Biomass & Bioenergy最新文献

The selective hydrogenolysis of lignin offers a promising avenue for converting lignin into valuable chemicals and fuels. However, the development of highly active catalysts for this process remains challenging. In this study, a series of Ni_x/Al₂O₃ catalysts were synthesized by calcining and reducing layered double hydroxides (LDHs) precursors. These catalysts were evaluated for their effectiveness in catalyzing the conversion of lignin-derived model compounds (2-phenoxy-1-phenylethanol and diphenyl ether). Remarkably, the optimized Ni₃/Al₂O₃ catalyst demonstrated exceptional performance in cleaving C–O bonds, achieving complete conversion with high selectivity for monomers product under reaction conditions of 200 °C, 1 MPa H₂, and 1 h. The catalyst's outstanding performance can be attributed to its relatively large specific surface area, Ni loading exceeding 50 wt%, well-dispersed Ni metal particles, abundant surface oxygen vacancies, and a significant number of acid sites. Additionally, the hydrogenolysis of lignin using the Ni₃/Al₂O₃ catalyst resulted in a substantial production of monophenols (15.0 wt%). This study introduces a novel approach for tailoring highly active Ni nanocatalysts and highlights the capability of Ni_x/Al₂O₃ catalysts to efficiently cleave C–O bonds in lignin under mild reaction conditions.

Interest in production and utilization of 5-hydroxymethylfurfural (5-HMF) has risen greatly as 5-HMF is considered as an extremely important platform compound. It remains a huge challenge to develop efficient and low-cost solid catalysts with suitable acid properties for sustainable production of 5-HMF from glucose. Herein, a bifunctional Sn-modified SBA-15 (Sn–OH/SBA-15) catalyst containing both Lewis and Brønsted acid sites was fabricated. Dimethyldichlorostannane was grafted onto mesoporous SBA-15, and the methyl groups were then converted to hydroxyl groups by calcination. The synergistic effects of Lewis and Brønsted acid significantly boosted the synthesis of 5-HMF from glucose adopting the one-pot method. By optimizing the reaction conditions, the Sn–OH/SBA-15 sample was able to achieve a glucose conversion of 96.9% with a 5-HMF yield of 70.6% (180 °C, 5 h). Moreover, the catalyst demonstrated superior recyclability and reusability. This work would enlighten the exploitation and preparation of highly efficient catalysts for the transformation of carbohydrates into value-added chemicals.

Numerous active sites and hierarchical pore structures are important for improving catalytic performance for the oxygen reduction reaction (ORR). In this work, a series of iron-nitrogen-doped porous carbon materials (Fe–N–C) with ORR catalytic activity were prepared by a one-step pyrolysis method using enzymolytic lignin as the raw material, soy protein isolate and iron chloride as dopants. The results showed that the samples with the best performance have abundant Fe-Nx active sites and mesoporous structures. At the same time, the electrocatalytic results indicate that the half-wave potential of catalyst was 0.84 V, which reached 96.55% of commercial Pt/C catalysts (E_1/2 = 0.86 V), it still preserves an initial current density of 92%, after 10,000 s of circulation, which is much better than Pt/C (86%). Due to the low cost, high activity and stable ORR property, the prepared non-precious metal electrocatalyst will play an important role in the applications of fuel cells.

Citrus limetta or sweet lime is a widely consumed fruit worldwide. The wastes generated from their processing are enormous and are discarded without any value-addition. Biomass liquefaction in hydrogen-donor solvent is an effective thermochemical conversion technique to produce value added products such as biocrude and biochar from wet biomasses directly. Thus, liquefaction studies of Citrus limetta peel and pulp were conducted using solvent methanol at temperatures of 240 °C–280 °C, 30 min residence time as well as 1:2, 1:3 and 1:4 ratios of biomass to solvent. The impact of temperature as well as biomass to solvent ratio on yield of biocrude and biochar were investigated herein. Biocrude produced from Citrus limetta peel at 240 °C and 1:3 ratio of biomass to solvent is maximum (12.5 wt. %). At reaction parameters of 280 °C and 1:4 ratio of biomass to solvent, biocrude from Citrus limetta pulp showed higher heating value of 27.18 MJ kg⁻¹ which was the maximum obtained in this study. The gas-chromatography mass-spectrometry (GC-MS) indicated presence of alcohols, phenols, alkanes, ketones, ethers, esters and fatty acid methyl esters as major compounds. The characteristics and energy content of biochar demonstrated their potentiality for bioenergy applications.

Biomass is the only carbon-neutral fuel, the development and utilization of biomass are crucial for achieving carbon neutrality. However, the combustion of biomass in boilers is often unstable due to the heterogeneity of biomass raw materials, leading to a decrease in combustion efficiency and an increase in pollutant emissions. Continuous online monitoring is essential for the safe, stable and efficient operation of boilers. Traditional measurement methods typically rely off-line analysis to study the kinetics of biomass oxidation and pyrolysis. These methods struggle to accurately capture transient parameters during combustion due to changes in reaction pathways and oxidant products. Optical diagnosis is a non-contact, instantaneous and efficient method that can achieve in-situ, online and rapid measurement of multiple parameters. This technology has been extensively applied by researchers in the field of biomass combustion diagnosis. The current status and applications of online measurement methods for biomass ignition/combustion behavior and soot generation are reviewed. The problems and development trends of existing optical diagnostic technologies for biomass combustion are also been proposed. The review suggests that the future development of more diverse and effective optical diagnostic techniques, as well as the combination of various diagnostic technologies, is beneficial for comprehensively analyzing the key issues in biomass combustion, so as to realize the efficient utilization of biomass.

Anaerobic digestion is a promising approach to dispose of biodegradable waste and wastewater, generating biogas as an alternative energy resource. This work proposed a so-called M-CADM1 for continuous anaerobic digestion simulation, which combined the machine learning and anaerobic digestion model No.1 (ADM1). The detailed reaction path and intermediate products in different stages of anaerobic digestion are specified in ADM1. The kinetic parameters were modified by machine learning. The characteristics (elemental composition) of feedstocks were used to predict kinetic parameters. A total of 75 biomass samples were used to establish for machine learning models. Five element contents (C, H, O, N, S), feedstock feed rate, and anaerobic digestion temperature were used as the input. The kinetic parameters were set as output. The sensitivities of 17 kinetic parameters were evaluated. 7 kinetic parameters with the highest sensitivities were selected as ADM1 model inputs by sensitivity analysis. The R² and RMSE were used as the index to evaluated the accuracy of machine learning model. The best R² and RMSE reached 0.84 and 0.196. The TIC was used as the index to evaluated the accuracy of M-CADM1. By comparing the simulated value with the experimental value, the accuracy of the overall M-CADM1 expressed by TIC of kitchen waste was 0.036. The organic acid content and pH in the reactor were considered as indicators to study the accuracy and stability of the M-CADM1. Trends in organic acids, free ammonia or hydrogen inhibition, and pH were consistent with experimental continuous anaerobic digestion results.

The rising energy demand, coupled with increasing pollution and the depletion of fossil fuel reserves, has led to an urgent need for sustainable fuel alternatives like biodiesel. However, biodiesel production is not without its challenges, especially when using homogeneous catalysis, which often results in soap formation and high wastewater production. This review focuses on the use of heterogeneous base catalysts, particularly calcium oxide (CaO) doped with transition and non-transition metals, as a more efficient method for biodiesel production from various raw materials. The inclusion of transition and non-transition metal dopants in CaO catalysts plays a crucial role in enhancing their performance. These dopants significantly increase the surface area of the catalysts, leading to higher biodiesel yields (84.9–99.7%) and offering a marked improvement over traditional homogeneous catalysis methods. The study delves into the reaction mechanisms, thermodynamics, comparison of economic aspects of using heterogeneous and homogeneous catalysts, life cycle assessment (LCA), and practical implications of this study. It highlights that metal-doped heterogeneous catalysts are not only more efficient but also offer environmental benefits such as the emission of fewer pollutants and cost benefits due to reusability, ease of separation, and cheaper maintenance. In addition, future research should explore the untapped potential of new dopants and waste materials for developing cost-effective and sustainable catalysts. Investigating statistical methods and optimization models is crucial for finding optimal conditions for efficient biodiesel production.

Large amounts of produced water are extracted by the Oil and Gas energy sector since the industrial revolution. This available water, often salty, can be used to dilute liquid digestate from the anaerobic digestion process, a promising source of nutrients for microalgae cultivation. The study investigates the growth of halotolerant microalgae and their associated bacteria in column photobioreactors (PBRs) and open raceway pond (RWP), to treat industrial wastewaters while producing biomass for energy valorisation. Microalgae were cultured in mixtures of saline artificial produced water (7–44 %v/v), liquid digestate (5 %v/v using PBRs, 29–63 %v/v using RWP) and seawater. Nannochloropsis oceanica and Tetraselmis suecica strains were firstly cultivated in 70 L PBRs in indoor conditions for 3 months and later in 1.1 m³ RWP operated in outdoor conditions for 5 months in spring-summer period. In PBRs, average productivity was 9.0 ± 4.2 gVSS·m⁻²·d⁻¹ (102–153 mgVSS·L⁻¹·d⁻¹), with daily removal efficiencies for chemical oxygen demand, nitrogen and phosphorous up to 61.8, 31.6 and 97.2 %, respectively. In RWP, strong changes in the microalgae populations were observed. Productivity was 6.7 ± 5.2 gVSS·m⁻²·d⁻¹ (30 ± 23 mgVSS·L⁻¹·d⁻¹), with daily removal efficiencies for chemical oxygen demand, nitrogen and phosphorous up to 48.4, 44.4 and 88.1 %, respectively. In parallel with the production of microalgae, a nitrifying microbial population grew in the RWP despite the high salinity (70 g L⁻¹). Over these periods of several months, microalgae production was maintained using a culture medium containing high salt concentration, metals and harmful aromatic compounds.

Carbon dioxide methanation is a promising approach to convert captured CO₂ into green natural gas. Developing high performance biochar-supported nickel catalysts promotes a circular economy and the application of sustainable catalysts. Western red cedar biochar was produced via pyrolysis at 400, 500, and 600 °C and loaded with nickel via incipient wetness impregnation. Methanation was done at 400, 500, and 600 °C with the highest methane yield of 59% achieved at 500 °C with 10 wt.% Ni loading. This is comparable to a γ-Al₂O₃ supported catalyst prepared and tested similarly, which achieved a methane yield of 53%. Biochar-supported catalysts showed deactivation whereby methane yield decreased from 59% to 51% over 5 h, likely due to coking and/or the sintering of nickel. Various space velocities were tested, and results demonstrated that with a space velocity of 37.5 mL/g.min methane selectivity was 89% after 1 h on stream compared to methane selectivity of 42%, which was achieved at a space velocity of 112.5 mL/g.min. This shows that a much higher rate of deactivation is observed at higher space velocities. Increasing the nickel loading from 5 wt.% to 10 wt.% increased methane yield from 40% to 58% after 1 h on stream. The higher loading also showed significantly less deactivation. Future work focusing on the extent and impact of metal-support interactions and metal dispersion on catalytic performance and deactivation during CO₂ methanation is recommended.

In the present study, waste green and black tea leaves have been used to synthesize metal–free catalysts for hydrogen generation by ethanolysis of sodium borohydride by the acetic acid activation and carbonization. The FTIR, BET, SEM-EDS, and XPS characterizations have been performed to analyze the synthesized catalysts' properties. The parameters such as amounts of catalysts, SB, and reaction temperature were studied while performing the experiments. They were optimized using the Response Surface Methodology (RSM) to obtain the highest values of Hydrogen Generation Rates (HGR) of 1350 ml min⁻¹ g catalyst⁻¹ and 2700 ml min⁻¹ g catalyst⁻¹ using the acetic acid activated black tea (AA – BT) and acetic acid activated green tea (AA – GT) catalysts respectively with the activation energies of 13.14 kJ mol⁻¹ and 37 kJ mol⁻¹. The BET analysis has revealed that the AA – GT and AA – BT catalysts have surface areas of 22.96 m² g⁻¹ and 3.28 m² g⁻¹, pore diameters of 1.72 nm and 1.70 nm and pore volumes of 0.0047 and 0.0331785 m³ g⁻¹ respectively. The electrochemical analysis has revealed that the synthesized metal–free catalysts AA – BT and AA - GT possess good specific capacitances of 63.77 mF cm⁻² and 121 mF cm⁻², which shows that both can be used as electrode material for energy storage applications. Hence, it can be believed that both metal–free catalysts can act as dual functional materials, which can act as catalysts and energy storage materials.