Recovery Act - Energy Efficient Reactive Dehydration of Acetic Acid by Hybrid Reactive Distillation and Membrane Separation

Acetic acid is a large volume, global commodity chemical used as a basic building block in manufacturing polymers, anhydrides, and esters. Water is an inherent part of the manufacturing process. Dehydration of crude acetic acid consumes substantial energy, and adds to production costs. By 2010, total distillation energy consumption for dehydration of acetic acid will exceed 10 trillion BTU/year. In addition, this energy usage contributes to the cost of manufacture of acetic acid, impacting the global competitive position of U.S. producers. This proposal addresses the reduction of both energy consumption and manufacturing costs for acetic acid. The overall objective of the Phase I project is to substantially reduce the costs associated with the dehydration of acetic acid, which is currently performed by energy-intensive distillation. This goal is to be accomplished by the integration of two energy efficient separation technologies; reactive distillation and membrane separation. A novel reactant will be added to the crude acetic acid, which converts the water into a highly volatile product, by a reversible reaction over a solid catalyst in a reactive distillation column. This volatile product is readily removed from the acetic acid, at substantially reduced energy input. The volatile product is then regenerated off-line in a second small reactive distillation column, by reversing the reaction, producing water, which is removed from the system by energy efficient membranes. This application will extend the use of energy efficient membranes to the dehydration of chemically aggressive or corrosive materials, and small molecules otherwise difficult to separate from water. The program will demonstrate the technical and economic feasibility of the novel dehydration technology, through the evolution of new catalysts for the reaction, demonstration of the membrane separation of water, demonstration of the experimental performance of the total system, and process design, cost estimation, and life cycle cost assessments. This program will be conducted with subcontracts to the Department of Chemical Engineering at the University of Massachusetts, Amherst, and Compact Membrane Systems of Wilmington, Delaware. Commercial Applications and Other Benefits: This integrated dehydration system, based on energy efficient membranes and reactive distillation, should find immediate application to the commercial production of acetic acid. In addition, many industrial chemical are produced for which water must be removed, such as ethanol for fuels. In these cases, energy conservation is achieved because the high heat of vaporization of water is circumvented in distillation processes, leading to opportunities for a major reduction in the energy requirements for dehydration in the production of chemicals and fuels for the U.S. economy.