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21.
L. Cherif F-Z. El-Berrichi A. Bengueddach P. Tougne J. Fraissard 《Colloids and surfaces. A, Physicochemical and engineering aspects》2003,220(1-3):83-89
The structural evolution of Y zeolite (Si/Al 2.17) weakly dealuminated by hexafluorosilicate (Si/Al 3.13), denoted YD, and exchanged with calcium (CaYD), has been studied after acid–base treatments at 80 °C close to the cation exchange conditions. The stability of the samples was followed by X-ray diffraction and solid-state NMR of 29Si and 27Al; YD zeolite was completely destroyed by treatment with acid pH 2.5 and suffered serious degradation on treatment with alkali at pH 11.8. The introduction of calcium improved the stability of the zeolite in acid and base. In acid CaYD was not destroyed until pH 1. At pH 2, silicon and aluminium were extracted and an amorphous phase was formed. Base treatment at pH 13 did not affect the calcium-exchanged zeolite. 相似文献
22.
本文报道了一种光敏型的阳离子表面活性剂(AZO),其分子结构中含有偶氮苯基团,并研究了光照对表面活性和泡沫性能的影响。经紫外光照射后,表面活性剂的饱和吸附量(Гmax)减小,临界胶束浓度(cmc)、最低表面张力(γcmc)和分子极限占有面积(Amin)增大;气泡数目增多,直径变小,发泡能力和泡沫稳定性降低。实验结果证实,该表面活性剂的表面活性和泡沫稳定性可以用光照进行调控。 相似文献
23.
ZheMingNI WeiHuaYU ShaoFenZHAO ZhongHuaGE 《中国化学快报》2004,15(8):989-992
Magnesium aluminium hydrotalcite (Mg-Al-HT) with molar ratio of Mg-to-Al of 3 to 1 was prepared and characterized by X-ray diffraction (XRD) and infrared spectra (IR). The performances of Mg-Al-HT for the adsorption and desorption of NOx were studied. The results indicated that the adsorption capacity of the hydrotalcite for NOx was 1398.2mg/g, and it was higher than the acticarbon‘s. The adsorption capacities depended on adsorption time and temperature.Mg-Al-HT could be regenerated by thermal decomposition, and the adsorption efficiency had not changed markedly after three cycles. 相似文献
24.
25.
Formation of mixed adsorbed layers was tested for ternary liquid mixtures containing methanol or acetone and the binary solvent benzene+n — heptane. The specific excess adsorption isotherms from the liquid phase were measured on silica gel, silanized silica gel and aluminium oxide. The experimental adsorption data are discussed on the basis of the changes in the mixed solvent composition. 相似文献
26.
β-Glucosidase was covalently immobilized alone and coimmobilized with cellulase using a hydrophilic polyurethane foam (Hypol®FHP 2002). Immobilization improved the functional properties of the enzymes. When immobilized alone, the Km for cellobiose of β-glucosidase was decreased by 33% and the pH optimum shifted to a slightly more basic value, compared to the free enzyme. Immobilized β-glucosidase was extremely stable (95% of activity remained after 1000 h of continuous use). Coimmobilization of cellulase and β-glucosidase produced a cellulose-hydrolyzing complex with a 2.5-fold greater rate of glucose production for soluble cellulose and a four-fold greater increase for insoluble cellulose, compared to immobilized cellulase alone. The immobilized enzymes showed a broader acceptance of various types of insoluble cellulose substrates than did the free enzymes and showed a long-term (at least 24 h) linear rate of glucose production from microcrystalline cellulose. The pH optimum for the coimmobilized enzymes was 6.0. This method for enzyme immobilization is fast, irreversible, and does not require harsh conditions. The enhanced glucose yields obtained indicate that this method may prove useful for commercial cellulose hydrolysis. 相似文献
27.
The system BaF2/AlF3 is investigated by X-ray and D.T.A., and the liquid-solid phase diagram is established. Five ternary fluorides are disclosed: trimorphic BaAlF5, Ba3Al2F12, Ba5AlF19, polymorphic Ba3AlF9 and Ba5AlF13. Neutron thermodiffractometry experiments are performed to specify some parts of the diagram. The cell parameters of the fluorides are given and the results are discussed and compared with those of the previous works. 相似文献
28.
29.
F. M. Bautista J. M. Campelo A. Garcia D. Luna J. M. Marinas A. A. Romero M. R. Urbano 《Reaction Kinetics and Catalysis Letters》1997,62(1):47-54
The vapor-phase catalytic alkylation of phenol with methanol and dimethyl carbonate on a series of differently prepared CrPO4 (Cr/P=1) and CrPO4-AlPO4 (CrAIP) catalysts, has been studied at different temperatures (473–673 K). The reaction is first order in phenol, giving
a mixture of O- and C-alkylated products (C-alkylation taking place preferentially at theortho-position). Moreover, dimethyl carbonate is a better methylating agent than methanol. 相似文献
30.
A. M. George N. C. Mishra M. S. Nagar N. C. Jayadevan 《Journal of Thermal Analysis and Calorimetry》1996,47(6):1701-1708
Thermal decomposition of the amorphous coprecipitate of yttrium and aluminium hydroxides forming yttrium aluminium garnet has been investigated employing thermal analyses, X-ray diffraction and IR spectroscopy. On heating, the coprecipitate progressively loses water forming a stable but highly disordered hydroxy garnet which crystallizes at 1180 K and decomposes to YAG at 1290 K. Nucleation of the crystalline phase appears to begin at 800 K.The authors thank Dr. P. V. Ravindran of the Analytical Chemistry and Shri N. K. Kulkarni of the Fuel Chemistry Divisions of BARC for their assistance in the thermoanalytical experiments. 相似文献