Search Results
O 40 ·16H 2 O (sample A in Table 1 ) and silver nitrate were obtained from Aldrich. All reagents were analytical grade. Besides, fumed silica-aerosil A300 (Oriana, Ukraine) was utilized as support. 1-Octene, 1,7-octadiene, and chlorbenzene (solvent
DTA and X-ray powder diffraction methods were used to study the phase equilibria established in the V9Mo6O40-FeVMoO7 system up to 1000° throughout the whole component concentration range. The experimental results are presented in the form of a phase diagram.
Abstract
The aim of this study is to investigate the influence of some monovalent counter-ions (NH4 +, K+ and Cs+) on thermal behavior of polyoxometalates derived from H3PMo12O40 (HPM) and H4PVMo11O40 (HPVM) by replacing the protons. The IR and UV-VIS-DRS spectra of some acid and neutral NH4 +, K+, Cs+ salts, which derived from HPM and HPVM, confirmed the preservation of Keggin units (KU) structure. The X-ray diffraction spectra clearly showed the presence of a cubic structure. The non-isothermal decomposition of studied polyoxometalates proceeds by a series of processes: the loss of crystallization water; the loss of O2 accompanying with a reduction of V5+→V4+ and Mo6+→Mo5+; the loss of constitution water started at 360C for HPVM salts and 420C for HPM salts; the decomposition of ammonium ion over 420C with NH3, N2 and H2O elimination and simultaneous processes of reduction (V5+→ V4+ and Mo6+→ Mo5+ or Mo4+) associating with endothermic effects; reoxidation of Mo5+, Mo4+ and V4+with a strong exothermic effect; destruction of KU to the oxides: P2O5, MoO3 and V2O5 and the crystallization of MoO3.
Abstract
DTA and XRD methods were applied in studies on phase equilibria established in the system V9Mo6O40-AlVMoO7 up to 1000C over the whole component concentration range. The results were presented in the form of a phase diagram.
Abstract
The V9Mo6O40−Cr2(MoO4)3 system has been investigated using the differential thermal analysis (DTA) and X-ray phase diffraction methods. The system has been found not to be a real two-component system over the whole component system.
Phase equilibria have been established in the solid state in the V9Mo6O40-Cr2O3 system. The results obtained have permitted to state that the system of interest, in the subsolidus area, is not a real two-component system in the whole component concentration range.
Abstract
This paper reports a comparative study of the non-isothermal decompositions of the heteropolyacids HPM and HPVM, with structures consisting of Keggin units (KUs). Non-isothermal analysis at low heating rates demonstrated the existence of 4 crystal hydrate species, depending on the temperature. The stability domains of the anhydrous forms of HPM and HPVM were found to be 150–380°C, respectively. Processing of the TG curves obtained at different heating rates by the Ozawa method revealed that the decomposition of anhydrous HPM takes place according to a unitary mechanism, whilst for anhydrous HPVM two mechanisms are observed. Thus, the first part of the constitution water is lost simultaneously with the departure of vanadium from the KU as VO2+, while the second part is lost at higher temperatures as in the case HPM.
PW 12 O 40 /SiO 2 catalyst showed high catalytic activity and high tolerance to sulfur and nitrogen compounds in the hydrocracking reaction of n -decane. The main reason was that the hydrogen spillover effect happened on the catalyst surface, which
40 ·20H 2 O, H 4 SiW 12 O 40 ·24H 2 O, H 3 PMo 12 O 40 ·18H 2 O, Na 3 PW 12 O 40 ·18H 2 O and Ca 2 SiW 12 O 40 ·16H 2 O were purchased from Sinopharm Chemical Reagent Co., Ltd. Acenaphthene (97%) and anhydrous AlCl 3 were sublimated before used. All
completely substituted by tellurium and investigate their catalytic performance for the partial oxidation of isobutane. Experimental Catalyst preparation A series of H 3+x PMo 12−x V x O 40 (x = 0
