Novel Extraction Process Of Natural Tocopherols

Various aspects of the novel extraction process of natural tocopherols from deodorizer distillates of vegetable oils by methyl esterification of free fatty acids and specific adsorption on chemically modified adsorption resins have been studied.Methyl esterification of free fatty acids can be conducted either in a stirred tank batch process, or in a fixed bed continuous process.When a stirred tank batch process is used, the appropriate catalyst is sulphuric acid. Suitable operation conditions are as follows: sulphusic acid catalyst 1.0 wt% of deodorizer distillates, methanol 42 wt% of deodorizer distillates, temperature 70℃, time 2 h. By first esterification reaction, the acid value of deodorizer distillates can be reduced to less than 10 mgKOH/g from 130 mgKOH/g. By secondary esterification reaction, the acid value can be further reduced to less than 3 mgKOH/g. The recovery of tocopherols is more than 97% at every esterification reaction.When the fixed bed continuous process is used, the appropriate catalyst is strong acid cation exchange resin. The dynamic characteristics is studied in a fixed bed reactor of inner diameter 1.56 cm, resin packing height 96 cm. The effect of mass ratio of methanol to deodorizer distillates, temperature, residence time, and flow rate to conversion of free fatty acids has been studied. Suitable operation conditions are as follows: strong acid cation exchange resin as catalyst, flow rate 1.05 ml/cm2 min, temperature 60℃, methanol/deodorizer distillates 2.0 (by mass), residence time 2 h. By first esterification reaction, the acid value of deodorizer distillates can be reduced to 30-40 mgKOH/g from 145 mgKOH/g. By secondary esterification reaction, the acid value can be further reduced to less than 3 mgKOH/g. The recovery of tocopherols is more than 99.5% at every esterification reaction.By using anhydrous ethanol as solvent, the adsorption equilibrium and adsorption rate of tocopherols in methyl esterification products on modified adsorption resin No.2 have been determined by static method. The adsorption isotherms can becorrelated by Langmuir equation. The equation at 25℃ is thesaturated adsorption amount is 454.5 mg tocopherols/g dried resin. The equation at 35℃ is the saturated adsorption amount is 373.1 mg tocopherols/gdried resin. The adsorption capacity is quite large, therefore, it is suitable for adsorption separation of tocopherols. If the external diffusion resistance is negligible, the internal diffusion time constants (D/r2) are 0.5 x l0-3 min-1 (25℃) and 1.5 x l0-3 min-1 (35℃), respectively, as calculated by solid ball diffusion model.The adsorption breakthrough curves and desorption curves of tocopherols on modified adsorption resins No.l and No.2 are determined on an adsorption column of inner diameter 2.0 cm, resin packing height 29.6 cm. Anhydrous ethanol-benzene (5:1(V/V)) mixture as solvent, flow rate 0.57 ml/cm2 min, temperature 25℃, desorption agent 5% acetic acid-anhydrous ethanol-benzene. The breakthrough point of tocopherols on resin No.2 is later than on resin No.l. The highest tocopherols concentration of desorption curve on resin No.2 is higher than on resin No.l. This shows that the adsorption capacity and diffusion rate of tocopherols on resin No.2 are higher. The breakthrough curves of tocopherol homologues on resin No.2 are different as well, a-tocopherol breakthoughs and saturates firstly and has the lowest adsorption capacity; p+y-tocopherol breakthoughs and saturates later and has bigger adsorption capacity; 8-tocopherol breakthoughs and saturates ultimately and has the highest adsorption capacity.In the tocopherols extraction process of specific adsorption on adsorption resin, the resin should be used repeatedly. A complete cyle includes adsorption, purge 1, desorption, regeneration, purge 2. The load should be controlled that tocopherols do not flow out of the column by the end of purge 1. When the secondary methyl esterification products are used as raw materials of tocopherols, the load of tocopherols...