(151a) Process Intensification In Synthesis Of Methyl Acetate

Processes which combine chemical reaction and product separation in one step are of rising interest in the chemical industry as well as petrochemical and pharmaceutical industry. These reactive systems are so called hybrid processes. Main application of hybrid processes is reactive distillation, a combination of reversible reactions and product separation by distillation. Applicability of reactive distillation is limited to mixtures with different boiling point of substances. Yield of conversion can be increased by evaporating the product from the reaction broth.

Comparable advantages are expected from combination of chemical reaction with several unit operations such as liquid/liquid-extraction. Provided that a solvent can be found which dissolves the product selectively the result of extractive separation of products from reaction mixtures is comparable with distillative product separation except that chemical reaction with extraction can even be operated at ambient temperature. As a consequence lower cost of energy and less complexity of control systems is expected. In this project synthesis of methyl acetate with heterogeneous catalysts has been investigated and modeled. Synthesis was investigated in batch operation and in continuous operation in a plug flow reactor. In both processes esterification was catalyzed with a cation exchange resin Liquid/liquid extraction was carried out with the solvent dodecane. With an appropriate surplus of acetic acid in the feed the formation of the methyl acetate ?methanol aceotrop can be avoided because of complete methanol consumption (conversion). Separation of methylacetate from the reaction broth is only affected by the stoichiometric water content. Water/acetic acid-separation by distillation and therefore recovery of the acid surplus does not need a sophisticated rectification set up. The process can be operated without loss of catalyst activity for a very long time (in lab scale it was actually not possible to quantify loss of catalyst activity because it did not obtain a detectable level). By combining esterification with liquid/liquid-extraction the methyl acetate ? water aceotrop can be overcome by splitting the product mixture into two separate product fluxes for distillative separation, the binary system acetic acid ? water left in the raffinate phase and the binary system methyl acetate ? solvent formed in the extract phase.