Selective Water Removal by Sorption from Butanol–Water Vapor Mixtures: Analyses of Key Operating Parameters and Site Energy Distribution

Abstract

In the present paper, selective water removal from butanol–water vapor mixture was carried out in a pressure swing adsorption (PSA) system using canola meal (CM) biosorbent. Five operating parameters (temperature, pressure, feed butanol concentration, feed flow rate, and CM particle size) were studied by the orthogonal array design method and range analysis to obtain the favorable process conditions for butanol drying. The performance of butanol dehydration was evaluated using five indices: water uptake, butanol uptake, water selectivity, butanol recovery, and maximum butanol concentration in the effluent. The obtained favorable dehydration conditions resulted in the maximum effluent butanol concentration of >99 v/v %, water uptake of 0.48 g/g-ads, water separation factor of 5.4, and butanol recovery of 90%. The Dubinin–Polanyi model for large pores fit the water adsorption isotherms reasonably well. Furthermore, site energy distribution of water adsorption was also estimated. Average site energy (3.33 kJ/mol) and standard deviation of the site energy distribution (2.36 kJ/mol) were determined and applied to analyze the interaction between the biosorbent and adsorbate, and adsorbent surface energy heterogeneity. Saturated CM was regenerated at 110 °C under vacuum and reused for more than 16 cycles.