Catalytic ethanolysis of soybean oil with immobilized lipase from Candida antarctica and 1H NMR and GC quantification of the ethyl esters (biodiesel) produced

Abstract

The catalytic ethanolysis of soybean oil with commercial immobilized lipase type B from Candida antarctica to yield ethyl esters (biodiesel) has been investigated. Transesterification was monitored with respect to the following parameters: quantity of biocatalyst, reaction time, amount of water added and turnover of lipase. The highest yields of biodiesel (87% by 1H NMR; 82.9% by GC) were obtained after a reaction time of 24h at 32°C in the presence of lipase equivalent to 5.0% (w/w) of the amount of soybean oil present. The production of ethyl esters by enzymatic ethanolysis was not influenced by the addition of water up to 4.0% (v/v) of the alcohol indicating that it is possible to use hydrated ethanol in the production of biodiesel catalyzed by lipase. The immobilized enzyme showed high stability under moderate reaction conditions and retained its activity after five production cycles. The 1H NMR methodology elaborated for the quantification of biodiesel in unpurified reaction mixtures showed good correlations between the signal areas of peaks associated with the α-methylene groups of the ethyl esters and those of the triacylglycerides in residual soybean oil. Monoacylglycerides, diacylglycerides and triglycerides could also be detected and quantified in the crude biodiesel using 1H NMR spectroscopic and GC-FID chromatographic methods. The biodiesel production by enzymatic catalysis was promising. In this case, was produced a low concentration of glycerol (0.74%) and easily removed by water extraction.