Synergistic Hydrothermal Conversion of Aqueous Solutions of CO₂ and Biomass Waste Liquefaction into Formate

Abstract

CO 2 utilization by conversion into useful chemicals can contribute to facing the problem of increasing CO 2 emissions. Among other alternatives, hydrothermal transformation stands out by the high conversions achieved, just using hightemperature water as the solvent. Previous works have demonstrated that several organic compounds with hydroxyl groups derived from biomass can be used as reductants of NaHCO 3 aqueous solutions as inorganic CO 2 sources. Formate was obtained as the main product as it was produced by conversion both of the inorganic carbon and of the organic reductants, whose transformation into formate was promoted by the addition of NaHCO 3 . Based on these results, in this work, the hydrothermal conversion of NaHCO 3 is performed together with the liquefaction of lignocellulosic biomass (sugarcane bagasse and pine needles) in a one-pot process. Results show that yields to formate of 10% wt/wt (with respect to the initial concentration of biomass) are achieved by hydrothermal treatment of NaHCO 3 and lignocellulosic biomass at 250 °C with a residence time of 180 min. Other products, such as acetic acid and lactic acid, were also obtained. These results demonstrate the feasibility of the hydrothermal reduction of CO 2 combined with the hydrothermal liquefaction of residual biomass in a simultaneous process.

Long-Chain Hydrocarbons from Nonthermal Plasma-Driven Biogas Upcycling

“…Because H 2 O is the only source of proton in this situation, produced formic acid (<2.5 ppm) and H 2 (∼1%) is comparatively limited. The production of formic acid from CO 2 in the thermal catalytic system is well established, as corroborated by the research of He et al, Quintana-Gómez et al, and Andérez-Fernández et al…”

“…Because H 2 O is the only source of proton in this situation, produced formic acid (<2.5 ppm) and H 2 (∼1%) is comparatively limited. The production of formic acid from CO 2 in the thermal catalytic system is well established, as corroborated by the research of He et al, 12 Quintana-Goḿez et al, 13 and Andeŕez-Fernańdez et al 14 In contrast, the presence of CH 4 in the feed exerts a significant influence on the production of alcoholic products and acetic acid. Methanol and ethanol are found to reach the highest concentration when 25% CO 2 is present, with approximately 40 and 41 ppm, respectively.…”

Effect of Alkali‐ and Alkaline‐Earth‐Metal Promoters on Silica‐Supported Co−Fe Alloy for Autocatalytic CO2 Fixation

“…This value was even higher (72 mM) when H 2 accounted for 60 % of the gas phase, meaning that the formate concentration is highly hydrogen dependent. [38] At this point, we could observe a quantifiable concentration of acetate (up to 0.17 mM) in both hydrogen-added experiments, which is higher than the value detected in LCHF. [37] A control reaction of H 2 (1 mmol) and CO 2 (8.8 g) without CoFe/SiO 2 did not show any products, meaning that CoÀ Fe acts as not only a reductant but also a catalyst.…”

Thermodynamic modelling of mixtures of water, carbon dioxide and hydrogen at high pressure and temperature for hydrothermal CO2 reduction processes

“…Figure 3 presents the results obtained at different pressures and temperatures, considering a fixed initial concentration of NaHCO 3 of 0.5 mol/kg in the dissolution (matching the conditions used in experimental works, in which the aqueous CO 2 solution was prepared dissolving this concentration of sodium bicarbonate in water [18,19]) and a fixed hydrogen partial pressure of 20 bar. The range of conditions analyzed comprised temperatures ranging from 300 K to 500 K and CO 2 partial pressures in the gas of 20 bar, 50 bar, 75 bar and 125 bar.…”

“…The hydrothermal reduction process can be carried out either using gaseous hydrogen as reductant, or using water itself as hydrogen source; in the second case, an additional reductant to promote the decomposition of water into hydrogen and oxygen, such as a metal [16,17] or an organic reductant [18,19], must be provided. Typically, formic acid is the main product yielded by this process [12,18], but several products can be obtained from carbon dioxide under hydrothermal reduction using metal reductants and catalysts.…”