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John L. Falconer
Heterogeneous Catalysis Research

Photocatalytic Oxidation
Heterogeneous photocatalytic oxidation (PCO) is a method to remove low concentrations of organic contaminants from gaseous effluents by converting them to environmentally safe products. Photocatalytic oxidation has been proposed as an effective means of cleaning up waste air streams contaminated with volatile organic compounds (VOCs) because it has many advantages:

• High destruction efficiencies at room temperature
• No chemical additives, such as auxiliary fuel, are required
• High quantum yields for gas phase reactants (low-intensity UV lamps)
• Complete oxidation of organics to CO₂ and H₂O is possible
• Inexpensive catalyst (titania)
• Applicable to a large number of organics
• Effective for low concentrations of pollutants
• Works in humid conditions
• Activity of catalyst not destroyed by chlorinated organics

PCO is well suited for modular systems and is effective on a small scale. These reactions take place on a semiconductor catalyst (usually TiO₂) with near-UV light (<380 nm). Photocatalytic oxidation is a low-energy way to reduce low concentrations of pollutants in air. Photocatalytic oxidation rates increase for many molecules when Pt particles are dispersed on the TiO₂ surface. We are using transient isothermal reaction, temperature-programmed desorption, temperature-programmed oxidation, steady-state reaction, and isotope labeling to study reaction mechanism and catalyst deactivation on TiO₂ and Pt/TiO₂ catalysts.

Sample Publications

Preis, S. and J.L. Falconer, "Gas-Phase Photocatalytic Oxidation of Motor Fuel Oxygenated Additives", J. Water Science Technol. 49, 141-145 (2004).

Blount, M.C. and Falconer, J.L., "Steady State Surface Species during Toluene Photocatalysis", Applied Catalysis B: Environmental 39, 39-50 (2002)

Blount, M.C. and Falconer, J.L., "Characterization of Adsorbed Species on TiO₂ after Photocatalytic Oxidation of Toluene", J. Catalysis 200, 21-33 (2001)

Lee, G.D., Tuan, V.A., Falconer, J.L., "Photocatalytic Oxidation and Decomposition of Acetic Acid on Titanium Silicalite", Environ. Sci. Technol. 35, 1252-1258 (2001)

Transparent Thin-Film TiO₂ Photocatalysts with High-Activity", Environmental Sci. Technol. 35, 2988-2994 (2001).

Muggli, D.S. and Falconer, J.L., "Role of Lattice Oxygen in Photocatalytic Oxidation on TiO₂". J. Catalysis 191, 318-325 (2000).

Muggli, D.S. and Falconer, J.L., "Role of Lattice Oxygen in Photocatalytic Oxidation on TiO₂". J. Catalysis 191, 318-325 (2000).

Muggli, D.S. and Falconer, J.L., "UV-Enhanced Exchange of O₂ with H₂O Adsorbed on TiO₂", J. Catalysis 181, 155-159 (1999).

Muggli, D.S., Keyser, S.A., and Falconer, J.L., "Photocatalytic Decomposition of Acetic Acid on TiO₂", Catalysis Letters 55, 129-132 (1998).

Muggli, D.S., Lowery, K.H., Falconer, J.L., "Identification of Adsorbed Species during Steady-State Photocatalytic Oxidation of Ethanol on TiO₂", J. Catalysis 180, 111-122 (1998).

Muggli, D.S., McCue, J.T., and Falconer, J.L., "Mechanism of the Photocatalytic Oxidation of Ethanol on TiO₂", J. Catalysis 173, 470-483 (1998).

Muggli, D.S. and Falconer, J.L., "Catalyst Design to Change Selectivity of Photocatalytic Oxidation", J. Catalysis 175, 213-219 (1998).

Falconer, J.L. and Magrini-Bair, K.A. "Photocatalytic and Thermal Catalytic Oxidation of Acetaldehyde on Pt/TiO₂", J. Catalysis 179, 171-178 (1998).

Photocatalytic Decomposition
We are studying how weakly adsorbed water dramatically increases the rate of photocatalytic decomposition (PCD) of organics on a Pt/TiO₂ catalyst, but chemisorbed water does not. This rate enhancement took place at room temperature; dehydrogenation rates increased as much as an order of magnitude. This type behavior may be important for other catalytic reactions, but PCD provides an unique way to study intermediates and mechanisms because reaction can be started and stopped isothermally by turning lights on and off.

Sample Publications

Blount, M.C., Buchholz, J.A., and Falconer, J.L., "Photocatalytic Decomposition of Aliphatic Alcohols, Acids, and Esters",J. Catalysis 197, 303-314(2001).

Muggli, D.S. and Falconer, J.L., "Parallel Pathways for Photocatalytic Decomposition of Acetic Acid on TiO₂", J. Catalysis 187, 230-237 (1999).

Catalyst Characterization by Temperature-Programmed Methods
Temperature-programmed oxidation, hydrogenation, and desorption are used to study catalyst deactivation. These techniques can measure the fraction of active sites that have been blocked, identify the adsorbed species that cause deactivation, and determine the amount of carbonaceous species deposited on catalyst surfaces.

Sample Publications

Luo, S. and Falconer, J.L. "Aldol Condensation of Acetaldehyde to form High Molecular Weight Compounds on TiO₂", Catalysis Letters 57, 89-93 (1999).

Luo, S. and Falconer, J.L., "Acetone and Acetaldehyde Oligomerization on TiO₂ Surfaces", J. Catalysis 185, 393-407 (1999).