0.5% Pd on alumina

Grunwaldt et al. (2003b) reported XAFS measurements recorded during palladium-catalyzed alcohol oxidation in supercritical CO2. A commercial shell-impregnated catalyst consisting of 0.5 wt% Pd on alumina was used for benzyl alcohol oxidation (to benzaldehyde) in supercritical CO2 with pure O2 as oxidant. The conditions were 353 K and 150 bar. The results are summarized in Table 8. The authors reported only Pd XANES data, not EXAFS data, and thus the analysis is limited to information about the average oxidation state of the palladium. 

Hydrogenation of a-methylstyrene to cumene in 0.5% and 1% Pd-on-alumina Petroleum hydrocracking, hydrodenit rogenation, hydrodesulfurization, and hydrogenation... 

Figure 2.9 Kinetics of the hydrogenation of 2,4-dinitrotoluene. Initial consumption rates as a function of the averaged catalyst particle diameter at 345 K, PHi = 0.5 MPa, CM = 196 mol nr 3> mM = 20 g for a Pd on alumina catalyst.

The key problem here is the preparation of these plates. The plates contained one inert hydrophobic part close to the hydrogen gas side, and another part consisting of a catalytically active metal on various types of carrier powder. The hydrophobic layer was made of 30-50-fjLm nonporous PTFE particles. The catalyst carrier particles were porous (mean pore diameter of 10 nm) with a particle size of about 5 p.m. The catalytic material was of three different types 10% Pd on alumina, 10% Pd on carbon, and 1.9% Pd on Ni0/Si02. In addition to these powder materials, the plates contained nets of nickel wire (0.16 mm) or glass fibers (0.2 mm) as reinforcement. The catalytic plates were prepared... 

Fio. 6. Concentration of octalins relative to decalins as a function of conversion during the hydrogenation of naphthalene or tetralin at 1000 psig hydrogen pressure over 0.6% metal-on-alumina or 5% metal-on-charooal catalysts. 0> Naphthalene, Rh/Al203, 26° , tetralin, Ru/C, 25° A, tetralin, Ru/AlsOa, 25° A, naphthalene, Pd/C, 100° , naphthalene, Pt/AlaOa, 200° , naphthalene, Ir/C, 25°. 

The reaction considered was the catalytic oxidation of ethyl alcohol, dissolved in an aqueous alkaline solution, to acetic acid As oxidizing agent gaseous oxygen was used The catalyst employed was 0 5% Pd supported on alumina Table 5 gives the properties of the catalyst A previous kinetic study was carried out to measure the intrinsic chemical kinetic parameters of this reaction For this purpose a tubular, packed, flooded reactor was used (oxygen was supplied after its absorption in the solution before entering the reactor) Papers on this subject have already been published Baldi et al [2], [3] ... 

As with any system, there are complications in the details. The CO sticking probability is high and constant until a 0 of about 0.5, but then drops rapidly [306a]. Practical catalysts often consist of nanometer size particles supported on an oxide such as alumina or silica. Different crystal facets behave differently and RAIRS spectroscopy reveals that CO may adsorb with various kinds of bonding and on various kinds of sites (three-fold hollow, bridging, linear) [307]. See Ref 309 for a discussion of some debates on the matter. In the case of Pd crystallites on a-Al203, it is proposed that CO impinging on the support... 

GP 9] [R 16] The reaction rate and activation energy of metal catalysts (Rh, Pt or Pd) supported on alumina particles ( 3 mg 53-71 pm) were determined for conversions of 10% or less at steady state (1% carbon monoxide 1% oxygen, balance helium 20-60 seem up to 260 °C) [7, 78]. The catalyst particles were inserted into a meso-channel as a mini fixed bed, fed by a bifurcation cascade of micro-channels. For 0.3% Pd/Al203 (35% dispersion), TOF (about 0.5-5 molecules per site... 

EDX has, for instance, been used to determine the composition of individual particles in a bimetallic Pt-Pd catalyst on alumina. Electron micrographs show the presence of particles with diameters between 0.5 and 5 nm, while EDX spectra show the X-ray fluorescence peaks of Al, Pt and Pd of the individual particles and enable one to investigate whether all catalyst particles have the same compositions [10,22],... 

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