Production Characteristics of Volatiles from Anthracite Cracking via Microwave-Induced Discharge.

The ignition of anthracite with arc plasma has not been applied due to its low chemical effect and volatile content in anthracite. The nonequilibrium plasma generated by a microwave-induced discharge has the ability to break branch chains and aromatic ring structures by kinetic effects, which has the potential for anthracite cracking and ignition. This work investigated anthracite cracking by microwave-induced discharges under an Ar/N2 atmosphere. Results showed that the maximum levels of CO production, total gas production, and total gas generation rate occur in 20% argon content due to an increase in the number of electrons and a decrease in the total electronic states excitation rate constant with an increase in the argon content. The total gas production in plasma cracking is larger than that by pyrolysis, indicating the crack of polycyclic aromatic hydrocarbon by plasma. In addition, we attempted anthracite combustion under an 80% N2 and 20% O2 atmosphere.

Heat and mass transfer simulation of the microwave-assisted toluene desorption for activated carbons regeneration.

The low cost and high efficiency of microwave-assisted regeneration render it a viable alternative to conventional regeneration methods. To enhance the regeneration performance, we developed a coupled electromagnetic, heat, and mass transfer model to investigate the heat and mass transfer mechanisms of activated carbon during microwave-assisted regeneration. Simulation results demonstrated that the toluene desorption process is governed by temperature distribution. Changing the input power and flow rate can promote the intensity of hot spots and adjust their distribution, respectively, thereby accelerating toluene desorption, inhibiting readsorption, and promoting regeneration efficiency. Ultimately, controlling the input power and flow rate can flexibly adjust toluene emissions to satisfy the processing demands of desorbed toluene. Taken together, this study provides a comprehensive understanding of the heat and mass transfer mechanisms of microwave-assisted regeneration and insights into adsorbent regeneration.

Release Pattern of Light Aromatic Hydrocarbons during the Biomass Roasting Process.

Roasting is an important step in the pretreatment of biomass upgrading. Roasting can improve the fuel quality of biomass, reduce the O/C and H/C ratios in the biomass, and provide the biomass with a fuel quality comparable to that of lignite. Therefore, studying the structure and component evolution laws during biomass roasting treatment is important for the rational and efficient utilization of biomass. When the roasting temperature is 200-300 °C, the cellulose and hemicellulose in the biomass undergo a depolymerization reaction, releasing many monocyclic aromatic hydrocarbons with high reactivity. The proportion of monocyclic aromatic hydrocarbons in biomass roasting products can be effectively regulated by controlling the reaction temperature, residence time, catalyst, baking atmosphere, and other factors in the biomass roasting process. This paper focuses on the dissociation law of organic components in the pretreatment process of biomass roasting.

Elucidating the impact of oxygen functional groups on the catalytic activity of M-N4-C catalysts for the oxygen reduction reaction: a density functional theory and machine learning approach.

Efforts to enhance the efficiency of electrocatalysts for the oxygen reduction reaction (ORR) in energy conversion and storage devices present formidable challenges. In this endeavor, M-N4-C single-atom catalysts (MN4) have emerged as promising candidates due to their precise atomic structure and adaptable electronic properties. However, MN4 catalysts inherently introduce oxygen functional groups (OGs), intricately influencing the catalytic process and complicating the identification of active sites. This study employs advanced density functional theory (DFT) calculations to investigate the profound influence of OGs on ORR catalysis within MN4 catalysts (referred to as OGs@MN4, where M represents Fe or Co). We established the following activity order for the 2eORR: for OGs@CoN4: OH@CoN4 > CoN4 > CHO@CoN4 > C-O-C@CoN4 > COC@CoN4 > COOH@CoN4 > CO@CoN4; for OGs@FeN4: COC@FeN4 > CO@FeN4 > OH@FeN4 > FeN4 > COOH@FeN4 > CHO@FeN4 > C-O-C@FeN4. Multiple oxygen combinations were constructed and found to be the true origin of MN4 activity (for instance, the overpotential of 2OH@CoN4 as low as 0.07 V). Furthermore, we explored the performance of the OGs@MN4 system through charge and d-band center analysis, revealing the limitations of previous electron-withdrawing/donating strategies. Machine learning analysis, including GBR, GPR, and LINER models, effectively guides the prediction of catalyst performance (with an R2 value of 0.93 for predicting ΔG*OOH_vac in the GBR model). The Eg descriptor was identified as the primary factor characterizing ΔG*OOH_vac (accounting for 62.8%; OGs@CoN4: R2 = 0.9077, OGs@FeN4: R2 = 0.7781). This study unveils the significant impact of OGs on MN4 catalysts and pioneers design and synthesis criteria rooted in Eg. These innovative findings provide valuable insights into understanding the origins of catalytic activity and guiding the design of carbon-based single-atom catalysts, appealing to a broad audience interested in energy conversion technologies and materials science.

Activity origin of boron doped carbon cluster for thermal catalytic oxidation: Coupling effects of dopants and edges.

Catalytic oxidation plays important roles in energy conversion and environment protection. Boron-doped crystalline carbocatalyst has been demonstrated effective; however, the application potential of boron-doped amorphous carbocatalyst remains to be explored. For amorphous carbon material, finite-sized carbon clusters are the basic structural units, which exhibit unique activity due to edge and size effect. Herein, using sulfur dioxide (SO2) and carbon monoxide (CO) oxidation as probe thermal-catalysis reactions, we found the distribution and reactivity of active sites in boron-doped carbon clusters are simultaneously determined by dopants and edges. According to comparisons of oxygen (O2) chemisorption energy at different sites of symmetric and non-symmetric carbon cluster, the most active site is found to be the edge carbon atom with high electron donation ability, which can be accurately identified by electrophilic Fukui function. More importantly, the reactivity of boron-doped cluster is simultaneously influenced by doping configuration and the type of edge, based on which -O-B-O- configuration embedded into K-region edge (isolated carbon-carbon double bonds that do not belong to Clar sextet) is predicted to exhibit the highest reactivity among various boron doping configurations. This work clarifies unique activity origin of heteroatom-doped amorphous carbon materials, providing new insights into designing high-performance carbocatalysts.

Janus graphite felt cathode dramatically enhance the H2O2 yield from O2 electroreduction by the hydrophilicity-hydrophobicity regulation.

Hydrogen peroxide (H2O2) electrosynthesis from 2-electron O2 reduction reaction (2eORR) is widely regarded as a promising alternative to the current industry-dominant anthraquinone process. Design and fabrication of effective, low-cost carbon-based electrodes is one of the priorities. Many previous work well confirmed that hydrophilic carbon-based electrodes are preferable for 2eORR. Here, we proposed a strategy of hydrophilicity-hydrophobicity regulation. By using commercially available graphite felt (GF) as electrodes, we showed that both hydrophilic GF, hydrophobic GF, and Janus GF yielded significantly higher H2O2 production, which is 7.3 times, 7.6 times, and 7.7 times higher than the original GF, respectively. Results showed that currents and stirring rates affect the H2O2 yields. The enhancement of hydrophilic GF is due to the incorporation of oxygen-containing functional groups, while the hydrophobic and Janus GF comes from the locally confined O2 bubbles, which built a gas-liquid-solid interface inside GF and thus enhance the H2O2 formation kinetics. Finally, the effectiveness of the hydrophilicity-hydrophobicity regulation concept was tested in Electro-Fenton process by removing typical dyes and antibiotics. This work supply an effective but facile strategy to enhance the performance of carbon-based electrodes towards 2eORR by regulating the micro-environment of electrodes.

Broadening the pore size of coal-based activated carbon via a washing-free chem-physical activation method for high-capacity dye adsorption.

Aiming to overcome the limitations of the narrow pore size distributions of traditional activated carbon materials and to achieve wide adaptabilities towards large molecules adsorption, we herein demonstrate a new type of activated carbon with a broadened pore size distribution for high-rate and high-capacity aqueous dye molecule (Rhodamine B) adsorption. The preparation of CP-AC is achieved by a facile and one-step mineral-assisted chem-physical activation strategy from Chinese large-reserve Zhundong coal with ZnCl2 and CO2 as the activation agents. The method yields the activated carbon (CP-AC) that has a pore-size broadened hierarchical pore configuration with a high surface area and a large pore volume, favorably enabling a high-capacity Rhodamine B adsorption up to 881 mg g-1, which is among the highest levels of the reported activated carbons. A sonication-assisted adsorption test further demonstrates the high-rate adsorption capability of CP-AC with Rhodamine B adsorption capacity up to 842 mg g-1 within 30 min (96% of the saturation capacity) while microporous activated carbon obtained by solely ZnCl2 activation could just achieve a capacity of 374 mg g-1 within 30 min. In virtue of the low-cost resource materials and washing-free craft, this work offers a simple and green preparation strategy towards high-performance coal based activated carbons, holding great potentials for the industrial production and applications.

Introducing catalytic gasification into chemical activation for the conversion of natural coal into hierarchically porous carbons with broadened pore size for enhanced supercapacitive utilization.

Focusing on engineering the pore structure of porous carbons for enhanced supercapacitive performances, a new type of coal derived hierarchically porous carbon which is synthesized by introducing a catalytic gasification mechanism into an often-utilized chemical activation process is demonstrated. Such a strategy skillfully employs the catalytic effects of the minerals in natural coal on the etching reaction between CO2 molecules and carbon framework, which easily widen the pore size of well-developed micropores, thereby yielding a hierarchical pore configuration with simultaneously high surface area, large pore volume as well as broadened pore size distribution. The enhanced pore development mechanism is elucidated by a series of control experiments and thermogravimetric analysis. Evaluated as supercapacitor electrode materials, the resulting HPC exhibits state-of-the-art supercapacitive performances in both aqueous and non-aqueous electrolytes, particularly the superior rate capabilities, which highlights the favorable role of broadened pore configuration in facilitating electrolyte ion transfer and storage. Combining with the naturally abundant carbon resource and easily-implemented preparation craft, the as-obtained coal transferred hierarchically porous carbons hold great potentials for industrial production and supercapacitor applications.

Combustion characteristics of particles of hazardous solid waste mixtures in a fixed bed.

Hazardous waste disposal is vitally important as industrial production increases. Grate furnaces are a common means to incinerate hazardous waste. In this present work, a fixed bed assembly is used to experimentally model combustion within grate furnaces. Combustion characteristics are examined and the effects of primary air rate, moisture, bed height and particle size on burning rate, ignition-front speed and temperatures in the bed are also investigated. The results indicate that a rising temperature front descends through the bed while weight loss remains constant during the main combustion stage. Primary air rates and moisture content are shown to have significant effects on burning rates and average ignition-front speeds. Bed height has no effect on burning rates but does have an effect on average ignition-front speeds. Particle size is found to have slight effects on burning rates while having no effect on average ignition-front speeds.

TG-FTIR characterization of pyrolysis of waste mixtures of paint and tar slag.

Safe disposal of hazardous waste is becoming generally more important as industrial production increases. The pyrolysis characteristics and gas evolution of mixtures of several wastes are discussed in this paper. Experiments are described for various heating rates, particle sizes and final temperatures using thermogravimetric analysis (TGA) and a Fourier transform infrared spectrometer. The results indicate that there are three stages in the pyrolysis process. The composition of evolved gas includes carbon monoxide, carbon dioxide, ammonia, methane, nitric oxide, hydrocyanic acid and a number of other light alkanes. Gas evolution temperatures and gas generation rates were significantly influenced by the factors identified.

Combustion characteristics and NO formation for biomass blends in a 35-ton-per-hour travelling grate utility boiler.

Measurements were taken for a 35-ton-per-hour biomass-fired travelling grate boiler. Local mean concentrations of O(2), CO, SO(2) and NO gas species and gas temperatures were determined in the region above the grate. For a 28-ton-per-hour load, the mass ratios of biomass fly ash and boiler slag were 42% and 58%, the boiler efficiency was 81.56%, and the concentrations of NO(x) and SO(2) at 6% O(2) were 257 and 84 mg/m(3). For an 18-ton-per-hour load, the fuel burning zone was nearer to the inlet than it was for the 28-ton-per-hour load, and the contents of CO and NO in the fuel burning zone above the grate were lower.

Kinetic study of corn straw pyrolysis: comparison of two different three-pseudocomponent models.

With heating rates of 20, 50 and 100 K min(-1), the thermal decomposition of corn straw samples (corn stalks skins, corn stalks cores, corn bracts and corn leaves) were studied using thermogravimetric analysis. The maximum pyrolysis rates increased with the heating rate increasing and the temperature at the peak pyrolysis rate also increased. Assuming the addition of three independent parallel reactions, corresponding to three pseudocomponents linked to the hemicellulose, cellulose and lignin, two different three-pseudocomponent models were used to simulate the corn straw pyrolysis. Model parameters of pyrolysis were given. It was found that the three-pseudocomponent model with n-order kinetics was more accurate than the model with first-order kinetics at most cases. It showed that the model with n-order kinetics was more accurate to describe the pyrolysis of the hemicellulose.

Combustion characteristics of different parts of corn straw and NO formation in a fixed bed.

Experiments with five samples of corn straw were carried out on a one-dimensional bench combustion test rig. The bed temperature distribution and the mass loss of fuel and gas components such as O2, CO, CO2 and NO were measured in the bed. The combustion of corn straw occurred in two stages, ignition front propagation and char oxidation. The average burning rate increased with an increase in the primary air flow until a critical point was reached, beyond which a further increase in the primary air flow resulted in a decreased burning rate. The mean concentration of NO reached a minimum value and then increased with increased primary air flow. The time taken for the drying front to reach the bottom of the bed was 800 s, 700 s, and 500 s; the temperatures in the high bed temperature zones were 900-935 degrees C, 800-850 degrees C and 700-743 degrees C; and the maximum concentrations of NO were 725 ppmv, 1287 ppmv, and 2730 ppmv, for whole corn stalks, hollow corn stalks and flaked corn stalks, respectively. The maximum concentrations of CO and NO were quite different between samples. There was only one peak in the distribution of NO concentration for sample B, but there were two peaks for whole corn stalks and sample A.