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Catalyst preparation parameter determination

The current work indicates that sulfided platinum catalysts are, in general, more active and selective than Pt, Pd, or sulfided Pd catalysts for reductive alkylation of primary amines with ketones. The choice of the catalyst preparation parameters, especially the support, plays a major role in determining the performance of the catalyst. Diamines, especially of lower molecular weight, tend to react with ketones even at room temperature to form heterocycles such as imidazolidine, diazepanes, and pyrimidines. Hence, a continuous reactor configuration that minimizes the contact between the amine and the ketone, along with a highly active catalyst is desired to obtain the dialkylated product. In general, sulfided Pt appears to be more suited for the reductive alkylation of ethylenediamine while unsulfided Pd or Pt may also be used if 1,3-diaminopropane is the amine. [Pg.165]

Often it is essential to characterize the formation of a catalytically active state of a highly dispersed phase by XRD under reactive atmospheres. Investigations of reduction and calcination processes, for example (Thomas and Sankar, 2001 Sankar et al., 1991), guided the determination of recipes for catalyst preparation (Gunter et al., 2001d Kirilenko et al., 2005 Ressler et al., 2001, 2002 Wienold et al., 2003) in a complex parameter space. [Pg.283]

The efficiency of the above catalysts for NO reduction depends definitely on the kind of metals and their loadings onto supports, the type of reductants and the feed gas composition employed as well as on the kinds of supports and structure of the parent zeolite and its historical nature during preparation. In particular, the effect of the presence of H2O and SO2 in the exhaust gas from mobile sources is well documented on the maintenance of time-on-stream deNOx activity of SCR catalysts, and their resistance to these co-existing gases is an essential parameter determining successful applications to engine sources. The durability of the documented catalysts under hydrothermal conditions should also be considered to verify if those were applicable to controlling vehicle NOx... [Pg.125]

Parameters Determining Selectivity. We believe that the peculiar selectivity of Pt-H-mordenite for hydrocracking normal and near-normal paraflSns in high-boiling feedstocks could not have been predicted from the known adsorption and diffusion properties of mordenites loc. cit.). However, extensive catalytic studies on the preparation of low-pour-point petroleum fractions have suggested to us that catalyst selectivity depends... [Pg.405]

Relatively recent results indicate that the mode of the interfacial deposition and the local sfructure of the iimer sphere complexes, eventually formed, may influence remarkably the surface characteristics and thus the catalytic behavior of the final supported catalysts [2,5-7]. In view of the above, it is clear that the determination of the mode of interfacial deposition and the local stmcture, which predominate under given impregnation conditions, may be proved an extremely useftil tool for catalyst preparation, because it allows their control by regulating the impregnation parameters. [Pg.810]

The performance of a catalyst for a certain application depends on a number of important parameters. As noted earlier, the characteristics of the catalyst support chosen has a strong influence. Additionally, some other key factors coming from the preparation process determine the final performance, especially selectivity and activity. Those factors are the precious metal loading, the metal distribution of the precious metal crystallites, the size of the crystallites and their spatial distribution, the oxidation state of the metal, and the addition of modifiers. The mefal loading of a cafalysf is typically in the range 1 to 20% for precious metal powder catalysts. A fuel cell catalyst can have metal loadings of up to 60%. This parameter can easily be adjusted by the amount of precious metal used during catalyst preparation. [Pg.545]

Different preparation methods and preparation conditions as well as pretreatment conditions lead to remarkable effects on the structure of the catalyst, which influence the catalytic performance. The coprecipitation methods implicate high flexibility, but entail high complexity. So, not only chemical composition, but also the preparation parameters and activation conditions determine the resulting properties of the final catalyst, which makes reproducible preparation difficult, especially when different phases are present. [Pg.348]

Corrosion, determination of corrosion products on iron and steel surfaces, adsorption properties of ion exchangers, catalysis, surface reactions on catalysts, coatings, effect of the preparation parameters on the phase composition and the short-range order... [Pg.1442]

Hence, any one of these two parameters, in the present study, can be used to represent the other. In catalyst preparations where Pt or Ir dispersions in /- alumina can not be practically determined using the known techniques of chemisorption of gases, e.g., Hz or CO, the metal distribution data can be used Instead. [Pg.1135]

In MD simulations, the molecular adsorption concept is used to interpret the Pt-C interactions during the fabrication processes. The Pt complexes are mostly attached to the hydrophilic sites on carbon particles, viz. carbonyl or hydroxyl groups [108]. The adsorption is based on both physical and chemical adsorption. Carbon particle preparations, impregnation, and reduction are three main steps of the catalyst preparation. The point of zero charge (PZC) determines the pH range at which the impregnation step should be carried out. The PZC is an important parameter in catalyst preparation. [Pg.400]

Decalactone-co Caprolactone. Copolymers of -decalactone and caprolactone were prepared in bulk at 130°C with stannous octoate as catalyst. For accurate determinations of copolymer compositions H-labeled -caprolactone was used. The copolymerization parameter for caprolactone was found to be 2.2, whereas the parameter for -decalactone was practically zero. The latter finding agrees with homopolymerization experiments which established that -decalactone polymerizes extremely slowly to low molecular weight products ([n] 0.4 dl/g). [Pg.262]

The copolymerization of a mixture of DTC and CL at low temperatures resulted in A-X-B-type copolymers, where A was a PDTC block, B a PCL block, and X a random DTC and CL block. As a consequence, DTC-CL and CL-DTC heterodiads were observed in the C NMR spectra. The concentration of heterodiads was seen to increase with temperature such that, at 80 °C, a random copolymer was obtained. From a mechanistic point of view, the active species of each monomer would be eligible to react with both DTC and CL. In case of using Mg-, A1-, and Zn-based catalysts, transesterification plays a minor role, and the miaostructure of the copolymers prepared is determined by the nucleophilicity of the active species and the electrophilicity of the monomer alone. For alkoxide (Li", K ) initiators and Sn-based catalyst, transesterification takes place and determines the final polymer microstructure, besides the copolymerization parameters, especially at higher temperatures. [Pg.291]


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See also in sourсe #XX -- [ Pg.18 ]




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