Study On Phthalic Anhydride Process Synthesis Of Anthraquinone Catalyzed By Zeolite Molecule Sieves

Anthraquinone (AQ) is an important organic dye intermediate. It has a great variety and been widely used, so it plays an important role in the organic dye field. To develop zeolite molecular sieve solid acid catalyst in stead of the traditional Lewis acid catalyst can simplify the synthesis techniques of anthraquinone and realize the green synthesis, which is valuable and has practical significance. In this paper, the catalytic properties of four kinds of zeolite molecular sieves were studied in acylation reaction to synthesize anthraquinone by benzene and phthalic anhydride, the appropriate HM-3 zeolite molecular sieves was selected, on which the modification was studied. The structures and acidity of modified catalysts were characterized by Pyridine-IR, NH3-TPD, XRD, BET. A preliminary investigation was carried out on the relationship between the structures and catalytic performances of different modified catalysts.In this paper, the anthraquinone was synthesized by the Friedel-Crafts acylation with benzene and phthalic anhydride using HM-3 zeolite as the catalyst through an intermittent liquid-solid reaction style. The products were analyzed by GC. The effects of HM-3 molecular sieve preparation conditions on the catalytic activities was investigated, and it was concluded that : the best H-exchange times was 2 , H-exchange temperatures was 90℃, calcinations temperature was 550℃; Then the reaction conditions were discussed and the optimized parameters were determined: reaction temperature was 250℃, reaction time was 5h, n(benzene)/n(phthalic anhydride) was 4/1, catalyst dosage was 42.2% of phthalic anhydride in reactants, stirring speed was 500r/min, and the yield of anthraquinone can reach up to 23.64% at this best conditions. At the same time, the catalytic mechanism to synthesis anthraquinone with zeolite molecular sieve was studied, the results of experiments and characterization showed that B acid sites played the most important role in catalysis reaction, and L acid sites had the synergistic effects.The HM-3 molecular sieve was modified by inorganic acid salt, inorganic proton acids, solid superacids of zirconium system, cerium oxide, and aluminum salts, and it was concluded that: (1)The best modified conditions by (NH4)2SO4: concentration was 0.75mol/L, modification temperature was 90℃and calcinations temperature was 550℃. The catalytic performance of modified molecular sieve was improved, the yield of anthraquinone reached to be 28.18%, and the selectivity of anthraquinone was 94.7%. (2)The catalytic activity of HM-3 molecular sieve modified by inorganic proton acids was reduced but had little effects on selectivity of anthraquinone. (3)The activity and selectivity of HM-3 zeolite modified by solid superacids of zirconium system were both reduced. (4)The catalytic activity of HM-3 molecular sieve modified by cerium oxide was reduced, but the selectivity of anthraquinone was raised to 98.75%. (5)During the modifications by aluminum salts, catalytic activities of HM-3 molecular sieve modified by AlCl3 and Al2(SO4)3 were increased at different degrees, and the effects on selectivity of anthraquinone was not obvious. The best modification conditions of Al2(SO4)3 was as follows: concentration was 0.2mol/L, ion-exchange temperature was 30℃, calcinations temperature was 550℃. The yield of anthraquinone was 30.14% at these conditions, and the selectivity of anthraquinone was 94.61%.