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1.
XU Jun YAN Ai-Zhen XU Qin-Hua Department of Chemistry Nanjing University Nanjing Jiangsu China 《中国化学》1995,(2)
The strength of basic sites has been measured by pyrrole-IR on alkali metal cation exchanged β and X zeolites, as well as NaOH loaded Naβ. The influence of cation type and the structure of zeolites on their basicity has been studied. The acidic and basic properties of the samples were investigated by NH3-TPD and isopropanol reaction. It was shown that the strength of basic sites on samples could be characterized by the shift of vNH band in the pyrrole-IR spectra. The framework oxygen charges were calculated from the Sanderson electronegativity. The changes in basic properties with various alkali metal cation are consistent with the changes of local oxygen charges of the zeolite framework. 相似文献
2.
Shufeng Zuo 《Applied Surface Science》2006,253(5):2508-2514
Al-pillared clays supported rare earths (RE/Al-PILC) are prepared and used as supports of palladium catalysts for deep oxidation of low concentrations of benzene (130-160 ppm). The supports and catalysts are characterized by X-ray powder diffraction (XRD), FT-IR, BET, transmission electron microscopy (TEM) and temperature-programmed reduction (H2-TPR). The results show that Al-pillaring results in a strong increase in the basal spacing (d0 0 1) from about 1.2 to 1.8 nm, and an increase in the BET surface area from 63.6 (±3.2) to 238.8 (±11.9) m2/g. Activity tests of deep oxidation of low concentration benzene show catalysts supported on Al-PILC and RE/Al-PILC are obviously more active than that on raw clay. Pd/6% Ce/Al-PILC, in particular, can catalyze the complete oxidation of low concentration benzene at a temperature as low as about 290 °C. 相似文献
3.
Zhaohui Wang 《Thermochimica Acta》2004,414(1):31-33
Microcalorimetric measurements of excess molar enthalpies, at 298.15 K, are reported for the four binary systems formed by mixing 1-hexene with the cycloalkanes: cyclohexane and methylcyclohexane, and with the aromatic hydrocarcons: benzene and toluene. Smooth Redlich-Kister representations of the results are presented. It was found that the Liebermann-Fried model also provided good representations of the results. 相似文献
4.
Kai-li Xiang 《计算数学(英文版)》2002,(2)
1. IntroductionWe consider a class of direct hybrid methods proposed in [11 for solving the second orderinitial value problemy" = f(t,y), y(0),y'(0) given (1.1)The basic method has the formandHere t. = nh and we define t.l.. = t. I aih, i = 1, 2 and n=0,1… 相似文献
5.
E. E. Ergozhin N. A. Bektenov A. K. Mekebaeva N. N. Chopabaeva 《Chemistry of Natural Compounds》2003,39(3):299-302
Phosphorus-containing cellulose cation exchangers were synthesized by reaction of wood cellulose with orthophosphoric acid and the ternary polymer from glycidylmethacrylate, styrene, and maleic anhydride. The effects of the ratio of reactants, temperature, and duration of the reaction on the phosphorylation and exchange capacity of the modified cellulose material were studied. 相似文献
6.
The sorption, diffusion, and pervaporation (PV) properties of benzene/cyclohexane (Bz/Cx) mixtures on cation-exchange membranes containing copper ions (Cu(II)) were investigated. The equilibrium sorption isotherms of pure vapors in the membranes and the partial solubility of binary solutions in the membranes were described using the UNIQUAC model. The τiM and τMi values were 0.978 and 0.591 for Bz, and 0.922 and 0.475 for Cx. The transient regimes of vapor sorption were employed to calculate the concentration-dependent diffusion coefficients. Long’s model sufficiently explained the diffusivity of Bz and Cx in the membranes. The pre-exponential factors were 3×10−13 m2/s and the plasticization factors were 3.0 and 3.6 for Bz and Cx, respectively. Excellent agreement was found with the experimental results applying the solubility and diffusivity data to simulate the pervaporation performance (flux and selectivity) using the modified Maxwell–Stefan equation. The membrane containing Cu(II) demonstrates better facilitating capability for Bz transport than that with Na(I), mainly due to its preferential sorption property toward Bz. Replacing Na(I) with Cu(II) into a Neosepta membrane resulted in better separation efficiency and higher Bz flux throughout the entire Bz concentration range. 相似文献
7.
毛细管离子交换电色谱的分离行为 总被引:7,自引:0,他引:7
在离子交换毛细管色谱柱上实施电色谱,并对其分离行为进行了研究,采用75μm(i.d.)20cm的毛细管强阳离子交换柱(3μm)以NaH2PO4-H3PO4缓冲液为淋洗剂,紫外柱上检测(214nm)考察了流动相的pH值,有机改性剂及分离电压等因素对分离的影响,研究表明,不同的pH溶质的流出次序发生改变,随着有机改性剂含量增加,溶质的保留时间减小,而电渗流却增大,同时,对分离的柱效和方法的重现性进行了 相似文献
8.
The monodisperse, porous poly(chloromethylstyrene-co-divinylbenzene) beads of 7.9 microm were prepared by a single-step swelling and polymerization method. The seed particles prepared by dispersion polymerization exhibited good absorption of the monomer phase. Based on this media, a weak cation-exchange (WCX) stationary phase for HPLC was synthesized by a new chemically modified method. The prepared resin has advantages of biopolymer separation, high column efficiency, low column backpressure, high protein mass recovery, and good resolution for proteins. The dynamic protein-loading capacity of the synthesized WCX packings was 18.2 mg/g. Five proteins were separated in 3.0 min using the synthesized WCX stationary phase. The experimental results show that the obtained WCX resin has very weak hydrophobicity. The WCX resin was also used for the rapid separation and purification of lysozyme from egg white in 5.0 min with only one step. The purity and specific bioactivity of the purified lysozyme were found to be more than 93% and 70 245 U/mg, respectively. 相似文献
9.
本文采用表面活性剂十六烷基三甲基溴化铵(C16TABr,以下为1631),在(Na,K)OHSiO2C16TABrH2O体系中分别利用室温、水热及干粉法进行了纯硅MCM41中孔分子筛的合成,考察了阳离子Na+、K+对MCM41合成及稳定性的影响。通过XRD对结晶度的测定,发现NaMCM41的晶化速率明显高于KMCM41,而热稳定性和水热稳定性较差,且a0值小于后者。同时发现,就合成方法而言,室温法得到的产物具有很高的结晶度,利用水热法合成的样品的热稳定性明显较高,而干法得到的分子筛产品具有优良的水热稳定性。 相似文献
10.
Titration calorimetry was used to construct the solid-liquid equilibrium line in ternary systems containing the solute and an aqueous mixed solvent by measuring the heat of dissolution of the solid solute during successive additions of the liquid solvent. The plot of cumulated heats versus the mole ratio, nsolvent/nsolute, yields two (almost) linear increases of different slopes. These two lines represent successively the enthalpy of dissolution then the enthalpy of dilution of the medium; their intersection gives the solubility and the enthalpy of dissolution of the solute. Phase diagrams have been established over the whole concentration range for o-anisaldehyde, 1,3,5-trimethoxybenzene and vanillin, in water + methanol, +ethanol, or +n-propanol at 303, 313 and 318 K. 相似文献