Polyoxymethylene dimethyl ethers(OMEs)with physical properties similar to those of diesel has received significant attention as green additives for soot emission suppression.Herein,series of SO_(4)^(2-)/ZrO_(2)-TiO_(2...Polyoxymethylene dimethyl ethers(OMEs)with physical properties similar to those of diesel has received significant attention as green additives for soot emission suppression.Herein,series of SO_(4)^(2-)/ZrO_(2)-TiO_(2)catalysts were developed for OMEs production from dimethoxymethane(DMM)and1,3,5-trioxane through sequential formaldehyde monomer insertion into C-O bond of DMM.Not Lewis but Bronsted acid sites were identified to be active for the decomposition of 1,3,5-trioxane into formaldehyde unit,however,both of them are effective for the chain propagation of DMM via formaldehyde unit insertion into C-O bond.Kinetic studies indicated each chain growth step exhibited the same parameters and activation barrier on corresponding Bronsted and Lewis acid sites due to the same reaction mechanism and very similar chemical structure of OMEs.Also,the catalytic stability investigation suggested the deactivation behavior was derived from the carbon deposition,and the decay factor could be exponentially correlated with the amount of coke accumulation.展开更多
It is urgent to develop catalysts with application potential for oxidative coupling of methane(OCM)at relatively lower temperature.Herein,three-dimensional ordered macro porous(3 DOM)La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)(...It is urgent to develop catalysts with application potential for oxidative coupling of methane(OCM)at relatively lower temperature.Herein,three-dimensional ordered macro porous(3 DOM)La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)(A_(2)B_(2)O_(7)-type)catalysts with disordered defective cubic fluorite phased structure were successfully prepared by a colloidal crystal template method.3DOM structure promotes the accessibility of the gaseous reactants(O2and CH4)to the active sites.The co-doping of Ca and Sr ions in La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts improved the formation of oxygen vacancies,thereby leading to increased density of surface-active oxygen species(O_(2)^(-))for the activation of CH4and the formation of C2products(C2H6and C2H4).3DOM La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts exhibit high catalytic activity for OCM at low temperature.3DOM La1.7Sr0.3Ce1.7Ca0.3O7-δcatalyst with the highest density of O_(2)^(-)species exhibited the highest catalytic activity for low-temperature OCM,i.e.,its CH4conversion,selectivity and yield of C2products at 650℃are 32.2%,66.1%and 21.3%,respectively.The mechanism was proposed that the increase in surface oxygen vacancies induced by the co-doping of Ca and Sr ions boosts the key step of C-H bond breaking and C-C bond coupling in catalyzing low-temperature OCM.It is meaningful for the development of the low-temperature and high-efficient catalysts for OCM reaction in practical application.展开更多
基金the fund from the National Natural Science Foundation of China(22208349)the Innovation Academy for Green Manufacture(Chinese Academy of Sciences,IAGM2020C20)+1 种基金Shandong Provincial Natural Science Youth Fund(ZR2022QB244)Japan Society for the Promotion of Science(P20345)。
文摘Polyoxymethylene dimethyl ethers(OMEs)with physical properties similar to those of diesel has received significant attention as green additives for soot emission suppression.Herein,series of SO_(4)^(2-)/ZrO_(2)-TiO_(2)catalysts were developed for OMEs production from dimethoxymethane(DMM)and1,3,5-trioxane through sequential formaldehyde monomer insertion into C-O bond of DMM.Not Lewis but Bronsted acid sites were identified to be active for the decomposition of 1,3,5-trioxane into formaldehyde unit,however,both of them are effective for the chain propagation of DMM via formaldehyde unit insertion into C-O bond.Kinetic studies indicated each chain growth step exhibited the same parameters and activation barrier on corresponding Bronsted and Lewis acid sites due to the same reaction mechanism and very similar chemical structure of OMEs.Also,the catalytic stability investigation suggested the deactivation behavior was derived from the carbon deposition,and the decay factor could be exponentially correlated with the amount of coke accumulation.
基金supported by the National Key Research and Development Program of China(Nos.2022YFB3504100,2022YFB3506200)the National Natural Science Foundation of China(Nos.22208373,22376217)+1 种基金the Beijing Nova Program(No.20220484215)the Science Foundation of China University of Petroleum,Beijing(No.2462023YJRC030)。
文摘It is urgent to develop catalysts with application potential for oxidative coupling of methane(OCM)at relatively lower temperature.Herein,three-dimensional ordered macro porous(3 DOM)La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)(A_(2)B_(2)O_(7)-type)catalysts with disordered defective cubic fluorite phased structure were successfully prepared by a colloidal crystal template method.3DOM structure promotes the accessibility of the gaseous reactants(O2and CH4)to the active sites.The co-doping of Ca and Sr ions in La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts improved the formation of oxygen vacancies,thereby leading to increased density of surface-active oxygen species(O_(2)^(-))for the activation of CH4and the formation of C2products(C2H6and C2H4).3DOM La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts exhibit high catalytic activity for OCM at low temperature.3DOM La1.7Sr0.3Ce1.7Ca0.3O7-δcatalyst with the highest density of O_(2)^(-)species exhibited the highest catalytic activity for low-temperature OCM,i.e.,its CH4conversion,selectivity and yield of C2products at 650℃are 32.2%,66.1%and 21.3%,respectively.The mechanism was proposed that the increase in surface oxygen vacancies induced by the co-doping of Ca and Sr ions boosts the key step of C-H bond breaking and C-C bond coupling in catalyzing low-temperature OCM.It is meaningful for the development of the low-temperature and high-efficient catalysts for OCM reaction in practical application.
