Catalytic Decomposition Research Articles

Density Functional Theory Study of Mechanism of Reduction of N2O by CO over Fe-ZSM-5 Zeolites

Nitrous oxide (N2O) is an industrial waste gas (e.g., from the production of adipic acid), which damages the ozone layer and causes the greenhouse effect. Density functional theory calculations were employed to investigate the mechanism of direct catalytic decomposition of N2O and selective catalytic reduction (SCR) of N2O by CO over Fe-ZSM-5 zeolites. Two stable Fe-active sites with six-membered ring structures on Fe-ZSM-5 were considered. The calculations indicate that the decomposition of N2O is affected by the coordination environment around Fe and can occur through two reaction pathways. However, there is invariably a more considerable energy hurdle for the initiation of the second stage of N2O decomposition. When CO participated in the reaction, it showed good reactivity and stability, the reaction energy barriers of the rate-limiting step were reduced by roughly 20.57 kcal/mol compared to the direct catalytic decomposition of N2O. CO exhibited a superior electron-donating ability and orbital hybridization performance during the reaction, which enhanced the cyclicity of the N2O reduction catalytic process. Our calculations confirmed the significant role of CO in N2O reduction over Fe-ZSM-5 observed in previous studies. This study provides a valuable theoretical reference for exploring CO-SCR methods for N2O reduction over Fe-based zeolite catalysts.

New insights into the effect of polyvinyl alcohol on Co3O4 spinel oxide catalyst for N2O decomposition

Polyvinyl alcohol (PVA)-assisted precipitation method offered surface modification Co3O4 spinel oxides which were applied to catalytic N2O decomposition. PVA was added in the preparation process and endowed catalysts with changes in surface metal ions valance state properties, i.e. Co2+ ions which served as active centers. Co3O4 adding PVA (Co3O4-P) showed superior performance for catalytic N2O decomposition with a high gas hourly space velocity of 400,000 h−1. Co2+ ion quantities were positively correlated to catalytic performance which was inseparable from PVA superhydrophobicity and reducibility during the preparation process. Moreover, density functional theory (DFT) calculation revealed N2O preferable adsorption on Co2+ sites whether near oxygen vacancies or not, which indirectly affirmed the reason Co3O4-P with superior catalytic N2O decomposition property. Our research gave more evidence to N2O decomposition active sites from atom-scale for Co3O4 spinel oxides and provided a novel pathway for high-performance catalyst preparation.

Structure and Microchannel Catalytic Bed Performance of Silver Thin Films Prepared by Electroplating

The morphology of catalysts in microchannels plays a crucial role in the orbital maneuvering and networking applications of micro/nano satellites using hydrogen peroxide as a unit propellant. In this paper, a microfluidic reaction chip was designed and fabricated to detect the reaction rate of the catalytic decomposition of hydrogen peroxide solution by a microchannel catalytic bed. In addition, a silver thin film prepared by constant-current electroplating was used as a substrate for the microchannel catalyst. The results show that the ratio of surface area to area of silver film and the average particle size of silver particles have a significant positive correlation on the reaction rate of catalytic decomposition, while the thickness, silver content, and surface roughness of the silver film have no significant effect on the reaction rate of catalytic decomposition. The catalytic performance of the microchannel catalytic bed of silver thin film is greatly influenced by the conditions of electroplating, namely, the electroplating temperature (T), time (t), and current (I). And when I = 0.3 mA, t = 180 s, and T = 60 °C, the microchannel catalytic bed of the silver film prepared by electroplating reaches the optimal reaction rate for the catalytic decomposition of hydrogen peroxide solution. This study has the best process parameters for the design and optimization of heterogeneous catalysts applied to microfluidic reactors.

Biodegradable CoSnO3 nanozymes modulate pH-responsive graphene quantum dot release for synergistic chemo-sonodynamic-nanocatalytic cancer therapy

Albeit nanozymes are widely applied for nanocatalytic therapy (NCT), the unsatisfactory catalytic activity of nanozymes accompanied by complex tumor microenvironment (TME) greatly pose a barrier to the therapeutic effect of NCT. Moreover, developing a high-efficiency nanozyme with biodegradability is still a huge challenge, which hinders their further clinical translation. Herein, pH-responsive biodegradable CoSnO3 nanocubes are synthesized and employed as sonosensitizers and nanozymes due to their narrow bandgaps (1.6 eV) and Co2+/Sn4+-mediated multi-enzyme activities. After depositing the graphene quantum dot (GQD) topoisomerase inhibitors on CoSnO3 nanocubes, the heterojunction-fabricated GQD/CoSnO3 shows cascaded amplification of ROS generation, which is ascribed to the inhibition of electron-hole pair recombination, Co2+-mediated peroxidase (POD)-mimic catalytic reaction to generate OH, Co3+/Sn4+-mediated depletion of overexpressed GSH, and catalytic decomposition of endogenous H2O2 for providing more O2 for enhanced SDT. More importantly, GQD/CoSnO3 heterojunctions are slowly degraded in the weakly acidic TME, resulting the tumor-specific release of GQDs after completion of SDT, which could induce DNA damage and cell apoptosis for chemotherapy to further enhanced the antitumor efficacy. The synergetic therapeutic efficacy of GQD/CoSnO3 heterojunctions through chemotherapy, SDT, and NCT could realize “three-in-one” multimodal oncotherapy to completely eliminate tumors without recurrence. This work provides a paradigm of exploring pH-responsive biodegradable nanozymes as a drug carrier to realize tumor-specific drug release for enhanced SDT and NCT.

Research progress on the catalytic and thermal decomposition of ammonium dinitramide (ADN).

Ammonium dinitramide (NH4N(NO3)2, ADN) is regarded as a promising oxidizer due to its low signature and high specific impulse. Generally, ADN undergoes exothermic decomposition above 140 °C accompanied by the byproduct of ammonium nitrate (AN). The inevitable endothermic decomposition of AN decreases the overall heat release, and so there is a need to develop efficient catalysts to guide ADN decomposition along desired pathways with a lower decomposition temperature and higher heat release. A suitable catalyst should be able to withstand the harsh conditions in a thruster to achieve a stable thrust force, which poses a huge obstacle for manufacturing a stable and active catalyst. This review gives a comprehensive summary of the thermal and catalytic decomposition pathways of ADN for the first time, which is expected to deepen the understanding of its reaction mechanism and provide useful guidance for designing prospective catalysts toward efficient ADN decomposition.

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.

Machine learning for deconstructing contributions of atomic characterizations to achieve hybridization-determined electron transfer in a perovskite catalyst

Machine learning deconstructed the atomic contribution of a perovskite to catalytic toluene decomposition and found that wider hybridization resulted in smaller impedance, faster electron transfer speed, and enhanced catalytic activity.

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.

Preparation of HMn2O4 lithium-ion sieves with low manganese dissolution loss for improved cycling stability.

Manganese-based lithium-ion sieves have become some of the promising adsorbents for extracting Li+ from brines. However, manganese dissolution loss (MDL) severely impairs the stability and cyclicity of ion sieves. A novel ozone eluent was first developed to extract Li+ from lithium manganese oxides, which decreased MDL decreased from 5.89% to 0.11%, and after ten regeneration cycles, the adsorption capacity retained 85.39% of the initial value, which was better than 55.15% when only hydrochloric acid (HCl) was used as the eluent. Based on these phenomena, the mechanism for the O3 lowering of MDL was investigated. First, the catalytic decomposition reaction of O3 competed with the disproportionation reaction, and the involvement of O3 inhibited the occurrence of the disproportionation reaction. Additionally, the presence of O3 and reactive oxygen species provided a preferential electron acceptor compared to Mn3+ during the migration of electrons from the bulk phase to the surface. In this study, MDL was greatly reduced with a very simple strategy, and the cycling stability of the adsorbent was improved.

An NIR-II-photoresponsive CoSnO3 nanozyme for mild photothermally augmented nanocatalytic cancer therapy.

The main challenges of nanozyme-based tumor catalytic therapy (NCT) lie in the unsatisfactory catalytic activity accompanied by a complex tumor microenvironment (TME). A few nanozymes have been designed to possess both enzyme-like catalytic activities and photothermal properties; however, the previously reported nanozymes mainly utilize the inefficient and unsafe NIR-I laser, which has a low maximum permissible exposure limit and a limited penetration depth. Herein, we report for the first time an all-in-one strategy to realize mild NIR-II photothermally amplified NCT by synthesizing amorphous CoSnO3 nanocubes with efficient triple enzyme-like catalytic activities and photothermal conversion properties. The presence of Co2+ and Sn4+ endows CoSnO3 nanocubes with the triple enzyme-like catalytic activities, not only achieving enhanced reactive oxygen species (ROS) generation through the Co2+-mediated peroxidase-like catalytic reaction to generate ˙OH and Sn4+-mediated depletion of overexpressed GSH, but also realizing the catalytic decomposition of endogenous H2O2 for relieving tumor hypoxia. More importantly, the obtained CoSnO3 nanocubes with a high photothermal conversion efficiency of 82.1% at 1064 nm could achieve mild hyperthermia (43 °C), which further improves the triple enzyme-like catalytic activities of the CoSnO3 nanozyme. The synergetic therapeutic efficacy of the NIR-II-responsive CoSnO3 nanozyme through mild NIR-II PTT-enhanced NCT could realize all-in-one multimodal tumor therapy to completely eliminate tumors without recurrence. This study will open a new avenue to explore NIR-II-photoresponsive nanozymes for efficient tumor therapy.

Progress and challenges in nitrous oxide decomposition and valorization.

Nitrous oxide (N2O) decomposition is increasingly acknowledged as a viable strategy for mitigating greenhouse gas emissions and addressing ozone depletion, aligning significantly with the UN's sustainable development goals (SDGs) and carbon neutrality objectives. To enhance efficiency in treatment and explore potential valorization, recent developments have introduced novel N2O reduction catalysts and pathways. Despite these advancements, a comprehensive and comparative review is absent. In this review, we undertake a thorough evaluation of N2O treatment technologies from a holistic perspective. First, we summarize and update the recent progress in thermal decomposition, direct catalytic decomposition (deN2O), and selective catalytic reduction of N2O. The scope extends to the catalytic activity of emerging catalysts, including nanostructured materials and single-atom catalysts. Furthermore, we present a detailed account of the mechanisms and applications of room-temperature techniques characterized by low energy consumption and sustainable merits, including photocatalytic and electrocatalytic N2O reduction. This article also underscores the extensive and effective utilization of N2O resources in chemical synthesis scenarios, providing potential avenues for future resource reuse. This review provides an accessible theoretical foundation and a panoramic vision for practical N2O emission controls.

Catalytic decomposition of hydrazine nitrate and hydroxylamine nitrate in radioactive nitric acid waste liquid using Ru/AC catalyst

The 5 wt% Ru/AC catalysts were prepared using the impregnation method.

A novel magnetically guided, oxygen propelled CoPt/Au nanosheet motor in conjugation with a multilayer hollow microcapsule for effective drug delivery and light triggered drug release.

In recent years, nanomotors have been developed and attracted extensive attention in biomedical applications. In this work, a magnetically-guided oxygen-propelled CoPt/gold nanosheet motor (NSM) was prepared and used as an active self-propelled platform that can load, transfer and control the release of drug carrier to cancer cells. As a drug carrier, the microcapsules were constructed by the layer-by-layer (LbL) coating of chitosan and carboxymethyl cellulose layers, followed by incorporation of gold and magnetite nanoparticles. Doxorubicin (DOX) as an anti-cancer drug was loaded onto the synthesized microcapsules with a loading efficiency of 77%. The prepared NSMs can deliver the DOX loaded magnetic multilayer microcapsule to the target cancer cell based on the catalytic decomposition of H2O2 solution (1% v/v) via guidance from an external magnetic force. The velocity of NSM was determined to be 25.1 μm s-1 in 1% H2O2. Under near-infrared irradiation, and due to the photothermal effect of the gold nanoparticles, the proposed system was found to rapidly release more drugs compared to that of an internal stimulus diffusion process. Moreover, the investigation of cytotoxicity of NSMs and multilayer microcapsules clearly revealed that they have negligible side effects over all the concentrations tested.

Effect of the Ca/P ratio of Ni-loaded hydroxyapatite on the catalytic decomposition of biomass tar at low temperatures

Ni-loaded catalysts using hydroxyapatite (HAp) supports with various Ca/P ratios are promising biomass tar decomposition catalysts at low gasification temperatures (i.e., 450 °C), and that variations in the Ca/P ratio of the HAp support allow tuning of the Ni dispersion state and catalytic activity.

Morphological impact of 1-dimensional → 3-dimensional manganese dioxides on ozone catalytic decomposition correlated with crystal facet and lattice oxygen mobility

Ozone is a pollutant that has received widespread attention in recent years, and manganese dioxide (MnO2) has been widely used for ozone catalytic decomposition. However, few studies have described the...

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.

Design of poly(N-isopropylacrylamide) coated MnO2 nanoparticles for thermally regulated catalytic decomposition of H2O2

We report the synthesis of thermoresponsive poly(N-isopropylacrylamide) coated manganese dioxide nanoparticles for the catalytic decomposition of hydrogen peroxide (H2O2), with the goal of developing a temperature-controlled catalytic system.

Low-temperature direct decomposition of NO over Rh/NC-MnFe catalyst: activity, stability and mechanism

As the ideal NO removal technology, the biggest challenge associated with the direct catalytic decomposition of NO is the development of highly active deNOx catalysts at low temperatures.

Methane conversion for hydrogen production: technologies for a sustainable future

We review state-of-the-art technologies and processes of catalytic decomposition of methane (CDM) to produce hydrogen, a COx free technology with carbon nano materials (CNMs) as a byproduct, in view of the circular economy.

Adsorption and dehydrogenation of ammonia on Ru55, Cu55 and Ru@Cu54 nanoclusters: role of single atom alloy catalyst.

Hydrogen production by the catalytic decomposition of ammonia (NH3) is an important process for several important applications, which include energy production and environment-related issues. The role of single Ru-atom substitution in a Cu55 nanocluster (NC) has been illustrated using the NH3 decomposition reaction as a model system. The structural stability of Ru@Cu54 NC has been evaluated using Ru55 and Cu55 NCs for comparison. Ru@Cu54 prefers an icosahedron structure (Ih), like Ru55 and Cu55 NCs, with almost comparable average binding energies of -5.55 eV per atom. The adsorption of NHx (x = 0-3) on different adsorption sites of the icosahedron Ru@Cu54 NC has also been studied and the corresponding adsorption energies have been estimated. The site-preference investigation suggested that NH3 prefers to adsorb vertically to the Ru@Cu54. The stable geometries of the N and H atoms on the high symmetry adsorption sites of Ru@Cu54 NC have been studied. Although the N atom favours top and hollow sites, the H atom prefers to stay in the Ru-Cu bridge site along with the hollow sites. The adsorption energy of N on the Ru@Cu54 NC fcc site is found to be -5.42 eV, which is very close to the optimal value (-5.81 eV) of the ammonia decomposition volcano curve. The reaction energies for stepwise H atom elimination from an adsorbed NH3 molecule have been estimated. Finally, NH3 adsorption and decomposition on Ru@Cu54 have been illustrated in terms of electronic structure analysis. The energetics calculations for the dehydrogenation of NH3 suggest that Ru@Cu54 NC can be a suitable catalyst.