Oxidative dehydrogenation dimerization of propylene over bismuth oxide: kinetic and mechanistic studies

Journal Article · Fri Jul 01 00:00:00 EDT 1983 · J. Catal.; (United States)

DOI:https://doi.org/10.1016/0021-9517(83)90129-X· OSTI ID:5105322

White, M G ^[1]; Hightower, J W

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1. Georgia Inst. of Tech., Atlanta

Classical kinetic experiments together with pulse microreactor studies involving deuterium and carbon-13-labeled isotopic tracers were used to investigate the oxidative dehydrogenation dimerization (OXDD) of propylene to 1,5-hexadiene and benzene over bismuth oxide between 748 and 898/sup 0/K. The kinetic data, which indicated that the OXDD reaction is of variable order with respect to oxygen and propylene concentrations, could be fit to rate equations based on either the Langmuir-Hinshelwood model or the Mars-van Krevelen model, although the former gave more linear Arrhenius plots. A significant kinetic isotope effect (k/sub H//k/sub D/ = 1.7 at 873/sup 0/K) shows that the rate-limiting step for the OXDD reaction involves C-H cleavage, and there is only a small amount of H/D scrambling among reactant and product molecules. Analysis of liquid products by infrared spectroscopy indicated that both 1,5-hexadiene and 1,3-cyclohexadiene are stable reaction intermediates; microreactor results involving unlabeled propylene, 1,5-hexadiene, 1,3-cyclohexadiene, and 1,4-cyclohexadiene as reactants confirmed the infrared findings. Pulse microreactor experiments with /sup 13/C-labeled propylene clearly showed that deep oxidation (complete combustion) occurs via a consecutive-parallel network involving the partially oxidized intermediates as well as the starting propylene. Changes in the particle size do not alter the overall activity, although larger particles have lower selectivities for C/sub 6/ products than do smaller particles.

• OSTI ID: 5105322
• Journal Information: J. Catal.; (United States), Vol. 82:1
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BISMUTH OXIDES
CATALYTIC EFFECTS
PROPYLENE
DEHYDROGENATION
DIMERIZATION
BENZENE
DIENES
HIGH TEMPERATURE
ISOTOPE EFFECTS
KINETICS
OXIDATION
ALKENES
AROMATICS
BISMUTH COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
HYDROCARBONS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
POLYENES
POLYMERIZATION
400301* - Organic Chemistry- Chemical & Physicochemical Properties- (-1987)