Sustainable Biodiesel Production Research Articles

Enhanced Biodiesel Production from Waste Cooking Oil Using Potash-Enriched Natural Base Catalyst

The transesterification reaction of waste cooking oil with methanol using a sugar apple peel ash catalyst has been reported. Under optimized conditions, the reaction of the oil with methanol in a molar ratio of 1:10, in the presence of a catalyst (2 g) at 60 °C temperature offered a 94.5% yield of biodiesel within 120 min. The heterogeneous catalyst was developed via a straightforward calcination process using fruit processing industry waste peels of sugar apples. The characterization of the catalyst by FTIR, EDS, SEM, XRD, N2 sorption, and XRF analysis revealed a higher concentration of potassium species which is possibly responsible for the promotion of the transesterification reaction more efficiently. This approach offers cost competitiveness, reusability of the catalyst, simplicity of operation, and high biodiesel yields. This study underscores the potential of utilizing waste materials for sustainable biodiesel production, contributing to environmental preservation and economic viability.

Waste snail shells-derived mixed oxide catalyst for efficient transesterification of vegetable oil: Towards sustainable biodiesel production

This study explores the transesterification process of soybean oil for the production of biodiesel, utilizing an innovative mixed oxide catalyst obtained from discarded snail shells powder. The catalyst synthesis involved a thermal treatment at 900°C for 120 min, predominantly yielding calcium oxide (CaO). In order to evaluate its properties, we carried out a thorough characterization using various analytical techniques. The study explores the impact of crucial variables on the transesterification reaction, such as reaction time (from 30 to 150 min), methanol-to-oil ratio (from 3:1–18:1), and catalyst concentration (from 0.5% to 4% by weight). Optimal conditions emerged with a 90-min reaction time, a 12:1 methanol-to-oil ratio, and a 2% catalyst loading, yielding an impressive biodiesel conversion rate of approximately 93%. The validity of biodiesel conversion was confirmed through Fourier transform infrared spectroscopy (FTIR) and Proton Nuclear Magnetic Resonance Spectroscopy (1 H NMR). The resultant biodiesel exhibited highly favorable characteristics, including an acid value of 0.85 mg of KOH/g, a density of 886.8 kg/m3, and a viscosity of 4.6 mm2/s. These measurements align with the standards set forth in EN 14214 and ASTM D6751 regarding biodiesel quality. The utilization of waste snail shells powder as a precursor for synthesizing the mixed oxide catalyst presents a promising approach for the sustainable production of biodiesel from soybean oil, offering a sustainable and efficient approach to biofuel production.

RSM and ANN methodologies in modeling the enhanced biodiesel production using novel protic ionic liquid anchored on g-C3N4@Fe3O4 nanohybrid

Herin, a new nanohybrid acid catalyst was fabricated for the efficient biodiesel production. At the first, magnetic porous nanosheets of graphitic carbon nitride (g-C3N4@Fe3O4) was prepared and then functionalized with sulfonic acid. Next, the preparation of the catalyst was completed by mixing this surface modified support with n-methyl imidazolium butyl sulfonate zwitterion to achieve non-covalent immobilized acidic ionic liquid on g-C3N4@Fe3O4 support. The catalyst underwent characterization through various techniques such as 1H and 13C NMR, FTIR, SEM, TEM, TGA, EDX and BET which revealing that the magnetic support loaded acidic ionic liquids via a robust charge interaction effect enabling the one-pot production of biodiesel from low-quality oils. Furthermore, the catalyst could be simply recovered using a permanent magnet and reused multiple times without a significant decline in catalytic activity. Consequently, the solid catalyst based on ionic liquids holds promise for the sustainable and eco-friendly production of biodiesel from low-quality oils. Furthermore, Response Surface Methodology (RSM) and Artificial Neural Networks (ANN) were used to model the yield and various process parameters. The findings underscore the enhanced predictive capabilities of ANN in comparison to RSM.

Enhancing high-density microalgae cultivation via exogenous supplementation of biostimulant derived from onion peel waste for sustainable biodiesel production

Microalgae demonstrate significant potential as a source of liquid-based biofuels. However, increasing biomass productivity in existing cultivation systems is a critical prerequisite for their successful integration into large-scale operations. Thus, the current work aimed to accelerate the growth of C. vulgaris via exogenous supplementation of biostimulant derived from onion peel waste. Under the optimal growth conditions, which entailed a biostimulant dosage of 37.5% v/v, a pH of 3, an air flow rate of 0.4 L/min, and a 2% v/v inoculum harvested during the mid-log phase, yielded a maximum biomass concentration of 1.865 g/L. Under the arbitrarily optimized parameters, a comparable growth pattern was evident in the upscaled cultivation of C. vulgaris, underscoring the potential commercial viability of the biostimulant. The biostimulant, characterized through gas chromatography-mass spectrometry (GC-MS) analysis, revealed a composition rich in polyphenolic and organo-sulphur compounds, notably including allyl trisulfide (28.13%), methyl allyl trisulfide (23.04%), and allyl disulfide (20.78%), showcasing potent antioxidant properties. Additionally, microalgae treated with the biostimulant consistently retained their lipid content at 18.44% without any significant reduction. Furthermore, a significant rise in saturated fatty acid (SFA) content was observed, with C16:0 and C18:1 dominating both bench-scale (44.08% and 14.01%) and upscaled (51.12% and 13.07%) microalgae cultures, in contrast to the control group where C18:2 was prevalent. Consequently, SFA contents reached 54.35% and 65.43% in bench-scale and upscaled samples respectively, compared to 33.73% in the control culture. These compositional characteristics align well with the requirements for producing high-quality crude biodiesel.

Preparation CaO/MgO/Fe3O4 magnetite catalyst and catalytic test for biodiesel production

Biodiesel is a promising renewable fuel with lower emissions and environmental friendly. This research investigated the potential of a CaO/MgO/Fe3O4 nanomagnetic catalyst synthesized from dolomite and iron sand for biodiesel production from waste cooking oil. The influence of catalyst loading, Fe3O4:CaO/MgO mass ratio, and calcination temperature on biodiesel yield was investigated and the catalyst was characterized using XRD, SEM, and PSA techniques. The optimal reaction conditions were found at 1 % w/w catalyst loading, Fe3O4:CaO/MgO weight ratio of 1:7.5 w/w, and 1000 °C calcination temperature, which result in 95.640 % yield. The produced biodiesel has fulfill the quality standards for density and viscosity. This work also demonstrates the effectiveness of CaO/MgO/Fe3O4 nanomagnetic catalysts for sustainable biodiesel production from waste feedstock, offering a promising approach for waste management and cleaner fuel alternatives.

Utilizing Waste Cooking Oil for Sustainable Biodiesel Production: A Comprehensive Review

The environmental and economic challenges posed by the over-reliance on fossil fuels have driven the search for alternative and sustainable energy sources. Waste cooking oil (WCO) presents a viable feedstock for biodiesel production, offering a dual solution to waste management and renewable energy generation. This comprehensive review examines the current state of biodiesel production from waste cooking oil, exploring the benefits, challenges, and processes involved. Biodiesel derived from WCO has several environmental advantages, including lower greenhouse gas emissions, biodegradability, and enhanced engine lubricity compared to traditional fossil fuels. Moreover, utilizing it for biodiesel addresses waste disposal issues, reducing the contamination of land and water resources. Despite these benefits, several challenges remain, such as the variability in its composition, contamination, and the need for efficient purification and transesterification processes. The review explores various methods for converting WCO into biodiesel, highlighting the key stages of the transesterification process, including the use of catalysts, alcohols, and reaction conditions. Additionally, advanced techniques such as ultrasound-assisted and microwave-assisted transesterification are discussed for their potential to increase efficiency and reduce processing time. This paper also addresses the sustainability aspects of biodiesel production from it, emphasizing its role in promoting a circular economy and reducing waste. The use of its contributes to a closed-loop system, where waste is transformed into a valuable resource. Furthermore, the review explores the economic and social impacts of biodiesel production, noting its potential to create jobs, reduce import dependence, and support local communities. In conclusion, this review underscores the significant potential of waste cooking oil in sustainable biodiesel production. It calls for continued research and technological innovation to optimize processes, enhance efficiency, and overcome existing challenges, thereby contributing to a cleaner and more sustainable energy landscape.

Green synthesis of highly active and recyclable chromium oxide nanocatalyst for biodiesel production from novel nonedible oil seeds

AbstractThis study explores the sustainable production of biodiesel from nonedible Phyllanthus maderaspatensis seed oil (highest oil content of 35%, FFA 0.87 mg/KOH), utilizing an innovative green synthesis approach for chromium oxide nanoparticles derived from the waste fruit parts of Aubergine for the very first time in the current work. In pursuit of alternatives to fossil fuels, our research underscores the environmental and socio‐economic benefits of biofuels, particularly in reducing greenhouse gas emissions. The optimized process yielded a 92% biodiesel conversion under conditions of a 9:1 methanol‐to‐oil ratio, 0.135 wt.% catalyst concentration, and a reaction duration of 150 min at 80°C. Comprehensive analysis techniques, including XRD, FTIR, SEM, EDX, Zeta analysis, differential reflectance spectroscopy (DRS), GC–MS, and NMR (1H, 13C), were employed to characterize the synthesized nanocatalyst and biodiesel product. The biodiesel's fuel properties, such as acid value, fire point, pour point, viscosity, kinematic density, sulfur content, and cloud point, were rigorously tested, demonstrating compliance with international standards (ASTM D‐6571, EN 14214, and GB/T 20828‐2007). The use of P. maderaspatensis seed oil, an economical and environmentally friendly feedstock, in conjunction with a cost‐effective nanocatalyst, presents a viable pathway for the sustainable and scalable production of biodiesel. This study contributes to the advancement of bioproducts for a sustainable bioeconomy by demonstrating an integrated approach to bioenergy production that leverages biotechnological innovations and addresses both environmental and socio‐economic dimensions.

Unleashing the power of non-edible oil seeds of Ipomoea cairica for cleaner and sustainable biodiesel production using green Molybdenum Oxide (MoO3) nano catalyst

This research aims to conduct a thorough analysis of the novel and cost-effective use of Ipomoea cairica L. seeds as a potential feedstock for green energy technologies. Ipomoea cairica L. seeds (42 % oil, 0.67 % free fatty acid content) were used as a promising source for producing sustainable biodiesel using novel green Molybdenum Oxide (MoO3) nanocatalyst. The Ipomoea cairica seeds utilized in this study serve a dual purpose: they provide feedstock for the future energy mix, and their seed shells (considered waste) are used as a starting material for synthesizing green nanocatalysts. The highest biodiesel yield of 95 % was achieved under optimal reaction conditions of 1:15 oil to methanol molar ratio, 50 °C, 120 min, and 0.4 (wt.%) catalyst loading. In order to evaluate the quality and characteristics of the resultant biodiesel and synthesized nanocatalyst, a detailed examination was conducted utilizing analytical techniques such EDX, XRD, FTIR, SEM, NMR (1H, 13C) and GC–MS analysis. The phytofabricated nanocatalyst unveils highest recyclability (up to 5 cycles), reactivity, stability and efficiency during transesterification operations. The produced biodiesel was also optimized using response surface methodology (Box-Behnken Design). When compared to conventional diesel, the biodiesel made from Ipomoea cairica L. seed oilshowed better oxidative stability and reduced viscosity, suggesting that it might be a viable replacement for conventional fuel without compromising engine performance. Moreover, using untamed, uncultivated, and non-edible seed plants to produce biodiesel presents a chance to move toward a more sustainable and environmentally friendly energy plan.

Sustainable production of biodiesel enabled by acid-base bifunctional ZnF2 via one-pot transformation of Koelreuteria integrifoliola oil: Process optimization, kinetics study and cost analysis

Against the backdrop of energy crisis and quest for carbon neutrality, efficient utilization of heterogeneous catalysts to facilitate one-pot conversion of low-quality nonedible oils into biodiesel, shows enormous promise for the reduction of carbon footprints and environmental pollution. In this study, an effective heterogeneous catalyst, acid-base bifunctional mesoporous ZnF2 (MP-ZnF2) was successfully fabricated for biodiesel synthesis from Koelreuteria integrifoliola oil (KIO, acid values of 8.26 mg KOH/g) via facile one-pot process. Meanwhile, systematic characterization showed the large specific surface area (62.9 m2/g), abundant mesoporous (12.15 nm), outstanding thermal stability, and plentiful stable acid-base sites (1.22 and 0.56 mmol/g) of MP-ZnF2. Consequently, MP-ZnF2 achieved a high biodiesel yield of 97.15% under moderate conditions (103 °C, 6.2 h, 10.2 wt% catalyst dosages, 29:1 MeOH/KIO molar ratio) optimized by response surface methodology (RSM). More importantly, through the kinetic investigation, a low activation energy of 49.24 kJ/mol explained the reason for its high activity, and the possible reaction mechanism of (trans)esterification was also proposed. In addition, MP-ZnF2 demonstrated satisfactory reusability (6th cycle, >90%), water resistance (8 wt% water content, 89.25%), and versatility (all yields >90%). According to cost analysis, the price of biodiesel in this work was about 0.64 $/kg. Notably, the as-prepared biodiesel conformed to ASTM D6751 and EN 14,214 standards, indicating great application prospects. It was demonstrated that one-pot transformation of KIO into biodiesel using acid-base bifunctional MP-ZnF2 contributes to the sustainable development of clean energy.

Sustainable microwave-supported biodiesel production using sandbox oil and its waste shell as a nanoparticle green alkali heterogeneous catalyst

This present work explored the possible use of sandbox seed (Hura crepitans) shell (SSS) waste as a feedstock for synthesizing green solid alkali biocatalyst in the microwave-aided sandbox oil (SBO) transesterification to obtain SBO biodiesel (SBOB). The solid catalyst was produced using a calcination method by burning raw SSS in the open air to obtain ash heated for 3 h in a furnace at 500 °C. The calcined sandbox shell ash (CSSA) produced was characterized using standard techniques to establish its catalytic potency. Also, a model was developed to simulate the process and examine the interactive effect of process input variables on SBOB yield using the Taguchi approach. The CSSA characterization showed it composed of K (44.99 %), Ca (1.54 %), and Mg (1.87 %) with crystalline compounds of K and Mg. The physisorption results gave a mean pore size of 18.142 nm and a surface area of 6.1125 m2/g. The best combination of the input variables determined for the process is a heating power of 450 W, methanol:SBO of 8:1, time of 1.5 min, and CSSA loading of 2 wt% with an optimum SBOB yield of 98.27 wt%. The SBOB produced met standard specifications for biodiesel. Microwave application to the SBO transesterification aided in rapidly completing the reaction. The study concluded that sandbox seeds and their shells are promising feedstock for cheap and sustainable biodiesel production.

Catalytic Conversion of Jatropha curcas Oil to Biodiesel Using Mussel Shell-Derived Catalyst: Characterization, Stability, and Comparative Study

Biodiesel represents a promising solution for sustainable energy needs, offering an eco-friendly alternative to conventional fossil fuels. In this research, we investigate the use of a catalyst derived from mussel shells to facilitate biodiesel production from Jatropha curcas oil. Our findings from X-ray Fluorescence (XRF) analysis emphasize the importance of carefully selecting calcination temperatures for mussel shell-based catalysts, with 1100 °C identified as optimal for maximizing CaO content. We identify a reaction time of 6 h as potentially optimal, with a reaction temperature of approximately 110 °C yielding the desired methyl ester composition. Notably, a methanol-to-oil ratio of 18:1 is the most favorable condition, and the optimal methyl ester composition is achieved at a calcined catalyst temperature of 900 °C. We also assess the stability of the catalyst, demonstrating its potential for reuse up to five times. Additionally, a thorough analysis of J. curcas Methyl Ester (JCME) biodiesel properties confirmed compliance with industry standards, with variations attributed to the unique characteristics of JCME. Comparing homogeneous (NaOH) and heterogeneous (CaO) catalysts highlights the potential of environmentally sourced heterogeneous catalysts to replace their homogeneous counterparts while maintaining efficiency. Our study presents a novel approach to sustainable biodiesel production, outlining optimal conditions and catalyst stability and highlighting additional benefits compared with NaOH catalysts. Therefore, utilizing mussel shell waste for catalyst synthesis can efficiently eliminate waste and produce cost-effective catalysts.

Characterization of GPAT gene family in Euphorbia lathyris L. and elucidating the role of ElGPAT9 in the biosynthesis of oils and pollen viability

Caper spurge (Euphorbia lathyris L.), known for its high content of oleic acid-enriched seed oils, has gained recognition as a valuable non-edible feedstock for biodiesel production. However, there is limited understanding of the biosynthesis and regulation of these desirable seed oils. In this study, an omics-based approach and genetic transformation were employed to investigate the glycerol-3-phosphate acyltransferase (GPAT) enzyme, which catalyzes the initial acylation reaction in triacylglycerol (TAG) biosynthesis, in caper spurge. Ten genes encoding ElGPAT, identified from the E. lathyris genome, were classified into three phylogenetic groups, exhibiting similar protein motifs and gene structures. RNA-seq data revealed distinct expression patterns of these ElGPAT genes in various tissues and different stages of seed development. Notably, ElGPAT9 showed the highest expression in flowers and developing seeds, with its encoded protein localized in the endoplasmic reticulum. Experiments using a yeast (Saccharomyces cerevisiae) expression system demonstrated that ElGPAT9 exhibited strong GPAT enzyme activity, crucial for TAG assembly, and preference for oleic acid (C18:1), as confirmed by feeding tests with exogenous fatty acids (FA). Similarly, stable transgenic lines of Nicotiana tabacum over-expressing ElGPAT9 showed increased levels of total oil and oleic acid, as well as improved pollen viability, without any growth penalty compared to wild-type and empty-vector controls. The transcriptome based WGCNA also identified genes related to lipid synthesis that are co-expressed with ElGPAT9. These findings provide a foundation for further understanding the roles of ElGPAT family members in E. lathyris and suggest the potential of ElGPAT9 as a desirable target for genetic engineering to enhance the production of vegetable oils enriched with C18:1 in caper spurge and other oil crops, contributing to sustainable biodiesel and lipid product production.

Magnesium Oxide (MgO) as a Sustainable Catalyst for Biodiesel Production from Waste Cooking Oil: A Comparative Study with KOH

The present study investigates the efficiency of magnesium oxide (MgO) as a heterogeneous catalyst in the production of biodiesel from waste cooking oil (WCO), putting an emphasis on its environmental benefits, cost-effectiveness, and operational efficacy. Through a series of experiments, we optimized the reaction conditions, including catalyst concentration, reaction temperature, and ethanol to WCO molar ratio, to achieve a high biodiesel yield. The results indicate that an optimal MgO concentration of 3 wt%, a reaction temperature of 65 °C, and a molar ratio of 9:1 result in the highest biodiesel production efficiency. Additionally, MgO demonstrated significant reusability without a decrease in performance, underscoring its economic and environmental advantages. Comparative analysis revealed that MgO outperforms conventional KOH catalysts in terms of yield, purity, and sustainability. Our study suggests future research directions, including the optimization of MgO preparation methods and the exploration of co-catalyst systems to further enhance biodiesel production from WCO. This research contributes to the development of sustainable biodiesel production methods, aligning with global energy and environmental goals.

Sustainable Biodiesel Production via Chlorella vulgaris and Tetraselmis Chuii in Food-based Brewery Industrial Wastewater

Sustainable Biodiesel Production via Chlorella vulgaris and Tetraselmis Chuii in Food-based Brewery Industrial Wastewater

Valorization of Sugarcane Vinasse and Crude Glycerol for Single-Cell Oils Production by Rhodotorula glutinis R4: A Preliminary Approach to the Integration of Biofuels Industries for Sustainable Biodiesel Feedstock

Single-cell oils (SCOs) offer a promising alternative to conventional biodiesel feedstocks. The main objective of this work was to obtain SCOs suitable for biodiesel production from the oleaginous yeast Rhodotorula glutinis R4 using sugarcane vinasse from a local sugar-derived alcohol industry as the substrate. Additionally, crude glycerol from the local biodiesel industry was evaluated as a low-cost carbon source to replace expensive glucose and as a strategy for integrating the bioethanol and biodiesel industries for the valorization of both agro-industrial wastes. R4 achieved a high lipid accumulation of 88% and 60% (w/w) in vinasse-based culture media, containing 10% and 25% vinasse with glucose (40 g L−1), respectively. When glucose was replaced with crude glycerol, R4 showed remarkable lipid accumulation (40%) and growth (12.58 g L−1). The fatty acids profile of SCOs showed a prevalence of oleic acid (C18:1), making them suitable for biodiesel synthesis. Biodiesel derived from R4 oils exhibits favorable characteristics, including a high cetane number (CN = 55) and high oxidative stability (OS = 13 h), meeting international biodiesel standards (ASTMD6751 and EN14214) and ensuring its compatibility with diesel engines. R. glutinis R4 produces SCOs from vinasse and crude glycerol, contributing to the circular economy for sustainable biodiesel production.

Solar radiation powered biodiesel synthesis using C&D waste catalyst – a novel approach

A significant amount of construction and demolition waste is generated in India every year. The proper management of this waste has become a crucial concern due to fast urban growth, building projects, and increased construction work. The volume of this waste is substantial, which can harm the environment, deplete resources, and pose health risks if not handled well. This study presents an innovative method for biodiesel synthesis, addressing the challenges of construction and demolition (C&D) waste management and renewable energy integration. The research introduces a novel catalyst derived from C&D waste through a calcination process, offering an eco-friendly solution for waste repurposing. This catalyst demonstrates potential for sustainable biodiesel production, marking a significant advancement in waste management practices. Furthermore, a pioneering solar-powered reactor is utilized for biodiesel synthesis, achieving an impressive 92.2% conversion rate under specific conditions. The system's energy efficiency, calculated as [Formula: see text], surpasses conventional methods, highlighting its potential for reducing energy consumption and environmental impact. Moreover, the produced biodiesel meets ASTM D6751 standards, ensuring quality and compatibility with industry requirements.

Musa balbisiana colla banana flower derived magnetic heterogeneous nanocatalyst for cleaner biodiesel production from jatropha oil

Banana flower has been used to create a very effective magnetically separable basic heterogeneous nanocatalyst for the production of sustainable biodiesel using jatropha oil. The potentiality of the innovative catalyst was assessed through the study performed by fourier transform infrared (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectrometer (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), and thermogravimetric (TG) analysis. The magnetic nanocatalyst appeared as quasi spherical and core/shell structure, with a mean size of 19.47 nm. The catalyst's significant calcium (3.5%) and potassium (32.4%) contents indicates that the catalyst is quite basic in nature. With a catalyst load and methanol to oil ratio of 6 wt% and 9:1 respectively at 60 °C, the synthesized basic nanocatalyst produced 97.2 ± 1.15% biodiesel yield in 60 ± 2 min. It was discovered that the catalyst's basicity and surface area were 0.612 mmol/g and 64.4 m2 g−1 respectively. The transesterification reaction proceeded via pseudo-first order kinetics with an activation energy (Ea) of 33.25 kJ mol−1. The transesterification process exhibits endergonic and non-spontaneous behaviour as suggested by the values of entropy change (ΔS) and enthalpy change (ΔH) as 20.785 and −4.43 kJ mol−1 K−1 respectively. The catalyst showed promising catalytic stability and reactivity up to 3rd cycle with sufficient magnetization value of 17.43 emu/g and potassium content of 22.38% which endorsed biodiesel yield of 91.5% at 3rd cycle.

Nutrient and salinity stress induced biodiesel production from a green alga, Monoraphidium neglectum

The potential of a green alga as a versatile and sustainable feedstock for biodiesel production was assessed. Molecular identification revealed the alga to be Monoraphidium neglectum. Under diverse growth conditions, including nutrient deficiency and salinity stress, the microalga showed robust adaptability. Under nitrate deficiency (N-, the lipid content peaked (30.67 %), with a notable increase in monounsaturated fatty acids (MUFA), reaching 50.72 % in the stressed sample. Additionally, the highest polyunsaturated fatty acid (PUFA) content (24.55 %) was observed at a salinity level of 0.12 M. At 0.01 M salinity, the highest total carbohydrate content was observed. A significant fatty acid methyl ester (FAME) yield of 85.08 % was obtained under nitrate deficiency (N-) emphasizing its biodiesel production potential. The as-obtained biodiesel exhibited low viscosity, superior low-temperature performance and enhanced oxidation stability rendering the alga as an ideal candidate for eco-friendly, sustainable biodiesel production.

Production of biodiesel from waste culinary oil catalyzed by S2O82−/TiO2–SiO2 solid super-acid catalyst prepared with recovered TiO2 from spent SCR

Recovery and valorization of natural resources from waste materials are crucial for promoting sustainable development. In light of this, the present study explores the transesterification of waste culinary oil into biodiesel production using a silica-supported solid super-acid catalyst (S2O82−/TiO2–SiO2) prepared with recovered TiO2 from spent SCR. The synthesized materials were characterized through XRD, SEM-DES, XPS, FT-IR, NH3-TPD, and N2-BET analysis. Notably, the crystal structure of recovered TiO2 was not destroyed during the whole process. N2-BET analysis showed that the silica-supported catalyst significantly increased the specific surface area from 47.89 to 101.16 g/m2. The presence of superacid sites (Brønsted and Lewis acid sites) on the surface of the catalyst was confirmed by NH3-TPD and FT-IR analysis. The silica-supported catalyst (S2O82−/TiO2–SiO2) exhibited high catalytic activity for free fatty acid (FFA) about a conversion rate of 90.7 % under optimal reaction conditions: a reaction time of 4 h, at 180 °C with a 5 wt% catalyst loading, and a methanol-to-oil molar ratio of 12:1. The biodiesel production was confirmed by using FT-IR and 1HNMR techniques. Furthermore, the catalytic performance of the prepared catalyst was compared with other catalysts prepared from pure TiO2 reported in the literature. This approach showed a potential for sustainable biodiesel production by using low-cost solid acid catalyst synthesized from recovered materials.

Environmentally-friendly preparation of Sn(II)-BDC supported heteropolyacid as a stable and highly efficient catalyst for esterification reaction

Facilitating energy resource deficiency and environmental contamination, this work focuses on sustainable biodiesel production through the esterification reactions of oleic acid (OA) with methanol. To address the reaction, a novel heterogeneous acid catalyst, 12-tungstophosphoric acid (TPA) immobilized on Sn-based MOFs (Sn(II)-BDC) was synthesized via a simple, green solvent, and easy-to-implement synthesis strategy for the first time, and applied effectively for esterification process of OA to produce biodiesel. The structure and composition of as-obtained catalyst have been verified using XRD, FTIR, N2 physisorption, SEM, EDX, TG, Py-FTIR, TPD-NH3, and XPS techniques. The obtained TPA/Sn(II)-BDC catalyst was found to be the best with 60 wt% of TPA loading, which resulted in an OA conversion of 91.7 % at optimized conditions of 0.15 g catalyst loading and methanol to OA molar ratio of 20:1 at temperature of 120 °C in 4 h, and the excellent performance arises from available pores structure, large amounts of acidic sites, good stability and the synergistic catalytic effect of TPA and Sn(II)-BDC. Furthermore, the composite catalyst reusability has been studied for five cycles, and it exhibits an acceptable conversion. This research provides a green and large-scale synthesis route for the sustainable production of biofuels by constructing heteropolyacids/Sn-based MOFs synergistic catalysts.