Terminalia chebula as a novel green source for the synthesis of copper oxide nanoparticles and as feedstock for biodiesel production and its application on diesel engine

In this study, the components of Terminalia chebula plant such as leaves and seeds are effectively utilized as a green source for the synthesis of copper oxide nanoparticles (CuO NPs) and production of biodiesel, respectively. CuO NPs have been synthesized through solution combustion route using T. chebula leaves extract as a reducing-cum-fuel agent. Notably, the synthesized CuO NPs are used as a heterogeneous catalyst in the biodiesel production. The synthesized CuO NPs are characterized using XRD, FTIR, FESEM, BET, Zeta potential, DLS and UV–visible absorption spectroscopy. The obtained results showed the monoclinic crystal structure of CuO with rod-like morphology with diameter of around 100 nm. The CuO NPs were successfully utilized for the biodiesel synthesis using T. chebula oil as feedstock by varying the reaction parameters. The maximum of 97.1% yield of T. chebula methyl ester (TCME) is achieved at 3 wt% catalyst loading with methanol to oil molar ratio of 9:1 for the reaction time of 60 min at the of temperature 60 °C with constant stirring speed of 650 rpm. The CuO NPs showed a good catalytic stability up to four cycles with a slight loss in biodiesel yield. The kinetic study of TCME production fits well to the pseudo-first order reaction and the activation energy (Ea) and frequency factor (A) is found to be 40.74 kJ/mol and 5.7 × 104 min−1 respectively. Further, the TCME is also characterized by 1H NMR and FTIR. The fuel properties of TCME are also determined and found to be in the range of ASTM standards. The green chemistry metrics such as E-factor, atom economy, atom efficiency and solvent and catalyst environmental impact parameter have also been studied. Furthermore, the performance, combustion and emission characteristics of the test samples (diesel, biodiesel test blends such as B10, B20, B30, B40 and B100) on a single cylinder diesel engine have also been studied by varying the load (0%, 25%, 50%, 75% and 100%). [Display omitted] •For the first time reporting T. chebula leaves and seeds is the green energy source.•Maximum TCME yield of 97.1% has obtained at optimal conditions.•Catalyst reused upto 4th cycle with a slight loss of TCME yield.•The activation energy (Ea) and frequency factor (A) was found to be 40.74 kJ/mol and 5.7 × 104 min−1 respectively.•Green chemistry approach has been studied.