Raman spectroscopy was applied to investigate the speciation in both single and mixed solutions of molybdate and vanadate at pH values from 10.0 to 1.0. Evidence was obtained for the difference of existing forms betwe...Raman spectroscopy was applied to investigate the speciation in both single and mixed solutions of molybdate and vanadate at pH values from 10.0 to 1.0. Evidence was obtained for the difference of existing forms between these two elements. Vanadium mainly exists as （VO3）n^n- while Mo is MoO4^2- in the pH range of 9.0-7.5. This difference is the theoretical basis for many available separation process. The species in the binary system was identified by comparing the Raman spectra with that in the single systems. Molybvanadates are formed below pH=6.5, which may partly be ascribed to the replacement of V atoms by Mo atoms in some V-O-V groups. Vanadium mainly exists as the decavanadate species in the pH range of 6.0-2.0. The predominant species of Mo are heteropolyanions having structural features of heptamolybdate rather than MosO26^4- and Mo36O112^8- which are the predominant Mo species in single solution at pH=2.0-1.0.展开更多
A 1D chain-like organic/inorganic composite material with polyoxovanadates serving as building blocks has been synthesized by the reaction of cyclohexylamine with vana- dium pentoxide, and characterized by IR, UV spec...A 1D chain-like organic/inorganic composite material with polyoxovanadates serving as building blocks has been synthesized by the reaction of cyclohexylamine with vana- dium pentoxide, and characterized by IR, UV spectra and TG-DTA technique. The title compound (C30H70N5O15V5, Mr = 995.61) crystallizes in orthorhombic, space group P212121 with a = 6.0093(12), b = 26.780(5), c = 27.979(6) ? V = 4502.6(16) 3, Z = 4, Dc = 1.461 g/cm3, F(000) = 2060, = 1.063 mm-1, R = 0.0651 and wR = 0.1084 for 3426 observed reflections (I > 2(I)). Single-crystal X-ray structural analysis indicates that the title compound consists of five proto- nated cyclohexylamine molecules and a polyoxovanadate anion of V5O155-. In addition, the results of IR spectra and single-crystal X-ray diffraction exhibit that there exists comparatively stronger interaction between the organic groups and polyoxovanadate anion in solid state. Adjacent structure units are bridged through corner-sharing oxygen atoms of VO4 tetrahedra to construct a novel one-dimensional zigzag infinite linear chain arrangement. The curves of TG- DTA elucidate that the process of weight loss of the title compound is divided into two stages, and also reveal that the framework of polyoxovanadate anion decomposes at 473.0 ℃.展开更多
In the present study, the modified （non-Keggin-type） aqueous solutions of Mo-V-phosphoric heteropoly acids HaPzMoyVx,Oh （HPA-x＇） were applied as homogeneous catalysts for the two-stage oxidation of TMP （2,3,6-tr...In the present study, the modified （non-Keggin-type） aqueous solutions of Mo-V-phosphoric heteropoly acids HaPzMoyVx,Oh （HPA-x＇） were applied as homogeneous catalysts for the two-stage oxidation of TMP （2,3,6-trimethylphenol） by oxygen into TMQ （2,3,5-trimethyl-l,4-benzoquinone）, the latter being the key intermediate in the synthesis of vitamin E. The TMQ yield was analyzed regarding solvent type, reaction temperature, molar HPA-x ＇：TMP ratio, and the concentration of vanadium （V） in the HPA-x＇ solution. The TMQ yield was found to depend strongly on the catalyst redox potential and the rate of electron transfer. The results obtained enabled to establish the optimal reaction conditions as well as to suggest the reaction mechanism. In the target reaction, which proceeds in the two-phase system, the TMQ yield is higher than 99%. After phase separation, the catalyst is rapidly regenerated by oxygen and reused.展开更多
文摘Raman spectroscopy was applied to investigate the speciation in both single and mixed solutions of molybdate and vanadate at pH values from 10.0 to 1.0. Evidence was obtained for the difference of existing forms between these two elements. Vanadium mainly exists as （VO3）n^n- while Mo is MoO4^2- in the pH range of 9.0-7.5. This difference is the theoretical basis for many available separation process. The species in the binary system was identified by comparing the Raman spectra with that in the single systems. Molybvanadates are formed below pH=6.5, which may partly be ascribed to the replacement of V atoms by Mo atoms in some V-O-V groups. Vanadium mainly exists as the decavanadate species in the pH range of 6.0-2.0. The predominant species of Mo are heteropolyanions having structural features of heptamolybdate rather than MosO26^4- and Mo36O112^8- which are the predominant Mo species in single solution at pH=2.0-1.0.
基金grant from the Institute of Education of Henan Province (No: 20011500024) and Outstanding Youth Foundation of Henan Province
文摘A 1D chain-like organic/inorganic composite material with polyoxovanadates serving as building blocks has been synthesized by the reaction of cyclohexylamine with vana- dium pentoxide, and characterized by IR, UV spectra and TG-DTA technique. The title compound (C30H70N5O15V5, Mr = 995.61) crystallizes in orthorhombic, space group P212121 with a = 6.0093(12), b = 26.780(5), c = 27.979(6) ? V = 4502.6(16) 3, Z = 4, Dc = 1.461 g/cm3, F(000) = 2060, = 1.063 mm-1, R = 0.0651 and wR = 0.1084 for 3426 observed reflections (I > 2(I)). Single-crystal X-ray structural analysis indicates that the title compound consists of five proto- nated cyclohexylamine molecules and a polyoxovanadate anion of V5O155-. In addition, the results of IR spectra and single-crystal X-ray diffraction exhibit that there exists comparatively stronger interaction between the organic groups and polyoxovanadate anion in solid state. Adjacent structure units are bridged through corner-sharing oxygen atoms of VO4 tetrahedra to construct a novel one-dimensional zigzag infinite linear chain arrangement. The curves of TG- DTA elucidate that the process of weight loss of the title compound is divided into two stages, and also reveal that the framework of polyoxovanadate anion decomposes at 473.0 ℃.
文摘In the present study, the modified （non-Keggin-type） aqueous solutions of Mo-V-phosphoric heteropoly acids HaPzMoyVx,Oh （HPA-x＇） were applied as homogeneous catalysts for the two-stage oxidation of TMP （2,3,6-trimethylphenol） by oxygen into TMQ （2,3,5-trimethyl-l,4-benzoquinone）, the latter being the key intermediate in the synthesis of vitamin E. The TMQ yield was analyzed regarding solvent type, reaction temperature, molar HPA-x ＇：TMP ratio, and the concentration of vanadium （V） in the HPA-x＇ solution. The TMQ yield was found to depend strongly on the catalyst redox potential and the rate of electron transfer. The results obtained enabled to establish the optimal reaction conditions as well as to suggest the reaction mechanism. In the target reaction, which proceeds in the two-phase system, the TMQ yield is higher than 99%. After phase separation, the catalyst is rapidly regenerated by oxygen and reused.
