Mocvd Palladium and Platinum Supported on Alumina Catalysts: Preparation and Characterization

1997 ◽  
Vol 497 ◽  
Author(s):  
Z. K. Lopez ◽  
J. R. Vargas ◽  
M. A. Valenzuela ◽  
D. R. Acosta
Keyword(s):  
Particle Size ◽  
Auger Spectroscopy ◽  
Pt Catalysts ◽  
Hrem Image ◽  
Alumina Catalyst ◽  
Pd Catalysts ◽  
Deposition Zone ◽  
Mocvd Reactor ◽  
Operation Conditions ◽  
Catalysts Preparation

ABSTRACTAn horizontal hot-wall MOCVD reactor was used to prepare palladium and platinum catalysts supported on alumina. A conventional impregnated Pt on alumina catalyst was prepared as comparison. The solids were characterized by XRD, Auger spectroscopy, HREM and H2 -TPR. The operation conditions of the MOCVD reactor were fixed preparing several Pd catalysts until to find the appropriate deposition zone. The particle size of Pt catalysts prepared by MOCVD was at about 7 nm compared with 6 ran obtained with the Pt impregnated catalyst, measured by XRD. The HREM image of the Pt MOCVD catalyst showed a narrower particle size ranging from 1 to 4 nm. After calcination three Pt compounds were detected by TPR, which were attributed to PtO, PtO2 and Pt-Al2O3 interaction in MOCVD preparation. Additionally, a clear reduction of surface oxygens of alumina was also observed.

Particle size effect in liquid-phase hydrogenation of phenylacetylene over Pd catalysts: Experimental data and theoretical analysis

2019 ◽  
Vol 358 ◽  
pp. 520-530 ◽  
Author(s):  
Pavel V. Markov ◽  
Igor S. Mashkovsky ◽  
Galina O. Bragina ◽  
Johan Wärnå ◽  
Evgenii Yu. Gerasimov ◽  
...  
Keyword(s):  
Experimental Data ◽  
Particle Size ◽  
Liquid Phase ◽  
Theoretical Analysis ◽  
Size Effect ◽  
Particle Size Effect ◽  
Pd Catalysts ◽  
Liquid Phase Hydrogenation

Particle size and support effects on the complete benzene oxidation by Co and Co–Pt catalysts

2007 ◽  
Vol 42 (10) ◽  
pp. 3315-3320 ◽  
Author(s):  
Silviya Todorova ◽  
Georgi Kadinov ◽  
Krasimir Tenchev ◽  
Yuri Kalvachev ◽  
Vladislav Kostov-Kytin
Keyword(s):  
Particle Size ◽  
Benzene Oxidation ◽  
Pt Catalysts ◽  
Support Effects

The hydrodynamic filter separator for removal of urban storm runoff

2006 ◽  
Vol 53 (7) ◽  
pp. 243-252 ◽  
Author(s):  
J.H. Lee ◽  
K.W. Bang ◽  
Y.J. Cho ◽  
S.J. Joh
Keyword(s):  
Particle Size ◽  
Loading Rate ◽  
Solid Particles ◽  
Storm Runoff ◽  
Surface Loading ◽  
Loading Rates ◽  
Operation Conditions ◽  
Solids Separation ◽  
Series Of Experiments ◽  
Urban Storm

The majority of storm runoff pollution is trapped in particles smaller than 100 μm in diameter. Solid particles smaller than 100 μm in diameter are not easily separated by conventional types of hydrodynamic separator, and remain in suspension in overflow. To overcome this problem, a HDFS (hydrodynamic filter separator) has been developed for treatment of the microparticles in urban storm runoff. We conducted a laboratory scale study on treatable potential of microparticles using HDFS that combined HDS with perlite filter. To determine the efficiency for various operation conditions, a series of experiments was performed with different solids concentrations and surface loading rate. The operation ranges of surface loading rates were 100 to 2,800 m3/m2/day, and influent solids concentrations were varied from 800 to 1,900 mg/L. Also, the particle size distribution was monitored to investigate the effects of surface loading rates on the particle size. Results indicated that the HDFS-Inside type showed greater efficiency at solids separation than the other type.

Electrocatalytic hydrogenation of octyl aldehyde over Pd catalysts

2007 ◽  
Vol 85 (7-8) ◽  
pp. 475-478
Author(s):  
Ciprian M Cirtiu ◽  
Hugues Ménard
Keyword(s):  
Aqueous Ethanol ◽  
Supporting Electrolyte ◽  
Catalyst Support ◽  
Current Intensity ◽  
Electrocatalytic Hydrogenation ◽  
Alumina Catalyst ◽  
Pd Catalysts ◽  
Alumina Catalysts

The electrocatalytic hydrogenation (ECH) of octyl aldehyde (octanal) to octyl alcohol (octan-1-ol) was investigated using commercial Pd/alumina catalysts in aqueous ethanol. The influence of different parameters, such as catalyst support, current intensity, polarity of solvent, supporting electrolyte, and octanal concentration, on the electrocatalytic hydrogenation of octanal was studied.Key words: octanal, octan-1-ol, Pd/alumina catalyst, electrocatalytic hydrogenation.

TEM/STEM characterization of industrial type supported Pd catalysts: Effect of an in situ hydrogen activation

1988 ◽  
Vol 46 ◽  
pp. 700-701
Author(s):  
R. Szymanski ◽  
J. Lynch
Keyword(s):  
Particle Size ◽  
Particle Shape ◽  
Local Information ◽  
Ex Situ ◽  
Supported Metal Catalysts ◽  
Metal Dispersion ◽  
Pd Catalysts ◽  
Supported Pd Catalysts ◽  
Induced Changes

TEM is routinely used to control the metallic dispersion of industrial supported metal catalysts, since in complement to the chemisorptive methods it provides unique local information about particle size distribution, i.e. about the quality of the metal dispersion. An evaluation by TEM of the mean particle size can be useful to quantify the metal dispersion assuming a simple model for the particle shape, e.g. spherical or cubic. However, except for the cases where chemisorption fails (e.g. poisonning), this evaluation is mainly considered as a mean of checking the representativity of the statistical distribution of local information in comparison with chemisorption results. Discrepancies are often observed between the two techniques and many reasons can be advanced for these such as statistics, particle shape models, electron beam induced changes, chemisorption assumptions (cf coverage), etc... In fact, we consider that in a number of cases one of the primary limitations is likely to be due to the in situ problem in TEM, which is inherent to most techniques involving an ex situ characterization.

Treatment of Waste Seawater from Shrimp Farm Using a Photocatalytic Membrane Reactor

2013 ◽  
Vol 409-410 ◽  
pp. 199-203 ◽  
Author(s):  
Zai Feng Shi ◽  
Su Min Zhang ◽  
Su Guo
Keyword(s):  
Waste Water ◽  
Particle Size ◽  
Membrane Reactor ◽  
Membrane Filtration ◽  
Ceramic Membrane ◽  
Permeation Flux ◽  
Waste Water Sample ◽  
Operation Conditions ◽  
Shrimp Farms ◽  
Photocatalytic Membrane Reactor

To treat the waste seawater from shrimp farms, TiO2 powder photocatalysis and ceramic membrane filtration technologies were integrated to form a photocatalytic membrane reactor (PMR). PMR performance was investigated and real waste water sample was treated under the optimum operation conditions. Results indicated that TiO2 powder with mean particle size of 0.27 μm could be separated successfully with α-Al2O3 membrane with pore size of 0.05 μm, the permeation flux was 432 Lhr-1m-2 under pressure of 0.05 MPa. Wastewater was treated with three different catalysts involving 2 g of TiO2 powder, 2 g of TiO2 powder combined with 5 ml of H2O2 (30%), and 2 g of TiO2 powder combined with 5 ml of Fenton agent for per liter of wastewater, the corresponding CODCr removal rates were 15.67 %, 25.19 % and 40.67 % separately.

A Single Turnover (STO) Characterization of Supported Palladium Catalysts

1987 ◽  
Vol 111 ◽  
Author(s):  
Robert L. Augustine ◽  
David R. Baum
Keyword(s):  
Palladium Catalysts ◽  
Active Sites ◽  
Pt Catalyst ◽  
Catalyst Characterization ◽  
Pt Catalysts ◽  
Ambient Conditions ◽  
Reaction Conditions ◽  
Pd Catalysts ◽  
Supported Pt Catalysts

AbstractWhile the STO catalyst characterization procedure has been applied to a variety of supported Pt catalysts, application of this technique to the characterization of supported Pd catalysts showed that there were several significant differences between the Pt and the Pd catalysts. Under STO reaction conditions each surface site on a Pt catalyst reacts only once so there is a 1:1 relationship between the product composition and the densities of the various types of active sites present. With Pd catalysts under these same conditions, alkene isomerization takes place so readily that the amount of isomerized product formed depends on the contact time of the reactant pulse with the catalyst so there is no direct relationship between the amount of isomerization and the number of isomerization sites present. On Pt there are some direct saturation sites present on which H2 is rather weakly held. Such sites are not present on Pd catalysts. The reactive surface of supported Pt catalysts remains constant on long exposure to air. With Pd catalysts exposure to air results in a decrease in saturation site densities which can be reversed by re-reduction of the surface with H2 under ambient conditions but not completely under what can be termed “reaction conditions” where the extent of surface re-reduction decreases with catalyst age.

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