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 absorption spectroscopy (XAS). The XANES portion of the XAS data showed that all of the copper was present as Cu{sup +} cations, and analysis of the EXAFS portion of the data shows the Cu{sup +} cations had a CuO coordination number of 2.1 on Cu-Y and 2.7 on Cu-ZSM-5 and Cu-MOR. Dimethyl carbonate (DMC) was observed as the primary product when a mixture of CH{sub 3}OH/CO/O{sub 2} was passed over Cu-Y, whereas dimethoxy methane was the primary product over Cu-ZSM-5 and Cu-MOR. The higher activity and selectivity of Cu-Y for the oxidative carbonylation of methanol can be attributed to the weaker adsorption of CO on the Cu{sup +} cations exchanged into Y zeolite. In situ IR observations revealed that under reaction conditions, adsorbed CO was displaced by methoxide groups bound to the Cu{sup +} cations. The kinetics of DMC synthesis suggests that the rate-limiting step in the formation of this product was the insertion of CO into CuOCH{sub 3} bonds. The yield of DMC decreased with methanol conversion, likely due to the hydrolysis of DMC to methanol and carbon dioxide.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-76SF00515
- OSTI ID:
- 953914
- Report Number(s):
- SLAC-REPRINT-2009-478; JCTLA5; TRN: US201004%%651
- Journal Information:
- J. Cat. 251:443,2007, Vol. 251, Issue 2; ISSN 0021-9517
- Country of Publication:
- United States
- Language:
- English
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