Experimental and computer simulation of a molecular distillation process for the dehydration of tetramethylammonium hydroxide solution

Abstract

Tetramethylammonium hydroxide pentahydrate (TMAH·5H2O) is easily decomposed when heated, which results in the difficulty of dehydration. In this study, a new process for dehydration of a TMAH propylene glycol solution using wiped-film molecular distillation was developed. The experiments were carried out to evaluate the effect of operating conditions on the performance of the dehydration with the operating temperature ranging from 65 °C to 90 °C, the operating pressure from 100 Pa to 2000 Pa and the mass flow rate from 36 to 162 g/min. The experimental results indicated that molecular distillation was capable of dehydrating TMAH solution to a water content of 0.65% from 5.82%. Then a modified Flash module in Aspen plus, which used the fitting factor and linear correlation between the simulated and experimental temperatures, was developed to simulate the dehydration process. The relative error between the modified simulated and experimental data is less than 5%, and the response surface methodology analysis was conducted to optimize the operating conditions. The optimal dehydration conditions were 85 °C, 100 Pa and 54 g/min feed flow rate, where the minimum water content in distilled solution is 0.43%. The results show that the process developed realizes a high efficiency of dehydration and prevents TMAH from thermal decomposition.