Pt/Al/sub 2/O/sub 3/. I. Percentage exposed and its effect upon the reactivity of adsorbed oxygen

Journal Article · Tue Jul 01 04:00:00 EDT 1980 · J. Catal.; (United States)

OSTI ID:6870098

Kobayashi, M; Inoue, Y; Takahashi, N; Burwell, Jr, R L; Butt, J B; Cohen, J B

A set of platinum catalysts on ..gamma..-alumina was prepared by impregnation with Pt(NH/sub 3/)/sub 2/(NO/sub 2/)/sub 2/ aq and Pt(NH/sub 3/)/sub 4/(NO/sub 3/)/sub 2/ aq. Calcination at 200 to 400/sup 0/C followed by reduction at 300 to 500/sup 0/C gave percentages exposed of platinum as measured by hydrogen chemisorption at 25/sup 0/C (D/sub h/) approx. = 100%. Direct reduction of incompletely dried material led to lower values of D/sub h/. The ratio D/sub t//D/sub h/(D/sub t/ is the percentage exposed by hydrogen-oxygen titration at 25/sup 0/C) was unity for D/sub h/ < 45%, but it fell progressively below unity at larger values of D/sub h/. At D/sub h/ > 90%, not all oxygen adsorbed at 25/sup 0/C reacted with pulses of hydrogen at 25/sup 0/C. The ratio O/Pt/sub s/ increased with increasing temperature of adsorption of oxygen and at large enough O/Pt/sub s/, reaction with hydrogen at 25/sup 0/C became incomplete for all catalysts. The value of O/Pt/sub s/ at which reaction became incomplete was structure sensitive and decreased with increasing D/sub h/, from about 1.15 for D/sub h/ = 36% to 0.5 for D/sub h/ = 94%. At smaller D/sub h/, O/Pt/sub s/ became about 2 after exposure to oxygen at 300/sup 0/C; at D/sub h/ near 100%, O/Pt was about 1.15. Properties of Pt/SiO/sub 2/ and Pt/Al/sub 2/O/sub 3/ for these reactions are compared.

• Research Organization: Northwestern Univ., Evanston, IL
• OSTI ID: 6870098
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 64:1; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical &amp; Physicochemical Properties
ADSORPTION
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL REACTIONS
ELEMENTS
HYDROGENATION
METALS
NONMETALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PLATINUM
PLATINUM METALS
SORPTION
SYNTHESIS
TRANSITION ELEMENTS