Research Of Nickel Catalysts For Oil Hydrogenation

Stearic acid is an important chemical raw material, has a high application in cosmetics,medicine, surfactant and other fields. As the most important method in the production ofstearic acid, oil hydrogenation can reduce its degree of unsaturation, improve its quality andexpand the scope of its use. Hydrogenation catalyst plays a key role in the process ofhydrogenation reaction and how to prepare a highly active hydrogenation catalyst is the keytechnology of this field. The topic is aiming at preparing supported nickel hydrogenationcatalyst with high active and low cost, simplifying catalyst preparation process, andimproving its catalytic activity to international level in order to replace importedhydrogenation catalyst.At first, taking coconut shell activated carbon as carrier. Ni-Co binary catalyst has beenprepared with coprecipitation method. The effect of surface area、pore volume、pore sizedistribution and HNO3modification on catalytic activity have been studied in depth, so do asthe optimal preparation condition of HNO3modification. The results show that, activatedcarbon with a relatively large pore volume and surface area, and suitable pore structuredistribution is suitable for hydrogenation catalyst carrier. The HNO3modification has aneffect on surface area and pore structure. Under the optimal modification conditions:5mol/LHNO3, reacting6h under60℃, catalyst has a good catalytic activity, which is better thancatalyst with unmodified carrier. Furthermore, the optimal preparation condition ofcoprecipitation method has been explore systematically, and the structure of catalyst has alsobeen analyzed by combing BET、TEM、XRD and TG. Under the optimal conditions: nickelnitrate is0.5mol/L, pH is about8, Ni loading is35%,350℃calcination for2h,400℃reducing for2h, mass ratio of Ni and Co is600:1, iodine value can be decreased from38to1.The right proportion of Co additives can also improve the catalytic activity.Three kinds of preparation method: coprecipitation method, ammonia evaporationmethod, and homogeneous precipitation under reduced pressure, are researched forhydrogenation activity. The results indicate that homogeneous precipitation under reducedpressure has the higher catalytic activity than coprecipitation method, ammonia evaporationmethod is worst. Compared with coprecipitation method, homogeneous precipitation underreduced pressure has a simpler preparation method, less impurity adsorption and goodrepeatability. TEM and XRD analyses indicate that its active component disperses evenly, andNi crystal size is small, and has no reunion. The optimal conditions of homogeneousprecipitation under reduced pressure are as follows: the aging time is3h, the concentration ofnickel ammonia complex is0.2mol/L, and pH is about10.Taking palm oil hydrogenation as evaluating reaction and homogeneous precipitationunder reduced pressure as preparation method, the influence of process conditions of oilhydrogenation reaction on the property of catalyst has been researched. The optimalconditions are as follows, the reaction temperature is230℃, reaction pressure is2MPa,reaction time is4h, and catalyst concentration is about0.5‰. Iodine value of oil can reduceto about0.5, can meet the industrial requirements. At last, the paper has studied the recycling and reuse of industrial waste catalyst. Metalcomponent with Ni, Co and the carrier of waste catalyst can be recycled with the wet process.Ni and Co metal components can be loaded on recycled carrier directly to prepareregeneration hydrogenation catalyst without separation. The regeneration catalyst’s activity issame as fresh catalyst, and its dosage is only0.3‰.