Insights Into Carbonvlation Of Methyl Alcohol And Dimethyl Ether On Zeolites From Solid-state NMR Spectroscopy

As environmental friendly heterogeneous catalysts, solid acid has been widely used in variously fields of the industrial production. Among various solid acid, zeolites are of great interest because of their distinct physicochemical properties and excellent activity in catalytic reaction. In this dissertation, the mechanism of CH3OH and DME carbonylation reaction in zeolites with varying channel structure has been studied by in-Situ Solid-State NMR Spectroscopy.The mechanism of dimethyl ether (DME) carbonylation reaction with CO in MOR zeolites has been studied by in-Situ Solid-State NMR Spectroscopy. Mordenite (MOR) zeolite consists of8-membered ring (MR) and12-membered ring (MR) channels. As the most active zeolite catalyst for CH3OH and DME carbonylation, it is believed that the carbonylation reaction of CH3OH and DME occurs mainly in8MR channels. We separately studied the reaction in the8MR and12MR channels respectively. The surface acetyl species (CH3CO-) is for the first time observed in the8MR channels, which however cannot form in the12MR channels. Alternatively, the acetaldehyde is generated which might be the intermediate in12MR channels. Comparing with surface acetyl species, acetaldehyde acts as the intermediate for the formation of methylacetate with a lower activity and selectivity.The mechanism of DME carbonylation reaction with CO in ZSM-35(FER), ZSM-5(MFI) and Y(FAU) zeolites has been studied by in-Situ Solid-State NMR Spectroscopy. DME and CO carbonylation reaction can occure in ZSM-35, ZSM-5and Y zeolites. ZSM-35zeolites contains8MR and10MR channels. We observed surface acetyl species, which is the same intemediate species as observed in the8MR channels of MOR. ZSM-5zeolite consists of10MR channels, where acetyl species is also observed. Howere, the surface acetyl species in the10MR channels of ZSM-5easily decomposes to form CO, which could be the reason that ZSM-5zeolite has a low activity in carbonylation reaction of DME and CO. Y zeolites only has one type of12MR channels. We have not observed surface acetyl species in the carbonylation process. However, acetaldehyde is proved to be the intermediate for the formation of mythl acetate. This phenomenon is the same as that for MOR zeolites.The mechanism of DME carbonylation reaction with CO2+in Cu-H-MOR of Cu2+can notably enhance the activity and selectivity of CH3OH carbonylation reaction over Cu-H-MOR comparing with parent H-MOR zeolite. The adsorbed species formed in the reaction were determined. It is for the first time that the Cu-CO, Cu-O-(CO)CH3and Cu-OCH3were observed during the carbonylation by NMR Spectroscopy. Moreover, the high reactivity toward formtion of methyl acetate was determined and intermediate role of the Cu-O-(CO)CH3was discussed in the proposed mechanism.