Influence Of Oxidation Conditions Research Articles

Influence of oxidative conditions on the deactivation of an equilibrium FCC catalyst in the fast pyrolysis of HDPE in a conical spouted bed reactor

This study approaches the continuous catalytic fast pyrolysis of plastics in a flexible and original technology, i.e., a conical spouted bed reactor equipped with fountain confiner and draft tube. The catalyst is an inexpensive equilibrium fluid catalytic cracking (FCC) one. Moreover, operation under oxidative conditions is proposed to solve heat supply to the pyrolysis reactor, as a previous study revealed a remarkable difference in the performance of the cracking catalyst when pyrolysis was carried out under inert (conventional) and oxidative conditions. Therefore, the aim of this paper is to assess the role played in the catalyst stability and deactivation mechanism by the presence of air in the reaction environment. A comparative study has been conducted by operating in long continuous runs under the same conditions (550 °C and a space time of 15 gcatalyst min gHDPE−1) in inert and oxidative atmospheres, i.e., equivalence ratios (ER) of 0 and 0.2, respectively. The evolution of product distribution with time on stream was evaluated. Moreover, samples of catalysts were taken from the reactor at different reaction times to correlate catalyst performance with the deactivated catalyst properties, and therefore progress in the understanding of the deactivation mechanism. The amount and nature of the coke deposited on the catalyst and its influence on catalyst properties was ascertained using thermogravimetry (TG-TPO), Raman spectroscopy, and NH3 and N2 adsorption–desorption techniques. The operation under oxidative conditions improved product distribution, with higher yields of light olefins. Moreover, catalysts activity and stability were also enhanced under oxidative conditions. Therefore, the results obtained involve a step forward towards the scaling up of plastics continuous catalytic pyrolysis.

High-Performance Heterogeneous Oxidative Desulfurization Catalyst with Brønsted Acid Sites

A new heterogeneous catalyst containing two types of active sites, sulfo group and ammonium heptamolybdate, on ASKG silica gel support was synthesized. The influence of oxidation conditions (temperature, reactant ratio, reaction time) on the conversion of a model substrate, dibenzothiophene (DBT), was examined. Conditions were found for exhaustive oxidation of DBT. The catalyst synthesized is stable under the oxidation conditions and preserves its activity in five oxidation cycles. The combination of two types of active sites not only considerably enhances the catalyst performance but also reduces to a minimum the possible washout of molybdenum compounds from the support surface.

Effect of synthesis conditions on CO2 capture of ethylenediamine-modified graphene aerogels

Ethylenediamine-modified graphene oxide-based three-dimensional aerogels were fabricated by one-step hydrothermal technique. The influence of oxidation conditions and starting graphite material was studied by elemental analysis, X-ray photoelectron spectroscopy, Raman spectroscopy and Scanning electron microscopy. The CO2 adsorption properties of modified aerogels were tested. The results show the distribution of oxygen groups and type of GO altered by oxidation conditions and graphite nature induce a different N doping configuration in the modified aerogel and a higher surface utilization factor for the CO2 capture. The GO-based aerogel obtained from expanded graphite exhibited the best performance (2-fold the un-modified one), reaching a value of 1.18 mmol g−1 at 1 bar and 298 K, thus indicating the high potential of the present approach towards enhancing the CO2 capture.

Influence of Oxidation Conditions on the Yield of 2-Substituted Imidazole-4,5-dicarboxylic Acids

Conditions were found which allow 2-alkyl-substituted imidazole-4,5-dicarboxylic acids to be synthesized in preparative quantities by the oxidation of 2-alkylbenzimidazoles with hydrogen peroxide. It was shown that optimal results can be obtained at the concentration of 2-alkylimidazole in sulfuric acid of 1 M and the hydrogen peroxide: 2-alkylbenzimidazole molar ratio of 11: 1. Oxidation under these conditions results in higher yields of the target 2-alkylimidazole-4,5-dicarboxylic acids, including those with a branched alkyl group.

ANTIBACTERIAL ACTIVITY OF SELECTIVELY OXIDIZED LYOCELL FIBERS

The purpose of this research was to study antibacterial activity of selectively oxidized lyocell fibers with incorporated silver particles against gram (+) and gram (-) pathogens. Antibacterial properties were accomplished by incorporation of silver ions into modified lyocell fibers by chemisorption from aqueous silver nitrate solution. In order to improve sorption properties of lyocell fibers, the selective TEMPO-mediated oxidation, i.e. oxidation with sodium hypochlorite and catalytic amount of sodium bromide and 2,2´,6,6´-tetramethylpiperidine-1-oxy radical (TEMPO), was applied. The influence of oxidation conditions оn the amount of sorbed silver, and thus on the degree of antibacterial activity was determined. It was found that the maximum amount of sorbed silver was 0.996 mmol/g cell. The antibacterial activity of the TEMPO-oxidized lyocell fibers with silver particles was confirmed in vitro against two strains: Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 25922). The silver-loaded TEMPO-oxidized lyocell fibers showed better antimicrobial activity against strain Staphylococcus aureus.

ANTIBACTERIAL ACTIVITY OF SELECTIVELY OXIDIZED LYOCELL FIBERS

The purpose of this research was to study antibacterial activity of selectively oxidized lyocell fibers with incorporated silver particles against gram (+) and gram (-) pathogens. Antibacterial properties were accomplished by incorporation of silver ions into modified lyocell fibers by chemisorption from aqueous silver nitrate solution. In order to improve sorption properties of lyocell fibers, the selective TEMPO-mediated oxidation, i.e. oxidation with sodium hypochlorite and catalytic amount of sodium bromide and 2,2´,6,6´-tetramethylpiperidine-1-oxy radical (TEMPO), was applied. The influence of oxidation conditions оn the amount of sorbed silver, and thus on the degree of antibacterial activity was determined. It was found that the maximum amount of sorbed silver was 0.996 mmol/g cell. The antibacterial activity of the TEMPO-oxidized lyocell fibers with silver particles was confirmed in vitro against two strains: Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 25922). The silver-loaded TEMPO-oxidized lyocell fibers showed better antimicrobial activity against strain Staphylococcus aureus.

Efficient Iron-Catalyzed N-Demethylation of Tertiary Amine-N-oxides under Oxidative Conditions

An investigation into the influence of oxidative conditions on the efficiency of opiate N-demethylation using iron powder has been carried out under non-classical Polonovski conditions. This approach involves a two-step process of N-oxidation and subsequent treatment of the intermediate N-oxide hydrochloride with the redox catalyst. Significant improvements in rate and yield have been realized for these reactions in the presence of molecular oxygen. In this context, further rate enhancement was achieved by the judicious addition of small amounts of ferric ions, leading to a concomitant reduction in the amount of the zero-valent iron primary catalyst that is required. This has led to a generalized improved methodology for the N-demethylation of oripavine, codeine, morphine, and thebaine. This protocol can also be carried out in one-pot without the need to isolate the intermediate N-oxide.

A study of the oxidation of titanium hydride powder by measurements of its electrical resistance

The oxidation of titanium hydride powder by air oxygen and the influence of oxidation conditions on the degree of oxidation of hydride particles, specific gas content in the powder, and kinetics of its thermal decomposition were studied. The resistometry method was used to determine the effective activation energy of oxidation of titanium hydride by air oxygen. The content of the surface nonconducting phase formed by titanium oxide and oxohydride films under various oxidation conditions was estimated.

Phosphorylation mediates the proteasomal degradation of the tau protein: influence of oxidative conditions

Phosphorylation mediates the proteasomal degradation of the tau protein: influence of oxidative conditions

Influence of oxidation conditions on the properties of indium oxide thin films

Indium oxide (In 2O 3) thin films have been prepared by thermal evaporation of indium in vacuum on a glass substrate at room temperature, followed by thermal oxidation in air. It was experimentally established that the heating velocity during the oxidation process has a strong influence on the electrical and optical properties of films as prepared. The temperature was increased from room temperature to 450°C, with velocities ranging between 0.1°C/s and 0.5°C/s. In 2O 3 thin films as obtained have been examined for optical transparency function on wavelength. The calculated values of optical band gap range between 2.99 and 3.31 eV. Electrical conductivity measurements have also been carried out on the above oxide thin films as a function of temperature. Both the electrical and optical studies showed that In 2O 3 thin films with higher transparency and electrical conductivity are obtained at higher oxidation velocities. Also, the experimental results show linear dependences of transmission coefficient on the oxidation velocity.

On the kinetics of the generation of point defects in the Si-SiO2 system

The results of studies of the point-defect generation kinetics in the Si-SiO2 system by means of Electron Spin Resonance (ESR) and InfraRed (IR) absorption spectroscopy are presented. The influence of oxidation conditions (oxidation temperature and time, cooling rate) on the defect structure of the Si-SiO2 interface has been studied. It is shown that this influence can be explained by the model of point-defect generation proposed by Tan and Gosele, and the structural properties of the Si-SiO2 system can be improved by an appropriate choice of the oxidation conditions.

Influence of Oxidation Conditions on Polyacrylonitrile-Based, Activated Hollow Carbon Fibers

Polyacrylonitrile hollow fibers are oxidized at three different temperatures and var ious durations, and then further carbonized in nitrogen and activated with carbon dioxide. The influence of oxidation conditions on the properties of the resulting ac tivated hollow carbon fibers is discussed. Activated hollow carbon fibers at the highest oxidation temperature have the lowest mechanical properties, and stick together on the surface due to quick heating during oxidation. The higher the oxidation temper ature, the larger the size of the pores, and the pores are almost always concentrated at the center of the wall of the hollow fiber. However, activated hollow carbon fibers at the lowest oxidation temperature have higher mechanical properties, fewer pores of large size, and larger surface areas, which exhibit greater hysteresis effects in nitrogen adsorbing at low pressure.