Thermocatalytic Decomposition Research Articles

Highly pure hydrogen production via the thermocatalytic decomposition of methane over Ni/SiO2.MgO catalysts: Impact of the catalyst's chemical composition

The goal of current research is to focus on exploring the effects of various MgO/SiO2 ratios, emphasizing their impact on the structure properties and advancing the catalytic activity and the chemical life span of Ni-catalysts by an exciting mixture of SiO2 and MgO to generate COx-bare hydrogen and nanocarbon simultaneously from methane decomposition reactions. SiO2/MgO mixed oxides with different ratios (0.5, 1, and 2) were ready via a facile co-precipitation method from magnesium nitrate and sodium metasilicate and used as supports for various nickel contents (30, 40, 50, and 60 wt%) followed by an impregnation technique. Different analytical techniques, such as XRD, BET, SEM, EDS, H2-TPR, and TPO, were used to characterize the catalysts before and after the catalytic runs. The prepared catalysts with various SiO2/MgO molar ratios depicted the BET surface area limiting from 37.9 to 143.4 m2 g−1, indicating remarkable surface improvements. The vast CH4 conversion of 64 % earned on the 50 wt% Ni/SiO2·MgO at 575 °C. Moreover, lower deactivation was detected regarding this catalyst at 600 min on stream.

Metal-Catalyzed Thermo-Catalytic Decomposition and Continuous Catalyst Generation

In this study, metal dusting is utilized to initiate a two-stage thermo-catalytic decomposition (TCD) process. Stage 1 starts with metal-catalyzed TCD, and in stage 2 the metal-catalyzed carbon catalyzes additional TCD. TEM is presented of the early- versus late-stage TCD to qualitatively illustrate the second-stage TCD by the metal-catalyzed carbons. Corresponding SEM illustrates differences in growth type and surface density between early versus late reaction times, with backscattered imaging differentiating the first- versus second-stage TCD. TGA supports the microscopic inference of a second carbon phase by the presence of an early (low-temperature) reaction peak, characteristic of low-structure or disordered carbon as the second-stage TCD carbon. Raman analysis confirms that the second-stage carbon deposit is more disordered and unstructured, especially at 1000 °C, supported by the ID/IG and La value changes from 0.068 to 0.936 and 65 nm to 4.7 nm, respectively. To further confirm second-stage TCD occurrence upon pre-catalyzed carbons, two carbon blacks are tested. Exposing a combination of edge and basal or exclusively basal sites for the graphitized form, they afford a direct comparison of TCD carbon nanostructure dependence upon the initial carbon catalyst nanostructure. Pre-oxidation of the stainless-steel wool (SSW) prior to TCD is advantageous, accelerating TCD rates and increasing carbon yield relative to the nascent SSW for an equivalent reaction duration.

Mn/carbon aerogels derived from the water-induced self-assembly of UIO-66 (Mn) for the thermal decomposition of ammonium perchlorate.

In solid propellants, combustion catalysts play a crucial role. Here, we introduce a convenient method for the self-assembly of UIO-66 (Mn) in the presence of water, leading to the preparation of Mn/C aerogels. The aerogels were successfully utilized in the thermocatalytic decomposition of ammonium perchlorate (AP). The results indicate that the incorporation of 2% mass fraction of Mn/C aerogels enhances the peak temperature of AP decomposition by approximately 87.5°C. Mn/C aerogels demonstrate excellent catalytic performance. In combination with kinetics, we propose a thermal catalytic mechanism.

Effects of the ZrO2 Crystalline Phase and Morphology on the Thermocatalytic Decomposition of Dimethyl Methylphosphonate.

Thermocatalytic decomposition is an efficient purification technology that is potentially applicable to degrading chemical warfare agents and industrial toxic gases. In particular, ZrO2 has attracted attention as a catalyst for the thermocatalytic decomposition of dimethyl methylphosphonate (DMMP), which is a simulant of the nerve gas sarin. However, the influence of the crystal phase and morphology on the catalytic performance of ZrO2 requires further exploration. In this study, monoclinic- and tetragonal-phase ZrO2 (m- and t-ZrO2, respectively) with nanoparticle, flower-like shape and hollow microsphere morphologies were prepared via hydrothermal and solvothermal methods, and their thermocatalytic decomposition of DMMP was systematically investigated. For a given morphology, m-ZrO2 performed better than t-ZrO2. For a given crystalline phase, the morphology of hollow microspheres resulted in the longest protection time. The exhaust gases generated by the thermocatalytic decomposition of DMMP mainly comprised H2, CO2, H2O and CH3OH, and the by-products were phosphorus oxide species. Thus, the deactivation of ZrO2 was attributed to the deposition of these phosphorous oxide species on the catalyst surface. These results are expected to help guide the development of catalysts for the safe disposal of chemical warfare agents.

Thermocatalytic decomposition of methane to low-carbon hydrogen using LaNi1-xCuxO3 perovskite catalysts

The thermocatalytic decomposition (TCD) of methane is an attractive alternative to produce low-carbon hydrogen and solid carbonaceous materials. In this study, substituted LaNi1-xCuxO3 perovskite catalysts prepared via self-combustion method were investigated for methane TCD. The effect of Ni partial substitution with Cu, varying gas hourly space velocity, temperature and stability on methane conversions were evaluated. PXRD, H2-TPR, SEM-EDS, TGA, and XPS were used to characterize the catalysts. An increase in Cu loading to 50%, increase in temperature and decrease in GHSV resulted in an improvement in methane conversions to 92%. At a GHSV of 2400 ml/gcat.h, no significant deactivation was observed as the stability of the LaNi0.5Cu0.5O3 catalyst increased from 6 to 20 hours’ TOS with methane conversions maintained at 92% where carbon nanofibers were observed on the surface of the spent catalysts. The study demonstrates the potential to prepare LaNi1-xCuxO3 catalysts and identify optimal testing conditions for the novel production of low-carbon hydrogen with minimal catalyst deactivation.

Toward Rational Design of Nickel Catalysts for Thermocatalytic Decomposition of Methane for Carbon Dioxide‐Free Hydrogen and Value‐Added Carbon Co‐Product: A Review

AbstractThermocatalytic decomposition of methane provides opportunities for hydrogen (H2) production with no emission of carbon dioxide. However, high‐value carbon products need to be produced for economic deployment of thermocatalytic decomposition and to achieve a minimum H2 selling price below the U.S, Department of Energy target of $ 1/kg H2. In this review, we re‐evaluate data on catalyst development reported in the literature and propose correlations between catalyst characteristics, catalytic stability, and properties of carbon co‐products. In the first part of the review, growth mechanisms for carbon nanotubes using state‐of‐the‐art chemical vapor deposition are reviewed to catalog the effects of catalyst characteristics, the influence of carbon sources, interactions between metal particles and supports, and metal particle sizes on carbon growth. In the second part, representative developments in mono‐, bi‐, and tri‐metallic nickel catalysts are highlighted. We present kinetic analysis of reactions catalyzed by mono‐metallic nickel catalysts, which generates a correlation between metal particle size and catalyst stability. Rational design of Ni‐based catalysts for TCD of methane requires attention to the size of the metal particle and effective normalization of the reaction rates. Further attention to the distribution of the metal particle sizes may help identify catalyst properties that contribute longevity and selectivity to processes that use them. While it is tempting to focus on the highest valued carbon products (e. g., CNTs and CFs), analysis of the markets for other carbon products suggests that a more flexible approach may generate comparable returns without the risk associated with specialization.

Obtaining Hydrogen by Thermocatalytic Decomposition of Methane Using a Catalyst ‘Nickel on Kieselgur’

The process of hydrogen production through thermocatalytic decomposition of methane using a “nickel on kieselgur” catalyst on a quartz sand substrate with a thickness of 1 cm in the “sand-catalyst-sand” configuration was investigated in this work. The experimental results revealed a dependence of the percentage yield of hydrogen on temperature within the temperature range of 530°C to 770°C. As a result, a hydrogen content of 68% in the gas mixture was achieved at the reactor outlet under the conditions of 770°C temperature and a methane flow rate of 2 l/h.

Comparative analysis of a batch and continuous fluidized bed reactors for thermocatalytic decomposition of methane: A CFD-DEM-MGM approach

ThermoCatalytic Decomposition of methane (TCD) has shown great potential for synthesis of valuable carbon nanomaterials as well as hydrogen production, however due to the importance of the phenomena operating at different scales, it is a complex process to model and predict. During the TCD process methane is decomposed to hydrogen gas and solid carbon. Carbon is accumulated on the catalyst particle and leads to larger but less active catalyst particles. In this study, a Computational Fluid Dynamics-Discrete Element Method-Multi Grain Model (CFD-DEM-MGM) was employed to investigate two catalytic fluidized bed reactors for TCD with the same dimensions. Case-1 involved a batch of catalyst particles staying in the reactor during the process, while Case-2 featured a continuous reactor with removal of catalyst particles from the bottom and the introduction of fresh particles from the side. Results showed that the continuous reactor had lower catalyst particle growth and reduced deactivation due to limited residence time, yet demonstrated higher carbon production and gas conversion. Case-1, with larger catalyst particles, experienced reduced bubble formation, while in Case-2 the continuous removal/introduction of particles enhanced solids mixing. Internal diffusion limitations affected reactor performance, emphasizing the CFD-DEM-MGM model’s potential for optimizing fluidized bed reactor design and gas-solid contacting in the TCD process.

Thermo-catalytic decomposition of cotton seed press cake over nickel doped zeolite Y, hydrogen: enhanced yield of bio-oil with highly selective fuel-range hydrocarbons.

This research reports the yield of bio-oil from cotton seed press cake (CSPC) via an optimized thermo-catalytic pyrolysis using nickel impregnated zeolite Y, hydrogen catalyst. The catalyst, raw biomass and catalyst impregnated biomass were characterized using different analytical techniques. The ideal temperature, duration, and catalyst concentration for pyrolysis experiments were determined to be 300 °C, 20 minutes, and 5% of Ni-doped zeolite Y, hydrogen, respectively, in order to achieve the best bio-oil yield (35%). Gas chromatography-mass spectrometry (GC-MS) of pyrolytic bio-oil depicted the presence of C2-C26 hydrocarbons. The findings of this investigation showed that the synthesis of bio-oil with highly selective fuel-range hydrocarbons could be efficiently induced through the pyrolysis of CSPC biomass employing nickel impregnated zeolite Y, hydrogen catalyst. Moreover, thermogravimetric analysis (TGA) of cotton seed press cake with catalyst was carried out at various heating rates to find out the kinetic parameters. Employing Kissinger model, activation energy (E a) and frequency factor (A) for various components of biomass i.e., hemicellulose, cellulose and lignin were calculated as 83.14 kJ mol-1, 99.76 kJ mol-1, 124.71 kJ mol-1 and 1.9 × 107 min-1, 1.0 × 108 min-1, 1.0 × 1010 min-1, respectively. It can be concluded from the results that cotton seed press cake waste has potential for use as a pyrolysis feedstock in large-scale bio-fuel production.

Thermo-Catalytic Decomposition Comparisons: Carbon Catalyst Structure, Hydrocarbon Feed and Regeneration

Thermo-catalytic decomposition (TCD) activity and stability depend upon the initial carbon catalyst structure. However, further transitions in the carbon structure depend on the carbon material (structure and composition) originating from the TCD process. In this article, reaction data are presented that illustrates the time-dependent TCD activity as TCD-formed carbon contributes and then dominates conversion. A variety of initial carbon catalysts are compared, including sugar char, a conductive carbon black (AkzoNobel Ketjenblack), a rubber-grade carbon black (Cabot R250), and its graphitized analogue as formed and partially oxidized. Regeneration of carbon catalysts by partial oxidation is evaluated using nascent carbon black as a model, coupled with subsequent comparative TCD performance relative to the nascent, non-oxidized carbon black. Activation energies for TCD with nascent and oxidized carbons are evaluated by a leading-edge analysis method applied to TCD. Given the correlation between nanostructure and active sites, two additional carbons, engine soots, are evaluated for regeneration and dependence upon nanostructure. Active sites are quantified by oxygen chemisorption, followed by X-ray photoelectron spectroscopy (XPS). The structure of carbon catalysts is assessed pre- and post-TCD by high-resolution transmission electron microscopy (HRTEM). Last, energy dispersive X-ray analysis mapping (EDS) is carried out for its potential to visualize oxygen chemisorption.

Thermo-catalytic decomposition of walnut shells waste over cobalt doped cerium oxide: Impact of catalyst on kinetic parameters and composition of bio-oil

This research work is aimed at investigating the pyrolysis of walnut shells mixed with cobalt doped cerium oxide and non-catalytic pyrolysis of walnut shells. The pyrolysis experiments were performed in a locally designed pyrolysis chamber. The oils from catalytic and non-catalytic pyrolysis were characterized with GC–MS. It was found that in case of catalytic pyrolysis, the bio-oil obtained has several short-chain compounds as compared to bio-oil obtained through non-catalytic pyrolysis. Thermogravimetric analysis was conducted to assess the kinetics of pyrolysis of biomass both with and without catalyst. The kinetic parameters were determined using Kissinger equation. The activation energy (Ea) values for the decomposition of hemicelluloses, cellulose, and lignin were found as 167.72, 181.35, and 191.22 kJ mol−1 for non-catalytic pyrolysis and 107.48, 121.79, and 137.57 kJ mol−1 for catalytic pyrolysis. Moreover, the optimumtemperature of pyrolysis was effectively reduced to 410 °C employing a catalyst, as opposed to the maximum temperature of 430 °C in the case of non-catalytic pyrolysis. Keeping in view the reduction in activation energy and improvement in quality of oil from catalyzed reaction in presence of cobalt doped cerium oxide, it can be concluded that the findings of this study can contribute to the development of a process for sustainable utilization of walnut shells as energy source.

New Perspectives on Catalytic Hydrogen Production by the Reforming, Partial Oxidation and Decomposition of Methane and Biogas

The article provides a short review on catalyst-based processes for the production of hydrogen starting from methane, both of fossil origin and from sustainable processes. The three main paths of steam- and dry-reforming, partial oxidation and thermo-catalytic decomposition are briefly introduced and compared, above all with reference to the latest publications available and to new catalysts which obey the criteria of lower environmental impact and minimize the content of critical raw materials. The novel strategies based on chemical looping with CO2 utilization, membrane separation, electrical-assisted (plasma and microwave) processes, multistage reactors and catalyst patterning are also illustrated as the most promising perspective for CH4 reforming, especially on small and medium scale. Although these strategies should only be considered at a limited level of technological readiness, research on these topics, including catalyst development and process optimization, represents the crucial challenge for the scientific community.

Preparation of the NiO/FeAl2O4 nanopowders and their application in CH4 thermocatalytic decomposition to produce high purity of hydrogen: Optimization of the synthesis parameters using Taguchi design of experiment

The present research is centralized on designing and optimizing the preparation conditions of the NiO(50)/FeAl2O4 catalyst in the thermocatalytic decomposition of CH4 (TDM). The mesoporous FeAl2O4 powders were synthesized by various methods, and the supported nickel catalysts were employed in the TDM. The results showed that the catalyst supported on FeAl2O4 synthesized by the modified co-precipitation (MCOP) method possessed the best efficiency, and CH4 conversion and H2 yield were 74 and 82% at 675 °C, respectively. Taguchi L9 statistical experimental design was applied to investigate and optimize the preparation parameters, including surfactant type (CTAB, PVP, P123), pH (9, 10, 11), aging temperature (40, 60, and 80 °C), and aging time (0, 15, 30 h). The obtained outcomes revealed that the optimized sample displayed a mesoporous nanocrystalline structure with an appropriate BET area (72.6 m2 g−1) and pore volume (0.17 cm3 g−1), and its maximum methane conversion was 80.8% at 700 °C. The results indicated that the Taguchi procedure was impressive in the optimization of the synthesis parameters, and the error value between the predicted value and the actual value was lower than 4%. The physicochemical characteristics of the optimized sample were assessed based on the XRD, BET, H2-TPR, FTIR, TGA/DTA, FESEM, and TPO analyses. Furthermore, the influence of calcination temperature was investigated on the textural properties and catalytic performance of the selected catalyst. The stability experiment of the samples showed that the NiO(50)/FeAl2O4 catalyst calcined at 600 °C was utterly stable for 300 min time on stream. Also, the effect of the processing parameters (GHSV, feed composition, and reduction temperature) was evaluated on the catalyst stability and amount of the deposited carbon on the catalyst surface of the optimum NiO(50)/FeAl2O4 catalyst.

Thermocatalytic Decomposition of Methane: A Review on Carbon-Based Catalysts.

The global initiatives on sustainable and green energy resources as well as large methane reserves have encouraged more research to convert methane to hydrogen. Catalytic decomposition of methane (CDM) is one optimistic route to generate clean hydrogen and value-added carbon without the emission of harmful greenhouse gases, typically known as blue hydrogen. This Review begins with an attempt to understand fundamentals of a CDM process in terms of thermodynamics and the prerequisite characteristics of the catalyst materials. In-depth understanding of rate-determining steps of the heterogeneous catalytic reaction taking place over the catalyst surfaces is crucial for the development of novel catalysts and process conditions for a successful CDM process. The design of state-of-the-art catalysts through both computational and experimental optimizations is the need of hour, as it largely governs the economy of the process. Recent mono- and bimetallic supported and unsupported materials used in CDM process have been highlighted and classified based on their performances under specific reaction conditions, with an understanding of their advantages and limitations. Metal oxides and zeolites have shown interesting performance as support materials for Fe- and Ni-based catalysts, especially in the presence of promoters, by developing strong metal-support interactions or by enhancing the carbon diffusion rates. Carbonaceous catalysts exhibit lower conversions without metal active species and largely result in the formation of amorphous carbon. However, the stability of carbon catalysts is better than that of metal oxides at higher temperatures, and the overall performance depends on the operating conditions, catalyst properties, and reactor configurations. Although efforts to summarize the state-of-art have been reported in literature, they lack systematic analysis on the development of stable and commercially appealing CDM technology. In this work, carbon catalysts are seen as promising futuristic pathways for sustained H2 production and high yields of value-added carbon nanomaterials. The influence of the carbon source, particle size, surface area, and active sites on the activity of carbon materials as catalysts and support templates has been demonstrated. Additionally, the catalyst deactivation process has been discussed, and different regeneration techniques have been evaluated. Recent studies on theoretical models towards better performance have been summarized, and future prospects for novel CDM catalyst development have been recommended.

Ammonia Decomposition over Alkali Metal (Li, K, Cs)-Promoted Bulk Mo2N Catalyst

Ammonia (NH3), which has a 17.7 wt% gravimetric hydrogen density, has been considered as a potential hydrogen storage material. This study looked at the thermocatalytic decomposition of NH3 using a bulk Mo2N catalyst that was boosted by alkali metals (AM: 5 wt% Li, K, Cs). The K-Mo2N catalyst outperformed all other catalysts in this experiment in terms of catalytic performance. At 6000 h−1 GHSV, 100% conversion of NH3 was accomplished using the K-Mo2N, Cs-Mo2N, and Mo2N catalysts. However, when compared to other catalysts, K-Mo2N had the highest activity, or 80% NH3 conversion, at a lower temperature, or 550 °C. The catalytic activity exhibited the following trend for the rate of hydrogen production per unit surface area: K-Mo2N > Cs-Mo2N > Li-Mo2N > Mo2N. Up to 20 h of testing the K-Mo2N catalyst at 600 °C revealed no considerable deactivation.

Thermocatalytic Decomposition of Sesame Waste Biomass over Ni-Co-Doped MCM-41: Kinetics and Physicochemical Properties of the Bio-Oil

The increase in industrialization and development has tremendously diminished fossil fuel resources. Moreover, the excessive use of fossil fuels has resulted in the release of various toxic gases and an increase in global warming. Hence, necessitating the need to search for a renewable energy source. In this study, sesame waste biomass (SWB), which is abundantly available in Pakistan, has been used as feedstock for obtaining bio-oil using the pyrolysis technique. Pyrolysis was carried out using thermogravimetry and a pyrolysis chamber. Firstly, thermogravimetric analysis was performed on biomass with/without a laboratory synthesized catalyst Ni/Co/MCM-41 in nitrogen at different temperature programmed rates of 5, 10, 15, and 20 °C/min. A four-stage weight loss was observed that pointed toward the vaporization of water, and degradation of hemicelluloses, cellulose, and lignin. The kinetics parameters were determined using the Kissinger equation. The activation energy for the decomposition reaction of hemicelluloses, cellulose, and lignin, without catalyst, was observed as 133.02, 141.33, and 191.22 kJ/mol, respectively, however, with catalyst it was found as 91.45, 99.76, and 149.65 kJ/mol, respectively. In the catalyzed reaction the results showed the lowest activation energy, which is an indication of the fact that the catalyst is successful in reducing the activation energy to a sufficient level. As the TG/DTG showed active degradation between 200 and 400 °C, therefore, the waste sesame biomass over Ni-Co/MCM-41 was pyrolyzed within the same temperature range in the pyrolysis chamber. Temperature and time were optimized for maximum oil yield. A maximum oil yield of 38% was achieved at 330 °C and 20 min. The oil obtained was studied using GCMS. The physicochemical characteristics of the oil were assessed, and it was found that if the oil was upgraded properly, it could serve as a fuel for commercial use.

Thermocatalytic Decomposition of Dimethyl Methylphosphonate Based on CeO2 Catalysts with Different Morphologies

The catalytic performances of the catalysts and decomposition mechanisms of dimethyl methylphosphonate (DMMP), a commonly used nerve agent simulant, are well understood based on previous studies. However, the effects of the morphology of the catalyst on DMMP decomposition performance and mechanisms remain unexplored. Thus, in this work, experimental studies were conducted on the thermocatalytic decomposition of DMMP on CeO2 nanomaterials with different morphologies, e.g., irregular nanoparticles, nanorods, and nanocubes. From the performance evaluation, CeO2 nanorods exhibited higher DMMP thermocatalytic decomposition performance as compared to irregular nanoparticles and nanocubes. The primary reaction pathways were the same on all three morphologies of materials, according to in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) study, whereas side reaction paths showed variable behaviors. According to the catalytic reaction mechanism study, the surface lattice oxygen played a vital role in the thermocatalytic decomposition of DMMP and the accumulation of phosphates, carbonates, and formates were the main factors for deactivation of the catalyst. The behavior of CeO2 catalyst with different morphologies in the thermocatalytic decomposition of DMMP was revealed in this work, and this will be useful for the future design of high-performing catalysts for the efficient degradation of chemical toxicant.

Production of Bio-Oil from Thermo-Catalytic Decomposition of Pomegranate Peels over a Sulfonated Tea Waste Heterogeneous Catalyst: A Kinetic Investigation

In this study, the pyrolysis procedure was used to extract oil from pomegranate peels (PP) utilizing biomass-derived sulfonated tea waste as a catalyst. FTIR, SAA, SEM, and XRD were used to characterize the catalyst. Thermo-catalytic decomposition was carried out in a salt bath reactor and the bio-oil composition was determined through GC-MS. The oil obtained from virgin PP was observed to contain compounds in the range of C5–C13, whereas from the catalyzed reaction it was found to be rich in C5–C23. For the calculation of kinetic parameters, TG analysis was performed of virgin PP and with the catalyst at different heating rates. TG/DTG indicated weight loss in four steps. The first weight loss below 100 °C is due to the physically adsorbed water molecule evaporation. The second weight loss is attributed to hemicellulose decomposition and the third one to cellulose degradation. The fourth weight loss is due to lignin degradation. Kissinger model was used for measuring the activation energy (Ea) of the decomposition reaction. The activation energy of hemicellulose, cellulose, and lignin for non-catalytic reactions was observed as 199, 249, and 299 kJmol−1, while in the case of the loaded tea waste catalyst, the Ea was reduced to 122, 163, and 207 kJmol−1, respectively, confirming the effectiveness of the catalyst. From these findings, it can be concluded that sulfonated tea waste catalyst has not only lowered the pyrolysis temperature and Ea but also brought a change in oil quality by enhancing value-added compounds in the bio-oil.

Fabrication and evaluation of the Mn-promoted Ni/FeAl2O4 catalysts in the thermocatalytic decomposition of methane: Impact of various promoters

This research is focused on the designing and developing catalytic systems over various metal oxides (CuO, Cr2O3, Co3O4, ZnO, and MnO2) promoted NiO/FeAl2O4 catalysts in the thermocatalytic decomposition of CH4. The catalysts were synthesized based on the wet impregnation method, and the nominal NiO content was fixed at 50 wt% along with each transition metal at 10 wt%. The controlled preparation method caused the sample doped with MnO2 to show the highest specific surface area (46.8 m2/g) and the lowest particle size (10.6 nm) among the promoted samples. The activity test revealed that the MnO2(10)-NiO(50)/FeAl2O4 catalyst was the most active and stable catalyst in the CH4 decomposition reaction. At 700 °C, the CH4 conversion and H2 yield were 62.3 and 66 % over this catalyst. Also, the decline in its initial activity was only 3 % during the 300 min reaction time at 575 °C. Also, the results indicated that the catalytic efficiency and rate of carbon production increased by raising the MnO2 content from 5 to 10 wt%. However, the high amount of the deposited carbon and decline in metal dispersion led to the catalytic activity being reduced when the MnO2 loading was increased from 10 to 15 wt%. The impact of calcination temperature (600, 700, and 800 °C) was also investigated on the characterization features and conversion rate of the selected catalyst, and the results revealed that the catalyst calcined at 600 °C displayed the highest efficiency under studied conditions. Furthermore, the results indicated that the catalytic activity and stability decreased by increasing the GHSV value from 40000 to 60000 ml.h−1.g-1cat and CH4:N2 molar ratio from 10:90 to 30:70. Also, the CH4 conversion decreased from 47 to 28 % when the reduction temperature increased from 700 to 800 °C, respectively.

Understanding the synergistically enhanced thermocatalytic decomposition of ammonium perchlorate using cobalt nanoparticle-embedded nitrogen-doped graphitized carbon

The excellent catalytic activity of Co-NPs@NC is attributed to the well-dispersed Co NPs, the intrinsic adsorption capacity for NH3, and the synergistically enhanced effect of NC, which favor the thermal catalytic decomposition of AP.