Pt/SiO/sub 2/. IV. Isotopic exchange between cyclopentane and deuterium

Journal Article · Sat Jul 01 00:00:00 EDT 1978 · J. Catal.; (United States)

OSTI ID:6548838

Inoue, Y; Herrmann, J M; Schmidt, H; Burwell, Jr, R L; Butt, J B; Cohen, J B

Isotopic exchange between cyclopentane and deuterium, mostly at 81/sup 0/C, has been investigated on a set of 10 Pt/SiO/sub 2/ catalysts whose percentages exposed ranged from 6.3 to 81%. The standard pretreatment, O/sub 2/, 300/sup 0/C; H/sub 2/, 300/sup 0/C; He 450/sup 0/C with cooling in helium, leads to turnover numbers for formation of exchanged cyclopentanes, which decline by a factor of less than 2 as the percentage exposed increases from 6.3 to 63.5% and then at 81% rise to about the value for 6.3%. Selectivity to various exchanged species varies with percentage exposed and, in particular, D/sub 6//D/sub 10/ (the ratio of initial yields of d/sub 6/ and d/sub 10/) decreases substantially as the percentage exposed increases. This suggests that exchange of the hydrogen atoms on both sides of the cyclopentane ring proceeds mainly via formation of ..cap alpha..,..cap alpha..-diadsorbed cyclopentane on catalysts with a smaller percentage exposed and by rollover on catalysts with a large percentage exposed. Other pretreatment conditions such as O/sub 2/, 300/sup 0/C; H/sub 2/, 100/sup 0/C and O/sub 2/, 300/sup 0/C; H/sub 2/, 450/sup 0/C with cooling in hydrogen give larger structure sensitivites for activity and different selectivities. Catalysts deactivate rather rapidly but with little change in selectivity. Deactivation is accompanied by the formation of carbonaceous residues. C/Pt/sub s/ becomes approximately 0.5 and the activity declines 10% in about 10 min on stream. Ninety percent or more of the carbon in the residue occurs in a cyclopentane structure because 90% of the carbon is removed as cyclopentane by hydrogen at 100/sup 0/C. Repetition of the standard pretreatment regenerates the initial activity and selectivity.

• Research Organization: Northwestern Univ., Evanston, IL
• OSTI ID: 6548838
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 53:3; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400303* -- Organic Chemistry-- Isotope Exchange & Isotope Separation-- (-1987)
ALKANES
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CYCLOALKANES
DEACTIVATION
DEUTERIUM
ELEMENTS
HYDROCARBONS
HYDROGEN ISOTOPES
ISOTOPES
ISOTOPIC EXCHANGE
KINETICS
LIGHT NUCLEI
METALS
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLATINUM
PLATINUM METALS
REACTION KINETICS
REGENERATION
SILICON COMPOUNDS
SILICON OXIDES
STABLE ISOTOPES
TRANSITION ELEMENTS