The Physical Nature of Supported Platinum

Adler, Stephen F.; Keavney, James J.

doi:10.1021/j100831a005

Cited by 105 publications

(16 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A review on surface area measurements by Farrauto (1974) gives details on the chemisorption method, and the article by Pulvermacher and Ruckenstein (1974) provides details on the other methods including magnetic measurements. Of these methods, gas chemisorption is perhaps the most accurate and certainly the easiest to implement, e.g., Hz on Pt (Spenadel and Boudart, 1960;Adler and Kearney, 1960) and on Ni (Taylor, Yates and Sinfelt, 1964), CO on Pd (Scholten and Montfoort, 1962), and NO on oxides of Cu, N, and Fe (Gandhi and Shelef, 1973). While the chemisorption method is a powerful tool for catalytic research, it has its limitations for the determination of active surface area.…”

Section: Introductionmentioning

confidence: 99%

Determination of catalyst surface area from desorption characteristics of physisorbed gases

Miller

Lee

1984

AIChE Journal

View full text Add to dashboard Cite

A new experimental method for the measurement of catalyst surface area of supported catalysts has been developed using selective physisorption. The desorption characteristics of a gas are studied separately on the catalyst, the support, and the supported catalyst by carrying out thermal desorption experiments in a continuous flow sorptometer. Differences in the coverage vs. temperature curves, obtained from the thermal desorption experiments, are a measure of the selectivity of the physisorbing gas, and allow calculation of the fraction of total surface area occupied by the catalyst.Two systems have been studied utilizing the thermal desorption with carbon dioxide as adsorbate: potassium carbonate/carbon black and silver/alumina. Supported catalyst surface area was determined for each system; the results were confirmed using physical mixtures of the two components (where the actual area of each component is known) and oxygen chemisorption for the silver/alumina system. The experimental technique allows for straightforward calculation of the catalyst area. D. J. MILLER and H. H. LEE Department of Chemical EngineeringUniversity of Florida Gainesville, FL 3261 1The exposed surface area of a catalyst on a support is an important parameter in the characterization of catalytic behavior, particularly in sintering and dispersion studies. Several experimental methods of determining catalyst area have been developed, including chemisorption, electron microscopy, and X-ray techniques. The difficulties involved in applying electron microscopy to actual catalysts and the sophistication of small angle X-ray scattering prevent their practical application in many cases. Chemisorption techniques have met with success in several catalyst systems, but the chemisorption techniques are limited to well-defined metal catalysts and are not in general applicable to nonmetallic catalysts. This paper presents a new method for determining catalyst area using physical adsorption. The method examines the adsorption characteristics of a gas separately on the catalyst (in powder or gauze form), the support, and the supported catalyst using a thermal desorption technique for the determination of the total exposed catalyst area as a fraction of the total catalyst and support area. This method has several advantages over other methods used in catalyst area measurements:1) The physisorption experiments are easy to carry out and the equipment needed is low cost. The physisorption experiments show good reproducibility, and sample preparation is the same as in conventional physisorption.2) The method can be applied to any catalyst system with the appropriate choice of adsorbing gas, since gases physisorb on all surfaces at low temperatures. This is in contrast to chemisorption, where the specific gas-solid interactions limit application to a few systems.3) The total catalyst area is determined directly from the experiments. Unlike chemisorption, there is no need to know the adsorption stoichiometry to determine the total area. CONCLUSIONS AND SIGNIFIC...

show abstract

Section: Introductionmentioning

confidence: 99%

Determination of catalyst surface area from desorption characteristics of physisorbed gases

Miller

Lee

1984

AIChE Journal

View full text Add to dashboard Cite

show abstract

“…Because of the nature of physisorption, the selective physisorption method should be applicable to any supported catalyst, including oxides and metal compounds catalysts, provided a suitable adsorbate is used. This ccntrasts with the chemisorption method (Spenadel andBoudart, 1960 Adler andKearney, 1960), which does not yield the catalyst surface area of some metal catalysts and the majority of metal compounds catalysts because of the specific nature of chemisorption, although it yields valuable information on the sites active to a chemisorbing gas. It should be noted in this regard that Parekh and Weller (1977) developed a method of determining catalyst surface area based on a low-temperature oxygen chemisorption for oxide catalysts.…”

Section: Conclusion and Significancementioning

confidence: 97%

Further development of selective physisorption for measuring catalyst surface area

Toor

Lee

1985

AIChE Journal

View full text Add to dashboard Cite

Platinum supported on silica is used as a model supported catalyst for the purpose of demonstrating that the selective physisorption method yields the fractional catalyst surface area of supported catalysts, including metal compounds catalysts for which the method is primarily intended. The selective physisorption results with nitrous oxide as adsorbate are compared with hydrogen chemisorption results for this purpose. Experimental and theoretical refinements of the method developed earlier in our laboratory are presented that allow rather accurate determination of the catalyst surface area. The refinements also make the method effective even when the catalyst covers a small portion of the total surface area. Because of the nature of physisorption, the method should be applicable to any supported catalyst including metal compounds catalysts, provided a suitable adsorbate is used. Adsorbates other than nitrous oxide and carbon dioxide which are suitable for selective physisorption, are suggested.

show abstract

“…It has been reported (Adler and Keavney, 1960;Weisz and Prater, 1957) that even a severe coke laydown is not sufficient to deactivate the Pt-function. It has been reported (Adler and Keavney, 1960;Weisz and Prater, 1957) that even a severe coke laydown is not sufficient to deactivate the Pt-function.…”

Section: To C5)mentioning

confidence: 99%

“…Coking and sintering cause loss of surface area resulting in decline of activity in heterogeneous catalysts. It has been reported (Adler and Keavney, 1960;Weisz and Prater, 1957) that even a severe coke laydown is not sufficient to deactivate the Pt-function. However, sintering is known to reduce Pt surface area which irreversibly decreases its activation.…”

Section: To C5)mentioning

confidence: 99%

Modelling of catalytic naphtha reformers

1989

View full text Add to dashboard Cite

A simple kinetic model has been used to simulate catalytic naphtha reformers. The model idealises naphtha to three constituents, namely, paraffins, naphthenes and aromatics, with average properties assigned to each class. Out of the many reactions the mixture can undergo, four major reactions have been considered for which the kinetic parameters have been estimated using plant production data. The reactor model is validated against two different sets of plant data. The agreement between predicted results and observations is generally good. A sensitivity analysis of operating parameters on reactor performance revealed that, while temperature affects the aromatics production significantly, the effect of pressure is negligible.Un modtle cinttique simple a Ctt utilisC pour simuler des reformeurs de naphta catalytiques. Dans ce modtle, le naphta est represent6 par trois composants, soit les paraffines, les naphtenes et les aromatiques, avec des proprittts moyennes attributes ? i chacun des groupes. Outre les nombreuses rtactions que le mtlange peut subir, quatre rtactions principales ont ttt considtrtes pour lesquelles les paramktres cinttiques ont ttt estimts en utilisant des donntes de production d'une installation. Le modkle de rtacteur est valid6 en confrontant deux stries diffdrentes de donntes de production. L'accord entre les rtsultats prtdits et les observations est gtntralement satisfaisant. Une analyse de sensibi-lit6 des effets des parametres optratoires sur la performance du rtacteur rtvkle que l'effet sur la pression est ntgligeable, alors que la temptrature exerce un effet important sur la production des aromatiques.

show abstract

The Physical Nature of Supported Platinum

Cited by 105 publications

References 3 publications

Determination of catalyst surface area from desorption characteristics of physisorbed gases

Determination of catalyst surface area from desorption characteristics of physisorbed gases

Further development of selective physisorption for measuring catalyst surface area

Modelling of catalytic naphtha reformers

Contact Info

Product

Resources

About