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The plane exposure of support vitally affects the catalytic performance of the catalyst. In this work, CeO2 nanorods ((1 1 0) plane exposure), nano-octahedrons ((1 1 1) plane exposure) and nano-cubes ((1 0 0) plane exposure) were prepared as the supports of Pt/CeO2 samples to investigate the effect of CeO2 plane exposure on total toluene oxidation. Characterizations reveal that the (1 1 0) plane of CeO2 is more helpful to the dispersion of Pt species, followed by (1 1 1) face. The improved dispersion of Pt species can enhance the metal-supports interaction, which promotes the electron transfer of CeO2 carrier to Pt nanoparticles and the adsorption-activation of O2, thereby facilitating the total oxidation of toluene via the Langmuir–Hinshelwood (L-H) mechanism. Therefore, Pt/CeO2-r (nanorods) sample expresses the most excellent catalytic performance of toluene oxidation. Finally, the procedure of toluene total oxidation was studied by in-situ DRIFT. We expect that this work can contribute to the development of an effective sample for the decomposition of volatile organic compounds (VOCs).

No consensus has been reached on the role of reducible and irreducible supports on the reaction pathway of CO oxidation over supported metal catalysts. Here, colloidal ligand-free Pt nanoparticles were deposited on Al2O3 and CeO2 to investigate the support effect in CO oxidation by in situ diffuse reflectance Fourier-transform infrared spectroscopy (DRIFTS) and mass spectrometry (MS). On Pt/Al2O3, the carbonate-like intermediates accumulate and do not decompose to CO2 at the ignition temperature (150 °C) or above; the conversion of CO to CO2 follows classic Langmuir−Hinshelwood (L–H) mechanism with direct reaction of CO and O2 on Pt. Whereas for Pt/CeO2, the CO conversion to bidentate carbonate (b-CO32−) species followed by decomposition to CO2 is a main reaction pathway leading to its high reactivity at low temperature (75 °C). CeO2 facilitates the activation of oxygen to produce the carbonate-like intermediates and further decomposition to CO2, which resulted in a lower ignition temperature.

The cognition of active sites in the Ni-based catalysts plays a vital role and remains a huge challenge in improving catalytic performance of low temperature CO2 dry reforming of methane (LTDRM). In this work, typical catalysts of SiO2 and γ-Al2O3 supported Ni and Ni-Ce were designed and prepared. Importantly, the difference in the chemical speciations of active sites on the Ni-based catalysts is revealed by advanced characterizations and further estimates respective catalytic performance for LTDRM. Results show that larger [ Ni n 0 ] particles mixed with [Ni-O-Sin]) species on the Ni/SiO2(R) make CH4 excessive decomposition, leading to poor activity and stability. Once the Ce species is doped, however, superior activity (59.0% CH4 and 59.8% CO2 conversions), stability and high H2/CO ratio (0.96) at 600 °C can be achieved on the Ni-Ce/SiO2(R), in comparison with other catalysts and even reported studies. The improved performance can be ascribed to the formation of integral ( [ Ni n 0 ] -[CeIII-□-CeIII]) species on the Ni-Ce/SiO2(R) catalyst, containing highly dispersed [ Ni n 0 ] particles and rich oxygen vacancies, which can synergistically establish a new stable balance between gasification of carbon species and CO2 dissociation. With respect to Ni-Ce/γ-Al2O3(R), the Ni and Ce precursors are easily captured by extra-framework Aln-OH groups and further form stable isolated ( [ Ni n 0 ] -[Ni-O-Aln]) and [CeIII-O-Aln] species. In such a case, both of them preferentially accelerate CO2 adsorption and dissociation, causing more carbon deposition due to the disproportionation of superfluous CO product. This deep distinguishment of chemical speciations of active sites can guide us to further develop new efficient Ni-based catalysts for LTDRM in the future.

The fast decomposition of peroxides (M2O2, where M = H+, Li+) at room temperature has gained increased attention given its relevance, from propulsive systems to metal-O2 conversion batteries. This study describes, by a rational design of experiment, the influence of selected parameters such as: pH, initial concentration of K2CO3, precipitate aging, precipitate washing, and thermal treatment for the hydrotalcite co-precipitation, characterizing it for each synthesis variable. The results show that hydrotalcites can efficiently be converted in Co-Mn-Al spinels and as a result, a new highly active Co2Mn0.5Al0.5O4 spinel oxide was synthesized after thermal treatment. Its activity and mechanical resistance were tested in a micro-thruster reactor where it showed total decomposition (> 98%) of H2O2 and in a Li-O2 battery, with increased cyclability, been able to reduce the charging potential in ~200 mV. These encouraging results enhance the importance not only of this class of material, but also, the importance of robust synthesis methodologies for reproducible results.

In this study, several noble zeolites (SA-600A)-based catalysts supported with RuCl3.nH2O and LiOH·H2O materials were investigated for H2 production from NH3 decomposition. The synthetic catalysts were simultaneously prepared at different supported materials mixing ratios. The effect of initial mixing of Li and Ru on catalyst performance compared to simultaneous mixing was studied. All catalysts were tested for hydrogen production from NH3 decomposition at atmospheric pressure, temperature range of 200–670 oC, and gas hourly space velocity (GHSV) of 3000 h−1. It was found that the simultaneous and initial mixing of Li and Ru has the same NH3 decomposition results. The zeolite-based catalyst was enhanced with the Ru supported material mixing ratio increase. Among all the synthetic catalysts the catalyst type of 40 g (SA-600A)/5 g RuCl3.nH2O/3 g LiOH·H2O) showed the highest catalyst activity. The catalyst with a mixing ratio of 40 g (SA-600A)/5 g RuCl3.nH2O/3 g LiOH·H2O) was registered the peak NH3 conversion 99.87% at lower temperature of 490 °C.

The phosphorus-doped carbon materials as one of novel carbon catalysts towards the hydrogen evolution reaction (HER) have attracted considerable attention over the past years. However, the role of C-P species palyed in the HER activity is still not clear up to now. Phosphorus-doped carbon nanotubes (P-CNTs) were prepared by chemical vapor deposition and annealed at 900, 1000 and 1200 ℃ to remove all or parts of phosporus species, resulting in four samples with different proportions of graphite-, pyridine- and pyrrole-like P species. The correlations between their HER activity and the contents of three types of P species were investigated. Results showed that the content of graphite-like P decreased with the annealing temperature and no graphite-like P was retained at 1200℃. The HER activity increased with the annealing temperature and the one annealed at 1200 ℃ had the highest HER activity in an acid medium with an overpotential of 0.266 V at a current density of 10 mA/cm−2. Density functional theory calculations revealed that the pentagon- and nine-membered ring defects formed by the destruction of graphite-P species contributed mainly to the HER activity, which gave a deep insight into the active sites for HER.

Phosphogypsum is a solid waste sourced from the wet-process phosphoric acid industry, which causes severe environmental damages. Its utilization was limited by its high decomposition temperature and high energy consumption. Herein, an Fe-P slag, which is a solid waste that mainly comprises iron phosphide (FeP) and diiron phosphide (Fe2P), can dramatically decrease the decomposition temperature of phosphogypsum. It was found that the Fe-P slag and CaSO4 can react as shown in the following reaction equation: 2Fe1.5P+3CaSO4+6CO2→Ca3(PO4)2+Fe3O4+3SO2+6CO. Its reaction mecha-nism was further determined using the thermodynamic method. It was found that CaS was the key intermediate for this reaction. The CaSO4 conversion for this method can reach approximately 97% under the optimized roasting conditions: the molar ratio between Fe1.5P and CaSO4 of 2:3, roasting temperature of 900 °C, a roasting time of 8 h.

Exploring an alternative strategy with high efficiency and low cost to abate formaldehyde (HCHO) in indoor environment, is of increasing significance for people’s health. CeO2 catalysts prepared by hydrothermal, precipitation and calcination methods were investigated for HCHO removal at ambient temperature. It is found that indoor fluorescent light visibly boosts the catalytic performance of CeO2 catalysts for HCHO decomposition at ambient temperature. Among the CeO2 catalysts, CeO2 prepared from hydrothermal method (CeO2-H) exhibits a superior catalytic performance and an excellent durability by eight recycle times. Based on the characterization and analysis, the excellent catalytic performance of CeO2-H is mainly contributed by its abundance of surface oxygen vacancies, and photogenerated electrons and hole activated by fluorescent light. This work shows a potential practicability in HCHO pollution elimination by taking full advantage of the existing lighting in indoor environments.

This study investigated catalytic decomposition and mass transfer of aqueous ozone promoted by Fe-Mn-Cu/γ-Al2O3 (Cat) in a rotating packed bed (RPB) for the first time. The results showed that the value of the overall decomposition rate constant of ozone (Kc) and overall volumetric mass transfer coefficient (KLa) are 4.28×10−3 s−1 and 11.60×10−3 s−1 respectively at an initial pH of 6, β of 40, C O 3 ( g ) of 60 mg·L−1 and QL of 85 L·h−1 in deionized water, respectively. Meanwhile, the Kc and KLa values of Fenhe water are 0.88×10−3 s−1 and 2.51×10−3 s−1 lower than deionized water, respectively. In addition, the Kc and KLa values in deionized water for the Cat/O3-RPB system are 44.86% and 47.41% higher than that for the Cat/O3-BR (bubbling reactor) system, respectively, indicating that the high gravity technology can facilitate the decomposition and mass transfer of ozone in heterogeneous catalytic ozonation and provide some insights into the industrial wastewater.

In recent years, MoS2 catalyzed/cocatalyzed Fenton/Fenton-like systems have attracted wide attention in the field of pollution control, but there are few studies on the effect of H2O2 feeding way on the whole Fenton process. Here, we report a new type of composite catalyst (MoS2-Fex) prepared in a simple way with highly dispersed iron to provide more active sites. MoS2-Fex was proved to possess selectivity for singlet oxygen (1O2) in effectively degrading sulfadiazine with a wide pH adaptability (4.0∼10.0). Importantly, the mechanism of the interaction between H2O2 and MoS2 on the Fenton reaction activity was revealed through the combination of experiment and density functional theory (DFT) calculations. Compared to the traditional “a large amount for one time” feeding way of H2O2, the “small amount for multiple times” of H2O2 feeding way can increase the degradation rate of sulfadiazine from 36.9% to 91.1% in the MoS2-Fex heterogeneous Fenton system. It is demonstrated that the “small amount for multiple times” of H2O2 feeding way can reduce the side reaction of decomposition of H2O2 by MoS2 and effectively improve the utilization rate of H2O2 and the stability of MoS2-Fex. Compared with Fe2O3-based Fenton system, MoS2-Fex can significantly save the amount of H2O2. Compared with nano-iron powder, the formation of iron sludge in MoS2-Fex system was significantly reduced. Furthermore, long-term degradation test showed that the MoS2-Fe75/H2O2 system could maintain the effectiveness of degrading organic pollutants for 10 days (or even longer). This study has a guiding significance for the large-scale treatment of industrial wastewater by improved Fenton technology in the future.

Formic acid is one of the key components in green chemistry being involved in energy storage, production of chemical intermediates and fuel components. Therefore the knowledge of its stability is of crucial importance and a systematic study of its decomposition is needed. The kinetics of formic acid decomposition to hydrogen and carbon dioxide was investigated in a laboratory-scale fixed bed reactor at 150–225 °C and atmospheric pressure. Palladium nanoparticles deposited on porous active carbon Sibunit were used as the heterogeneous catalyst. The catalyst was characterized by nitrogen physisorption and high-resolution transmission electron microscopy. The average palladium nanoparticle size was 5–6 nm. The impacts of mass transfer resistance and formic acid dimerization were negligible under the reaction conditions. Prolonged experiments revealed that the catalyst had a good stability. Hydrogen and carbon dioxide were the absolutely dominant reaction products, whereas the amounts of carbon monoxide and water were negligible. The experimental data were described with three kinetic models: first order kinetics, two-step adsorption-reaction model and multistep adsorption-decomposition model of formic acid. The multistep model gave the best description of the data.

Although the photovoltaic efficiency of organic solar cells (OSCs) has exceeded 17%, poor lifetime excludes OSCs from practical use. In particular, UV rays in sunlight may cause the decomposition o...

CO2 hydrogenation to methanol was investigated over CuZnIn/MZrOx (M = La, Y or Ti) catalysts at 20 bar and at 225 °C with the purpose to elucidate the effects of the metal oxide promoter for ZrO2 and InOx for CuZnOx on reaction scheme of product formation, catalyst activity and product selectivity. Although the additives do not affect the overall scheme of product formation, they are relevant for the rates of direct CO2 conversion into methanol or CO and of methanol decomposition to CO and H2. This is due to their influence on dispersion of CuOx and the strength of basic sites for CO2 adsorption. Highly dispersed CuOx species are essential for CO2 conversion but not for methanol selectivity. The selectivity is improved over polymerized CuOx with strong basicity. This catalyst property can be controlled through promoting of (i) ZrO2 with La2O3/Y2O3 or (ii) CuZnOx with InOx. The latter promoter is crucial for hindering the undesired methanol decomposition to carbon monoxide.

Direct synthesis of graphene on insulating substrates is highly desirable for practical applications. Herein, we present a new fabrication method for graphene on quartz which enables the direct growth of high-quality and large-scale graphene films with no metal involved. The growth rate of graphene on insulating substrates was typically extremely slow due to the low catalytic activity and the slow diffusion speed of carbon species on them. Thus, an extra catalyst is required. Instead of metal elements, such as Cu, Ni, and Ga, highly-defective graphene films were applied as the catalyst for methane decomposition. The key feature of our approach is that carbon itself was used as the catalyst for graphene fabrication, which completely avoided the contamination of other elements. As a result, the growth rate of graphene films increased significantly compared to the conventional CVD method. The excellent quality of graphene glass was verified by a series of experimental characterization and the fabrication of a transparent heating device without any transfer process. In addition, the energy barrier of the decomposition of methane was explored using the first principles calculation, which further confirmed the catalytic behavior of highly-defective graphene films.

A highly efficient and stable hydrotalcite-derived Cu-MgAlO catalyst was developed for the partial oxidation of cyclohexane with molecular oxygen. The physical-chemical properties of Cu-MgAlO catalysts were studied, and the results indicated that the copper component had been successfully introduced into the hydrotalcite unit layer structure. The catalytic reaction results showed that copper as the active species could activate C-H bond and effectively promote the decomposition of cyclohexyl hydroperoxide (CHHP) to KA oil. 8.3% of cyclohexane conversion and 82.9% of selectivity for KA oil were obtained over 9%Cu-MgAlO catalyst at 150 °C with 0.6 MPa of oxygen pressure for 2 h. Especially, its catalytic performance was still stable after five runs.

Evaluation and understanding of the thermal behavior of polymers is crucial for many applications, e.g., polymer processing at relatively high temperatures, and for evaluating polymer-polymer miscibility. In this study, the differences in the thermal behavior of poly(vinyl alcohol) (PVA) raw powder and physically crosslinked films were investigated using various methods, such as thermogravimetric analysis (TGA) and derivative TGA (DTGA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Various strategies were adopted, e.g., film casting from PVA solutions in H2O and D2O and heating of samples at carefully selected temperatures, in order to provide insights about the structure-properties relationship. It was found that the physically crosslinked PVA film presents an increased number of hydrogen bonds and increased thermal stability/slower decomposition rate compared to the PVA raw powder. This is also depicted in the estimated values of specific heat of thermochemical transition. The first thermochemical transition (glass transition) of PVA film, as for the raw powder, overlaps with mass loss from multiple origins. Evidence for minor decomposition that occurs along with impurities removal is presented. The overlapping of various effects (softening, decomposition, and evaporation of impurities) has led to confusion and apparent consistencies, e.g., from the XRD, it is derived that the film has decreased crystallinity, and apparently this is in agreement with the lower value of heat of fusion. However, the heat of fusion in this particular case has a questionable meaning.

Weak thermal stability and low-burning resistance of the rigid polyurethane foams are the classic problems in the usage of them. Therefore, it is required to improve these problems of the foams while reducing the cost of production. This study investigated the effects of dolomite (DOL) and intumescent flame retardant (IFR) system on thermal and combustion behaviors of rigid polyurethane foams (RPUFs). For this purpose, DOL (5, 10, and 15 wt%) and DOL/IFR (5/5, 10/5, and 5/10 wt%) combinations were added into RPUFs. Thermogravimetric analyses were performed to investigate the thermal decompositions of the foams and the thermal conductivity measurements were performed to examine the effects of DOL and DOL/IFR additions on the thermal insulation properties of the foams. Cone calorimeter and UL 94 tests were performed to investigate the fire resistances of the foams. The test results showed that up to 15 wt% DOL could be incorporated into the rigid polyurethane foams as filler without any problems in the foam productions, and the thermal and the combustion behaviors of the foams were slightly enhanced. In addition, it was determined that IFR should be used to improve the thermal stability and the fire resistance of the DOL added foams. Among DOL/IFR combinations, 5 wt% DOL and 10 wt% IFR addition satisfied the best performance in terms of the thermal stability and the fire resistance with reducing the smoke, CO, CO2 and NO emissions. In general, the additions of DOL and IFR slightly increased the thermal conductivity coefficients of the foams. © 2023 Wiley Periodicals LLC.

Porous carbon fibers catalysts have been prepared by electrospinning of Alcell lignin, a green carbon precursor, which could be obtained as by-product in wood-to-ethanol biorefineries. The addition of H3PO4, a well-known chemical activation agent, to the electrospinning lignin solutions, at different mass ratios and the use of different carbonization temperatures, between 500 and 1600 °C, were analyzed in order to obtain carbon fibers with a large variety of porosity and chemical surface properties. Isopropanol decomposition was used as a catalytic test. Phosphorus-containing carbon fibers showed acid character and high catalytic activity, achieving propylene selectivity of 100 % under inert atmosphere. However, the use of air atmosphere increases the isopropanol conversion but produces the formation of acetone, via oxidative dehydrogenation, at low temperatures (∼20 %). Ethanol and methanol decomposition were also evaluated in air stream for the most active phosphorus-containing carbon catalyst, showing improved alcohol conversions with minimal gasification of the carbon fibers. These results confirmed that phosphorus-containing carbon fibers prepared by electrospinning of lignin solutions were excellent catalysts for alcohol dehydration reactions.

An effective decontamination method for soils remediation is a long-standing challenge. Herein, hydrogen peroxide (H2O2) was spontaneously produced in thin films generated by evaporating almost all the water. H2O2-sensitive test strips and oxidation of 2-hydroxybenzophenone to 2-hydroxyphenyl benzoate confirmed the generation of H2O2. Experiments in which reaction time and temperature were varied and established dependence of H2O2 production on the long-lasting thin films. H2O2 production was independence of irradiation and oxygen from air or dissolved oxygen. Spin-trapping probe experiments suggested that electric fields at the thin interfacial films enabled OH- to hydroxyl radicals and further recombination to H2O2. As a proof-of-principle experiment, perfluorooctanoic acid (PFOA) was effectively degraded on the thin films without catalysts and UV irradiation could further facilitate the degradation. A degradation mechanism was proposed involving the PFOA radicals on thin interfacial films and the subsequent decomposition of the radicals with successive loss of CF2. These findings have important implications for the development of decontamination method for soils remediation based on thin films, because thin film formats are ubiquitous at the surface of soils and when aerosols falling onto a substrate.

In this study, the effect of unintentional nitrogen incorporation on n-type doping of β-Ga2O3 films grown by plasma-assisted molecular beam epitaxy has been demonstrated. The nitrogen atoms, with a concentration as high as 2×1019 cm-3, are confirmed to originate from the decomposition of the pyrolytic boron nitride (PBN) crucible in the plasma source. These atoms act as acceptors in β-Ga2O3 and severely compensate the Si-donors, thus, hindering the generation of n-type β-Ga2O3. Instead, a quartz (SiO2) crucible free of nitrogen atom can overcome this issue, leading to the successful generation of n-type β-Ga2O3 with tunable electron concentration in the range 5.0×1016-2.6×1019 cm-3.

Selective catalytic reduction (SCR) of NOx with NH3 has been widely used for NOx emission control, but commercial catalysts inevitably suffer severe deactivation in SO2-containing stack gases at low temperatures because the ammonium bisulfate (NH4HSO4, ABS) formed in SCR blocks the surface active sites. We resolve this issue by developing a TiO2-supported single-atom Mo catalyst (Mo1/TiO2) that decomposes ABS at ∼225 °C, far lower than the dew point of ABS (∼260 °C). Single Mo atoms paired with the neighboring surface Ti atoms function as Mo–Ti acid–base dual sites, which respectively adsorb the NH4+ and HSO4− of ABS. After the oxidation of NH4+ by surface lattice oxygen on the Mo sites, electrons left behind on the dual sites are localized around the Fermi level, which allows them to transfer to the adsorbed HSO4− on the Ti sites, thus releasing SO2 at low temperatures. The Mo1/TiO2 catalyst with Mo–Ti acid–base dual sites enables the decomposition of ABS at low temperatures, and thus this work provides a way to effectively control NOx emission particularly from industrial boilers.

Antioxidants scavenge free radicals and may help prevent disease. However, due to poor stability, continuous intake is required. This study investigates the ability of cyclodextrin inclusion to improve the stability of the novel antioxidant edaravone. Kinetic models of cyclodextrin protection against edaravone oxidative decomposition were assessed and the data obtained was analyzed using Hanes–Woolf plots and Scatchard plots. In addition, complexation was analyzed using phase-solubility diagrams. The results show that cyclodextrin inclusion can control the oxidation rate of antioxidant molecules such as edaravone. This paper also demonstrates a substantial variation in the quantitative stability constant when calculated using different methods. This observation is relevant to determining complexation during the many and varied applications of cyclodextrins. The study establishes mechanisms to enhance the stability of antioxidants, which in turn may be useful to improve their bioavailability and may have translational implications in future.

Charge-transfer (CT) complexes of 4,4′-bis(9H-carbazol-9-yl)-1,1′-biphenyl (CBP) and three acceptors emitted cyan, green, and orange fluorescence, and lower LUMO energy levels of the acceptors prom...

A first-principles microkinetic model is developed to investigate low-temperature ammonia assisted selective catalytic reduction (NH3-SCR) of NO over Cu-CHA. The reaction proceeds over NH3-solvated Cu-sites by the formation of H2NNO and HONO, which decompose to N2 and H2O over Bro nsted acid sites. Non-selective N2O formation is considered by H2NNO decomposition over the Cu-sites. The adsorption of NH3 at oxidized Cu-sites is found to inhibit the reaction at low temperatures by hindering NO adsorption. For the reactions, we nd positive reaction orders with respect to NO and O2, whereas the reaction order with respect to NH3, is negative. The reaction orders and the obtained apparent activation energy are in good agreement with experimental data. A degree of rate control analysis shows that NH3-SCR over a pair of Cu(NH3)+2 is mainly controlled by NO adsorption below 200 C, whereas the formation of HONO and H2NNO becomes controlling at higher temperatures. The successful formulation of a first-principles microkinetic model for NH3-SCR rationalizes previous phenomenological models and links the kinetic behaviour with materials properties, which results in unprecedented insights in the function of Cu-CHA catalysts for NH3-SCR.

The development of highly active and durable catalysts for H2 production through CH4 decomposition process is still a great challenge. In this study, CeO2 and CeO2–SiO2 supported bimetallic Ni–Mo catalysts were produced and examined for CH4 decomposition at 700 °C. The unreacted and reacted catalytic materials were characterized by XRD, BET, H2-TPR, TGA-DTA, TEM, and Raman spectroscopy techniques. The collected data illustrated that the inclusion of SiO2 to CeO2 support in Ni–Mo/CeO2–SiO2 catalyst participated in the inhibition of the catalytic efficiency because of the fast agglomeration of Ni particles on the SiO2 surface, that arise from the weak interactions between the metal and support. The Ni–Mo/CeO2 catalyst displayed an exceptional catalytic decomposition behavior and durability stemming from the facile formation of a solid Ni–O–Ce solution with a fair interaction in terms of metal-support and the presence of some NiMoO4 species. These phases improved the dispersion and stability of the active Ni particles, resulting in improved catalytic activity. The hydrogen yield was 48% and 29% after 180 min of reaction over Ni–Mo/CeO2 and Ni–Mo/CeO2–SiO2 catalysts, respectively. Multi-walled carbon nanotubes of diverse radii were produced on the surface of both reacted catalysts depending on the catalyst structure and composition. TGA and Raman results showed that the as-deposited MWCNTs over both CeO2 and CeO2–SiO2 supported Ni–Mo catalysts exhibited good crystallinity and high graphitization degree.

Activation of small molecules is one of the important research topics for last decade. Activation of nitrogen is one among the important small molecule. This work presents a DFT study of the adsorption properties of nitrogen molecule over group 8 metal-borazine complex. Using B3LYP theory and 6-31G*/LANL2DZ basis sets, the different mode of adsorption of dinitrogen over the metal-borazine complex has been studied. In all the case, dinitrogen has adsorbed over the metal-borazine complex without undergoing any deformation and decomposition. Vibrational analysis, NPA and FMOs analysis afford significant understanding into their bonding and reactivity pattern. All the complexes show very strong binding towards dinitrogen and lead to activation of nitrogen molecule with less energy barrier. It has been observed that dinitrogen is highly activated in the case of Os-complex. The results show that group 8 metal-borazine complexes are a potential nitrogen trapper and good choice of complexes for activating the nitrogen molecule.

Efficient destruction of perfluoroalkyl compounds in contaminated waters remains a challenge because of highly stable C-F bonds. In this study, mineralization of perfluorooctanoic acid (PFOA) with high concentration (∼30 mg/L) was realized in a needle-plate pulsed discharge reactor integrated with a water jet (NPDW) to which microbubbles (MBs) with different carrier gases (air, N2, and Ar) were introduced to enhance interfacial reactions. MBs effectively enrich dispersed PFOA from a bulk solution to a liquid surface to allow enhancing contact with reactive species and also expanding the plasma discharge area and channels. The PFOA removal efficiency in air and Ar discharge reached 81.5 and 95.3% in 2 h, respectively, with a defluorination ratio of no less than 50%. Energy requirements (EE/O) ranged from 216.49 to 331.95 kWh/m3. Aside from fluoride, PFOA was degraded to a range of short-chain perfluoroalkyl acids and, to a minor extent, at least 20 other fluorinated transformation products. PFOA degradation mechanisms were proposed, including decarboxylation, hydroxylation, hydrogenation reduction, and defluorination reactions. Real water matrices (groundwater, tap water, wastewater effluent, and surface water) showed moderate impact on treatment outcomes, demonstrating the robustness of the treatment process. The study demonstrated an environmentally friendly nonthermal plasma technology for effective PFOA degradation.

A systematic study of halogenate(I/III) anions with polyatomic ligands is presented. The bis(perfluoro-tert-butoxy) halogenates(I) [X(OC4 F9 )2 ]- , X=Cl, Br, I, of chlorine, bromine, and iodine are prepared as their tetraethylammonium salts and characterized with IR, Raman, and NMR spectroscopic methods, as well as single-crystal X-ray diffraction analyses. Spectroscopical data are supported by quantum-chemical calculations. Additionally, the bonding situation of the species in question are analyzed and discussed. Furthermore, the oxidation to the corresponding halogenate(III) derivatives was studied. For [Br(OC4 F9 )2 ]- , oxidation with elemental fluorine gave [BrF2 (OC4 F9 )2 ]- . Iodide was directly oxidized by ClOC4 F9 to the IIII species [I(OC4 F9 )4 ]- , which is a surprisingly inert anion that might be used as a weakly coordinating anion (WCA) in the future. For [Cl(OC4 F9 )2 ]- , the decomposition products of the synthetic approaches towards a chlorine(III) system were analyzed.

Biowaste derived ethanol is an important feedstock for carbon neutral hydrogen production. It is liquid at atmospheric conditions, has a high hydrogen to carbon ratio, and it can be generated from ...

Summary Upgrading biomass-derived phenolic compounds provides a valuable approach for the production of higher-value-added fuels and chemicals. However, most established catalytic systems display low hydrodeoxygenation (HDO) activities even under harsh reaction conditions. Here, we found that Pd supported on –NH2-modified hierarchically porous carbon (Pd/HPC–NH2) with formic acid (FA) as hydrogen source exhibits unprecedented performance for the selective HDO of benzylic ketones from crude lignin-derived oxygenates. Designed experiments and theoretical calculations reveal that the H+/H− species generated from FA decomposition accelerates nucleophilic attack on carbonyl carbon in benzylic ketones and the formate species formed via the esterification of intermediate alcohol with FA expedites the cleavage of C–O bonds, achieving a TOF of 152.5 h−1 at 30°C for vanillin upgrading, 15 times higher than that in traditional HDO processes (∼10 h−1, 100°C–300°C). This work provides an intriguing green route to produce transportation fuels or valuable chemicals from only biomass under mild conditions.

Mitigation of undesired byproducts from ozonation of dissolved organic matter (DOM) such as aldehydes and ketones is currently hampered by limited knowledge of their precursors and formation pathways. Here, the stable oxygen isotope composition of H2O2 formed simultaneously with these byproducts was studied to determine if it can reveal this missing information. A newly developed procedure, which quantitatively transforms H2O2 to O2 for subsequent 18O/16O ratio analysis, was used to determine the δ18O of H2O2 generated from ozonated model compounds (olefins and phenol, pH 3–8). A constant enrichment of 18O in H2O2 with a δ18O value of ∼59‰ implies that 16O–16O bonds are cleaved preferentially in the intermediate Criegee ozonide, which is commonly formed from olefins. H2O2 from the ozonation of acrylic acid and phenol at pH 7 resulted in lower 18O enrichment (δ18O = 47–49‰). For acrylic acid, enhancement of one of the two pathways followed by a carbonyl–H2O2 equilibrium was responsible for the smaller δ18O of H2O2. During phenol ozonation at pH 7, various competing reactions leading to H2O2 via an intermediate ozone adduct are hypothesized to cause lower δ18O in H2O2. These insights provide a first step toward supporting pH-dependent H2O2 precursor elucidation in DOM., Environmental Science & Technology, ISSN:0013-936X, ISSN:1520-5851

Wastewater generated from industries seriously impacts the environment. Conventional biological and physiochemical treatment methods for wastewater containing organic molecules have some limitations. Therefore, identifying other alternative methods or processes that are more suitable to degrade organic molecules and lower chemical oxygen demand (COD) in wastewater is necessary. Heterogeneous Fenton processes and persulfate (PS) oxidation are advanced oxidation processes (AOPs) that degrade organic pollutants via reactive radical species. Therefore, in this study, limonite powder was incorporated into porous regenerated chitosan fibers and further used as a heterogeneous catalyst to decompose methylene blue (MB) via sulfate radical-based AOPs. Limonite was used as a heterogeneous catalyst in this process to generate the persulfate radicals (SO4−·) that initiate the decolorization process. Limonite–chitosan fibers were produced to effectively recover the limonite powder so that the catalyst can be reused repeatedly. The formation of limonite–chitosan fibers viewed under a field emission scanning electron microscope (FESEM) showed that the limonite powder was well distributed in both the surface and cross-section area. The effectiveness of limonite–chitosan fibers as a catalyst under PS activation achieved an MB decolorization of 78% after 14 min. The stability and reusability of chitosan–limonite fibers were evaluated and measured in cycles 1 to 10 under optimal conditions. After 10 cycles of repeated use, the limonite–chitosan fiber maintained its performance up to 86%, revealing that limonite-containing chitosan fibers are a promising reusable catalyst material.

Biomass can be upgraded via torrefaction, and torrefied kenaf (TK) is a fuel that allows blending with coal at high ratios. In the present study, raw kenaf (Hibiscus cannabinus L.) (RK) was torrefied at 523 K for 30 min and then mixed with Vietnamese anthracite (NinhBinh, NB) before co-pyrolysis. Thermogravimetric (TG) analysis was used to evaluate the behavior of RK, TK, and blended RK/TK during co-pyrolysis at biomass blending ratios (BBRs) of 0, 25, 50, 75, and 100 wt %. The TG and derivative thermogravimetry curves of a mixture of NB and RK (NBRK) were similar to those of RK. The decomposition curves of a mixture of NB and TK (NBTK) depended on the mass fraction of TK. Based on weight loss differences between the experimental and calculated data for the fuel blends, no interaction between the RK and anthracite was observed for all BBRs, whereas anthracite involving 50 and 75% TK exhibited synergistic effects. The temperature range for synergy and degree of synergy for NB and TK depended on the heating rate and mass ratio of TK. Kinetic parameters were calculated using the Friedman–non-isothermal free kinetic method at heating rates of 10, 20, and 40 K/min. The results showed that the activation energy (E) values of the NBRK at conversion ratios of 0.2–0.5 were equal to those of the RK, whereas they were superior at NB decomposition ratios of 0.6–0.8. NBTK1-1 (BBR of 50%) showed E values higher than those of NB at some conversion ratios, thus demonstrating a negative impact of blending. Further, NBTK1-3 (BBR of 75%) and NBTK3-1 (BBR of 25%) exhibited E values between those of NB and TK. The present study suggests that a high TK mass fraction (75%) in the blend for co-pyrolysis is optimal for the activation energy and volatile matter yield.

The kinetic and temperature dependencies of the conversion of hexane to gas and liquid oxide products on the surface of the nano-Al2O3 catalyst in the homo and hetero phase were investigated and compared. The rate of hexane conversion in air in different phases at temperature ∆T = 180–2000 C was determined ((a) 10–15% from the homo phase in the hetero phase; (b) thermal 12–17%; (c) radiation-thermal 14–22%). It is shown that the excess electron density formed in radiation defects migrates from the surface to the adsorbents, thereby weakening the intramolecular chemical bonds of the adsorbent and accelerating the decomposition processes investigated.

Cracking of high-sulfur natural bitumen of the Mordovo-Karmal and Ashalchi fields (Russia, Republic of Tatarstan) at a temperature of 450°C and different process times was studied. The characteristic features of the changes in the material and group compositions of the cracking products and the nature of the transformation of the group composition of the sulfur-containing compounds of oils as dependent on the cracking conditions were demonstrated. The kinetic regularities of the formation and decomposition of benzo- and dibenzothiophene derivatives in the cracking products of the natural bitumens were elucidated. Cracking was shown to involve breakdown of large molecules (resins and asphaltenes) with formation of a broad range of low-molecular-weight sulfur-containing compounds falling into oils. The sets of benzo- and dibenzothiophene homologs thereby formed were identical, but the rates of formation and decomposition of the sulfur-containing compounds were dependent on the thermal stability of the components of the initial bitumens. The data obtained provide a substantially better understanding of the laws governing the transformation of the sulfur-containing compounds of heavy hydrocarbon feedstock in thermal processes.

The eco-friendly insulating medium C5F10O gas has attracted the attention of many researchers due to its superior environmental protection and insulation properties. However, there are few studies on the compatibility of C5F10O gas with sealing materials for the gas-insulated equipment (GIE), which will bury hidden dangers for its engineering application. In this study, the compatibility of C5F10O gas with an ethylene propylene diene monomer (EPDM) sealing material which is most used in equipment was tested, and its reaction mechanism was simulated. The study found that the O element on the carbonyl group of C5F10O gas has high chemical reactivity and will interact with EPDM rubber. During the interaction process, EPDM rubber will also react with the C3F6 gas generated by the decomposition of C5F10O gas, and at the same time, it will also decompose C5F10O gas to produce more C3F6O and C3HF7. The surface of EPDM rubber will produce oily substances and a large number of crystal particles, which will cause its mechanical properties to deteriorate and shorten its service life. Therefore, it is necessary to carry out anti-corrosion treatment on the surface of EPDM rubber or replace the sealing material with better compatibility when designing and manufacturing GIE.

The ligation behavior of the chalcone ligand namely (E)-3-(4-hydroxy-3-methoxyphenyl) acrylic acid (ferulic acid) (FA) toward the Cu(II) and Zn(II) ions was determined. The structure of the isolated solid complexes was elucidated by elemental analyses, spectral techniques (IR, UV–Vis, 13C– and 1H-NMR spectra) as well as the conductance measurements and thermal analyses. UV–Vis spectra and magnetic moments had suggested square planar and tetrahedral stereochemistry for Cu(II) and Zn(II) complexes, respectively. The kinetic and thermodynamic parameters for some selected decomposition steps have been calculated. Two precise and sensitive spectrophotometric methods were utilized to determine Zn(II) and Cu(II) complexes with ferulic acid using a micellar media of cetylpyridinium bromide (CPB) and sodium lauryl sulfate (SLS) with an absorption maxima of 430 and 465 nm for Zn(II) and Cu(II), respectively. Various analytical conditions, for example, the concentration of the reagent, temperature, the sequence and timing of addition were also looked into. Under optimum conditions, the complexes exhibited good linearity in concentration range of 2.0–70.0 and 4.0–140.0 µg mL−1; molar absorptivities 1.3161 × 104 and 8.826 × 103 L mol−1 cm−1; and Sandell’s sensitivity 0.00496 and 0.00719 µg cm−2 for the proposed methods of Zn(II) and Cu(II), respectively. The complexes ratio was found to be 1:2 [Zn(II):FA or Cu(II):FA] and the stability constants were 2.771 × 105 and 2.826 × 105, respectively. Finally, the newly synthesized complexes were shown potent antimicrobial activity.

The research was devoted to experimental study of low-temperature cyclic chemisorption-catalytic process for H2S decomposition, including the identification of optimal chemisorbent-catalysts and quantitative investigation of process characteristics. The study involved sulfides of transient metals (Fe, Co and Ni) both in bulk and supported forms. The highest efficiency was achieved with bulk sulfides NiS, CoS and especially FeS. Sorption capacity of up to 10 % by weight is observed for these systems, while all the hydrogen sulfide is absorbed irreversibly. It was shown that at elevated temperatures (250−600 °C) the reaction can proceed in a quasi-stationary mode, in which the conversion of hydrogen sulfide and the yield of hydrogen are observed almost unchanged during rather long period of time. In this case, the conversion of H2S and the yield of H2 significantly exceed the equilibrium values for direct H2S decomposition reaction, thus indicating a noticeable contribution of chemisorption processes. In the optimal temperature range (350−400 °C), the hydrogen yield on these systems varies from 11 to 95 % with an average value of 26–34 % per cycle.

The decomposition of aluminum hydride complexes with trimethylamine and N-heterocyclic carbene—1,3-bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene was studied by a static tensimetric method with a membrane null-manometer. The AlH3·NMe3 complex passes into vapor in the form of monomeric molecules and in unsaturated vapor slowly decomposes at 70‒80°С into solid aluminum, gaseous trimethylamine, and hydrogen. The decomposition is accompanied by an induction period, the duration of which decreases as temperature increases. The AlH3 complex with carbene slowly decomposes at 170‒200°С with a rate practically independent of temperature.

Ozone (O3) plays essential roles in stratosphere and helps reduce the amount of harmful ultraviolet arriving the Earth’s surface. However, O3 is also a strong oxidant and causes troubles to human health in troposphere, especially in the confined space, such as indoor environment. Recently, O3 abatement materials have become research hotspots due to the urgent environmental demands. Catalysis is a facile strategy that can eliminate indoor airborne O3 efficiently and economically. Thus, this review summarizes the recent progresses of O3 decomposition catalysts. The catalysts covered here are categorized as follows: zeolite, metal organic frameworks (MOFs), metal oxides, noble metals. Manganese–based catalysts display higher efficiency and are mainly discussed. Generally, the active sites of O3 decomposition catalysts are described as Lewis acid sites (e.g., zeolite), metal sites (e.g., MOFs), oxygen vacancy sites (e.g., MnO2) in the previous work. In this review, we ascribe all the active sites to unsaturated metal sites and their Lewis acidity. Possible evidence from the experimental and theoretical perspectives are proposed. Furthermore, the strategy to circumvent deactivation caused by peroxides (O22–) accumulation and water molecular competition are also elaborated. Finally, perspective is presented on the challenges and opportunities of exploring existing and new O3 decomposition catalysts.

Detecting the composition and concentration of SF6 decomposition products is an effective method to evaluate the state of gas-insulated switchgear. Based on density functional theory, in this work we investigated the adsorption properties of four typical SF6 decomposition products (H2S, SO2, SOF2, SO2F2) on an SnS2 S vacancy structure (SnS2-Sv) and SnS2 edge structure (SnS2-edge). By calculating the adsorption energy, charge transfer, and comparing the density of states (DOS) of each system before and after the adsorption of gas molecules, the physical and chemical interactions between SnS2 with different structures and gas molecules were investigated. The results show that SnS2-Sv has the largest adsorption energy for SO2 and has obvious chemical interactions. The S vacancy can effectively capture an O atom in SO2, causing SO2 to firmly adsorb in the S vacancy. In addition, the adsorption of the four gases on the SnS2-edge is physical adsorption, in which the 50% S edge structure has the largest adsorption energy for H2S, reaching -0.52 eV, and there is also a large charge transfer between the 50% S edge structure and H2S. Although the adsorption energy of SnS2-edge to the four gases is smaller than SnS2-Sv, it is still greater than the pristine SnS2. This paper explores the adsorption properties of SnS2-Sv and SnS2-edge for SF6 decomposition products, providing insights for the development of SnS2-based gas sensors.

In this study, the catalytic effect of the internal surface of reactors constructed from stainless steel (SS310) for hydrogen production via methane decomposition has experimentally been proved and compared with a quartz-lined reactor. The effects of the methane decomposition temperature and volume-hourly-space velocity (VHSV) on hydrogen production, conversion of methane, and initial decomposition rates were investigated in an SS310 lab-scale reactor. Within the duration of the experiments, no change was recorded for hydrogen and methane concentration in all the experiments. The catalytic activity of the SS310 reactor's internal surface increased with increasing methane decomposition temperature (850−950 °C) and decreasing VHSV (37−52 h−1). The as-produced carbon was characterized using surface texture analysis, X-ray, and SEM-EDX.

Tertiarybutylarsine (TBAs) and tertiarybutylphosphine (TBP) are getting more and more established as group V precursors for the growth of V/III semiconductors by metal organic vapor phase epitaxy (MOVPE). Due to this development, the thermal decomposition of these precursors was studied during the growth of GaAs and GaP utilizing the Ga precursors, trimethylgallium (TMGa), triethylgallium (TEGa), and tritertiarybutylgallium (TTBGa), in a horizontal AIXTRON AIX 200 GFR MOVPE system. The decomposition and reaction products were measured in line with a real-time Fourier transform quadrupole ion trap mass spectrometer from Carl Zeiss SMT GmbH. The decomposition temperatures and the related activation energies were determined for all the mentioned precursors under comparable reactor conditions. The decomposition curves suggest, on the one hand, a catalytic effect of the GaAs surface on the decomposition of TBAs. On the other hand, the decomposition products indicate alkyl exchange as a relevant step during the bimolecular decomposition of TBAs and TBP with the Ga precursors TMGa, TEGa, and TTBGa. The catalytic reaction reduces the decomposition temperature of TBAs and TBP by up to 200 °C. In addition, for the growth of GaAs with TBAs and TEGa and for the growth of GaP with TBP and TEGa, a significant decrease of the decomposition temperature with an increasing V/III ratio is observed. This behavior, which is related to an alkyl exchange reaction, gives insights into the low-temperature growth of GaAs and GaP and is converted into an effective V/III ratio. Finally, the growth of GaAs with TTBGa and TBAs is realized at 300 °C below the unimolecular decomposition temperature of TBAs, underlining the catalytic effect of the GaAs surface. Altering the growth surface with trimethylbismuth led to the prevention of the catalytic effect.

According to UV-vis spectroscopy (0.10 mM, CH2Cl2 at 25 °C), the catalyst transformation (which could possibly include ligand dissociation with active catalyst formation, dimer formation, and decomposition) rate constants (kobs) of Grubbs' first (1) and second (2) generation catalysts are 7.48 × 10-5 and 1.52 × 10-4 s-1, respectively. From 31P NMR (0.1 M, CD2Cl2, at 25 °C), the catalyst transformation was 5.1% for 1 and 16.5% for 2 after 72 h. However, due to the larger concentrations of the NMR samples compared to the UV-vis samples, the extent of transformation did not correspond. The oxidation potential of the RuII/RuIII couple of 2 (E°' = 27.5 mV at v = 200 mV s-1) was considerably lower than that of 1 (E°' = 167 mV at v = 200 mV s-1). In the case of 1, a second reduction peak appeared at slow scan rates. This may probably be ascribed to an electrochemically active compound that was formed from the intermediate cation 1•+ and the subsequent reduction of the latter. The oxidation/reduction of 1 proceeds according to an ErCi electrochemical mechanism (Er = electrochemically reversible step, Ci = chemically irreversible step), whereas 2 proceeds according to an ErCr electrochemical mechanism (Er = electrochemically reversible step, Ci = chemically reversible step).

This article introduces an efficient decomposition process that uses sodium carbonate (Na2CO3) and activated carbon (C) as additives to decompose Bayan Obo mixed rare earth concentrate (hereinafter to be referred to as RE concentrate) by nonoxidative microwave radiation roasting. The roasting temperature, holding time, and contents of Na2CO3 and activated carbon are investigated. The optimum process parameters for decomposition are 800 °C and 30 min. The ratio of m(Na2CO3)/m(RE concentrate) is 0.5, and the ratio of m(C)/m (ER concentrate and Na2CO3) is 0.2 based on experimental data. Under the above conditions, the decomposition rate (shortened to DR) of RE concentrate is 98.58%, and the removal rates (shortened to CRs) of fluorine (F) and phosphorus (P) reached 80.35 and 46.75%, respectively. These rates are higher than traditional oxidation roasting under the same conditions. The three reasons for the result are the unique microwave heating characteristics, the overall efficient reaction of the mixture (RE concentrate, Na2CO3, and activated carbon), and the high nonoxidation rate of cerium. For these reasons and large experimental data, the reaction rate of the mixture is improved, and the efficiency of dilute hydrochloric acid for leaching rare earth elements is enhanced. In this article, the valence of rare earth elements in the roasted ore is all in the form of trivalence. Importantly, this nonoxidative roasted product can avoid the generation of chlorine in hydrochloric acid leaching. Moreover, such a short holding time is scarce in traditional roasting. When the mixture was roasted by utilizing microwave heating, the sinter phenomenon of the roasted product was avoided at high-temperature roasting. Finally, the surface morphology of RE concentrate at different conditions was observed by scanning electron microscopy (SEM) analysis, which can be used to compare the specific differences of roasting methods. According to these results, this process is beneficial for the decomposition of RE concentrate in terms of Na2CO3 roasting and is helpful for improving the clean and green technology method of hydrometallurgy.

One of the crucial steps for the conversion of CO2 into polymers is the catalytic formate to oxalate coupling reaction (FOCR). Formate can be obtained from the (electro)catalytic reduction of CO2, while oxalate can be further processed toward building blocks for modern plastics. In its 175 year history, multiple parameters for the FOCR have been suggested to be of importance. Yet, no comprehensive understanding considering all those parameters is available. Hence, we aim to assess the relative impact of all those parameters and deduce the optimal reaction conditions for the FOCR. We follow a systematic two-stage approach in which we first evaluate the most suitable categorical variables of catalyst, potential poisons, and reaction atmospheres. In the second stage, we evaluate the impact of the continuous variables temperature, reaction time, catalyst loading, and active gas removal within previously proposed ranges, using a response surface modeling methodology. We found KOH to be the most suitable catalyst, and it allows yields of up to 93%. Water was found to be the strongest poison, and its efficient removal increased oxalate yields by 35%. The most promising reaction atmosphere is hydrogen, with the added benefit of being equal to the gas produced in the reaction. The temperature has the highest impact on the reaction, followed by reaction time and purge rates. We found no significant impact of catalyst loading on the reaction within the ranges reported previously. This research provides a clear and concise multiparameter optimization of the FOCR and provides insight into the reaction cascade involving the formation and decomposition of oxalates from formate., Critical assessment of parameters in the formate to oxalate reaction using design of experiments and response surface model methodology in CO2 for materials processing.