A modelling study of acetylene oxidation and pyrolysis

This study initiates the gradual upgrade of the DLR reaction database The upgrade plan has two main steps: an optimisation of the C1–C4 oxidation chemistry and a revision of the polyaromatic hydrocarbon (PAH) formation sub-mechanism based thereupon. The present paper reports the main principles applied to model improvements and results obtained for the acetylene (C2H2) oxidation sub-mechanisms. The principle acetylene oxidation reactions have been revised as well as the detailed chemistry of important intermediates, i.e. methylene, ethynyl, vinylperoxy radical and also diacetylene, vinylacetylene and higher diacetylenes, important for PAH formation. The uncertainty intervals of the studied reactions were statistically evaluated, providing general bounds for the performed modifications to reaction rate coefficients. The first stage of the presented update was performed through revision of the thermochemical data and model optimisation on ignition delay data and laminar flame speed data, since they exhibit lower uncertainty in comparison to species profile data. The final model optimisation was obtained through simulations of concentration profiles measured in shock tubes and laminar flames for improvement of the reaction paths and rate coefficients related to acetylene pyrolysis and PAH precursor formation. Approximately 500 data points were analysed. The updated reaction mechanism predicts all simulated experimental data, also not included in the optimisation loop data prom plug flow and jet-stirred reactors, either with good or satisfactory agreement. It was found that the vinylperoxy radical formation and consumption dictate the reaction progress at low temperatures. The performed study clearly determined that acetylene combustion proceeds through the strongly coupled reaction paths of fuel oxidation and PAH precursor formation; the same species are involved in these parallel processes. Therefore, the self-consistent reaction model for acetylene combustion could be obtained only by an optimisation performed on the experimental dataset encompassing both processes

Modification of Biomass-Derived Nanoporous Carbon with Nickel Oxide Nanoparticles for Supercapacitor Application

Supercapacitors are one of the promising devices for the accumulation and storage of electrical energy. The purpose of this study is to develop a synthesis and modification method of carbon material to improve the electrochemical characteristics of a supercapacitor. In the proposed study, by varying the sequence and parameters of the processes of carbonization, mechanoactivation and thermochemical activation, the conditions for obtaining nanoporous carbon with a specific surface area of 2200 (±50) m2/g from walnut shells (WSs) are optimized. In addition, to increase the electrochemical efficiency of the electrode material, the resulting nanoporous carbon was modified with nickel oxide (NiO) nanoparticles by the thermochemical method. It is shown that the modification with nickel oxide nanoparticles makes it possible to increase the specific capacitance of the supercapacitor electrode by 16% compared to the original unmodified nanoporous carbon material

Preparation of Nanoporous Carbon from Rice Husk with Improved Textural Characteristics for Hydrogen Sorption

This study proposes a method to control the pore-forming process by performing preliminary mechanical activation of the initial rice husk before carbonization. Preliminary mechanical activation of the initial rice husk leads to the loosening of the intercellular substance and its partial depolymerization, thereby increasing the availability of its internal structure for pore formation during carbonization and chemical activation. Using the method described above, nanoporous carbon was obtained with a Brunauer–Emmett–Teller (BET)-calculated specific surface area of 2713 m2/g, a micropore specific surface area calculated by using the Dubinina–Radushkevich (D-R) method of 3099 m2/g, and a total pore volume calculated by using the Barett–Joyner–Halenda (BJH) method of 1.625 cm3/g. Due to these characteristics, the adsorption capacity in the obtained sample was for hydrogen 3.7 wt.% at a temperature of −190 °C and a pressure of 9 kgf/cm2, which is 29.7% higher than the adsorption capacity of nanoporous carbon obtained based on rice husk without mechanical activation. The composite “carbon–platinum” NC-2/Pt10%, at a temperature of 20 °C and a pressure of 9 kgf/cm2, showed an increase in sorption capacity of 27% compared to pure nanoporous carbon NC-2, which is explained by the emergence of the spillover effect