Hydrogenation Of ?-pinene Over Ru Nanocatalysts Stabled By PEG

Pinane is widely applied in the synthetize of terpenes and other industrial products.It is usually synthetized by hydrogenation of a-pinene.Research shows that Ru nanocatalysts has a good catalytic activity in the hydrogenation of pinene,but its stability and recycling are two big problems.Therefore,improving its stability and solving the problem of difficult recycling are of great significance for the research of hydrogenation of a-pinene.In this paper,Ru nanocatalysts and Ru/Ni bimetallic nanocatalysts stabled by polyethylene glycol(PEG)were synthesized.The liquid/liquid separation system was formed with the organic solvent of toluene/n-heptane.The system was applied to the hydrogenation of a-pinene.The liquid/liquid two-phase system could be used to recover the catalysts by simply regulating the temperature of the system.It provided a simple and feasible way for the difficult recovery of the homogeneous catalysts in the hydrogenation of a-pinene.The main results are as follows:With different molecular weights of PEG(600,4000,6000)as stabilizer,Ru nanoparticles were synthetized by H2reduction.The average particle size of the catalyst were between 1.0-2.3nm.Comparing its catalytic performance for the hydrogenation of a-pinene,it was concluded that the catalytic activity of Ru(II)nanoparticles stabilized by PEG6000 was better.The Ru(II)nanocatalysts was applied to the hydrogenation of a-pinene.The effects of reaction temperature,hydrogen pressure,reaction time and the molar ratio of substrate/Ru on the reaction were investigated.Under optimal reaction conditions,the conversion of a-pinene reached98.9%,and the selectivity of cis-pinane was 96.7%.After 5 circulations,the conversion rate of a-pinene remained at more than98.0%.This showed that PEG was a good stabilizer.Ni and Ru/Ni bimetallic metal catalysts stabled by PEG6000 were synthesized,and their diameters were 5.9nm and4.7nm respectively.This two kinds of catalyst were used in hydrogenation of pinene,and the Optimal Ru/Ni molar ratio was 3:2 in preparation for Ru/Ni nanocatalys.The recycling of Ru/Ni bimetallic catalysts was investigated.After 3 circulations,the catalytic activity did not change obviously.The conversion of a-pinene and the selectivity of cis-pinane were all above 95.0%.Under the same conditions,the catalytic activity of the hydrogenation of a-pinene was compared.The experimental results were as follows:Ru nanocatalysts>Ru/Ni bimetallic nanocatalysts>Ru/C(5%)>Pt/C(0.5%)>Pt/C(5%)>Ni nanocatalysts.