Hydrogenation of nitroxides on Pt/SiO/sub 2/

Journal Article · Wed Jun 02 04:00:00 EDT 1982 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00375a001· OSTI ID:6876650

Kawai, T; Jarjoui, M; Burwell, L Jr

The hydrogenation of the nitroxide 2,2,6,6-tetramethylpiperidinyl-N-oxy (TMPNO) in ethylcyclohexane and other solvents has been studied from 0.6 to 35/sup 0/C on Pt/Si0/sub 2/. Hydrogenations were sandwiched between hydrogenations of cyclopentene using the techniques of Hyssey et al. Results were shown to be uninfluenced by mass transfer of hydrogen between gas and liquid phases and in the catalyst pores. Significant levels of poisons in the TMPNO appeared to have been absent. Rates of hydrogenation of TMPNO to the hydroxylamine were very fast. At 20/sup 0/C, turnover frequencies per second per surface atom of Pt for the loss of unsaturated molecules were approx.130 for TMPNO and approx.13 for cyclopentene, and E/sup a/'s were 21 and 34 kJ mol/sup -1/, respectively. The rates were zero order in TMPNO and about first order in hydrogen. In competitive hydrogenations of equimolar mixtures, TMPNO hydrogenated 3 times faster than cyclopentene. It appears that both TMPNO and cyclopentene adsorb strongly enough on Pt to form an essentially saturated adsorbed layer and that the rate of hydrogenation is that of the dissociative adsorption of hydrogen at gaps in the adsorbed layer of the unsaturated molecule. The relative rates of hydrogenation of such molecules are then proportional to the product (effective area of gaps) X (sticking coefficient of hydrogen).

• OSTI ID: 6876650
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 104:11; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

08 HYDROGEN
080201* -- Hydrogen-- Chemisorption Storage
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301 -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
ADSORPTION
AMINES
AZINES
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
DATA
ELEMENTS
EXPERIMENTAL DATA
HETEROCYCLIC COMPOUNDS
HYDROGEN STORAGE
HYDROGENATION
HYDROXY COMPOUNDS
INFORMATION
MEDIUM TEMPERATURE
METALS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SOLVENTS
OXIDES
OXYGEN COMPOUNDS
PIPERIDINES
PLATINUM
PLATINUM METALS
PYRIDINES
SILICON COMPOUNDS
SILICON OXIDES
SOLVENTS
SORPTION
STORAGE
TRANSITION ELEMENTS