Search

Under the circumstances of serious environmental challenges and energy crises, it is of utmost importance to produce fuels and chemicals from renewable biomass and organic wastes. Biochar as a bioproduct from thermochemical conversion of biomass has attracted exponential research interest in recent years due to the abundance of its precursor (biomass resources) and its adaptability in different chemical reaction systems. Undoubtedly, it is essential to attain an in-depth understanding of the physiochemical properties and functionalization of biochar catalysts to further improve their catalytic activity, selectivity and stability in the reactions. However, until now, only a few reports are accessible on the use of biochar as a catalytic support material and/or a standalone catalyst in thermochemical biomass conversion to produce high-quality biofuels. Thus, the key objective of this review article is to summarize and discuss the latest progress in biochar production, modification, activation and functionalization by understanding its physical chemistry, composition and application in catalytic processes. This review article provides insights into the thermochemical and hydrothermal production of biochar as well as the engineering and process optimization aspects for value-added biofuel production and decarbonization. [Display omitted] • Effects of biomass composition and process conditions on biochar are reviewed. • Systematic discussion on biochar functionality as bio-based catalyst support is made. • Insights into the modification of biochar targeting optimal performance are shown. • Comparative analysis of biochar-based catalytic pyrolysis, gasification and liquefaction. • The significance of activation of biochar for enhanced functionality is justified. [ABSTRACT FROM AUTHOR]

Direct carbon solid oxide fuel cells (DC-SOFCs) demonstrate significant promise in clean energy conversion technology due to their direct utilization of solid carbon, high-temperature operation, and fuel flexibility. Exploring biomass as a fuel for DC-SOFCs is particularly intriguing within this context. Here, we successfully developed the biochar derived from tomato straw and conducted a comprehensive physicochemical characterization to investigate its feasibility and advantages for DC-SOFCs. Electrochemical results revealed that DC-SOFC powered by tomato straw biochar achieved an impressive output of 219 mW cm−2 at 850 °C, surpassing the cell output of 187 mW cm−2 operating on commercial activated carbon. Furthermore, the single cell demonstrated a higher discharge plateau and a longer lifetime of 26.5 h under 50 mA at 850 °C. Consequently, fuel utilization was calculated to be up to 29.7%, which was also superior to that of activated carbon-fueled DC-SOFC, further validating the effectiveness of tomato straw biochar in improving DC-SOFC performance. These outstanding performances were primarily attributed to the unique porous microstructure, naturally existing metal elements, high disorder and large specific surface area of the biochar, which effectively promoted the reverse Boudouard reaction to produce a substantial amount of CO for anode reaction, thus enhancing the DC-SOFC performance and efficiency. These findings underscore the enormous application potential of tomato straw biochar for DC-SOFCs, providing strong support for advancing clean energy technology and achieving carbon neutrality goals. [Display omitted] • Tomato straw biochar is successfully developed as an alternative fuel for DC-SOFCs. • The biochar exhibits excellent physicochemical properties for carbon gasification. • Biochar-fueled DC-SOFC achieves an impressive output of 219 mW cm−2 at 850 °C. • The cell operates stably for 26.5 h at 50 mA with a high fuel utilization of 29.7%. [ABSTRACT FROM AUTHOR]

Reusable, solid acid carbon supported catalysts were generated from biomass by pyrolysis (400–500°C) to generate a soft to hard carbon backbone (i.e., biochar) for addition of acidic functional groups. Acid catalysts were synthesized by sulfonating the biochar and wood derived activated carbon using concentrated H2SO4 at 100, 150 and 200°C (12h) and gaseous SO3 (23°C). Attenuated Total Reflectance, sulfur, and NH3-TPD analysis of the sulfonated carbons indicated the presence of SO3H groups on the 100°C sulfonated biochar and activated carbon (AC), with higher active site densities (SO3H density) for the SO3 sulfonated material. The sulfonated carbons were tested for their ability to esterify free fatty acids with methanol in blends with vegetable oil and animal fat (5–15wt.% FFA). Esterification of the fatty acids was typically complete (∼90–100% conversion) within 30–60min at 55–60°C (large methanol excess), but decreased with lower methanol to oil ratios using the biochar catalysts (e.g., 70%, 6h, 20:1). Solid acid catalysts derived from wood based activated carbon had significantly higher activity compared to the biochar derived catalysts (e.g., 97%, 6h, 6:1). Of the synthesized biochar catalysts, 400 °C pyrolyzedpine chip biochar, sulfonated at 100°C, resulted in the highest reaction rate and lowest reduction in conversion (or deactivation) when reused multiple times. Drying the biochar catalysts for 1h at 125°C between uses maintained esterification activity, allowing the catalysts to be reused up to 7 cycles. For the SO3 sulfonated AC catalyst, such a regeneration step was not required, as the fractional conversion of palmitic and stearic acid (5% FFA, 10:1, 3h) remained >90% after 6 cycles. [Copyright &y& Elsevier]