Properties of supported metal catalysts. Progress report, 1 April 1979-1 April 1980

Technical Report · Sat Mar 01 04:00:00 EST 1980

DOI:https://doi.org/10.2172/5648632· OSTI ID:5648632

Butt, J B; Cohen, J B

Some eleven Pd/SiO/sub 2/ catalysts have been prepared by ion exchange or impregnation, with percent exposed varying from 7.3 to 82.8. Stored catalyst is more difficult to reduce than clean catalyst with short-time exposure to oxygen. Oxidation is less complete as percent exposed decreases. Upon cooling in H/sub 2/ from 450/sup 0/C and flushing with argon, there is more H than in a catalyst exposed to H/sub 2/ at 25/sup 0/C and then flushed. The Pd particles are more elongated than the Pt catalysts we have studied, and the particles are less perfect. The activity and selectivity of the entire series were examined with the hydrogenolysis of methylcyclopropane at 0/sup 0/C. These catalysts are mildly structure sensitive. Formation of palladium hydride during pretreatment (observed with in-situ x-ray diffraction studies) reduces the activity, but this occurs primarily for the low dispersions. Purging in O/sub 2/ He or Ar for 15 to 30 min at 20/sup 0/C eliminates the hydride. The turnover frequency for i-butane formation is ten times higher for Pt/SiO/sub 2/ than for these Pd/SiO/sub 2/ catalysts, but the n-butane activity is similar for both; as a result the selectivity of Pd/SiO/sub 2/ is one sixth that for the Pt/SiO/sub 2/ catalysts. The reduction in loading with increasing temperature of H/sub 2/ reduction of Pt/SiO/sub 2/ was confirmed with additional x-ray measurements and by desorption studies. This effect is largest for the lowest % exposed and is accompanied by a decrease in particle size and a shift of the size distribution to smaller sizes.

• Research Organization: Northwestern Univ., Evanston, IL (USA)
• Sponsoring Organization: USDOE
• OSTI ID: 5648632
• Report Number(s): COO-4254-3
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKANES
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
CHEMISORPTION
CRYOGENIC FLUIDS
CYCLOALKANES
ELEMENTS
FLUIDS
HYDROCARBONS
HYDROGEN
HYDROGENATION
METALS
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PALLADIUM
PLATINUM
PLATINUM METALS
RESEARCH PROGRAMS
SEPARATION PROCESSES
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
TRANSITION ELEMENTS