Oxygenated compounds like acetals, esters and ketals are often produced by a reversible liquid phase reaction catalyzed by acids, where water is formed as subproduct. By means of chromatographic reactors, as the Simulated Moving Bed Reactor (SMBR), it is possible to integrate reaction and products separation into a single unit, displacing the equilibrium towards the products formation by removing at least one of them from the reaction medium. In addition to complete reactants conversion, operational and equipment costs are reduced. Usually, strongly acidic ion exchange resins, such as Amberlyst 15wet, are used both as catalyst as a selective adsorbent for water. However, water is strongly adsorbed and a large consumption of desorbent is needed in order to achieve high product purity and high productivity. Since the stationary phase and equipment costs are small with respect to the solvent recycle cost [1], it is desirable to choose an appropriate stationary phase for an SMBR that will provide the maximum productivity value but for a low desorbent consumption.

The aim of this work is to present the influence of the stationary phase on the SMBR performance by using mixtures of Amberlyst 15wet (a catalyst and selective adsorbent for water) with Smopex 101 fibres (catalyst), for the case of 1,1-dimethoxyethane production [2, 3]. By means of a complete model accounting for the different particularities of both catalyst and adsorbent (external mass-transfer resistance followed by reaction at the surface of Smopex 101 fibres; external and internal mass-transfer resistances for Amberlyst 15wet using a bi-LDF approach and adsorption and reaction at both particle and pores surface) the performance of the SMBR is studied. The concepts of reactive-separation region (γ2-γ3 plot) and regeneration region (γ1-γ4 plot) [4] are used to analyze the effect of the stationary phase composition in the productivity and desorbent consumption, respectively.

References:

[1] G. Ströhlein, Y. Assunção, N. Dube, A. Bardow, M. Mazzotti, M. Morbidelli, Chem. Eng. Sci., 61 (16), 5296-5306 (2006).

[2] C. Pereira, P. Gomes, G. Gandi, V. Silva, A. Rodrigues, Ind. Eng. Chem. Res. (ie070889t) (2008).

[3] G. Gandi, V. Silva, A. Rodrigues, Chem. Eng. Sci., 62 (7), 907-918 (2007).

[4] P. Sá Gomes, M. Minceva, A.E. Rodrigues, Adsorption, 12, 375-392 (2006).