Photothermal-driven CaO-CNT catalyst enhancing transesterification for energy-efficient biodiesel production

CaO-CNT absorbs 92% broad-spectrum light and rapidly produces localized heat. • Photothermal transesterification delivers efficient energy supply to active sites. • Under optimal conditions, 99.22% biodiesel conversion is achieved at 50 °C. • LCA demonstrates low carbon profile with GWP 2.07 kg CO 2 eq·kg −1 and DFF 28.24 MJ·kg −1 . Transesterification for biodiesel production demands external heat supplied through temperature gradient-driven heating, which limits energy efficiency. Photothermal catalysis offers an alternative route, but reported photothermal catalysts for biodiesel transesterification often suffer from narrow-spectrum light harvesting, strict requirements for monochromatic high-power light sources, and inefficient heat delivery to active sites, which severely restrict their practical application. In this study, a CaO-CNT photothermal catalyst was fabricated via wet impregnation coupled with high-temperature calcination to enable in-situ solar-to-heat conversion and boost catalytic activity. Multiple characterization techniques, including TG/DTG, XRD, XPS, SEM, Raman spectroscopy, N 2 adsorption and desorption, UV-Vis-NIR spectroscopy and infrared thermal imager were carried out, and simulated sunlight from a xenon lamp was used for palm oil photothermal transesterification. The CaO-CNT catalyst exhibited 92% light absorption over 300-2500 nm and rapidly increased its surface temperature from ambient temperature to 70.7 °C within 300 s under an irradiation power density of 14.5 W/g. Compared with conventional water-bath heating, photothermal heating catalyzed by CaO-CNT resulted in higher biodiesel conversions, with improvements of 7.71%, 12.48%, and 9.71% at 46 °C, 50 °C, and 54 °C, respectively. The maximum biodiesel conversion of 99.22% was achieved by photothermal-driven heating with a catalyst loading of 6 wt%, a methanol/oil molar ratio of 10, and an irradiation power density of 15.2 W/g for 2.5 h. Findings from life cycle assessment (LCA) established that the global warming potential (GWP) of this process reached 2.07 kg CO 2 eq·kg −1 , with the depletion of fossil fuel (DFF) amounting to 28.24 MJ·kg −1 . Download: Download high-res image (194KB) Download: Download full-size image