Study On Liquid Phase Hydrogenation Of Maleic Anhydride Over Catalyst

Maleic anhydride as an important intermediate in organic synthesis, can be hydrogenated to yield a series of fine chemicals, such as succinic anhydride, y-butyrolactone and 1,4-butanediol. Among them succinic anhydride can produce many reactions for its unique structure. Specifically, succinic anhydride contains one oxygen atom and two acyls, thus the electrophilic effect and the interaction of acyls can enhance their electropositivity further promoting the chemical reactions, such as hydrolysis, alcoholysis, aminolysis and esterification, which leads to an extensive commercial prospective of succinic anhydride. The three main ways to yield succinic anhydride include maleic anhydride hydrogenation, bio-fementation, and electrochemical reduction. The maleic anhydride hydrogenation method has many advantages, especially the product of high purity and the feasibility of commercial production. While currently the researches were focused on the hydrogenation of maleic anhydride to y-butyrolactone or 1,4-butanediol, but few to succinic anhydride. So the relative researches, particularly on the hydrogenation catalyst, are necessary.This paper systematically studied the influences of the Pd catalyst preparation and the reaction conditions on the conversion of maleic anhydride as well as the selectivity of succinic anhydride, by using a series of analytic methods, such as XRD, TEM, XPS and TG-DTA. The main works are as follows:1. The catalysts with the different supports, such as TiO2, AI2O3 and SiO2, were studied. It was found that the Pd/TiO2 catalyst produced the highest hydrogenation activity which results in the 59.3% conversion because it has better dispersion, smaller particle size and more active sites than those of the catalysts with other supports, though its special surface is comparatively small.2. The influences of calcination on catalyst active components were also studied when the precursor is Pd(NO3)2. It was found that the catalysts after calcination had large active components in size leading to a low catalyst hydrogenation activity and thus a decrease of about 10% of the maleic anhydride conversion. Besides, with the increase of reduction temperatures from 150 to 450?, the interaction between active component and supports became stronger, causing a decrease of the hydrogenation activity of catalyst. The conversion of maleic anhydride reached 87.9% when the reduction temperature is 150? whereas the conversion was only 38.9% when reduction temperature is 450?. The supports after impregnation, drying and reduction with 150? had the highest hydrogenation activity producing the conversion of 87.9%.3. The conversion of maleic anhydride increased from 59.4% to 100% with the reaction temperature rising from 100 to 200?, and maintained at 100% after the temperature reaching 250?. But it should be noted that at the temperature of 250? some byproducts y-butyrolactone produced. The partial pressure of hydrogen and reaction time made a little difference on the conversion of maleic anhydride. The best reaction condition in this article was 150?-2 MPa H2-1h. In addition, it was found that the presence of water inhibited the hydrogenation of maleic anhydride.