Design of novel order mesostructured superacid catalyst from rice husk for the conversion of linseed oil to methyl esters

Abstract

A novel ordered mesoporous catalyst was prepared from rice husk (MRH catalyst) through condensation–evaporation method in alkaline media. The process used cetyltrimethylammonium bromide (CTAB) as a structure-directing agent (template) and sulfonated biochar obtained from partial rice husk carbonization (SBRH) as precursor. Various parameters such as temperature and CTAB/SBRH mass ratios were investigated to improve the mesoporous structure. The chosen catalyst was based on its degree of order of the mesoporous channels, and its activity was also tested in the methanolysis of linseed oil to methyl esters which was considered as a valuable blending composition for commercial jet fuels. The results showed that the temperature and CTAB/SBRH mass ratio should be of 70 °C and 0.3/1, respectively. The catalyst samples were characterized by many techniques including X-ray diffraction (XRD), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ammonia-temperature programmed desorption (NH3-TPD). The methyl ester composition of the as-synthesized biofuel was determined using gas chromatography supported by mass spectroscopy detector (GC–MS). The results of the characterizations showed that the catalyst possessed superacidic sites (NH3-TPD) caused by –SO3H groups (confirmed by FT-IR analysis) and ordered mesoporous structure (XRD). The mesoporous channel distribution was also observed by TEM images. The methanolysis yield reached 93.5% (calculated through GC–MS analysis) at mild conditions with high purity of methyl ester products strongly proving the catalyst activity and selectivity.