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The current study aims to develop a heterogeneous base catalyst from areca nut (Areca catechu L.) leaf ash incorporated with K2CO3. The composite heterogeneous catalyst was used to catalyze transesterification of a mixture of edible and inedible oils viz. soybean, jatropha and pongamia oil for biodiesel production. The characterization of the catalyst was done by Field emission scanning electron microscopy (FESEM), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), High resolution transmission electron microscopy (HRTEM), and Brunauer–Emmett–Teller (BET). The highest biodiesel yield of 96.57 ± 0.81 % was attained in 3.35 ± 0.15 h under optimal conditions of 9:1 molar ratio of methanol to oil (MRMO), 15 wt% catalyst concentration at 65 °C temperature. The reusability of the catalyst was successfully studied till 3rd cycle, resulting in 82.76 ± 0.80 % biodiesel yield. The feasibility of the resultant methyl esters was asserted by FT-IR, Carbon-13 nuclear magnetic resonance (13C NMR), Proton nuclear magnetic resonance (1H NMR), and Gas chromatography-Mass spectrometry (GC-MS) analyses. The developed catalyst can be considered an active catalyst, which is advantageous because of its cost-effectiveness and environmentally friendly nature.

Biodiesel is generally obtained by transesterification and esterification of appropriate feedstocks facilitated by a catalyst. It has emerged to be one of the most potential alternatives for the conventional fuels gaining worldwide attention. Heterogeneous catalysts are usually preferred than homogeneous for biodiesel synthesis due to facile separation and insignificant soap formation. However, the separation still possesses difficulty leading to mass transfer hindrance. Therefore, these catalysts can be further modified using magnetic separation techniques to develop magnetically separable catalysts. The magnetic nanoparticles (MNPs) are notable appealing catalysts due to huge surface area, high activity, amicable functional groups and structures, adaptable properties, conformity in pore size, and facile separation have made them desirable catalyst carriers for biodiesel synthesis. The MNPs are modified via functionalization to construct magnetically recoverable heterogeneous nanocatalysts. Magnetic catalysts can be utilized as a befitting option for biodiesel synthesis as these are environmentally benign, highly reusable and economically viable. The current review article discusses different magnetic solid catalysts such as magnetic base, acid, biocatalysts and bifunctional of acid base catalysts for efficient biodiesel synthesis. The prime focus of this paper rest on the catalytic performances of various magnetically recoverable catalysts, mechanisms and recyclability for biodiesel production processes. The synthesis methods of magnetic heterogeneous base and acid nanocatalysts, magnetic properties, functionalization and their reciprocity on the catalytic activity are reviewed in this article.

Energy consumption is increasing day by day, thereby depleting the fossil fuel reserve at an alarming rate. The fossil-based fuels have many adverse effects on the environment and cause global warming due to emission of greenhouse gases. Biodiesel produced via the transesterification process is an alternative, eco-friendly, and renewable fuel. Transesterification is carried out using homogeneous, enzyme, and heterogeneous catalysts. Heterogeneous catalysts can resolve the issues faced by the homogeneous and enzyme catalysts during biodiesel synthesis. At the same time, heterogeneous nanocatalysts have much more potential due to their higher surface area, more selectivity, and stronger catalytic activity. In this review, various nanocatalysts such as metal oxides (CaO, MgO, ZnO, Ti2O, CuO, and ZrO2), magnetic nanocatalyst, nano-zeolite catalyst, and nano-hydrotalcite catalysts were studied. In addition, catalyst preparation methods, physical properties of catalyst along with various reaction parameters such as reaction temperature and time, methanol to oil molar ratio (MTOMR), catalyst loading, and biodiesel yield were highlighted and discussed. In short, biodiesel synthesis using nanocatalyst can provide a cheap and clean energy and thus the nanocatalyst can be further developed as a strong candidate for the global energy industry in the future.

Biodiesel is a renewable alternative biofuel to conventional fossil fuel. Biodiesel can be produced through esterification and transesterification reactions mainly catalyzed by acid, alkali, and enzyme catalysts. Among all of these catalysts, enzyme catalysts are more advantageous than chemical catalysts (alkali and acid catalysts) due to their high selectivity, mild reaction conditions, lower energy consumption, and yielding of good quality of products with no side reactions. However, because of the high costs of enzymes, there is a limit on the use of enzymatic operation on an industrial scale. The cost of enzymes can be reduced by improving the lifespan of catalysts. Over the last few decades, significant developments in enzyme-based biodiesel synthesis have been attained both on the laboratory and industrial scale, and production costs are also reduced. This review gives an overview of immobilized lipase-catalyzed and lipase-inorganic hybrid nanoflowers catalyzed biodiesel production, including the economic viability of enzyme catalysts and idea about different reactors which is used for enzymatic transesterification reaction.

Biodiesel is considered eco-friendly, biodegradable, non-toxic, and carbon-neutral fuel. It is made from edible or non-edible oil feedstocks including other triglyceride sources. The production of biodiesel depends on the availability of a particular feedstock and the cost of desired raw materials. Biodiesel is mainly produced by the transesterification process using a suitable catalyst preferably a heterogeneous catalyst as it is more beneficial in terms of reusability, recovery, product purity, and production cost as well. Various reactors are developed to produce cost-effective biodiesel at the commercial level. The latest trend in biodiesel synthesis is the application of the machine learning (ML) technique to optimize the process parameters. The application of a mixture of two or more oils as feedstock either non-edible or edible oil is emphasized for biodiesel synthesis and is presently getting more importance. In this paper, the production of biodiesel from various mixed oil (hybrid oil) is reviewed and the effects of mixed oil on the reaction, physicochemical properties, fatty acid composition, and fuel quality of the product are discussed. The study highlighted the activity of various catalysts in the reaction of mixed oil and the economic feasibility. It was found that the ratio of mixed oil is an important factor in terms of conversion and quality of biodiesel. It is also revealed that the application of the ML technique is essentially useful to optimize production efficiency. The utilization of mixed oils will overcome the issues related to the non-availability of feedstocks and reduce the overall cost with improved quality of biodiesel. This approach enhances the production possibility of biodiesel at a large-scale and may boost the biorefinery sector satisfying the future energy demand if the research at the advanced level goes in the right direction.

In the present work, a solid catalyst has been derived by calcination (550 ​°C, 2 ​h) of waste sugarcane bagasse ash and applied for the production of jatropha seed oil methyl esters (JSOME). The prepared catalyst was well-characterized by using Brunauer–Emmett–Teller (BET) method, Fourier transform infrared spectrometer (FT-IR), X-ray diffractometer (XRD), Field emission scanning electron microscope (FESEM), Energy dispersive X-ray (EDX), High resolution transmission electron microscope (HRTEM) and X-ray photoelectron spectrometer (XPS). The analysis revealed that the catalyst is composed of various metal oxides and carbonates. The catalyst could produce 92.84 ​wt. % yield of JSOME (biodiesel) at 9:1 methanol to oil ratio (MTOR), 10% catalyst and at 65 ​°C in 285 ​min, and found to be reusable. The polycrystalline catalyst with a surface area of 7.66 m2 g-1 and basic strength within 10.1 < H_ < 18.4 possesses good efficacy for the reaction with turnover frequency (TOF) of 6.59 h−1. The kinetic and thermodynamic parameters of the reaction were studied. JSOME was characterized by 1H NMR and GC-MS techniques, and fuel properties were also assessed. Biodiesel synthesis with such a renewable catalyst will add value to waste sugarcane bagasse and is considered sustainable for material development.