Catalytic testing, experimental

The results of the catalytic tests were expressed as DPM total conversion. These experimental results were compared to theoretical values (Cj), calculated considering, as an approximation, a zero-order reaction and the absence of interactions of any kind between both phases, according to the following expression ... 

This interpretation of the experimental data is supported by the differences observed in the deactivation patterns and carbon contents after test, since one notorious effect of Hjp is the capacity to diminish the deactivation caused by coke deposition on the active sites [21,22]. This is supposed to be due to a reaction with the coke precursors, very likely a hydrogenolysis. In pure silica-aluminas, where no source of spillover is present, no special protection against deactivation should be observed. Indeed, the silica-aluminas lose most of their activity (about 80%) before reaching the steady-state and present the highest carbon contents after catalytic test. On the other hand, in the case of the mechanical mixtures, where spillover hydrogen is continuously produced by the CoMo/Si02 phase and can migrate to the silica-alumina surface, the predicted protection effect is noticed. The relative losses of activity are much lower... 

Figure 40.1. Flammability areas for NH3/02/inert and -hexane/02/inert mixtures. Experimental feed composition used for catalytic tests.

Based on the ACR "virtual" catalytic tests and optimization can be performed using HRS (further details are given in the experimental part). Alternatively the whole experimental space can be mapped (see Fig. 1). After subsequent verification step a high resolution experimental space is created and further optimization takes place by HRS creating 1-3 more catalyst generations. After the last verification procedure the... 

Here, we report the application of this procedure for immobilizing Mucor miehei lipase. A catalytic test was aimed at producing esters by direct esterification reactions with a large range of carboxylic acids (from C4 to C16), and a diversity of alcohols (from C4 to C8). Several reaction model systems are analyzed in order to illustrate the kind of products that can be made by using an experimental preparation of lipase immobilized on POS-PVA particles. 

Catalytic tests have been performed in a 500 ml stainless steel batch reactor under hydrogen pressure using 50 g of presulfided catalyst and 125 g of Safanyia atmospheric residue (SAR), The SAR feed had a specific gravity of 0,977 and contained 4.1 wt % S, 0.25 wt % N, 25 wt ppm Ni, 81 wt ppm V and 15.5 wt % C7-asphaltens, A set of used catalysts (symbol P) has been obtained by varying the pressure between 2 to 15 MPa at reaction temperature of 390 °C, contact time of 1 h and hydrogen flow rate of 30 1/h. Further experimental details are reported elsewhere (30). 

Catalytic tests have been performed in a high pressure fixed bed continuous flow "Catatest unit from VINCI Technologies, France, with the Safanyia atmospheric residue. The experimental conditions employed were a total pressure of 8 MPa, a reaction temperature of 380°C, a liquid hourly space velocity... 

The acid or base strength is defined by comparing the interaction between the sites and reference (probe) molecules. For example, the acid strength is the ability of the site to convert an adsorbed reference neutral base into its conjugate acid. This process may be monitored by following the colour changes of the indicators or by such techniques as IR or NMR spectroscopies. Several criteria must be considered in the selection of these probes their pK value must be adapted to the acidity or basicity of the surface under study the size of the probe molecules should ensure that all sites are readily accessible finally, the probe should be selected so that its interaction with the surface is easily studied by the available experimental techniques. Catalytic test reactions are sometimes used... 

After several unexploitable catalytic tests because of either a too low activity of the surface or an immediate consumption of the prenal, < standani experimental conditions have been determined ... 

NO conversion of one of the catalysts under conditions that were totally different from those used in the catalytic tests where it was employed as part of the model development. By comparison of the predicted NO conversion values with those determined experimentally the confidence level of the model was determined. 

The selective oxidation of D-glucose into gluconic acid was selected as catalytic test reaction. The reactor vessel and the experimental conditions were described in detail elsewhere [8]. The pH of the reaction mixture was kept at a constant value in the range 9.25-9.45 by adding a 20 wt.% aqueous solution of sodium hydroxide with an automatic titrator (Stat Titrino 718) from METROHM. The base consumption was recorded as a function of time. 

Catalytic tests were made using a quartz continuous flow reactor (5 mm inner diameter) loaded with 0.5 g of catalyst in the form of small pellets (0.1-0.3 nun range). The feed composition was 3% toluene with a stoichiometric CVtoluene ratio (1.5). The space-velocity was set to 14500 h to avoid diffusional limitations. Tests were made in the 250-550°C range, but above 500°C severe deactivation of the catalysts occurs. Before the tests the catalysts were conditioned at 450°C for 6 h in the presence of standard feed. The axial temperature profile was determined by a thermocouple inserted in the catalytic bed. Preliminary experimental tests were made to ensure the absence of mass and heat diffusional limitations on the reaction rates. 

Then the sequential steps mentioned in section 2 were repeated till the precision was satisfied, and the catalytic results corresponding to the optimal composition were Xp 80.0%, Sacn 53.7% and Yacn 43.0%. For this case the iteration was undertaken thrice, in each one four local optimal composition were predicted and then tested experimentally. The best acrylonitrile yields (including both results of calculation and eiqieriments) in each iteration are shown in Figure 5. 

The selective oxidation of D-glucose into gluconic acid was selected as catalytic test reaction. The reactor vessel and the experimental conditions were described in detail elsewhere... 

Bismuth was found systematically to dissolve in the reaction medium during the catalytic tests. In contrast with bismuth, palladium dissolution was never detected under the present experimental conditions. As indicated in line 7 of table 3, bismuth dissolution increases with the Bi/Pd molar ratio and, when the gluconic acid yields are normalized with respect to the amount of dissolved bismuth (line 13), the highest value is observed for the 5Pd2Bi/Co catalyst. 

The reaction was studied in the following experimental conditions 0.2 g of catalyst was mixed with 0.8 g of a alumina, the global flow rate was 10 L h. The space velocity was kept constant at 25000 h during the catalytic testing. 

The details of the synthesis of the V-MFI samples from acidic and alkaline media and the V-MEL samples from alkaline media have already been reported [6,7], The procedure used in the synthesis of vanado-aluminosilicates with BEA structure has also been reported [8], Similarly, the experimental methods adopted for the various characterization techniques and the catalytic tests have also been reported already [6,7],... 

Catalytic tests in flow reactors Experimental conditions... 

Physico-chemical characterizations of the monoliths were performed on the powder of the crushed monoliths (TPR) or directly on the honeycomb substrates opportunely sectioned ((BET, XPS, SEM/EDAX). Details on the characterization techniques are reported elsewhere [4-6]. The experimental apparatus used to perform the catalytic tests is described elsewhere [9]. Before the catalytic tests the samples were pre-treated in situ under flowing O2 (10 vol.% in N2) at 400 °C for 30 min, then cooled to room temperature in nitrogen. CO oxidation only tests were carried out over the two prepared monoliths (mono 1 and 2) by feeding the mixture CO 1750 ppm, O2 10 vol.%, N2 balance. Combined light-off experiments were performed over the Pd-Pt promoted substrate Pd-Pt/mono 2) by feeding the reaction mixture CO 5000 ppm, CH4 400 ppm, O2 1.0 vol.%, N2 balance. In all the experiments, the GHSV was set at a realistic value, i.e. 100,000 h ... 

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