The mechanism of dimethyl carbonate synthesis on Cu-exchanged zeolite Y
نویسندگان
چکیده
The mechanism of dimethyl carbonate (DMC) synthesis from oxidative carbonylation of methanol over Cu-exchanged Y zeolite has been investigated using in situ infrared spectroscopy and mass spectrometry under transient-response conditions. The formation of DMC is initiated by reaction of molecularly adsorbed methanol with oxygen to form either monoor di-methoxide species bound to Cu+ cations. Reaction of the mono-methoxide species with CO produces monomethyl carbonate (MMC) species. DMC is formed via two distinct reaction pathways—CO addition to di-methoxide species or by reaction of methanol with MMC. The rate-limiting step in DMC synthesis is found to be the reaction of CO with mono-methoxide or di-methoxide species. The first of these reactions produces MMC, which then reacts rapidly with methanol to produce DMC, whereas the second of these reactions produces DMC directly. Formaldehyde was identified as an intermediate in the formation of dimethoxy methane (DMM) and methyl formate (MF). Both byproducts are thought to form via a hemiacetal intermediate produced by the reaction of methanol with adsorbed formaldehyde at a Cu+ site. © 2008 Elsevier Inc. All rights reserved.
منابع مشابه
Effects of zeolite structure and composition on the synthesis of dimethyl carbonate by oxidative carbonylation of methanol on Cu-exchanged Y, ZSM-5, and Mordenite
The aim of this work was to establish the effects of zeolite structure/chemical composition on the activity and selectivity of Cu-exchanged Y (Si/Al = 2.5), ZSM-5 (Si/Al = 12), and Mordenite (Si/Al = 10) for the oxidative carbonylation of methanol to DMC. Catalysts were prepared by solid-state ion-exchange of the H-form of each zeolite with CuCl and were then characterized by FTIR and X-ray abs...
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