Stage Of Reaction Research Articles

Changes in the state of matter of KCIO4 to improve thermal and combustion properties of Al/MoO3 nanothermite

To improve the thermal and combustion properties of nanothermites, a design theory of changing the state of matter and structural state of the reactants during reaction was proposed. The Al/MoO3/KClO4 (Kp) nanothermite was prepared and the Al/MoO3 nanothermite was used as a control. SEM and XRD were used to characterize the nanothermites; DSC was used to test thermal properties; and constant volume and open combustion tests were performed to examine their combustion performance. Phase and morphology characterization of the combustion products were performed to reveal the mechanism of the aluminothermic reaction. The results show that the Al/MoO3/Kp nanothermite exhibited excellent thermal properties, with a total heat release of 1976 J·g− 1, increasing by approximately 33% of 1486 J·g− 1 of the Al/MoO3 nanothermite, and activation energy of 269.66 kJ·mol− 1, which demonstrated higher stability than the Al/MoO3 nanothermite (205.64 kJ·mol− 1). During the combustion test, the peak pressure of the Al/MoO3/Kp nanothermite was 0.751 MPa, and the average pressure rise rate was 25.03 MPa·s− 1, much higher than 0.188 MPa and 6.27 MPa·s− 1 of the Al/MoO3 nanothermite. The combustion products of Al/MoO3 nanothermite were Al2O3, MoO, and Mo, indicating insufficient combustion and incomplete reaction, whereas, the combustion products of Al/MoO3/Kp nanothermite were Al2O3, MoO, and KCl, indicating complete reaction. Their “coral-like” morphology was the effect of reactants solidifying after melting during the combustion process. The characterization of reactants and pressure test during combustion reveals the three stages of aluminothermic reaction in thermites. The excellent thermal and combustion performance of Al/MoO3/Kp nanothermite is attributed to the melt and decomposition of Kp into O2 in the third stage. This study provides new ideas and guidance for the design of high-performance nanothermites.

Demineralization effects on physicochemical and combustion characteristics of biomass: Insights into distributed kinetics, flue gas evolution, and slag formation

Biomass as the only carbon-bearing renewable energy has enormous potential to challenge the established energy structure dominated by fossil resources, and incineration technology is one of the most direct and efficient pathways for utilizing biomass resources, unfortunately enduring the inevitable sintering and slagging problems owing to the excessive alkali metals. Herein, we comparatively investigated the effects of five leaching solvents (water, acetic acid, wood vinegar, hydrochloric acid, and oxalic acid) on the physicochemical properties and ash-removal capabilities of wheat straw (WS) and rice husk (RH), with a view to achieving better performance in the subsequent combustion characteristics, kinetic examination, flue gas, and slag evolution. Results indicated with ionization ability increased (water < acetic acid < hydrochloric acid), the WS exhibited a strong demineralization performance (maximum 61.1%), further leading to a steep weight loss in its combustion characteristic curve at approximately 350 °C and a delayed peak temperature after the removal of alkali metal. Multiple distributed activation energy model and sensitivity analysis revealed that leaching pretreatment enhanced the activation energy (189–191.8 kJ mol−1) and optimized energy distribution at the preliminary stage of the combustion reaction. In addition, the absence of alkali metals suppressed the catalytic oxidation reaction in the flue gas, remarkably limiting the formation of CO2 but facilitating the release of CO and CH4. Meanwhile, a considerable optimal in biomass ash slagging, in which the initial temperature of the liquid phase slag for WS ash increased to 991 °C. Notably, HCl showed the strongest demineralization performance among the five leaching solvents during pretreatment, but the high-temperature slag content was still higher than that of acetic acid. Therefore, slagging performance is not only associated with the demineralization ability of leaching solvents, but also with ash composition.

Design of earth-abundant Ni3ZnC0.7@Ni@C catalyst for selective butadiene hydrogenation

The pursuit of developing catalysts from earth-abundant materials to supplant those based on precious metals is of paramount importance in selective hydrogenations. While nickel-based systems have shown promise in the selective hydrogenation of butadiene, their practical applications are hampered by severe deactivation issues due to coke deposition and excessive hydrogenation. Here, a novel catalyst, Ni3ZnC0.7@Ni@C, is ingeniously engineered through the controlled oxidation of Ni3ZnC0.7@C. This catalyst is characterized by small Ni0 ensembles elegantly embellishing the Ni3ZnC0.7 nanoparticles, all encased within porous carbon shells. The evolutions of this catalyst, in terms of composition and structure during the oxidation process, is meticulously observed and characterized using a spectrum of advanced techniques. The Ni3ZnC0.7@Ni@C catalyst exhibits outstanding activity and stability in the hydrogenation of butadiene, surpassing other Ni-based systems, including its precursor Ni3ZnC0.7@C and other previously documented catalysts such as Ni3InC0.5 and the Ni3In alloy. A pivotal finding of this research is the self-limiting behavior of coke deposition in the initial reaction stages. This intriguing phenomenon not only curbs further deactivation but also significantly enhances butene production, maintaining operational stability for an impressive duration of 80 hours. This discovery underscores the advantageous role of in situ generated ‘soft’ cokes in augmenting the selectivity and stability of the catalyst, which is particularly enlightening for other catalytic processes that are similarly afflicted by coking issues, thereby opening avenues for further in-depth investigations in this field.

Metabolite Profiling Reveals the Dynamic Changes in Non-Volatiles and Volatiles during the Enzymatic-Catalyzed Processing of Aijiao Oolong Tea.

The enzymatic reaction stage (ECS) of oolong tea processing plays an important role in the formation of the flavor quality of the oolong tea. To investigate the dynamic changes in the volatile and non-volatile components in the leaves of oolong tea during the ECS, metabolomic studies were carried out using the leaf samples collected at different stages of the ECS of Aijiao oolong tea. Out of the identified 306 non-volatile metabolites and 85 volatile metabolites, 159 non-volatile metabolites and 42 volatile metabolites were screened out as key differential metabolites for dynamic changes during the ECS. A multivariate statistical analysis on the key differential metabolites showed that the accumulations of most metabolites exhibited dynamic changes, while some amino acids, nucleosides, and organic acids accumulated significantly after turning-over treatment. The evolution characteristics of 27 key precursors or transformed VOCs during the ECS of Aijiao oolong tea were clarified, and it was found that the synthesis of aroma substances was mainly concentrated in lipids as precursors and glycosides as precursor pathways. The results revealed the dynamic changes in the flavor metabolites in the ECS during the processing of Aijiao oolong tea, which provided valuable information for the formation of the characteristic flavor of Aijiao oolong tea.

Decarbonisation of high-temperature endothermic chemical reaction processes using a novel turbomachine: robustness of the concept to feed variability

This paper presents a revolutionary turbomachinery concept, referred to as the turbo-reactor, which has the potential to replace gas-fired radiant furnaces and decarbonise a wide range of hard-to-abate, high-temperature endothermic chemical reaction processes. Although previous studies by the authors have confirmed the feasibility of using a turbo-reactor for steam cracking reactions, the numerical investigation presented in this work broadens the scope of potential applications for the machine to a variety of energy-intensive chemical processes, including those used for hydrogen production. This step change in technology could be the catalyst needed to enable rapid scale-up of low-carbon hydrogen technology. The innovative design of the turbo-reactor is fundamentally based on converting all of the imparted mechanical energy into internal energy, rather than pressure. This enables temperatures of up to 1,700°C to be achieved within an axial length on the order of one metre, resulting in an increase in the power density of 50 to 1,000 times compared to a surface heat exchanger. This paper presents the first comprehensive analysis of the turbo-reactor’s robustness and controllability across a broad spectrum of feeds, chemical reaction stages, Mach number regimes, and operating points, conclusively demonstrating the feasibility of a universal stage design strategy for repeatedly imparting and dissipating energy for various endothermic reaction processes.

Gas-liquid-soild triphasic continuous flow microreactor for improving homogeneous distribution of solid composites in heterogeneous photocatalytic degradation progress

The homogeneous distribution of solid composites in continuous flow photocatalytic progress is difficult due to the settle and clog in capillary. To overcome this challenge, a gas–liquid-soild triphasic continuous flow photoreactor was designed and used for heterogeneous photocatalytic degradation of antibiotics wastewater. In this work, take Bi2WO6 as photocatalyst, photocatalytic degradation of ofloxacin wastewater was studied systematically under different operational parameters and flow characteristics. The photocatalytic degradation performance of flow photoreactor was superior to batch counterpart, especially in later stage of reaction. The apparent reaction rate constants (k) of flow photoreactor was about 1.6 times that of batch counterpart. The gas–liquid mass transfer coefficient of flow photoreactor was more than 25 times that of batch photoreactor. Moreover, the influence mechanism of gas fraction, flow rate and tube diameter on photocatalytic degradation performance was investigated under various continuous flow conditions. Higher gas fraction, faster flow rate and smaller tube diameter were beneficial to improve photocatalytic degradation performance due to the enhancement of irradiation transmission and intensification of mass transfer. Therefore, the results of this work provided a guideline for the application of gas–liquid-soild triphasic continuous flow photocatalytic degradation technology in the future.

Early age structural build-up and pore stability in raw foam at ambient conditions: Implications for the final properties of glass-ceramic foam

Alkali activation followed by foaming techniques is an effective method for glass-ceramic foam development where early-age reactions in the alkali-activated precursors and the foaming reaction happen simultaneously. Therefore, this early reaction stage must be clearly understood to control the pore characteristic in the glass-ceramic foams. However, correlations between early-age structural build-up and foaming stability and their consequences on the final properties of the sintered glass-ceramic foams have not been investigated. This research aims to examine this relationship. 80–95 wt % of waste glass and 5–20 wt % of slag were used as alkali-activated precursors in this research. Using the alkali activation and combined foaming technique, the raw glass foam was developed and hardened at ambient conditions. The early-age reactivity and structural build-up of the binder and foamed suspension were studied through the rheological parameter and chemical structure analysis over the hardening period. During the hardening process, the percolation effect and development of reaction gels contribute to network formation and stability of the foamed suspension. As the hardening time increases, the matrix strengthens, and the pores stabilise through crosslinking of the gels. After hardening, the raw glass foams were sintered and their properties were evaluated and correlated with early-age structural build-up in fresh glass foam. This study demonstrates that the early-age interaction during matrix development and the foaming process controls the pore stability, connected pore volume, and strength of the final glass-ceramic foams. By understanding these parameters, the properties and pore stability in final glass-ceramic foams can be controlled effectively.

The exploration of relationship between the evolution of Cu to Cu2O/CuO and photocatalytic efficiency toward water oxidation reaction

This paper introduces a facile method to develop core-shell nanocomposite Cu/(Cu2O/CuO) through gradually oxidation on Cu nanocomposite precursors. As-prepared catalyst exhibited excellent catalytic activity in the reaction of water oxidation reaction (WOR). Comparing with the reported catalyst, Cu/(Cu2O/CuO) posed one of the highest O2 evolution around 7700 μmol g-1·h-1. By analyzing the composition of catalysts in each reaction stages, the evolution pathway of Cu towards Cu2O/CuO and the different roles of each component in catalytic water oxidation reactions were deeply studied. In presence of high conductive Cu element and excellent light absorption Cu2O, the photo generated electron and holes can be effectively separated and greatly improve the efficiency of the catalyst. The evolution process and synergistic effects of the three components play a crucial role in improving photocatalytic efficiency, which promoting the nanocomposite to be a highly efficient core-shell catalyst for WOR.

Kinetic Study of Pure Oxygen Combustion of Coke Blended with Calcium Oxide

ABSTRACT In order to elucidate the mechanism of CaO on pure oxygen combustion of coke, non-isothermal TGA technique was use to test coke blended CaO samples of varying C/Ca molar ratios (CMCa-2, CMCa-3, and CMCa-4). The characteristic combustion temperatures at varying β were measured. The representative CMCa-2 and CMCa-4 were tested by TG-MS to determine the effect of CaO on coke combustion. Kinetics parameters for the blended samples across various reaction phases were determined using the improved Coats-Redfern method. The results showed that in the pure oxygen atmosphere, the combustion characteristic temperature rise with the increase of β. The material transformations during different reaction stages proceeded as follows: coke combustion generated CO2, CO2 combined with CaO to generate CaCO3, and finally CaCO3 decomposed to release CO2. The E values of three reaction stages were as follows: the highest E was observed in stage 3, ranging from 128.05–151.18 kJ·mol−1, the lowest E in stage 2 was below 46 kJ·mol−1, and the E in stage 1 laid between 99.35–128.71 kJ·mol−1. The C/Ca molar ratio was proportional to the kinetic parameters of the blended sample.

The Influence of Quartz Powder on the Mechanical–Thermal–Chemical–Durability Properties of Cement-Based Materials

Using industrial by-products to replace cement is an important way to reduce carbon emissions in the cement industry. The purpose of this article is to understand the effect of quartz powder on the properties of cement-based materials. Experimental studies were conducted on the macroscopic and microscopic properties of cement-based materials mixed with quartz powder to evaluate their feasibility as a replacement for cement. The substitution rates of quartz powder were 0% (Qu0), 7.5% (Qu7.5), and 15% (Qu15). The test time was from 1 day to 28 days, and the main results are as follows: In the early stage of the hydration reaction, as the amount of quartz powder substitution increases, the cumulative hydration heat increases. This is mainly because the nucleation effect of quartz powder accelerates the hydration reaction of cement. In the later stage of the hydration reaction, as the amount of quartz powder substitution increases, the cumulative heat of hydration decreases. This is mainly due to the diluting effect of quartz powder. For Qu0, Qu7.5, and Qu15, the decrease in compressive strength after 1 day is not obvious. The decrease in compressive strength at 28 days is more obvious. Overall, there are exponential relationships between the UPV measurement or surface resistivity results and the compressive strength measurement results at 1, 3, 7, and 28 days. The XRD test results show that the main products of the reaction are AFt, CH, Hc, and Mc. From Day 1 to Day 28, the content of Mc becomes evident. The test results for TG showed that, as the amount of quartz powder substitution increases, the mass loss decreases. For different specimens of Qu0, Qu7.5, and Qu15 at different test times (3 and 28 days), there is an exponential function relationship between chemically bound water and strength. A numerical hydration model is proposed for cement–quartz binary blends. The parameters of the hydration model are determined based on the hydration heat normalized by the cement mass. Moreover, the hydration heat at 28 days is calculated using the proposed model. The strength development of all specimens and all test ages can be expressed as an exponential function of hydration heat.

CO and O2 Interaction with Kinked Pt Surfaces.

We investigate the chemical interaction of carbon monoxide (CO) and oxygen (O2) with kink atoms on steps of platinum crystal surfaces using a specially designed Pt curved sample. We aim at describing the fundamental stages of the CO oxidation reaction, i.e., CO-covered/poisoned stage and O-covered/active stage, at the poorly known kinked Pt facets by probing CO uptake/saturation and O2 saturation, respectively. Based on the systematic analysis that the curved surface allows, and using high-resolution X-ray photoemission, a diversity of terrace and step/kink species are straightforwardly identified and accurately quantified, defining a smooth structural and chemical variation across different crystal planes. In the CO-saturated case, we observe a preferential adsorption at step edges, where the CO coverage reaches a CO molecule per step Pt atom, significantly higher than their close-packed analogous steps with straight terrace termination. For the O-saturated surface, a significantly higher O coverage is observed in kinked planes compared to the Pt(111) surface. While the strong adsorption of CO at the kinked edges points toward a higher ignition temperature of the CO oxidation at kinks as compared to terraces, the large O coverage at steps may lead to an increased reactivity of kinked surfaces during the active stage of the CO oxidation.

Effect of Ce2O3 phase transition on the catalytic oxidation for toluene over CeO2 catalysts

Cerium oxide was a potential replacement for precious metals as a catalyst for VOCs. Here, we prepared CeOx-350, CeOx-450, CeOx-550 and CeOx-650 catalysts by controlling the calcination temperature, the occurrence of Ce2O3 localized phase transitions at CeOx-350 and CeOx-550 was confirmed by XRD, HRTEM and TGA. This localized phase transition caused the change in specific surface area and crystallinity, and prolonged the Ce-O-Ce bond lengths at the heterogeneous interfaces, enhancing the redox capacity and activity of oxygen species. CeOx-550 exhibited the optimal low-temperature activity towards toluene due to the highest Ce3+ content, oxygen vacancy content and the best activity of reactive oxygen species. The oxidation of toluene experienced intermediates of benzyl alcohol, benzaldehyde, benzoate, maleic acid and carbonates. Among them, benzoic acid was the decisive step in the toluene oxidation pathway. Combined with the reaction pathway of toluene, the reaction stages of different oxygen species were determined. The active oxygen species located at the heterogeneous interface would serve as an adsorption site for toluene. The Ce2O3 phase would participate in the deep oxidation of toluene as an active site, which was equivalent to the oxygen vacancies. This study was conducted to explore the effect of local phase transition on catalytic activity, which provided a new strategy for the synthesis of highly active cerium oxide catalysts.

Composite LaNi0.6Fe0.4O3-δ - La0.9Sr0.1Sc0.9Co0.1O3-δ cathodes for proton conducting solid oxide fuel cells: Electrode kinetics study

Composite LaNi0.6Fe0.4O3-δ - La0.9Sr0.1Sc0.9Co0.1O3-δ (LNF-LSSCo) electrodes with the compositions 50/50, 60/40, and 80/20 wt% LNF/LSSCo are successfully applied for La0.9Sr0.1ScO3-δ proton conducting electrolyte. Electrochemical activity of the electrodes is studied by impedance spectroscopy, depending on temperature and oxygen partial pressure. The best performance is observed for 60/40 LNF/LSSCo electrodes. Detailed analysis of impedance data is performed using non-linear least squares and distribution of relaxation times methods taking into account the shunt effect of electronic conductivity of La0.9Sr0.1ScO3-δ electrolyte. Two main rate-determining stages of the electrode reaction are determined, which are assigned to oxygen ion diffusion in the bulk of the electrode and oxygen interphase exchange with the gas phase. The application of the LNF current collector layer improves the electrochemical activity of the electrodes without changes in the electrode reaction mechanism, while the modification of the electrodes with Pr6O11 leads to a sufficient decrease in the resistance of the stage, corresponding to oxygen interphase exchange, resulting in a twice-improved electrochemical activity of the electrodes.

SYNTHESIS AND BIOLOGICAL ACTIVITIES OF ACETAMINOPHEN AND IBUPROFEN METAL COMPLEXES OR DERIVATIVES: A REVIEW

We reviewed scientific literature on the synthesis of acetaminophen and ibuprofen, as well as their derivatives and biological properties. The synthesis of acetaminophen involves the acetylation of 4-aminophenol and acetic anhydride, while ibuprofen is synthesised by reacting isobutyl benzene and acetic anhydride in four continuous reaction stages, which are Friedel-Crafts acylation, carbonyl reduction, chloride substitution, and Grignard reaction. To obtain their derivatives, modifications have been made either by complexing the main structure of the drug compound with metal elements or adding certain desired moieties, such as thiourea, amide, ammonium, halogen, silicon, and 1,3,4-oxadiazole. Ibuprofen and acetaminophen have been recognised as effective painkillers and anti-inflammatories. Recently, their derivatives have been implicated in a variety of biological effects. The biological activities of acetaminophen and ibuprofen derivatives have been reported to exhibit urease inhibition and inflammatory inhibition, as well as inhibit the proliferation of breast cancer cells MCF-7. Overall, this review article describes the synthesis of acetaminophen and ibuprofen derivatives, complete with their biological activities such as antimicrobial, antifungal, anti-inflammatory, urease inhibitors, and anticancer.

Heat storage and release characteristics of a prototype CaCO3/CaO thermochemical energy storage system based on a novel fluidized bed solar reactor

CaCO3/CaO thermochemical energy storage (TCES) system has a high heat storage density (1780 kJ/kg) along with high heat storage and release temperature (650–850 °C), which can be applied to concentrated solar power (CSP) technology utilizing CO2 Brayton cycles to improve power generation efficiency. There are several problems to be urgently resolved in current CaCO3/CaO solar calciners, such as poor heat and mass transfer and low thermochemical efficiency. This paper proposed a prototype CaCO3/CaO TCES system based on a novel fluidized bed solar reactor, which has a serrated arc surface in alignment with the direction of the incident solar rays to receive concentrated solar energy. The natural limestone particles were used as the reactive particles. The effects of operating modes (intermittent/continuous), initial mass of reactive particles, and initial carbonation temperature Tcar,initial on the heat storage and release characteristics of the TCES system were experimentally explored. During the carbonation reaction stage, the effective carbonation degrees in the continuous mode were generally higher than in the intermittent mode under the experimental conditions and declined at a slower rate. The reactive particles were recovered from the reactor for microstructural characterization after completing the experiments, high-temperature particle agglomeration and pore structure clogging were directly responsible for the decrease of the effective carbonation degree. In the continuous mode, the average thermochemical and total thermal efficiencies of 24.7 % and 53.5 % were obtained in the 1st calcination reaction, respectively, which represents significant advantages over other CaCO3/CaO solar calciners. The novel fluidized bed reactor demonstrated excellent fluidization in the experiments and did not exhibit mechanical deformation after multiple experiments under non-uniform concentrated radiation provided by an 84 kWe high-flux solar simulator. Overall, this paper provides a successful gas-solid reactor design to be coupled with CSP technology.

Physics-informed data-driven model of dehydration reaction stage in the sintering process of ternary cathode materials

The sintering process is the main process that affects the performance of ternary cathode materials. Due to the closed, continuous, and long-term characteristics of the sintering process carried out in a roller kiln, the reaction state including reaction degree, particle size, and etc., of the raw materials cannot be directly obtained through sampling detection, resulting in ineffective temperature control. This article mainly focuses on modeling the dehydration reaction stage of the sintering process to obtain the reaction state of the raw materials. Firstly, a two-sphere model is established based on Newton’s second law and the particle volume conservation equation to describe the relationship between the particle radius and sintering temperature of lithium hydroxide and ternary precursor; Secondly, the chemical kinetic parameters of the dehydration reaction in the two-sphere model are obtained by combining the single heating rate scanning method with the multiple heating rate scanning method; Then, in order to improve the accuracy of the two-sphere model and reduce the impact of external environmental temperature changes, a physics-informed neural network model is constructed by combining the two-sphere model with the neural ordinary differential equation model. Finally, the effectiveness of the modeling method is verified through numerical simulation and empirical data.

Effect of Hyperthermal Hybrid Gas Composition on the Interfacial Oxidation and Nitridation Mechanisms of Graphene Sheet.

Graphene is one of the most promising thermal protection materials for high-speed aircraft due to its lightweight and excellent thermophysical properties. At high Mach numbers, the extremely high postshock temperature would dissociate the surrounding air into a mixture of atomic and molecular components in a highly thermochemical nonequilibrium state, which greatly affects the subsequent thermal chemical reactions of the graphene interface. Through establishing a reactive gas-solid interface model, the reactive molecular dynamics method is employed in this study to reveal the influences of the thermochemical nonequilibrium gas mixture on the thermal oxidation and nitridation mechanisms of graphene sheet. The results show that three distinctive stages can be recognized during bombardment of various nonequilibrium gas components toward the graphene sheet: (i) collision and surface adsorption stage, (ii) gas-solid heterogeneous reaction stage, and (iii) gas phase homogeneous reaction stage. The surface catalysis effect is found to be dominant during the first two stages, which can influence the following ablation behavior of graphene significantly at high-temperature conditions. Moreover, surface catalysis, oxidation, nitridation, and ablation mechanisms between nonequilibrium gas and graphene interface are revealed, which is of high relevance for future interfacial design and application of graphene as a thermal protection material.

A more appropriate way to optimize the hybrid reactive-extractive distillation system

Existing studies on reactive-extractive distillation (RED) commonly misapply optimization variables by including reaction stages. Given the uncatalyzed nature of ethylene oxide (EO) hydration in RED, where it naturally occurs throughout the column, a more appropriate strategy is to optimize only the total stages, allowing the reactive stage to align accordingly. However, previous attempts to implement this approach faced challenges. Here we introduce an algorithm addressing the variable overlap issue in optimizing RED, exemplified in two case studies. In Case 1, we explored a distinct scenario where the original process designated a specific reaction zone. Adjustments were made to ensure the reaction occurred throughout the entire column but it leads to a 13 % total annual cost (TAC) increase compared to the base case. In Case 2, optimization was applied to a system where reaction were distributed throughout the column without prior optimization, yielding a marginal 3.87 % reduction in the TAC.

Modelling and Design of a Novel Integrated Heat Exchange Reactor for Oxy-Fuel Combustion Flue Gas Deoxygenation

The concentration of residual O2 in oxy-fuel combustion flue gas needs to be reduced before CO2 transportation, utilization, or storage. An original application of the printed circuit heat exchanger (PCHE) for catalytic combustion with natural gas (catalytic deoxygenation) is described for reducing the residual O2 concentration. The PCHE design features multiple adiabatic packed beds with interstage cooling and fuel injection, allowing precise control over the reaction extent and temperature within each reaction stage through the manipulation of fuel and utility flow rates. This work describes the design of a PCHE for methane–oxygen catalytic combustion where the catalyst loading is minimized while reducing the O2 concentration from 3 vol% to 100 ppmv, considering a maximum adiabatic temperature rise of 50 °C per stage. Each PCHE design differs by the number of reaction stages and its individual bed lengths. As part of the design process, a one-dimensional transient reduced-order reactor model (1D ROM) was developed and compared to temperature and species concentration axial profiles from 3D CFD simulations. The final design consists of five reaction stages and four heat exchanger sections, providing a PCHE length of 1.09 m at a processing rate of 12.3 kg/s flue gas per m3 PCHE.

Unravelling the reaction mechanism for the AP decomposition over MgO: A density functional theory study and microkinetic simulation

The detailed reaction mechanisms for the decomposition of ammonium perchlorate (AP), an essential component of solid composite propellants, are poorly understood due to the ultrafast and complex reactions. Density functional theory and kinetic simulation are utilized to calculate the decomposition reaction of AP on the surface of magnesium oxide and present a detailed decomposition network. Using a proton transfer mechanism, NH3 and HClO4 are the major production at low-temperature decomposition of AP, involving two elementary steps. AP is completely decomposed in the high-temperature reaction stage. In this work, it is found that the decomposition of NH3 is mainly in the form of oxidative dehydrogenation, while HClO4 proceeds along the pathway HClO4→ClO3→ClO2→ClO→Cl, and the final nitrogen oxides, chlorine oxides are formed. These simulations provide offer atomic-level understanding of the complex reaction kinetics of AP, which can be applied to explore the reaction mechanisms of other metal oxides.