Catalytic Hydrogenation Synthesis Of Helional By Pd/C

Helional?2-methy-3-?3,4-methylenedioxyphenyl?propanal?is a synthetic floral fragrances,which can be used for the preparation of a varietyofcosmetics.Theselectivehydrogenationof2-piperonylidenepropanal?3-?1,3-Benzodioxol-5-yl?-2-methyl-2-propenal?could give helional.At present,the catalyst used in the reaction is high loading Pd/C catalyst in domestic,which existed the problem of high cost.This paper aimed to prepare the catalyst with low cost,high performance,good stability and selectivity in the above hydrogenation reaction.In the experiment of selective hydrogenation synthesis of helional,1%Pd loading Pd/C catalyst modified by 3%K₂CO₃ exhibited excellent stability and selectivity.The optimal conditions for selective hydrogenation reaction determined by experiments are:4 g2-piperonylidenepropanal as raw material,200 mL ethyl acetate as solvent,0.2 g 1%Pd/C catalyst,150?,0.5 MPa,4 hours and the stirring speed of 1000r/min.The reaction under these conditions have a stable results with the yield in 94-96%.And based on above experiments,stability evaluation is also carried out and catalyst through simple processing can be used 20 times or so.The differences between the untreated catalyst and catalyst treated with K₂CO₃ is examined by scanning electron microscopy?SEM?and BET.The catalyst modified by K₂CO₃ has a smaller surface area,pore size,pore volume,and bore diameter than those of untreated catalyst.So it was speculated that catalyst treated with K₂CO₃ delayed the rate of side effects,and thus improved the reaction selectivity and yield.