Preparation of novel carbonaceous solid acids from rice husk and phenol

We reported a simple protocol to prepare a novel carbonaceous solid acid (CSA) with SiO2 from a mixture of rice husk and phenol by using small amount of sulfuric acid while stirring and heating for dehydration, sulfonation and carbonation at 240 °C for 2 h. It was found that adding phenol was vital for enhancing properties of the obtained CSA, and the CSA was efficient and recyclable catalyst for production of biodiesel, with the conversion of oleic acid reaching 94.3% at 65 °C for 4 h. Moreover, the conversion still was 90.2% after the CSA had been used five times.