초록 ▼

연구개발결과
촉매의 개발은 조합화학(combinatorial chemistry)적 방법을 통하여 일차적으로 시작되었다. 나노입자 금속산화물 Mn_xCu_yO_z의 형태인 선도물질(lead compound)을 도출한 후 이어서 전통적 방법(conventional method)인 침전법을 이용하여 도출된 선도물질을 최적화 하였다.
생성된 촉매는 비정질의 형태를 이루고 있으며 250~400℃의 조건에서 소성된 촉매의 비표면적 값은 대부분 160~200 ㎡/g으로 천연망간광석

연구개발결과
촉매의 개발은 조합화학(combinatorial chemistry)적 방법을 통하여 일차적으로 시작되었다. 나노입자 금속산화물 Mn_xCu_yO_z의 형태인 선도물질(lead compound)을 도출한 후 이어서 전통적 방법(conventional method)인 침전법을 이용하여 도출된 선도물질을 최적화 하였다.
생성된 촉매는 비정질의 형태를 이루고 있으며 250~400℃의 조건에서 소성된 촉매의 비표면적 값은 대부분 160~200 ㎡/g으로 천연망간광석의 비표면적 값보다 매우 높은 값을 보여 주었다. 또한 수백 나노미터수준의 입자로 입도분포가 매우 균일하게 구성되어 있었다.
합성된 금속산화물촉매는 NO의 함량, 소성온도, 수분의 유무, 공간속도의 변화, 산소의 함량, 황화합물의 함량에 따른 NOx 제거율을 측정하였으며 Eco Physics 사의 CLD-60 분석기를 사용한 시스템을 만든 후 사용하였다.
촉매의 성능 평가는 Mn_xCu_yO_z 뿐만 아니라 Mn_xCu_yO_z 와 V₂O₅/TiO₂ 및 기타 전이금속을 첨가한 형태로 나누어 실시하였다
Mn_xCu_yO_z의 경우 상기의 SO₂ 투입을 배제한 모든 조건에서는 뛰어난 성능을 나타내었으나 SO₂를 투입하면 성능이 지속적으로 감소하였다. 이러한 SO₂에 대한 저항성을 극복하기 위하여 Mn_xCu_yO_z와 V₂O₅/TiO₂ 및 기타 전이금속을 첨가한 형태로 촉매를 완성 후 성능을 측정하였고 <그림 2.1.86>에 보여 주듯이 SO₂에 대한 저항성을 나타내는 실험의 결과 Co가 10%, 20%의 결과는 시간이 경과함에 따라 NOx의 제거율이 여전히 서서히 감소함을 보여주었지만 Co가 30%인 경우는 시간이 지속됨에도 NOx의 전환율이 감소하지 않고 SO₂에 대한 강한 저항성을 나타내고 있음을 알 수 있었다. 이와 같은 결과를 확인하기 위하여 외부 평가기관에 샘플을 의뢰하여 반응온도 250℃, 산소 농도 4%, NO 400ppm, NH₃ 400ppm, SO₂ 50ppm, 공간속도(SV) 6,000hr^-1의 조건에서 5시간 이상동안 92.5% 이상의 탈질제거효율이 지속되고 있음을 확인하였고, 또한 반응온도를 300℃로 올린 것 이외에는 모두 동일한 조건에서도 93.8%의 높은 제거율을 보여 줌을 확인하였다. 개발된 촉매는 성형기술을 진행하였으며 최적의 촉매성능 및 성상을 만들기 위한 조건을 정한 후 시제품 10kg 을 생산하였다.

Abstract ▼

Ⅳ. Results
1. Generation of catalyst-lead compound through the combinatorial chemistry method
In this study, the lead compound such as the formula 1 was deducted firstly through the combinatorial chemistry method, and then the deducted lead compound was optimized for catalyst development by th

Ⅳ. Results
1. Generation of catalyst-lead compound through the combinatorial chemistry method
In this study, the lead compound such as the formula 1 was deducted firstly through the combinatorial chemistry method, and then the deducted lead compound was optimized for catalyst development by the conventional method.
Mn_xCu_yOz_x (Chemical formula 1)
According to the chemical formula 1 was 0.01≤x≤3, 0≤y≤2, 2≤z≤8, and X utilized Fe, Zn, Co, Ce, Zr, Mo, Al, Ni, V and one of W or more metallic salts. Metallic salt A and B were used as basic materials for the metal oxide catalyst in the chemical formula 1. As shown in < Table 2.1.2 >, themetallic salts could include at least one metal selected from the group C~L, and one or more precipitant(s) was/were selected from α~η.
As shown in < Figure 2.1.22 > and < Figure 2.1.23 >, the quantitative solutions were injected simultaneously to the reactor arranged at regular intervals using micro multi-pipette which enables quantitative injection. The reaction was processed through the combinatorial chemistry method to synthesize several libraries at the same time according to each concentration of metallic salts A~L and precipitants α~η. The filtered materials collected after the reaction was passing the courses of washing, filtering, drying and firing, and then finally produced as a metallic oxide catalyst < Figure 2.1.25>. Here, we used A=Mn, B=Cu, C=Fe, D=Zn, E=Co, F=Ce, G=Zr, H=Mo, I=Al, J=Ni, K=V, and L=W as the metallic salts and α=NaOH, β=KOH, γ=Na₂CO₃, δ=K₂CO₃, ε=NH₄OH, ζ=CO(NH₂)₂, and η=(NH₄)₂CO₃ as the precipitants.
The compounds 1~144 were synthesized in the following method shown in < Table2.1.2~2.1.4>. That is, the metallic salts A and B (0.01~0.5 mM of concentration range) of 60℃ were distributed to the 48 well plate reactor by 0.25~0.5mL using multi-channel pipette. After adjusting pH using addictive α~η, which was stirred by a shaker for 30 mins~1hour < Figure 2.1.24>. The library of each well plate reactor was filtered through the filtering device < Figure 2.1.25>. The filtered library of each reaction well plate was moved to another same sized-well plate being up-side down, and then dried in an oven of 60℃ for 4 hours. Finally, the library of each well plate was transferred to a container which can stand the firing temperature of 250~400℃ followed by firing for 4 hours in air, then generated as the metal oxide catalyst library for removal of nitrogen oxides.
The most suitable concentration of metallic salts A~L was 0.01~0.5 mM. Manganese nitrate, manganese sulfate, manganese chloride or manganese acetate could be used as metallic salt A. And copper nitrate, copper sulfate, copper chloride or copper acetate could be used as metallic salt B. The precipitants α~η were possible to use, but precipitant α was the most ideal. Although the firing could be conducted at 300~600℃, generally it was conducted at 250~400℃.
Using such combinatorial chemistry methods, 14 compounds (compound 1, 14, 20, 30, 42, 48, 58, 69, 75, 83, 96, 101, 108 and 134) which were determined to have excellent activity were selected among the composed metal oxide catalysts.
2. Optimization of the lead compound by the traditional method
The lead compounds derived from the combinatorial chemistry method were optimized by the precipitation method of the traditional synthesis method. As shown in < Table 2.1.2>, < Table 2.1.3> and < Table 2.1.4>, the metallic salt A, B < Figure 2.1.28> and other materials were dissolved in 40~60℃ water by a reactor which was specially manufactured, followed by stirring < Figure 2.1.29>, or filtering such as an experimental filter press < Figure 2.1.30>. After filtering, it was transferred to a container for drying as < Figure2.1.29> or < Figure 2.1.30>, and a stainless steel containers as < Figure 2.1.31>, then it was dried at 100℃ for 24 hours for catalyst drying as < Figure 2.1.32>, and finally we could get a cake shown in < Figure 2.1.33>. The obtained cake was pulverized using a mortar, and fired using a furnace at 250~400℃ air with the heating rate of 10℃/min for 4 hours < Figure 2.1.34>.
To measure the NO_X removal rates in accordance with the NO content, firing temperature, presence or absence of moisture, change of space velocity, oxygen content and sulfur compound content. The system shown in < Figure 2.1.26> was composed by CLD-60 analyzer of Eco Physics Inc., and the experimental device was set up with the parts of gas injection, window, reactor section and reaction gas analysis. The gas flow supplied to the reactor were controlled by MFC (Mass Flow Controller, SM-TEK Co.) from each cylinder of NO, N₂, O₂, and NH₃. And moisture supply was achieved by injection f N₂ to the reactor through the bubbler which make N₂ to be moisturized. At this time, we maintained the inner temperature of the bubbler constantly at 60℃ using the furnace outside of the bubbler to supply certain amount. All the gas supply pipes were made by stainless steel tubes, and wrapped by the heating band to prevent the generation of salt
such as NH₄NO₃ and NH₄NO₂ induced by NO and NH₃, to avoid water condensation among the reaction gas, and to maintain the temperature constantly at 180℃. The reactor was manufactured by stainless steel (SUS 316) to be 20mm of the inner diameter and 30 mm of the height as a continuous flow-type reaction device, and used quartz wool to fix the catalyst layer. The reactor temperature was controlled by PID temperature controller using the K-type thermocouple attached to outside of the reactor. And, the temperature of catalyst layer was measured by installing a K-type thermocouple at the upper part of catalyst layer in order to check the temperature of the gas inflow part. All of the gases were analyzed after removing the moisture using a moisture trap in a chiller before entering the analyzer. At this time, the temperature of the reactor was varied in 60~300℃, and the concentrations of NO and NH₃ were controlled to be 300~500ppm. Additionally, the o xygen concentration was maintained to be 3~5%, and the space velocity was set to be 5,000~40,000hr^-1.
Before the reaction, to exclude the influence of moisture and oxidation which was absorbed to catalyst, the activity experiment was conducted by keeping at 300℃ for 1 hour in an oxygen atmosphere followed by cooling to the reaction temperature, and then increasing the temperature.
The reaction activity of catalyst was presented as NO_X conversion rate, and the experimental parameters for NO_X removal in the normal condition was shown on < Table2.1.5>.
In addition, the measurement of the specific surface area and pore size distribution was performed by the catalytic conversion of carbon resources research group of Korea Research Institute of Chemical Technology. XRD and XPS analyses for catalyst structure determination were performed by the Reliability Analysis Center of Korea Research Institute of Chemical Technology.
3. Performance evaluation of nano-composite Mn_xCu_yO_z(MCO) metal oxide denitrification catalyst
The XRD analysis result of manufactured catalyst showed the Mn_1.5Cu_1.5O₄ (PDF35-103818) peak in the EI-01-018 catalyst case, and the Mn_1.5Cu_1.5O₄ (PDF 35-114669) peak in the EI-01-009 case < Figure 2.1.36>. However, both of the catalysts have forms of amorphous shapes mostly. Generally, it is suggested that the amorphous structure can havelarger surface and higher performance than the conventional catalyst composed of Mn, Cu, and O.
As shown in < Figure 2.1.37> and < Figure 2.1.38>, the specific surface area values of the catalysts fired in the condition of 250~400℃ were 160~200 ㎡/g mostly, which revealed much higher values than the specific surface area value of the natural manganese ores.< Figure 2.1.39> is a picture of an electron microscope and < Figure 2.1.40> is a figure of the particle-size distribution of the catalyst showing that the particle-size distribution was composed of hundreds of nano-meter-particles highly uniformly. The catalyst powder colored black or dark brown as shown in < Figure 2.1.41>. Molding was performed using a compressor by dividing the presence or absence of binder < Figure 2.1.43>. The molding pellet shape and XPS data were presented in < Figure 2.1.42> and < Figure 2.1.45> respectively, and the most of the measured pressing intensity values were > 3.0 kgf/c㎡. < Figure 2.1.44>. The catalysts manufactured in this study were very small nano-level particles and the manganese catalyst which have relatively high speci fic surface area. Their activation site was already determined in nature, so our catalyst showed more excellent performance than the natural manganese ore which could not be controlled in their activation site anymore even though trying technology combination.
The NO_X removal rates were measured in the shapes of manufactured catalyst powder and molded pellets. As shown in < Figure 2.1.46> and < Figure 2.1.47>, almost catalysts manufactured in this study showed excellent NO_X removal rates at a reaction temperature of 150~300℃. Especially, the highest removal rate was observed at 210~250℃. The ideal iring temperature of the catalyst was 250~400℃ and the optimal firing temperature duration was 3-4 hours. If the process was performed under the excess firing temperature or duration too long time, the catalyst performance was relatively decreased. The excellent activity was observed at 50~130℃ of the catalyst reaction temperature, which was interpreted as a result of absorption at such temperature and ranges.
As shown in < Figure 2.1.50> ~ < Figure 2.1.52>, in order to examine the relative performance of our catalyst which showed high NO_X removal ability, the experiment was performed with the materials such as CuO, MnO₂, Mn₃O₄, MnO and MN₂O₃ , and MnO₂ showed relatively better performance while the others revealed very low No removal efficiencies.
A. Influence of space velocity
< Figure 2.1.53> ~ < Figure 2.1.56> showed the experimental results which test the denitrification property with changing the space velocity of Mn_xCu_yO_z(MCO) the metal oxide catalyst that was fired at 250℃. < Figure 2.1.47> represent the removal rate results conducted at the condition of lowering the relative space velocity from 40,000hr^-1 to 20,000hr^-1. As predicted, NO_X removal rate was relatively increased. Same as the result, the more the space velocity was decreased, the more the NO removal efficiency was increased, which attribute to the amount of MnO₂ catalyst surface participating the catalyst reaction and lattic oxygen. However, when the reaction temperature was high over 350℃, the amount of No and NO₂ caused by the ammonia (reducing agent) oxidation were increased, so the activity was reduced even in the condition of low space velocity.
B. Influence of oxygen concentration
< Figure 2.1.57> showed the catalyst activity fired in the condition of N₂, O₂/N₂ 20%, O₂/N₂ 50%, O₂/N₂ 100% with respect to Mn_xCu_yO_z(MCO) catalyst. As the result of 200~25 0℃ in the figures, the more oxygen concentration was increased, the more the activity was increased. In Particular, the catalyst fired with 100% O₂ showed a high conversion rate of at least 13% compared to that with general air at 220℃.
In order to determine the cause of the increased activity following increased oxygen concentration, the experiment for O₂ on/off was performed. As compared with air firing, the catalyst fired with N₂ was decreased exponentially with oxygen blocking < Figure 2.1.58>. So, it was found that very small amount of lattic oxygen was present. However, as the oxygen concentration was increasing, the activity was maintained by the lattic oxygen after oxygen blocking.
According to < Figure 2.1.59> representing the denitrification efficiency by the oxygen concentration, the efficiency when the oxygen content was 8% was weak comparing to the efficiency when the content was 3%, however, showed relatively a little higher efficiency.
C. Influence of the firing temperature
It is well known that the manganese oxide is a multivalent metal oxide which changes the oxidation values according to the manufacturing condition. The reaction activity and selectivity of the product is changed depending on each oxidation value. Many previous researches have been performed the experiments using the natural manganese ores, however, this study was composed of several experiments on the basis of newly generatedand manganese-based amorphous metal oxide catalyst which was differentiated from the conventional simple MnO₂ studies for manganese. < Figure 2.1.53> and < Figure 2.1.60>~< Figure 2.1.64> represent the results very well. There was a slight degradation of the performance at 200℃ of firing temperature, while the highest performance was achieved at 250℃~300℃ of temperature.
D. Influence of moisture
It is well known that the natural manganese ore catalyst has an excellent oxidation and reduction reaction (redox) property by the participation of lattic oxygen to the reaction and oxygen in the atmosphere, and the removal rate was high over 90% at below 150℃ of low temperature, so it was superior and excellent than the conventional V₂O₅/TiO₂, however, the inhibition caused by moisture of the emission gas was very severe. It is because not only that the moisture strongly absorbed on the acid site an active site of the natural manganese ores competing with ammonia, but also that the moisture affect the re-oxidation rate on the reduced active site in the course of reaction.
Since the moisture competitively absorbed to the catalyst surface of the atmosphere oxygen resulted in prevention of oxygen diffusion.
One of the main problems in the development of low-temperature denitrification catalyst is the effect of moisture contained in the exhaust gas. However, most of the chimney gas contains 2-18% moisture, which showed the effect of moisture at around 200℃, while it is well known that there was little effect of moisture over 300℃ in SCR process, substantially, the reactivity was slightly reduced by moisturing. Generally, moisture adsorbed to ammonia, then inhibit single oxidation of ammonia in a high temperature, while decreased the reactivity in a low temperature. < Figure 2.1.65> is a result of an experiment for the influence of moisture. In this study, we performed the experiment at the condition of 10% of moisture content considering that commonly the exhaust gas of a LNG power plant contained 8% of moisture.
< Figure 2.1.65> shows the result of experiments performed to evaluate the NO_X conversion rate and unreacted- NH₃ and NO₂ exhaust concentrations by each temperature when the moisture is present or absent after firing Mn_xCu_yO_z(MCO) at 250℃. If there is no moisture, the catalyst activity was excellent in a low-temperature showing over 90% of SCR activity, while in the case of moisture presence, the activity decreased largely in a low-temperature, even though a little increase was detected at around 260℃, however the the activity decreased again due to increasing amount of NO₂ over 340℃. It is suggested that the activity was decreased due to the competitive adsorption of water and ammonia in a low temperatures, and consequently, the emission of unreacted ammonia increased greatly. The activity was increased in some temperature ranges of the high-temperature part, but the increasing amount of NO₂ seemed to be caused by the increase of ammonia oxidation at over 350℃.
The Mn_xCu_yO_z(MCO) catalyst induced the high NO_X removal activity in the condition of no moisture shown as < Figure 2.1.46> and < Figure 2.1.47>, but the low performance in the condition of moisture and relatively low temperature < Figure 2.1.48>. That is, < Figure 2.1.47> exhibited the removal capacity result carried out at the relatively decreased space velocity from 40,000hr^-1 to 20,000hr^-1, and as predicted, the NO_X removal capacity was relatively higher. Unlike < Figure 2.1.46> and < Figure 2.1.47>, < Figure 2.1.48>, when passing the 6% of moisture-containing NO in the course of reaction, at first, very low NO_X removal capacity was observed followed by high removal rate in the high temperature part as the catalyst temperature was rising gradually, and became comparable with the condition of no moisture and over 220℃ in the removal capacity.
As the result, SCR activity of the Mn_xCu_yO_z(MCO) catalysts decreased greatly in a low temperature by moisture. Therefore, in order to apply Mn_xCu_yO_z(MCO) to low-temperature SCR catalyst, it is required to add a co-catalyst which can reduce the moisture effect in low temperature to enhance their activity, however, this problem could be resolved by adjusting the reaction temperature over 300℃.
E. Influence of sulfur compounds (SO₂)
SO₂ existing in the exhaust gas reacted with oxygen, became oxidized to SO₃, and generated ammonium bisulfate and ammonium sulfate, and such sulfate deposited on the catalyst surface in a low temperature region of under 300℃ and induced degradation of catalyst activity and corrosion and clogging of the lower unit. It was the reaction to combine the reactants such as NO₂, NH₃ and moisture, and resulted in generating ammonium nitrate. Ammonium nitrate is generated under 150℃, so in order to suppress this generation, the pre-heating unit where these reactants can be combined to each other should be maintained over 150℃. At the temperature under 200oC, the formation of ammonium nitrate should be considered.
The biggest problem with the SCR method is the damage caused by SO₂. At the reaction temperature under 300℃, (NH₄)2SO₄ is formed on the catalyst surface. In the case of catalyst using Al₂O₃, SO₂ reacts with the catalyst and forms Al₂(SO₄)3, when using theother metals, the metal sulfate is produced.
Until now, there is no clearly identified answer. But, the big differences are present between the ammonia reaction method which uses ammonia as a reducing agent in spite of the catalyst damage by SO₂ and the hydrocarbon reaction method which uses hydrocarbonas a reducing agent. In ammonia reaction method, the damaged catalyst is not recovered even though the SO₂ supply is stopped, while, in the hydrocarbon reaction method, the damaged catalyst is recovered to the initial activity when the SO₂ supply is stopped.
Typically, manganese oxide catalysts are known to be vulnerable to moisture and sulfur compounds (SO_X). Therefore, we have performed the endothelial toxicity experiment for the sulfur compound of the synthesized catalyst, because the aim of this study was to develop a catalyst which could overcome the weakness to moisture and sulfur compounds. < Figure 2.1.66> is a graph for performing NO_X removal in the condition of 300℃, NO 300ppm, 5% of oxygen concentration, molar ration of NH₃/NO, and 10,000hr^-1 space velocity followed byadding 10ppm of SO₂. As indicated in this figure, no endothelial toxicity was observed even though 10ppm SO₂ was injected. When increasing the SO₂ concentration to 50 ppm as shown in < Figure 2.1.67>, the endothelial toxicity seemed to be still slight. Finally, the result using 150ppm of SO₂ is represented in < Figure 2.1.68> showing a little different pattern comparing to the previous 2 graphs, in which there was a trend of endothelial toxicity to the sulfur compounds.
All the experiments were performed under the same condition except that the experiment for endothelial toxicity was proceeded at the temperature of 250℃, which showed a similar trend to the results performed at 300℃. < Figure 2.1.69> < Figure 2.1.70> and < Figure 2.1.71> shows these results.
In order to compare the results of endothelial toxicity of sulfur compounds, the catalyst of US CRI Catalyst Company used at the same conditions. There was still good resistance to endothelial toxicity although only injecting 150ppm of SO₂, and the test results was displayed in < Figure 2.1.72>.
4. Development of denitrification catalyst according to the composition ratio of nano-composite Mn_xCu_yO_z(MCO) metal oxide and V₂O₅/TiO₂
A lot of experiments were performed for the factors affecting the performance of denitrification catalyst and catalyst according to the composition ratios of nano-composite Mn_xCu_yO_z(MCO) and metal oxide V₂O₅/TiO₂, so the metal oxide catalyst of high activitywas obtained, however, it was found that the performance tended to decrease continuously as following injection of SO₂.
V₂O₅/TiO₂-based catalyst has been used as a SCR catalyst, because vanadium pentaoxide(V₂O₅), tungsten trioxide(WO₃), molybdenum trioxide(MoO₃) and TiO₂ has excellent denitrification reaction and also has high resistance to sulfur.
In general, tungsten (W) is added in V₂O₅/TiO₂ catalyst, which has a high value in that the addition of WO₃ can expand the "temperature window". This is because the TOF(turnover frequency) of V₂O₅-W/TiO₂ catalyst is higher than that of V₂O₅-W/TiO₂ theoretically. WO₃ or MoO₃ is contained a large amount of 10% or 6% respectively, and acts as the "chemical" and "structural" promotor for catalyst. In other words, they are known to extend the operating temperature range of SCR reaction, limit the oxidation of SO₂ and increase the mechanical, morphological and structural properties of the catalyst by enhancing the catalyst activity and acid point of the V₂O₅/TiO₂ group.
In this study, we intended to develop a catalyst which does not cause the reduction of NO_X removal efficiency by adding the materials such as V₂O₅/TiO₂, W and Mo to the nano-composite composition Mn_xCu_yO_z(MCO) metal oxides.
As shown in < Figure 2.1.73>, the NO_X removal temperature moved to around 250℃ more closely by adding V₂O₅/TiO₂, and relatively high removal rate was observed when the V₂O₅/TiO₂ content was 5% while the lowest removal rate was measured when the V₂O₅/TiO₂ content was 10%, which showed lower removal rates when comparing to that of Mn_xCu_yO_z(MCO) metal oxide composition itself. These results means that Mn_xCu_yO_z(MCO) metal oxide itself shows very excellent NO_X removal rates at a relatively lower temperature. And it means that V₂O₅/TiO₂ acts as a foreign substance lowering the performance of the existing Mn_xCu_yO_z(MCO) metal oxide itself rather than enhancing the NO_X removal.
In addition, the experiment for SO₂ resistance was performed on the basis of such NO_X removal performance. < Figure 2.1.74> shows that the NO_X removal rate was still decreased gradually as time passed. This represents that the resistance to SO₂ was not increased in spite of adding V₂O₅/TiO₂ to Mn_xCu_yO_z(MCO) metal oxide.
As shown in < Figure 2.1.75>, the NO_X removal temperature moved to around 250oC~300oC more closely by adding W, and relatively high removal rate was observed when the W content was 3%, while the lowest removal rate was measured when adding 1% of W. However, sometimes it was regarded as an experimental error because most of the experiments showed similar results. In addition, it showed lower removal rates when comparing to that of Mn_xCu_yO_z(MCO) metal oxide composition itself like as the previous result of V₂O₅/TiO₂. These results means that Mn_xCu_yO_z(MCO) metal oxide itself shows very excellent NO_X removal rates at a relatively lower temperature.
For the case of W content, the experiment for SO₂ resistance was processed on the basis of such NO_X removal performance. < Figure 2.1.76> shows the NO_X removal rate was still decreased gradually as time passed. This also represents that the resistance to SO₂ was not increased in spite of adding W to Mn_xCu_yO_z(MCO) metal oxide.
As shown in < Figure 2.1.77>, the NO_X removal temperature moved to around 250oC~300oC more closely by adding Molybdenum (Mo), and relatively high removal rate was observed when the Mo content was 3%, while the lowest removal rate was measured when adding 1% of Mo. However, sometimes it was regarded as an experimental errorbecause most of the experiments showed similar results. In addition, it showed lower removal rates when comparing to that of Mn_xCu_yO_z(MCO) metal oxide composition itself like as the previous result of V₂O₅/TiO₂. These results means that Mn_xCu_yO_z(MCO) metal oxide itself shows very excellent NO_X removal rates at a relatively lower temperature. For the case of Mo content, the experiment for SO₂ resistance was processed on the basis of such NO_X removal performance< Figure 2.1.78>. < Figure 2.1.78> shows the NO_X removal rate was still decreased gr adually as time passed. This also represents that the resistance to SO₂ was not increased in spite of adding Mo to Mn_xCu_yO_z(MCO) metal oxide.
< Figure 2.1.79> shows the measurement results of NO_X conversion efficiency by changing the composition ratios of V₂O₅/TiO₂, Mo and W to the metal oxide Mn_xCu_yO_z(MCO), the best performance was achieved when V₂O₅/TiO₂ was 5% and W was 3% showing similar results between them. < Figure 2.1.80> is an experiment for the resistance to SO₂, which shows the NO_X removal rate was still decreased gradually as time passed. This also represents that the resistance to SO₂ was not increased in spite of adding V₂O₅/TiO₂, Mo and W to Mn_xCu_yO_z(MCO) metal oxide.
< Figure 2.1.81> shows the measurement results of NO_X conversion efficiency by changing the composition ratios of V₂O₅/TiO₂, Fe, Zn and Co to the metal oxide Mn_xCu_yO_z(MCO), which represent the similar results for the conversion rates between them.
< Figure 2.1.82> is an experiment for the resistance to SO₂, which shows the NO_X removal rate was still decreased gradually as time passed. This also represents that the resistance to SO₂ was not increased in spite of adding V₂O₅/TiO₂, Fe and Co to Mn_xCu_yO_z(MCO) metal oxide.
< Figure 2.1.83> shows the measurement results of NO_X conversion efficiency by changing the composition ratios of V₂O₅/TiO₂, La, Zr and Ce to the metal oxide Mn_xCu_yO_z(MCO), which represent the similar results for the conversion rates between them.
< Figure 2.1.84> is an experiment for the resistance to SO₂, which shows the NO_X removal rate was still decreased gradually as time passed. This also represents that the resistance to SO₂ was not increased in spite of adding V₂O₅/TiO₂, La, Zr and Ce to Mn_xCu_yO_z(MCO) metal oxide.
< Figure 2.1.85> shows the measurement results of NO_X conversion efficiency by changing the composition ratios of V₂O₅/TiO₂, and Co to the metal oxide Mn_xCu_yO_z(MCO) by 10%, 20% abd 30% , which represent the similar results for the conversion rates between them. Although < Figure 2.1.86> the result of resistance experiment for SO₂ shows that the NO_X removal rate was still decreased gradually as time passed when the composition ratios of Co are 10% and 20%, but if the composition ratios of Co is 30%, the NO_X conversion rate is not decreased and represents the resistance to SO₂ though time passed.
In order to verify these results, the verification was conducted by submitting XI-01-098 sample which does not represent the performance degradation on SO₂ to Korea Research Institute of Standards and Science, and the result data from the verifying authority were attached here.
5. Binding system development and performance test of Nano-composite
Mn_xCu_yO_z metal oxide catalyst To use the developed powder Mn_xCu_yO_z catalyst commercially, a certain type of molding is required. So, out research team performed an experiment using various binders to mold such type of powder catalyst and confirmed that the alumina binder was most ideal.
Generally, the removal performance was superior in the powder catalyst which did not use a binder than the catalyst which used a binder by average 10~20%, because the binder was a foreign matter. In addition, the manufacturing cost of the catalyst was rising by using a binder, but the use of a binder was inevitable because it was impossible to be commercialized in powder form, so we carried out various studies for binders.
A. Forming Technology
(1) Understanding the present levels of each material's strength and Mn_xCu_yO_z metal oxide catalysts
For the commercial application of powder Mn_xCu_yO_z catalyst that was finally selected and developed, it is required to mold it into a certain form, so we adopted the pellet form and tested its strength to evaluate the consequent durability in this study.
Firstly, we secured the similar materials and performed a comparative analysis to determine the strength level of the pellet form. It was found that the activated carbon coal represented higher strength than the other materials, because usually, the activated carbon coal was molded using the materials such as the coal, coconut coal, bituminous coal and binders such as tar and pitch,
Unlike the activated carbon which removes the harmful gases through physical adsorption, the metal hydroxide absorbent removes the harmful gases through chemical reaction, and which is used at the field of slow reaction, so it is not required the intensity to be relatively high. On the other hand, since the catalyst is operated at a relatively high temperature when compared to these materials, it should be kept the constant intensity to use for a long time and minimize the loss of the catalyst due to long-term operation.
As the result of strength measurement of the local and international catalyst products, the average strength was over 3kgf/c㎡. Considering the strength and differential pressure of products on the basis of our measurement result, we determined the final form of the catalyst developed in this study to be a pellet form with 3.3±0.2mm diameter, and then the final molding was carried out using an extruder.
(2) Strength improvement experiment of Mn_xCu_yO_z metal oxide catalyst
Since the extruder form, content and structure of the binder and extrusion pressure could have a direct effect on the strength and performance of the products, and the product strength directly or indirectly influenced the product performance and the powder flying degrees caused by elimination of fine particles on the product surface, the process development for optimal extrusion conditions was established to prevent it.
To measure the intensity, a manufactured pellet was pre-treated to have under 2 values of L(length)/D(diameter) ratios, and 20 pellet samples were randomly selected. Then the maximum values (peak value) of crushing strength which appeared when compressing each pellet was calculated, subsequently, the average values were calculated among the results excluding the highest and lowest results.
Considering the mechanical factor and composition change and addition factors among the methods to improve the strength of Mn_xCu_yO_z metal oxide catalyst, the improvement experiment was performed and achieved the results as following.
As shown in < Table 2.1.9> and < Figure 2.1.87>, it was possible to improve the extrusion pressure by reducing the extrusion rate, but it was hard to expect a mass-production, so the best factor for increasing the catalyst strength is to increase the pressure of a extruder. < Table 2.1.10> and < Figure 2.1.88> showed that the strength improvement was achieved when the extrusion was subjected to 15HP (horsepower) under the same condition of being subjected to 6HP.
< Table 2.1.11> and < Figure 2.1.89> is the result of the strength performance according to binder contents and pellet diameters. The high level of binder addition affected the improvement of strength directly, however, as the content increased, so the catalyst performance decreased, and consequently, it was desirable to add up to less than 10%.
And as displayed in < Table 2.1.12> and < Figure 2.1.90>, since the larger the pellet diameter, the larger the extrusion pressure of the cross-sectional area, which also demonstrated that as the diameter increased, so the strength also increased.
B. Prototyping
The prototype (10kg) was completed by the development successes of binding system, performance tests and molding technologies.