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This paper reports experimental conversion of spent vegetable oil with bio-ethanol to long chain biodiesel fuel in presence of a new developed solid K3PO4 heterogeneous catalyst. Examined catalyst was synthesized following dipping impregnation of γ-Al2O3 solid support in an aqueous solution of potassium phosphate tri-basic K3PO4. K3PO4/γ-Al2O3 catalyst samples were distinguished based on their percentage loadings of K3PO4 (CK3PO4) and averaged particle size (dp). Produced catalyst samples were characterized in terms of their textural and surface properties using nitrogen adsorption-desorption isotherms and carbon dioxide & ammonia temperature programmed desorption techniques respectively. While the liquid phase of the product was analyzed using a GC-Mass spectroscopy technique. Ethanolysis runs were carried out following surface response methodology, central composite design (CCD).

This paper reports the optimisation study of a batch scaled ethanolysis conversion of waste frying oil carried out over aluminium phosphate-potassium bi-functional catalysts. All synthesised catalysts were analysed for their structural and surface chemical properties thereby following N2 adsorption-desorption isotherm and CO2 and NH3-temperature programmed desorption techniques respectively. X-ray diffraction and x-ray photoelectron spectroscopy were also adopted for phase identification and atomic quantification studies respectively. Ethanolysis experiments were carried out eliminating reaction rate limitations caused by solid-liquid interfacial mass transport and intraparticle diffusion. Other operating parameters were also examined in the study. These included; reaction temperature, catalyst percentage loading on support, catalyst weight and reactants molar ratio (β).

Developing relatively cheap and widely available resources for heterogeneous solid catalyst synthesis is a promising approach for biodiesel fuel industry. Seashell which is essentially calcium carbonate can be used as a basic support for transesterification heterogeneous catalysts. In the present investigation, the alcoholysis of waste frying oil has been carried out using seashell-supported K₃PO₄ as solid catalyst. The rationale for this derives from the fact that waste frying oil contains both long-chain free fatty acids (FFA) and triglycerides (TG) which are catalyzed on acid and basic sites respectively. Thus, the K₃PO₄/seashell catalyst may serve the dual role of promoting both esterification and transesterification reactions. The catalyst was synthesized following a dipping impregnation of pre-crushed and calcined seashell in an aqueous solution of K₃PO₄. Samples with different percentage loadings of K₃PO₄ (5 to 25 wt%) were prepared.

Biodiesel obtained from the transesterification of vegetable oil or animal fat is a promising renewable green alternative fuel for compression ignition engines. Compression ignition engines are particularly suitable for medium-to-large road, rail and marine use. This is due to their excellent efficiency and longer operation life which is about twice as much as that for spark ignition engines. The replacement of conventional diesel fuel with biodiesel fuel is an attractive solution since the latter is regarded as a renewable, biodegradable, non-poisonous, and oxygenated fuel. However, existing production technologies offer less competitive prices than petroleum-derived diesel due to high input feed and biodiesel purification costs. Non-edible vegetable oils such as waste cooking oils may be used as cheaper substitutes to virgin edible vegetable oils in the feed stream.