Acylation Of Aromatic Compounds Catalyzed By Zeolite Molecule Sieves

Anthraquinones have been widely used as final products or intermediates in the field ofdyes, pharmaceuticals, agricultural chemicals and so on, and play an important role in thenational economy. Friedel-Crafts acylation is the primary method for the preparation ofanthraquinones, which involves the employment of AlCl₃ and H₂SO₄ as the homogeneousacid catalysts. Application of those catalysts in industries has caused environment pollutionand the waste of resource. Therefore, the study of developing new catalysts for theFriedel-Crafts acylation to form anthraquinones becomes important and critical. In thisresearch, H-type zeolite molecule sieves have been employed as catalysts to synthesizeanthraquinone and 2-methyl anthraquinone.2-methyl anthraquinone has been synthesized via the Friedel-Crafts benzoylation oftoluene catalyzed by HZ-1 zeolite through an intermittent liquid-solid reaction style, andcharacterized by HPLC, MS and NMR techniques. Detailed study on the effects of differentzeolite molecule sieves, solvents and modification of catalyst on acylation has shown that thebest condition for synthesis of 2-methyl anthraquinone is HZ-1 zeolite as the catalyst, and nosolvent involved.The influence of preparation conditions of HZ-1 zeolite such as calcined temperature andion-exchanged times on the catalytic performance has been investigated. Besides, NH₃-TPD,XRD, pyridine-IR and XRF have been employed to account for the change of SiO₂/Al₂O₃ratio, crystallinity and acid properties of HZ-1 zeolite which will impact the catalyticperformance. The twice exchanged HZ-1 zeolite calcined at 550℃exhibite optimalcatalytic capability. The reaction conditions have also been optimized by adjusting catalystdosage, reactants ratio, reaction temperature and reaction time. Under those optimizedconditions, the conversion of phthalic anhydride can reach as high as 71.3% with 91.3%selectivity for 2-methyl anthraquinone. Moreover, the catalytic activity of reused HZ-1zeolite is found to decrease distinctly and can be resumed on the whole after regeneration.The benzoylation of benzene catalyzed by HZ-1 zeolite has also been studied roundly.The reaction conditions have also been optimized by adjusting ion-exchanged times, catalystdosage, reactants ratio, reaction temperature and reaction time. Under those optimizedconditions, the conversion of phthalic anhydride can reach as high as 57.1% with 79.3%selectivity for anthraquinone.