Catalytic Preparation Of Fatty Acid Methyl Esters In Fixed Bed Reactor

Fatty acid methyl esters (FAMEs) are widely used in bioenergy source, reaction intermediates, surfactants, and so on. Using anion exchange resin as catalyst, fatty acid methyl esters can be prepared in a fixed bed reactor. In this article we have done a lot of research works on this field.The content of triolein in rapeseed oil is 38.73%. When the rapeseed oil is totally transesterified with methanol, the content of methyl linolenate, methyl linoleate, methyl oleate is 16.47%, 20.00% and 58.43%, respectively. The total contents of three methyl esters come to 94.89%.We put the resin into the fixed bed reactor (1.62 cm×73.8 cm) and use solid anion exchange resin as catalyst. Then the rapeseed oil can be transesterified. The rapeseed oil and methanol were fed separately with two pumps. In this way we can avoid adding auxiliary solvent and instable flow rate by mechanical stirring. We have examined the steady state in the reactor. The results were as follows: when the ratio of methanol to oil was low and the flow rate was high, the steady state could be established quickly. However, when the feed volume of rapeseed oil came to 60～80 mL, the reactor could always reach steady state.The conditions which affect the reaction include temperature, residence time, the ratio of methanol to oil. The results were as follows: the optimum temperature was 60℃, which was the maximum temperature of the resin. With the ratio of methanol to oil from 3.23 to 8.21, the conversion and the yield increased with the ratio. With the residence time from 5 to 55 minutes, the conversion and the yield increased linearly with time, which indicated that the residence time should be lengthened. We used twice and three times transesterification, or connected the outlet of fixed bed with inlet of circulation pump to lengthen the residence time, and we could get betterconversion and yield even though the ratio was low. We also analyzed the purity of the side-product, glycerol. The purity of glycerol was 98.17% and the glycerol in the product could be separated through centrifugation.The preparation of fatty acid methyl esters by esterification of free fatty acid with methanol was conducted as well. In this process we used solid cation exchange resin as catalyst to treat deodorizer distillates. The catalyst has good activity and stability under the temperature of 85℃. With esterification of the deodorizer distillates by three times in the fixed bed, the conversion was 99.59% using methanol amount only 90% of the deodorizer distillates. At 60℃, with twice esterification, the methanol amount used was four times of deodorizer distillates.