Fatty acid esterification by reactive distillation: Part 2—kinetics-based design for sulphated zirconia catalysts

Abstract

In a previous study on the basis of reaction equilibrium, it was demonstrated that the synthesis of fatty acids esters of heavy alcohols by catalytic reactive distillation (RD) is basically feasible. Presently, the analysis is expanded to the kinetics-based design applied to the synthesis of 2-ethylhexyl dodecanoate. Experimental data for a super-acidic sulphated zirconia catalyst are employed. It is shown that this catalyst is highly selective even for the high alcohol/acid ratios as prevail in a RD column. To avoid catalyst deactivation, liquid–liquid segregation into an organic and an aqueous phase must be prevented, and operating temperatures beyond 373 K must be chosen. A kinetic model based on liquid activities is proposed, with parameters determined from both kinetic and equilibrium measurements. A typical column design has 13 reactive stages with a catalyst loading of 170 kg m −3 , temperature profile of 400– 440 K , and a space velocity of 0.022 kmol kg cat −1 h −1 for 99.9% purity product ester. A modified Damköhler number is proposed.