Catalytic Thermal Decomposition Research Articles

Facile Design of Bi2S3‐Doped CeO2/Dihydroxybenzoate Composite as Highly Efficient UV‐Shielding Agents

AbstractIn this study, bismuth sulfide (Bi2S3)‐doped cerium oxide (CeO2) was prepared via hydrothermal method, and by depositing ethyl 3,4‐dihydroxybenzoate (EDHB) on the surface of Bi2S3/CeO2 (Bi2S3/CeO2/EDHB and BCE). The samples were characterized by FTIR, XRD, TEM, and UV–vis absorption spectrum means. According to the characterizations, Bi2S3 was successfully incorporated into the CeO2 structure (Bi2S3/CeO2), and the prepared BCE/PVC composite films display excellent UV‐shielding property. Moreover, the result of thermogravimetric analysis (TGA) tests indicated that BCE also was barely catalytic thermal decomposition of PVC matrix. This work not only paves an attractive way for the design of the CeO2‐based UV‐shielding agent, but also provides valuable insights into the inspiration to construct high‐performance UV‐shielding composites.

Enhancing combustion performance of solid propellants using synergistic effect of energetic metal–organic framework with cage-like [Bi6(µ3-O)3(µ3-OH)5] clusters and copper-iron hetero-metallic compound

This study explores the potential of energetic metal–organic frameworks (E-MOFs) to enhance the combustion performance of solid propellants. A {[Bi6O3(tza)5(NO3)2(OH)5]·H2O}n (Bi-MOF) incorporating the energetic ligand tetrazole-1-acetic acid (Htza) was synthesized and evaluated for structural characteristics and properties. The catalytic thermal decomposition of cyclotrimethylene trinitramine (RDX) and cyclotetramethylene tetranitramine (HMX) by mixed systems was investigated. These systems consisted of Bi-MOF and copper-iron hetero-metallic compound ({[CuFe3O(tza)6(H2O)3]·Cl·(NO3)2·4H2O}n, CuFe-MOF), previously reported by our group in different ratios. The effect of the mixed system with the highest synergy index on the combustion performance of composite modified double-base propellant (RDX-CMDB) and nitrate ester plasticized polyether propellant (HMX-NEPE) was investigated. The impact of varying carbon black (CB) contents on the catalytic performance of the mixed system was also examined. The results showed that Bi-MOF exhibits good thermal stability (Tdec = 226.9 °C) and insensitivity (IS>40 J, FS>360 J). The mixed system, comprising Bi-MOF and CuFe-MOF in a 2:1 ratio (M2), exhibited the highest synergistic indices (3.35 and 3.24) on thermal decomposition for RDX and HMX. RDX-CMDB and HMX-NEPE propellant formulations containing M2 and a small amount of CB exhibited significant improvements in combustion performance. RDX-CMDB propellant exhibited up to an 80.6 % increase in burning rate and up to a 59.6 % reduction in pressure index. The pressure indices of NEPE without and with aluminum were reduced from 0.65 and 0.50 to 0.38 and 0.40, respectively (10–20 MPa, 1–20 MPa). These findings highlight the promise of the mixed system, formed by Bi-MOF and CuFe-MOF, as a potential combustion catalyst for RDX-CMDB and HMX-NEPE propellants.

Enhanced photocatalytic dehydrogenation of formic acid over ultrafine electron-deficient Pd nanoparticles immobilized on amine-functionalized mesoporous titanium dioxide

Formic acid (FA) has been increasingly favored by researchers as an ideal material for the chemical storage of hydrogen. However, the exploration of photocatalytic hydrogen evolution from FA is less extensive compared to conventional thermal catalytic FA decomposition. Therefore, constructing highly active photocatalysts for H2 release from FA presents a challenging issue. Herein, we employed a strategy that involves Pd nanoparticles (NPs) immobilized on amine-functionalized mesoporous titanium dioxide (TiO2–NH2) to promote hydrogen production from FA under full-spectrum light illumination. Impressively, the as-made 2 wt% Pd/TiO2–NH2 catalyst showed remarkable activity under full-spectrum light (Turnover frequency (TOF) of 1380.5 h−1 at 308 K, H2 selectivity: 100%). Characterization results indicated that the unique mesoporous structure of TiO2–NH2, the synergistic interaction of Pd NPs with –NH2, and the Mott-Schottky heterojunction are primarily responsible for the excellent photocatalytic performance of 2 wt% Pd/TiO2–NH2. This study modulates the metal-support interactions through surface engineering and proposes a novel and effective method for the construction of high-performance photocatalysts for H2 production from FA or other photoinduced reactions.

Preparation of metal–organic framework-199 (Cu) and their effects on catalytic decomposition of hexahydro-1,3,5-trinitro-s-triazine

In this study, a series of metal–organic framework-199 (MOF-199) products were prepared with copper (Cu) as the metal center and trimesic acid as the organic ligand. The morphological changes of MOF-199 under different preparation conditions and its application in the catalytic thermal decomposition of hexahydro-1,3,5-trinitro-s-triazine (RDX) were studied. The morphological changes of MOF-199 were compared by scanning electron microscopy (SEM), the crystal structures of MOF-199 were analyzed by X-ray diffraction and the effects of MOF-199 with different morphological characteristics on the thermal decomposition behavior of RDX were studied by differential scanning calorimetry. The results showed that MOF-199 with different morphologies could effectively adjust the thermal decomposition process of RDX and reduce the decomposition peak temperature of RDX, and the catalytic effect of MOF-199 was different due to different crystal surfaces exposed. Among them, (110) was a highly active crystal plane with a high catalytic activity. In addition to the crystal plane structure, the defects on the surface of MOF-199 would also affect its catalytic performance. This study provides some theoretical support for the catalytic mechanism of MOFs in the thermal decomposition of nitro compounds.

Nitrogen‐doped reduced graphene oxide/Fe2O3 hybrid as efficient catalyst for ammonium nitrate

AbstractIn this investigation, we successfully synthesized a hybrid material, N‐rGO@Fe2O3, via a one‐step hydrothermal process, comprising nitrogen‐doped reduced graphene oxide and α‐Fe2O3. Thorough characterization using diverse analytical methods validated its structure. Employing this hybrid composite as a catalyst, we studied its efficacy in the catalytic thermal decomposition of ammonium nitrate (AN). The N‐rGO@Fe2O3/AN composite was prepared using a recurrent spray coating method with 3 % mass of the hybrid material. Thermo‐gravimetric (TG) and differential scanning calorimetric (DSC) analyses were employed to investigate the catalytic effect. Computational assessment of Arrhenius parameters was conducted through isoconversional kinetic approaches. Results from the kinetic analysis allowed the determination of the critical ignition temperature. Furthermore, calorific values for pure AN and N‐rGO@Fe2O3/AN were measured using an oxygen calorimetric bombe, revealing a 41 % reduction in activation energy barrier and a lowering of the critical ignition temperature from 292 °C to 283 °C upon incorporation of the hybrid material. Notably, the surface modification of AN with N‐rGO@Fe2O3 resulted in an increase of 1440 J/g in the observed calorific values. These findings highlight the potential of N‐rGO@Fe2O3 as an effective catalyst, offering promising implications for applications in enhancing ammonium nitrate thermal decomposition.

Study on Ni-based Bead Catalyst for Catalytic Thermal Decomposition of Light Hydrocarbons

Study on Ni-based Bead Catalyst for Catalytic Thermal Decomposition of Light Hydrocarbons

Reactivity and catalytic effect of coals during combustion: Thermogravimetric analysis

Catalytic coal combustion is a promising technology to realize efficient utilization of coal, however, the catalysis in the coal combustion process is unclear. This paper focused on the effects of two type catalysts (metal oxides and metal compounds) on the combustion reactivity of lignite, bituminous coal and anthracite using thermogravimetric analyzer, and discussed the catalytic mechanisms combining with catalytic thermal decomposition and catalytic char combustion. All catalysts decreased the ignition temperature and burnout temperature of coals to the extent of 0.25–81.25 °C, 24.75–73.25 °C, and increased the exothermic values. The catalytic effect was influenced by coal rank and had the greatest promoting effect on anthracite. Besides, the pyrolysis conversion rates of coals were increased by catalysts, resulting in ignition advance and made the subsequent reaction easier. The results of catalytic char combustion showed that both catalysts significantly reduced the ignition temperature of char, the Na2CO3 had the best catalytic effect on fixed carbon combustion, while CaO mainly affected the release of volatile matter. Finally, the catalytic mechanism in coal combustion was discussed. This article aims to provide theoretical reference for the practical comprehensive application of coal catalytic combustion.

Balancing act: influence of Cu content in NiCu/C catalysts for methane decomposition.

Thermal catalytic decomposition of methane is an innovative pathway to produce CO2-free hydrogen from natural gas. We investigated the role of Cu content in carbon-supported bimetallic NiCu catalysts. A graphitic carbon material was used as a model support, and we combined operando methane decomposition experiments in a thermogravimetric analyzer with in situ electron microscopy measurements. The carbon yield was maximum with around 30% Cu in the nanoparticles. Adding more Cu drastically lowered the carbon solubility in the metal nanoparticles, which lowered the initial reaction rate and overall carbon yield. In situ TEM measurements showed that the addition of Cu to the catalysts strongly influenced the metal nanoparticle shape and size during carbon growth, and the growth mode. NiCu particles were larger, remained spherical and facilitated steady CNF growth. In contrast, pure Ni nanoparticles fluctuated in shape, sometimes fragmented, and showed stuttering CNF growth. This was ascribed to fluctuating coverage of part of the Ni nanoparticle surface with amorphous carbon, which increased the chance of total encapsulation and hence deactivation of the individual Ni nanoparticles. This supports a picture where balancing the carbon supply, transport, and nucleation of amorphous and crystalline carbon is crucial. Our results also highlight the importance of combining statistically relevant measurements with microscopic information on individual nanoparticles to understand overall catalytic trends from the combined behavior of individual catalyst nanoparticles.

Spiral gas-solid two-phase flow continuous mechanochemical synthesis of salophen complexes and catalytic thermal decomposition of ammonium perchlorate.

Although mechanochemistry is increasingly becoming an alternative to traditional chemical synthesis, highly efficient continuous mechanochemical synthesis techniques are still rare. In this work, a novel spiral gas-solid two-phase flow (S-GSF) synthesis technique for the mechanochemical synthesis of salophen complexes has been reported, which is an approach for continuous synthesis based solely on airflow impacting the reaction. The synthesis of salophen-Br-Cu was used as a model reaction to optimize the reaction conditions, and three other salophen complexes, namely, salophen-Br-Co, salophen-Br-Ni, and salophen-Br-Zn were synthesized on this basis. The structure and thermal stability of the obtained products were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, UV-vis spectroscopy, nuclear magnetic resonance spectroscopy, scanning electron microscopy, and differential thermal analysis (DTA). The results showed that these complexes can be obtained continuously at a rate close to 4 g min-1, and the corresponding space-time yield is close to 1.2 × 105 kg m-3 day-1. In addition, DTA was used to analyze the catalytic performance of the complex for ammonium perchlorate (AP). The results showed that compared to the conditions for pure AP, salophen-Br-Co and salophen-Br-Cu could significantly reduce the high-temperature decomposition of AP pyrolysis to 77.0 and 102.1 °C, respectively. According to the method of Kissinger calculations, the Ea of AP decomposition decreased from 217.3 kJ mol-1 to 131.0 and 118.5 kJ mol-1, respectively. The TG data at different heating rates were analyzed using two isoconversion methods, i.e. Flynne-Walle-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS). The activation energies of AP, AP + 10 wt% salophen-Br-Co, and AP + 10 wt% salophen-Br-Cu were calculated. When the conversion degree (α) is between 0.1 and 0.9, the Ea values obtained from the two isoconversion methods are similar and exhibit certain matching. These two isoconversion methods also confirm Kissinger's calculations.

Investigation of the Effects of Temperature and Catalyst on the Liquid Products of Waste Lubricant Oil Catalytic Pyrolysis

Catalytic pyrolysis is the process in which organic materials undergo catalytic thermal decomposition in the absence of oxygen. In this study, catalytic pyrolysis was conducted by heating waste lubricant oil in a modified catalytic reactor for 60 minutes at 350, 450, and 550°C. Furthermore, the effect of a catalyst on the pyrolysis of waste lubricant oil was investigated. The catalyst used was natural zeolite with particle sizes of 70/100 mesh, 200/250 mesh and > 400 mesh. The catalytic pyrolysis liquid products obtained were then analyzed to determine the viscosity, density, heat value and composition of carbon compounds. The results show that temperature, the addition of catalysts and the catalyst particle size affect the physical and chemical properties of liquid products. On the basis of these properties, liquid products can be grouped into several types of liquid fuels namely, gasoline, kerosene and diesel. The liquid products obtained with a catalytic pyrolysis at temperature 550°C and catalyst particle size of > 400 mesh have a density, viscosity, yield and heating value of 829.760 kg/m3, 1.9508 mPa⋅s, 45.33% and 10.981 calories/gram, respectively. The composition of carbon compounds in liquid products is 20.39% for C < 8 compounds and 79.61% for C8-C18 compounds. These liquids are similar to gasoline, kerosene and diesel.

Construction of cobalt–nickel bimetallic coordination polymers and their catalytic thermal decomposition of ammonium perchlorate

The addition of a catalyst to ammonium perchlorate (AP) can effectively improve its thermal decomposition properties. The heterobimetallic complex Ni-Co-pzdc (2,3-pyrazinedicarboxylic acid) was synthesized via in situ substitution, and the N-doped Ni-Co-pzdc derivative was prepared by using it as a sacrificial template. A series of characterization tools were used to investigate the morphological and structural features of the resulting materials, and the thermal decomposition behaviors of the two products were investigated by homogeneous mixing with AP, respectively, and the activation energies were calculated by using Kissinger, Kissinger-Akahira-Sunose (KAS), and Flynn-Wall-Ozawa (FWO), and the results showed that both substances possessed excellent catalytic activities.

NH3 decomposition for H2 production by thermal and plasma catalysis using bimetallic catalysts

Plasma catalysis has emerged as a promising approach for driving thermodynamically unfavorable chemical reactions. Nevertheless, comprehending the mechanisms involved remains a challenge, leading to uncertainty about whether the optimal catalyst in plasma catalysis aligns with that in thermal catalysis. In this research, we explore this question by studying monometallic catalysts (Fe, Co, Ni and Mo) and bimetallic catalysts (Fe-Co, Mo-Co, Fe-Ni and Mo-Ni) in both thermal catalytic and plasma catalytic NH3 decomposition. Our findings reveal that the Fe-Co bimetallic catalyst exhibits the highest activity in thermal catalysis, the Fe-Ni bimetallic catalyst outperforms others in plasma catalysis, indicating a discrepancy between the optimal catalysts for the two catalytic modes in NH3 decomposition. Comprehensive catalyst characterization, kinetic analysis, temperature program surface reaction experiments and plasma diagnosis are employed to discuss the key factors influencing NH3 decomposition performance.

The effect of oxygen defects in Cu2O1−x nanocatalyst on the catalytic thermal decomposition of ammonium perchlorate

The effect of oxygen defects in Cu2O1−x nanocatalyst on the catalytic thermal decomposition of ammonium perchlorate

The effect of oxygen vacancy defects in nano-CuO1−x on its catalytic properties in ammonium perchlorate thermal decomposition

The oxygen vacancy defect engineering has been identified as a valid strategy to modify the physicochemical and catalytic properties of semiconductor catalysts, but it’s rarely used in combustion catalyst. Herein, a novel oxygen deficient copper oxide (CuO1−x) nano-combustion catalyst was successfully prepared by a two-step process involving the controlled chemical precipitation and vacuum sintering. As expected, the CuO1−x exhibits enhanced catalytic activity towards the ammonium perchlorate (AP) thermal decomposition. Once CuO1−x nanocatalyst was added, the high-temperature decomposition peak temperature (THTD) and the apparent activation energy (Ea) of AP are respectively decreased by 109.2 °C and 79.2 kJ/mol, higher than those of commercial nano-CuO (80.6 °C and 56.4 kJ/mol), showing significant oxygen vacancy defect effects. In addition, the effect of oxygen vacancy defects in CuO1−x on the catalytic thermal decomposition behaviors and mechanism of AP were investigated by thermal analysis techniques and density functional theory for the first time. The results prove that the improved catalytic performance of CuO1−x towards the thermal decomposition of AP might relate to the enhanced adsorption and bonding capacity with NH3, which helps to prevent the accumulation of NH3 and consequently promote the thermal decomposition reaction of AP.

Enoki-like carbon nanotubes coated with in situ growing nickel particles for enhanced electromagnetic wave absorption

With the increasingly serious electromagnetic pollution, the urgent demands for electromagnetic wave absorption (EMWA) materials are gradually developing towards performance integration and multi-dimensional scales. Herein, the enoki-like carbon nanotubes (CNTs) coated with nickel particles (CNT@Ni) were synthesized by a catalytic thermal decomposition method. The resulting CNT@Ni composites exhibited excellent EMWA performances with a minimum reflection loss value of − 60.4 dB at a thickness of 2.97 mm. It benefited from the synergy of collaborative electrical and magnetic losses and hierarchical structure. The conductive pathways formed by the intertwined CNTs greatly improved the EMWA capacity of the material, enabling large amounts of electromagnetic waves to enter the material for conversion and dissipation. In addition, the inherent graphite defects and oxygen-containing groups formed on the material surface during the process of high-temperature treatment provided polarization centers for dipole polarizations. More importantly, the abundant heterogeneous interfaces enhanced the interface loss effects of the material. This simple preparation strategy of the CNT-based EMWA material will provide a design inspiration for the novel electromagnetic absorber.

The catalytic thermal decomposition of ammonium perchlorate on CuMxOy (M = Fe, Ni, Co and Zn) catalysts and their applications in solid propellant

The catalytic thermal decomposition of ammonium perchlorate on CuMxOy (M = Fe, Ni, Co and Zn) catalysts and their applications in solid propellant

Preparation of surface modified ammonium perchlorate with green iron oxide nitrocellulose nanocomposite for catalytic thermal decomposition of ammonium perchlorate

This work concerns kinetic modeling and the investigation of the thermal decomposition of surface modified ammonium perchlorate (AP) with green iron oxide nitrocellulose nanocomposite (AP–NC–nFe2O3), via a recurrent spray drying method (SDM). The thermal degradation of the different investigated samples was studied by differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis. The kinetics of the thermal decomposition reaction of the various prepared samples and the pure AP were estimated by differential scanning calorimetry (DSC) combined with various isoconversional methods. Additionally, the critical ignition temperature was calculated. For comparison, a similar study was carried out for the pure AP and the surface modified ammonium perchlorate (AP) by SDM with green nano iron oxide (AP-nFe2O3). The results of the kinetic investigation showed that AP-nFe2O3 and AP–NC–nFe2O3 had lower activation energies than pure AP, demonstrating the catalytic impact of nFe2O3, and which is strengthened by the addition of NC. In addition, the results have demonstrated that the surface modifications of AP reduced critical ignition temperature compared to that of pure AP.

Catalytic thermal decomposition of ammonium perchlorate by a series of lanthanide EMOFs

Given their unique and excellent properties, metal–organic frameworks (MOFs) materials have been used in many scientific fields. EMOFs use energetic materials as ligands, which can provide part of the energy for the system while catalyzing ammonium perchlorate. The energetic material 1.1′-dihydroxyazotetrazole (H2AzTO), as a high-energy nitrogen-rich material, was selected as a ligand. Five kinds of La3+, Ce3+, Pr3+, Nd3+, and Sm3+ lanthanide EMOFs were synthesized and obtained. Single crystal X-ray diffraction tests were conducted to obtain the crystal structures of EMOFs 1–5, which indicate that they have similar crystal structures. The thermal stabilities of EMOFs 1–5, which are obtained by differential scanning calorimetry (DSC) tests, are improved compared with that of the ligand. The results of thermic-decomposition of ammonium perchlorate (AP) and AP mixtures with 10 wt% EMOFs 1–5 show that except for AP mixed with 10 wt% compound 2, the high-temperature decomposition peak temperature of AP mixed with other compounds is significantly advanced (up to 59.3–88.3 K), and the decomposition of AP is continuous and violent. EMOFs 3–5 have good application prospects for the catalytic thermic-decomposition of AP.

Design and performance of a novel high-efficiency WO3-based combustion catalyst and its catalytic mechanism

To develop efficient combustion catalyst for solid propellants, a novel WO3-based composite (CuX-WO3/Biochar) was designed by the method of doping and loading. As a dopant, Cu has the advantages of producing multiple bands, inhibiting grain growth and restraining exciton–exciton collisions. Meanwhile, biochar is cheap and available as a carrier, which can effectively inhibit the agglomeration of nanomaterials. Therefore, in this work, Cu-doped WO3 nanoparticles were uniformly anchored on surface of biochar by in-situ solvothermal reaction combined calcination method, which significantly increased the surface-active area, and was firstly applied to catalytic decomposition and laser ignition of ammonium perchlorate (AP), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) and 5,5′-bistetrazole-1,1′-diolate (TKX-50). With the introduction of CuX-WO3/Biochar, decomposition peak temperature of AP, RDX and TKX-50 diminished by 97.0, 6.7 and 37.9℃, and activation energy decreased by 14.4, 93.5 and 22.6 kJ mol−1, respectively. Simultaneously, flame brightness, flame area and flame propagation speed during combustion of RDX and TKX-50 were evidently improved after CuX-WO3/Biochar was added. Finally, electron transfer mechanism of catalytic thermal decomposition of energetic materials was deduced based on Density Functional Theory (DFT) calculation and characterization analysis. This study will provide a new insight into development of combustion catalysts.

Carbon nanofiber growth from methane over carbon-supported NiCu catalysts: Two temperature regimes

An alternative route towards COx-free production of hydrogen is the thermal catalytic decomposition of methane. In addition to hydrogen, valuable carbon nanomaterials can be formed. Carbon nanofiber formation from methane decomposition over carbon supported NiCu catalysts was studied in-situ using a Thermogravimetric analyzer. We especially investigated how the carbon yield is influenced by reaction parameters. Based on experiments with varying temperature (450–600 °C), two distinct temperature regimes were identified. Different kinetic parameters were derived for the two regimes. Activation energies of 86 and 45 kJ/mol, and reaction orders in methane of close to 1 and 1.5, were found in the low and high temperature regimes, respectively. We postulate that at lower temperature the methane dissociation is rate limiting, while at higher temperature the carbon formation plays a more critical role. At low temperatures mostly full fishbone fibers are formed, whereas at higher temperatures mainly hollow fibers are formed. The maximum carbon yield is obtained at the transition between the two regimes, when the carbon supply and carbon nanostructure formation are balanced.