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61.
Charles S. Oakes John M. Simonson Robert J. Bodnar 《Journal of solution chemistry》1995,24(9):897-916
Relative densities of CaCl
2
(aq) with 0.22ml(mol-kg–1)6.150 were measured with vibrating- tube densimeters between 25 and 250°C and near 70 and 400 bars. Apparent molar volumes V calculated from the measured density differences were represented with the Pitzer ioninteraction treatment, with appropriate expressions chosen for the temperature and pressure dependence of the virial coefficients of the model. It was found that the partial molar volume at infinite dilution V
o
, and the second and third virial coefficients B
V
and C
V
, were necessary to represent V near the estimated experimental uncertainty. The ionic-strength dependent (1)v term in the B
V
coefficient was included in the fit. The representation for V has been integrated with respect to pressure to establish the pressure dependence of excess free energies over the temperature range studied. The volumetric data indicate that the logarithm of the mean ionic activity coefficient, ln ±(CaCl
2
), increases by a maximum of 0.3 at 400 bars, 250°C, and 6 mol-kg–1 as compared with its value at saturation pressure. 相似文献
62.
Photocatalytic oxidation of water is a promising method to realize large-scale H2O2 production without a hazardous and energy-intensive process. In this study, we introduce a Pt/TiO2(anatase) photocatalyst to construct a simple and environmentally friendly system to achieve simultaneous H2 and H2O2 production. Both H2 and H2O2 are high-value chemicals, and their separation is automatic. Even without the assistance of a sacrificial agent, the system can reach an efficiency of 7410 and 5096 μmol g–1 h–1 (first 1 h) for H2 and H2O2, respectively, which is much higher than that of a commercial Pt/TiO2(anatase) system that has a similar morphology. This exceptional activity is attributed to the more favorable two-electron oxidation of water to H2O2, compared with the four-electron oxidation of water to O2. 相似文献
63.
E. Fleury J. Dubois C. Léonard J. P. Joseleau H. Chanzy 《Cellulose (London, England)》1994,1(2):131-144
Solutions of cellulose diacetate (CDA) from two sources (cotton linters and wood pulp Floranier) were analysed in various solvents by size exclusion chromatography (SEC). Without special precautions, the SEC chromatograms presented three peaks — or prehumps — before the main polymer peak. The first prehump which could be eliminated by ultracentrifugation corresponded to microgels whose sugar composition was determined. These microgels were also investigated by electron microscopy, X-ray and electron diffraction analysis. They corresponded mainly to cellulose triacetate (CTA-II) in the case of CDA from cotton linters and a mixture of CTA-II and xylan diacetate (XDA) in the case of CDA from the wood pulp Floranier. The second and third prehumps could be attributed to ionic effects corresponding to the association of remaining sulfate groups on the CDA molecules with residual calcium. It was found that these ionic effects could be eliminated by the addition of LiBr or LiCl to the elution solvents. This led to chromatograms devoid of prehumps.Presented in part at the Cellulose '91 meeting in New Orleans. 相似文献
64.
Alkanes (cyclohexane, hexane, heptane isomers) are effectively oxidized in CH3CN at 20–70°C by hydrogen peroxide when catalyzed by a Bu4NVO3-pyrazine-2-carboxylic acid system. Alkyl hydroperoxide is the main product; an alcohol and a ketone or an aldehyde are also formed. Under these conditions benzene is oxidized to give phenol, while alkyl benzenes yield oxygenation products both of the ring and the side chain. It has been assumed that the interaction of H2O2 with VO3
– gives rise to generation of HO radicals and other radical-like vanadium containing species that abstract a hydrogen atom from an alkane, RH. The radical R. formed reacts with O2 to produce ROO. which is then transformed to alkyl hydroperoxide.Presented at the VIII International Symposium on Homogeneous Catalysis (Amsterdam, 1992).Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 64–68, January, 1993. 相似文献
65.
66.
67.
Qing Hua Zhang Shou Feng Wang Zi Qiang Lei 《中国化学快报》2007,18(1):4-6
Sn-aniline complex was prepared by a simple procedure.Cyclic and acyclic ketones were oxidized into lactones or esters with very high selectivity and yield with 30% hydrogen peroxide in the presence of Sn-aniline complex. 相似文献
68.
We report herein an efficient catalytic epoxidation reaction for the synthesis of epoxyketone (tert-butyl ((S)-4-methyl-1-((R)-2-methyloxiran-2-yl)-1-oxopentan-2-yl)carbamate), which is an important synthetic intermediate of carfilzomib. 相似文献
69.
The oxidative polycondensation of 4-[(pyridin-3-ylimino)methyl]phenol (4-PIMP) with O2, H2O2, and NaOCl was studied in an aqueous alkaline medium between 50°C and 90°C. Oligo-4-[(pyridin-3-ylimino)methyl]phenol (O-4-PIMP)
prepared was characterized by 1H-NMR, 13C-NMR, FT-IR, UV-VIS, size-exclusion chromatography, and elemental and thermal analyses techniques. At the optimum reaction
conditions, the yield of O-4-PIMP was 18.9%, 39.4%, and 46.8% using H2O2, O2, and NaOCl oxidant, respectively. According to the TG analysis, the initial degradation temperature of O-4-PIMP was 218°C,
which was by 50°C higher than that of 4-PIMP. Thermal analyses of 4-PIMP and O-4-PIMP were carried out in N2 atmosphere at 15–1000°C. The highest occupied molecular orbital, the lowest unoccupied molecular orbital, and electrochemical
energy gaps of 4-PIMP and O-4-PIMP were determined from the onset potentials for n-doping and p-doping, respectively. Also, optical band gaps of 4-PIMP and O-4-PIMP were determined according to UV-VIS measurements. 相似文献
70.
Dawson结构钼钒磷杂多化合物对苯酚过氧化氢羟化作用的研究 总被引:14,自引:0,他引:14
Dawson结构钼钒磷杂多化合物对苯酚过氧化氢羟化作用的研究于剑锋,杨宇,吴通好,孙家锺(吉林大学化学系理论化学研究所,长春,130023)关键词Dawson结构钼钒磷杂多化合物,苯酚羟化,过氧化氢苯二酚(DBH)是重要的化工原料.由芳香化合物羟化制... 相似文献