Biodiesel production via esterification/transesterification reactions can be catalyzed by homogenous or heterogeneous catalysts. Development of heterogeneous catalysts for biodiesel production is highly advantageous due to the ease of product purification and of catalyst recyclability. In this current work, a novel acidic [DABCODBS][CF3SO3]2 dicationic ionic liquid (DIL) was used as heterogeneous catalyst to produce biodiesel using oleic acid as model oil. The esterification was conducted under ultrasonic irradiation (20 kHz) using a 14 mm ultrasonic horn transducer operated at various duty cycles. It was observed that the duty cycle, amplitude, methanol to oil molar ratio, catalyst amount and reaction temperature were the major factors that greatly impact the necessary reaction time to lead to a high yield of biodiesel. The reaction conditions were optimized with the aid of Response Surface Methodology (RSM) designed according to the Quadratic model of the Box Behnken method. The optimum conditions were found to be at catalyst amount of 0.64 mol%, methanol to oil ratio of 14.3:1, temperature of 59 °C, reaction time of 83 min and amplitude of 60% in continuous mode. The results showed that the oleic acid was successfully converted into esters with conversion value of 93.20% together with significant reduction of reaction time from 7 h (using mechanical stirring) to 83 min (using ultrasonication). The results also showed that the acidic DIL catalyst we designed purposely was efficient to catalyze the ultrasonic-assisted esterification yielding high conversion of oleic acid to methyl oleate on short times. The DIL was also recycled and reused for at least five times without significant reduction in performance. Overall, the procedureoffersadvantages including short reaction time, good yield, operational simplicity and environmentally benign characteristics.

Hydrodesulfurization (HDS) has been commercially employed for the production of ultra-low sulfur fuel oil. However, HDS is unable to remove sterically hindered sulfur-containing compounds such as dibenzothiophene (DBT) and benzothiophene (BT). An alternative way to remove sulfur is via extractive desulfurization system (EDS) using deep eutectic solvents (DES) as sustainable extractant. In this work, liquid polymer DES was synthesized using tetrabutylammonium chloride (TBAC) and poly(ethylene glycol) 400 (PEG) with different molar ratios. Response surface methodology (RSM) was applied to study the effect of independent variables toward extraction efficiency (EE). Three significant operating parameters, temperature (25–70 °C), DES molar ratio (1–3), and DES volume ratio (0.2–2.0), were varied to study the EE of sulfur from model oil. A quadratic model was selected based on the fit summary test, revealing that the extraction efficiency was greatly influenced by the amount of DES used, followed by the extraction temperature and PEG ratio. Although molar ratio of DES was less sensitive towards EDS performance, the EE was much higher at lower PEG ratio. For the realization of an energy-efficient EDS system, optimization of EDS parameters and EE was carried out via a desirability tool. At 25 °C, 1:1 molar ratio of TBAC to PEG, and DES-to-model-oil-volume ratio of 1, removal of DBT reached as high as 79.01%. The present findings could provide valuable insight into the development of practicable EDS technology as a substitute to previous HDS process.

This study describes the potential conversion of dried microalgae. Chlorella vulgaris (C. vulgaris) into fatty acid methyl ester (FAME) using the direct transesterification (DT) method and using ionic liquids (ILs) as a catalyst. In this work, the performance of monocationic IL, namely 1-butyl-1-methylpyrrolidinium bromide (IL 1), and dicationic IL, namely 1,4-bis(1-methylpyrrolidinium-1-yl) butane dibromide (IL 2), as catalysts was compared for DT of C. vulgaris under microwave irradiation. The results revealed that IL 2 showed a better performance in catalyzing the DT reaction by producing 87.9 mg/g% of FAME, while the use of IL 1 led to 74.3 mg/g% of FAME under optimum conditions. The kinetic study for direct transesterification of C. vulgaris showed that the reaction followed a first order kinetic reaction where the activation energies were calculated to be 22.2499 kJ mol⁻¹ and 22.0413 kJ mol⁻¹ for IL 1 and IL 2, respectively.