Coal pyrolysis to acetylene in thermal plasma provides a direct route to make chemicals from coal resources, where the rapid heating and release of volatile matters in coal particles play the dominant role in the overall reactor performance. A mechanism model incorporating the heat conduction in solid materials, diffusion of released volatile gases, and reactions was proposed for a deep understanding of the heat transport inside a coal particle under extreme environmental conditions such as high temperatures greater than 2000 K and milliseconds of reaction time. The two competing rates model, known as the Kobayashi model, was applied to describe the devolatilization kinetics, which was verified by comparing the predicted yield of volatiles with the experimental data in the literature. Thermal balance between coal particles and the hot carrier gas was established, and the four influencing factors including the heating rate, particle size, reactants flow ratio, and heat of devolatilization were paid attention when analyzing the heating profile inside the particles and the yield of volatiles. The results showed that the inherent resistance due to the volatiles released from coal particles seriously impeded the thermal energy transportation from heating gas to the particle. This led to a weakened heating rate, i.e., a long heating up time, and thereafter a low yield of volatiles, especially when the particle size was large (e.g., >40 μm). Meanwhile, the heat conduction inside the coal particle also imposed additional resistance to reduce the heat transportation rate from heating gas to the particle, especially when the particle size was larger than 80 μm. The predicted yield of volatiles considering the mechanism of the two resistances agreed reasonably with the reported experimental data under different operating conditions but was smaller than that which could be obtained when neither resistance is considered. It can be concluded that the proposed heat transport mechanism inside coal particles works well in understanding the coal pyrolysis process at ultrahigh temperatures.
Chemical recycling of plastic waste could reduce its environmental impact and create a more sustainable society. Hydrogenolysis is a viable method for polyolefin valorization but typically requires high hydrogen pressures to minimize methane production. Here, we circumvent this stringent requirement using dilute RuPt alloy to suppress the undesired terminal C–C scission under hydrogen-lean conditions. Spectroscopic studies reveal that PE adsorption takes place on both Ru and Pt sites, yet the C–C bond cleavage proceeds faster on Ru site, which helps avoid successive terminal scission of the in situ-generated reactive intermediates due to the lack of a neighboring Ru site. Different from previous research, this method of suppressing methane generation is independent of H2 pressure, and PE can be converted to fuels and waxes/lubricant base oils with only <3.2% methane even under ambient H2 pressure. This advantage would allow the integration of distributed, low-pressure hydrogen sources into the upstream of PE hydrogenolysis and provide a feasible solution to decentralized plastic upcycling. Hydrogenolysis of waste polyolefins often produces excessive methane under low hydrogen pressure. Here, by using a dilute RuPt alloy, the authors successfully prevent sequential C–C bond cleavage, enabling flexible use of various hydrogen sources for localized plastic recycling.
The widespread application of electrochemical hydrogen production faces significant challenges, primarily attributed to the high overpotential of the oxygen evolution reaction (OER) in conventional water electrolysis. To address this issue, an effective strategy involves substituting OER with the value-added oxidation of biomass feedstock, reducing the energy requirements for electrochemical hydrogen production while simultaneously upgrading the biomass. Herein, we introduce an electrocatalytic approach for the value-added oxidation of isobutanol, a high energy density bio-fuel, coupled with hydrogen production. This approach offers a sustainable route to produce the valuable fine chemical isobutyric acid under mild condition. The electrodeposited Ni(OH)
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