Decomposition Of Carbon Monoxide Research Articles

Improvement of fretting fatigue strength by carbon monoxide and catalyst activation under chemomechanical effects of fretting

It is known that the fretting fatigue strength in hydrogen (H2) gas is lower than that in air. The objective of this study is to mitigate the hydrogen effect during the fretting fatigue test in H2 gas by adding carbon monoxide (CO) to the H2 environment. The expected CO effect was reduction in the hydrogen uptake into the material following deactivation of the catalytic surface where H2 molecules dissociate into H atoms. However, an unexpected result, which was unique in fretting, was obtained. The fretting fatigue test using JIS SUS304 austenitic stainless steel was performed in H2, argon (Ar), 2 vol% CO mixed H2, and 2 vol% CO mixed Ar gases. The fretting fatigue strengths in the CO-mixed gases were significantly improved. For instance, the fretting fatigue life at σa = 240 MPa was 8.8 × 105 cycles in the H2 and 107 cycles or longer in the CO mixed H2. The cause of the improved fretting fatigue strength was the formation of amorphous carbon between the contacting surfaces during the fretting. The carbon reduced the tangential force coefficient between the contacting surfaces from around 0.6 in the H2 to 0.2 or less in the CO mixed H2. The reduced tangential force resulted in improvement of the fretting fatigue strength. Although the detailed mechanisms of the carbon deposition were unclear, it is plausible that the catalytic action of the metal surface for the CO decomposition into C and O was activated by the effect of fretting, such as removal of the surface oxide layer and other chemomechanical effects.

Multi‐wall carbon nanotubes by catalytic decomposition of carbon monoxide on Ni/MgO

AbstractThe redox behavior of the catalyst and the catalytic decomposition of carbon monoxide (CO) were investigated in the synthesis process of multi‐wall carbon nanotubes (MWCNT) using Ni/MgO catalyst. The surface morphology of the heated Ni layer was observed by TEM to confirm the formation of NiO particles (50 nm or less) and NiO (222). The chemical reaction behavior of the catalyst in CO the atmosphere was displayed via TG‐DSC analysis, and the reduction of NiO was revealed due to the mass decrease of 2.71 wt% and the exothermic peak at around 400°C. The deposition of carbon was identified with an increase in mass and the exothermic peak near 600°C. Ni (111) and carbon (002) facets was taken place in a diffraction pattern of carbon deposited catalyst, indicating the reduction in NiO and the graphitic carbon deposition. The crystallinity of the graphitic carbon was analyzed as the ratios of 0.998 for ID/IG and 0.26 for sp3/sp2 in Raman and photoelectron spectra. The encapsulated Ni in MWCNT was observed through TEM‐EDS, verifying the activation of the catalyst by CO.

Enhanced photocatalytic efficiencies of TiO2 nanoparticles loaded with WO3 and Pt for exhaust decomposition

TiO2, WO3/TiO2 and Pt/WO3/TiO2 hybrid nanoparticles were prepared to measure the photocatalytic decomposition efficiencies on hydrocarbons (HC), nitrogen oxides (NOx) and carbon monoxide (CO), for the purpose to produce pavement coatings that can clean up vehicle exhaust. X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and UV-Vis-NIR spectrophotometer were used to characterize the nanoparticles. The decomposition rates of exhaust after 60 min photocatalytic reactions under UV and visible light irradiation were recorded to calculate the decomposition efficiencies. The optimum WO3 content in WO3/TiO2 binary nanoparticles is 2 atomic% (at%), and the optimum Pt content in Pt/WO3/TiO2 ternary nanoparticles is 1 at%. The decomposition efficiencies of WO3/TiO2 are higher than that of TiO2 but lower than Pt/WO3/TiO2 both under UV and visible light irradiations. Meanwhile, the decomposition efficiencies of all the photocatalysts under visible light are lower than that under UV light. By analyzing the experimental results, the loading of WO3 is proved to be more effective in decomposing HC, NOx and CO under visible light compared to the loading of Pt. Under UV light irradiation, the WO3 addition contributes more to the decompositions of HC and NOx, while the Pt addition contributes more to the decomposition of CO.

Tuning Geometry of SWCNTs by CO2 in Floating Catalyst CVD for High‐Performance Transparent Conductive Films

AbstractOptimized geometry of single‐walled carbon nanotubes (SWCNTs) is vital to high‐performance transparent conductive films (TCFs). Herein, the geometry of SWCNTs, i.e., tube diameter, bundle length, and bundle diameter, are successfully tuned by introducing carbon dioxide (CO2) into floating catalyst chemical vapor deposition (FC‐CVD), where carbon monoxide (CO) is used as a carbon source and ferrocene as a catalyst precursor. Both tube diameter and bundle length increase with an increment of CO2 concentration, and the yield of SWCNTs can be significantly promoted with the appropriate amount of CO2. The role of CO2 in this behavior is further rationalized as enhancing CO decomposition or carbon dissolution into catalysts. The TCFs based on SWCNTs with optimized geometry by CO2 exhibit improved performance up to 86.8 Ω sq−1 at 90% transmittance after AuCl3 doping, achieving about 50% reduction of sheet resistance compared to the TCFs without CO2. The use of CO2 for directly tuning growth of SWCNTs blazes a new trail in the field of SWCNT based TCFs.

Hyperbaric Oxygen Therapy and Acute Carbon Monoxide Poisoning

Carbon monoxide poisoning is the most commonly seen cause of poisoning in the emergency room (ER). The high affinity between carbon monoxide andhemoglobin and their complex biological characteristics greatly increase the risks of cardiac, nervous, muscular, and kidney diseases. In severe cases, patients may lose consciousness or die in just a few minutes. In recent years, hyperbaric oxygen therapy has been applied extensively in patients with severe conditions such as carbon monoxide poisoning and cerebral hypoxia. Hyperbaric oxygen accelerates the decomposition of carbon monoxide in hemoprotein. Therefore, treating patients with similar conditions in the ER with hyperbaric oxygen as soon as possible will improve their cognitive disorder and postpone their neuropsychological sequelae. ER nurses typically play a decisive role in saving patients with carbon monoxide poisoning. This research scrutinizes a case analysis of using hyperbaric oxygen to treat carbon monoxide poisoning and offers general rules for the use of hyperbaric oxygen. Further, the research elaborates from the perspective of ER nursing staffs the management and care of acute carbon monoxide poisoning and hyperbaric oxygen therapy nursing care. The aim of this research is to offer references for members of the ER nursing team and to enable this team to provide accurate and effective medical measures to patients during the "golden hours" of nursing care. Achieving this will help ensure that patients receive comprehensive nursing and care, thus reducing the harm suffered by patients and increasing the rate of survival.

Impact of support calcination and competitive adsorbate in Fe/Mo-Al2O3 catalyst for synthesis of carbon nanotubes by V-flame

Carbon nanotubes (CNTs) were synthesized via carbon monoxide decomposition with aid of various Fe/Mo-Al2O3 catalysts by V-type flame method. The influences of support calcination and competitive adsorbates on the morphology and properties of CNTs were studied. SEM, HRTEM, TPO and Raman spectroscopy were applied to investigate the morphology and microstructure of CNT products. XRD, H2-TPR were employed to characterize catalysts. The obtained results indicate that calcinated support can increase production and promote the formation of CNTs with small diameter. Utilizing citric acid as a competitive adsorbate is successful in improving the quality of CNTs. Besides, the addition of citric acid and calcinated support in catalyst enhances the catalytic growth activity. The obtained CNTs have a diameter around 4–6 nm within a narrow diameter distribution range. Raman spectrum analysis also illustrates that highly graphitized CNTs are produced on the catalyst with calcinated support and citric acid. These results suggest that support calcination and competitive adsorbate have pronounced effect on the average diameter, diameter distribution, and graphitization of CNTs, which provides a simple and effective way to tune the properties of CNTs.

Probing the structural organisation of sp2 carbons obtained by the Boudouard reaction using in situ Raman scattering in reducing conditions

The catalytic decomposition of carbon monoxide from a mixture of CO and H2 in the presence of iron or iron oxides has been the subject of many studies since the end of 1950s. The Boudouard reaction (2CO→CO2+C) produces solid carbon deposition in many high temperature industrial processes in which carbon monoxide is a reactant. The aim of this study was to determine whether the oxidation degree of iron has a significant effect in the quantity and in the morphology of carbon deposit. Original in situ Raman device using controlled temperature and gas mixture was developed to explore the evolution of the morphology of the carbon formation during Boudouard’s reaction. The results show two types of carbon morphologies (well-structurally organized sp2 carbons in the form of shells and nano-fibers) depending on the content of H2 in the gas mixture. The abundant production of carbon nano-fibers could be responsible for the destruction of refractory materials operating in CO+H2 atmospheres. This study is of outstanding importance to provide helpful observation and basic information on the involved mechanisms for solving this industrial problem.

The catalytic effect of iron oxides on the formation of nano-carbon by the Boudouard reaction in refractories

The catalytic decomposition of carbon monoxide via the Boudouard reaction in the presence of iron has been a subject of numerous studies. This reaction produces a solid carbon deposit in which CO is a reactant and results in deleterious effects on refractory materials. Only a few studies have used a gas mixture primarily composed of CO+H2, which is generated in new energy applications. We investigated the effect of the degree of oxidation and the grain size of the FexOy catalyst particles on the amount of carbon, in CO+H2, using thermogravimetric analysis and Raman-spectroscopy as well as scanning and transmission electron microscopy. All of the FexOy resulted in similar carbon formation. The effect of the grain size and specific surface particles was demonstrated, in particular due to the large decrease in the catalyst particle size. This study could be helpful for the future development of new refractories materials in reducing conditions.

Decomposition of carbon monoxide and carbon dioxide using cathode-supported dense yttria-stabilized zirconia electrolyte cell

CO, CO2 and CO–CO2 mixed gas were electrochemically decomposed at 800°C using a cell of Ni–YSZ (8mol% yttria-stabilized zirconia) cathode (5mm thick), dense YSZ electrolyte (40μm thick) and Ru–YSZ anode (30μm thick). The decomposition rate of CO gas (2CO→2C+O2) was in the range of 9–15% at an applied voltage of 1.0V and increased to 67–100% at 2.0–8.0V. Carbon was deposited significantly near the electrolyte interface in the cathode. In the case of CO2 gas decomposition (2CO2→2CO+O2, CO2→C+O2), CO2 gas of 6–8vol% was converted to CO (6–8vol%), O2 (2–9vol%) and C. Deposition of a small amount of C was observed in the cathode. The decomposition of CO–CO2 mixed gas produced O2 gas of 2–10vol% in the anode but carbon deposition hardly occurred. Carbon deposited in the cathode from CO decomposition was easily oxidized to CO gas again by CO2 mixed (C+CO2→2CO).

Natural Gas Steam Reforming over Rhodium/Alumina Catalysts: Experimental and Numerical Study of the Carbon Deposition from Ethylene and Carbon Monoxide

Natural gas steam reforming (SR) over technically used rhodium/alumina (Rh/Al2O3) honeycomb catalysts is studied experimentally at temperatures between 923 and 1073 K and steam-to-carbon ratios (S/C) of unity, with regard to coke deposition caused by the decomposition of the product species ethylene (C2H4) and carbon monoxide (CO). Furthermore, the process is modeled using detailed reaction mechanisms, and numerical simulations are carried out to describe the coke formation on Rh/Al2O3 catalysts quantitatively. The amount of deposited carbon was detected and analyzed for varying feed mixtures of the products CO and C2H4 diluted in N2. During the decomposition of CO, the saturation of the amount of coke is monitored by feeding CO in high concentrations. No saturation occurs for the same amounts of coke resulting from the decomposition of C2H4. The coking rate caused by the decomposition of C2H4 is found to be ∼25 times higher than the coking rate caused by the decomposition of CO. The differences in coking behavior caused by C2H4 and CO, respectively, are described by coking models.

The correlation between carbon monoxide and hydrogen cyanide in fire effluents of flame retarded polymers

This study considers the demonstrated correlation between carbon monoxide and hydrogen cyanide in the special case of fire retarded materials. It shows that the combination of aluminium phosphinate and melamine polyphosphate causes a much smaller increase in the carbon monoxide (CO) and hydrogen cyanide (HCN) yields than the combination of brominated polystyrene and antimony oxide, although both fire retardants inhibit combustion reactions in the gas phase. The formation and destruction mechanisms of CO and HCN are considered. It is shown that both toxicants form early in the flame, and that the OH radical is critical for the destruction of both CO and HCN. Crucially, in the context of the flame inhibition mechanism, this suggests that the phosphorus system reduces the H and O radical concentrations without a corresponding decrease in the OH radical concentration, thus it is an effective gas phase flame retardant which only causes a small increase in the toxic product yields. Conversely, the bromine system reduces the H, O and OH concentrations, and thus increases the fire toxicity, by inhibiting decomposition of CO and HCN. Moreover, while the phosphorus flame retardant is effective as an ignition suppressant at low temperatures, this effect ―switches off‖ at higher flame temperatures, minimising the potential increase in fire toxicity, once the fire develops.

Reduction Behaviors of Pellets Under Different Reducing Potentials

Owing to the change of gas composition in top gas recycling-oxygen blast furnaces compared with traditional blast furnace, many attentions are attracted to the research on iron oxide reduction again. In order to study the influence of H2 and CO on the reduction behavior of pellets, experiments were conducted with H2-N2, CO-N2 or H2-CO gas mixtures at 1173 K by measuring the mass loss, respectively. It was found that the reduction degree increased with increasing the ratio of H2 or CO in the gas mixture, but the reduction with hydrogen was faster than that with carbon monoxide. The reduction degree could reach 96. 72% after 65 min for the reduction with 50% H2 + 50% N2, while it is only 53. 37% for the reduction with 50% CO+ 50% N2. The addition of hydrogen to carbon monoxide will accelerate the reduction because the hydrogen molecules are more easily chemisorbed and reacted with iron oxide than carbon monoxide. A scanning electron microscope was used to characterize the structures of reduced samples. Dense structure of iron was obtained in the reduction with hydrogen while the structure of iron showed many small fragments for the reduction with carbon monoxide. At the later stage of reduction with the gas mixtures containing carbon monoxide, the reduction curves showed a descending trend because the rate of carbon deposition caused by the thermal decomposition of carbon monoxide was faster than the rate of oxygen loss. Compared with the reduction with CO-N2 and H2-CO gas mixtures, H2 gas could enhance the carbon deposition while N2 gas would reduce this phenomenon. The results of X-ray diffraction and chemical analysis demonstrated that the carbons are mainly in the form of cementite (Fc3C) and graphite in reduced sample.

A comprehensive small and pilot-scale fixed-bed reactor approach for testing Fischer–Tropsch catalyst activity and performance on a BTL route

Ruthenium (Ru)-based catalysts were prepared by the sol–gel technique for biomass-to-liquid (BTL) operation and had their performance tested under different conditions. The catalytic study was carried out in two steps using a simple and reliable method. In the first step, the effects of reaction temperatures and inlet H2/CO molar feed ratios obtained from biomass gasification were investigated on the catalyst performance. A set of experimental results obtained in a laboratory fixed bed reactor was described and summarized. Moreover, a simplified Langmuir–Hinshelwood–Hougen–Watson (LHHW) kinetic model was proposed with two promising models, where the surface decomposition of carbon monoxide was assumed as the rate determining step (RDS). In the second step, a FT pilot plant was conducted to validate the catalyst performance, especially the conversion efficiency, heat and mass transfer effects, and system controllability. The results indicated that our catalyst performances under mild conditions were not significantly different in many regards from those previously reported for a severe condition, as especially Ru-based catalyst can be performed to vary over a wide range of conditions to yield specific liquid productivity. The results in terms of the hydrocarbon product distribution obtained from the pilot scale operations were similar with that obtained from the related lab scale experiments.

The effect of gas phase flame retardants on fire effluent toxicity

Abstract Standard industry formulations of flame retarded aliphatic polyamides, meeting UL 94 V-0, have been burned under controlled conditions, and the yields of the major asphyxiants, carbon monoxide (CO) and hydrogen cyanide (HCN) have been quantified. Although both the combination of aluminium phosphinate and melamine polyphosphate, and the combination of brominated polystyrene and antimony oxide, inhibit combustion reactions in the gas phase, this study shows that the phosphorus causes a much smaller increase in the CO and HCN yields than antimony-bromine. The mechanisms of CO and HCN generation and destruction are related to the flame inhibition reactions. Both CO and HCN form early in the flame, and the OH radical is critical for their destruction. Crucial, in the context of the flame inhibition mechanism, is the observation that the phosphorus system reduces the H and O radical concentrations without a corresponding decrease in the OH radical concentration; conversely, the bromine system reduces all three of the key radical concentrations, H, O and OH, and thus increases the fire toxicity, by inhibiting decomposition of CO and HCN. Moreover, while the phosphorus flame retardant is effective as an ignition suppressant at lower temperatures (corresponding to early flaming), this is effect “switches off” at high temperatures, minimising the potential increase in fire toxicity, once the fire develops. Since flame retardants are most effective as ignition suppressants, and at the early stages of flaming combustion, while most fire deaths and injuries result from toxic gas inhalation from more developed fires, it is clearly advantageous to have an effective gas phase flame retardant which only causes a small increase in the toxic product yields.

Reduction of iron and chromium from oxides by carbon

The reaction of iron and chromium oxides with carbon is considered. The decomposition of carbon monoxide is an important source of carbon at the surface of the iron oxides. In the reaction of Cr2O3 with carbon, the first stage includes dissociation of the oxides, with the liberation of atomic and molecular oxygen, and the formation of carbon oxides. Rapid reduction of chromium is ensured by the reaction of Cr2O3 with C3O2 and elementary carbon, which is produced from oxides.

Effect of sulfur compounds on the decomposition of carbon monoxide on red mud

The utilizing of red mud via the carburization of its ferrous components by CO-containing gases of ferroalloy furnaces is investigated. As a result of our experiments, it is established that the red mud of alumina production and exhaust gases of ferroalloy furnaces are quite suitable for performing the decomposition reaction of carbon monoxide after the required preparation. It is found that the presence of hydrogen sulfide has a toxic effect on the catalytic abilities of iron oxides as catalysts of the thermal catalytic decomposition of CO. The mechanism behind the effect of sodium aluminum silicate hydrates entering the red mud on the degree to which sulfur compounds are removed from the ferroalloy gas is revealed. It is established that purification of the ferroalloy gas allows us to increase the carbon content in the final product by a factor of 5–10.

Quantum molecular dynamic simulations of warm dense carbon monoxide

Using quantum molecular dynamic simulations, we have studied the thermophysical properties of warm dense carbon monoxide under extreme conditions. The principal Hugoniot pressure up to 286 GPa, which is derived from the equation of state, is calculated and compared with available experimental and theoretical data. The chemical decomposition of carbon monoxide has been predicted at 8 GPa by means of pair correlation function and the charge density distribution. Based on Kubo-Greenwood formula, the dc electrical conductivity and the optical reflectivity are determined, and the nonmetal-metal transition for shock compressed carbon monoxide is observed around 40 GPa.

Determination of the Surfactant Density on SWCNTs by Analytical Ultracentrifugation

We report on the extensive characterization of single-walled carbon nanotubes (SWCNTs) dispersed in a variety of surfactants, such as sodium dodecyl benzene sulfonate (SDBS), sodium cholate (SC), and three synthesized perylene-based surfactants, by using differential sedimentation in H(2)O and D(2)O. Multidimensional evaluation of the absorption profiles over radius, wavelength, and time allows the determination of the anhydrous specific volumes of the SWCNT-surfactant complexes as well as the concentration of the surfactant reservoir in free micelles with very slow sedimentation coefficients (<1 Svedberg). Among the perylene bisimide surfactants, the smallest derivative is densely adsorbed on the nanotube backbone with an anhydrous specific volume significantly above that of SC or SDBS. Bulky Newkome dendritic groups on one or both ends of the perylene moiety gradually reduce the adsorption density, in accord with the absolute adsorption between 0.66 and 1.7 mmol surfactant per gram SWCNTs. Furthermore, hydrodynamic analysis reveals that SDBS favors the "tails-on" configuration. The distribution of sedimentation coefficients of SWCNTs prepared by high-pressure carbon monoxide decomposition (HiPco) is broader and shifted to faster sedimentation than those prepared by using cobalt-molybdenum catalysis (CoMoCAT), which reflects the polydispersity in diameter and length.

Enhanced Adsorption Affinity of Anionic Perylene‐Based Surfactants towards Smaller‐Diameter SWCNTs

We present evidence from multiple characterization methods, such as emission spectroscopy, zeta potential, and analytical ultracentrifugation, to shed light on the adsorption behavior of synthesized perylene surfactants on single-walled carbon nanotubes (SWCNTs). On comparing dispersions of smaller-diameter SWCNTs prepared by using cobalt-molybdenum catalysis (CoMoCAT) with the larger-diameter SWCNTs prepared by high-pressure carbon monoxide decomposition (HiPco), we find that the CoMoCAT-perylene surfactant dispersions are characterized by more negative zeta potentials, and higher anhydrous specific volumes (the latter determined from the sedimentation coefficients by analytical ultracentrifugation), which indicates an increased packing density of the perylene surfactants on nanotubes of smaller diameter. This conclusion is further supported by the subsequent replacement of the perylene derivatives from the nanotube sidewall by sodium dodecyl benzene sulfonate (SDBS), which first occurs on the larger-diameter nanotubes. The enhanced adsorption affinity of the perylene surfactants towards smaller-diameter SWCNTs can be understood in terms of a change in the supramolecular arrangement of the perylene derivatives on the scaffold of the SWCNTs. These findings represent a significant step forward in understanding the noncovalent interaction of π-surfactants with carbon nanotubes, which will enable the design of novel surfactants with enhanced selectivity for certain nanotube species.

Separation and Characterization of Double-Wall Carbon Nanotube Subpopulations

Surfactant-encapsulated double-wall carbon nanotubes (DWCNTs) synthesized by the high-pressure carbon monoxide decomposition (HiPco) process were separated by length and electronic characteristics using density gradient ultracentrifugation (DGU). To ensure our study focuses only on the behavior of DWCNTs, dispersed DWCNTs were first isolated following the method of Green et al. [Green, A. A.; Hersam, M. C. Nat. Nanotechnol. 2008, 264, 1], utilizing the differences in buoyant density of DWCNTs from that of impurity single-wall carbon nanotubes (SWCNTs) and multiwall carbon nanotubes contained in the parent soot. By increasing the density difference between the nanotubes and the density gradient medium, we exploited the length-dependent translation of the nanotubes in response to applied centrifugation to isolate narrow length distribution DWCNT fractions. The length-dependent intrinsic optical response of DWCNTs is consistent compared with the previously reported values for SWCNTs. The controlled addition ...