Siti Kholijah Abdul Mudalip

Effects of Ultrasonic Waves on Vapor-Liquid Equilibrium of an Azeotropic Mixture

Abstract Azeotropic and extractive distillation techniques used to separate azeotropic mixtures are among the most challenging separation processes in the chemical industry. In this work, an innovative distillation technique which employed ultrasonic waves was proposed to intensify the conventional multi-column azeotropic distillation method into a single-column alternative. The effects of ultrasonic intensity on the vapor-liquid equilibrium (VLE) of methyl-tert-butyl-ether (MTBE)-methanol was investigated at 50, 100, 200, and 250 W/A·cm2 and at a fixed frequency of 40 kHz. Studies were also done to examine the effects of ultrasonic frequency on the VLE data at 25 and 68 kHz frequencies. It was found that ultrasonic waves at 50 W/A·cm2 intensity and 25 kHz frequency gave the highest relative volatility (α) at 2.654 and completely eliminated the MTBE-methanol azeotrope, thereby allowing highly pure MTBE to be recovered in just a single distillation column. The results revealed that ultrasonic waves had the potential to favorably manipulate α, and hence, the VLE of an azeotropic mixture.

Structures and hydrogen bonding recognition of mefenamic acid form I crystals in mefenamic acid/ethanol solution

Mefenamic acid is one of the active pharmaceutical ingredients that exhibit polymorphism. An experimental study has found that Form I of mefenamic acid is produced from cooling crystallization with ethanol as a solvent. Hydrogen bonding is considered as the fundamental factor that controls the polymorphism of mefenamic acid in ethanol. This work, in essence, was performed to verify this using molecular dynamics simulation.The simulation was performed using COMPASS force field available in Material Studio package.The result of the simulation showed strong hydrogen bonding between oxygen and hydrogen in the carboxylic group. The results of the Fourier transform infrared spectroscopy analysis confirmed the existence of O-H, C-O and C=O bonds. These findings proved the presence of hydrogen bonds that leads to the formation of hydrogen motif in Form I of mefenamic acid during crystallization process using ethanol as a solvent.