4 edition of Oxygen pathways on unpromoted and chlorine inhibited silver epoxidation catalysts found in the catalog.
Oxygen pathways on unpromoted and chlorine inhibited silver epoxidation catalysts
Christopher Jason Bertole
by National Library of Canada = Bibliothèque nationale du Canada in Ottawa
Written in English
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These catalysts are capable of selectively extracting a hydrogen atom by breaking a C H bond in the allyl position and if necessary replacing it with an oxygen atom. Industrial catalysts are generally multi-component (for example, Bi-Mo oxides, used in the synthesis of acrylonitrile from propylene, contain various promoters such as Fe, Cu, W. Written by internationally acclaimed experts, this textbook includes fundamentals of adsorption, characterizing catalysts and their surfaces, the significance of pore structure and surface area, solid-state and surface chemistry, poisoning, promotion, deactivation and selectivity of catalysts, as well as catalytic process engineering.
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A rare exception limited to gas phase is the ethylene epoxidation using bulk silver as a heterogeneous catalyst where O 2 achieves dissociative adsorption into atomic oxygen species. Oxygen pathways in ethylene epoxidation over unpromoted and chlorine inhibited silver catalysts were studied between °C and °C.
Steady state dynamic isotope tracing ( + I8O2) was the prirnary technique. Results from the unpromoted catalysts showed three kinetically distinguishable oxygen pools on silver during the steady state Author: Christopher Jason Bertole. The catalyst used in this study was provided by an industrial supplier.
Its preparation corresponds closely to the state oft the art. Such catalysts for ethylene epoxidation consist generally of silver particles ( to 1 μm) supported on α-Al 2 O 3. Usually, they contain between 7 and 20 wt% of silver and are prepared by impregnation of the Cited by: The epoxidation of 1,3-butadiene to epoxybutene (EpB) was performed in a plug flow reactor using a boehmite-supported silver catalyst with molecular oxygen as the oxidant.
Unpromoted silver. 25, 33,34 There are few theoretical studies investigating propylene epoxidation on an oxide phase of the silver catalyst using either a partially oxidized single Ag 2 O like layer on Ag() or an. Surface Science () North-Holland, Amsterdam CHEMISORPTION OF OXYGEN, CHLORINE, HYDROGEN, HYDROXIDE, AND ETHYLENE ON SILVER CLUSTERS: A MODEL FOR THE OLEFIN EPOXIDATION REACTION * Emily A.
CARTER * and William A. GODDARD III Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena. Physical and kinetic methods were used to study the structural, electron, and catalytic properties of silver catalysts for ethylene epoxidation: bulk silver (Ag() and foil), silver powder, and.
The effect of chlorine upon the rates of EtO and COz production and upon the selectivity for steady-state conditions at PE, = Torr, Pot = Torr and T= K over Ag(). 34 C. Campbell, M.T Pafjett /Chlorine promoters and ethylene epoxidation over Ag(!l0) The most obvious conclusion in figs.
2 and 3 is that atomically adsorbed. 1. Introduction. The epoxidation of ethylene to form ethylene oxide is one the most important heterogeneous catalytic oxidation processes. The process employs a silver catalyst supported on α-Al 2 O 3 and promoted by alkalis and halides.
Considerable effort has been devoted to understanding the mechanism of silver-catalyzed ethylene all available surface. ETHYLENE DESORPTION FROM AN UNOXIDISED AND OXIDISED Cs-PROMOTED Ag/a-Al 2 O 3 CATALYST s) Origins of Selectivity in Ethylene Epoxidation on Ag/a-Al 2 O 3 Catalysts M a s s s p e c r e s p o n s e (a r b u n i t Temperature (C) Mass 26 (ethylene) Mass 32 (oxygen) âˆ’ 0 FIGURE The ethylene desorption spectrum.
Chlorine and Caesium Promotion of Silver Ethylene Epoxidation Catalysts. ChemCatChem5 (2), DOI: /cctc Angeles Pulido, Patricia Concepción, Mercedes Boronat, Avelino Corma.
Aerobic epoxidation of propene over silver () and () facet catalysts. Why silver is the unique catalyst for ethylene epoxidation. Journal of Catalysis(2), DOI: / M O Ozbek, I Onal, R A Van Santen. Ethylene epoxidation catalyzed by chlorine-promoted silver oxide. Surface science experiments, DFT calculations, and kinetic isotope effect data are utilized to understand the elementary steps that govern the selectivity of silver catalysts for the partial oxidation of ethylene to produce ethylene oxide.
It is proposed that selective and unselective pathways proceed via a common intermediate, the surface oxametallacycle. Temperature programmed desorption, high-resolution electron energy loss spectroscopy (HREELS), and density functional theory (DFT) were used to investigate the adsorption and reaction of ethylene oxide (EO) on the Ag() surface.
When EO is dosed onto Ag() at K it adsorbs molecularly, desorbing without reaction at ∼ K. On the other hand, when EO is dosed at K, the ring-opening. The only selective catalyst known is based on silver. This catalyst was known as early as the s and has been continuously improved since then in a rather empirical way.
It has been discovered that the catalyst may be promoted by the addition of alkali metal ions. Moreover, the presence of chlorine has a beneficial effect (cf.
Fig. ) . Supported Ag catalysts on silica and corundum have been synthesized applying an improved impregnation technique. The resulting Ag particle sizes can be divided into three categories concerning: (I) bulk-like, (II) nanoparticles of 1–6 nm, and (III) in situ created Ag clusters below 1 nm.
Ag nanoparticles and bulk-like Ag are investigated concerning their pretreatment dependence for CO. Will Medlin, Catalyst design using an inverse strategy: From mechanistic studies on inverted model catalysts to applications of oxide-coated metal nanoparticles, Surface Science Reports, /p, 73, 4, (), ().
The diversity of catalysts is large and encompasses all the known categories of catalyst type: homogeneous, heterogeneous, and biological. This book summarizes the current status in these fields concentrating on rates, kinetics, and reaction mechanisms, but also covers broad topics including modeling, computational simulation, process concepts.
Given the heterogeneous disposition of silver entities, different photo-activation pathways can be simultaneously occurring in our catalysts. First of all, a fraction of smaller silver domains (Figure 1 b–d) with the proper energy levels can be acting as sinks or trap centers for the electrons photogenerated by the CuO semiconductor fraction.
Recently, silver catalysts were proposed as a promising alternative, being less expensive than Au or Pt catalysts and applicable to a wide variety of alcohols. A Ag/SiO 2 catalyst that acts as efficient catalyst (but only in the presence of ceria: 10 wt % Ag/SiO 2 mixed with ceria in a ratio of ) gave the best catalytic performance in.
First‐principles (in Latin ab initio) quantum‐mechanical-based computer simulations can deliver anatomic‐level insight into elementary constituents of phenomena such as chemical knowledge and understanding thus obtained may beused to propose new reaction‐centers with on‐demand tailored catalytic properties.However, this study presents an innovative way to improve the performances of V 2 O 5 /TiO 2 catalysts by the addition of silver.
Three kinds of catalysts were synthesized: Ag/TiO 2, V 2 O 5 /TiO 2 and Ag–V 2 O 5 /TiO 2. The vanadia loading always corresponds to a theoretical monolayer while 9 different loadings of silver were explored.Ceria has been the subject of thorough investigations, mainly because of its use as an active component of catalytic converters for the treatment of exhaust gases.