Control of Indoor Biogenic Volatile Organic Compounds with the Honeycomb Monolith Supported Photocatalyst
Date Issued
2012
Date
2012
Author(s)
Hung, An-Jie
Abstract
Photocatalytic oxidation (PCO) was used to control α-pinene in indoor environment in this research. Effecient use the space for the photocatalystreaction with indoor VOCs is important. The objective of coating the photocatalyst on honeycomb support is to make the best of space by addition the area of reaction. The honeycomb support needs to be operated with optical fiber for UV light. In the experiment, Degussa P25 TiO2 was chosen as catalyst. The UV lamp is 254nm and 8W. The key factors including α-pinene concentration, relative humidity, gas flow rate and the experiment conducted twice for average.
In the experiment, the effect of gas-phase transfer could be negligible when gas flow rate exceeded 1500ml/min.
Therefore the rate-determaining step was related with the surface reaction of catalyst for photocatalysis. The gas flow rate is fixed at 1500ml/min to conduct the following experiment. The inlet concentration was from 400ppb to 2400ppb, the conversion of photocatalyst was maintained between 90% to 95% regardless of the relative humidity which is from 30% to 70%. PCO rate is increased with the inlet concentration. PCO rate at the relative humidity 50% is more than it at the relative humidity 30% and 70%. Therefore, the moderate relative humidity (50%) is helpful to PCO rate, others were not. At the relative humidity 70%, the conversion of photocatalyst and the residual intermediate were decrease with the inlet concentration. To fit the reaction rate of photocatalyst, it is to use the Langmuir-Hinshelwood model for bimolecular competitive adsorption form. The Langmuir adsorption constants of α-pinene and water at relative humidity 30% is 0.168 and 1×10-2 ppm-1. And the reaction rate constants of α-pinene at relative humidity 30% is 0.82 μmole/m2-s; The Langmuir adsorption constants of α-pinene and water at relative humidity 50% is 0.56 and 5.4×10-3 ppm-1. And the reaction rate constants of α-pinene at relative humidity 50% is 0.24 μmole/m2-s; The Langmuir adsorption constants of α-pinene and water at relative humidity 70% is 1.74 and 9.6×10-3 ppm-1. And the reaction rate constants of α-pinene at relative humidity 70% is 0.18 μmole/m2-s.
Relative humidity may affect the production of hydroxyl radicals and the competitive adsorption in photocatalytic reaction. Results indicated that the increase of relative humidity could decrease the intermediates by about 8%. However, the increase of relative humidity had slightly effect on the conversion of photocatalyst. Consequently, relative humidity had an enhancement effect on production of the hydroxyl radicals in the experiment.
Subjects
photocatalyst
optical fiber
biogenic volatile organic compounds
honeycomb monolith
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-101-R99541121-1.pdf
Size
23.54 KB
Format
Adobe PDF
Checksum
(MD5):412bd350e6bb45c758b9c54a0f15ddde