| Anthraquinone is an important chemical raw materials and chemical intermediates. It has been widely used. But the uses of classical homogeneous catalysts, such as AlCl3, H2SO4 result in the heavy environmentally pollution. Therefore, to develop a new style solid acid catalyst which is environmentally friendship and no pollution used becomes an important and critical work.In this paper, in order to reduce modifying time and heighten catalyst efficiency, Hβzeolites were modified by different metal ions under microwave radiation heating instead of conventional heating and the effect was admirable. The optimal conditions for NH4+ exchange of beta zeolite were found: NH4+ exchange times were 1; NH4+ exchange power was 390W, time 15min; dry power was 325W, time 20min; calcinations temperature was 550℃, time 5h. The prepared catalysts were used to catalyze the synthesis of anthraquinone with benzene and phthalic anhydride. The optimum reaction conditions were: n(benzene)/n(phthalic anhydride) was 16/1, catalyst amount of 8.0% on the total mass of reactants; reaction temperature was 250℃, time 5h; stirring speed was 500r/min. The conversion rate of phthalic anhydride could reach up to 31.68%, and selectivity 87.66%, at these best conditions. Compared with the conventional heating method, the results showed that the microwave radiation was more effective for the modification of zeolite, and the catalytic performance of modified zeolites were improved. Microwave radiation did not destroy the crystal structure ofβzeolite.Beta zeolite was modified by Al2(SO4)3, TiCl4, Ti(SO4)2, InCl3, Ce(NH4)2(NO3)6 and FeCl3, under microwave radiation, respectively. It was discovered that zeolites modified with 0.5mol·L-1 Al2(SO4)3,0.04 mol·L-1 InCl3 and 0.4mol·L-1TiCl4 had good catalytic activity for the reaction, and the conversion ratio of phthalic anhydride could reach up to 41.89%, 49.09% and 40.41%, respectively; selectivity reached 92.78%, 75.35% and 90.16%. However, the catalytic effect of zeolites modified by other metal salts, such as Ti(SO4)2, Ce(NH4)2(NO3)6, FeCl3 were ineffective. It was regenerated to investigate its lifetime. The catalytic activity of reused beta zeolite could be resumed after 10 times regeneration, and the yield and selectivity of anthraquinone were not found significantly decreased. Py IR, NH3 TPD, XRD and BET technologies were used to characterize the modified catalysts.The experiment shows that the mediate strong acid sites were the active sites for this reaction; L acid was the main acid sites on the surface of modified zeolite; the right proportion of acid of L and B acid was important for the reaction.The product was separated and purified by the different solvents, and it was found that dimethyl sulfoxide (DMSO) was a suitable solvent. The solubility of the phthalic anhydride was 8.57, while the solubility of anthraquinone was only 0.038. The purity of isolated anthraquinone was over 96%, and the recovery ratio was over 92%.
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