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Free keywords:
Reactive chromatography; SMB; nonisothermal; heat of reaction; heat of adsorption
Abstract:
Reaction and separation can be integrated into a single unit operation in several ways. Selective adsorbents can be used in non-steady state fixed bed reactors to enhance the conversion of reversible reactions through separation of products, which diminishes the undesired backward reactions. This is the main idea of chromatographic reactors that are currently intensively investigated considering various liquid feed stocks (e.g. alcohol/acid mixtures or esters in water) [1,2]. In most of the studies reported up to now, the processes have been considered to proceed under isothermal conditions. Only recently, more attention was paid to the aspect that, in such periodically operated reactors, significant temperature effects can occur [3]. Reliable prediction of the performance of chromatographic reactors also at large scale requires that thermal effects due to adsorption, reaction, and also mixing are properly accounted for.
In the present work, thermal effects in reactive chromatography are investigated both theoretically and experimentally. The limiting case of simultaneous chemical and phase equilibrium is discussed in the framework of the equilibrium theory. Behaviour of single column and simulated moving bed chromatographic reactors is analysed with numerical simulations.
Esterifications of acetic acid with methanol and ethanol to produce methyl acetate and ethyl acetate were used as model reactions. Amberlyst 15 and Finex CS16G ion-exchange resins were chosen as the stationary phases. Adsorption enthalpies were determined from chromatographic data at various temperatures. Reactor experiments were carried out in thermally insulated (adiabatic) columns, fitted with several thermocouples. The self-amplifying nature of thermal waves in the reactor is due to nearly equal propagation velocities of the reaction front and the thermal wave. Experiments under isothermal conditions were carried out as a reference.
References:
1. Mazzotti, M., Kruglov, A., Neri, B., Gelosa, D., Morbidelli, M., Chem. Eng. Sci., 51(1996), 1827-1836
2. Vu Dinh, T., Seidel-Morgenstern, A., Grüner, S., Kienle, A., Ind. Eng. Chem. Res. 44(2005), 9565 - 9574
3. Sainio, T., Doctoral dissertation, Acta Universitatis Lappeenrantaensis 218, 2005
