Liquefaction of lignite with a Ru/C catalyst in supercritical ethanol

Abstract

High moisture content materials present challenges for direct liquefaction. We herein report an effective way to liquefy high moisture content feedstocks in supercritical ethanol with a Ru/C catalyst. The Ru/C catalyst converts some of the ethanol into hydrogen through steam reforming. Additional hydrogen is produced by the water gas shift reaction. During this process, water is converted into gaseous products. Compared to the case with no added catalyst, use of Ru/C suppressed solid residues, improved hydrogen yields, and improved the quality of the oil fraction. Oil quality was improved by enhancing production of long chain alkanes (LCAs), and suppressing production of phenols and polycyclic aromatic hydrocarbons (PAHs). The effects of reaction temperature and time on the product distribution and composition were also investigated. Higher temperatures favored gasification. The maximum oil yield, 6.4 wt%, and minimum solid residue yield, 0.9 wt% (calculated by oil or solid/the mass of ethanol and lignite), were obtained at 400 °C and 60 min reaction time with an ethanol/lignite (E : L) ratio of 9 : 1, and 50 wt% catalyst loading relative to lignite. The dominant compounds in the oil were LCAs, esters, and phenols. The major gaseous products were CH₄, H₂, and CO.