Study On The Synthesis Of Anthraquinones Over Zeolite Molecular Sieves

The anthraquinones are very important fine chemicals for dyes and pigments, pharmaceuticals,additives of paper making,etc.The consumption of anthraquinones in the world is extremely enormous,and will increase in the future.The currently adopting method for industrial production is still the phthalic anhydride method including the AlCl₃ and concentrated H₂SO₄ as catalysts.However,the use of these catalysts induce the heavy environmentally pollution.The green revolution for the synthesis of anthraquinones determines whether the industry of anthraquinone dyes can last or not.To introduce catalytic technology into this field is a very effectual approach.Upon the previous successful research on the one-step synthesis of anthraquinone and 2-methyl anthraquinone catalyzed by HZ zeolite,and the further research on elevating the yield of anthraquinones will be investigated in this research.Ethylbenzene and o-xylene were used as aromatics and as solvent at the same time,and benzoylated with phthalic anhydride in liquid-solid phase over HZ zeolite were performed to synthesize 2-ethyl anthraquinone(2-EAQ) and 2,3-dimethyl anthraquinone(2,3-DMAQ) via one-step synthetic strategy,respectively.The reaction mixture was analyzed via HPLC and HPLC-MS,and the major products were confirmed by ¹H NMR techniques.Effects of reaction parameters like ion-exchange time of zeolite,dosage of catalyst,mole ratio of aromatics to phthalic anhydride,reaction temperature and reaction time were investigated in detail.Different times of ion-exchanged zeolite were characterized by NH_3^-TPD,Pyridine-IR, XRF,etc.Under the optimal reaction conditions,66.48%and 55.34%of yield for 2,3-DMAQ and 2-EAQ could be achieved,respectively.The effect of particle size of HZ catalyst on catalytic performance has been studied. Nanosized HZ was used as catalyst,ethylbenzene or o-xylene benzoylated with phthalic anhydride in liquid-solid phase to produce 2-EAQ and 2,3-DMAQ.Effects of reaction parameters like ion-exchange time of zeolite,dosage of catalyst,mole ratio of aromatics to phthalic anhydride,reaction temperature and reaction time were investigated in detail.The Nanozied and Microsized HZ catalysts were characterized by Electron microscopy,XRD, N_z-adsorption,NH_3^-TPD,Pyridine-IR,etc.The Nanosized HZ with 20-60 nm particle size exhibited higher catalytic activity than Microsized HZ due to its larger specific surface area and larger secondary pores.Under the optimal reaction conditions,73.56%and 60.11%of yield for 2,3-DMAQ and 2-EAQ could be obtained,respectively.The effect of different acylating reagents on catalytic performance has been explored. Micro HZ was used as catalyst,toluene or o-xylene benzoylated with phthalic acid in liquid-solid phase to produce 2-methyl anthraquinone(2-MAQ) and 2,3-DMAQ.Effects of reaction parameters like ion-exchange time and calcined temperature of zeolite,dosage of catalyst,molar ratio of aromatics to phthalic acid,reaction temperature and reaction time were investigated in detail.Zeolites calcined at different temperature were characterized by NH₃-TPD and Pyridine-IR.Under the optimal reaction conditions,79.94%and 82.15%of yield for 2,3-DMAQ and 2-MAQ could be obtained,respectively.The unreacted phthalic anhydride could be recycled via transforming into phthalic acid after reaction,and the acylating reactivity of phthalic acid is higher than phthalic anhydride,which either greatly elevated the once yield of anthraquinones or elevated the total yield of anthraquinones.The recovery properties of Nano and Micro HZ catalysts were investigated.The spent catalysts can be refreshed by temperature-programmed calcinations.