Electronic structures of monoclinic and hexagonal pyrrhotite were studied using density functional theory method,together with their flotation behavior. The main contribution of monoclinic pyrrhotite is mainly from Fe...Electronic structures of monoclinic and hexagonal pyrrhotite were studied using density functional theory method,together with their flotation behavior. The main contribution of monoclinic pyrrhotite is mainly from Fe 3d, while that of hexagonal pyrrhotite is from Fe 3d, Fe 3p and S 3s. The hexagonal pyrrhotite is more reactive than monoclinic pyrrhotite because of large density of states near the Fermi level. The hexagonal pyrrhotite shows antiferromagnetism. S—Fe bonds mainly exist in monoclinic pyrrhotite as the covalent bonds, while hexagonal pyrrhotite has no covalency. The main contributions of higest occupied molecular orbital(HOMO) and lowest unoccupied molecular obital(LUMO) for monoclinic pyrrhotite come from S and Fe. The main contribution of HOMO for hexagonal pyrrhotite comes from Fe, while that of LUMO comes from S. The coefficient of Fe atom is much larger than that of S atom of HOMO for hexagonal pyrrhotite, which contributes to the adsorption of Ca OH+ on the surface of hexagonal pyrrhotite when there is lime. As a result, lime has the inhibitory effect on the floatation of hexagonal pyrrhotite and the coefficient of Fe is very close to that of S for monoclinic pyrrhotite. Therefore, the existence of S prevents the adsorption of Ca OH+on the surface of monoclinic pyrrhotite, which leads to less inhibitory effect on the flotation of monoclinic pyrrhotite.展开更多
Mesoporous aluminosilicates with cubic and hexagonal structure have been synthesized by structure units of β zeolite in a two step crystallization process and characterized by XRD, IR, N 2 physical adsorption and des...Mesoporous aluminosilicates with cubic and hexagonal structure have been synthesized by structure units of β zeolite in a two step crystallization process and characterized by XRD, IR, N 2 physical adsorption and desorption, 27 Al MAS NMR and NH 3 TPD techniques. The results show that MB48(25) and MB41(25) were similar to MCM 48 and MCM 41 on the long range structure respectively and MB48 with a cubic structure can be synthesized under the condition of a lower n (CTMAB)/ n (SiO 2) ratio. HMB48(25) and HMB41(25) exhibit a stronger acidic strength than conventional HMCM 41. The catalytic activity of HMB48(25) was the highest for cumene cracking and alkylation of 2,4 tert butylphenol with tert butylalcohol.展开更多
基金Project supported by the Open Foundation of Guangxi Key Laboratory for Advanced Materials and Manufacturing Technology,China
文摘Electronic structures of monoclinic and hexagonal pyrrhotite were studied using density functional theory method,together with their flotation behavior. The main contribution of monoclinic pyrrhotite is mainly from Fe 3d, while that of hexagonal pyrrhotite is from Fe 3d, Fe 3p and S 3s. The hexagonal pyrrhotite is more reactive than monoclinic pyrrhotite because of large density of states near the Fermi level. The hexagonal pyrrhotite shows antiferromagnetism. S—Fe bonds mainly exist in monoclinic pyrrhotite as the covalent bonds, while hexagonal pyrrhotite has no covalency. The main contributions of higest occupied molecular orbital(HOMO) and lowest unoccupied molecular obital(LUMO) for monoclinic pyrrhotite come from S and Fe. The main contribution of HOMO for hexagonal pyrrhotite comes from Fe, while that of LUMO comes from S. The coefficient of Fe atom is much larger than that of S atom of HOMO for hexagonal pyrrhotite, which contributes to the adsorption of Ca OH+ on the surface of hexagonal pyrrhotite when there is lime. As a result, lime has the inhibitory effect on the floatation of hexagonal pyrrhotite and the coefficient of Fe is very close to that of S for monoclinic pyrrhotite. Therefore, the existence of S prevents the adsorption of Ca OH+on the surface of monoclinic pyrrhotite, which leads to less inhibitory effect on the flotation of monoclinic pyrrhotite.
文摘Mesoporous aluminosilicates with cubic and hexagonal structure have been synthesized by structure units of β zeolite in a two step crystallization process and characterized by XRD, IR, N 2 physical adsorption and desorption, 27 Al MAS NMR and NH 3 TPD techniques. The results show that MB48(25) and MB41(25) were similar to MCM 48 and MCM 41 on the long range structure respectively and MB48 with a cubic structure can be synthesized under the condition of a lower n (CTMAB)/ n (SiO 2) ratio. HMB48(25) and HMB41(25) exhibit a stronger acidic strength than conventional HMCM 41. The catalytic activity of HMB48(25) was the highest for cumene cracking and alkylation of 2,4 tert butylphenol with tert butylalcohol.
