Production of biodiesel by a two-step supercritical reaction process with swing-adsorption refining

C.R. VERA; SILVANA A. D'IPPOLITO; CARLOS L PIECK; JOSÉ M. PARERA

Río de Janeiro

Congreso; ENPROMER 2nd Congress on Chemical Engineering, 4th Mercosur Congress on Process; 2005

A new catalyst-free, effluent-free process for the production of biodiesel is disclosed. The reaction of transesterification of triglycerides is carried out under supercritical conditions, i.e. at temperatures higher than the critical temperature of methanol. Raw materials for the reaction are methanol and triglycerides with any amount of free fatty acids thus enabling the production of biodiesel from cheap feedstocks such as beef tallow or high acidity yellow grease. The reaction proceeds without the aid of alkaline or acid catalysts, thus eliminating the need for neutralization steps downstream the reactor. In order to minimize the heat consumption and pumping power which are usually very high in the one-reactor configuration of all reported supercritical processes, two medium-pressure successive reactors with intermediate glycerol removal are used and a heat recovery scheme composed of heat exchangers and adiabatic flash drums is proposed. Process conditions and equipment design parameters are determined on the basis of the minimization of the heat duty and energy requirements. For the final removal of free glycerol, an alternative approach is presented which differs from the classical washing-distillation and washing-ultracentrifugation operations. Glycerol is cyclically retained in adsorption beds, desorbed in a thermal-swing step and recycled to the first reactor. Design parameters are obtained both from experimental data and estimation. No process water effluents are produced with this approach. The whole system is essentially ?dry? and only small water amounts are produced by esterification of the free fatty acids in the feed. Glycerol purification is simplified by the absence of catalyst and low water content.