Studying the feasibility of hydroprocessing used cooking oil into hydrogenation derived renewable diesel from local feedstock and catalyst.

Abstract

Identifying and developing heterogeneous catalysts capable of mild-cracking used cooking oil (UCO) into hydrogenation-derived renewable diesel (HDRD) or green diesel production has posed a considerable challenge to commercialization of this fuel type in the energy sector. HDRD has received wide acceptance as alternative renewable energy that guarantees a pollutant-free environment, sustainability, renewability, and possesses a high degree of compatibility with compression ignition (CI) engine with little or no retrofitting needed. This research focuses on the feasibility of locally sourced UCO and catalysts for hydrogenation into green diesel. The objectives of this research are to produce a biofuel for CI engine using biowaste catalyst and UCO as a feedstock. Various studies have highlighted the benefit of UCO as a feedstock for biofuel production. UCO was collected from takeaway outlets. The samples were prepared by the in-situ hybridization method, heated on an electric heater fitted with a magnetic stirrer kept at 110 ⁰C and agitating speed of 50 rpm. The novel approach of in-situ hybridization of waste cooking oil was investigated. The outcome of the investigation showed that hybridization of the samples caused an increase in iodine value from 80.4 cg/g to 100.2 cg/g, affected kinematic viscosity, saponification value, and density, but did not affect cetane number, higher heating value, and acid value. The results are evidence that hybridization is a viable technique for improving the quality of existing feedstock and creating high-quality feedstock for the production of HDRD. Bio-based thermal power plant fly ash (BBTPPFS) was sourced locally from an ESKOM power plant in South Africa, pulverized, and developed into a fine powder, while SiO2, Al2O3, and CaO were procured from a commercial supplier. The samples were reinforced in various proportions and subjected to thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), Scanning Electron Microscopy (SEM), and X-ray diffraction (XRD) characterization processes. The results revealed that SiO2 reinforced with BBTPPFS showed adequate properties that render it viable as a potential low-cost green catalyst for hydrogenation and capable of mild cracking to achieve a green diesel range C15-C18. The properties of locally sourced catalyst and feedstock were evaluated; experimental results revealed that the BET surface area, pore-volume, and micropore volume of fly ash reinforced with SIO2 showed high catalytic viability because of its capability to withstand temperatures up to 950 °C. Also, the addition of SIO2 to BBTPPFS showed a significant percentage increment in quartz, calcite, and mullite. This property is further evidence of its viability as a potential local catalyst for hydrogenation. HDRD were produced from hydro-processed used cooking oil using a locally sourced fly ash catalyst. The properties of HDRD were measured according to the ASTM standards and compared with green diesel. In terms of fuel quality, engine performance, and emission outcome, HDRD showed high yield and exhibited excellent fuel properties. The results from the engine test and combustion performance in a diesel engine are compatible with results from a CI engine, and meet acceptable performance and emission standards.