(503f) Intensified Reaction-Separation Schemes

Evangelia Koumaditi, John Woodley, Rafiqul Gani Department of Chemical and Biochemical Engineering, Technical University of Denmark, DK-2800 Lyngby, Denmark

The environmental and economic concerns are driving the chemical and biochemical industries to develop new, sustainable methods of production. Combining the reaction and the separation process in one unit, not only can it lead to cost and energy reductions for the overall process, but it can also have an effect on the reaction, in terms of yield. Motivated by the need to take advantage of the intensified process units, a method needs to be developed, which will allow the systematic generation and analysis of reactive separation configurations at an early stage in process synthesis. The objective of this work is the development of a method to design reaction-separation schemes, based on analysis of phase equilibrium of the involved chemical system.

Oxidation reactions are used as a generic system to highlight the conceptual basis of the design method. The selective oxidation of primary alcohols are examples of this generic system, which are used as case studies for the application of the design method. The properties of the pure components and the characteristics of phase equilibrium (azeotropes and liquid phase split) have been considered to identify new and novel intensified reaction-separation schemes. Also, the selective oxidation of alcohols to aldehydes is a challenging reaction, as aldehydes are relatively unstable products and also due to their use in the production of high-value products. Even though the reactions are considered to be bio-catalyzed by the enzyme Galactose Oxidase, the design method nevertheless is applicable to other similar systems and also not restricted to the use of biocatalysts only.

The specific examples highlighted in this work cover ternary systems involving alcohol + water + aldehyde, from which aldehyde is the product to be recovered, while alcohol and water are recycled back to the reactor. The first step of the method is the definition of the reaction system and data collection. The designs of the intensified separation schemes are based on the properties of pure components, as well as the properties of the mixture of the involved chemical system. The properties of pure components that are of interest are namely, the boiling point, the vapor pressure and the water solubility. After the pure component analysis is completed, the vapor-liquid and liquid-liquid equilibria are examined for each binary subsystem of the ternary mixture, employing available data or generated through model-based phase equilibrium predictions. The next step involves the classification of the systems according to their characteristics. The reaction-separation schemes are then determined by using phase equilibrium relations that favor the removal of the product from the reacting phase. Calculations of single-stage equilibrium based separations are performed in order to obtain the mass balance and the distribution of the compounds in the different phases. The last step involves validation tests to confirm the feasibility of the suggested configuration, by super-imposing the calculated mass balance lines on the predicted VLE and LLE plots. Success of the designed intensified reaction-separation scheme depends on the amount of the targeted compound removed from the reactor. Note that the separation and recovery of the product requires the use of solvents. Ionic liquids, because of their special properties have been considered as the needed solvents.

The presentation will highlight the results of the intensified reaction-separation schemes for a class of oxidation of primary alcohol reactions. Details of the design method together with the important concepts will also be highlighted.