Study On The Preparation Of α-tocopherol Via Heterogeneous Catalytic Reaction

Tocopherol is the most effective and necessary antioxidant in the body ofhuman and animals. It can effectively block the free radical chain reaction, with theeffect of promoting breeding, anti-aging, anti-tumor and preventing cardiovasculardisease. α-tocopherol is biologically the most active naturally occurring form oftocopherols, but its content is very low in natural tocopherols. Industrially, the methodof hydroxymethylation is usually adopted to realize conversion of non-α-tocopherol toα-tocopherol.Traditional hydroxymethyl process which uses homogeneous liquid acid ascatalyst has many disadvantages, such as corrosion of the equipment, separationdifficulties of the catalyst, large amount of acid catalyst and environmental pollutionby the waste acid, etc. It is not suitable for today’s cleaner production trend on theprinciple of green chemistry. Therefore, it is a genuine desire to develop solid acidcatalyst to substitute liquid acid in the traditional acid catalyzed reaction.In this paper, sulfonic acid modified MCM-41was firstly used asheterogeneous catalyst in the converting reaction of non-α-tocopherol to α-tocopheroland α-tocopherol product was prepared.Sulfonic acid modified MCM-41catalyst was prepared by the post synthesismethod. The characterized results of TEM, BET, XRD, FT-IR, TG-DTG indicated thatsulfonic acid modified MCM-41catalysts had maintained good mesoporous structure;the pores arrangement was in an orderly manner; the surface acidity reached8.3mmol/g; BET specific surface area was253m2/g, the average pore diameter was2.6nm with a narrow pore size distribution range; sulfonic acid groups had beensuccessfully grafted into the MCM-41mesoporous surface and fomed the solid acidcatalyst with strong acidity.Sulfonic acid modified MCM-41catalyst was applied in thehydroxymethylation-reduction reaction of non-α-tocopherol. The influences ofcatalyst amount, reaction time, reaction temperature to the selectivity and yield wasstudied and the optimal reaction conditions were obtained: natural tocopherol rawmaterials5.0g, paraformaldehyde amount2.5g, catalyst amount12%of the raw material, reaction time4h, reaction temperature180°C, Pd/C catalyst amount1.49g.At these conditions, the yield of α-tocopherol product was47%, the proportion ofα-tocopherol in the product was94%. Finally,13C nuclear magnetic resonancespectroscopy of α-tocopherol product indicated that the chemical shift value of threechiral carbon atoms had not changed.