Iranian Journal of Chemical Engineering (IJChE)

Abstract In this paper, we report the reaction of isoamyl alcohol and 1-chloro-4-nitrobenzene was carried out in a batch reactor under aqueous-organic biphasic conditions using the techniques like phase transfer catalysis and ultrasound irradiation. Tetrabutylammonium bromide (TBAB) was employed as the phase transfer catalyst. The reaction is greatly enhanced by adding a small quantity of phase-transfer catalyst under ultrasound (28 kHz, 300W). Detailed kinetics of the etherification was investigated. The rate constants were determined by varying the concentration of the catalyst, stirring speed, the concentration of alcohols, temperature, different solvents, concentration of sodium hydroxide, different inorganic salts and different phase transfer catalysts. From the detailed kinetic study, the optimum reaction conditions to produce higher yield of 1-(isopentyloxy)-4-nitrobenzene was obtained. The experimental data were well described by the pseudo-first-order equation. The individual experiment was carried without ultrasound; the obtained kapp value is 0.0094 min-1. The combination of ultrasound and stirring; the kapp value is 0.0178 min-1. From the observed results, the kapp value for ultrasonically promoted reaction is almost two fold higher than the normal reaction.

Abstract The ultrasound-assisted (UA) soybean oil methanolysis using KOH as a catalyst was studied at different reaction conditions in a microreactor. Box–Behnken experimental design, with three variables, was performed and the effects of three reaction variables i.e. reaction temperature, catalyst concentration and the methanol-to-oil molar ratio on fatty acid methyl ester (FAME) yield were evaluated by method of analysis of variance (ANOVA) and multiple regression. A quadratic polynomial model was obtained to predict the methyl ester yield. A yield of 97.1% for methyl ester was obtained at the deduced optimal conditions: reaction temperature of 47 °C, KOH catalyst concentration of 1.29% (w/w) and methanol-to-oil molar ratio of 6:1. Validation experiments confirmed the validity of the predicted model. At the optimal operation condition for the ultrasonic process, a higher yield of methyl esters was obtained in comparison with that of the non-ultrasonic layout. The results show that UA transesterification in microreactor minimizes the reaction time and temperature, alcohol-to-oil molar ratio as well as energy consumption.

Abstract The major active component in licorice is glycyrrhizic acid which is very useful in the pharmaceutical industry. In the present work, the extraction of glycyrrhizic acid in licorice is carried out in a stirred reactor as well as under indirect sonication in an ultrasonic bath. Batch extraction is carried out in a glass reactor of 150 mL capacity equipped with a six bladed glass turbine for agitation. Ultrasound assisted extraction has been carried out in a dual frequency ultrasound cleaning bath. The glycyrrhizic acid is analyzed using HPLC. Various process parameters such as solvent concentration, power, frequency of ultrasound, extraction temperature and solvent to solute ratio, which affect the extraction yield are optimized for both techniques. In ultrasound assisted extraction with final optimized conditions, i.e. 50% ethanol as solvent, 230 W power, 40:1 solvent to solute ratio, 30∫C temperature and 40 kHz frequency, 95.69% extraction is obtained in 20 minutes, whereas in extraction using stirred reactor only 68% extraction is observed in 60 minutes. Kinetic of the extraction process is studied and volumetric mass transfer coefficients as well as theoretical yield for different process parameters are estimated.