Catalytic Decomposition Research Articles

Application of Mesoporous/Hierarchical Zeolites as Catalysts for the Conversion of Nitrogen Pollutants: A Review

Mesoporous/hierarchical zeolites (HZs) are a relatively new group of materials, and interest in their application in catalysis is continuously growing. This paper presents recent achievements in the application of mesoporous zeolites in catalytic reactions of nitrogen pollutant conversion. The analysis presented includes processes such as selective catalytic reduction of NOx with ammonia (NH3-SCR, DeNOx), selective catalytic oxidation of ammonia (NH3-SCO, AMOx), and catalytic decomposition of N2O. Different zeolite topologies and methods of their modification focused on mesoporosity generation (e.g., desilication, dealumination, steaming, self-assembly techniques, and application of hard and soft templates) are reviewed and compared with respect to catalytic processes. Special attention is paid to the role of porous structure and acidity, as well as the form of deposited transition metals, in the catalytic activation of modified zeolites in the elimination of nitrogen pollutants from flue gases.

Stress-Alteration Enhancement of the Reactivity of Aluminum Nanoparticles in the Catalytic Decomposition of exo-Tetrahydrodicyclopentadiene (JP-10).

High-energy-density aluminum nanoparticles (AlNPs) upon thermal annealing followed by superquenching result in elevated stress levels in the metallic core and reduced surface energy at the core-shell interface. Isomer-selective vacuum ultraviolet-based photoionization mass spectrometry coupled to a high-temperature chemical microreactor reveals that these stress-altered AlNPs (SA-AlNPs) exhibit distinctive temperature-dependent reactivities toward catalytic decomposition of the hydrocarbon jet fuel exo-tetrahydrodicyclopentadiene (JP-10, C10H16) compared to untreated AlNPs (UN-AlNPs). SA-AlNPs show a delayed initiation of the decomposition for JP-10 by 200 K relative to the UN-AlNPs; however, the full decomposition is achieved at a 100 K lower temperature. Furthermore, there are fewer oxygenated products that are generated from the alumina surface-induced heterogeneous oxidation process and a larger fraction of closed- and open-shell hydrocarbons. Chemical insight bridging the reactivity order of SA-AlNPs at low and high temperatures, simultaneously, is obtained via a detailed examination of the product branching ratios obtained in this study.

High-efficiency thermal reduction of CO2 to high-valued carbon nanotubes

To reduce the amount of carbon dioxide (CO2) already emitted into the atmosphere, various carbon capture, utilization, and storage (CCUS) technologies have been developed for climate and economic reasons in recent years. However, the state of art CCUS techniques suffer from deficiencies such as high cost, low yield, and harsh and discontinuous production conditions. In this work, we report a new thermal reduction method for continuously conversing CO2 to methane (CH4) by introducing sodium borohydride (NaBH4) as a reductant under catalyst-free conditions. Experimental results show that CO2 can be fully captured and converted to CH4 and carbon monoxide (CO) and the selectivity efficiency of CO2 to CH4 can be achieved to be as high as 90% with the optimization of experimental conditions. Such a result originates from the high activity of NaBH4 and high selectivity of the thermal reduction of CO2. To demonstrate one of the potential usages of the reduction products, we integrated the thermal reduction of CO2 with the production of carbon nanotubes (CNTs). As long as CO2 is supplied at the source end, the reduction products can undergo catalytic decomposition to produce a CNT fiber or film continuously at the final end. The present technique is featured with simple equipment setup, low cost, and continuous thermal reduction, thus providing a new pathway for the large-scale conversion of CO2 into high-valued products for wide applications.

Space-confined manganese oxides nanosheets for efficient catalytic decomposition of ozone

Ground-level ozone has long posed a substantial menace to human well-being and the ecological milieu. The widely reported manganese-based catalysts for ozone decomposition still facing the persisting issues encompass inefficiency and instability. To surmount these challenges, we developed a mesoporous silica thin films with perpendicular nanochannels (SBA(⊥)) confined Mn3O4 catalyst (Mn3O4@SBA(⊥)). Under a weight hourly space velocity (WHSV) of 500,000 mL g−1 h−1, the Mn3O4@SBA(⊥) catalyst exhibited 100% ozone decomposition efficiency in 5 h and stability across a wide humidity range, which exceed the performance of bulk Mn3O4 and Mn3O4 confine in commonly reported SBA-15. Rapidly decompose 20 ppm O3 to a safety level below 100 μg m−3 in the presence of dust in smog chamber (60 × 60 × 60 cm) was also realized. This prominent catalytic performance can be attributed to the unique confined structure engenders the highly exposed active sites, facilitate the reactant-active sites contact and impeded the water accumulation on the active sites. This work offers new insights into the design of confined structure catalysts for air purification.

Effects of moisture and aging upon decomposition of methyl iodide by reduced silver mordenite

Reduced silver mordenite has been considered as a sorbent for the capture of organic iodides, especially methyl iodide, from off-gases produced by aqueous used nuclear fuel reprocessing operations. The adsorption capacity of this material has been unpredictable especially when NOx and water are present. Previous work has found that a catalytic decomposition reaction is occurring on the surface but few determinations have been made of the kinetics of this reaction. The work presented tested the adsorption behavior and apparent catalytic reaction rate in humid conditions and compared those to dry conditions testing. Both experiments observed a first order reaction with rate constants of 0.0847 L/g sorbent/s and 0.1202 L/g sorbent/s respectively. Such a reduction in apparent rate constant is possibly due to either water obstructing methyl iodide adsorption or product desorption limitation. Changes in the adsorption profile were also apparent between these two, with the humid conditions experiment reaching saturation sooner than the dry conditions experiment. Additionally, an experiment into the effects of sorbent storage in a controlled laboratory environment was performed. The performance of the sorbent materials that were stored with silver in the zerovalent state was slightly inferior to those materials that were stored in ionic form (Ag+) and reduced to zerovalent silver immediately prior to subjecting them to sorption test. The materials stored with silver in the ionic form (and reduced just prior to application) behaved essentially similarly to the freshly synthesized (and reduced) sorbents in the sorption tests. This suggests that zerovalent silver experiences some oxidation resulting in deactivation of some sites.

Catalytic Decomposition of CH4 to Hydrogen and Carbon Nanotubes Using the Pt(1)-Fe(30)/MCM-41 Catalyst

The catalytic decomposition of CH4 to H2 and carbon nanotubes (CNTs) was investigated regarding Pt(1)-Fe(30)/MCM-41 and Fe(30)/MCM-41 using a fixed-bed flow reactor under an atmosphere. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscope (TEM), and Raman spectroscopy were used to characterize the behavior of Pt(1)-Fe(30)/MCM-41 and Fe(30)/MCM-41. The hydrogen yield of Pt(1)-Fe(30)/MCM-41 was 3.2 times higher than that of Fe(30)/MCM-41. When 1 wt% of Pt was added to Fe(30)/MCM-41(Mobil Composition of Matter No. 41), the atomic percentage of Fe2p increased from 13.39% to 16.14% and the core Fe2p1/2 electron levels of Fe0 and Fe2+ chemically shifted to lower energies (0.2 eV and 0.1 eV, respectively) than those of Fe(30)/MCM-41. The Fe, Pt, Si, and O nanoparticles were uniformly distributed on the catalyst surface, and the average iron particle sizes of the Pt(1)-Fe(30)/MCM-41 and Fe(30)/MCM-41 were about 33.4 nm and 58.5 nm, respectively. This is attributed to the uniform distribution of the nano-sized iron particles on the MCM-41 surface, which was due to the suitable metal-carrier interaction (SMCI) between Fe, Pt, and MCM-41 and the high reduction degree of Fe due to the spillover effect of H2 from Pt to Fe. Pt(1)-Fe(30)/MCM-41 produced multiwalled CNTs and bamboo-shaped CNTs with high crystallinity and graphitization degree using the tip-growth mechanism, with an ID/IG ratio of 0.93 and a C(101)/C(002) ratio of 0.64.

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.

Catalytic decomposition of sulphuric acid in Iodine-Sulphur and Hybrid-Sulphur processes for Hydrogen production: Estimation of effectiveness factor of catalyst

High endothermic heat of SO3 decomposition reaction (ΔHR∼+98 kJ mol−1) can lead to significant thermal gradients (lower temperatures) inside the catalyst particle, depending up on mass diffusion, heat conduction and intrinsic reaction kinetics in the particle. The lower catalyst effectiveness (due to thermal gradients) leads to lower decomposition conversions in Packed Bed Reactors (PBR), which has to be maximized. In this study, a multi-scale model (Double Porosity Model, DPM) is used for the estimation of non-isothermal effectiveness factor (η) of Cr-Fe2O3 catalyst types; less porous pellet and porous foam types. η obtained using DPM (foam∼0.249 and pellet∼0.147) are found to be in good agreement with experimental data and also with the results of derived model (Weisz model). Further, effect of porosity and size/diameter on η are studied and obtained the optimum porosity required for maximum η. The present study is useful for estimation and optimization of non-isothermal η of catalysts.

Precision Engineering of Nanorobots: Toward Single Atom Decoration and Defect Control for Enhanced Microplastic Capture

AbstractNanorobots are being received with a great attention for their move‐sense‐and‐act capabilities that often originate from catalytic decomposition of fuels. In the past decade, single‐atom engineering has demonstrated exceptional efficiency in catalysis, energy‐related technologies, and medicine. Here, a novel approach involving point defect engineering and the incorporation of platinum (Pt) single atoms and atomic level species onto the surface of titanium dioxide nanotubes (TiO2‐NT)‐based nanorobots is presented and its impact on the propulsion capabilities of the resulting nanorobots is investigated. The achievement of point defect engineering is realized through the annealing of TiO2‐NT in a hydrogen atmosphere yielding to the point‐defect decorated nanotube (TiO2‐HNT) nanorobots. Subsequently, the atomic level Pt species decorated TiO2 nanotube (TiO2‐SA‐NT) nanorobots are achieved through a wet‐chemical deposition process. Whereas TiO2‐SA‐NT nanorobots showed the highest negative photogravitaxis when irradiated with ultraviolet (UV) light, TiO2‐HNT nanorobots reached the highest velocity calculated in 2D. Both TiO2‐HNT and TiO2‐SA‐NT nanorobots demonstrated a pronounced affinity for microplastics, exhibiting the capability to irreversibly capture them. This pioneering approach utilizing point‐defect and atomic level Pt species nanorobotics is anticipated to pave the way for highly efficient solutions in the remediation of nano‐ and microplastics and related environmental technologies.

In-situ electrochemical passivation for constructing high-voltage PEO-based solid-state lithium battery

Polyethylene oxide (PEO) is one of the promising substrates for polymer solid electrolyte. However, when coupled with high energy density nickel-rich layered cathode materials, PEO faces the risk of catalytic decomposition by delithium nickel-rich materials. In this work, the in-situ electrochemical passivation strategy is employed to obtain high voltage PEO-based solid-state lithium battery. Trace commercial liquid electrolyte was added on the surface of LiNi0.8Co0.1Mn0.1O2 (NCM811) electrode, and liquid electrolyte is prior to PEO electrolyte to react with the cathode during charge/discharge process, leading to the formation of cathode-electrolyte interface (CEI) layer. The CEI layer avoids the direct contact between PEO and NCM811, thus effectively prevents PEO from being decomposed by NCM811 under high voltage. As a result, the optimized NCM811||PEO||Li battery displays enhanced electrochemical performance, especially cycling performance. This simple but effective strategy not only simplifies the manufacturing process, but also has instructional guidance for high-voltage PEO-based battery.

Chemical looping-based catalytic CH4 decomposition and successive coke gasification with CO2 on ordered mesoporous NiMCeOx (M = Co, Zr, La)

Highly ordered mesoporous NiLaCeOx mixed metal oxides were investigated as effective catalysts for the chemical looping-based dry reforming of methane (CH4) with carbon dioxide (CO2) (CL-DRM). This catalyst exhibited an excellent catalytic activity and stability in the decomposition of CH4 to form H2 with surface carbons subsequently activated by CO2 via reverse Boudouard reaction to form CO. Among the NiMCeOx catalysts with various promoter (M = Co, Zr, or La), the optimal NiLaCeOx catalyst preserved its original highly ordered mesoporous structures, leading to the higher dispersion of smaller Ni nanoparticles. This was attributed to the stronger Ni-Ce interactions facilitated by the La2O3 metal oxide promoter. The NiLaCeOx demonstrated a higher rate of H2 formation and successive CO production in the CL-DRM reaction, resulting in a H2/CO ratio above 1.0. Additionally, the NiLaCeOx catalyst exhibited superior structural stability over 5 cyclic CL-DRM reactions for CH4 decomposition (>85 %) and CO2 activation (>45 %), with minimal deposition of cokes.

Nickel perovskite catalysts for ammonia decomposition: DFT calculations and microreaction kinetics

Combining policy guidance, catalyzing ammonia decomposition to produce hydrogen is a new concept for hydrogen energy supply. Alkaline carriers can effectively improve the ammonia decomposition activity on the catalyst by adjusting the dispersion of nickel (Ni) and controlling the size of Ni. However, the activity of Ni-based perovskite catalysts does not seem to be entirely affected by the above factors. Exploring the mechanism of Ni and perovskite alkaline carrier surfaces through theoretical calculations provides deeper theoretical guidance for ammonia (NH3) decomposition. This study uses periodic density functional theory calculation methods to investigate the reaction paths and energy distribution of monomeric ammonia and dimeric ammonia on a nickel-doped barium zirconate (Ni/BaZrO3) catalyst. Molecular dynamics simulations, Bader charge analysis, and density of states assist in understanding the adsorption states of NH3 and the catalytic decomposition mechanism. The energy barriers for N-H bond breaking and nitrogen generation reactions of Ni clusters loaded on the BaZrO3 surface (Ni4/BaZrO3) were compared and analyzed. The results show that Ni/BaZrO3 is more conducive to ammonia decomposition, with a maximum reaction barrier of 0.90 eV. The catalytic activity of the catalyst under oxygen vacancy conditions was further examined. By comparing the mechanisms of dimeric ammonia decomposition on the clean catalyst surface and the oxygen vacancy catalyst surface, it was found that the presence of oxygen vacancies facilitates ammonia decomposition, but Ni doping provides more effective assistance for N-H bond breaking. The rate constant for ammonia decomposition was calculated using transition state theory. This work not only provides theoretical references for the decomposition mechanism of NH3 in Ni-based perovskite materials but also provides kinetic data for the kinetic modeling of NH3 decomposition.

Facile Synthesis of Copper Telluride Nanoparticles as a Robust Nanoenzymatic Catalyst for Intrinsic Peroxidase‐Like Activity

AbstractCopper telluride nanoparticles are classified as the family of metal chalcogenides and were synthesized using a simple solvothermal method using a new source of telluride, ditelluride diphenyl. The characterized techniques revealed that the atomic composition of copper tellurides is Cu2Te and particles are spherical. This study is greatly examined by different designed experiments for the proof of the intrinsic peroxidase‐like activity of copper telluride nanoparticles and its effectiveness in a variety of similar structures. Cu2Te nanoparticles can convert peroxidase substrates (TMB and OPD) to colored products in the presence of H2O2. In addition, the as‐prepared nanoparticles have the potential to oxidize DPPH and ABTS substrates. Michaelis–Menten constant KM value for TMB and H2O2 was found to be 12 mM and 0.60 mM for H2O2 and the Vmax value of the Cu2Te was found to be TMB and H2O2 was 2.50×10−7 and 0.82×10−8 MS−1. These data are found to be almost comparable with natural peroxidase HRP and other artificial enzymes reported in the literature. The natural peroxidase‐like activities of Cu2Te nanoparticles originated from the catalytic decomposition of H2O2 into ⋅OH radical, which was confirmed from the ESR spin‐trapping technique and using a fluorescence probe, terephthalic acid.

Hydrogen generation based on a gel-like formate system with a palladium catalyst

Catalytic formate decomposition under mild conditions is a promising strategy for hydrogen production as an efficient hydrogen carrier. Most of previous studies performed formate decomposition for hydrogen generation in liquid phase or using formate as a promoter for formic acid decomposition, which exhibits relatively low hydrogen energy density by mass. Here, we reported a gel-like formate system for catalytic hydrogen generation under mild conditions. A H2 yield of 100% with hydrogen energy density by weight of 2.38 wt% was achieved, and the palladium catalyst shows high stability and recyclability for KCOOH gel decomposition. Moreover, the constructed gel-like formate filled in an aluminum cylinder could continuously and steadily supply hydrogen to a 12V/35W fuel cell to drive a LED display. This work may provide a new thought for safe hydrogen storage and production system for hydrogen energy usage in the future.

Novel magnetite/persulphate/ozone hybrid system for catalytic degradation/ozonation of sunset yellow dye from wastewater

Food dyes with a diverse set of colorants stimulate appetite and enhance aesthetic charm of food on table but at the same time these dyes contaminate the aquatic and biological ecosystems due to their cytotoxic and carcinogenic potentials. Herein, we report magnetite catalyzed removal of sunset yellow dye from water through catalytic degradation and ozonation. The magnetite catalyst revealed about 83% catalytic degradation and 92% catalytic ozonation performance toward sunset yellow dye at 100 and 25 min, respectively. Furthermore, the persulphate/magnetite/O3 hybrid system revealed superior performance compared to the persulphate/magnetite under identical conditions. Kinetic studies revealed that the dye degradation data followed second-order kinetics, suggesting that the dye removal process is physicochemical in nature. This study further demonstrates that the persulfate/magnetite/O3 hybrid system can efficiently decompose sunset yellow dye in aqueous solution compared to the Fenton’s reagent and simple catalytic decomposition processes which is attributed to its unique structural features.

Facile Synthesis of N-doped Co3O4 Catalyst for Catalytic Decomposition of N2O under Simulated Real Tail Gases

Facile Synthesis of N-doped Co3O4 Catalyst for Catalytic Decomposition of N2O under Simulated Real Tail Gases

Suppressing the damage of deposited Mn(II) ions to graphite anode in lithium‐ion batteries by electrolyte additive agent and positive material coating

AbstractSEM and EDS techniques are carried out to demonstrate the variation of morphology and chemical compound on the surface of graphite anode, which suggest a well‐accepted concept that the manganese ions have serious influence on the reversible capacity fade of graphite anode in lithium ion batteries. Based the main chemical compounds of the inorganic layer on the graphite surface, the evolution steps of graphite structure damaged by Mn ions are derived. Although the amount of deposited manganese ions is small, these play an important role in the catalytic decomposition of the electrolyte. Moreover, Raman analysis shows that the structure of the graphite anode becomes irregular at initial SEI formation cycles and tends to be stable at subsequent cycles. This structure variation is probably generated from the manganese ion deposition and the solid electrolyte interphase (SEI) film formation. According to the capacity tests, the cycling performance of NCM811/graphite lithium‐ion batteries could be improved 50% by FEC additive and B2O3 surface coating. FEC additive maybe benefit graphite forming a stable SEI film in the early stages of cycling to suppress the damage of Mn2+ ions, then improving the cycling performance.

High-temperature treatment promotes N2O decomposition over Fe-impregnated Al-rich SSZ-13 zeolites

Fe/SSZ-13 catalysts were prepared via the impregnation method and calcined at different temperatures. The catalytic activity of Fe/SSZ-13 catalysts in the N2O catalytic decomposition reaction was greatly influenced by the calcination temperature. As the calcination temperature rose to 800 °C, the catalytic efficiency of N2O decomposition performance gradually improved. Nevertheless, if the temperature of calcination exceeded 800 °C, the efficiency diminished as a result of the disintegration of the molecular sieve framework. Various characterization methods were used to investigate the impact of calcination temperature on iron species. The results showed that the high-temperature treatment could promote the dispersion and reduction of Fe2O3 particles on the catalyst surface, which led to the generation of more active species (such as Fe3O4 and FeO) and provided more oxygen vacancies which favored the N-O breakage, thus improving the N2O decomposition activity.

Mechanism on CMD reaction regulated by supports and promoters of Fe-based catalysts

Methane cracking technology for low-carbon energy conversion to produce hydrogen is a key technical approach in the pursuit of fossil energy decarbonization. Catalytic methane decomposition (CMD) is a process that accomplishes the fundamental removal of carbon from fossil energy without oxygen, producing high-quality carbon-based materials and H2. The functionality of supports and promoters was investigated using inorganic metal oxide support Al2O3, supported active metal Fe, and cocatalyst K. The results show that the Al2O3–Fe catalyst achieves the highest CH4 conversion of 65% at 850 °C, with a gas-phase H2 yield of 1189.72 mmol/gFe within 3 h, and a solid-phase carbon yield of 6.32 g/gFe, significantly higher than at 750 °C. The Al2O3–Fe–K catalyst achieves a methane conversion rate of 66.28% at 850 °C for 1.5 h, exhibiting relatively fast deactivation. The Al2O3–Fe catalyst catalyzes the formation of carbon nanotubes (CNTs) through methane cracking, resulting in mainly 'chain-locked' morphology. The promoter K acts on the surrounding metal clusters to influence the dispersion of active metal. The Al2O3–Fe–K catalyst is more favorable for the production of 'bamboo-shaped' carbon nanotubes, suggesting that K has a more significant impact on shaping the CNTs' products.

Effect of Ni/SiO2 catalyst preparation method on methane decomposition and CO2 gasification cycles

Catalytic methane decomposition is a promising reaction to produce CO2-free hydrogen from methane-rich feedstock with solid carbon as a by-product. Significant research conducted on this reaction to find ways to manage and utilize this solid carbon. In this work, the methane decomposition reaction is followed by Reverse Boudouard Reaction using CO2 feedstock to convert the solid carbon to carbon monoxide, which is a valuable starting component for many chemical applications. Realizing this promising concept would require a catalyst that is efficient for both reactions. Herein, we explored the potential of using solution combustion synthesis (SCS) to make a 5 wt% of Ni supported SiO2 catalyst and benchmarked it versus the conventional impregnation method. The catalyst prepared by SCS showed an improved performance at different temperatures, space velocities, and catalyst pellet sizes. The SCS catalyst successfully completed five repeated cycles reaching up to 38.1 h of stable time on stream operation, whereas the impregnated catalyst was not able to complete the second testing cycle with only 14 h of time on stream operation. A thorough characterization using XRD, H2 and O2 TPR, TEM, SEM, XPS, and Raman spectroscopy were conducted to provide an adequate explanation for the observed performances for both catalysts. The Ni nanoparticles size and distribution, the strength of the metal support interaction, and the nature of graphitic carbon were the key factors affecting the catalytic performance. Insights on how to make an optimal catalyst for this promising process is identified which is a step forward toward making separated H2 and CO streams from methane feedstock and CO2, respectively.