Platinum-alumina Catalysts Research Articles

Study on the Selective Hydrogenation of Butadiene in C<sub>4</sub>-Hydrocarbon Fraction (Part 3)

Selective hydrogenation of butadiene to prepare 1-butene in a good yield has been studied over several group VIII metal catalysts in the presence of carbon monoxide. The following results were obtained.(1) In the presence of carbon monoxide, the selectivities of butadiene hydrogenation to n-butenes were kept nearly 100% until high conversion of butadiene over the various metal catalysts.(2) The selectivities of 1-butene and the trans-2-butene/cis-2-butene ratios did not change with the variation of the butadiene conversion over various metal catalysts and the selectivities of 1-butene over these catalysts were rebresented in the following order: Pt>Ir>Ph∼Ru>Pd>Ni and the order of trans-2-butene/cis-2-butene ratios were Pd>>Ir>Ni>Ru∼Ir>Pt. It was considered that 1-butene and 2-butenes were formed only by 1.2- or 1.4-addition of H2 on butadiene and the isomerization of 1-butene to 2-butenes did not proceed until butadiene disappeared.(3) Platinum-alumina catalyst showed very high 1-butene selectivity but resulted 1-butene was isomerized to 2-butenes when the butadiene conversion exceeded 90%. On the other hand, palladium-alumina catalyst showed somewhat lower 1-butene selectivity but no isomerization was observed. As a result, 1-butene could be produced in a good yield from butadiene using platinum-alumina catalyst followed by palladium-alumina catalyst in the presence of carbon monoxide in H2.

Kinetic relationships in the low-temperature isomerization of n-butane

1. The kinetics of the isomerization of n-butane over chlorine-promoted alumina-platinum catalyst have been studied. 2. The rate of isomerization is directly proportional to the partial pressure of butane and inversely proportional to that of hydrogen. The apparent activation energies of the forward and reverse reactions are 14 and 16 kcal/ mole,respectively. 3. An equation is proposed for representing the low-temperature isomerization of n-butane over an alumina-platinum catalyst. Satisfactory agreement is shown between the experimental data and the calculated data.

The mechanisms of hydrogenolysis and isomerization of hydrocarbons on metals: VII. Isomerization of labeled hexanes and hydrogenolysis of methyl ( 13C) cyclopentane on a 10% platinum-alumina catalyst

The isomerization of 2-methyl-2- 13C, 3-methyl-3- 13C, and the hydrogenolysis of methyl-( 13C) cyclopentane were studied over a 10% platinum-alumina catalyst at 270 °C, Methylcyclopentane hydrogenolysis yielded mainly 2-methylpentane and 3-methylpentane, and isomerization was mostly restricted to an interconversion between both methylpentanes. The position of the carbon 13 in the various reaction products could only be explained by assuming that several successive rearrangements take place in the adsorbed phase, before desorption. A model was devised whereby acyclic adsorbed hydrocarbons may either be desorbed, or be rearranged according to a cyclic or a bond shift mechanism. The only bond shift reactions envisaged in this model were the three possible methyl- and ethyl- shifts involving a tertiary carbon atom, and the same rate was assumed for each of these three reactions. With these assumptions, the observed initial product concentrations (ten independent values) could be reproduced with two parameters only: the probability d of desorption of the adsorbed species, and the probability t of bond shift rearrangement. The mean number of rearrangements before desorption, equal to 1 d , was two for the experiments described, so that not less than seven trips had to be envisaged to account for all of the reaction products. The differences between these results on the 10% PtAl 2O 3 catalyst and the ones obtained on a highly dispersed catalyst, where most of the isotopic varieties are explained by a single dehydrocyclizationring opening process, are interpreted in terms of metallic particle sizes. It is believed that on the dispersed catalysts, the active sites consist, of a single atom, and the only possible path for isomerization is the cyclic mechanism. On catalysts with large crystallites, such as the 10% Pt-alumina catalyst, it is believed that sites involving several metal atoms are present on the surface, which allows the occurrence of bond shift reactions and of the repetitive process.

The mechanisms of hydrogenolysis and isomerization of hydrocarbons on metals. VI. Isomerization of labeled hexanes on a 0.2% platinum-alumina catalyst

The isomerization at low conversion of six methylpentanes (2-methyl- and 3-methyl-), labeled with carbon 13 in various positions, have been studied over a 0.2% PtAl 2O 3 catalyst. The nature of the carrier, an inert alumina, and the reaction temperature, 265–275 °C, were such that the skeletal rearrangement proceeds only on the metallic part of the catalyst. The position of the labeling atom in most of the isomeric reaction products, methylpentanes and n-hexanes, is consistent with a simple cyclic mechanism of isomerization. This mechanism consists of a dehydrocyclization to a methylcyclopentane intermediate followed by the opening of its ring. However, ten to twenty percent of the isomers referred to as “abnormal” products, cannot be explained by this mechanism. The abnormal n-hexanes are formed by the succession of a dehydrocyclization-ring opening process and an exchange of the two terminal carbon atoms in the resulting adsorbed n-hexane. The abnormal methylpentanes may be formed either by a simple methyl or ethyl shift, or by the succession of several rearrangements in the adsorbed phase, according to a bond shift or a cyclic mechanism. The simultaneous occurrence of a single dehydrocyclization-ring opening process, the major mechanism, and of a minor process involving several successive rearrangements before desorption, suggests a heterogeneity of the 0.2% PtAl 2O 3 catalyst.

Hydrogenation of aromatic compounds in jet fuel fractions

1. A study has been made of the conditions for hydrogenating 130–215 and 130–240°C jet fuel fractions on commercial alumina-cobalt-molybdenum and alumina-platinum catalysts. 2. It has been shown that hydrogenation on alumina-cobalt-molybdenum catalyst gives hardly any increase in smoke point. 3. Hydrogenation on alumina-platinum catalyst leads to high degrees of conversion of aromatic hydrocarbons and hence to considerable increases in smoke point of the hydrogenated product.

Effect of rhenium additives to alumina-platinum catalysts on the conversion of n-heptane

IN ORDE~ to prepare gasoline with an octane number of 93 and more straightrun paraffin gasohnes were subjected to catalytic reforming at increased temperature and contact time. The following disadvantages normally characterize reforming of gasolines under strictly defined conditions with alumina-plat inum catalysts: low yield of reforming-gasoline (76-80%), relatively rapid coking o f the catalyst and consequently, short periods between regenerations and short general service life of catalysts. The development of stable catalysts is therefore of foremost significance for reforming plants using paraffin gasoline fractions with a high degree of aromatization. Reports on the development of "rheniforming"* [1-5] pubhshed in the literature are therefore of interest; according to these reports the addition of rhenium to an alumina-plat inum catalyst promotes more satisfactory dispersion of platinum and stabilization during operation. This appears likely since rhenium metal is highly heat resistant (m.p. 3170°). Considerable confusion is created by the report concerning the addition of rhenium to an aluminaplat inum catalyst which alters the selectivity of chemical reactions and reduces coke and gas yield. According to the authors, this is the reason why the apphcation of an alumina-plat inum-rhenium catalyst enables the process to be carried out at pressures which are reduced compared with those of ordinary reforming and with a 3 : 1 circulation of hydrogen and accordingly at approximately 50 % higher efficiency related to the raw material [5]. Results are given in this paper concerning the effect of rhenium additives on an alumina-plat inum catalyst for n-heptane conversion under impulse conditions.

Gas-phase conformational preference of the methyl group from equilibration of 1-, 3-, and 4-methyldiamantane on a chlorinated platinum–alumina catalyst

On a chlorinated platinum–alumina catalyst/hydrogen chloride co-catalyst, the isomeric methyldi-amantanes establish equilibrium, the temperature dependence of which yields a value of 2·14 kcal mol–1 for the gas-phase conformational ethalpy of the methyl group.

The chemistry of diamantane. Part I. Synthesis and some functionalisation reactions

Rearrangement of the tetrahydro-derivative of the heptacyclotetradecane Binor-S in the gas phase in hydrogen chloride over a chlorinated platinum-alumina catalyst at 150° or in solution in dichloromethane containing alumin-ium chloride gives diamantane in high yields. Methods for functionalisation of diamantane have been developed. Chlorination at 0° with alum'inium chloride–acetyl chloride yields equal amounts of 1- and 4-chlorodiamantane (the so-called zonal and apical derivatives) whereas use of chlorosulphonic acid at –5° yields mainly the 1-chloro-isomer. Hydrolysis of the chlorides yields the corresponding alcohols, which are separable by chromatography over alumina. The chlorides and alcohols can be equilibrated with aluminium chloride and with concentrated sulphuric acid, respectively. Oxidation of diamantane with 96% sulphuric acid at 75° yields diamantanone, 9-hydr-oxydiamantan-3-one, and diamantane-4,9-diol. Treatment of diamantan-3-ol with 70% sulphuric acid yields a mixture of mono-ols, 9-hydroxydiamantan-3-one, diamantane-3,9-diol, and diamantane-4,9-diol.

Dehydrocyclization of paraffins. Influence of chlorine on cyclization pathway over Pt-Al 2O 3 catalysts

Platinum-alumina catalysts are usually prepared by impregnation with chloroplatinic acid (1). McHenry et al. (b), have proposed that a fraction of the chloroplatinum complex survived the catalyst pretreatment; this complex-but not metallic platinum-was soluble in aqueous HF. They found that dehydrocyclization was catalyzed only by the soluble chloroplatinum fraction; isomerization and cracking were catalyzed by the metallic platinum. Other laboratories subsequently reported results which supported this proposal (S-5). Bursian et al. (6’) claimed that the soluble Pt-Cl-A1,03 complex was even more specific and catalyzed only cyclizations to naphthenes and that all dehydrogenation took place on the metallic platinum. In contrast, Kluksdahl and Houston (7) and Johnson and Keith (8) found that the soluble platinum was present only after the reduced catalyst was exposed to oxygen. Thus, the soluble form could not be the active dehydrocyclization catalyst but may still be the source of the Pt active for dehydrocyclization. The aromatic isomer distribution may be influenced by the various catalytic materials (9) ; hence, it could be expected that a different isomer distribution may be obtained when chlorine is present than when it has been removed. Thus, we have determined the aromatic isomer distribution for the dehydrocyclization of 3-methylheptane over catalysts with and without chlorine.

Preparation of diamondoid hydrocarbons by rearrangement employing a chlorinated platinum-alumina catalyst

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPreparation of diamondoid hydrocarbons by rearrangement employing a chlorinated platinum-alumina catalystM. A. McKervey, D. E. Johnston, and J. J. RooneyCite this: J. Am. Chem. Soc. 1971, 93, 11, 2798–2799Publication Date (Print):June 1, 1971Publication History Published online1 May 2002Published inissue 1 June 1971https://doi.org/10.1021/ja00740a044RIGHTS & PERMISSIONSArticle Views175Altmetric-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 (258 KB) Get e-Alerts Get e-Alerts

Hydrocracking with Chlorinated Platinum-Alumina Catalysts for Liquefied Petroleum Gas Production

Hydrocracking with Chlorinated Platinum-Alumina Catalysts for Liquefied Petroleum Gas Production

Dehydrogenation of Dicyclohexyl over a Platinum-Alumina Catalyst without Added Hydrogen

Dehydrogenation of Dicyclohexyl over a Platinum-Alumina Catalyst without Added Hydrogen

Production of Heavy Aromatic Hydrocarbons by Catalytic Reforming (Part 3)

Studies were carried out to investigate the composition of C6-C10 alkylbenzenes and C10-C12 alkylnaphthalenes in reformate and the yield of aromatics which were obtained by catalytic reforming of kerosene, using the commercial platinum-alumina reforming catalyst.1) Kerosene fractions having the boiling range of 210∼220°C, 220∼230°C, 230∼240°C, 240∼250°C and 250∼260°C obtained from Gach Saran crude oil were reformed.Kerosenes having boiling ranges of 210∼220°C, 230∼240°C and 250∼260°C gave higher yields (crude oil basis) of aromatics. Naphthalenes contents in reformates increased with raising of boiling point of the feed. However, compositions of C8, C9 and C10 aromatic isomers remained unchanged regardless of the boiling range of kerosene fractions.2) Gach Saran kerosene (180∼250°C) was reformed using the operating conditions as follows; the temperature 450∼530°C, the pressure 10∼50atm, the liquid hourly space velocity 0.6-8.4 and the mole ratio of hydrogen to hydrocarbon 5-15. From the data obtained, the relationship between the operating conditions and the yield, compositions of aromatics in reformates were investigated.3) Kerosenes of Gach Saran, North Sumatra, and Ekhabinskaya, having the boiling range of 180∼250°C and C10-C12 n-paraffins were reformed.The yields of reformates and the aromatics in reformates obtained from kerosenes varied with the kind of feed, but the compositions of aromatic isomers did not change with the feed.The yields of aromatics in reformates obtained from C10, C11 and C12 n-paraffins showed almost the same values, and compositions of aromatic isomers agreed with each other. Generally, C8-C10 aromatic isomers in the reformates obtained from C10-C12 n-paraffins contained more poly-methylbenzenes, and less mono-alkylbenzenes and alkylindanes than those obtained from kerosenes. From the above results, main pathway of dehydrocyclization of C10-C12 n-paraffins using the acidic platinum-alumina catalyst seems to be formed through iso-paraffin.

Hydroisomerization of Normal Paraffins over Fluorided Platinum-Alumina Catalysts

Hydroisomerization of Normal Paraffins over Fluorided Platinum-Alumina Catalysts

Effect of lntraparticle Diffusion of Hydrogen on Hydrogenation Rates of Nitrobenzene with Platinum-Alumina Catalyst Particles

ふりまぜ反応器を用い,エタノール溶媒中でアルミナ付き白金触媒によるニトロベンゼンの水素化反応速度を測定し,物質移動と触媒表面反応との関連についての基礎的検討を行なった。触媒は市販の多孔性アルミナに白金をf=0.0005～0.010g/gの範囲で担持したもので,100メッシュ程度の粒状である。水素の拡散移動を気一液境膜,液一固体外表面境膜,触媒粒内の3段階において考え,それに表面反応過程を考慮した一般理論式に基づいて検討した。触媒量あるいはfを変えて実験を行ない,実験結果はこの理論式によく一致することを確かめた。また,表面反応は触媒表面の水素濃度に関して一次であることを明らかにした。一次反応の場合の球形粒内拡散の取り扱いによりfの異なる触媒に応じて表面有効係数ηおよびThieleモジュラスの値をそれぞれ0.48～0.13および5～23と評価しえた。fの増加にともなう白金の比活性の見かけ上の減少はηの減少に起因することを明らかにした。直径が0.015cmほどの小さい触媒粒がこのようなη値をとるのは液相における粒内拡散の特徴を示すものである。スラリー法で多孔性触媒を用いた場合には粒内拡散の影響を多少にかかわらず考慮する必要があることを強調した。また,理論式に基づく実験的プロットからは,各段階における速度定数あるいは抵抗値を合理的に定めえる。それらの値はたがいに大差がないために,触媒の使用量やfが変わると,総括反応速度におよぼす各段階の寄与の大きさが変化することを明らかにした。

Rates of hydrogenation of cycloalkenes from the liquid phase on platinum-alumina catalysts

Rates of hydrogenation of cycloalkenes from the liquid phase on platinum-alumina catalysts

The surface transport of various gases on a platinum-alumina catalyst

Permeation measurements were evaluated to aid in the investigation of surface-transport rates for propane, n-butane, n-pentane, n-hexane and krypton in a platinum—alumina pill. The surface transport of the hydrocarbons follows an equation derived for the case of dissociative adsorption of the migrating gas. Surface mobility decreases with increasing chain length. Activation energies increase from propane to pentane and are somewhat larger than the corresponding heats of adsorption. Krypton follows an equation equivalent to the laws proposed by Babbitt and by Gilliland but here restricted to monoadsorbed gases. It is suggested that the derivation of the latter equation shown in this work may be preferable to that of Babbitt and Gilliland, because it points out the importance of the specific interaction between adsorbate and solid surface.

Catalytic dehydrocyclization of n-hexane over a platinum-alumina catalyst with the impulse regime

1. An investigation was made of the aromatization of n-hexane in presence of a 1% Pt/γ-Al2O3 catalyst in a stream of hydrogen at atmospheric pressure in the temperature range 380–540° with the impulse regime. 2. The maximum yield of benzene was obtained at 540° (29% in the catalyzate). 3. Over the whole temperature range investigated C5-dehydrocyclization of hexane occurs with formation of methylcyclopentane. 4. Under the conditions of the reaction methylcyclopentane undergoes hydrogenolysis and dehydrogenation with formation of 1-methylcyclopentene and methylcyclopentadiene, and also dehydroisomerization with formation of benzene.

Conversion of spiro[4,4]nonane on platinum-alumina and palladium-alumina catalysts under catalytic reforming conditions

1. The conversions of spiro[4,4]nonane at 450°, a hydrogen pressure of 30 atm, a space velocity of 0.3 h−1, and a molar ratio of hydrogen to hydrocarbon of 5∶1 in the presence of 0.5% platinum-alumina and 0.5% palladium-alumina catalysts have been investigated. 2. In the presence of the platinum-alumina catalyst, the main conversion product is o-methylethylbenzene (41% of the catalyzate). 3. In the presence of the palladium-alumina catalyst isomerization of the spiro[4,4]nonane took place with the formation of indan (68% in the catalyzate).

Catalytic conversions of spiro[4,5 ]decane on platinum-alumina, palladium-alumina, and cobalt-alumina catalysts under catalytic reforming conditions

1. The conversions of spiro[4,5]decane on 0.5% platinum-alumina, 0.5% palladium-alumina, and 10% cobalt-alumina catalysts at 450° and a hydrogen pressure of 30 atm have been investigated. 2. Under these conditions the main reaction is the isomerization of the spirane to naphthalene. This takes place most readily on the platinum catalyst. 3. Rupture of the five-membered ring of the spirodecane and all the C-C bonds also takes place with the formation of small amounts of gem-disubstituted cyclohexanes and alkylbenzenes.