Decomposition Of Carbon Tetrachloride Research Articles

Decomposition of сarbon tetrachloride under the action of a dielectric barrier discharge of atmospheric pressure in an oxygen atmosphere

In this study, the process of decomposition of carbon tetrachloride (CCl4) vapor in oxygen DBD at atmospheric pressure and its kinetic regularities have been studied. In the course of the experiments, it was shown that the efficiency of the decomposition of carbon tetrachloride in DBD can reach 100%. Depending on the conditions of the experiments, the effective rate constants were equal to (0.16–0.59) s−1, and the decomposition energy yields were (0.001–0.012) molecules per 100 eV of the inputed energy. The main decomposition products were CO2 and Cl2 molecules. The formation of a solid on the internal electrode of the reactor was also found. The substance contains atoms of carbon, oxygen, chlorine (C:O:Cl) = 1:0.38:0.01, as well as hydrogen atoms. The substance also contains functional groups –CH, –CH2, –OH and dimers of carboxylic (chlorocarboxylic) acids. Based on the solution of the Boltzmann equation for electrons, it is shown that for the compositions of a gas containing O2 molecules, ССl4, and decay products, the kinetic and transport characteristics of electrons are the same as in a pure oxygen discharge. Using the kinetic characteristics of electrons and the reaction rate constants the mechanisms of reactions leading to the found reaction products are proposed. It was shown that the primary reaction of destruction is the reaction of dissociation of CCl4 by electron impact, leading to the formation of CCl3• and Cl and the reaction with the O (1D) atom, as a result of which CCl3• and ClO• are formed.

Formation of Carbon Layers by the Thermal Decomposition of Carbon Tetrachloride in a Reactor for MOCVD Epitaxy

Formation of Carbon Layers by the Thermal Decomposition of Carbon Tetrachloride in a Reactor for MOCVD Epitaxy

Формирование углеродных слоев методом термического разложения четыреххлористого углерода в реакторе МОС-гидридной эпитаксии

Abstract A new method for depositing carbon films by the thermal decomposition of carbon tetrachloride (CCl_4) in a hydrogen flux in a reactor for metal-organic chemical vapor deposition (MOCVD) at atmospheric pressure is developed. From the results obtained by Raman spectroscopy, it can be conceived that the carbon layers produced by this method are the disordered nanocrystalline graphite. It is shown that such carbon layers can be used in the technological cycle of the production of gallium-arsenide optoelectronic device structures (among them spin light-emitting diodes with a CoPt injector).

From destructive CCl4 adsorption to grafting SO3H groups onto activated carbon fibers

Nanoporous activated carbon fibers (BusofitTM, BACF) showed effective adsorption of carbon tetrachloride (CTC) vapors. About 2.50 mmol × g−1 of chlorine, in the form of trichloromethyl and chlorine groups, can be grafted onto BACF surface by thermal decomposition of CTC at 450 °C. To obtain solid acids, this chlorinated BACF, the brominated and pristine BACFs, taken for comparison, were subjected to progressive sulfidation, hydrolysis and oxidation reactions for grafting sulfonic groups. By this wet route, sulfonic groups can substitute only 1.1–1.4 mmol × g−1 of the grafted chlorine groups. Nevertheless, solid acids obtained in this way have high catalytic performance in the 2-propanol dehydration to propene. For these catalysts, in the range from 180 to 220°C, a 100% alcohol conversion with 100% selectivity to propene could be reached. Thermoprogrammed desorption and thermal analysis revealed that the pyrolytic chlorination triggers the highest thermal stability of grafted sulfonic groups, and, they can repeatedly act in the dehydration reaction.

Modelling of catalytically oxidative decomposition of carbon tetrachloride on a ZnS nanocluster using density functional theory

Using density functional theory (DFT), adsorption of O2 and co-adsorption of O2 and CCl4 on (ZnS)n clusters (n = 6, 7, 11, 12, 13, 15, 16, 17, 25, 26) and the mechanism of oxidative decomposition of CCl4 on a ZnS nanocluster were investigated. The decomposition of CCl4 without the ZnS cluster was also studied for comparison. The ZnS cluster achieved a significant catalytic effect during the oxidative decomposition of CCl4. It is found that CCl4 in gas phase undergoes a homolytic dissociation process with the activation by ZnS, reacting with O2 to produce a CCl3˙ radical and a ClOO˙ radical first. CO2 and Cl2 are identified as the final neutral reaction products, while COCl2, CO and Cl2O are produced as intermediates. The released energy of the total reaction, 149.83 kcal mol−1, is sufficient to afford the transition energy of the cataluminescence, based on which a novel and sensitive gas sensor for the determination of CCl4 could be constructed.

High-pressure-activated carbon tetrachloride decomposition

The pressure-induced molecular dissociation as one of the fundamental problems in physical sciences has aroused many theoretical and experimental studies. Here, using a newly developed particle swarm optimization algorithm, we investigate the high-pressure-induced molecular dissociation. The results show that the carbon tetrachloride (CCl4) is unstable and dissociates into C2Cl6 and Cl2 under approximately 120 GPa and more. The dissociation is confirmed by the lattice dynamic calculations and electronic structure of the Pa3 structure with pressure evolution. The dissociation pressure is far larger than that in the case of high temperature, indicating that the temperature effectively reduces the activation barrier of the dissociation reaction of CCl4. This research improves the understanding of the dissociation reactions of CCl4 and other halogen compounds under high pressures.

Decomposition of carbon tetrachloride in the reactor of dielectric barrier discharge with different power supplies

The decomposition of CCl 4 in air was investigated at atmospheric pressure in a new type of dielectric barrier discharge reactor. The reactor was powered by three different power supplies: pulsed of low frequency (150–600 Hz), pulsed of 15 kHz frequency with regulated current pulse duration and AC of 6.8 kHz frequency. Maximum conversion of CCl 4 depended on the power supply. 64, 87 and 98% were the maximum achieved conversions of CCl 4 for tested power supplies. The products of CCl 4 conversion and energy consumption depended on power supply system. The chlorine gas was always the main product obtained from CCl 4 . The smallest energy consumption (~0.3 kWh per mol CCl 4 converted) was achieved for pulsed power supply system of low frequency. It was 26 and 230 times less than energy consumption (for similar overall CCl 4 conversion) in AC of 6.8 kHz frequency and pulsed of 15 kHz frequency respectively.

Decomposition of Carbon Tetrachloride and Mono-Chlorobenzen by Using Basic Molten Salts

Decomposition of Carbon Tetrachloride and Mono-Chlorobenzen by Using Basic Molten Salts

Carbon Tetrachloride Decomposition by Pulsed Spark Discharges in Oxidative and Nonoxidative Conditions

The estimation of pulsed-spark-discharge efficiency for destroying unwanted stable gaseous impurities is an object of the present study. A laboratory-scale reactor was developed to study the efficiency of pulsed spark discharges (PSDs) for CCl4 decomposition under oxidative and nonoxidative conditions at atmospheric pressure. In the discharge, chlorine gas was the main product produced from CCl4 in addition to minor amounts of additional products. These products were the following: 1) C2Cl4, C2Cl6, and solid deposits containing chlorine and carbon for the inlet CCl4 + Ar mixture and 2) CO2 with small amounts of COCl2 for CCl4 + O2 mixture. For both diluting gases, it was possible to reach a high CCl4 conversion (98% for CCl4 + O2 and 93% for CCl4 + Ar). CCl4 was chosen as a model substance, because of its simple chemical composition and high stability of its structure. For this reason, the positive result of experiments with CCl4 gave evidence that using the PSD may be an effective way for the abatement of gaseous pollutant emission.

CCl4 Decomposition in RF Thermal Plasma in Inert and Oxidative Environments

The decomposition of carbon tetrachloride was investigated in an RF inductively coupled thermal plasma reactor in inert CCl4–Ar and in oxidative CCl4–O2–Ar systems, respectively. The exhaust gases were analyzed by gas chromatography-mass spectrometry. The kinetics of CCl4 decomposition at the experimental conditions was modeled in the temperature range of 300–7,000 K. The simulations predicted 67.0 and 97.9% net conversions of CCl4 for CCl4–Ar and for CCl4–O2–Ar, respectively. These values are close to the experimentally determined values of 60.6 and 92.5%. We concluded that in RF thermal plasma much less CCl4 reconstructed in oxidative environment than in an oxygen-free mixture.

Estudo da eficiência de degradação de tetracloreto de carbono por plasma térmico e caracterização dos produtos formados

Decomposition of carbon tetrachloride in a DC thermal plasma reactor was investigated in argon atmosphere. The operational parameters such as plasma torch power and argon flow rate versus CCl4 conversion were examined. The CCl4 net degradation was determined by GC-FID, the chlorine produced was quantified by iodometric titration, the solid carbon was characterised by Raman spectroscopy and by BET analysis. The solid carbon collected inside de plasma reactor was submitted to solid/liquid extraction and the desorbed species were identified by GC-MS.

Degradation of carbon tetrachloride in the presence of zero-valent iron

Efforts to achieve the decomposition of carbon tetrachloride through anaerobic and aerobic bioremediation and chemical transformation have met with limited success because of the conditions required and the formation of hazardous intermediates. Recently, particles of zero-valent iron (ZVI) have been used with limited success for in situ remediation of carbon tetrachloride. We studied a modified microparticulate product that combines controlled-release carbon with ZVI for stimulation of in situ chemical reduction of persistent organic compounds in groundwater. With this product, a number of physical, chemical, and microbiological processes were combined to create very strongly reducing conditions that stimulate rapid, complete dechlorination of organic solvents. In principle, the organic component of ZVI microparticles is nutrient rich and hydrophilic and has high surface area capable of supporting the growth of bacteria in the groundwater environment. In our experiments, we found that as the bacteria grew, oxygen was consumed, and the redox potential decreased to values reaching -600 mV. The small modified ZVI particles provide substantial reactive surface area that, in these conditions, directly stimulates chemical dechlorination and cleanup of the contaminated area without accumulation of undesirable breakdown products. The objective of this work was to evaluate the effectiveness of ZVI microparticles in reducing carbon tetrachloride under laboratory and field conditions. Changes in concentrations and in chemical and physical parameters were monitored to determine the role of the organic products in the reductive dechlorination reaction. Laboratory and field studies are presented.

Comparative Study of Decomposition of CCl4 in Different Atmosphere Thermal Plasmas

Decomposition of carbon tetrachloride was studied theoretically in the most commonly used thermal plasma atmosphere such as H2, N2, O2 and water steam. A code developed by the National Aeronautics and Space Administration (NASA) was adopted to calculate the chemical equilibrium distribution and energy consumption of the decomposition of CCl4 in the H2, N2, O2 and water steam atmosphere thermal plasma respectively, with a temperature range of 500 K to 5000 K. In the neutral condition (H2, N2, atmosphere) formation of solid carbon was observed and in the oxygen-atmosphere (O2 and water steam) solid carbon formation disappeared through controlling the ratio of C/O. This indicates that the formation of polycyclic aromatic hydrocarbons (PAHs) is impossible theoretically. The energy consumption in the N2 atmosphere was much higher than that in the H2, O2 and water steam atmosphere at 1500 K.

Modelling of Carbon Tetrachloride Decomposition in Oxidative RF Thermal Plasma

Decomposition of carbon tetrachloride in a RF thermal plasma reactor was investigated in oxygen–argon atmosphere. The net conversion of CCl4 and the main products of decomposition were determined by GC–MS (Gas Chromatographic Mass Spectroscopy) analysis of the exhaust gas. Temperature and flow profiles had been determined in computer simulations and were used for concentration calculations. Concentration profiles of the species along the axis of the reactor were calculated using a newly developed chemical kinetic mechanism, containing 34 species and 134 irreversible reaction steps. Simulations showed that all carbon tetrachloride decomposed within a few microseconds. However, CCl4 was partly recombined from its decomposition products. Calculations predicted 97.9% net conversion of carbon tetrachloride, which was close to the experimentally determined value of 92.5%. This means that in RF thermal plasma reactor much less CCl4 was reconstructed in oxidative environment than using an oxygen-free mixture, where the net conversion had been determined to be 61%. The kinetic mechanism could be reduced to 55 irreversible reaction steps of 26 species, while the simulated concentrations of the important species were within 0.1% identical compared to that of the complete mechanism.

Kinetic Modeling of the Decomposition of Carbon Tetrachloride in Thermal Plasma

Decomposition of carbon tetrachloride in a RF thermal plasma reactor was investigated in argon atmosphere. The net conversion of CCl4 and the main products of its decomposition were determined from the mass spectrometric analysis of outlet gases. Flow and temperature profiles in the reactor were calculated and concentration profiles of the species along the axis of the reactor were estimated using a newly developed chemical kinetic mechanism, containing 12 species and 34 reaction steps. The simulations indicated that all carbon tetrachloride decomposed within a few microseconds. However, CCl4 was partly recombined from its decomposition products. The calculations predicted 70\% net conversion of CCl4, which was close to the experimentally determined value of 60\%. A thermodynamic equilibrium model also simulated the decomposition. Results of the kinetic and thermodynamic simulations agreed well above 2000 K. However, below 2000 K the thermodynamic equilibrium model gave wrong predictions. Therefore, application of detailed kinetic mechanisms is recommended for modeling CCl4 decomposition under thermal plasma conditions.

Low-temperature growth of carbon nanotubes from the catalytic decomposition of carbon tetrachloride.

Multiwall carbon nanotubes (MWNTs) were synthesized via the decomposition of CCl4 in supercritical CO2 at 175 degrees C and 27.6 MPa using an iron-encapsulated dendrimer as a growth catalyst. The average diameter of resultant nanotubes was 20-25 nm, obtained after a 24-h reaction time. Our conditions represent the first application for CX4 precursors, as well as the lowest-reported temperature regime for carbon nanotube growth, allowing the use of other temperature-sensitive catalytic substrates.

Comparative Study of the Decomposition of CCl4 in Cold and Thermal Plasma

Decomposition of carbon tetrachloride was studied in an inductively coupled thermal plasma reactor and in a low temperature, non-equilibrium plasma reactor, in neutral and oxidative conditions, respectively. In neutral conditions formation of solid soot, aliphatic- and cyclodienes was observed in equilibrium, and products, such as Cl2 and C2Cl6 were detected in non-equilibrium plasma. Feeding of oxygen into the thermal plasma reactor depressed both soot and dienes formation and induced the formation of oxygen containing intermediates and products. GC-MS analyses of the gaseous products and the extract of the soot referred to as complex decomposition and recombination mechanism at given conditions. Presence of oxygen in the low temperature plasma reactor results in the formation of carbonyl compounds as intermediers. CO2 and Cl2 revealed as final products of CCl4 decomposition in cold plasma.

Decomposition of Carbon Tetrachloride by a Pulsed Corona Reactor Incorporated with In Situ Absorption

The decomposition of carbon tetrachloride by a wire-in-tube pulsed corona reactor was tested to investigate the influence of the reaction agents H 2 and O 2 on the plasma decomposition of carbon tetrachloride, as well as on the control of unwanted products. It was found that the decomposition of carbon tetrachloride was higher with 2% H 2 in N 2 gas and lower with 2% O 2 in N 2 gas, compared to the decomposition in N 2 atmosphere. Cl 2 and ClCN were regarded as the major products from CCl 4 decomposition in N 2 atmosphere. HCl was the major FTIR-detected product from CCl 4 decomposition in a 2% H 2 /N 2 gas mixture, whereas the products CO 2 , CO, and COCl 2 were detected when carbon tetrachloride was decomposed in a 2% O 2 /N 2 gas mixture. To prevent the production of unwanted byproducts such as ClCN and COCl 2 from CCl 4 decomposition, a combination of nonthermal plasma and in situ absorption by coating a layer of Ca(OH) 2 on the surface of the grounding electrode was proposed. It was demonstrated that the Ca(OH) 2 sorbent in the plasma reactor played an effective role as a scavenger participating in the CCl 4 decomposition reaction by in situ capturing of the unwanted intermediates.

Electron-Beam Decomposition of Carbon Tetrachloride in Air/Nitrogen

Abstract Carbon tetrachloride (CCl4, approximately 10, 50, and 100 ppm) in air and nitrogen was irradiated with electron beams in both the presence and absence of water. The absorbed doses ranged from 1.2 to 18.0 kGys. An absorbed dose of 18 kGy led to approximately 90% decomposition of CCl4 at a concentration of 10 ppm in dry air. The presence of water lowered the decomposition rate in air by 20%, but not in nitrogen. Negative oxygen ions (O2-) formed upon the irradiation of wet air played a role in the oxidation of CCl4. Water molecules became negative cluster ions (O2-(H2O)n) with negative oxygen ions, which depressed the oxidation.

A theoretical study on decomposition of carbon tetrachloride, trichloroethylene and ethyl chloride in dry air under the influence of an electron beam

New experimental data were published in literature regarding CCl 4 , C 2 HCl 3 and C 2 H 5 Cl decomposition in dry air under electron beam influence. Taking into account experimental data theoretical models of those species decomposition were established and computer simulations were performed by the authors of this work to find the kinetics of such processes. The results of the calculations and experimental data show that CCl 4 decomposition depends on delivered dose and initial CCl 4 concentrations. The calculation revealed that recombination of CCl + 4 and Cl − is the source of CCl 3 radicals and that reaction may have an important role in the process of CCl 4 decomposition. A theoretical model of C 2 HCl 3 decomposition in dry air under electron beam influence describes the decay of C 2 HCl 3 and the formation of several products such as Cl 2 , CCl 2 O, CO, CO 2 , HCl and C 2 HCl 3 O. The detailed comparison of experimental and theoretical data shows relatively good agreement in efficiency of C 2 HCl 3 decomposition process, but it can be achieved only with an assumption that the relation between rate constants of C 2 HCl 4 O intermediate product decomposition (C 2 HCl 3 O+Cl and COCl 2 +CHCl 2 ) should be around 20 and C 2 HCl 3 O oxidation rate should be not lower than 7.5×10 −11 cm 3 /mols. All those rate constants are not yet established experimentally. The results of the calculation of C 2 H 5 Cl decomposition and the data obtained experimentally were compared. The temperature, gas pressure, initial C 2 H 5 Cl concentration and dose range were equal in both cases. An elaborated model allow us to obtain quantitatively similar results as the experiments, but the degree of C 2 H 5 Cl decomposition for certain dose levels is significantly higher in experimental data. It is quite probable that some important processes have not been included to the theoretical model.