Identifier

etd-06202008-131226

Degree

Master of Science in Chemical Engineering (MSChE)

Department

Chemical Engineering

Document Type

Thesis

Abstract

Photocatalytic oxidation (PCO) using TiO2 is a potential means of remediating poor indoor air quality that is attributed to low levels of volatile organic compounds (VOC). In this work, ethanol is chosen as a simple compound representative of VOC’s. The aim of this research is to establish a baseline for the photocatalytic activity of TiO2 in ethanol PCO as well as the photonic efficiency of the photoreactor. The PCO conversion could then be enhanced by using photocatalyst having a macroporous structure. A flat plate photoreactor, UV light delivery and a flow system was designed in this work to accomplish ethanol PCO. Three kinds of photocatalysts were evaluated: 1) commercial Degussa P25 (in powder and slurry form), 2) unstructured sol-gel TiO2 and 3) macroporous TiO2 deposited on two substrates (optic fiber and glass slide). Titania from sol-gel hydrolysis was found to be a better photocatalyst than the commercial Degussa P25. Maximum PCO conversion found is 61% using an optimum TiO2 surface loading of 0.403 mg/cm2. A quantum efficiency of 2.3% was obtained for the photoreactor. Kinetic analysis of the experimental rate data gave an apparent reaction order of 0.45 and an approximate rate constant of 0.00144 (mol/cm3)0.55 (cm3/ gcat-s) for ethanol PCO. The photocatalyst samples were characterized using XRD and it was found that during sol-gel hydrolysis, only anatase crystalline phase was formed. From SEM images it was confirmed that the dipcoating method at low TiO2 weights resulted to a macroporous structure but only short range ordering is apparent. It was also found that colloidal crystals made from convective assembly have very good long range order and with clearly visible (111) symmetric plane. The available surface areas were measured from adsorption isotherms, for the unstructured sol-gel TiO2 it was found to have a surface area of 50 m2/g which is comparable to Degussa P25. The pore size distributions were generated from desorption isotherms, for the unstructured sol-gel TiO2 it was found to have an average pore size of 3.9 nm. A porosity of 0.21 and bulk density of 3.07 cm3/g was also found, indicating a much denser structure than Degussa P25 slurry. Lastly, an effort was made to attain higher PCO conversion for the macroporous TiO2 through higher TiO2 weights at ideal TiO2:PS weight ratio, using three different colloidal crystal templating methods and four variations of sol-gel infiltration techniques. However, no evidence that a macroporous structure was formed. Comparable PCO conversion values to unstructured sol-gel TiO2 were obtained. Additional work is needed to improve the methodology used in the fabrication of the macroporous structure.

Date

2008

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Gregory Griffin

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