Stereoselective Catalytic Isomerization of n-Butenes

Foster, NR; Cvetanović, R. J.

doi:10.1021/ja01501a039

Cited by 77 publications

(9 citation statements)

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“…Ameilonliya and Cvetanovid (2) found a similar stereoselectivity for unpromoted chromia-alumina between 210 to 260 "C. A difference in catalyst prevents a quantitative conlparison of selectivity. Foster and Cvetanovid (6) report that cis is favored over trans for isomerization of 1-butene, and that 1-butene is favored over cis-trans for 2-butene isomerization on uilsupported chromia at 250 "C. Chromia on alumina and unsupported chromia exhibit a selectivity in between those found by Foster and Cvetanovid to characterize acidic and basic catalysts. Their stereoselectivity is similar to that found for activated carbon.…”

Section: Modelling and Interpretatiorz Of Resultsmentioning

confidence: 86%

“…Higher te~nperatures also reduce stereoselectivity. Selectivity observations have led to the view that isomerization proceeds via a carbanioil radical on alkaline catalysts, whereby the stereoselectivity is due to lack of rotation of the allylic carbanion (6,8,10). A carbonium ion mechanism has been proposed for the acidic catalysts by Lucchesi et al (7) and is given support by other investigators (9-11).…”

mentioning

confidence: 95%

“…Catalytic isomerization of butenes exhibits a high degree of stereoselectivity mhich is dependent upon the catalyst (2)(3)(4)(5)(6)(7)(8)(9), temperature, and conversiois (6,11). Foster and CvetanoviC (6) show that alkaline catalysts favor double bond migration, whereas typically acidic catalysts favor cistrans isomerization.…”

mentioning

confidence: 99%

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Isomerization of butene over a chromia–alumina catalyst

Chen¹,

Hudgins²,

Silveston³

1969

Can. J. Chem.

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Psomerization runs were performed in a micro-reactor at 325 "C over a range of butene partial pressure of 84 t o 763 mm Hg and at a total pressure of approximately 1 atm. The isomerization rate of I-butene passed thro~igh a maximum ~i t h increasing I-butene partial pressure; the isornerization rate of cis-and trans-2-butcne increased asymptotically with increasing cis-and trans-2-butene partial pressures respectively. Stcreoselecti\ity was obserbed in the isomerization of each butene, and mas found to be independent of pressure. Catalyst deactivation resulted in loss in stereoselectivity. Results suggest that surface reactions control isornerization and proceed simultaneously on different active sites.Canadian Journal of Chemistry, 47, 323 (1969) Despite thecoinniercialimportance ofchromia-I11 particular, Hall and co-m orkers using isotope alumina catalyses for dehydrogenation-isomeri-and tracer techniques (9) provide considerable zation reactions, our understanding of the re-evidence for a carbonium ion intermediate on action mechailism on the catalyst and the trans-silica-alumina. Their studies (9) on activated port-kinetic rate-controlli~lg steps is incomplete. ;I-alumina lead them to suggest that more than This paper filrnishes new kinetic data on the one mecliai~ism is operative. Brouuer (5) attribisomerizatioil of buteiles over a commercial utes olefill isonierization on y-alumina to a carchromia-alumina catalvst taken with the illtent boniurn ion mechanism for cis-traus isomerizaof establishing rate-controlling steps and helping to elucidate the catalytic mecl~anism. This study extends earlier work (1) on butane dehydrogenation using the same catalyst, and suppleilieilts

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Section: Modelling and Interpretatiorz Of Resultsmentioning

confidence: 86%

mentioning

confidence: 95%

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Isomerization of butene over a chromia–alumina catalyst

Chen¹,

Hudgins²,

Silveston³

1969

Can. J. Chem.

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“…Foster and CvetalloviC (6,20) had similarly considered dual fullction of the catalyst surface in the isonlerization of n-butenes, with cis-trans isonlerizatioll involving predolni~lantly the carbollium ion or the "associative" radical mechanism, and double-bond migration predominantly the carbanion, the "dissociative" radical, or the hydrogen switch mechanism, depending on the type of catalyst. All these processes could involve a slow interaction of a physically adsorbed olefin molecule with the active sites of the catalyst.…”

Section: N I T I a L P R E S S U R E O F R E A C T A N T (Rnrn )mentioning

confidence: 99%

“…I t is well known that the presence of hydrogen is necessary for the olefin isomerization on some ~netallic catalysts (1-G), while the reaction occurs in the absence of hydrogen on metal oxide, alkali, and acid catalysts (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). Several kinetic studies have been carried out on inetallic catalysts and the mechanism of olefill isomerization has been discussed in conjunction with the mechanism of hydrogenation (2-3).…”

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confidence: 99%

KINETIC STUDY OF THE ISOMERIZATION OF n-BUTENES ON CHROMIA–ALUMINA

Amenomiya¹,

Cvetanović²

1962

Can. J. Chem.

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hZIutnal i~lterconversions of the three ti-butenes on a chromia-alumina catalyst have bccn st~~diccl in a t e m p c r a t~~r e range between 210 and 2G0° C and in a pressure rangc from about 10 to about 100 mnl. Depenclence of initial rates on the initial pressures of the reactants was clctermi~~ed expcrimei~tallp. The initial rates of isolnerization could be, in each case, expressed ernpiricall); b?. a rate ecluation conforming to the Langmuir-I-linsl~el\\~ood form~rla. It was possible to explain thc experimental results by assunling the existence of three din'erent aclsorbecl species for the thrcc 71-butene iso~~lers and their surface intercor~versions as the rate-cleterrninir~g step.Catalytic isomerization of butenes has been extensively investigated in attempts to contribute to the understanding of the mechanism of the catalytic isomerization of olefins. I t is well known that the presence of hydrogen is necessary for the olefin isomerization on some ~netallic catalysts (1-G), while the reaction occurs in the absence of hydrogen on metal oxide, alkali, and acid catalysts (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). Several kinetic studies have been carried out on inetallic catalysts and the mechanism of olefill isomerization has been discussed in conjunction with the mechanism of hydrogenation (2-3). On the other hand, relatively few kinetic studies of olefin iso~nerizations on oxide catalysts are avaiIable (12,13,18,21).Carbonium ions and carbanions have been postulated by many investigators as intermediates in the catalytic reactions of olefins ancl have been also recently invoked to explain the stereoselectivity in the catalytic isomerization of butenes (6, 15). I t is felt, ]lowever, that further lcinetic studies of these reactions, on catalytic materials of various types, are necessary, and the present work has, therefore, been carried out with the object of obtaining kinetic information on butene isomerization on a chromia-alumina catalyst. This catalyst is used commercially as a dehydl-o-isomerization catalyst. CatalystChrornia-alumina catalyst was prepared by mixing and grinding a l u m i n~~m hydroxide and chrorni~~m hydroxide, both of which were spearately precipitated by adding ammonium hydroxide to the solutions of the respective nitrates. The composition of the cataIyst was about 20% Cr?Os and 80% A1?03 by weight, as calculated from the loss on ignition of the two hydroxides. The catalyst was heated a t 500' C for 1 hour, a;lcl crushecl into pieces of convenient size. The sarne catalyst sample, weighing 0.0038 g, was used in all kinetic measurements. The surface area of the catalyst, determined by the B.E.T. method with nitrogen, -was 100.5 m2/g. Research grade butenes of Phillips Petroleum Co. were used as reactants. They \\.ere twice condensed in liouid nitrocen tram follo\ved bv evacuation, and were kept in a 3-1. reservoir. The irnpuritics in 1-butene -and cis-butene were negligibly small, but tra7bs-butene contained a small amount of cis-butenc, which \\.as subtracted ...

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Isomerization

2017

Hydrocarbon Chemistry, Two Volume Set

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Stereoselective Catalytic Isomerization of n-Butenes

Cited by 77 publications

References 1 publication

Isomerization of butene over a chromia–alumina catalyst

Isomerization of butene over a chromia–alumina catalyst

KINETIC STUDY OF THE ISOMERIZATION OF n-BUTENES ON CHROMIA–ALUMINA

Isomerization

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