Monolithic supports content

The cerium and titanium oxide contents were determined by inductively coupled plasma (ICP) optical emission spectroscopy (Perkin-Elmer Optima 3300DV) of dissolution of the ground catalysts in acid solutions. The composition of the powder samples and monolithic supports are shown in Tables la) and 2 respectively. 

Taking into account the results with the powdered samples, monolithic supports were manu ctured, with CeOi contents between 0-4 wt%. The sihcate binders were necessary for the conformation of these structures [17]. The axial profile and mapping obtained by EPMA-WDS microscopy revealed that Ti and Ce concentration deviation over the wall cross-section were parallel and contrary to Si and Mg, principal components of the binders. This result indicated that cerium was selectively deposited on titania particles and not on the silicates. The Ce02 content added to titania and confirmed with ICP spectroscopy, total pore voliune and BET area for the three monolithic supports, calcined at 500 C for 4 hours are collated in Table 2. 

A platinum content of 0.1 v % was achieved by impregnation of the monolithic supports with an aqueous solution of chloroplatinic acid and subsequent reduction. 

The transformation of straw and agrofood residues with high sulfur and ash content requires the development of materials for sulfur abatement at high temperature, tar cracking and as monolith for syngas production by exothermic or autothermal processes thanks to catalysts supported on materials with a high thermal conductivity. 

Horvath et al. sintered the contents of a capillary column packed with 6 pm oc-tadecylsilica by heating to 360 °C in the presence of a sodium bicarbonate solution [101]. These conditions also strip the alkyl ligands from the silica support, thus significantly deteriorating the chromatographic properties. However, the performance was partly recovered after resilanization of the monolithic material with dimethyloctadecylchlorosilane allowing the separation of aromatic hydrocarbons and protected aminoacids with an efficiency of up to 160,000 plates/m. 

Due to its high photocatalytic activity towards the complete mineralisation of VOCs [7,8] titania in its anatase form is normally used. Using ceramic monoliths with high titania content (50%) the total oxidation of chlorinated organic compounds at low temperature has been demonstrated [9]. However, since the photons from natural light may only penetrate a few microns into the catalyst surface the use of a wash-coating technique, where only a thin active film of titania is applied to the ceramic or metallic support can be considered as an ideal technique to produce maintenance free photocatalytic reactors. 

The activities of the catalysts prepared with the five titanias containing 0.1 wt.% Pt supported on 50 50, wt/wt, titania-sepiolite monoliths are shown in Figure 1. These displayed variations of the maximum conversion, by more than 15%, and maximum conversion temperature, of 25 °C. As all supports used were prepared with the same sepiolite content and the same platinum quantity, the activity differences might be attributed to the differences in the titanias used in the support preparation. 

Catalysts were prepared on Corning EX20 cordierite, open channel monolithic substrates (nominally 62 square channels per square centimeter). High surface area supports were activated with base or noble metal components. The final composition of the fresh catalysts are shown in Table 1, where the metal content is expressed as grams of metal per liter of catalyst (including substrate). 

Fresh and thermally aged catalysts containing mixtures of platinum and palladium were laboratory tested for the oxidation of carbon monoxide, propane, and propylene. For both monolithic and particulate catalysts, resistance to thermal deactivation was optimum when palladium content was 80%. Full-scale vehicle tests confirmed these findings. Catalysts of this composition were developed which, on the basis of durability tests at Universal Oil Products and General Motors, appeared capable of meeting the 1977 Federal Emissions Standards with as little as 0.56 g noble metal per vehicle. The catalyst support was thermally-stabilized, low density particulate. 

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