Hydrotropes affect a several-fold increase of the solubility of sparingly soluble solutes under normal conditions. Their water-solubility can significantly enhance the solubility of organic solutes such as esters, alcohols, aldehydes, ketones, hydrocarbons, and fats. While the study of hydrotropes is pioneered by a biochemist, greater appreciation of their role and applicability has happened rather in chemistry and chemical engineering than in biology. Hydrotropes are widely used in drug solubilization, as extraction agents for fragrances, as agents to increase the rate of heterogeneous reactions, and for separation of close-boiling liquid mixtures through extractive distillation and liquid-liquid extraction. Applications of hydrotropy and its mechanism are discussed and the scope for future work is presented in this review.

In the present study, Calcium oxide (CaO) obtained from eggshells has been used as a heterogeneous catalyst for biodiesel production from highly viscous non-edible rubber seed oil (RSO). Characterization of synthesized catalyst was done with the help of scanning electron microscope equipped with Energy dispersive spectrometry (SEM-EDS), X-ray diffraction (XRD) and Fourier transform Infrared spectroscopy (FTIR). Response surface methodology (RSM) with central composite design (CCD) was used to optimize the process parameters and 1H-NMR (Nuclear Magnetic Resonance) spectroscopy analysis was performed to find the conversion of RSO to biodiesel. A conversion of 99.7% of RSO to biodiesel was obtained at 12:1 methanol to oil molar ratio, 4 (wt%) of catalyst, and 3 hour reaction time with a quadratic regression model of R2 of value 0.9566 was obtained. The composition of prepared biodiesel is estimated with the help of Gas Chromatogram-Mass Spectroscopy (GC-MS) analysis. Artificial Neural Network (ANN) with Levenberg-Marquardt algorithm was also trained to predict biodiesel conversion and the value of R2 obtained was 0.9976. It was observed that predicted conversion values from ANN were better when compared to prediction using RSM.

Biodiesel production by transesterification of rubber seed oil (RSO) using calcium oxide (CaO) derived from calcined limestone as a heterogeneous catalyst is presented in this study. Optimization of process parameters affecting the conversion of RSO to biodiesel is done by design of experiments (DOE) and an effective comparison of two different optimization methods, namely, response surface methodology (RSM) and artificial neural networks (ANN) is presented. A high conversion of 95.2% was obtained at 12:1 methanol: Oil molar ratio, 4 (wt%) catalyst and 5 hr of reaction time. The proposed design model of RSM is found to fit well with the predicted conversion and with molar ratio and reaction time as the significant process parameters affecting the conversion. Best validation performance of 8.8991 occurred at epoch 4 with a mean square error (MSE) of 1.55 in ANN model trained with Levenberg-Marquardt algorithm. By comparing the predicted coefficient of determination, R 2 , values of 0.8452 obtained by using RSM, and 0.9939 obtained by using ANN for biodiesel conversion, it is concluded that ANN model is the best model for predicting the percentage conversion of RSO to biodiesel with minimum error between experimental and predicted values. K E Y W O R D S artificial neural networks, biodiesel, limestone, optimization, response surface methodology, transesterification

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In the recent times, biodiesel production from various non-edible oil sources has received a lot of attention. Karanja oil is chosen mainly due to its availability and low cost. It is a nitrogen fixing tree cultivated to enhance soil quality. Transesterification of Karanja oil to biodiesel using a basic solid modified heterogeneous catalyst has been discussed in the present study. Aluminum nitrate Al(NO 3 ) 3 impregnated on calcined marble (Al(NO 3 ) 3 /calcined marble), prepared by wet impregnation method (25%), is used as a modified heterogeneous base catalyst. Surface morphology of the synthesized catalyst is determined using a scanning electron microscope (SEM) analyzer and the composition of various elements present in the prepared catalyst is analyzed using energy dispersive spectrometer (EDS analyzer). 67.56 (wt/wt) of calcium oxide (CaO) is observed for calcined marble and 78.19 (wt/wt %) of CaO has been noticed for impregnated catalyst (Al(NO 3 ) 3 /calcined marble). A maximum biodiesel yield of 96.5% and a conversion of 97.43% was obtained at an optimum methanol:oil molar ratio of 9:1 (mol/mol), 4 (wt %) of catalyst concentration and 1.5 (h) reaction time respectively. The entire composition of formed biodiesel is determined using gas chromatography-mass spectrometry (GC-MS) analyzer and conversion of Karanja oil to biodiesel is measured using 1 H-nuclear magnetic resonance (NMR) analyzer.

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Statistical analysis for esterification of high viscous rubber seed oil (RSO) (feed stock) with a high free fatty acids (FFA) content was presented in this work. Initially a high acid value of 67.6 mg KOH/g oil was observed from raw RSO analysis, which is not in a favorable range. After complete esterification reaction, a reasonable acid value of 3.55 mg KOH/g oil was detected at reaction conditions of 15:1 methanol: oil molar ratio (mol/mol), 3 vol% of catalyst concentration, and 2 hr of reaction time. Statistical analysis of factors affecting the final value is performed using response surface methodology. From the statistical analysis, a significant second-order quadratic model with a p value <0.0001 was observed. It is also noticed that molar ratio and reaction time are the most significant factors affecting the final product (esterified oil). The coefficient of determination, R 2 of value, 0.9672 indicates that there exists a minimum error between predicted and experimental acid values observed.

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