The Mechanism Of Methane Activation And Its Co-conversion With CO On Cu/Na-ZSM-5Zeolite

As a major component of natural gas and the most abundant feedstock, the study of methane activation and transformation is not only important for understanding C-H activation in metal organic chemistry, but also plays a significant role in its application to related industries. At present time, the industrial process involves a conversion from methane to synthesis gas, followed by a subsequent conversion to methanol and other valued chemicals or fuels. Because of the lack of flexibility, not only is this approach energy intensive, but less attractive in terms of the investment return. It would be of much interest to directly convert methane into liquid fuels and, particularly into methanol.Recently, it was found that methane could be converted to methanol with a high selectivity at low temperature on the copper modified Na-ZSM-5zeolite. However, the conversion mechanism is not clear.In this thesis, we report, based on the solid-state NMR measurements, that methane forms copper methoxy species on copper modified Na-ZSM-5zeolite. The methoxy species then produce methanol in the presence of water.Further, we investigated the co-reaction of methane and CO on the copper modified Na-ZSM-5zeolite by solid-state NMR spectroscopy. We found that methane reacted with CO to form acetic acid at a temperature range of250-350℃. Cu+CO species and CO2were identified as the by-products in the reaction system. At a higher temperature (450℃), methane reacted with CO to form multimethyl substituted benzene, and acetic acid may be the reaction intermediate species. We also studied the mechanism of the formation of acetic acid, and found the copper methoxy species reacted with CO to produce acetic acid. To the best of our knowledge, this Cu+CO species was for the first time unambiguously detected by solid-state NMR spectroscope on the copper modified Na-ZSM-5zeolite in our work.