Catalytic Performance Of Phosphorous Modified Ni/Al₂O₃ Catalyst For Hydrogenation Of Maleic Anhydride

Succinic anhydride (SA) is an important raw material in the chemical industry, which is widely used in the manufacturing of surface-active agents, food additives, pharmaceuticals and agrochemicals. Currently, SA is produced by two main processes:hydrogenation of MA process and dehydration of succinic acid process. Hydrogenation of MA has attracted increasing attention because of the simple process, lowering cost and environmental protection.Maleic anhydride (MA) consists of two C=O bonds, one C=C bond and one C-O-C group. The product of the MA hydrogenation is rather complex and different type of reactions can occur, depending on the catalyst and reaction conditions. In the first step, the hydrogenation of C=C bond in MA produces SA. Then, the hydrogenolysis of one C=O bond in SA gives GBL. Finally, THF and BDO can be obtained by GBL hydrogenolysis. C3 and C4 compounds, such as n-propanol, n-butanol, propionic acid and butyric acid can also be produced. Thus, it is difficult to produce SA from the selective hydrogenation of MA. So far noble-based catalysts, such as Rh, Pd, Ru, copper-based catalysts and nickel-based catalysts have been used to catalyze MA hydrogenation to SA. The catalytic performance of single metal catalysts is further improved by introducing the second component commonly. The adding of phosphorous can improve the catalytic performance by adjusting the electronic configuration of active metal Ni, the dispersion of active components and the interaction between active components and supports.Up to now, P-modified catalysts used in the reaction of MA hydrogenation is scarcely studied.Based on our previous research, the P-modified catalysts were characterized by N2 physisorption, XRD, FT-IR, H2-TPR, H2-TPD, CO-TPSR, TG-DTA and applied in the MA hydrogenation. The main contents and conclusions are as follows:1. A series of 15Ni/xP-Al2O3 catalysts with different phosphorous contents were prepared by incipient wetness impregnation and applied in the the hydrogenation of maleic anhydride. The results showed that on one hand, the introduction of phosphorous species can improve the catalytic ability of adsorption and activation of hydrogen during the reaction by increase the number of reducible Ni species on the surface of catalysts; on the other hand, the introduction of phosphorous species can adjust the electronic con-figuration of active metal Ni and weaken the catalytic ability to activate the C=O bond. Thus, the catalytic activity of MA hydrogenation and selectivity to SA were improved.2. The stability of 15Ni/Al2O3 and 15Ni/5P-Al2O3 catalyst in the reaction of MA hydrogenation were also studied. The introduction of phosphorous species reduced the amount of coking on the surface of catalysts. Then the stability of catalysts for hydrogenation of MA was highly improved. The high stability of phosphorous modified catalysts was ascribed that the introduced phosphorous species can weaken the catalytic ability to activate the C=O bond and decrease the ability of catalysts to adsorb the C=O bond.