In the present work, high speed homogenizer has been used for the intensification of biodiesel synthesis from soybean oil and waste cooking oil (WCO) used as a sustainable feedstock. High acid value waste cooking oil (27mg of KOH/g of oil) was first esterified with methanol using sulphuric acid as catalyst in two stages to bring the acid value to desired value of 1.5mg of KOH/g of oil. Transesterification of soybean oil (directly due to lower acid value) and esterified waste cooking oil was performed in the presence of heterogeneous catalyst (CaO) for the production of biodiesel. Various experiments were performed for understanding the effect of operating parameters viz. molar ratio, catalyst loading, reaction temperature and speed of rotation of the homogenizer. For soybean oil, the maximum biodiesel yield as 84% was obtained with catalyst loading of 3wt% and molar ratio of oil to methanol of 1:10 at 50°C with 12,000rpm as the speed of rotation in 30min. Similarly biodiesel yield of 88% was obtained from waste cooking oil under identical operating conditions except for the catalyst loading which was 1wt%. Significant increase in the rate of biodiesel production with yields from soybean oil as 84% (in 30min) and from WCO as 88% (30min) was established due to the use of high speed homogenizer as compared to the conventional stirring method (requiring 2-3h for obtaining similar biodiesel yield). The observed intensification was attributed to the turbulence caused at microscale and generation of fine emulsions due to the cavitational effects. Overall it can be concluded from this study that high speed homogenizer can be used as an alternate cavitating device to efficiently produce biodiesel in the presence of heterogeneous catalysts.
The present work deals with the optimization of interesterification of karanja oil using response surface methodology (RSM) analysis with intensification studies based on the use of ultrasound. Esterification of karanja oil was performed as a pretreatment under fixed optimum conditions of molar ratio of 1:10, catalyst loading of 3.5% and temperature of 60 °C to reduce the acid value from initial of 10.5 mg of KOH/g to 1.8 mg of KOH/g. The pretreated oil was used for interesterification where the process parameters considered for optimization were time (X1), catalyst loading (X2), reactant ratio (X3) and duty cycle (X4), each varied at three levels. The maximum yield of FAME achieved using optimum parameters as time of 35 min, catalyst loading of 1 wt%, reactant ratio of 1:9 (mol:mol) and duty cycle of 60% was 91.56% (on the basis of theoretical ester formation). The effect of reaction temperature was also studied keeping other parameters constant at optimum conditions and it was observed that yield increases continuously with an increase in the temperature over the entire range of temperature. It was also demonstrated that ultrasound assisted interesterification approach gives less requirement of methyl acetate and catalyst as compared to the conventional approach. It was also observed that higher yield was obtained in the presence of ultrasound (91%) as compared to the conventional approach (60%). Kinetic studies established that second order rate equation fits the obtained data well. A mathematical model in RSM was also successfully developed which can be used to make predictions about the expected conversion. Overall the work demonstrated the intensification benefits of using ultrasound and established the optimum conditions for maximum benefits using RSM analysis.
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