Hydrothermal Co-Liquefaction of Lignite and Lignocellulosic Biomass with the Addition of Formic Acid: Study on Product Distribution, Characteristics, and Synergistic Effects

Abstract

Hydrothermal co-liquefaction of lignite (L) and lignocellulosic biomass represented by cornstalk (CS) and pinewood sawdust (PW) was investigated in this work under various conditions in the presence of formic acid (FA) as an in situ hydrogen donor. The effects of experimental parameters on product distribution and especially the synergistic interaction between lignite and biomass were studied in detail. The results indicated that oil production was significantly enhanced by the addition of FA, while the oil yields obtained from co-liquefaction of L/CS and L/PW reached 29.34 and 28.36 wt % under optimal conditions (350 °C, 30 min, lignite/biomass mass ratio = 1:1, with FA), respectively. The synergistic effects between lignite and biomass not only increased the oil yield but also promoted carbon and energy recovery in oil products. The produced oil products from co-liquefaction had similar boiling point fractions as those of the biomass-derived oil, and contained mainly hydrocarbons, phenols, and ketones, indicating that hydrothermal co-liquefaction of lignite and lignocellulosic biomass was beneficial for the production of oil products with high quality and diverse potential applications.

Physicochemical Characterisation and the Prospects of Biofuel Production from Rubberwood Sawdust and Sewage Sludge

“…46.94 MJ/kg), diesel (45.60 MJ/kg), and kerosene (45.99 MJ/kg), the HHV of RWS, SS, RWS50:SS50, and RWS75:SS25 was lower than that of petroleum feedstocks…”

“…However, it was lower than the LHV of petroleum feedstocks, such as natural gas (45.86 MJ/kg), gasoline (44.15 MJ/kg), diesel (42.91 MJ/kg), and kerosene (43.69 MJ/kg). As biofuel derived from biomass has a large quantity of impurities (chemical compounds) and a high O content, it causes corrosion and does not support direct engine ignition prior to upgrading, whereas lower grade biofuels can be used in boiler engines; however, this is an improvement on fossil fuels and is also considerably more environmentally friendly [46].…”

Biomass and Energy Production: Thermochemical Methods

“…The hydrothermal conversion process is a suitable technology especially for wet biomass into bio-fuel which is defined as a thermochemical transformation of biomass in high temperatures (100-700°C) and high pressures (5-40 MPa) in a liquid media or hot supercritical water [25]. In hydrothermal liquefaction (HTL) as an important hydrothermal process, raised temperatures (200-350°C) and high pressures (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) in the presence of solvent (sub−/super-critical water) applied to boost biomass decomposition and reformation to produce bio-crude (as the main output) bio-char, water-soluble organic polar fractions and gaseous [26][27][28]. During the HTL process, several complex mechanisms such as hydrolysis activate which degrade biomass macromolecules and then decompose them into smaller components to reactive fragments by bond cleavage and several reactions such as dehydration, dehydrogenation, deoxygenation, and decarboxylation while some complex chemicals such as bio-crude produce through depolymerization [29][30][31].…”

“…Biomass is clean renewable energy that accumulates and transfers sun energy in the form of chemical energy during the growth of plants and trees through the photosynthesis process [11]. Therefore, biomass has been recognized as one of the renewable energy sources, with carbon capture capability and carbon neutrality [12][13][14]. In this context as it is shown in Figure 1, biomass also demonstrates the capability of transformation of the accumulated energy into multiple general forms of final energy carries such as solid, liquid, and gaseous which are compatible for various sectors comprising heat, power, and transport fuel [15].…”

Bio-Crude Production Improvement during Hydrothermal Liquefaction of Biopulp by Simultaneous Application of Alkali Catalysts and Aqueous Phase Recirculation

“…As a thermochemical technique, HTL offers a value-added bio-product with more than 75% of the heating value compared to conventional petroleum (HHV: 32 to 38 MJ/kg) and a relatively low oxygen content [11][12][13]. Sub-critical HTL can hydrothermally convert biopolymeric structures to hydrophobic compounds at 280-370 • C and 10 to 35 MPa [14,15]. This operational condition lowers the water dielectric constant and generates H + and OH -, which highlights the role of water as a suitable solvent and catalyst simultaneously [16].…”