Biomass-derived hydrophobic metal-organic frameworks solid acid for green efficient catalytic esterification of oleic acid at low temperatures

Biodiesel, of great significance, is a promising kind of non-polluting renewable energy that can meet world energy needs. However, the by-product water of esterification reaction used for biodiesel production is not conducive to the positive reaction, and even destroys the activity and structure of the used catalyst. In this study, a renewable solid acid catalyst FDCA/SA-Hf with a degree of hydrophobicity was simply prepared by a solventfree assembly manner using biomass-based materials. FDCA/SA-Hf was found to be efficient for producing biodiesel from the abundant free fatty acid and nonedible raw oils at a low temperature, and its reaction mechanism was also studied. FDCA/SA-Hf showed stable structural properties and excellent hydrophobic network (131.5 degrees), wherein the chemical grafting of stearic acid improved its Lewis acidity and promoted the adsorption of free fatty acid and the desorption of water. Importantly, as promoted by FDCA/SA-Hf in esterification, a high biodiesel yield reached 98.6% (49 degrees C, 4.1 wt%, 19.5:1 and 9.5 h). After being easily reused, biodiesel yield still achieved 90% even in the presence of 6 wt% water or after six cycles, which was due to the high hydrophobicity and stability. FDCA/SA-Hf shows great potential in heterogeneous acid-mediated catalytic fields, especially for biodiesel production.

Automated summary

In this study, a renewable solid acid catalyst FDCA/SA-Hf with a high degree of hydrophobicity was prepared using biomass-based materials. FDCA/SA-Hf showed efficient performance in producing biodiesel from free fatty acids and nonedible raw oils. It exhibited stable structural properties and excellent hydrophobic network, enabling high biodiesel yield and good reusability. Therefore, FDCA/SA-Hf has great potential in the field of heterogeneous acid-mediated catalysis, especially for biodiesel production.