Selective Hydrogenation Of Phthalic Anhydride To Phthalide Over Lanthanum-Modified Nickel-based Catalysts

Phthalide is an important fine chemical intermediate, which has been widely used in pharmaceutical, pesticide and synthetic dyes industry. However, there is some of problem in serious environmental pollution, low yield for traditional methods of synthesis of phthalide, while phthalic anhydride catalytic hydrogenation method has been a green route for the synthesis of phthalide. The nickel-based catalyst used in phthalic anhydride catalytic hydrogenation has less selectivity to phthalide though it has the advantages of low price and high activity, so the preparation of catalysts with high selectivity to phthalide and optimization of reaction conditions is of great significance. In this paper, the preparation of lanthanum-modified nickel-based catalyst and its application in selective hydrogenation of phthalic anhydride to phthalide have been investigated.The lanthanum-modified supported nickel-based catalyst was prepared by impregnation method, and the catalysts were characterized by means of XRD and N2 physical adsorption, which were then used in catalytic hydrogenation reaction of phthalic anhydride. Firstly, the small scale hydrogenation of phthalic anhydride was carried out in 50 mL autoclave. The influence of amount of catalyst, the reaction solvent, lanthanum content, reaction temperature, and substrate concentration were investigated. The best hydrogenation activity was obtained over 40%Ni2%La/Al2O3 catalyst under the conditions of as 10 wt.% the catalyst amount,160 ℃,28 wt.% of the substrate concentration, the conversion of phthalic anhydride could reached 99%, and the selectivity to phthalide was 89%.The catalyst stability was tested in the scale-up experiments in 1 L autoclave under the optimum conditions.5 circulatory experiments was respectively carried on in γ-butyrolactone and dioxane solvent under the conditions of 10 g40%Ni2%La/Al2O3 catalyst,100 g phthalic anhydride,160℃,4.0 MPa. The higher activity was observed in the dioxane solvent, meanwhile both of the conversion of phthalic anhydride and the selectivity to phthalide could reach more than 98%; and the 40%Ni2%La/Al2O3 catalyst exhibited excellent stability in 5 circulatory experiments, since the conversion of phthalic anhydride was not lower than 95%, as well as the the selectivity to phthalide was not lower than 96%.Finally, considering the industrial production cost, the solvent recovery was performed and 70% of dioxane solvent was recoveried, the purity was over 99% by GC analysis. Meanwhile, crystallization purification of crude phthalide were performed under the solvent of acetone. After crystallization purification, the yield of phthalide with 99% of purity was also more than 88%.In this paper, we have provided a high activity, high selectivity, and high stability nickel-based catalyst for the preparation of high value-added phthalide, as well as developed a mild reaction conditions, environmental friendly phthalide synthesis method, which has a good industrial application prospect.