Evaluation of Adsorption Process in a Molecular Sieve for Anhydrous Ethanol Production Using Facilities of Aspen Adsim

Abstract

Anhydrous ethanol has several applications in industrial segments, besides being used as an additive to gasoline. Due to the formation of the azeotrope between ethanol and water, complex separation processes must be used to obtain anhydrous ethanol, such as extractive distillation, azeotropic distillation or molecular sieve adsorption. Among these processes, molecular sieve adsorption has the advantage of not requiring the addition of a solvent, which can enable a very high degree of purity for the product and avoids a solvent recovery step. This type of adsorption process can be performed using a hydrophilic adsorbent with pore diameter capable of selectively adsorbing water molecules and not ethanol molecules. Through dynamic process simulations, profiles of mole fractions of ethanol and water in the bed, the variation of the product composition with time and sensitivity analyses were evaluated. The adsorption phenomenon, the molecular sieves mechanism and the use of software for the simulation of chemical processes were demonstrated. The simulations reached very satisfactory results for the process. The base case simulation reached 91.3 % mass purity for the complete simulation of the batch process lasting 5000 s. Limiting the simulation to 2337 s, the mass purity was 99.3 %, while the recovery was 100.0 % and the productivity was 3.40 L/h/kg of adsorbent. This purity achieved meets the criteria for the use of ethanol as a gasoline additive. Column diameter and feed flow rate were the variables that most impacted the results in the sensitivity study.