An investigation of gas-phase photocatalytic oxidation of cyclohexane in air on TiO2

A seminar prepared for SEAS Undergraduate Research Forum

November 17, 2009

By Samuel T. Kurachek

Miami University Paper and Chemical Engineering Department

Advisor: Dr. Catherine Almquist

What is the phenomenon known as photocatalysis?

It denotes the acceleration of a photoreaction by the action of a catalyst

It also refers to a general label to indicate that light and a substance (Catalyst or initiator) are necessary entities to influence a reaction

Photo

Catalysis

Light; radiant

energy; of or

pertaining to light

The action of a catalyst;

the increase or decrease of the

rate of a chemical reaction

Application to Pollution Prevention

The process of photocatalytic oxidation has undergone numerous studies for its potential application to industry◦Degradation of organics in water and

in air

◦Disinfection of water

◦Self-cleaning surfaces

◦Organic synthesis

Everyday examples and Applications of photocatalysis using TiO2 Self-Cleaning Glass

Air purifiers

Water Treatment Coated Tiles

Anti-fogging glass Building Material Coating

Further Examples . Printing ink Paint Plastics Paper Synthetic

fibers Rubber Painting

colors and crayons

Ceramics Electronic

Components

Cosmetics Condensers

• Antimicrobial Coatings:Activity of TiO2 results in thin coatings of the material to which its applied to exhibit self-cleaning and disinfecting properties with exposure to UV radiation

Mechanism for Gas Phase Photocatalysis with TiO2

•RHRH2

RHOH(Alcohol or

Ketone Intermediate)

hVB

Research GoalsFocus on gas phase photo-oxidation of

cylcohexane in air on TiO2 catalyst

1) Determine the effect of cyclohexane concentration on the rate of cyclohexane degradation via photocatalysis

2) Determine the effects of TiO2 brand and particle size on the photoactivity of TiO2.

Cyclohexane (C6H12)

Experimental Apparatus

Bulk Flow of Air and Cyclohexane (vap.) into Photocatalytic Reactor

Cyclohexane (Liq.)

Air inflow from MFC

Cyclohexane Vapor Diffusing into Bulk Flow of Air

Cyclohexane Vapor Generator

TiO2 – coated glass beads

400 W xenon lamp

Ceramic cylinders to distribute air

Air

Aluminum box to contain light

Acetone-filled Impinger

Vent To Hood

Experimental Procedure

Experiment

1

•Mass Flow Controller Set Airflow rate at 100 ccpm•Varied Temp. Diffusion Cell

Experiment

2

•Mass Flow Controller Set Airflow rate at 50 ccpm•Varied Path L. Diffusion Cell

Cyclohexan

e Vapor in air

VOC

CO2+ H2

O

Photocatalytic Reactor

AcetoneTrap

Miget Impinger Bubbler

Sample Hewlett

-Packard HP 5890

GC

Calibration and Analysis

Safety First!

Tell someone (professor, graduate student, other student) that you are working in the laboratory so that someone knows what you are doing and when.

Never do experimental work without someone else in the

building.

If something does go wrong, first contact someone for help and then refer to the safety sheets located in the white binder inside the door of the lab – Chemicals/gases being used: Cyclohexane, Acetone, Hydrogen Gas, Helium Gas (Benzene was also in the lab work area used by another student)

Use safety glasses/goggles and gloves, have close-toed shoes, and use caution when working with volatile organics

Effect of inlet cyclohexane concentration

Although the inlet concentration of cyclohexane varied from 400 ppm – 650 ppm, the rate at which cyclohexane degraded was approximately 200 ppm/min or 0.035 mg/min.

Langmuir-Hinshelwood Kinetics often models photocatalytic oxidation systems well:

dC / dt = kC / (1+KC)NOTE: When KC >> 1, then dC/dt = k/KWhen KC << 1, then dC/dt = kC

Preliminary data suggests that our system was operated such that KC >> 1, and that the ratio of k / K is ~200 ppm/min. Thus, to see an effect of inlet concentration, a cyclohexane concentration of < 10 ppm would need to be fed to the reactor.

Effect of TiO2 particle size – To Be Completed

Hypothesis is that the competing effects of increasing specific surface area and decreasing light absorption as particle size decreases will result in an optimum particle size.

Specific surface area = 4 π R2/ (ρ 4/3 π R3) = 6 / (ρ D)

Light Absorption = function of D3

Effect of TiO2 particle size – Progress

Ishihara ST-01 TiO2 has a primary particle size of ~10 nm. This TiO2 was calcined at elevated temperatures to form TiO2 particles of various particle sizes.

As received 400 C 700 C~10 nm ~20 nm ~50 nm

Effect of TiO2 particle size – Previous Work There appears to be an optimum particle size of approximately 25

nm for the degradation of organics in water.

Is there also an optimum particle size in gas-phase photocatalysis?

Degussa P25

Aldrich Anatase

Ishihara ST-01

Almquist and Biswas (2002)Phenol Results

DMMP Results

Ishihara ST-01, calcinedAt various temperatures

Almquist, unpublished data

Future Work

Complete effect of TiO2 primary particle size in gas-phase photocatalytic oxidation of cyclohexane.

Prepare manuscript

Acknowledgements

This work could not have been completed without the help from Dr. Almquist, contributing her time and effort towards this project throughout the summer and this semester

Also, a special thanks to Deepika Mahendran for her help and company while working this summer

References[1] P. A. Deveau, F. Arsac, P. X. Thivel, C. Ferronato, F. Delpech, J. M. Chovelon, P. Kaluzny, C. Monnet, Journal of Hazardous Materials 144 (2007) 692-697

[2] G. Lu, H. Gao, J. Suo, S. Li, J. Chem. Soc., Chem. Commun.(1994) 2423.

[3] C. B. Almquist, P. Biswas, Applied Catalysis A: General 214 (2001) 259-271.

[4] P. Du, J. Moulijn, G. Mul. Journal of Catalysis 238 (2006) 342-352. [5] U. I. Gaya, A. H. Abdullah, Journal of Photochemistry and Photobiology C: Photochemistry Reviews 9 (2008) 1-12.

[6] P. Boarini, V. Carassiti, A. Maldotti, R. Amadelli, Langmuir 14 (1998) 2080.

[7] E. Sahle-Demessie, M. Gonzalez, Z. M. Wang, P. Biswas, Industrial & Engineering Chemistry Research (1999), 38, 3276-3284.