Research Of Preparation, Characterization And Activity Of The Catalysts For Oil Hydrogenation

Oil Hydrogenation is an reaction in which hydrogen gas is added to unsaturated double bonds using metals like reductive nickel as catalyst.Oil hydrogenation with extremely saturated level will obtain highly saturated products, from which fine chemicals of high-carbon saturated fatty acids(like stearic acid) can be prepared by subsequently processing of hydrolysis.These chemicals are extensively used in fast consuming field such as surfactants, cosmetics, medicine and so on.An imperative condition for oil hydrogenation to produce extremely hydrogenated oil is catalyst, which must behave with high activity and whose selectivity is not necessary to be considered.Consequently, how to achieve a highly active catalyst is a key technology in this area.In this thesis, a silica gel support named Si-g was firstly synthesized by chemical precipitation using sodium silicate as silicium source. On the basis of Si-g, either a nickel or nickel-lanthanum supported catalyst was then prepared adopting a deposition-precipitation method.The catalysts were characterized by XRD, SEM, TEM and N2 adsorption-desorption experiments, whose results useful for structural analysis were showed as following.Both two supported catalysts preserved support's amorphous structure, with bigger particle size, smaller average pore diameter, but higher specific surface area than their supports.The active constituents of supported nickel catalyst named Ni/Si-g were Ni and NiO, which were highly dispersed in Si-g support. However, active species of supported nickel-lanthanum catalyst named NiLax/Si-g were mainly Ni,La, and NiO,La2O3 in the second place.Doping lanthanum could accelerate formation of Ni metal phase and restrain particle aggregation, which resulted in better dispersion and smaller particle size of Ni. However, lanthanum doping did not change pore structure remarkably.The effects of various factors in catalyst preparation on hydrogenation activity were systematically investigated, using soybean oil hydrogenation as model reaction, and the process conditions had been determined. (1)Ni/Si-g catalyst on which the actual capacity of nickel was16.1wt%, had been prepared in optimized conditions.The process parameters of oil hydrogenation using Ni/Si-g as catalyst were obtained as follows:the dosage of catalyst was 0.10%, the reaction temperature was 200℃, the reaction pressure was 1.OMPa, and the reaction time was 60min, oil's iodine value was decreased from 130.0 to 5.5, the hydrogenation conversion calculated was 95.8%.(2) NiLa0.2/Si-g catalyst on which the capacity of nickel loaded was 20wt% and the molar ratio of nickel and lanthanum was 1:0.2, had been prepared in optimized conditions.The process parameters of oil hydrogenation using NiLao.2/Si-g as catalyst were determined as follows:the dosage of catalyst was 0.05%, the reaction pressure was 1.4MPa, the reaction temperature was 200℃, and the reaction time was 60min, oil's iodine value was decreased from 130.0 to 1.7, the hydrogenation conversion calculated was 98.7%. Hydrogenation activity could be greatly improved by introducing lanthanum of suitable proportion into nickel catalyst.