• Energy Research

AbstractThis study provides a new emphasis for research on the valorization of biowastes into nanocatalyst and biorefineries to be integrated with petroleum bioupgrading and polluted water treatment. The response surface optimized batch transesterification of waste‐frying oil using methanol and sustainable animal bone valorized fluorapatite nanocatalyst (FAP) yielded approximately 97% biodiesel via a pseudo‐second‐order reaction with an efficient rate of 0.48 (mol L−1)−1min−1 and activation energy of 13.11 kJ mol−1. In a pioneering step, by‐products of the starch industry and the biodiesel transesterification process; corn‐steep liquor (CSL 0.2 g L−1) and bioglycerol (6.24 g L−1) as nitrogen and carbon sources, increased the dibenzothiophene biodesulfurization (BDS) efficiency of a novel biodesulfurizing Rhodococcus jialingiae strain HN3 (NCBI Gene Bank Accession No. MN173539) sixfold. Further, upon the application of such bioproducts in a batch BDS process (1/3 petro‐diesel/water) of 96 h; HN3 desulfurized 82.26% of 0.62 wt.% sulfur without affecting the petro‐diesel calorific value. In an attempt to reach zero waste, an auxiliary pioneering step was performed, where the spent waste FAP, after being efficiently used for four successive transesterification cycles, was applied to photo‐remediate 4‐nitrophenol polluted water under UV‐irradiation. Advantageously, the fresh and spent waste FAP recorded the same photodegradation capabilities. Where they obeyed the Langmuir–Hinshelwood kinetic model (R2 ≥ 0.966) recording the same rate constants (kapp 0.032 min−1) and were efficiently reused for four successive polluted‐water treatment cycles. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Conventional biodiesel manufacturing uses alcohol as an acyl acceptor, resulting in glycerol as a side product. The increased demand for biodiesel has led to the production of a substantial surplus of glycerol, exceeding the market need. Consequently, glycerol is now being regarded as a byproduct, and in some cases, even as waste. The present study aims to suggest an economically viable and ecologically friendly approach for maintaining the viability of the biodiesel sector. This involves generating an alternative byproduct of higher value, rather than glycerol. Triacetin is produced through the interesterification of triglycerides with methyl acetate, and is a beneficial ingredient to biodiesel, reducing the need for extensive product separation. The primary objective of this research is to improve the interesterification reaction by optimising process parameters to maximise biodiesel production while using sulphuric acid as an economically viable catalyst. The study utilised the Box–Behnken design (BBD) to investigate the influence of various process variables on biodiesel yield, such as reaction time, methyl acetate to oil molar ratio, and catalyst concentration. An optimisation study using Response Surface Methodology (RSM) focused on key process reaction parameters, including the methyl acetate to oil (MA:O) molar ratio, catalyst concentration, and residence time. The best conditions produced a biodiesel blend with a 142% yield at a 12:1 MA:O molar ratio, with 0.1 wt% of catalyst loading within 1.7 h. The established technique is deemed to be undeniably effective, resulting in an efficient biodiesel production process.

In this study, a response surface methodology (RSM) using a central composite design (CCD) was implemented to investigate the influence of process variables on ethyl levulinate (EL) production from the ethanolysis of waste corn cob samples, using sulphuric acid as a catalyst. The effects of four independent variables, namely, the temperature (A), the corn cob content (B), corn cob/H2SO4 mass ratio (C) and the reaction time (D) on the yields of EL (Y1), diethyl ether (DEE) (Y2) and solid residue (Y3) were explored. Using multiple regression analysis, the experimental results were fitted to quadratic polynomial models. The predicted yields based on the fitted models were well within the experimental uncertainties. Optimum conditions for maximising the EL yield were found to be 176 °C, 14.6 wt. %, 21:1 and 6.75 h for A to D, respectively. A moderate-to-high EL yield (29.2%) from corn cob was achieved in optimised conditions, a result comparable to those obtained from model C6 carbohydrate compounds. Side products were also produced, including diethyl ether, furfural, levulinic acid, 5-hydroxymethyl furfural, ethyl acetate, ethyl formate and water. Total unknown losses of only 5.69% were reported after material balancing. The results suggest that lignocellulosic waste such as corn cob can be used as a potential feedstock for the production of ethyl levulinate by direct acid-catalysed ethanolysis, but that the treatment of side products will need to be considered.

Biodiesel production using supercritical methanol in the absence of catalyst has been analysed by studying the main factors affecting biodiesel yield. A quadratic polynomial model has been developed using Response Surface Methodology (RSM). Box-Behnken Design (BBD) has been used to evaluate the influence of four independent variables i.e. methanol to oil (M:O) molar ratio, temperature, pressure and time on biodiesel yield. The optimum biodiesel yield is 91% at M:O molar ratio, temperature, pressure and reaction time of 37:1, 253.5oC, 198.5 bar and 14.8 minutes, respectively. Overall reaction kinetics has been studied at optimum conditions concluding a pseudo first order reaction with reaction rate constant of 0.0006 s-1. Moreover, thermodynamics of the reaction has been analysed in the temperature range between 240 and 280oC concluding frequency factor and activation energy of 4.05 s-1 and 50.5 kJ/mol, respectively. A kinetic reactor has been simulated on HYSYS using the obtained kinetic data resulting in 91.7% conversion of triglycerides (TG) with 0.2% relative error from the experimental results.

In this study, a simple and robust derivatisation-free method has been developed using a gas chromatograph (GC), which has been validated as a suitable analysis for free fatty acids (FFAs) of waste cooking oil (WCO). As biodiesel synthesis from high acid value WCO involves pre-treatment steps, a non-catalytic approach has been employed for biodiesel production. This work has focused on the esterification of FFAs of high acidity feedstock for fatty acid methyl esters (FAME) production. The effect of four independent controllable factors, i.e. methanol to oil (M:O) molar ratio, temperature, pressure and time on FFAs conversion has been investigated. Response Surface Methodology (RSM) via Central Composite Design (CCD) has been implemented for designing experimental runs and optimising the process variables for maximum FFAs conversion. Four quadratic regression models have been developed representing an empirical relationship between reaction variables and responses. The adequacy of the predicted models has been checked by numerous statistical validation techniques including analysis of variance (ANOVA) at 95% confidence level. The developed optimum conditions have been reported at 25:1, 256 °C, 110 bar and 16.6 min for M:O molar ratio, temperature, pressure and time, respectively. The predicted optimal conditions have been validated experimentally with 0.22% relative error.

Biodiesel production using supercritical methanolysis has received immense interest over the last few years. It has the ability to convert high acid value feedstock into biodiesel using a single-pot reaction. However, the energy intensive process is the main disadvantage of supercritical biodiesel process. Herein, a conceptual design for the integration of supercritical biodiesel process with organic Rankine cycle (ORC) is presented to recover residual hot streams and to generate electric power. This article provides energy and techno-economic comparative study for three developed scenarios as follows: original process with no energy integration (Scenario 1), energy integrated process (Scenario 2) and advanced energy integrated process with ORC (Scenario 3). The developed integrated biodiesel process with ORC resulted in electric power generation that has not only satisfied the process electric requirement but also provided excess power of 257 kW for 8,000 tonnes/annum biodiesel plant. The techno-economic comparative analysis resulted in favouring the third scenario with 36% increase in the process profitability than the second scenario. Sensitivity analysis has shown that biodiesel price variation has significant effect on the process profitability. In summary, integrating supercritical biodiesel production process with ORC appears to be a promising approach for enhancing the process techno-economic profitability and viability.

In this study, valorisation of high acid value waste cooking oil into biodiesel has been investigated. Non-catalytic transesterification using supercritical methanol has been used for biodiesel production. Four controllable independent process variables have been considered for analysis including methanol to oil (M:O) molar ratio, temperature, pressure and time. Uncommon effects of process variables on the reaction responses, e.g. biodiesel and glycerol yields, have been observed and extensively discussed. Response surface methodology (RSM) via Central Composite Design (CCD) has been used to analyse the effect of the process variables and their interactions on the reaction responses. A quadratic model for each response has been developed representing the interrelationships between process variables and responses. Analysis of Variance (ANOVA) has been used to verify the significance effect of each process variable and their interactions on reaction responses. Optimal reaction conditions have been predicted using RSM for 98% and 2.05% of biodiesel and glycerol yields, respectively at 25:1 M:O molar ratio, 265oC temperature, 110 bar pressure and 20 minutes reaction time. The predicted optimal conditions have been validated experimentally resulting in 98.82% biodiesel yield, representing 0.83% relative error. The quality of the produced biodiesel showed excellent agreement with the European biodiesel standard (EN14214).

Biodiesel has been established as a promising alternative fuel to petroleum diesel. This study offers a promising energy conversion platform to valorise high acidity waste cooking oil (WCO) into biodiesel in a single-step reaction via supercritical methanol. Carbon dioxide (CO2) has been used as a co-solvent in the reaction with a catalytic effect to enhance the production of biodiesel. This work provides an in-depth assessment of the yield of four fatty acids methyl esters (FAME) from their correspondent triglycerides and fatty acids. The effects of four independent process variables, i.e., methanol to oil (M:O) molar ratio, temperature, pressure, and time, have been investigated using Response Surface Methodology (RSM). Four quadratic models have been developed between process variables and the yield of FAMEs. The statistical validation of the predicted models has been performed using analysis of variance (ANOVA). Numerical optimisation has been employed to predict the optimal conditions for biodiesel production. The predicted optimal conditions are at 25:1 M:O molar ratio, 254.7 °C, 110 bar within 17 min resulting in 99.2%, 99.3%, 99.13%, and 99.05% of methyl-oleate, methyl-palmitate, methyl-linoleate, and methyl-stearate yields, respectively. The predicted optimum conditions have been validated experimentally.