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Biodiesel production waste cooking oil is usually limited by its high free fatty acid and moisture content. The synergetic effect of both base and acid source from biomass was employed to proffer way out to this challenge. This study shows the coupled development of sulfonated carbonized corn cob (S-CCC) and calcined cow-bone (C-CB) catalysts for transesterification of waste cooking oil. The catalyst was prepared by physically mixing several mass percentages of S-CCC and C-CB (fluorapatite) in strategic proportions. The maximum biodiesel yield of 96.2 % was attained for catalyst mixture of 60 wt% and 40 wt%. The developed catalyst mixture was characterized by Fourier Transform Infrared Ray (FTIR), powder X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), Brunauer–Emmett-Teller (BET). The surface area (472.3 m2/g), pore size (2.4330 nm) and volume (0.1380 cc/g) were obtained for the catalyst. The XRD shows that the crystallized structure of the bifunctional catalyst was formed majorly between 2 theta 10 and 65.Also the SEM shows a well dispersive pattern of the particles of the catalyst. The developed catalyst was employed for biodiesel optimization studies by varying factors such as time, temperature, catalyst loading and methanol: oil using optimal design under the response surface methodology. Maximum yield of 98.98 % was attained at time 6 h, temperature 65 °C, catalyst loading 6 %wt/ wt of oil and methanol to oil ratio of 11.75:1. It was observed that time and temperature had notable effect on the biodiesel yield.

Biodiesel properties are in general attributed to the composition and properties of the oil feedstock used, overlooking the possible impacts of the catalyst preparation details. In light of that, the impacts of different catalyst preparation techniques alongside those of different support materials on the yield, composition, and fuel properties of biodiesels produced from the same oil feedstock were investigated. More specifically, tri-metallic (Fe-Co-Ni) catalyst was synthesized through two different techniques (green synthesis and wet impregnation) using MgO or ZnO as support material. The generated catalyst pairs, i.e., Fe-Co-Ni/MgO and Fe-Co-Ni/ZnO prepared by wet impregnation and Fe-Co-Ni-MgO and Fe-Co-Ni-ZnO prepared by green synthesis (using leaf extracts) were used in the transesterification process of Jatropha curcas oil. Detailed morphological properties, composition, thermal stability, crystalline nature, and functional groups characterization of the catalysts were also carried out. Using Box-Behnken Design response surface methodology, it was found that the green-synthesized Fe-Co-Ni-MgO catalyst resulted in the highest biodiesel yield of 97.9%. More importantly, the fatty acid methyl ester (FAME) profiles of the biodiesels produced using the four catalysts as well as their respective fuel properties were different in spite of using the same oil feedstock.

In this present study transesterification of used vegetable oil (UVO) using synthesized activated anthill as catalyst was investigated. The catalyst was prepared via calcination process, characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) techniques. From the BET analysis; calcination temperature has a positive impact on the textural properties. The XRD shows that the catalyst is crystalline in nature. Fatty acid methyl esters (FAME) was produced using thermally activated anthill as catalyst. The optimal FAME yield of 94.85 % was obtained at Methanol/Oil (M/O) 9:1, catalyst loading 1.5 wt%, reaction temperature of 65 ᵒ𝑪 and reaction time of 2 h. The physico-chemical properties of UVO – FAME produced was found to be within the American Society for Testing and Methods (ASTM). Hence, the study reveals that used vegetable oil catalyzed by novel activated anthill could be an effective feedstock to produce sustainable energy. Keywords: Anthills, FAME, Central composite design, Heterogeneous, used vegetable oil.

Mixed solid oxides are known for their excellent catalytic property and applications in environmental remediation. This study presents a green-synthesis route for magnesium oxide–titanium oxide, a mixed oxide here demonstrated to possess high performance of phenol removal from hydrocarbon refinery process wastewater. Mixed oxide (MgO-TiO2) was prepared by using the whole extract from leaves of Piliostigma Thonningii as reducing agent. A structural attribute of the mixed oxide was investigated using X-ray Diffractometer, High-Resolution Scanning Electronic Microscopy and Energy Dispersive X-ray. Petroleum refinery raw wastewater having phenol concentration of 19.961 mg/L was treated using the green-synthesized mixed oxide. Adsorptive phenols removal up to 99.5% was achieved with a dosage of 0.04 g/100 mL at temperature of 35 °C, and contact time of 1.167 h. By this, the treated water meets the standard acceptable phenol concentration (0.1 mg/L) in wastewater of hydrocarbon refinery.

Calcium-carbide residue (CCR) was used as a precursor to synthesise CaO–Al2O3–SiO2–CaSO4 heterogeneous acid catalyst for biodiesel production. The synthesis was through a two-step process of thermal treatment of the CCR at 500, 700, and 900 °C and sulphonation, to produce anhydrite-based solid-acid catalysts (ASACs) as ASAC500, ASAC700, and ASAC900 respectively. The CCR and ASACs were characterised using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Brunauer–Emmet–Teller (BET). The ASACs were tested for biodiesel production using high free fatty acid waste lard. The XRD analyses show that the three catalysts consist of CaSO4 in addition to each containing Ca2.62Al9.8Si26.2O72H4.56 (ASAC500), carbon atom and Ca2.62Al9.8Si26.2O72H4.56 (ASAC700), Ca2.62Al9.8Si26.2O72H4.56 and Ca2Al4Si14O36•14H2O (ASAC900). The SEM images of the ASACs show the formation of different surface morphology with active sites and improved porosity based on calcination temperatures. The BET analysis presents a surface area of 94.48 (ASAC500), 90.28 (ASAC700), and 98.22 m2/g (ASAC900). The biodiesel yields obtained using 5% (w/w) catalyst, 12:1 of MeOH: Lard molar ratio, 120 min reaction time and 60 °C reaction temperature are 94.8% (ASAC500), 89.2% (ASAC700) and 98.9% (ASAC900). The excellent performance of CaO–Al2O3–SiO2–CaSO4 catalyst with the high yields of biodiesel and recyclability of seven cycles are attributed to the synergy among the calcium, aluminium, and silicon. Therefore, the CCR is a suitable precursor to synthesise a novel heterogeneous acid catalyst that is highly effective for biodiesel production.