Continuous Selective Hydrogenation Of Itaconic Acid To Methylsuccnic Acid Over Silica-supported Nickel Catalyst

Itaconic acid is a kind of ?,?-unsaturated carbonyl compounds,under normal circumstances C-C double bond is more reactive than the C=O bond for hydrogenation,but the phenomenon of competitive adsorption of H2 should not be ignore.As a result,there are some difference in hydrogenation process between ?,?-unsaturated carbonyl compounds and single C=C bond or C=O bond.We choose nickel catalyst.Because it is one of the most active and selective catalyst for reducing the C=C double bond.In this paper,we have investigated the effect of nickel content,support,temperature,pressure,solvents and other factors on conversion and selectivity,under non-additives conditions.A serial of silica-supported nickel samples were prepared by incipient impregnation method with different Ni contents and were used in continuous selective hydrogenation of itaconic acid to methylsuccnic acid.Based on the experimental results of activity evaluation,nitrogen adsorption-desorption,transmission electron microscopy(TEM),X-ray diffraction(XRD),temperature-programmed reduction(TPR)and temperature-programmed desorption of adsorbed H2(H2-TPD),the catalytic performances and the physic-chemical properties of the prepared catalysts with different Ni contents were investigated.The results show that,the catalysts activity was increased significantly with the increasing Ni content in the context of 5-20wt%,whereas the methylsuccinic acid selectivity increased rapidly initially but almost reached a plateau when the Ni content is more than 10wt%.Under the reaction conditions of 343K and 3 MPa,the itaconic acid conversion ratio of 80.6%,selectivity to methylsuccinic acid of 88.1%can be achieved respectively.The excellent performance of Ni/Si02 catalysts in continuous catalytic hydrogenation of itaconic acid may be attributed to large surface area,large pore volume,and average pore diameter.