| Succinic anhydride is an important industrial raw materials, which has been widely used in the pharmaceutical, pesticide, petroleum chemical industry. Its hydrolysis product succinic acid can be used to synthesize biodegradable plastics PBS with1,4-butanediol. With the tightening of white pollution problems, the biodegradable plastic PBS shows a very broad market prospect. It will greatly stimulate and promote market demand of its upstream product succinic anhydride. The succinic anhydride industry has caused great concern to the industry and academia. At present, there are three ways in the industrial application to produce the succinic anhydride, including electrochemical reduction, bio-fermentation and maleic anhydride hydrogenation. The hydrogenation of maleic anhydride method is the most competitive industrial technology because of its high purity of the product, simple of the process, lower costs and ease of mass production.The maleic anhydride molecule contains one C=C, two C=O bonds, and one C-O-C group. Hydrogenation of the C=C bond in maleic anhydride can synthesize succinic anhydride. Hydrogenation of the C=C and one C=O bond can obtain y-butyrolactone. Hydrogenation of the C=C and two C=O bond can reach to tetrahydrofuran. Because of C=C and two C=O bonds in maleic anhydride are conjugate to each other, the activation energy of C=C bond is closer to C=O bond, increasing the difficulty of selective hydrogenation of C=C bond. In the early reports, researchers payed more attention to the depth hydrogenation products, such as y-butyrolactone,1,4-butanediol, tetrahydrofuran, and butyric acids. Hydrogenation of maleic anhydride to succinic anhydried was scarcely studied, maily focused on our group. The hydrogenation of maleic anhydride to succinic anhydride research can not only give the guidance for preparing high-performance of directed synthesis succinic anhydride of catalysts, it can also provide guidance on selective hydrogenation of a,β-unsaturated carbonyl compounds.Based on our previous research, we prepared a series of Ni-Cu/Al2O3catalysts with different Cu contents by wetness impregnation in this thesis. The catalytic performance in the hydrogenation of maleic anhydride was studied. Also, the catalysts were characterized by N2physisorption, H2-TPR、H2-TPD-MS、CO-TPSR、XRD、TPO-MS、TG-DTA. The function of Cu and how the Cu influence the performance of the catalysts on hydrogenation of MA were systematically researched. The followings are our major results:The selectivity of SAH was improved by the Cu promotion. The introduced Cu effectively improved the activity for C=C bond hydrogenation and inhibited the hydrogenation of C=O bond. Both of the MA conversion and SA selectivity on15Ni-7Cu/Al2O3catalyst reached to100%under the reaction condition of5MPa hydrogen pressure and210℃for40min.The Cu took up the tetrahedron vacancies preferentially in the surface of Al2O3, and decreased the active cite which has interaction with C=O bond, and improved performance of catalysts on hydrogenation of C=C bond. Besides, the Cu species inhibited migration and accumulation of Ni, raised dispersion of Ni on support that led to high performance on hydrogenation of C=C bond.The Cu-introduced improved the stability of Ni-Cu/Al2O3catalysts. The high carbon low-polymer which formed for strong interaction between C=O bond and the surface of catalysts was the major reason that caused the deactivation of Ni/Al2O3catalysts. The Cu species decreased the active cite of Ni which had interaction with C=O bond, and decreased the production of the high carbon low-polymer. The Cu species inhibited loss of Ni simultaneously. The synergetic effect between above factors improved the stability of catalysts on hydrogenation of MA. |
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