Experimental catalysts

Ethylene can be oxidized to ethylene oxide over a silver-alumina catalyst. Experimental data were obtained at 260 C and atmospheric pressure (Wan, Ind Eng Chem 45 234, 1951). Selected data are tabulated. Inlet... 

The utilization of polar polymers and novel N-alkyl-4-(N, N -dialklamino)pyridinium sedts as stable phase transfer catalysts for nucleophilic aromatic substitution are reported. Polar polymers such as poly (ethylene glycol) or polyvinylpyrrolidone are thermally stable, but provide only slow rates. The dialkylaminopyridininium salts are very active catalysts, and are up to 100 times more stable than tetrabutylammonium bromide, allowing recovery and reuse of catalyst. The utilization of b is-dialkylaminopypridinium salts for phase-transfer catalyzed nucleophilic substitution by bisphenoxides leads to enhanced rates, and the requirement of less catalyst. Experimental details are provided. 

Catalyst Experimental concentration of formyl species 10 7 mole g 1 cat. Calculated concentration of formyl species 10 7 mole g 1 cat. 

Carbonylation of methoxyoctadienes in the presence of soluble or supported palladium catalysts (Experimental conditions P(CO) = 30 bar T = 100°C substrate/Pd = 50)... 

In the studies of gaseous reactions on solid catalysts, experimental work to determine the concentration of reacting species on the surfaces is undoubtedly important and has been reviewed comprehensively by Wagner [63]. In this section, a brief summary is attempted, emphasizing this aspect of gas—solid reaction. 

Zereini, F., Skerstupp, B., Alt, F., Helmers, E., and Urban, H. (1994). Geochemical behaviour of platinum group elements (PGE) in particulate emissions by automobile exhaust catalysts Experimental results and environmental investigations. Sci. Total Environ. 206, 137—146. 

This is only a short list of possible pitfalls of the use of kinetic rate expressions in practice. Generally it is wise practice to test a catalyst experimentally before using available rate expressions (Chapter 5). The following gives a few examples to give weight to the above remarks. 

Supported metal catalysts generally show an increase in catalytic activity compared to the pure oxide or metal. Yet these systems are not well characterised, owing to the fact that such catalysts typically consist of a range of different supported metal sites, from small clusters to monolayer islands, all with non-uniform distributions in size and shape. One way to begin to understand such complex systems is to attempt to capture some essential part of the full system by developing model catalysts experimentally or using computer modelling techniques. This chapter concentrates on the latter but in the context of the relevant experimental data. 

Figure 13 Adsorption-desorption of NH3 on a model V205-W03/Ti02 catalyst Experimental data and model fit (solid line). T - 220 C. The dots represent the inlet NHj concentration the triangles show the outlet NH3 concentration. The TPD run started at / = 1500 sec. (From Ref. 52.)...

Fig. 14. Experimental demonstration of the effect of diffusion on the measured activation energy of the cracking reaction of cumene on Si02-Al20s catalyst. (Experimental points and slopes expected theoretically due to diffusion effect.)...

Figure 5. Selectivity to the parent olefins(%) as a function of the alkane feeded and of the catalyst. Experimental conditions alkane conversion of 20% reaction temperature of 600 (ethane) or 550 °C (propane and n butane).

This mechanism implies catalyst-oxygen interaction and excludes interaction between carbon and catalyst. It was used to explain successfully the observed features of the carbon dioxide gasification, including the deactivation (by oxidation) of the catalyst. Experimental evidence was presented to support the view that the metal acts as a dissociation centre, producing active species that diffuse across the metal to react at the graphite-metal interface. 

Catalysts may need to be aged for optimal activity. This was noted with the Ti(Oi-Pr)4/(+)-diethyl tartrate catalyst used for asymmetric epoxidation and kinetic resolution [27]. Both addition sequence and aging are essential for proper preparation of the catalyst. Experimentation is necessary to determine if catalytic activity benefits from aging. 

Derivation (1) By high-pressure catalytic synthesis from carbon monoxide and hydrogen (2) partial oxidation of natural gas hydrocarbons (3) several processes for making methanol by gasification of wood, peat, and lignite have been developed but have not yet proved out commercially (4) from methane with molybdenum catalyst (experimental). 

Photocatalytic reduction of C02 to organic compounds was carried out [327] in a semiconductor suspension system under simulated solar power using a Ti02 catalyst. Experimental results show that the photocatalytic activity can be... 

D. Lafarga, M. A. Al-Juaied, C. A. Bondy, A. Varma, Ethylene epoxidation on Ag-Cs/a-Al203 catalyst Experimental results and strategy for kinetic parameter determination, Ind. Eng. Chem. Res. 39 (2000) 2148. 

EE Petersen. The Fouling of Catalysts Experimental Observations and Modeling in Catalyst Deactivation, edited by E E Petersen and J B Butt, Marcel Dekker, Inc., New York, 1987... 

Fourth, at lower temperatures nonreacting extra-index chains of atoms also undergo adsorption on the surface of catalysts. Experimental evidence of flat adsorption was obtained in the precatalytic range of the adsorption of alcohols on alumina. Plane adsorption allows explanation of both asymmetric catalysis and a number of facts of enzymic catalysis. 

Recently, Hada et al. [74] have reported a theoretical study on the reaction mechanism and regioselectivity of silastannation of acethylene with a palladium catalyst. Experimentally, terminal acetylenes react with silylstan-nanes to give highly regio- and stereoselective l-silyl-2-stannylalkenes with tetrakis(triphenylphosphine)palladium as a catalyst [75]. The products are always cis adducts tin adds to the internal position as follows ... 

Deactivation studies on conventional sulfated zirconia at varying partial pressures of n-butane in helium showed two regions of deactivation as reported in the literature. Reaction studies with hydrogen as the diluent gas led to distinct changes in the two regions of activity. These changes could be rationalized by the presence of two active sites on the catalyst surface. A two active site, elementary step bimolecular reaction model is proposed for n-butane isomerization over optimally hydrated sulfated zirconia catalysts. Experimental data... 

The catalyst particles were 0.3 x 0.3-cm cylinders, 10% Ni on alumina. Surface area was 30m /g, and the diffusivity of hydrogen within the catalyst at 25 °C was 0.07cm /s. Is there evidence that diffusion was important Assume Knudsen diffusion in the catalyst pore structure. The rate of addition of deuterium to 2-butyne at 25 °C over a 0.03% Pd/ AI2O3 catalyst was reported to be 0.11 gmol/h-cm3 (catalyst). Experimental conditions were feed, D2 saturated with 2-butyne nt 25 °C catalyst dimension, 40 mesh D ff 0.15 of the bulk diffusivity of 2-butyne in hydrogen at 25 °C. Was intraparticle diffusion important in this experiment Note Persevere in obtaining all the exact numbers you need to do this calculation. They come from various sources, and it takes some time. After all, this is real life). 

Figure 4.7 Conversion (X ) versus time for the esterification reaction of PPSu at 190°C with different amounts of added catalyst. Experimental data (discrete points) and theoretical model simulation results [43].

An old method for preparing esters simply reacts a carboxylic acid and an alcohol in the presence of an acid catalyst. Experimentally, the reaction of acetic acid (21) and butanol in the presence of a sulfuric acid catalyst gives butyl... 

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