Comparative study on the catalytic performance of zeolite catalysts with different topologies in 2-methylnaphthalene acylation reaction
2,6-Naphthalenedicarboxylic acid is an important monomer for the synthesis of special polyester polyethy-lene naphthalate(PEN).2,6-Naphthalenedicarboxylic acid can be obtained by acylation,oxidation and purifica-tion of 2-methylnaphthalene.The acylation reaction is very important in this process.At present,Lewis acid AlCl3 is usually used as the catalyst in the 2-methylnaphthalene acylation reaction.The catalytic system has high conversion rate and good selectivity,but the reaction quenching process will produce a large amount of acidic aluminum-contai-ning wastewater,and the reaction system has high requirements for the material of the equipment.Based on the ad-vantages of molecular sieves such as high selectivity,good thermal stability,easy separation from products and good catalytic activity in various acylation reactions,2-methyl-6-butyrylnaphthalene was prepared by acylation reaction of 2-methyl-naphthalene and butyric anhydride catalyzed by molecular sieve solid acid.The structure and properties of the catalysts were characterized by XRD,BET,SEM and NH3-TPD.The catalytic properties of H-Beta,H-ZSM-5 and H-MCM-22 molecular sieves with BEA,MFI and MWW skeleton topologies were compared.The reaction mecha-nism was discussed and the reuse performance of molecular sieve catalyst was investigated.The results showed that compared with H-ZSM-5 zeolite with ten-membered ring characteristic channel,H-Beta zeolite with twelve-membered ring characteristic channel showed better catalytic activity,and the zeolite with BEA skeleton topology had higher se-lectivity.Under the catalysis of H-Beta molecular sieve,the reaction conditions were as follows:the molar ratio of 2-methylnaphthalene to butyric anhydride was 1∶1;2-methylnaphthalene was 0.05 mol,catalyst was 2 g,reaction temperature was 190℃,reaction time was 10 h,the conversion of butyric anhydride was 57.42%,the selectivity of 2,6-position was 44.98%,the selectivity of 2,7-position was 28.62%.The conversion rate of butyric anhydride was 31.66%under the catalytic system of H-MCM-22 molecular sieve,but the product was not dominated by the de-sired target.H-MCM-5 molecular sieve is not suitable for this system due to its small pore size.In this liquid phase system,the conversion of butyric anhydride is less than 3%,and no target is formed.Molecular sieve has excellent recycling performance.After the used H-Beta molecular sieve was regenerated by high temperature calcination,the performance of the catalyst was restored,which fully reflected the advantages of recyclability and reusability of the ze-olite molecular sieve catalyst.This study provides a promising molecular sieve catalytic system for the preparation of high-end polyester monomers from China's abundant naphthalene-containing resources.
万方数据
维普
