| Supported heteropolyacid catalysts, such as 12-tungstophosphoric acid (PW)/γ-Al2O3, PW/actived carbon(C), PW/dealuminated USY and PW/MCM-41, wereprepared by impregnation at room temperature. Their physicochemical propertiessuch as the dispersion of PW on the support, specific surface area, pore structure,thermal stability and acidity were characterized by X-ray diffraction (XRD), N2adsorption isotherm, infrared-ray spectrum (IR), thermogravimetry-differentialscanning calorimetry (TG-DSC) and temperature programmed desorption of ammonia(NH3-TPD). The catalytic behavior of the catalysts was tested in alkylation ofnaphthalene with isopropanol, and the relation between the physicochemicalproperties of the catalysts and their activity and selectivity have been discussed indetail.For the series of PW/γ-Al2O3 catalysts, the acid amount increases with theincrease of the PW loading in catalyst. PW could disperse on the surface of γ-Al2O3when the PW loading is as high as 40% by weight. 40%PW/γ-Al2O3 possesses thelargest acid amount. Results of isopropylation of naphthalene over PW/γ-Al2O3indicate that the optimum PW loading, activation temperature and reactiontemperature are 40%, 300℃ and 200℃, respectively. The highest conversion ofnaphthalene is 71.7% and the selectivity for β,β′ I products is 82.7%. The low PWloading in catalyst favors the high selectivity for 2,6-DIPN.The acid amount is improved by the increase of PW loadings in PW/C catalysts.When the PW loading is as high as 30wt%,PW could highly disperse on the surfaceof C, and it shows the highest acid amount. Compared with the high specific surfacearea of C, 707m2?g-1, 30%PW/C still has a high surface area of 367 m2?.g-1. Theresults of isopropylation of naphthalene over PW/C show that the optimum PWloading is 30%, the activation temperature is 300℃ and reaction temperature is 200℃.After 150 min of reaction, the conversion of naphthalene reaches 92.4%, and 360 minlate, the conversion is nearly 100%.Treated by steam and/or with HCl leaching, calcinated followed by calcinations - i -ABSTRACTat a proper temperature, dealuminated USY keeps high relative crystallinity becauseof the rearrangement of zeolite framework and the modification of zeolite frameworkthrough moving of silica species. USY dealuminated by the above method results insecondary mesopore system and lower acidity. The catalyst acidity and pore structurerelate closely with the catalytic performance in isopropylation of naphthalene. PWsupported on dealuminated USY zeolite does not improve its acidity and consequentactivity apparently, because the pore size and surface area decrease, and alsoselectivity for 2,6-DIPN decreases slightly. Reaction results of isopropylation ofnaphthalene indicate that dealuminated USY zeolite exhibits higher activity andselectivity for 2,6-DIPN, as compared to the unmodified USY sample. The optimumactivation temperature is 550℃ and reaction temperature is 160℃, and the optimalactivity and selectivity for 2,6-DIPN of dealuminated USY zeolite, treated by steamand HCl leaching, are 92.3% and 85.3%, respectively, with the molar ratio of Si to Albeing 10.5. After the fourth reaction cycle, the conversion of naphthalene still reaches70%.The characteristics of MCM-41 supported PW catalysts by saturation adsorptionare very different form those by impregnation, which is revealed by XRD results. Thespectra of XRD show the same diffraction peaks of PW/MCM-41 by saturationadsorption as those of MCM-41, while the spectra of XRD display the different peaksof PW/MCM-41 by impregnation from those of MCM-41. Compared with thespecific surface area of MCM-41, 840m2?g-1, 30%PW/MCM still possesses aconsiderable value as high as 439m2?g-1. NH3-TPD shows that the acid amount of30%PW/MCM prepared by the impregnation is the largest. XRD also indicates thatPW could highly disperse on the surface of MCM-41 and has the highest acid amountuntil the concentration of PW is 30% by weig...
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