Study On Hydrogenation Of Maleic Anhydride On Palldium Catalysts

With the development of the world economy and industrialization,the damage to the environment is getting worse and worse.It is necessary to promote economic development on the basis of environmental protection in the future.As a green industrial process,catalytic hydrogenation is gaining increasing attention.Succinic anhydride is an important fine chemical raw material and intermediate,which is widely used in polymer materials,medicines,agricultural chemicals,dyes and other fields.Compared with traditional maleic anhydride electrolytic reduction and succinic acid dehydration method,catalytic hydrogenation of maleic anhydride to succinic andydride is the most advantageous and green economy.Succinic anhydride is not only the hydrogenation product of maleic anhydride,but also the intermediate materials ofγ-butyrolactone,1,4-butanediol,etc..Improvement of the hydrogenation conversion efficiency and selectivity is the main problem to be solved in the production of succinic anhydride.Hydrogenation of maleic anhydride is an acid-base sensitive reaction.traditional acid catalyst is easy to induce deep hydrogenation of maleic anhydride,resulting in low selectivity of succinic anhydride;hydrogenation conversion efficiency is low on the basic catalyst.In this paper,we studied the effects of catalyst surface properties,metal size and metal-support interaction on the selective hydrogenation of C=C and C=O double bonds of maleic anhydride.As contrast,the acidic Pd/Al₂O₃,netutral Pd/BN and basic Pd/MgO catalysts are prepared and the three catalysts have similar Pd particle sizes.At room temperature,conversion of maleic anhydride is 25%,100%and 43%on Pd/Al₂O₃,Pd/BN,and Pd/MgO catalysts for 1 h,respectively.The yield of succinic anhydride can still reach 98%after four hydrogenation cycles on Pd/BN catalyst,and the succinic anhydride yield is close to 100%in the reaction temperature range of 25～150 ℃.The characterization results show that Pd/BN catalyst has the fastest rate of hydrogen dissociation and spillover,followed by Pd/MgO and Pd/Al₂O₃.In addition,acid Pd/Al₂O₃ catalyst and basic Pd/MgO catalyst adsorb the reactants molecules strongly and hydrogenation products are difficult to be desorbed,which result in the low product yield.Owing to the weak adsorption of the C=C bond of maleic anhydride on the neutral Pd/BN catalyst,succinic anhydride is easy to desorb from the surface of Pd/BN catalyst after fast hydrogenation of maleic anhydride.Therefore,the high hydrogenation efficiency and high selectivity of succinic anhydride are obtained on Pd/BN catalyst.Pd/BN is a new efficient catalyst for production of succinic anhydride by maleic anhydride hydrogenation.