Influence of promoters

Recent theoretical studies have demonstrated that it is possible to calculate accurately adsorbate stmcture and energy levels, to explain trends with variations in metal composition, and to interpret and predict the influence of promoters and poisons on the adsorption of reactants. Additional efforts along these lines will contribute greatly to understanding how catalyst stmcture and composition influence catalyst-adsorbate interactions and the reactions of adsorbed species on a catalyst surface. With sufficient development of theoretical methods, it should be possible to predict the desired catalyst composition and stmcture to catalyze specific reactions prior to formulation and testing of new catalysts. 

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. 

Important information on reaction mechanisms and on the influence of promoters can be deduced from temperature programmed reactions [2], Figure 2.8 illustrates how the reactivity of adsorbed surface species on a real catalyst can be measured with Temperature Programmed Reaction Spectroscopy (TTRS). This figure compares the reactivity of adsorbed CO towards H2 on a reduced Rh catalyst with that of CO on a vanadium-promoted Rh catalyst [13]. The reaction sequence, in a simplified form, is thought to be as follows ... 

In general, the influence of promotion may be explained by a geometric (blocking) effect or by the formation of new active sites. We suggest, that in our case the suppression of by-product formation by blocking a fraction of Pt° active sites is of... 

Influence of promoters on the reducibility and adsorption properties of Cu-Cr/A Og catalysts. 

Patema, J.C., Moccetti, T., Mura, A., Feldon, J. and Bueler, H. (2000) Influence of promoter and WHV posttranscriptional regulatory element on AAV-mediated transgene expression in the rat brain. Gene Ther., 7, 1304-1311. Politz, J.C. and Pederson, T. (2000) Review movement of mRNA from transcription site to the nuclear pores. J. Struct. Biol, 129,252-257. 

In this paper we give an overview on the partial oxidation of primary and secondary alcohols to ketones, aldehydes or acids. The influence of promotion on catalyst deactivation will be illustrated using the example of a 5 wt% Pt/alumina partially covered by Bi. 

Figure 3. Influence of promotion on Figure 4. Reaction rate and catalyst the conversion of l-methoxy-2 propa- potential during the oxidation of L-nol (Bi/Ptsurf = 0.2, Pb/Ptsurf = 0.3, sorbose on Pt/alumina and Bi/Pt/alu-Sn/Ptgurf = 0.13, Ag/PtSurf = 0.3) mina (Bi/Ptsurf= 0.5).

Arisawa T, Tahara T, Shibata T, Nagasaka M, Nakamura M, Kamiya Y, Fujita H, Yoshioka D, Arima Y, Okubo M, Hirata I, Nakano H (2008) The influence of promoter polymorphism of nuclear factor-erythroid 2-related factor 2 gene on the aberrant DNA methylation in gastric epithelium. Oncol Rep 19 211—216... 

Finally, let us take a closer look at the influence of promoters on hydrodesulfurization catalysts. In this important refinery technology reaction, C0M0/AI2O3 supported catalysts are used. The schematic reaction sequence is shown in Equation 5-81. 

A successful catalyst development strategy must take the chemical and physical conditions into account, from the outer shape of the catalyst to the pore structure to the active center, and from the chemical composition to the various crystalline phases to the influence of promoters. The reactor type must also be included in an overall view of the process [10]. 

Influence of Promoter Strength in Lnciferase Gene Expression (Table U)... 

J.A. Moreno, G. Poncelet, Isomerization of -butane over sulfated Al- and Ga-promoted zirconium oxide catalysts. Influence of promoter and preparation method, J. Catal. 203 (2001) 453—465. 

TeeMK, Damm I, Miller WL (2011) T ranscriptional regulation of the human P450 oxidoreductase gene hormonal regulation and influence of promoter polymorphisms. Mol Endocrinol 25 715-731... 

Fig. 3.44 Influence of promoter contents on the activity of catalyst after overheating...

Fig. 3.45 Influence of promoter contents on activity of cataiysts after poisoning...

Table 6.7 Influence of promoter on ammonia synthesis rate on 2% Ru/AC catalyst...

Fig. 8.43 Influence of promoter on the abrasion strength of the pre-reduced Fei xO-based cataiysts...

Lapidus, A., Agafonov, Y, Shaporeva, N., et al. (2010). Influence of promoters and oxidants on propane dehydrogenation over chromium-oxide catalysts, in DGMK Tagungsbericht 2010-3, October 4—6, Berlin, pp. 141-148. 

When chlorophenylsilanes are being produced, copper can be effectively replaced by silver. There are several co-catalysts which can elevate the catalytic efficiency of copper or silver. In addition to iron and aluminium, which are always present in crude silicon, the addition of zinc [49] or cadmium [50] has been recommended. The influence of promoters on the reaction is not well understood. 

Escalona, N., Medina, C., Garcia, R., Reyes, P., 2009. Fischer—Tropsch reaction from a mixture similar to biosyngas. Influence of promoters on surface and catalytic properties of Co/Si02 catalysts. Catalysis Today 143, 76—79. 

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