초록 ▼

$\circ$ 본 연구에서는 $350^{\circ}C$이하의 반응온도 영역에서 처리효율 90% 이상 $N_2O$의 분해가 가능한 촉매의 Formulation과 분해기술을 확립하여 각종 응용분야에 효율적으로 적용하기 위한 공정시스템의 개발에 최종목표를 두었음.
$\circ$ 연구개발의결과 $200^{\circ}C$ 저온에서부터 고온 영역까지 GHSV 100,000/hr 의 조건에서 $N_2O$ 분해를 효과적으로

$\circ$ 본 연구에서는 $350^{\circ}C$이하의 반응온도 영역에서 처리효율 90% 이상 $N_2O$의 분해가 가능한 촉매의 Formulation과 분해기술을 확립하여 각종 응용분야에 효율적으로 적용하기 위한 공정시스템의 개발에 최종목표를 두었음.
$\circ$ 연구개발의결과 $200^{\circ}C$ 저온에서부터 고온 영역까지 GHSV 100,000/hr 의 조건에서 $N_2O$ 분해를 효과적으로 수행할 수 있는 혼합금속산화물(MMO) 촉매의 제조, 촉매조성 및 분해공정 시스템을 확립하였음.
$\circ$ NOx, $O_2$ 등에 의한 영향을 최소화할 수 있는 CO 환원제 이용의 효용성과 Methane의 부분 산화를 이용하는 Dual-Bed System에 의한 $N_2O$ 분해제거 기술 및 나아가 NOx까지 동시 처리할 수 있는 촉매시스템을 구현하였음.
$\circ$ 나아가 이들의 상용화 과정에 소요되는 세라믹 성형과정의 핵심부분인 Porosity 및 수축비율 등에 대한 첨가제들의 종류와 비율 등 자료를 취득하여 세라믹 촉매 Monolith 제조기술에 대한 기틀을 마련하였음.

Abstract ▼

The global warming effect causes a lot of serious problems in natural environment such as the climate changes, the rising of sea level, and other various influences on human life, and it has been raised mostly by the increased accumulation of various green house gases. Understanding the significance

The global warming effect causes a lot of serious problems in natural environment such as the climate changes, the rising of sea level, and other various influences on human life, and it has been raised mostly by the increased accumulation of various green house gases. Understanding the significance of global worming effect, many countries are participating in reducing the emission of greenhouse gases.
Nitrous oxide($N_2O$) is one of the major greenhouse gases having warming potential 310 times that of carbon dioxide and chemically very stable in the atmosphere to give a life time of more than 120 years. Its production has been increased faster recently and the sources are diverse. Though large content of $N_2O$ is produced in nitric acid or adipic acid manufacturing plants, $N_2O$ is generally produced with nitrogen oxides in fossil fuel combustion and even through the reduction processes of nitrogen oxides. Global accumulation of $N_2O$ is estimated to around 6% of whole greenhouse gases.
The direct removal of $N_2O$ is usually not easy. When both components exist together, the problem becomes more complex. For the removal of $N_2O$ and NOx, selective catalytic reduction(SCR) systems are generally used with reducing agents. The SCR processes reported generally needs operation at temperatures over $400^{\circ}C$ to get a higher than 90% decomposition efficiency. The aim of this research is to find the catalyst formulation and appropriate process system which can decompose $N_2O$ effectively at the temperature range lower than $350^{\circ}C$. This study is based on the results of experimental and theoretical examinations on the catalytic decomposition of sole nitrous oxide($N_2O$) and a series of selective catalytic reduction or non-selective catalytic reduction(NSCR) of $N_2O$ with $CH_4$ and CO reductants in the presence of excess oxygen and the impurities such as NO over a fixed bed of Co, Al, and other transition metal-containing mixed metal oxide(MMO) catalysts obtained from the calcination of hydrolatcite-type precursors at $500^{\circ}C$.
The decomposition reactions were carried out under atmospheric pressure in the temperature range of $250-500^{\circ}C$ and at a space velocity of $30,000{\sim}100,000\;h^{-1}$. The $N_2O$ decomposition experiments were examined in the absence or presence of NO and excess oxygen. The presence of oxygen results in an inhibition effect on the $N_2O$ decomposition activity of the catalyst. However, when $CH_4$ is fed together with $O_2$, preferably at an optimum $CH_4$ to $O_2$ mole ratio, the $N_2O$ conversion activity is enhanced.
The direct use of CO as a reductant resulted in a hundreds to thousands times increase in decomposition rate and efficiency of $N_2O$, which leads to the decomposition of $N_2O$ more than 99% at $200^{\circ}C$. Also, the presence of NO, which acts as a significant inhibitor in direct $N_2O$ decomposition, was proven to be decomposed more readily than $N_2O$ when CO is fed slightly in deficit of equivalent quantity. When sufficient met of CO is fed in the system, $N_2O$ decomposition is followed.
The hydrotalcite-derived MMO catalysts tested herein were also found very active and selective in the simultaneous destruction of $N_2O$ and NO in the presence of CO at a temperature of $250^{\circ}C$. However, the presence of oxygen inhibits the destruction of $N_2O$ seriously even in the presence of CO, which implies that the rate of oxygen desorption by CO is also a rate-determining step. A plausible mechanism for $N_2O$ destruction in the presence of CO in the feed explaining both the scavenging effect of CO and surface reaction of adsorbed CO with gaseous $N_2O$, is suggested. In the presence of CO in excess of $N_2O$, the surface reaction of adsorbed CO with bulk(gaseous) $N_2O$ is expected mostly to promote the $N_2O$ destruction.
To effectively use the CO reductant in $N_2O$ decomposition, dual bed reaction system has been devised wherein the first catalyst bed was employed for the generation of CO by the partial oxidation of methane and second catalyst bed for the $N_2O$ destruction. In the dual-bed system investigated herein, for the first catalyst bed operation the various reaction parameters(viz. $CH_4/O_2$ ratio, GHSV, temperature etc.) in the partial oxidation of methane over a hydrotalcite catalyst were studied to obtain the maximum CO productivity and the $N_2O$ destruction(in the second reactor) over various hydrotalcite-derived catalysts was investigated at the maximum CO productivity in the first bed.
The presence of NO which can significantly reduce the $N_2O$ decomposition activity over the hydrotalcite catalysts was proven affecting little when excess amount of CO(obtained form first catalyst bed) was present in the second bed, both $N_2O$ and NO were converted into $N_2$. An excellent $N_2O$ conversion activity even at lower temperature($<250^{\circ}C$) was obtained with Co-Pd-Al(2/0.1/1) hydrotalcite-derived mixed metal oxide catalyst by combining Co-Rh-Al(1/0.2/1) hydrotalcite catalyst for the partial oxidation of methane in a dual-bed system.
Besides to the researches on the catalyst activity, fundamental and basic studies on the ceramic manufacturing have been performed to obtain shrinkage ratio, porosity and other physical properties depending on the ceramic ingredients, additives and sintering temperatures for the manufacturing of monolithic type of catalyst support. Also, several molds were manufactured for the extrusion of ceramic honeycomb, with which honeycombs were extruded and sintered with cordierite and some additives for trial purpose. The test manufacturing of ceramic honeycomb showed promisingly good features for future monolithic catalyst manufacturing.

목차 Contents

• 제 1 장 연구개발의 개요...20
• 제 1 절 연구개발의 필요성...20
• 제 2 절 연구개발의 범위...30
• 제 2 장 국내외 기술개발 현황...32
• 제 1 절 국내외 탈질 기술 현황...32
• 제 2 절 국내외 유사기술과의 차별성...39
• 제 3 장 연구개발의 수행 내용 및 결과...42
• 제 1 절 이론적 고찰...42
• 제 2 절 실험 및 분석...59
• 제 3 절 $CH_4$ 환원제에 의한 $N_2O$ 분해성능 연구...77
• 제 4 절 CO 환원제에 의한 $N_2O$ 분해 성능...101
• 제 5 절 Methane 부분산화에 의한 Dual-Bed $N_2O$ 분해성능...136
• 제 6 절 Monolithic Catalyst 제조특성...180
• 제 7 절 연구개발의 결과...258
• 제 4 장 연구개발의 성과 및 관련분야에의 기여도...262
• 제 5 장 연구개발결과의 활용계획...266
• 제 6 장 연구개발과정에서 수집한 해외과학기술정보...270
• 제 7 장 참고문헌...276