Identifier

etd-06082004-211423

Degree

Master of Science in Chemical Engineering (MSChE)

Department

Chemical Engineering

Document Type

Thesis

Abstract

Metal-doped supported rare earth oxide catalysts were examined to determine their suitability for the decarboxylative condensation of two carboxylic acids to produce ketones. The catalysts were characterized based on chemisorption tests, coke analysis using thermo-gravimetric analysis and X-ray absorption spectroscopy. Effect of catalyst particle size on rate of reaction was studied for various supported cerium oxide catalysts. Catalysts were tested for activity, selectivity, and stability using isothermal fixed bed reactors. Optimal operating conditions for the production of diisopropyl ketone and methyl nonyl ketone were determined. It was found that supported cerium oxide catalysts effectively catalyzed the condensation of isobutyric acid to diisopropyl ketone for up to 12 hours of operation at weight hourly space velocities of ~4-5. On most occasions these catalysts showed no sign of deactivation at the end of 12 hours. Reactivation with air at 540 °C was sufficient to maintain long-term activity. The optimal temperature range was 470-480 °C. Activity could by improved by using catalyst particle sizes < 1 mm. Doping (0.1 - 2.4 wt.%) a supported cerium oxide catalyst with a transition metal such as Mn or Pd deactivated the catalyst but the addition of 0.8 wt.% Co increased the molar yield to diisopropyl ketone. For methylnonyl ketone production from acetic acid and decanoic acid the optimal operating conditions using supported cerium oxide catalysts were 400-420 °C at weight hourly space velocities of ~4-6. Buildup of coke on the catalyst was observed. However, yield loss due to this coke formation was negligible, and the coke was easily removed by reactivation with air at 520 °C. Doping a supported cerium oxide catalyst with a transition metal such as Co or Pd increased both the activity and selectivity. Reaction results indicate a ketene-like surface intermediate is involved in the mechanism. The role of the transition metal dopants may be to facilitate the recombination of atomic hydrogen, produced during the formation of a ketene-like intermediate, with surface -OH groups, thereby increasing the reaction rate of ketone formation.

Date

2004

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Elizabeth J. Podlaha-Murphy

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