Metal heterogeneous

Pitting is a form of extreme, localized attack. The rate of corrosion is greater at some areas than at others, resulting in holes in the metal. Heterogenous metal... 

Unisar [Union saturation of aromatics] A process for hydrogenating aromatic hydrocarbons in petroleum fractions, using a noble metal heterogeneous catalyst. Developed by the Union Oil Company of California. The first commercial unit opened in Beaumont, TX, in 1969 eight commercial plants were in operation in 1991. 

Multi-metallic heterogeneous catalysts of rare-earth metals (including Y and La) have proved effective [151]. Hou reported complexes of general formula... 

Over Ni at 500-700°C, CH is the main product . Other transition-metal heterogeneous catalysts produce higher yields of C> 1 products. Using the homogeneous catalyst, Rh(CO)j(MeCOCHjCOj), (CHpH) forms in 70% yield ... 

The products of this reaction, an equimolar mixture of H2 and CO (called synthesis gas or syn gas some CO2 may be produced as a by-product), can be used with metallic heterogeneous catalysts in the synthesis of a variety of useful organic products. For example, the Fischer-Tropsch process, developed by German chemists in the early 1900s, uses transition metal catalysts to prepare hydrocarbons, alcohols, alkenes, and... 

On the other hand, the oxidative coupling reaction of CH4 in the presence of O2, even when performed in membrane type reactors,188 is mainly catalysed by metal oxides catalysts.185 Also, oligomerisation, aromatisa-tion, and the partial oxidation apply non-metallic heterogeneous catalysts (such as zeolites). The reader is therefore directed to some excellent reviews on these subjects.189,190 At this point, it is perhaps relevant to introduce the formation of carbon nanofibres or nanotubes from methane, these being catalysed by metal nanoparticles, but at this moment this is not considered as a Cl chemistry reaction. Again we direct the attention of the reader to some reviews on this type of process.191 192... 

The next possible objective is to incorporate increasing numbers of metal ions into DNA and to arrange metals heterogeneously using DNA templates possessing more than two different kinds of artificial nucleobases aligned in a programmable manner. 

The conducted experiments [70,71] demonstrate that PVP-Pd complexes are active, selective and stable catalysts. The composition of such catalysts represents a composite system including Pd(II) and Pd(0). The role of the polymer ligands evidently consists in the stabilization of the particular valent states of palladium which are optimum for the substrate hydrogenation. One can assume that in the given catalytic system, Pd(0) promotes the activation of hydrogen, whereas complex-bound Pd(II) promotes the formation of a tr-allyl complex with unsaturated double bonds of the substrate and thus its activation. Furthermore, pyridine rings promote substrate orientation. This assumption enables polymer-metal heterogenized catalysts to be considered as models of catalytic enzyme systems. 

The rediscovery of lanthanides, about 190 years after their first appearance, in the catalysis field now stimulates the study and the interest in these elements at a high level for many applications. In the absence of serious problems coming from purity, availability, toxicity, and cost, the performance of lanthanides appears in many cases favourable with respect to that of the more conventional d-transition metals. Heterogeneous Ln-containing catalysts show unique behaviour in hydrocarbon cracking and are now proposed for many other industrial processes. Homogeneous catalysts based on lanthanides, as competitors of other already applied transition elements. 

Here, we compare three different catalytic systems used to carry out the catalytic oxidation of ammonia gas-phase oxidation over transition-metal heterogeneous catalysts, gas-phase oxidation within zeolites and electrocatalytic oxidation of ammonia. 

Medford AJ, et al. From the Sabatier principle to a predictive theory of transition-metal heterogeneous catalysis. J Catal 2015 328 36-42. 

As mentioned in section 1 the evaluation of the structure/activity relationships of metallic heterogeneous catalysts requires a very accurate geometric and electroruc description of the metallic nanoparticles. These particles are usually described by simple geometric structures. In our work, the Pd NPs are non-conventional in size (higher than 15 nm) and offer the possibility to establish a well-defined geometric model for each... 

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