Decomposition Of Nitrate Research Articles

Dehydrogenation of propane over sugar foams templated Ga2O3 nanoparticles catalysts

Highly active Ga2O3 nanoparticles catalysts were prepared by one-step oxidative decomposition of gallium nitrate with sucrose-derived carbon foams (SCF) template. The catalysts were investigated by XRD, Ar physisorption, SEM–EDS, HRTEM, TGA, NH3-TPD and 71 Ga MAS NMR. The addition of sucrose facilitated the higher surface area of Ga2O3 nanoparticles and morphological transformation from bulk to flake due to the structure-directing role of the sucrose solution. Moreover, the weak-medium surface acid sites increased by adding sucrose properly, which was related to the larger number of tetrahedral Ga3+ cations. The optimum catalytic activity was achieved over SXCF-Ga2O3 catalysts at the sucrose/Ga2O3 molar ratio of 6 with the propane conversion of 46.63% and propene selectivity of 88.18%.

Decomposition of Energetic Ionic Liquid Over IrCu/Honeycomb Catalysts.

The objective of this study is to elucidate the influence of a loading procedure of iridium and copper oxides over cordierite honeycomb support on catalytic performance during the decomposition of a hydroxylammonium nitrate (HAN) solution. Iridium and copper composite oxides were successfully supported on the cordierite honeycomb at the same time by repeating the wash coating process more than 2 times. Through the wash coating process, Cu and Ir were supported up to 43.4% and 4.9%, respectively. The cordierite honeycomb without active metal plays little role as a catalyst to lower the decomposition temperature. It was found that IrCu/honeycomb-2 catalyst, which was prepared by repeating the wash coating procedure twice, is an optimal catalyst for the decomposition of HAN solution. The IrCu/honeycomb-2 catalyst had the effect of lowering the decomposition onset temperature by 27.1°C compared to thermal decomposition.

Catalytic effect of lithium titanate oxide doped with praseodymium on thermal decomposition of ammonium nitrate

In this work, lithium titanate oxide (Li4Ti5O12) (LTO) and praseodymium ion doped in lithium titanate oxide (Pr-LTO) were synthesized in a sol–gel simple method, and their catalytic effects on thermal decomposition of ammonium nitrate were reported using thermogravimetric analysis–differential scanning calorimetry (TGA–DSC) techniques. The X-ray powder diffraction, Brunauer–Emmett–Teller surface area measurements, particle size analysis, energy-dispersive X-ray spectroscopy, and scanning electron microscopy techniques were used to identify the structural properties and morphology of LTO and Pr-doped LTO. By doping the praseodymium ion within the LTO spinel structure, the surface area increases (from 204.2 m2 g−1 for LTO semiconductor to 318.9 m2 g−1 for Pr-doped LTO), and the catalytic activity improved. The catalytic effects of LTO and Pr-LTO on the thermal behavior of AN were studied via TG-DSC techniques. The thermal decomposition of pure AN (196–400 °C) shifted to lower temperatures, 154–280 °C, and 131–241 °C, in the presence of LTO and Pr-LTO, respectively. The results showed that the catalytic effects of LTO were improved by praseodymium doping. The Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), Starink, and Tang methods were used to determine activation energies of all AN samples at different conversion values (α). The activation energies of pure AN values were 166 ± 3, 166 ± 2, 166 ± 2, and 162 ± 2 kJ mol−1, while AN/LTO activation energies were 145 ± 2, 144 ± 1, 144 ± 1, and 144 ± 2 kJ mol−1 and finally, those of AN/Pr-LTO were 112 ± 1, 109 ± 2, 110 ± 1, and 110 ± 1 kJ mol−1 using FWO, KAS, Starink, and Tang methods, respectively.

The nature of ammonium nitrate decomposition and explosions

AbstractAmmonium nitrate explosions can cause significant destruction as shown with examples in West, Texas (2013) and Tianjin, China (2015). Yet, ammonium nitrate is available in nearly every garden center, and serves as one of the major fertilizers used throughout the world. Why is it safe to store in a garden center, and yet not safe when stored in wooden framed buildings? This presentation explores the nature of ammonium nitrate decomposition steps using a process simulator where adiabatic, constant pressure, and constant volume scenarios are evaluated. Answers are simple, yet complex. The first decomposition step is endothermic. In other words, there is a natural barrier that needs to be overcome before further decomposition. Further explanations are offered within the paper.

The effect of molecular structure on the O – NO2 bond dissociation energy and the activation energy of the radical decay of cellotriose nitrates

The molecular structure was determined using the method B3LYP/6-31+G(2df, p), and the dissociation energies of the O – NO2 bond in dimethylcellobiose and cellotriose nitrates were calculated. It has been established that the O – NO2 bonds attached to the secondary carbon atom at C2 are the least strong in cellotriose nitrates. With an increase in the degree of substitution, a slight decrease in the dissociation energy of radical decay is observed. The results can be used to discuss the mechanism of thermal decomposition of cellulose nitrates.

Functionalized Co3O4 graphitic nanoparticles: A high performance electrocatalyst for the oxygen evolution reaction

We describe a novel synthesis technique for the production of graphitic carbon functionalized Co3O4 (G/Co3O4), which involves the rapid decomposition of cobalt nitrate in the presence of citric acid. Upon immobilization of the G/Co3O4 upon Screen-Printed macroElectrodes (G/Co3O4-SPEs) the G/Co3O4-SPEs were found to exhibit remarkable electrocatalytic properties towards the Oxygen Reduction Reaction (OER). A detailed investigation has been carried out on the influence that the graphitization of the citric acid has, during the course of preparation of Co3O4, upon the ability of the G/Co3O4 to catalyse the OER within alkaline conditions (1.0 M KOH). The graphitization of citric acid ensures the uniform distribution of Co3O4 and enhanced conductivity with maximal exposure of active sites, which are the key parameters to delivering enhanced electrochemical activity. The G/Co3O4-SPEs exhibits an overpotential of 304 mV (recorded at 10 mA cm−2), a Tafel slope of 110 mV dec−1 and remain stable in its signal output (achievable current density) at varying temperatures (5–50 °C), and after 10 h of chronoamperometry in 1.0 M KOH. The G/Co3O4-SPE's OER activity was found to be superior to that of bulk and nano Co3O4. The results exhibited within this study will enable production of high-performance and environmentally benign electrocatalysts towards the OER for use within water splitting devices.

Formation of TiO2 particles during thermal decomposition of Ti(NO3)4, TiOF2 and TiOSO4

In the paper, impact of the precursor decomposition conditions on the morphological and structural characteristics of TiO2 particles was discussed. The novelty and significance of the researches lay in the ability to control morphological features of the synthesized powder particles so that enhanced properties of the sintered ceramics can be obtained. The research program covered thermal decomposition of titanium nitrate, titanium oxyfluoride and titanium oxysulphate at different temperatures, with and without organic additive. Obtained titanium dioxide powder underwent analysis, namely, its phase composition, particle shape and dimensions were measured using X-ray and IR-spectra, as well as scanning electron microscopy. Activity of the obtained particles during sintering process was analyzed using dilatometer and microhardness measurement after sintering. It was found that spherical TiO2 nanoparticles of anatase and rutile phases can be obtained from decomposition of titanium nitrate at 700 °C. Thermal decomposition of other precursors, titanium oxyfluoride and oxysulfate, synthesized only anatase phase with particles of 200 and even 300 nm. Obtained spherical particles were smaller when temperature of decomposition was lower or the activator OP9 was added. However, lower decomposition temperature and additive had negative effect on sintering activity of the obtained particles, decreasing the microhardness of sintered specimens.

Evolution mechanism of NOx in NH3-SCR reaction over Fe-ZSM-5 catalyst: Species-performance relationships

Fe-based zeolites are known for desired high-temperature activity in the selective catalytic reduction of NOx by NH3, and species-performance relationships over Fe-ZSM-5 were systematically investigated in this study. Via activity tests, characterization and TOF calculation, it was found that both the relative amount and the real content of active Fe species played vital roles in the catalytic activity. The weakened high-temperature acid sites and stronger NH3 oxidation caused by oligomeric Fe and FexOy species could account for the decreased high-temperature activity over Fe-ZSM-5 with a high Fe loading. N2O formation via nitrate decomposition was barely found over Fe-ZSM-5 with Fe content of 1.0 wt%, the “L-H” and “E-R” pathway could coexist in the SCR reaction as suggested by DRIFT studies. DFT calculation showed that [Fe-NO2]-1 was the most easily generated and the formation of [Fe-NO2]-1/[FeO-NO] was the rate limiting step in the calculated reaction pathways of NO2 and NH3.

Preparation of Ni2P Supported on Al2O3 and B2O3 Mixed Oxides by Temperature-Programmed Reduction of Phosphate Precursors with Low P/Ni Ratios

Two types of mixed oxides of B2O3 and Al2O3 were prepared. Aluminum borates (ABx, x represents the B/(B + Al) ratio) were prepared by low-temperature thermal decomposition of aluminum nitrate and H3BO3 sustained by the simultaneous oxidation of an organic agent (glycerol), while B2O3-Al2O3 with B/(B + Al) ratio of 0.3 was obtained by incipient wetness impregnation of H3BO3 on a commercial γ-Al2O3 support. Tetrahedrally, pentahedrally, and octahedrally coordinated Al3+ cations were all present in AB0.3 with ratios of 10.9/21.3/67.8, while no pentahedrally coordinated Al3+ was observed in B2O3-Al2O3. B2O3 was enriched in the surface of AB0.3. The Ni2P phase was obtained by temperature-programmed reduction of a phosphate precursor with a P/Ni ratio as low as 1.2 supported over both AB0.3 (Ni-P(1.2)/AB0.3) and B2O3-Al2O3 (Ni-P(1.2)/B2O3-Al2O3). This suggests that the surface B2O3 inhibits the reaction between nickel phosphates and Al2O3, and thus facilitates the formation of Ni2P. The hydrodesulfurization (HDS) of dibenzothiophene (DBT) over the supported Ni2P catalysts occurred mainly by the direct desulfurization pathway, and Ni-P(1.2)/B2O3-Al2O3 was much more active than Ni-P(1.2)/AB0.3. These features make B2O3-Al2O3 a promising support for Ni2P catalysts. The HDS of DBT followed a pseudo-first-order kinetics over Ni-P(1.2)/B2O3-Al2O3, whereas over Ni-P(1.2)/AB0.3 it can be described by pseudo-zero-order kinetics. The pseudo-zero-order kinetics suggests a strong adsorption of DBT on Ni-P(1.2)/AB0.3, which could be responsible for its lower activity.

Effects of chloride ions on electrochemical reaction of 316 stainless steel in mixtures of molten nitrate salts

AbstractEffects of chloride ion on decomposition of ternary nitrate and corrosion behaviors of 316 stainless steel (316 SS) were studied by electrochemical corrosion tests in molten salt. Chemical composition and morphology of the corrosion products were analyzed using x‐ray diffraction and scanning electron microscopy equipped with energy disperse spectroscopy. Composition analysis for molten salt combined with morphology analyses of corrosion layer showed that presence of chlorine ions slowed down decomposition of ternary nitrate and increased corrosion rate of stainless steel markedly. The polarization curve obtained indicated that the corrosion current density increased from 3.02 mA ⋅ cm−2 to 8.76 mA ⋅ cm−2 with the addition of 10 % NaCl. Electrochemical impedance spectroscopy indicated a decrease in charge‐transfer resistance of the double layer between 316 SS and ternary Nitrate containing 10 % NaCl, resulting in a decreased corrosion resistance of 316 SS.

Influence of lattice oxygen on properties of Ce–Fe composite in NO+CO reduction system

Ce–Fe composite was prepared by hydrothermal method to simulate the ore facies with Ce–Fe coatingembedded structure in rare earth tailings. Fe2O3 is used as the carrier and cerium nitrate is used as active component. We studied the effect of lattice oxygen on the performance of Ce–Fe composites in the NO+CO reduction system. The results show that the peak of CeO2 in the sample prepared by the hydrothermal method of nitric acid moves at a high angle, the lattice constant becomes smaller, and the diffraction peak corresponding to CeO2 in Raman is red-shifted. It indicated that the hydrothermal method can form Ce–O–Fe solid solution. In TEM, nanoscale Fe2O3 particles caused by the decomposition of ferric nitrate were observed on the surface of the sample. In the whole reaction process, a large amount of lattice oxygen provided by Fe2O3 as a carrier, the presence of Ce–O–Fe solid solution and free Fe2O3 fine particles determine the high catalytic activity of the composite catalyst. The presence of CeO2 can improve the surface reduction of Fe2O3, and also promote the conversion of Fe3+ to Fe2+, Ce4+ to Ce3+. The conversion of lattice oxygen to adsorbed oxygen reflects the combined action of the composite catalysts Ce and Fe. The denitration rate of the Ce–Fe composite NO+CO reduction system exceeded 92.24% at 700 °C. Lattice oxygen can promote the performance of Ce–Fe composites in NO+CO reduction system.

Co-Electrolysis-Assisted Decomposition of Hydroxylammonium Nitrate-Fuel Mixtures Using Stainless Steel-Platinum Electrodes.

Hydroxylammonium nitrate (HAN) is a promising green propellant because of its low toxicity, high volumetric specific impulse, and reduced development cost. Electrolytic decomposition of HAN is an efficient approach to prepare it for further ignition and combustion. This paper describes the investigation of a co-electrolysis effect on electrolytic decomposition of HAN–fuel mixtures using stainless steel–platinum (SS–Pt) electrodes. For the first time, different materials were utilized as electrodes to alter the cathodic reaction, which eliminated the inhibition effect and achieved a repeatable and consistent electrolytic decomposition of HAN solution. Urea and methanol were added as fuel components in the HAN–fuel mixtures. When the mass ratio of added urea ≥20%, the electrolytic decomposition of a HAN–urea ternary mixture achieved 67% increment in maximum gas temperature (Tgmax) and 185% increment in overall temperature increasing rate over the benchmark case of HAN solution. The co-electrolysis of urea released additional electrons into the mixtures and enhanced the overall electrolytic decomposition of HAN. In contrast, the addition of methanol did not improve the Tgmax but only increased the overall temperature increasing rate. This work has important implications in the development of an efficient and reliable electrolytic decomposition system of HAN and its mixtures for propulsion applications.

Two-stage decomposition of 2-hydroxyethylhydrazinium nitrate (HEHN)

The hydrazine-derived ionic liquid 2-hydroxyethylhydrazinium nitrate (HEHN) is a promising fuel component of green monopropellants. For successful implementation of these propellants, it is necessary to understand the kinetics and mechanism of HEHN decomposition, but the available data are scarce. The objective of the present work was to investigate the kinetics of HEHN thermal decomposition using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) as well as to identify the evolved gas products with mass spectrometry (MS) and Fourier-transform infrared (FTIR) spectroscopy. Both TGA and DSC have revealed that the decomposition of high-purity HEHN has two distinct stages. The effective kinetic parameters of both stages were determined using the Ozawa-Wall-Flynn, Kissinger, and model-based methods. The model-based analysis has shown autocatalytic behaviour of the involved reactions and produced apparent activation energies of 113.7 ± 1.7 kJ/mol at the first stage and 123.6 ± 2.5 kJ/mol at the second stage, close to the literature data (124.8 kJ/mol) on the autocatalytic reaction between HEHN and HNO3. The evolved gas analysis has shown that the first stage generates H2O, N2, NH3, NO, N2O, and NO2, while the second stage also generates HNO3 and CO2. The observed existence of two stages in the thermal decomposition of HEHN could be explained by the formation of a condensed by product, which, in turn, decomposes via a highly activated reaction during the second (high-temperature) stage.

Performance of Pt and Ir Supported on Mesoporous Materials for Decomposition of Hydroxylammonium Nitrate Solution.

The catalytic decomposition of hydroxylammonium nitrate (HAN) was investigated using a series of platinum and iridium supported on mesoporous materials. In this study, MMZY, KIT-6, and SBA-15 were used as supports. The effects of the active metal and the pore structure of the catalysts on decomposition of HAN solution were studied. The activity of the platinum catalysts supported on mesoporous material is much superior to that of the iridium catalysts on the same support. The Pt(10)/SBA-15 catalyst showed excellent decomposition activity and was the best among the catalysts tested here, which seemed to be because of the pore structure of Pt(10)/SBA-15. Because the pore size of Pt(10)/SBA-15 is larger than that of Pt(10)/MMZY and Pt(10)/KIT-6, it is more advantageous for diffusion of reactant and product gas. The activity of the catalyst increased as the amount of Pt loaded on the SBA-15 support increased.

Safer emulsion explosives resulting from NOx inhibition

Ammonium nitrate (NH4NO3, AN) is a major commodity chemical. Its principal uses are as a fertilizer and an explosive. Ammonium nitrate is inherently unstable and has been the cause of numerous accidental explosions, sometimes with hundreds of deaths. We have investigated the thermal decomposition and methods of inhibiting the critical reactions of ammonium nitrate. NOx gas was shown to accumulate during an induction period and lead to the generation of nitrous acid (HNO2). Removal of NOx by adsorption or reduction provides alternative approaches to inhibition. In this work we reveal alternative methods to inhibit accidental ammonium nitrate explosions. Layered double hydroxides, such as hydrotalcite, were found to be very effective at inhibiting and delaying detonation by adsorbing NOx. Urea, traditionally used to inhibit explosions, was found to be very ineffective at higher temperatures (above ∼ 80 °C). However, the addition of MnO2 catalysts to urea increased its efficiency at temperatures up to ∼ 130 °C. The urea/MnO2 catalyst system was a highly effective inhibitor for preventing thermal decomposition of ammonium nitrate over a wide temperature range.

Selected magnesium compounds as possible inhibitors of ammonium nitrate decomposition

Abstract Ammonium nitrate (AN) is considered to be a very hazardous and difficult to handle component of mineral fertilizers. Differential thermal analysis coupled with thermogravimetry and mass spectrometry was used to determine the possible inhibiting effect of selected magnesium compounds on thermal decomposition of AN. Each additive was mixed with AN to create samples with AN:magnesium compound mass ratios of 4:1, 9:1 and 49:1. Most of analyzed compounds enhanced thermal stability of ammonium nitrate, increasing the temperature of the beginning of exothermic decomposition and decreasing the amount of generated heat. Magnesium chloride hexahydrate was determined to accelerate the decomposition of AN while magnesium sulphate, sulphate heptahydrate, nitrate hexahydrate together with magnesite and dolomite minerals were defined as inhibiting agents.

Thermal decomposition of ammonium nitrate on rust surface: Risk of low-temperature fire

Ammonium nitrate (AN, NH4NO3) remains classified as an oxidising agent for transport, storage and handling purposes. The safe use of ammonium nitrate requires strict procedures as AN is incompatible with many materials. This study investigates the thermal decomposition of AN on surfaces of rust, potentially present on steel in storage facilities of AN. Infrared spectroscopy and X-ray diffraction served to characterise the mineralogy of the rust, relatively to neat iron (III) oxide. Furthermore, simultaneous thermogravimetric measurements and differential scanning calorimetry afforded the isoconversional analysis that yields the activation energies of the decomposition process. The results, in conjunction with the molecular modelling involving oxygen-deficient Fe2O3 clusters, elucidate the effect of rusts, existing on the surface of corroded steel, in reducing the ignition temperature of AN. This process manifests itself by lowering the activation energies of the initiation channels of the decomposition reactions. On the contrary, pure Fe2O3 does not influence the decomposition of AN. The dehydroxylation of hydrated iron (III) oxide, present on surfaces of rust, exposes the Fe sites that react exothermically with AN, before the material assumes the ordered Fe2O3 phase.

Fabrication of Nanoyttria by Method of Solution Combustion Synthesis.

In the work the research on properties of an yttria nanopowder obtained by solution combustion synthesis (SCS) in terms of its application in ceramic technology is presented. In order to characterize the SCS reaction the decomposition of yttrium nitrate, glycine and their solution was investigated using differential thermal analysis coupled with FT-IR spectrometry of the gases emitted during the measurements. The product obtained in the SCS process was characterized in terms of its microstructure, particle size distribution and BET specific surface. Although the obtained powders showed nanoscaled structures, only after calcination at a temperature of 1100 °C nanosized particles were revealed. The calcined powder occurred in an agglomerated state (cumulants mean Zave = 1.3 µm). After milling particle size was successfully decreased to Zave = 0.28 µm. The deagglomerated powder was isostatically densified and tested for sintering ability. The obtained nanopowder showed very high sintering activity as the shrinkage onset was detected already at a temperature of about 1150 °C.

Effects of sodium nitrate and heat treatment atmosphere on the synthesis of α–NaFeO2 layered oxide

α-NaFeO2 type layered oxides shows reversible intercalation/de-intercalation of sodium ions between the oxide layers, which is suitable as regenerable CO2 absorber and cathode material for secondary batteries. This paper reports a critical effect of heating atmosphere to synthesize pure α-NaFeO2 from equimolar sodium nitrate and iron oxide. Reaction of NaNO3 with γ-Fe2O3 was much faster in nitrogen than oxygen atmosphere and high-purity α-NaFeO2 was yielded in a few hours of heat treatment in nitrogen while in oxygen atmosphere the reaction was sluggish, resulting in partially sodiated γ-Fe2O3. Inert atmosphere thermodynamically enhances nitrate decomposition, which controls the reaction rate of NaNO3 with γ-Fe2O3, and increases the solubility of γ-Fe2O3 in molten NaNO3 to promote topotactic phase transformation to α-NaFeO2. Molten NaNO3 works as a solvent for ferric ions and a redox buffer for maintaining the lattice oxygen structure and oxidation state of γ-Fe2O3. Larger iron oxide crystal was found to be suitable for production of high-purity α-NaFeO2 in a wide temperature range.

Fischer-Tropsch synthesis: Direct cobalt nitrate reduction of promoted Co/Al2O3 catalysts

Direct reduction of cobalt nitrate versus conventional calcination/reduction treatment was conducted using alumina with identical methodology as previously applied to SiO2 and TiO2. Similar BET surface areas, pore volumes and pore size distributions were obtained for the activated calcined and uncalcined catalysts indicating no significant difference in morphological properties. However, the reducibility slightly increases and Co crystallite size is smaller for activated uncalcined samples. Reduction phenomena were analyzed by TPR-MS and TPR-EXAFS/XANES. Combining these techniques allows an explanation of the complex phenomena occurring during the direct reduction of cobalt nitrate, as both nitrate decomposition and cobalt oxide reduction are involved. Cobalt nitrate species are converted to CoOx intermediates. These species are oxidized by NOX (from nitrate decomposition) to Co3O4 spinel, which is converted to CoO prior to Co0 formation. Noble metals (Pt, Re, Ru and Ag) improve cobalt oxide reducibility, especially for the final reduction step (i.e., CoO to Co0). The effect of direct nitrate reduction on FT activity was investigated using a 1 L CSTR. Activated unpromoted and Pt-promoted uncalcined catalysts achieved higher initial and steady-state CO conversions in comparison to the corresponding calcined catalysts. The best performance was achieved with direct reduction of uncalcined 0.5 %Pt-25 %Co/Al2O3.