Selective Hydrogenation Of Tetrahydrofarnesylacetone To The Corresponding Saturated Ketone Over Palladium Supported Catalyst

6,10,14-trimethyl-2-pentadecanone (Hexahydrofarnesylacetone, PA) isan important intermediate for synthesis vitamin E. The methods used forproduction of hexahydrofarnesylacetone are well-documented reactions inthe industry field, however, all these synthetic routes reported contain thesame hydrogenation process of6,10,14-trimethyl-13-ene-2-pentadecanone(terahydrofarnesylacetone, FA-4H) to get PA. So it is important to developa green and efficient synthesis process for the selective hydrogenation ofFA-4H to the corresponding saturated ketone.Terahydrofarnesylacetone is a kind of unsaturated ketone. Undernormal circumstances, the hydrogenation of the C=C bond to yieldsaturated ketones (PA) is thermodynamically favoured, however, the resultindicates that selectivity for PA of100%with completely conversion ofFA-4H is still very difficult. In a word, there are some differences inhydrogenation process between terahydrofarnesylacetone and single C=Cbond or C=O bond, and it is particularly important to control the reaction selectivity.Palladium is intrinsicallly a well catalyst for selective hydrogenation ofthe C=C bond of FA-4H for its narrow radial expansion of d band; thelarger the band, the stronger the four-electron repulsive interactions withthe C=C bond and the lower the probability of its adsorption. In this paper,the liquid-phase reduction of FA-4H to the corresponding saturated ketonewas investigated on palladium-supported catalysts, under solvent-freecondition, and Pd/C catalyst exhibited a high hydrogenation effciencycompared to activities reported in the literature. On this basis, we had abrief discussion on Pd/SiO2catalyst, and focused on the best performancecatalyst—Pd/C. The effects of reation parameters such as palladiumloading, Pd particle size, granularity and pretreatment of support andreaction temperature on synthesis of PA in presence of Pd/C catalyst werestudied. And the best conditions were obtained as following: Pd loading0.5wt%~3.0wt%, small Pd particle, small granularity of support,pretreatment of active carbon with aqueous ammonia solution of10%ornitric acid of10%, low reaction temperature. Under the selected reactionconditions, the selectivity towards hexahydrofarnesylacetone (PA) wasalmost up to100%when FA-4H was completely converted.