [5, 6]. However, these catalysts also favored the formation of hydrocarbons, leading to a severe deactivation by deposition of carbonaceous residues. Quite recently, zeolites such as mordenite (HMOR) and ferrierite have been reported to be highly effective for DME carbonylation to MA, and HMOR is by far the most active and selective catalyst [7–10]. The common feature of these two types of zeolites is the existence of 8 memberring (8-MR) channel in which the reaction occurs preferentially [9]. It was proposed that carbonylation of DME in the 8-MR pore involves the interaction between the reactant and the surface hydroxyl (–OH) groups to form methoxy species, followed by insertion of CO molecule to methoxy species, forming acetyls. These acetyls further react with DME to produce MA and regenerate the surface methoxy species [8–1
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