CO decomposition

Ferro-nickel is produced by the co-decomposition of the carbonyl asfollows ]... 

The authors considered three mechanisms, including (a) a regenerative (redox) mechanism like that of Weibel,359 (b) the associative (formate) mechanism of Shido and Iwasawa360,361 that has some aspects in common with the formate mechanism of Grenoble et al.229 and (c) a CO decomposition mechanism by Yao,345 which was deemed unlikely as CO generally adsorbed on the metal, and does not decompose. 

RATE COEFFICIENTS OF SOME ELEMENTARY REACTIONS INVOLVED IN CO DECOMPOSITION... 

HREM methods are powerful in the study of nanometre-sized metal particles dispersed on ceramic oxides or any other suitable substrate. In many catalytic processes employing supported metallic catalysts, it has been established that the catalytic properties of some structure-sensitive catalysts are enhanced with a decrease in particle size. For example, the rate of CO decomposition on Pd/mica is shown to increase five-fold when the Pd particle sizes are reduced from 5 to 2 nm. A similar size dependence has been observed for Ni/mica. It is, therefore, necessary to observe the particles at very high resolution, coupled with a small-probe high-precision micro- or nanocomposition analysis and micro- or nanodiffraction where possible. Advanced FE-(S)TEM instruments are particularly effective for composition analysis and diffraction on the nanoscale. ED patterns from particles of diameter of 1 nm or less are now possible. 

SWNTs were prepared by high-pressure CO decomposition over the Fe catalyst (HiPco method [13]) at Carbon Nanotechnologies Inc. Houston, Texas, USA. The raw sample was purified by controlled thermal oxidation in air followed by sonication in HC1. The purity estimated by elemental analysis, TGA, XRD and TEM gave in result 99% content of SWNT in the samples studied [4],... 

Gas phase decomposition Decomposition in an oxygen-free environment Typical HiPco (high pressure CO decomposition) 1 (0.9-1.3) Easy purification, commercial, good quality... 

The first full study that showed positive evidence for homolytic fission was made with M CCO) (15). Reaction with X = 02 in decalin led to decomposition but the kinetics were quite clean. Reaction at 125°C under 100% O2 occurred at the limiting rate over a 500-fold range of [Mn2(C0)ig] but reaction under partial pressures of oxygen of 0.21 and 0.053 showed a clear change from almost first-order dependence on [Mn2(C0)ip] at the lowest concentrations to half-order dependence at the highest concentrations. Decomposition under 50% O2 at 155°C was unaffected by CO. Decomposition under Ar at 155°C or under CO at 170 C showed half-order... 

Before the additional CO is added, the system is at equilibrium, which means that the rate of CO formation and the rate of CO decomposition are equal. The... 

From Figure 2 it is clearly visible that once the reactants are mixed on a molecular level and if the temperature is sufficiently high (T > 800 C) the reaction time is quite short, i.e. below I s mean residence time to get a high CO decomposition (10... 

Fig. 2 Model calculation for the CO decomposition. Model parameters Mean residence time, state of mixedness (described with Bodenstein number Bo) and temperature, Oj concentration 2 Vol% and H2O concentration 15 Vol%, Kinetic data see Table I...

II About 20 to 180 minutes of experiment duration The catalyst is being carbided through CO-decomposition. The CO is formed by the WGS-reaction. The formation rate of organic compounds is very low and preferentially oxygen compounds are obtained indicating a preferred reaction of hydrocarbon species with OH-species. 

On the same catalyst using H2/CO syngas the carbon deposition continues after attaining maximum FT-activity and leads to deactivation. The CO decomposition rate then is too high as related to hydrogen transfer to carbon and chemisorbed species. 

What mechanism of adsorption is occurring on these metals is impossible to postulate. It seems highly probable however that CO decomposition of some type is occurring, such as that observed on niobium and tantalum (see following section). 

In the case of LaCos starting intermetallic in CO + H2 reaction, not only the oxidation of the rare earth but also the carbon provided by the CO decomposition plays a role to form a new active catalyst composed of Co particles dispersed from the La oxide platelets by carbon filaments (Wang et al. 1987). Its catalytic properties are similar to that of Co/La203 but very different from that of Co/Ce02 (Barrault et al. 1986b). In this last case the Co particles are deposited on ceria and an interaction with the support is expected. 

When Pzn+Pco+Pco2 = 1 bar, i.e. / zn< 1 bar and Pco < 1 bar, then it follows from the position of intersection A that the reduction of ZnO in the presence of solid carbon always leads to the formation of gaseous and not liquid zinc. If the gas produced, consisting of Zn, CO and CO2 (less than Zn and CO), is cooled, then because of the position of the Boudouard line, reoxidation should take place to ZnO. However, the CO decomposition taking place during this process is inhibited kinetically, so that cooling the Zn-CO mixture yields liquid zinc. 

Co-decomposition of Ru(77 -C8H]o)( -C8Hi2) and Pt(dba)2 leads to the formation of bimetallic Ru .-Pti j, particles. Platinum-rich particles are fee, whereas ruthenium-rich ones are hep. There is a critical composition Ru3-Pt, for which most of the particles are twinned. In this case, the particles are monodisperse and very small (1.1 nm). This composition corresponds roughly to the limit of solubility of ruthenium in the platinum lattice for bulk alloys. The particles adopt a twinned fee structure with the twinning wall lying in a (111) plane located in the middle of the particle. The homogeneity in the size and shape of the twinned particles suggests a well-defined atomic organization, namely, a twinned truncated octahedron for the particles which can also be described as well-defined clusters. 

The reactivity of carbon species after CO adsorption at room temperature was studied by TPSR. The rate of methane formation as a function of temperature is shown in Fig 3. The peak temperature of CH4 formation on CO TPSR was reported to closely relate to the catalytic activity of CO hydrogenation [16]. The methane formation peaks of Co/A.C. catalyst located at the lowest temperature as 462 K, indicating that this catalyst had the highest CO decomposition activity, resulting in the lowest hydroformylation activity in this study. On the other hand, the lwt% Ru promoted Co/A.C. catalyst had the highest methane formation peak temperature which was 474 K, and its peak area was smaller than the CO desorption peak area, the same with that of 1 wt%... 

Carbon monoxide, CO Decomposition of organic matter, industrial processes, fossU-fuel combustion 0.05 ppm in unpolluted air 1-50 ppm in urban areas... 

Figure 3.34a. The transition state for CO decomposition on a fiat Ru(OOOl) surface .

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