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
MnO_x/Al_2O_3 and MnO_x/ZrO_2-Al_2O_3 catalysts were prepared by incipientwetness impregnation of Mn(CH_3COO)_2 on the corresponding supports, followed by thecharacterization using X-ray diffraction (XRD), temperature...MnO_x/Al_2O_3 and MnO_x/ZrO_2-Al_2O_3 catalysts were prepared by incipientwetness impregnation of Mn(CH_3COO)_2 on the corresponding supports, followed by thecharacterization using X-ray diffraction (XRD), temperature programmed reduction (TPR) and BETsurface area techniques. The result shows the BET surface area of ZrO_2-Al_2O_3 is lower than thatof Al_2O_3 due to the loading of ZrO_2. However the resulted MnO_x/ZrO_2-Al_2O_3 catalyst exhibitshigher activity for methane combustion than MnO_x/Al_2O_3, because the addition of ZrO_2 ontoAl_2O_3 is beneficial for the dispersion of Mn species and the improvement of the lattice oxygenactivity in MnO_x, subsequently the activation of methane during combustion. The optimum loading ofZr in MnO_x/ZrO_2-Al_2O_3 is in the range of 5%-10% correlated with the calcination temperatures ofcatalyst supports.展开更多
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.
基金This work was financially supported by Shandong Provincial Department of Science and Technology(project number:981206403)and the State Key Laboratory of Coal Conversion at Institute of Coal Chemistry of CAS(2002-2003)
文摘MnO_x/Al_2O_3 and MnO_x/ZrO_2-Al_2O_3 catalysts were prepared by incipientwetness impregnation of Mn(CH_3COO)_2 on the corresponding supports, followed by thecharacterization using X-ray diffraction (XRD), temperature programmed reduction (TPR) and BETsurface area techniques. The result shows the BET surface area of ZrO_2-Al_2O_3 is lower than thatof Al_2O_3 due to the loading of ZrO_2. However the resulted MnO_x/ZrO_2-Al_2O_3 catalyst exhibitshigher activity for methane combustion than MnO_x/Al_2O_3, because the addition of ZrO_2 ontoAl_2O_3 is beneficial for the dispersion of Mn species and the improvement of the lattice oxygenactivity in MnO_x, subsequently the activation of methane during combustion. The optimum loading ofZr in MnO_x/ZrO_2-Al_2O_3 is in the range of 5%-10% correlated with the calcination temperatures ofcatalyst supports.
