Direct impregnation

Rare Earths and Alumina. A much easier and cheaper way of getting the SO2 removal enhancement from rare earths that was observed with the well-exchanged rare earth Y zeolite was to add rare earths, especially cerium, by direct impregnation to high alumina cracking catalyst (24). 

Despite the different impregnation methods, the surface areas are close to each other as can be seen in Table 3.5. The direct impregnated catalyst has a somewhat... 

When the catalysts were evaluated in the pilot unit it was found that the product yields were influenced by the selected impregnation method. The maximum naphtha yield (50.7 wt%) occurred at 76.5 wt% conversion for the standard impregnated catalyst. For the direct impregnated catalyst the maximum naphtha yield (50.9 wt%) occurred at a somewhat lower conversion (75.8 wt%). The comparison of product yields from the two impregnation methods shown in Table 3.6 is made at constant conversion (76.5 wt%). The hydrogen yield as well as the dry gas yield is slightly... 

These catalysts were modified by adding non-volatile inorganic acids and their salts, namely orthophosphoric acid, boric acid, barium sulfate, sodium silicate, barium nitrate, and hydrofluoric acid. The additives were added to the finished catalyst by direct impregnation from solution. The presence of the additives did not alter the specific surface or the geometric structure of the final preparations. 

In studies of dual-functional catalysis the mixed catalyst technique has many advantages, two of which are mentioned. (1) It allows separate and independent preparation of each component for example, a platinum preparation can be made in any manner desired in order to obtain a certain platinum activity without regard to what such procedures might do to the acidic properties of the oxide base, this interdependence always being a matter of concern in conventional direct impregnation techniques. (2) A component s relative activity contribution can be flexibly varied in a perfectly known and controllable manner by simply varying its bulk amount in admixture with the other. 

Figure 11 shows conversion to iso-heptanes to be negligible for (0.5 wt. %) platinum supported on activated carbon (Pt/C) as the only catalyst, and also for (0.4 wt. %) platinum on silica-gel (Pt/Si02). No detectable conversion was obtained with silica-alumina. A mechanical mixture of either of the Pt-bearing particles with silica-alumina of about 150 m.Vg-surface area, both in millimeter diameter particle size (1000m), immediately resulted in appreciable isomerization ( SiAl with Pt/C SiAl with Pt/Si02). Isomerization increases rapidly for smaller component particle sizes, of 70/i and S i diameters. It approaches the performance of a silica-alumina that has been directly impregnated with platinum, and which has... 

P. S. Nix and S. Lucki, at our laboratories, have demonstrated (unpublished) the ability of separate platinum and acidic catalysts, as a mixed composite, to perform the skeletal transition from ethyl-benzene to xylenes under hydrogenative conditions (pn, = 11.8 atm., Peb = 1.2 atm. 427 C, r = 3.3 sec.) with 40% conversion to xylenes. Yet at the same temperature, but at atmospheric pressure where production of cyclo-olefin intermediates is not favored, they obtained no measurable conversion even with platinum directly impregnated on the silica-alumina. 

Majewski W, Perrut M. On-line direct impregnation of natural extracts. In Perrut M, Reverchon E, eds. Proceedings of the 7th Meeting on Supercritical Fluids, 2000 779-780. 

Cordierite monoliths were coated with an alumina washcoat and stabilised at 550°C. Some of the samples were then immersed in either an aqueous solution of cerous or cobalt nitrate, dried and calcined in air at 550°C at which the metal nitrates decomposed into their oxides [11]. The samples were weighed and the procedure was repeated until 40 mg of the metal oxide had been deposited onto the alumina washcoated monolith samples. Pt and Pd were applied by direct impregnation using aqueous solutions of HaPtCla and PdCb followed by diying and calcination in air at 550°C [8]. The Pt and Pd loadings (2.0 and 1.09 mg, respectively) of the catalysts were equal on molar basis. The nominal composition of the eight catalysts prepared are listed in Table 1. 

Neither of these two materials is suitable for direct impregnation with... 

Fig. 2. The effect of Pt concentration and sol type on catalyst efficiency (Pt applied by direct impregnation).

Figure 3 a shows that wash-coat of Pt-coated TM gives a much steeper increase in CO conversion with temperature than wash-coat of TM directly impregnated with Pt. 

Figure 3 b shows that for wash-coats of Disperal the situation is the reverse namely that direct impregnation and adsorption results in lower light off temperature and faster response to increase in temperature than wash-coat of Pt coated alumina. Figure 3 c also demonstrates dramatic differences in efficiency of Pt applied by different methods. 

Direct impregnation of silica with Pt and wash-coat of Pt-coated alumina result in low efficiencies whereas Pt-coated silica and direct impregnation of alumina with Pt give catalysts with high efficiencies. 

The catalytic performance of Pt on silica, applied by direct impregnation or using Pt-coated silica sol, is as high as that of Pt on alumina, applied by adsorption or direct impregnation. 

Similar results were recently published for the continuous-flow gas-phase hydroformylation of propene [51]. This time, the supported system was prepared by direct impregnation of an unmodified silica gel with methanol solution containing [Rh(CO)2(acac)j, the ligand, and the IL. The sulfonated xantphos used in this investigation must be added in large excess (10-20 equiv. per Rh) to afford the expected selectivity for the linear aldehyde n/i = 16.9). The performance of the optimized catalytic support remains stable up to 5 h before a decrease in activity and selectivity was observed. This work was also completed using other ligands derived from the series developed in classical biphasic IL systems, and applied to the continuous hydroformylation of propene and 1-octene [52]. 

Ordered mesoporous carbons, prepared by nanocasting, have also been used successfully as templates for the synthesis of hierarchical zeolites [159, 160). This is the case of CMK-3, an ordered mesoporous carbon attained by nanoreplication of pure silica SBA-15. The hierarchical zeolites obtained by employing CMK-3 as a template mainly present supermicropores or small mesopores with a size around 2 nm. The textural properties of the hierarchical zeohtes can be tuned by changing the type of CMK-3 carbon used. A modification of this method consists of directly impregnating the composite SBA-15-carbon or MCM-41-carbon with TPAOH and leaving the mixture crystallizing hydrothermally under steam. After calcination, a mesoporous ZSM-5 is formed with mesopore sizes around 3.5 and... 

Alumina foams have been directly impregnated for propane CPO and OSR [13, 14, 40] to yield 0.01 wt.% rhodium. The catalyst on the foam body, which was 15 mm in diameter, 7 mm long and contained 400 cells per square inch (84% porosity), showed optimum performance at an oven temperature of700 °C and good stability under CPO conditions (C O = 0.8), even though a remaining hot spot of more than 200 K was observed in the foam. Under OSR conditions (C 0 = 0.5 and steam to carbon ratio = 1) only a 150 K hot spot was observed. However, the catalyst deactivated more rapidly, maybe due to the increase in byproduct formation. Complete homogeneous conversion was observed at an oven temperature of 800 °C... 

At the online-impregnation process (see section Direct impregnation technology ) the polymer is heated and melted with an extruder (external) and transported to an impregnation tool near the mandrel or directly on the mandrel. To reach a good bonding between the incoming molten material... 

For thermoplastic filament winding two main technologies can be differentiated. First is the direct impregnation technology in which fibers and... 

The second case, for example shown by Christen and coworkers, - involves a direct impregnation process in which the polymer coating is directly extruded and placed at the mandrel. The principle of the technique... 

Direct impregnation process chains (top polymer extruded and placed on the mandrel bottom melted polymer is pressed through a heated impregnation unit). 

Direct impregnation with multi feed configuration 1 Outer liner, 2 Inner liner, 3 Guiding tool, 4 Fibers axial, 5 Fibers circumferential. (Courtesy of COMAT Composite Materials GmbH, Germany.)... 

Christen, O., Beresheim, G., Neitzel, M. and Rasche, C., Thermoplastic winding with direct impregnation Cost-effective production of pressure cyhnders , Kunststoffe Plast Europe, 1999, 89(4), 18. 

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