On the selectivity of platinum catalysts

Boudart, M.; Aldag, A.W.; Ptak, L.D.; Benson, John

doi:10.1016/0021-9517(68)90007-9

Cited by 192 publications

(16 citation statements)

References 4 publications

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“…646 and electrical self-stimulation of the brain (13,14). The seemingly ubiquitous nature of catecholamine involvement across a wide spectrum of behaviors and the remarkable adaptive capacity of catecholamines to maintain relatively normal function even in cases of severe damage (1), suggests that catecholamine systems may play a very fundamental role in mediating the interaction between the organism and its environment.…”

Section: Discussionmentioning

confidence: 99%

“…As a result, one might well expect the state of dispersion of a metal to affect its specific catalytic activity, that is, the activity per unit surface area. This dependence of specific catalytic activity on dispersion has indeed been demonstrated for certain reactions which have been designated as "structure-sensitive" reactions (8,13). Interestingly, however, there are "'structure-insensitive" reactions for which the specific activity of a metal is virtually independent of the state of dispersion (13).…”

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confidence: 87%

“…This dependence of specific catalytic activity on dispersion has indeed been demonstrated for certain reactions which have been designated as "structure-sensitive" reactions (8,13). Interestingly, however, there are "'structure-insensitive" reactions for which the specific activity of a metal is virtually independent of the state of dispersion (13). The elucidation of structure sensitivity is the objective of much current research in heterogeneous catalysis.…”

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confidence: 93%

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Heterogeneous Catalysis: Some Recent Developments

Sinfelt

1977

Science

103

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In recent years major progress has been made in the area of heterogeneous catalysis by metals. Much has been learned about the nature of metal catalysts and of catalytic phenomena on metals. Characteristic patterns of catalytic behavior among the metallic elements have been established for certain classes of reactions, and these patterns provide a first step toward a more comprehensive understanding of catalytic specificity. Studies on metal alloys and related bimetallic catalysts have revived interest in a geometric factor in surface catalysis to complement the traditional electronic factor. Closely related to this geometric factor is the discovery that selectivity, rather than activity alone, is a major factor in reactions on bimetallic catalysts. Concurrent with progress in understanding how catalysts work, advances are also being made in the development of new catalyst systems, examples of which are the bimetallic (or polymetallic) cluster catalysts. Research in this area provides an example of how advances in catalyst technology can be realized within a framework of fundamental research on catalytic phenomena (38).

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Section: Discussionmentioning

confidence: 99%

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confidence: 87%

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confidence: 93%

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Heterogeneous Catalysis: Some Recent Developments

Sinfelt

1977

Science

103

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“…This indicates that the above reactions occur on special surface sites found more frequently on large dimension metal particles. Boudart et al (1968) conclude that the neopentane isomerization and hydrogenolysis reactions occur through an intermediate which must be adsorbed on three adjacent sites on the metal particle. The sites for this adsorption occur more frequently on a catalyst with a large mean crystallite size, The identification of a structure insensitive (facile) reaction is more difficult.…”

Section: Chemisorption/titrotion Methods For M E T a L Surfacesmentioning

confidence: 95%

“…Pusateri et al (1974) suggest that the reduction of nitric oxide by ammonia in an oxygen atmosphere is a structure sensitive reaction, since the rate of reaction increases by a factor of 6 as the fraction exposed decreases by a factor of 6. Boudart et al (1968) have called the hydrogenolysis and isomerization of neopentane a structure sensitive reaction. Although there is variation in the specific activity of this reaction, the general trend is for the selectivity of isomerization to decrease on catalysts containing small average particle sizes.…”

Section: Chemisorption/titrotion Methods For M E T a L Surfacesmentioning

confidence: 99%

Progress toward the a priori determination of catalytic properties

Butt

1976

AIChE Journal

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SCOPEThe ultimate achievement in catalysis would be the ability to determine without experimentation the optimum catalyst for a given chemical reaction. Fortunately, we are assured of a certain degree of job security, for this feat is certainly not possible at present, nor does it seem likely for at least some time to come. What we can do, however, is to make use of the accumulated wisdom and experience resulting from decades of research in catalysis through development of correlations which can provide some norms for catalytic behavior.The present review considers a number of these correlations, both old and new, with concern as to the progress which has been made over the years towards the ultimate achievement. In general, the concepts of the active site and surface complexes are viewed as ingredients more or less common to all correlations. Questions which should be addressed are the nature (chemical, geometric) of the active site and its relationship to surface structure, the density of active sites, chemistry of surface reactions at active sites, and the influence of electronic factors on the nature of active sites. Many correlations have an extensive history, as will become apparent, so the review presents an interesting combination of old and new in representative, if not comprehensive, form. CONCLUSIONS AND SIGNIFICANCEThere is a wide variation in the degree of understanding of different types of catalysts. This depends on both the catalytic system and who is trying to understand it. -*-rice this review ranges all the way from quantum ..echanical calculations of chemisorption on metals to ex post facto correlations of coke deposition on silica-alumina. And one general observation can be made concerning the correlations considered here: they all work, sort of.Chemisorption/titration methods have provided a significant amount of information regarding the nature of acid oxide and supported metal surfaces. In the latter case, it is found that rather simple geometric concepts may provide quite effective means of activity correlation, particularly for very highly dispersed metals with accompanying small crystallite dimension. Electronic theories, in and out of favor over the past 30 years return with deeper insight due to recently developed capabilities in quantum chemical calculations. The relationship between strength of chemisorption and activity seems firmly established on both metals and oxides, at least for the few systems for which sufficient experimental information exists.Correlations in catalysts seem to remain an experiment first, theory second matter; however, there appears to be some progress in the understanding of relationships once thought to be strictly empirical. Examples in this review deal with the compensation effect, catalyst deactivation, and alloy catalysts.To those readers actively engaged in catalysis research, apologies are offered for the presumption implied by the title of this review. Perhaps it should be "Has There Been Progress Toward the a Priori Deteimination oE Catalytic Prope...

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