Molecular Simulation of Biobutanol Recovery Using LTA and CHA Zeolite Nanosheets with an External Surface

LTA and CHA zeolites with silica and silico-alumino-phosphate (SAPO) composition have been recently proposed by Van der Perre et al. (ChemSusChem2017,10, 2968) to recover butanol from a mixture of butanol, ethanol, acetone, and water. Such a mixture is obtained from biomass fermentation, which is a sustainable alternative for butanol production. Here, we establish a computational methodology to simulate the three-step process, consisting of selective adsorption of butanol, with some ethanol and water, from the initial mixture, using a silica LTA nanosheet; desorption of the adsorbed mixture by increasing the temperature; and adsorption of the desorbed products in a CHA (silica or SAPO) nanosheet. A combination of Monte Carlo simulations, allowing to reproduce or predict single- or multiple-component gas adsorption isotherms, and molecular dynamics, giving the time evolution of the selective adsorption and desorption processes, have been used to model the experimental setup. A recently parameterized force field of general use for zeolites, AlPOs, and SAPOs has been tuned up in order to describe all interactions arising from this model, allowing to capture the thermodynamics of the system, the flexibility of the frameworks, and the effects of surface and bulk in the permeability of the nanosheets.