Platinum-alumina Catalysts Research Articles

Catalytic oxidation of hydrogen—intrapellet heat and mass transfer

AbstractRates of oxidation of hydrogen were measured by using platinum–alumina catalyst particles and 1.86‐cm. pellets. For high‐reaction rates, temperature differences between center and surface of the pellets were more than 300°C. Under these conditions large variations in temperature with position on the pellet surface were observed. The pellet reactor was of the recirculation, stirred‐tank type with injection nozzles. Local heat transfer coefficients between pellet and gas varied twofold with location on the surface. The data showed that intrapellet heat and mass transfer resistances were both important, while between pellet and gas only the heat transfer resistance was significant.The effective thermal conductivity of the pellet was measured independently. By using this and the experimental temperature measurements, a new method s devised to establish the effective diffusivity under reaction conditions.Effectiveness factors were predicted from ke and De and the rate data for the particles. The results were about 7% greater than the experimental effectivenes lactor.

Dehydrogenation of Methylcyclohexane over a Platinum-Alumina Catalyst in Absence of Added Hydrogen

Dehydrogenation of Methylcyclohexane over a Platinum-Alumina Catalyst in Absence of Added Hydrogen

Reaction gas chromatography : II. Dehydrogenation of monoterpene compounds on platinum—alumina catalyst

Dehydrogenation of forty-two monoterpenes was investigated via “reaction gas chromatograpy” employing a reactor packed with 5% platinum on alumina. Products obtained were analysed and experimental data correlated to the structures of the parent compounds. The technique should prove of value in the identification and structure elucidation of terpenoids. Mechanisms of deydrogenations and isomerisations involved have also been discussed.

The mechanisms of hydrogenolysis and isomerization of hydrocarbons on metals: I. Hydrogenolysis of cyclic hydrocarbons

The hydrogenolysis of methylcyclobutane and various substituted cyclobutanes and cyclopentanes has been studied on metal films and on the corresponding metal-on-alumina catalysts. The product distribution on metal films depends on the metal, the reaction temperature, and the hydrogen pressure; on supported catalysts, it depends on the concentration of the metal on the carrier. At high temperature, on platinum and palladium films and on the supported catalysts with low metal content, a typical distribution is obtained with any hydrocarbons, corresponding to an equal chance to break the different cyclic bonds of the molecules. π-Allylic triadsorbed species are thought to be responsible for this type of hydrogenolysis. On 10% platinum on alumina or platinum film, at low temperature, and on nickel, only the disecondary CH 2CH 2 cyclic bonds of cyclobutanes and cyclopentanes are broken. α,α,β,β-Tetraadsorbed species could be associated with this selective hydrogenolysis. The analysis of the product distributions obtained from methylcyclopentane on platinum-alumina catalysts and the hydrogen pressure dependency of the hydrogenolysis of methylcyclobutane on platinum films suggest that another mechanism takes place on this metal. The similarity of the product distributions on films and supported catalysts shows that the carrier does not play a catalytic role in the reaction. The difference of the product distributions in the hydrogenolysis of cis- and trans-dimethylcyclopropanes is also discussed.

Isomerization of n‐pentane over platinum alumina catalysts of different activity

AIChE JournalVolume 10, Issue 6 p. 907-912 Article Isomerization of n-pentane over platinum alumina catalysts of different activity W. N. Lyster, W. N. Lyster University of Houston, Houston, TexasSearch for more papers by this authorJ. L. Hobbs, J. L. Hobbs University of Houston, Houston, TexasSearch for more papers by this authorH. W. Prengle Jr., H. W. Prengle Jr. University of Houston, Houston, TexasSearch for more papers by this author W. N. Lyster, W. N. Lyster University of Houston, Houston, TexasSearch for more papers by this authorJ. L. Hobbs, J. L. Hobbs University of Houston, Houston, TexasSearch for more papers by this authorH. W. Prengle Jr., H. W. Prengle Jr. University of Houston, Houston, TexasSearch for more papers by this author First published: November 1964 https://doi.org/10.1002/aic.690100625Citations: 3AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume10, Issue6November 1964Pages 907-912 RelatedInformation

Reactions of some C 9 aromatics on platinum-alumina catalysts

The reactions of n-propylbenzene, ω-methylstyrene, and o-ethyltoluene on 0.5% platinum-γ-alumina catalyst were studied in the presence of excess hydrogen using a microreactor pulse technique. Detailed analyses of products were made at five temperatures in the range 337 ° to 490 °C. The reactions of indane were also investigated at 337 °, 392 °, and 434 °C. Hydrogenation and dehydrogenation were so rapid that equilibrium was attained between olefins and corresponding paraffins at all temperatures. Dehydrocyelization of the substituted benzenes occurred readily to give indane, and subsequent hydrogenolysis of the C 5 ring yielded the isomeric alkylbenzene. These reactions did not attain equilibrium. Hydrocracking was a relatively minor reaction in comparison with dehydrocyclization and subsequent hydrogenolysis. Toluene was usually the main component of the C 6C 8 aromatics. Substantial hydrocarbon losses were observed on fresh catalyst and on used catalyst at elevated temperatures. Changes in catalyst composition, degree of sintering, and poisoning with thiophene showed that dehydrocyclization, hydrogenolysis, and hydrocarbon losses were dependent on the state of the supported metal although equilibrium between paraffins and olefins was still attained. Small amounts of thiophene were found to increase the selectivity of the catalyst for hydrogenolysis. The mechanisms of these reactions are discussed and the suggestion advanced that multiple π-bonded intermediates play an important part in dehydrocyclization, condensation, and coke formation. Metallic sites which are highly active in this respect are selectively repressed by coke formation, thermal sintering, and chemisorption of thiophene.

Determination of Metallic Platinum-Alumina Catalysts by X-Ray Diffraction.

Determination of Metallic Platinum-Alumina Catalysts by X-Ray Diffraction.

Particle to Particle Migration of Hydrogen Atoms on Platinum—Alumina Catalysts from Particle to Neighboring Particles

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTParticle to Particle Migration of Hydrogen Atoms on Platinum—Alumina Catalysts from Particle to Neighboring ParticlesS. KhoobiarCite this: J. Phys. Chem. 1964, 68, 2, 411–412Publication Date (Print):February 1, 1964Publication History Published online1 May 2002Published inissue 1 February 1964https://doi.org/10.1021/j100784a503RIGHTS & PERMISSIONSArticle Views1482Altmetric-Citations276LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (233 KB) Get e-Alerts

Influence of steam on the activity of alumina-platinum catalysts with different contents of the metal

The effects of the activation of alumina-platinum catalysts on hydrothermal treatment and of their deactivation on treatment with pure hydrogen diminish as the content of platinum in the catalysts increases.

Promotion of an alumina-platinum catalyst with water

1. An investigation was made of the change in the activity of a 0.005% Pt-Al2O3 catalyst after it had been treated with water vapor mixed with hydrogen at 420° with a water vapor pressure of 60–80 atm and also after the catalyst was treated with hydrogen, freed from oxygen and water, at 500°. It was established that water promotes the alumina-platinum catalyst not only in benzene hydrogenation, but also in cyclohexane dehydrogenation. The promoting effect of water is reversible. 2. Dehydration of the alumina-platinum catalyst by treatment at 550° with hydrogen freed from oxygen and water produced practically complete deactivation of the catalyst in benzene hydrogenation and cyclohexane dehydrogenation.

Water promotion of an alumina platinum catalyst

1. A study has been made of the effect which removing the oxygen and water from electrolytic hydrogen has on the activity of an alumina platinum catalyst (0.005% Pt) when used to dehydrogenate benzene in a flow apparatus at 300° and 80 atm. Treating the catalyst with purified hydrogen at 420° produced an approximately 50% reduction in activity. It has been established that the changes in catalyst activity are reversible. 2. A study has been made of the effect of treating the catalyst with a mixture of water vapor and hydrogen at 420° with a pressure of water vapor of 55–60 atm. The result of this treatment was that the activity of the catalyst increased 1.5–2 times, although the surface was reduced by 80%. 3. A discussion is given of the possible reasons why the effect of water on the hydrogenating activity of an alumina platinum catalyst is opposite to that found with a tungsten sulfide catalyst.

Valence State of Platinum–Alumina Catalysts

PLATINUM-ON-ALUMINA reforming catalysts are widely used in the petroleum industry. Recent work in this laboratory has shown that catalysts containing soluble platinum more readily convert paraffins to aromatics1. Soluble platinum is that which will dissolve in either dilute hydrofluoric acid or acetylacetone. It is believed to exist as a compound involving the alumina support and the chloride present in the catalyst, and is in the plus-four valence state after solution in dilute hydrofluoric acid.

High Temperature Changes in Alumina Structure and Activity of Platinum-Alumina Catalysts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHigh Temperature Changes in Alumina Structure and Activity of Platinum-Alumina CatalystsR. F. Waters, J. B. Peri, G. S. John, and H. S. SeeligCite this: Ind. Eng. Chem. 1960, 52, 5, 415–416Publication Date (Print):May 1, 1960Publication History Published online1 May 2002Published inissue 1 May 1960https://doi.org/10.1021/ie50605a032RIGHTS & PERMISSIONSArticle Views436Altmetric-Citations12LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (278 KB) Get e-Alerts

How to Make a More Effective Platinum-Alumina Catalyst

How to Make a More Effective Platinum-Alumina Catalyst

A New Alumina Trihydrate

DURING the development of a platinum-alumina catalyst, X-ray studies have revealed that, in addition to the well-known gibbsite and bayerite, a third crystalline form of Al(OH)3 exists. Pure samples of this new trihydrate have not been obtained. It is generally accompanied by bayerite, often by both bayerite and gibbsite. In samples where this new crystalline trihydrate is the major component, it has been possible to determine its chemical composition as Al(OH)3 and to resolve its X-ray diffraction pattern. This pattern of the new phase (as recorded with a Geiger counter spectrometer using copper Kα radiation) is:

Catalytic reactions of five- and six-membered cycloalkanes under a pressure of hydrogen at high temperature

1. It has been found that cyclopentane, under a high pressure of hydrogen (20 atm), in presence of a platinum-alumina catalyst, and at 460°, undergoes far-reaching changes with formation not only of hydrogenolysis products (pentane, and isopentane formed by its isomerization), but also hydrogenosynthesis (methyl-cyclopentane, hexane and its isomers, benzene, toluene, xylene, polymethylbenzenes). 2. Under similar conditions (hydrogen pressure, 15 atm), methylcyclopentane is converted into a mixture of cyclopentane, pentane, 2-methylbutane, hexane and its isomers, benzene, toluene, xylene, and polymethylbenzenes. 3. In contact with the same catalyst at 460° under a pressure of hydrogen (15 atm), cyclohexane gives a mixture of benzene, methylcyclopentane, cyclopentane, hexanes, pentanes, toluene, xylenes, and polymethylbenzenes. 4. The synthesis reactions are in all cases to be explained by the alkylation of hydrocarbon molecules (cyclopentane, benzene, toluene) by means of methylene radicals arising under the given conditions as a result of the methane breakdown of cycloalkanes at the surface of the specific platinum-alumina catalyst.