Heterogeneous basic catalysis for upgrading of biofuels

• Deoxygenation of methyl octanoate was achieved over sodium low silica X zeolite.
• KNaX and CsNaX increase the selectivity to C6 and C7 hydrocarbons.
• The impregnation with cesium hydroxide improves the selectivity to desired products.
• Generation of hydrogen in situ has significant influence in the product distribution.

The liquid product (biofuel) obtained from biomass pyrolysis has a very complex composition that consists of a mixture of different organic compounds. This mixture presents a high content of oxygenated groups (aldehydes, acids, esters, etc.) that reduce the quality of the biofuel. The deoxygenation of these biofuels improves their quality, reducing the viscosity, increasing the calorific value and improving their thermal stability. In this sense, the deoxygenation of methyl octanoate was carried out over different catalysts with basic properties such as FAU zeolites, SBA-15 ordered mesoporous silicate and clays like sepiolite and hydrolacite. Enhancement of its basic properties was carried out by ion-exchange and/or by impregnation with CsOH. Among these catalysts only over X zeolite was obtained good activity and selectivities to the desired products (C6, C7 and C8 hydrocarbons), especially over the ones with low silicon/aluminum molar ratio. The decrease of the electronegativity of the exchangeable cation in the X zeolite (KNaX1 and CsNaX1) allowed to improve the selectivity to C6 and C7 hydrocarbons (60%). Furthermore, the presence of cesium hydroxide (10 wt%) on the zeolite (CsI-NaX1) produced significant conversion of methyl octanoate (70%) with high selectivity to alkenes (53%) reaching a desired/undesired product ratio of 7.3.

Figure optionsDownload high-quality image (130 K)Download as PowerPoint slide