Experimental determination of reactor activity factors for structure-sensitive catalyst deactivation

Kinetic hydrogen isotope effects in ethylene oxidation on silver catalysts

Colloidal silver catalysts for oxidation of ethylene

This article is devoted to the consideration of methods for the industrial production of ethylene oxide. Ethylene oxide is produced in large quantities and is primarily used as an intermediate in the production of a number of industrial chemicals, the best known of which is ethylene glycol. The process of producing ethylene oxide is carried out by a direct vapor-phase oxidation process, in which ethylene is oxidized to ethylene oxide by air or oxygen and a silver catalyst at 10-30 atm (1–3 MPa) and 200-300 °C. Ethylene oxidation can be carried out in several ways: air, oxygen under nitrogen ballast, oxygen under methane ballast. The production of ethylene oxide is one of the most dynamically developing. In Russia, the leading place in the production of ethylene oxide is occupied by the enterprise PJSC Nizhnekamskniftekhim. In 2012, the installation for producing ethylene oxide was reconstructed. The reconstruction consisted of transferring the ethylene oxide synthesis stage to methane ballast conditions. A patent analysis was carried out to determine the relevance of this process.

Support participation in chemistry of ethylene oxidation on silver catalysts

Supported silver catalysts for the oxidation of ethylene: The effects of thermal treatment of alumina as catalyst support

High surface area α-aluminas III. Oxidation of ethylene, ethylene oxide, and acetaldehyde over silver dispersed on high surface area α-alumina

Platinum has been shown to be an active catalyst for the dry reforming of methane (DRM), which converts CO2 and CH4 into 2CO and 2H2 (synthesis gases) that can further be processed to produce valuable chemical feedstocks. Catalytic activity is often improved by the addition of promoter atoms, which are typically transition metals or noble metals, such as PtNi and PtSn. Recently, boron has shown to be an effective and low-cost catalyst promoter. Pt/B/SiO2 catalysts were prepared for DRM catalysis and compared with Pt/SiO2 catalysts without boron promotion. Both catalysts had similar surface concentrations of platinum, but the catalytic activity at 750 °C after 14 h for boron-containing catalyst was very high, resulting in nearly 100% CO2 conversion and a H2/CO ratio close to unity, compared to 12% CO2 conversion and H2/CO of 0.35 for boron-free Pt/SiO2. The catalysts were investigated with X-ray absorption spectroscopy (XAS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), and CO2 temperature-programmed desorption (CO2-TPD) to identify the deactivating factors. It was determined that neither platinum nanoparticle sintering nor coking was a significant factor in catalyst deactivation; instead, boron had an effect on the reactive surface groups on the SiO2 support. These surface groups, such as hydroxyls and surface basic sites, enhance the adsorption of CO2 and potentially stabilize intermediate carbonate species, resulting in a high CO2 conversion for boron-promoted platinum catalysts.

The distribution of copper, iron, and sulfur during the oxidation of La Caridad copper concentrate particles under simulated flash smelting conditions was studied in a laboratory reactor. Six wet-sieved size fractions and the unsieved copper concentrate were oxidized at 1123 K and 40% and 70% O2 by volume in the process gas during the experiments. Samples of partially oxidized particles were collected at 0.2, 0.8, and 0.9 m from the point of entry and analyzed in a QEMSCAN® unit to determine the elemental composition within the population of particles. The distribution of the major elements during oxidation was strongly dependent upon the size and chemical composition of the initial particles. Overall, the copper content tended to increase and sulfur content decreased along the reactor length within all sizes. In contrast, the distribution of iron did not follow a general trend, as it was found to increase, decrease, or remain unchanged depending on the particle size. This finding may represent a key feature to further investigate the reaction path followed by particles during flash smelting, especially those associated with particle fragmentation. In general, the larger the particle size was, the larger the change in the content of the major elements within the particle population. Based on the experimental results, particles within a size fraction of <45 µm tended to follow a reaction path consisting of rapid melting followed by the collision and coalescence of reacting droplets during flight. In contrast, particles within the fraction of 45–53 µm tended to react individually. The oxidation behavior of the unsieved concentrate particles showed a combination of both reaction paths.

The oxidation of ethylene over evaporated palladium-silver alloy films: II. Variation of activity with catalyst composition

Catalytic dehydroxylation of glycerol to propylene glycol over Cu–ZnO/Al 2O 3 catalysts: Effects of catalyst preparation and deactivation

Quantifying the dominant factors in Cu catalyst deactivation during glycerol hydrogenolysis

<div class="htmlview paragraph">To derive an effective technique for reducing a greenhouse gas nitrous oxide (N<sub>2</sub>O) emitted from automobiles, we prepared experimental three-way catalysts carrying various types and quantities of precious metals, and investigated their N<sub>2</sub>O generation and conversion characteristics. In view of previous reports on increased N<sub>2</sub>O emissions from in-use automobiles, we deactivated the catalysts in a rapid aging test, and observed the effect of catalyst deactivation on N<sub>2</sub>O generation and conversion by the catalysts.</div> <div class="htmlview paragraph">We found that the concentrations of generated N<sub>2</sub>O decreased as the quantities of precious metals carried by catalysts were decreased and that, accordingly, these low-carrying catalysts are more advantageous from the standpoint of reducing N<sub>2</sub>O generation. However, the concentrations of generated N<sub>2</sub>O increased as the catalysts were deactivated. In palladium three-way catalysts, the N<sub>2</sub>O generation peak temperature shifted higher due to deactivation, and N<sub>2</sub>O generation in the high temperature range also increased.</div> <div class="htmlview paragraph">Regarding the decomposition of N<sub>2</sub>O by three-way catalysts, high precious metal carrying catalysts indicated higher N<sub>2</sub>O conversion rates. However, their N<sub>2</sub>O conversion rates were reduced by catalyst deactivation so that the N<sub>2</sub>O which remained unconverted increased in the temperature range of the most frequent catalyst operation. Thus, catalyst deactivation resulted in an increase in N<sub>2</sub>O emissions from automobiles.</div>

A Comparison Between Epoxidation and Degradation of Ethylene and Propylene over Silver

Epoxide, cyclic ether with a three-membered ring. the essential structure of an epoxide contains an oxygen atom attached to two adjacent carbon atoms of a hydrocarbon. The strain of the three-membered ring makes an epoxide far more reactive than a typical acyclic ether. Ethylene oxide is economically the foremost important epoxide and is formed from oxidation of ethylene over a silver catalyst. it's used as a fumigant and to form antifreeze, glycol , and other useful compounds.

Catalytic oxidation: VI. Oxidation of labeled olefins over silver