Temperature-programmed reduction (H2-TPR) was employed to quantitatively characterize the active oxygen species generated from a high Fe-loading Fe/ZSM-5 catalyst exposed to N2O at 250 ℃. Fe-O-Fe2+ dimer was determin...Temperature-programmed reduction (H2-TPR) was employed to quantitatively characterize the active oxygen species generated from a high Fe-loading Fe/ZSM-5 catalyst exposed to N2O at 250 ℃. Fe-O-Fe2+ dimer was determined as the active iron complex for N2O decomposition to produce the active oxygen. Reduction of Fe3+ to Fe2+ by H2 in the dimer and removal of OH- groups from Fe2+ dimer by heating Fe/ZSM-5 to 700 ℃ were the prerequisites for the formation of this active Fe complex. A linear correlation with a slope of 1.0 between the amount of Fe-O-Fe2+ and that of active oxygen species was observed. Maximum amount of active oxygen species can be generated by reducing Fe/ZSM-5 catalyst with H2 at the temperatures over 500 ℃ and then heating the resulting product in Ar to 700 ℃, followed by N2O exposure at 250 ℃.The ratio of the total number of oxygen atoms (Ode) deposited by interaction of Fe-O-Fe2+ with N2O to the amount of Fe-O-Fe2+ was 2. However, not all the deposited oxygen atoms were active oxygen (Oa); the ratio of Oa and Ode was 0.5. The iron dimer complex composing active oxygen is a five-atom ion Fe2O32+; the most probable structure is as follows:展开更多
Taking simultaneous variations in both particle volume and density into account, the radial mixing and segregation of binary granular bed in a rotating drum half loaded were investigated by a 3D discrete element metho...Taking simultaneous variations in both particle volume and density into account, the radial mixing and segregation of binary granular bed in a rotating drum half loaded were investigated by a 3D discrete element method. Then, based on the competition theory of condensation and percolation, radial segregation due to differences in particle volume and/or density was analyzed. The results show that if either percolation effect induced by volume difference or condensation effect induced by density difference dominates in the active layer of moving bed, separation will occur. Controlling the volume ratio or density ratio of the two types of particles can achieve an equilibrium state between percolation and condensation, and then homogenous mixture can be obtained. When the percolation balances with the condensation, the relationship between volume ratioand density ratiopresents nearly a power function. Scaling up a rotating drum will not affect the mixing degree of the granular bed so long as the volume ratio and density ratio are predefined.展开更多
In this paper, a method of transforming volume integrals to boundary integrals is given for complicated loadings such as a i(y)x i and b i(x)y i . In the present method the volume in...In this paper, a method of transforming volume integrals to boundary integrals is given for complicated loadings such as a i(y)x i and b i(x)y i . In the present method the volume integrals are approximately transformed to boundary integrals.展开更多
文摘Temperature-programmed reduction (H2-TPR) was employed to quantitatively characterize the active oxygen species generated from a high Fe-loading Fe/ZSM-5 catalyst exposed to N2O at 250 ℃. Fe-O-Fe2+ dimer was determined as the active iron complex for N2O decomposition to produce the active oxygen. Reduction of Fe3+ to Fe2+ by H2 in the dimer and removal of OH- groups from Fe2+ dimer by heating Fe/ZSM-5 to 700 ℃ were the prerequisites for the formation of this active Fe complex. A linear correlation with a slope of 1.0 between the amount of Fe-O-Fe2+ and that of active oxygen species was observed. Maximum amount of active oxygen species can be generated by reducing Fe/ZSM-5 catalyst with H2 at the temperatures over 500 ℃ and then heating the resulting product in Ar to 700 ℃, followed by N2O exposure at 250 ℃.The ratio of the total number of oxygen atoms (Ode) deposited by interaction of Fe-O-Fe2+ with N2O to the amount of Fe-O-Fe2+ was 2. However, not all the deposited oxygen atoms were active oxygen (Oa); the ratio of Oa and Ode was 0.5. The iron dimer complex composing active oxygen is a five-atom ion Fe2O32+; the most probable structure is as follows:
基金Projects(5137424151275531)supported by the National Natural Science Foundation of ChinaProject(CX2014B059)supported by the Innovation Foundation for Postgraduate of Hunan Province,China
文摘Taking simultaneous variations in both particle volume and density into account, the radial mixing and segregation of binary granular bed in a rotating drum half loaded were investigated by a 3D discrete element method. Then, based on the competition theory of condensation and percolation, radial segregation due to differences in particle volume and/or density was analyzed. The results show that if either percolation effect induced by volume difference or condensation effect induced by density difference dominates in the active layer of moving bed, separation will occur. Controlling the volume ratio or density ratio of the two types of particles can achieve an equilibrium state between percolation and condensation, and then homogenous mixture can be obtained. When the percolation balances with the condensation, the relationship between volume ratioand density ratiopresents nearly a power function. Scaling up a rotating drum will not affect the mixing degree of the granular bed so long as the volume ratio and density ratio are predefined.
文摘In this paper, a method of transforming volume integrals to boundary integrals is given for complicated loadings such as a i(y)x i and b i(x)y i . In the present method the volume integrals are approximately transformed to boundary integrals.
