Air pollution is becoming an important world-wide social issue as the amount of fossil fuel usage increases with the growing population. Therefore, the aim of this study is to confirm the property of specific surface area in photocatalyst TiO2, which has high VOCs removal efficiency, and look into t...
Air pollution is becoming an important world-wide social issue as the amount of fossil fuel usage increases with the growing population. Therefore, the aim of this study is to confirm the property of specific surface area in photocatalyst TiO2, which has high VOCs removal efficiency, and look into the possibilities of using TiO2 as the De-NOx catalyst of SCR – a method being spotlighted for removing nitrogen.
The sol-gel process allows convenient process control and material synthesis in the unit of single molecules, and is therefore applied widely in ceramic manufacture. In order to confirm the property of specific surface area in TiO2 – a substance with high photocatalytic performance – titanium tetra-isopopoxide (TTIP), which is a metal alkoxide, was used. The specific surface area of TiO2 was controlled with H2O and pH. For the TiO2 manufactured in different conditions, we measured the particle size, TiO2 crystal phase, thermal properties, and properties of specific surface area. As a result, it was possible to manufacture anatase-phase TiO2 by using amorphous TTIP and the results showed hydrophilic properties at contact angles equivalent to 5.2° with TiO2 owning the specific surface area of 80 m2/g.
However, the price of TTIP, which is the starting material of the sol-gel method, is high. So in order to manufacture TiO2 with equivalent photocatalytic performance, we used a more economic material called meta titanic acid (MTA) as the starting material to manufacture photocatalytic TiO2. The washing time, washing pH, and temperature of thermal processing was controlled to manufacture TiO2 with the specific surface area of 80 m2/g, manufactured with the sol-gel method. The results showed residual SO3 content of 0.42 wt.% and specific surface area of 82.1 m2/g in the TiO2 with repeated washing conducted in pH 9.
It was possible to manufacture photocatalytic TiO2 owning the specific surface area of 80 m2/g with the low priced starting material MTA using the sol-gel method. VOCs removal effects were all 92% or higher, and the contact angle was 5.5° for the TiO2 manufactured with sol-gel method and 5.2° for the TiO2 manufactured with MTA, both showing ultra-hydrophilic properties.
We studied the possibility of using photocatalytic TiO2 with the specific surface area of 80 m2/g manufactured to disintegrate VOCs as the De-NOx catalyst of SCR used in the removal of NOx. Recently, due to the lower quality of fossil fuel and wider application of De-NOx catalyst of SCR, studies are starting to be conducted in the wide temperature range of 200~500℃ or higher. According to each applied temperature range, its industrial SCR De-NOx catalyst was obtained to evaluate physical/chemical properties and to measure De-NOx efficiency, NH3 slip, and NH3 oxidation rate according to temperature. Commonly used catalysts are categorized into low, middle, and high temperature catalysts – used in temperatures 300℃ or lower, 350~400℃, and 400~450℃, respectively. The V2O5 content in catalysts determine the using temperature. In an ordinary catalytic reaction, the amount of NH3 decreases as the De-NOx efficiency increases. At temperatures higher than 400℃, the NH3 oxidative reaction induced lower De-NOx efficiency due to lower NH3, and the cause turned out to be the additional generation of NOx. This phenomenon became more severe in the order of high temperature catalysts < middle temperature catalysts < low temperature catalysts. In conclusion, the amount of V2O5 in a catalyst was the main influence factor in NH3 oxidative reactions.
Therefore, studies were conducted in order to find V2O5 conditions for controlling NH3 oxidation rate at temperatures of 400℃ or higher and to complement the issues of lower catalytic performance due to lower V2O5. With TiO2 manufactured using MTA as the carrier, catalysts were manufactured according to V2O5 content and deposition method and WO3 content. For the catalyst of 0.05 wt.% V2O5 deposited in Graphene, De-NOx efficiencies were 70.5% in 340℃, 82.1% in 500℃, and the SO2/SO3 diversion rate was 0.1%. Also, the catalyst manufactured with 12 wt.% WO3 had the denitrification efficiency of 68%. The fact that WO3 is the main influence factor in low temperature catalytic function according to the proportional results of WO3 content and acid site intensity of the catalyst was revealed.
Air pollution is becoming an important world-wide social issue as the amount of fossil fuel usage increases with the growing population. Therefore, the aim of this study is to confirm the property of specific surface area in photocatalyst TiO2, which has high VOCs removal efficiency, and look into the possibilities of using TiO2 as the De-NOx catalyst of SCR – a method being spotlighted for removing nitrogen.
The sol-gel process allows convenient process control and material synthesis in the unit of single molecules, and is therefore applied widely in ceramic manufacture. In order to confirm the property of specific surface area in TiO2 – a substance with high photocatalytic performance – titanium tetra-isopopoxide (TTIP), which is a metal alkoxide, was used. The specific surface area of TiO2 was controlled with H2O and pH. For the TiO2 manufactured in different conditions, we measured the particle size, TiO2 crystal phase, thermal properties, and properties of specific surface area. As a result, it was possible to manufacture anatase-phase TiO2 by using amorphous TTIP and the results showed hydrophilic properties at contact angles equivalent to 5.2° with TiO2 owning the specific surface area of 80 m2/g.
However, the price of TTIP, which is the starting material of the sol-gel method, is high. So in order to manufacture TiO2 with equivalent photocatalytic performance, we used a more economic material called meta titanic acid (MTA) as the starting material to manufacture photocatalytic TiO2. The washing time, washing pH, and temperature of thermal processing was controlled to manufacture TiO2 with the specific surface area of 80 m2/g, manufactured with the sol-gel method. The results showed residual SO3 content of 0.42 wt.% and specific surface area of 82.1 m2/g in the TiO2 with repeated washing conducted in pH 9.
It was possible to manufacture photocatalytic TiO2 owning the specific surface area of 80 m2/g with the low priced starting material MTA using the sol-gel method. VOCs removal effects were all 92% or higher, and the contact angle was 5.5° for the TiO2 manufactured with sol-gel method and 5.2° for the TiO2 manufactured with MTA, both showing ultra-hydrophilic properties.
We studied the possibility of using photocatalytic TiO2 with the specific surface area of 80 m2/g manufactured to disintegrate VOCs as the De-NOx catalyst of SCR used in the removal of NOx. Recently, due to the lower quality of fossil fuel and wider application of De-NOx catalyst of SCR, studies are starting to be conducted in the wide temperature range of 200~500℃ or higher. According to each applied temperature range, its industrial SCR De-NOx catalyst was obtained to evaluate physical/chemical properties and to measure De-NOx efficiency, NH3 slip, and NH3 oxidation rate according to temperature. Commonly used catalysts are categorized into low, middle, and high temperature catalysts – used in temperatures 300℃ or lower, 350~400℃, and 400~450℃, respectively. The V2O5 content in catalysts determine the using temperature. In an ordinary catalytic reaction, the amount of NH3 decreases as the De-NOx efficiency increases. At temperatures higher than 400℃, the NH3 oxidative reaction induced lower De-NOx efficiency due to lower NH3, and the cause turned out to be the additional generation of NOx. This phenomenon became more severe in the order of high temperature catalysts < middle temperature catalysts < low temperature catalysts. In conclusion, the amount of V2O5 in a catalyst was the main influence factor in NH3 oxidative reactions.
Therefore, studies were conducted in order to find V2O5 conditions for controlling NH3 oxidation rate at temperatures of 400℃ or higher and to complement the issues of lower catalytic performance due to lower V2O5. With TiO2 manufactured using MTA as the carrier, catalysts were manufactured according to V2O5 content and deposition method and WO3 content. For the catalyst of 0.05 wt.% V2O5 deposited in Graphene, De-NOx efficiencies were 70.5% in 340℃, 82.1% in 500℃, and the SO2/SO3 diversion rate was 0.1%. Also, the catalyst manufactured with 12 wt.% WO3 had the denitrification efficiency of 68%. The fact that WO3 is the main influence factor in low temperature catalytic function according to the proportional results of WO3 content and acid site intensity of the catalyst was revealed.
주제어
#탈질촉매 TiO2 광촉매 V2O5-WO3-TiO2 SCR
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