Premium biofuels from straw – production of advanced biofuels using the Sylvan process

Abstract

The increasing demand for transportation fuels, especially middle distillates, stimulates the research of new strategies to obtain or synthesize biofuels. The processing of lignocellulosic biomass (for example straw) is a process of great interest, because after its hydrolysis and subsequent dehydration of the resulting sugar monomers, very valuable substances including furfural are obtained. Then, furfural is selectively hydrogenated to 2-methylfuran, sylvan, that is the basic “building block” in the Sylvan process. This manuscript summarizes the knowledge on Sylvan process as a promising way of biofuels synthesis. By sylvan condensing with aldehydes, ketones or even 2-methylfuran itself, it is possible to prepare C13-C16 oxygenates in high yields up to 100 % under mild reaction conditions (30 - 60 °C) over various heterogeneous catalysts. Based on the overview, the heterogeneous catalysts are preferred and the immobilized sulfonic acids are the most active catalysts, however, expensive. The reaction products then may be hydrodeoxygenated commonly over supported noble metal catalysts to provide premium quality C13-C16 hydrocarbons to produce diesel or kerosene. These fractions have great low-temperature properties such as CFPP (-50 °C) or cetane number (70-72). According to the proposed sustainability prediction, this process could be sustainable in the Czech Republic, where 30 % of produced wheat straw could be used for the production of 130 kt advanced biofuels by Sylvan process required by EU directive RED II. Finally, the future approaches have been suggested.