Catalyst carbon-support interaction

The surface properties of carbon play an important role in the dis persion and the sintering behavior of supported catalyst. The study of iron-phthalocyanine is of particularly interest for the investigation of catalyst-carbon support interactions. The coalescence of PcFe particles on graphitized carbon is considerably lowered by the... 

In the carbon-supported, Pt catalyst, the interaction is attributed to the presence of a Pt-support electronic effect. The specific metal-support interaction is through the electron transfer from the Pt clusters to the oxygen atoms of the surface of the support [222]. In many cases, chemical bonds are formed or charge transfer takes place between the contacting phases. The Pt-carbon support interaction is considered to be beneficial to the enhancement of the catalytic properties and to improve the stability of the electrocatalyst [223, 224]. 

This paper describes the catalytic activity of nickel phosphide supported on silica, alumina, and carbon-coated alumina in the hydrodesulfurization of 4,6-dimethyldibenzothiophene. The catalysts are made by the reduction of phosphate precursors. On the silica support the phosphate is reduced easily to form nickel phosphide with hi catalytic activity, but on the alumina support interactions between the phosphate and the alumina hinder the reduction. The addition of a carbon overlayer on alumina decreases the interactions and leads to the formation of an active phosphide phase. 

Concerning the Fischer-Tropsch synthesis, carbon nanomaterials have already been successfully employed as catalyst support media on a laboratory scale. The main attention in literature has been paid so far to subjects such as the comparison of functionalization techniques,9-11 the influence of promoters on the catalytic performance,1 12 and the investigations of metal particle size effects7,8 as well as of metal-support interactions.14,15 However, research was focused on one nanomaterial type only in each of these studies. Yu et al.16 compared the performance of two different kinds of nanofibers (herringbones and platelets) in the Fischer-Tropsch synthesis. A direct comparison between nanotubes and nanofibers as catalyst support media has not yet been an issue of discussion in Fischer-Tropsch investigations. In addition, a comparison with commercially used FT catalysts has up to now not been published. 

From the work reported in literature it can be thus concluded that there will be various forms of carbonaceous species, which vary in reactivity, that exist on the catalyst or support during FTS. Some forms of this carbon are active (atomic surface carbide and CHX species) and even considered as intermediate species in FTS. However, it is also clear that especially during extended runs there may be a build up/transformation to less reactive forms of carbon (e.g., polymeric carbon). The amounts of these species may be small, but depending on their location, they may be responsible for a part of deactivation observed on cobalt-based FTS catalysts. The electronic interaction of carbon with the catalyst surface may also result in decreased activity. 

The structure of supported rhodium catalysts has been the subject of intensive research during the last decade. Rhodium is the component of the automotive exhaust catalyst (the three-way catalyst) responsible for the reduction of NO by CO [1], In addition, it exhibits a number of fundamentally interesting phenomena, such as strong metal-support interaction after high temperature treatment in hydrogen [21, and particle disintegration under carbon monoxide [3]. In this section we illustrate how techniques such as XPS, STMS, EXAFS, TEM and infrared spectroscopy have led to a fairly detailed understanding of supported rhodium catalysts. 

Carbon support plays a vital role in the preparation and performance of catalysts since it influences the shape, size and dispersion of catalyst particles as well as the electronic interactions between catalyst and support [154,155]. 

Molecular precursors for tailored metal catalysts, 38 283-392 see also Bimetallic catalysts, cluster-derived Zeolites carbon-supported, 38 389-390 chemical interaction between clusters and supports, 38 295-296... 

Smith and co-workers investigated the effect of metal support interaction on the CF formation on a series of Co-silica catalysts.The metal support interaction was manipulated by addition of either BaO, La203 or Zr02 to silica. The rate of catalyst deactivation was found to increase with the increase in the metal support interaction. Competition between CF formation and encapsulating carbon formation controlled the catalyst deactivation rate. In case of the catalysts with high metal support interaction, the encapsulating carbon formation was dominant and hence led to a rapid deactivation of the catalyst. 

Catalysts for coal liquefaction require specific properties. Catalysts of higher hydrogenation activity, supported on nonpolar supports, such as tita-nia, carbon, and Ca-modified alumina, are reasonable for the second stage of upgrading, because crude coal liquids contain heavy polar and/or basic polyaromatics, which tend to adsorb strongly on the catalyst surface, leading to coke formation and catalyst deactivation. High dispersion of the catalytic species on the support is very essential in this instance. The catalyst/support interactions need to be better understood. It has been reported that such interactions lead to chemical activation of the substrate 127). This is discussed in more detail in Section XIII. 

One of the most controversial issues in AFCs is the formation of carbonates. It is generally accepted that the C02, both originally in the air and formed by corrosion reaction of the carbon catalyst support, interacts with the electrolyte according to the following equation ... 

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