Catalyst supports pretreated carbon

Similarly, Pt catalysts supported on carbon aerogels were used in the combustion reaction of toluene, o-xylene, and m-xylene [41,67]. Carbon aerogels were obtained by carbonization of an organic aerogel at 773 and 1273 K. Both samples were mesoporous, and their microporosity was equally accessible to N2 and CO2 at 77 and 273 K, respectively. Pt was deposited on both carbon aerogels by an incipient wetness technique using an aqueous solution of [Pt(NH3)4]Cl2. The supported catalysts thus obtained were pretreated in different atmospheres to obtain different mean Pt particle sizes. 

Therefore, we examined the properties of the bare carbon fibrils, as well as the properties of catalysts supported on carbon fibrils. To obtain carbon fibril-supported palladium catalysts, a homogeneous deposition-precipitation procedure was utilized. Varying preparation conditions, such as, the atmosphere during drying and the pretreatment of the carbon fibrils, affect the activity in the liquid-phase hydrogenation of nitrobenzene significantly. 

Before preparing these carbon-supported Pt-based catalysts, a support pretreatment toward granular activated carbon with an aqueous solution of NaOH (pH 14) was carried out by immersing for 24 h to promote the anion exchange between the ligand chloride of impregnated metal precursers (K2PtCl4) and the aqueous hydroxide ion (OH ) inside the micropores of the activated carbon [33]. 

In recent years a simplifying attempt to overcome this complexity was to analyze carbon by TPD and to integrate the total CO and CO2 emission and to correlate the results with sample pretreatment and chemical reactivity [33]. The limited validity of such an approach is apparent. As is illustrated below, the chemically complex surfaces which are not described by such crude correlations are those with the highest catalytic activity. In applications of carbons as catalyst support it is immediately apparent that the details of the car-bon-to-metal interaction depend crucially on such details of surface chemistry. This explains the enormous number of carbon supports commercially used (several thousands). A systematic effort to understand these relationships on the basis of modern analytical capabilities is still missing. 

The nano-grained nickel catalysts supported on zdrconia or zirconia-rare earth element oxides are prepared by the oxidation-reduction pretreatment of amorphous Ni-Zr-rare earth element alloys. The conversion of carbon dioxide to methane on the catalyst prepared from amorphous Ni-40Zr alloy is improved by the addition of 5 at% or more rare earth elements (Y, Ce and Sm). 

Gurrath, M., Kuretzky, T., Boehm, H.-P., et al. (2000). Palladium catalysts on activated carbon supports Influence of reduction temperature, origin of the support and pretreatments of the carbon surface. Carbon, 38, 1241-55. 

The use of a support allowing the HPA to be dispersed over a large surface may result in an increase of its catalytic activity. The performance of supported HPA catalysts depends on the carrier, the HPA loading, conditions of pretreatment, among other variables. Acidic or neutral solids such as active carbon, Si02 and ZrOz are suitable as supports [1]. But HPA often leaks out of catalyst supports even in vapor-phase reactions. It is important, for practical purposes, to develop supported catalysts which can be applied to several reactions with no leakage of HPA. 

In the present work, the dependence of the catalytic activity and diastereoselectivity in the hydrogenation of the methylester 1, was studied on rhodium catalysts, as a function of the nature of the support (active carbon, graphite and alumina) and of catalyst pretreatments under hydrogen. 

Pretreated carbon can also affect the activity of other catalysts supported on it. For example, pretreatment of a carbon support... 

The method of deposition-precipitation can also be used for the preparation of catalysts based on inert supports, like carbon nanofibers (CNFs). This has been demonstrated first in the case of the Ni/CNF system (35). To make the CNF surface reactive, the CNFs were first submitted to an oxidative pretreatment by reflux with acidic solution, HNOj (36), or a mixture of HNO3 and H2S04(35). This treatment induced the formation of polar oxygen-containing surface groups resulting from the hydrolysis of anhydric carboxyl groups. The consequence is a better wettability of the aqueous precursor solutions and a decrease of the PZC from a pH of 5 for the untreated fibers to a pH of 2-3. 

Several methods for the incorporation of catalysts into microreactors exist, which differ in the phase-contacting principle. The easiest way is to fill in the catalyst and create a packed-bed microreactor. If catalytic bed or catalytic wall microreactors are used, several techniques for catalyst deposition are possible. These techniques are divided into the following parts. For catalysts based on oxide supports, pretreatment of the substrate by anodic or thermal oxidation [93, 94] and chemical treatment is necessary. Subsequently, coating methods based on a Uquid phase such as a suspension, sol-gel [95], hybrid techniques between suspension and sol-gel [96], impregnation and electrochemical deposition methods can be used for catalyst deposition [97], in addition to chemical or physical vapor deposition [98] and flame spray deposition techniques [99]. A further method is the synthesis of zeoUtes on microstructures [100, 101]. Catalysts based on a carbon support can be deposited either on ceramic or on metallic surfaces, whereas carbon supports on metals have been little investigated so far [102]. 

As the support of catalyst, the pretreatment of activated carbon is necessary. The main purpose of pretreatment is to improve the physical structure and chemical properties of the surface in order to meet the requirements of the catalytic supports. The method of pretreatment includes high temperature (graphitization), acid-alkali, gases and microwave treatment and so on. 

Ammonia synthesis catalyst consisting of ruthenium on a pretreated carbon support with a barium promoter. M. R. Logan, J. J. McCarroll, and S. R. Tennison (British Petroleum Ltd). EP 58531 (1982). 

L. Li, G. Wu, B.Q. Xu, Electro-catalytic oxidation of CO on Pt catalyst supported on ctirbon nanotubes pretreated with oxidative acids. Carbon 44, 2973—2983 (2006)... 

Fe/Ir catalysts In situ Fe and Ir Mossbauer spectroscopy of silica-supported Fe/Ir catalysts with different iron to iridium ratios following pretreatment in hydrogen show that the reduction of the Fe component is enhanced by the presence of Ir metal. The presence of Ir was found to increase the catalytic activity in hydrogenation of carbon monoxide and also to influence selectivity... 

The feasibility of carbon-supported nickel-based catalysts as the alternative to the platinum catalyst is studied in this chapter. Carbon-supported nickel (Ni/C, 10 wt-metal% [12]), ruthenium (Ru/C, 10 wt-metal% [12]), and nickel-ruthenium composite (Ni-Ru/C, 10 wt-metal%, mixed molar ratio of Ni/Ru 0.25,1,4, 8, and 16 [12]) catalysts were prepared similarly by the impregnation method. Granular powders of the activated carbon without the base pretreatment were stirred with the NiCl2, RuC13, and NiCl2-RuCl3 aqueous solutions at room temperature for 24 h, respectively. Reduction and washing were carried out in the same way as done for the Pt/C catalyst. Finally, these nickel-based catalysts were evacuated at 70°C for 10 h. 

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