Catalyst supports surface modifications

HI. Gri ard Reagents as Precursors to Catalyst Supports IV. Modification of Heterogeneous Surfaces V. Dialkylmagnesium Reagents in Zicgler-Natta Catalysis References... 

Carbon supports typically undergo chemical or physical activation prior to platinum impregnation. The alteration of surface groups and functionalities on the carbon support can strongly influence the carbon-metal interaction that can directly affect the metal particle size, metal particle distribution, surface morphology of the carbon, and surface impurities that may be present. These parameters have been known to influence the catalytic metal stability and activity of the resulting catalyst. Common surface modifications strategies include chemical oxidation of the carhon or thermal activation to modify the surface structures. 

The selective deposition technique seems a surface modification of oxides. In this regard, the modification of material surface is generally carried out in the field of the catalyst preparation. Catalysts are divided into heterogeneous and homogeneous catalysts. The former is well known to be used in the petroleum industry and almost all catalysts are solid, in particular, the supported catalysts. The supported catalysts are composed of the main... 

The dispersion and solid-state ion exchange of ZnCl2 on to the surface of NaY zeolite by use of microwave irradiation [17] and modification of the surface of active carbon as catalyst support by means of microwave induced treatment have also been reported [18]. The ion-exchange reactions of both cationic (montmorillonites) and anionic clays (layered double hydroxides) were greatly accelerated under conditions of microwave heating compared with other techniques currently available [19.]... 

Zhang Y., Hanayama K., and Tsubaki N. 2006. The surface modification effects of silica support by organic solvents for Fischer-Tropsch synthesis catalysts. Catal. Commun. 7 251-54. 

When controlled nitridation of surface layers is required, as for example in the modification of the chemical properties of the surface of a support, the atomic layer deposition (ALD) technique can be applied." This technique is based upon repeated separate saturating reactions of at least two different reactants with the surface, which leads to the controlled build-up of thin films via reaction of the second component with the chemisorbed residues of the first reactant. Aluminium nitride surfaces have been prepared on both alumina and silica supports by this method wherein reaction cycles of trimethylaluminium and ammonia have been performed with the respective supports, retaining their high surface areas." This method has been applied to the modification of the support composition for chromium catalysts supported on alumina." ... 

For example, the most noteworthy disadvantage of catalytic wet oxidation is the severe catalyst deactivation (Larachi el al., 1999). Hamoudi el al. (1998, 1999) systematically studied the deactivation of Mn02/Ce02 catalyst during wet catalytic oxidation of phenol and the catalyst-surface modifications. It was observed that deactivation was induced mainly by the formation of carbonaceous deposits on the catalyst surface. Ohta et al. (1980) reported that the size of the catalyst particles affected the stabilization of catalytic activity. For granular particles of supported copper oxide, the catalytic activity was decreased after each inn, even after six successive experiments. In contrast, for larger particles the catalytic activity was stabilized after the first three runs. 

Loss of hydrogen and changes in the chemical bonding of hydrogen also accompany the production of activated carbons at the various stages of activation, purification, and controlled surface modification. These carbons are used as supports for precious metal hydrogenation catalysts. 

Ziegler Natia Catalysis. 677 683 catalyst support. 679 681 chemical rcduc anl for TiCJ. 677 679 modification ol hetcrogeiKous surfaces, 681 682... 

The study of the chlorine evolution reaction at the Ru02-modified BDD surfaces conforms to the schemes proposed in the literature for thicker oxide films based on the same catalyst. However, for lower oxide loading, the nanoparticle size and distribution on the support surface cause a somewhat different reaction path, possibly related to the occurrence of chlorine radical spillover. Voltammetric tests on the electrodes after prolonged chlorine evolution experiments showed that the oxide modifications at BDD were quite stable. 

In terms of availability, number, and nature of surface groups, surface area, pore size, pore volume, and form and size of the particles, silica has been undoubtedly the most preferred inorganic support. Suitable modification is possible via the surface silanol groups, which can react either directly with an appropriate metal complex or with an intermediate ligand group. Direct surface bonding has often been practiced, e. g., for the anchoring of metal carbonyl complexes [14] (eq. (11)), carbonyl clusters [26], polymerization catalysts [21, 62], or other special systems, e. g., 7r-allyl complexes [63] or metalloporphyrins [64]. 

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