Revolutionizing biodiesel with novel MWCNT-COOH@TiO2-ZnO nanocatalysts for enhanced transesterification and tribocorrosion resistance

The present work describes the development of a new nanocatalyst that features a multiwalled carbon nanotube functionalized with titanium dioxide and zinc oxide (MWCNT-COOH@TiO2-ZnO). The catalyst was designed to increase the biodiesel yield of used cooking oil (UCO) and reduce problems associated with tribocorrosion in biodiesel-powered engines. Techniques including X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy with energy dispersive spectroscopy, were employed to investigate the structural and surface properties of the nanocatalyst.The results showed that the catalyst had a surface area of 260.13 m2/g, and a pore diameter of 9.47 nm, which were considered to provide an optimum catalytic interface. These properties allowed for highly effective transesterification of the UCO, and the biodiesel yield reached 98.6 % under optimal conditions. Using the Taguchi method, the optimum parameters were determined as a catalyst loading of 0.4 g, a reaction temperature of 45 °C, a methanol-to-oil molar ratio of 10:1, a stirring speed of 400 rpm, and a reaction time of 90 min. These results validate the suitability of the biodiesel for use in engines, meeting the ASTM standards for the quality and safety parameters of fuels for use in internal combustion engines. The nanocatalyst was highly reusable and retained an efficiency of 93.2 % after three runs. In the tribocorrosion tests, notable wear rate reductions of 67.8, 67.7, and 62.0 % were recorded at 10, 20, and 30 N loads, respectively. While the nanocatalyst performed well, future research may explore regeneration, stability, scalability, nanocomposites, engine dynamics, and machine learning to boost performance and sustainability.