Methanol conversion to DME was investigated over CuO /H-MOR nanocatalyst prepared by precipitation and /or by precipitation flowed by ultrasonic irradiation methods. BET,XRD,SEM,NH3-TPD and H2-TPR techniques were used...Methanol conversion to DME was investigated over CuO /H-MOR nanocatalyst prepared by precipitation and /or by precipitation flowed by ultrasonic irradiation methods. BET,XRD,SEM,NH3-TPD and H2-TPR techniques were used to characterize nanocatalysts. The effective ultrasonication factors encountered during carrying out the dehydration of methanol on Cuo /H-MOR zeolite catalysts to produce dimethylether are studied in the present work. These factors include: the type of ultrasonication media,the ultrasonication time,and the fixed weight of the solid catalyst per the volume of the ultrasonication liquid media( Wcatalyst/ Vliquidratio). XRD showed that structure of H-MOR is not damaged even after it is loaded with CuO nanoparticles or with ultrasonication. H2-TPR profiles indicated that reducibility of sonicated CuO / H-MOR nanocatalyst is higher than non-sonicated catalyst. It is found that employing ultrasound energy for 60 min has the highest influence on the surface properties of nanocatalyst and its catalytic performance( activity and stability) of CuO / H-MOR catalyst. Surface morphology( SEM) of the sonicated CuO /H-MOR catalysts have clarified that methanol by itself used as an ultrasonication medium gives the best results concerning the homogeneity of particle sizes compared to the non-sonicated catalyst,where large agglomerates and non-homogeneous clusters appeared. Water used as a sonication medium showed many large agglomerates in addition to some smaller particles resulted in lowcatalytic activity. The different alcohols and( Wcatalyst/ Vliquid) ratio were examined to give precise correlation with the catalytic activity of the sonicated CuO / H-MOR zeolite catalyst. These findings certified that ultrasonication has a deep effect on the surface morphology and hence on the catalytic behavior of the dehydration of methanol to DME. NH3-TPD shows that ultrasound irradiation has enhanced the acidity of CuO / H-MOR catalyst and hence it's catalytic performance for DME formation.展开更多
MOR zeolite has been effectively utilized for dimethyl ether(DME)carbonylation reaction due to its unique pore structure and acidity.During industrial production,the transformation of ammonium type MOR zeolite(NH_(4)-...MOR zeolite has been effectively utilized for dimethyl ether(DME)carbonylation reaction due to its unique pore structure and acidity.During industrial production,the transformation of ammonium type MOR zeolite(NH_(4)-MOR)into proton type MOR zeolite(H-MOR)causes inevitable dealumination.Therefore,understanding the influencing factors and dynamic evolution mechanism of zeolite dealumination is crucial.In this work,the stability of framework aluminum was studied by X-ray diffraction(XRD),Fourier transform infrared(FT-IR)spectroscopy,^(29)Si,^(27)Al,^(1)H magic angle spinning nuclear magnetic resonance(MAS NMR),and DME carbonylation performance evaluation.These results indicate that extra-framework cation Na^(+)and NH_(4)^(+)could better preserve the aluminum structure of the MOR zeolite framework compared to H^(+),primarily due to the different'attraction'of the framework to water.Furthermore,the impact of water on the zeolite framework aluminum at high temperature was studied by manipulating the humidity of the calcination atmosphere,revealing the formation of extra-framework six-coordinated aluminum(Al(Ⅵ)-EF)and the mechanism of water influence on the zeolite framework aluminum.展开更多
文摘Methanol conversion to DME was investigated over CuO /H-MOR nanocatalyst prepared by precipitation and /or by precipitation flowed by ultrasonic irradiation methods. BET,XRD,SEM,NH3-TPD and H2-TPR techniques were used to characterize nanocatalysts. The effective ultrasonication factors encountered during carrying out the dehydration of methanol on Cuo /H-MOR zeolite catalysts to produce dimethylether are studied in the present work. These factors include: the type of ultrasonication media,the ultrasonication time,and the fixed weight of the solid catalyst per the volume of the ultrasonication liquid media( Wcatalyst/ Vliquidratio). XRD showed that structure of H-MOR is not damaged even after it is loaded with CuO nanoparticles or with ultrasonication. H2-TPR profiles indicated that reducibility of sonicated CuO / H-MOR nanocatalyst is higher than non-sonicated catalyst. It is found that employing ultrasound energy for 60 min has the highest influence on the surface properties of nanocatalyst and its catalytic performance( activity and stability) of CuO / H-MOR catalyst. Surface morphology( SEM) of the sonicated CuO /H-MOR catalysts have clarified that methanol by itself used as an ultrasonication medium gives the best results concerning the homogeneity of particle sizes compared to the non-sonicated catalyst,where large agglomerates and non-homogeneous clusters appeared. Water used as a sonication medium showed many large agglomerates in addition to some smaller particles resulted in lowcatalytic activity. The different alcohols and( Wcatalyst/ Vliquid) ratio were examined to give precise correlation with the catalytic activity of the sonicated CuO / H-MOR zeolite catalyst. These findings certified that ultrasonication has a deep effect on the surface morphology and hence on the catalytic behavior of the dehydration of methanol to DME. NH3-TPD shows that ultrasound irradiation has enhanced the acidity of CuO / H-MOR catalyst and hence it's catalytic performance for DME formation.
基金support provided by the National Key Research and Development Program of China(No.2022YFE0116000)the National Natural Science Foundation of China(22241801,22022202,22032005,22288101,21972142,21991090,21991092,21991093)Dalian Outstanding Young Scientist Foundation(2021RJ01).
文摘MOR zeolite has been effectively utilized for dimethyl ether(DME)carbonylation reaction due to its unique pore structure and acidity.During industrial production,the transformation of ammonium type MOR zeolite(NH_(4)-MOR)into proton type MOR zeolite(H-MOR)causes inevitable dealumination.Therefore,understanding the influencing factors and dynamic evolution mechanism of zeolite dealumination is crucial.In this work,the stability of framework aluminum was studied by X-ray diffraction(XRD),Fourier transform infrared(FT-IR)spectroscopy,^(29)Si,^(27)Al,^(1)H magic angle spinning nuclear magnetic resonance(MAS NMR),and DME carbonylation performance evaluation.These results indicate that extra-framework cation Na^(+)and NH_(4)^(+)could better preserve the aluminum structure of the MOR zeolite framework compared to H^(+),primarily due to the different'attraction'of the framework to water.Furthermore,the impact of water on the zeolite framework aluminum at high temperature was studied by manipulating the humidity of the calcination atmosphere,revealing the formation of extra-framework six-coordinated aluminum(Al(Ⅵ)-EF)and the mechanism of water influence on the zeolite framework aluminum.
