Catalytic Decomposition Process Research Articles

Experimental investigation of the catalytic decomposition and combustion characteristics of a non-toxic ammonium dinitramide (ADN)-based monopropellant thruster

Low toxicity ammonium dinitramide (ADN)-based aerospace propulsion systems currently show promise with regard to applications such as controlling satellite attitude. In the present work, the decomposition and combustion processes of an ADN-based monopropellant thruster were systematically studied, using a thermally stable catalyst to promote the decomposition reaction. The performance of the ADN propulsion system was investigated using a ground test system under vacuum, and the physical properties of the ADN-based propellant were also examined. Using this system, the effects of the preheating temperature and feed pressure on the combustion characteristics and thruster performance during steady state operation were observed. The results indicate that the propellant and catalyst employed during this work, as well as the design and manufacture of the thruster, met performance requirements. Moreover, the 1 N ADN thruster generated a specific impulse of 223s, demonstrating the efficacy of the new catalyst. The thruster operational parameters (specifically, the preheating temperature and feed pressure) were found to have a significant effect on the decomposition and combustion processes within the thruster, and the performance of the thruster was demonstrated to improve at higher feed pressures and elevated preheating temperatures. A lower temperature of 140°C was determined to activate the catalytic decomposition and combustion processes more effectively compared with the results obtained using other conditions. The data obtained in this study should be beneficial to future systematic and in-depth investigations of the combustion mechanism and characteristics within an ADN thruster.

Iso-octane internal reforming in a solid oxide cell reactor

This study reports on the feasibility of internal iso-octane steam reforming process in an YSZ solid oxide fuel cell reactor by employing Cu/CeO2 as catalyst/anodic electrode. The Cu/CeO2 anode is evaluated for its both catalytic and electro-catalytic performance. In all cases, i-C8H18 was successfully reformed by H2O to syngas. In addition, appreciable amounts of CO2 and CH4 were also produced. The distribution of products was also influenced by i-C8H18 thermal pyrolysis and catalytic decomposition processes leading mainly to olefins formation. At closed-circuit operation, and by applying anodic overpotentials, mainly H2 and CO were electro-oxidized to H2O and CO2, while at cathodic polarization conditions the co-electrolysis of H2O and CO2 to H2 and CO was taking place, affecting the equilibrium reactions at the anodic chamber. During fuel cell operation, the electrochemical performance increased with cell temperature and i-C8H18/H2O feed ratio. The AC impedance spectroscopy analysis showed contributions both from charge and mass transfer processes, with the latter to dominate the overall cell performance.

Concentration measurement of carbon monoxide in the combustion chamber of ADN-based thruster with QCL

Ammonium Dinitramide (ADN) is a chemical propellant with high-performing, green, and storable characteristics. It has been used as solid propellant and liquid propellant which represents a new trend in chemical propulsion technology. The present study discussed the experimental investigations of a model aerospace thruster with ADN-based liquid propellant. The catalytic decomposition and combustion processes of the ADN-based thruster is significantly complicated. And only few literatures are focused on this topic. In this paper, based on quantum cascade laser (QCL), the combustion process in the ADN-based thruster was investigated. Carbon monoxide(CO) is a characteristic species produced during the chemical reaction of ADN-based liquid propellant. Through the measurement of CO concentration, the complicated catalytic decomposition and combustion processes was described quantitatively. These results are valuable for a better understanding of the mechanisms of the catalytic decomposition and combustion with ADN-based liquid propellant, which is beneficial to the development of green aerospace propulsion techniques.

Formation of alumina film using alloy catalyzers in catalytic chemical vapor deposition

The decomposition of tri-methyl aluminum (TMA) by various catalytic alloys is investigated to find low cost and oxidation-resistive catalyzers for preparation of alumina films by catalytic chemical vapor deposition (Cat-CVD) method. It is found that the temperature to decompose TMA in catalytic decomposition process decreases in the temperature region below 500°C with associated reduction in activation energy as chromium (Cr) contents in catalytic alloys increase. It is also found that the density of decomposed species increases as nickel (Ni) contents in alloys increase. It has been confirmed from alumina film formation experiments using various alloy catalyzers that the growth rate of films increases as Ni contents included in the catalytic alloys increase.

NO removal in the process of adsorption non-thermal plasma catalytic decomposition

The interesting process of adsorption NTP catalytic decomposition (ANCD) was used for NO removal without external heating. NO removal by NTP alone, NTP assisted catalytic decomposition (NCD) and ANCD were each studied for comparative purposes. The energy efficiency, NO removal efficiency and discharge power of these processes were investigated. Compared with the other two processes, outstanding experimental results were achieved by the ANCD process. Using this process, three different catalysts were also investigated. The results showed that the adsorption properties of the catalyst play a key role in the ANCD process. In addition, the influence of NO concentration on the conversion of NO was not appreciable. When the flow was too large, the residence time of pollutants in the catalyst decreased, resulting in a reduction in its adsorption capacity for pollutants and a decrease in the NO conversion and energy efficiency.

스팀 플라즈마를 이용한 HFCs 분해특성

CFCs (Chlorofluorocarbons) and HCFCs (Hydrochlorofluorocarbons) that are chemically stable were proven to be a greenhouse gases that can destroy ozone layer. On the other hand, HFCs (Hydrofluorocarbons) was developed as an alternative refrigerant for them, but HFCs still have a relatively higher radiative forcing, resulting in a large Global Warming Potential (GWP) of 1,300. Current regulations prohibit production and use of these chemicals. In addition, obligatory removal of existing material is in progress. Methods for the decomposition of these material can be listed as thermal cracking, catalytic decomposition and plasma process. This study reports the development of low cost and high efficiency plasma scrubber. Stability of steam plasma generation and effect of plasma parameters such as frequency of power supply and reactor geometry have been investigated in the course of the development. Method for effective removal of by-product also has been investigated. In this study, elongated rotating arc was proven to be efficient in decomposition of HFCs above 99% and to be able to generate stable steam plasma with steam contents of about 20%.

Retracted Article: Catalytic decomposition of ammonium dinitramide (ADN) as high energetic material over CuO-based catalysts

A CuO/Al2O3–La2O3 catalyst was effective for ADN catalytic decomposition processes. Moreover, the present catalyst was stable after several tests and compared with CuO/Al2O3.

N2O emission and reduction in the electronics manufacturing industries

AbstractElectronics manufacturing industries have rapidly developed in South Korea. To reduce the use of fluorinated gases having high global warming potential (GWP) in their processes, companies have recently attempted to replace these gases with nitrous oxide (N2O). Unfortunately, N2O itself has a GWP of 310 and is one of the main greenhouse gases. The electronics manufacturing industries should therefore consider reducing N2O emissions from their processes. This study measured the N2O emission from a large display manufacturing plant in South Korea and investigated the removal of N2O at the site of the plant by either a catalytic decomposition process or a reduction process. We suggest a hybrid N2O reduction process to effectively reduce the N2O emissions of the electronics manufacturing industries. © 2012 Society of Chemical Industry and John Wiley & Sons, Ltd

HAN and ADN as liquid ionic monopropellants: Thermal and catalytic decomposition processes

Binary HAN and ADN aqueous solutions have been synthesized, then thermally and catalytically decomposed. Binary HAN mixtures were prepared with different concentrations: 95, 80 and 60wt.%. Whereas ADN solution contains are: 75, 60 and 50wt.%. The candidate catalysts were prepared by impregnation of alumina doped by lanthanum oxide with active phase precursors: iridium for HAN and copper oxide for ADN and characterized by transmission electron microscopy, X-ray diffraction and chemisorption. The decomposition processes were followed by thermal analysis and a constant batch reactor. This work shows the essential effect of monopropellant concentrations to determine the best green propellants for industrial applications as reaction control systems. Moreover, HAN and ADN solutions are more efficient for catalytic decomposition due to the absence of stabilizer to inhibit catalysts. The (10%)Ir/Al2O3–La2O3+HAN95% and the (10%)CuO/Al2O3–La2O3+ADN75% associations show lower decomposition temperatures, larger reaction rates and leads to higher amount of gas phase products, giving the most efficient systems.

Catalytic Decomposition of PH3on Heated Tungsten Wire Surfaces

The catalytic decomposition processes of PH3 on heated tungsten surfaces were studied to clarify the mechanisms governing phosphorus doping into silicon substrates. Mass spectrometric measurements show that PH3 can be decomposed by more than 50% over 2000 K. H, P, PH, and PH2 radicals were identified by laser spectroscopic techniques. Absolute density measurements of these radical species, as well as their PH3 flow rate dependence, show that the major products on the catalyst surfaces are P and H atoms, while PH and PH2 are produced in secondary processes in the gas phase. In other words, catalytic decomposition, unlike plasma decomposition processes, can be a clean source of P atoms, which can be the only major dopant precursors. In the presence of an excess amount of H2, the apparent decomposition efficiency is small. This can be explained by rapid cyclic reactions including decomposition, deposition, and etching to reproduce PH3.

Catalytic Decomposition of PH3 on Heated Tungsten Wire Surfaces

The catalytic decomposition processes of PH3 on heated tungsten surfaces were studied to clarify the mechanisms governing phosphorus doping into silicon substrates. Mass spectrometric measurements show that PH3 can be decomposed by more than 50% over 2000 K. H, P, PH, and PH2 radicals were identified by laser spectroscopic techniques. Absolute density measurements of these radical species, as well as their PH3 flow rate dependence, show that the major products on the catalyst surfaces are P and H atoms, while PH and PH2 are produced in secondary processes in the gas phase. In other words, catalytic decomposition, unlike plasma decomposition processes, can be a clean source of P atoms, which can be the only major dopant precursors. In the presence of an excess amount of H2, the apparent decomposition efficiency is small. This can be explained by rapid cyclic reactions including decomposition, deposition, and etching to reproduce PH3.

Substituted ferrite M Fe1−Fe2O4 (M = Mn, Zn) catalysts for N2O catalytic decomposition processes

The N2O catalytic decomposition to N2 and O2 as gas products was carried out on the substituted ferrite MxFe1 − xFe2O4 (M = Mn and Zn with x = 0 − 0.8) catalysts. The obtained results showed that the partial substitution of Fe by Mn and Zn metal transitions in Fe3O4 spinel oxide led to a significant improvement in the catalytic activity for the N2O decomposition. Moreover, the catalytic activity depended on the degree of Fe replacement by Mn or Zn. The N2O conversion reached 100% over the Mn0.8Fe0.2Fe2O4 and Zn0.6Fe0.4Fe2O4 catalysts at 250 and 280 °C for pure N2O, respectively. The decomposition temperatures were relatively increased after O2 addition.

Catalyst Poisoning by Amorphous Carbon during Carbon Nanotube Growth: Fact or Fiction?

The influence of amorphous carbon on FePt catalyst particles under chemical vapor deposition conditions typically applied for CNT growth is examined through two routes. In the first, FePt catalyst particles supported on alumina are exposed to a well-established cyclohexane thermal CVD reaction at various temperatures. At higher temperatures where self-pyrolysis leads to copious amorphous carbon and carbon tar formation, carbon nanotubes are still able to form. In the second route, an amorphous carbon film is first deposited over the catalyst particles prior to the CVD reaction. Even for reactions where further amorphous carbon is deposited due to self-pyrolysis, graphitization is still demonstrated. Our findings reveal that the presence of amorphous carbon does not prevent catalytic hydrocarbon decomposition and graphitization processes. We also show an additional catalytic reaction to be present, catalytic hydrogenation, a process in which carbon in contact with the catalyst surface reacts with H(2) to form CH(4).

Influence of chemical composition of nanocrystalline iron’s surface on the rates of two parallel reactions: nitriding and catalytic decomposition of ammonia

AbstractInfluence of chemical composition of nanocrystalline iron’s surface on its activity in the nitriding process of iron and catalytic decomposition of ammonia was studied. The rate of the nitriding reaction was measured by the thermogravimetric method using a tubular differential reactor. Hydrogen concentration in the reactor was also measured. The rate of the catalytic decomposition of ammonia was determined using the reactor’s mass balance. Experiments were conducted at different temperatures within the range from 300°C to 525°C. Iron catalyst for ammonia synthesis was studied. Two sorts of samples with a different content of potassium oxide (0.16 mass % and 0.64 mass % of K2O) were used. The composition of samples from the second group was modified by an addition of different amounts of sulfur. At temperatures above 400°C, when the effect of ammonia decomposition on the gas phase composition was experimentally measured, the presence of potassium and sulfur on the iron surface influenced the rate of the iron nitriding process. The ammonia decomposition rate was higher for samples with a greater amount of potassium. The rate of reactions depended also on the sulfur concentration and dropped when the sulfur content increased. The value of apparent activation energy of ammonia decomposition was in the range of 150 kJ mol−1 to 180 kJ mol−1 while the content of sulfur in the samples increased.

Development of direct resistive heating method for SO3 decomposition in the S–I cycle for hydrogen production

The Sulfur–Iodine (S–I) cycle has been considered as one of the efficient and promising thermochemical water-splitting cycles for hydrogen production using nuclear energy. However, the catalytic SO3 decomposition process in the S–I cycle demands high temperature heat (>800°C). Existing nuclear reactors cannot provide such heat for SO3 decomposition. AECL proposed a direct resistive heating concept to compensate for the requirement of high temperature heat. An experimental program was established at AECL to demonstrate the concept and to develop reliable catalyst structures for SO3 decomposition. Due to the high temperature and harsh chemical environment, Hastelloy C-276 was selected as the material for the heating element and reactor. The catalyst was directly applied on the surface of an electrical heating element. SO3 was produced online from H2SO4 in a pre-heated vessel. The SO3 decomposition percentage was determined using the measured O2 concentration in the exit gas stream. The results showed that SO3 decomposition can be successfully achieved with the direct resistive heating method. As much as 90% of the initial SO3 was decomposed under the experimental conditions explored. The Pt-based catalyst performed better than the Fe-based catalyst in the low temperature region (<700°C). The effect of carrier gas flow on SO3 decomposition was also considered.

Catalytic decomposition of NH 3 on heated Ru and W surfaces

The catalytic decomposition processes of NH 3 on heated W and Ru-coated W wires were examined by employing laser spectroscopic and mass spectrometric techniques. Laser spectroscopic measurements show that more H atoms are produced on uncoated W wires, while the NH-radical densities are higher for Ru-coated wires, at the same wire temperatures. Mass spectrometric measurements show that the decomposition efficiencies are nearly the same in both systems. The main products on heated W wires must be NH 2 and H, while the production of NH should also be important on Ru-coated W wires.

I214 カーボンブラック表面特性のメタン分解過程における変化(一般講演(8))

The variation of surface characteristics of carbon blacks in methane catalytic decomposition process was investigated. Remarkable time variation of the methane decomposition rate was demonstrated and the influence of carbon deposition was suggested. Surface characteristics of carbon blacks were analyzed by nitrogen adsorption-desorption isotherms and transmission electron microscopy (TEM). Changes in the surface structural characteristics were evaluated by the specific surface area, the pore size distribution, and TEM images. The correlation between the catalytic activity and the surface characteristics was discussed.

New data on the mechanism of hydrogen peroxide decomposition in acetic acid in the presence of vanadyl and cobalt (II) acetylacetonates

The process of catalytic hydrogen peroxide decomposition in acetic acid in the presence of vanadyl and cobalt (II) acetylacetonates was studied using modern spectroscopic and kinetic techniques. The formation of intermediates during the catalytic decomposition of hydrogen peroxide in the presence of VO(acac)2 was observed using UV—Vis and ESR spectroscopy. The decomposition of H2O2 occurs both catalytically and via the radical route.

Recovery of phytosterols from waste residue of soybean oil deodorizer distillate

This study describes a catalytic decomposition and crystallization process to recover phytosterols from the waste residue of soybean oil deodorizer distillate (WRSODD). Various solvents were used for the crystallization of phytosterols. The effect of different solvents on the purity and yield of recovered phytosterols was investigated. The composition of WRSODD was analyzed by silica gel column chromatography and FT-IR spectrum. Gas chromatography (GC), GC–MS, and FT-IR were adopted to determine the purity and structure of phytosterols. Results showed the total amount of phytosterols, in the form of fatty acid steryl esters, was up to 20 wt.% of WRSODD. Through orthogonal experiments, the optimized crystallization conditions were obtained. It’s found the mixed solvent of acetone and ethanol (4/1, v/v) could generate good crystallization. The yield of recovered phytosterols was 22.95 wt.% after the 1st crystallization. The purity of phytosterols reached 91.82, 92.73, and 97.17 wt.% after the 1st, 2nd, and 3rd crystallization, respectively.

Methane catalytic decomposition integrated with on-line Pd membrane hydrogen separation for fuel cell application

In this study, 70 wt.% Ni/Al 2O 3 was prepared via a glycine–nitrate combustion method and applied as the catalyst for decomposing methane into hydrogen and carbon nanotubes that can be applied in polymer-electrolyte-membrane fuel cell (PEMFC). The methane conversion and the hydrogen content in the effluent gas reached 71 and 83%, respectively, at an operating temperature of 700 °C under ambient pressure. I– V tests demonstrated that the methane is inert to the electro-catalyst and acts mainly as a diluting gas. A porous Al 2O 3-supported thin-film Pd membrane was integrated with the catalytic methane decomposition process. Due to the high initial hydrogen content, even an imperfect Pd membrane, effectively increased the hydrogen content to >98%, which resulted in only a slight performance loss of ∼10% compared to the application of pure hydrogen as the fuel. The advantages, such as continuous hydrogen separation, simple process, high reliability and value-added by-product, all make this process highly attractive for future PEMFC application.