(372c) Reactive Distillation for Synthesis of Ethyl Levulinate From Biobased Resources

In order for USA to reduce its dependence on foreign oil, it is necessary to produce liquid transportation fuels from lignocellulose biomass.  Levulinic acid can be synthesized from waste lignocellulosic biomass by a thermo-chemical route.  Levulinic acid can be converted into its ethyl and butyl esters by reaction with the corresponding alcohol, ethanol or butanol.  Ethyl levulinate and butyl levulinate have been identified as promising diesel fuel blending agents arising from their high oxygen content.  When burned in diesel engines, they give rise to very low soot and NOx emissions.  Ethyl levulinate is also used for synthesis of levulinic ketals by reaction with glycerol; these ketals are used as green plasticizers and cleaning solvents.

Esterification of levulinic acid is an equilibrium limited chemical reaction.  In order to improve conversion over the conventional batch reactor followed by distillation, the versatile process intensification technique reactive distillation, where simultaneous chemical reaction and distillation take place in a single piece of equipment, is used for levulinic acid esterification.

In this paper, we present results of recent experimental studies at the Michigan State University Reactive Distillation Facility to synthesize ethyl levulinate from the heterogeneous ion exchange resin catalyzed reaction of levulinic acid with ethanol.  In developing the process concept, we have studied the batch kinetics and equilibrium for esterification of levulinic acid with ethanol using homogeneous and heterogeneous catalysts.  A pseudo-homogeneous model has been used to represent the batch kinetic data using MATLAB.  Vapor-liquid equilibrium studies for important binary mixtures has been experimentally generated and co-related using the NRTL-HOC model. 

Continuous reactive distillation experiments were conducted in the MSU reactive distillation facility.  The catalytic zone of the reactive distillation column is packed with Katapak-S filled with Amberlyst-15; the column was run at atmospheric pressure.  High conversion of levulinic acid (~98%) was observed.  A process concept has been developed that allows ethyl levulinate containing less than 0.1% of lactones which form as side products.

Experimental studies are complemented by process analysis using Aspen Plus simulation software.  By implementing the kinetic model and phase equilibrium data generated in our laboratories, we are able to accurately model pilot-scale column behavior and simulate commercial-scale facilities.