본 연구에서는 졸-겔법으로 각각 Pt/Alumina와 Mo/Alumina를 제조하고 solid state 27Al NMR, X-ray absorption fine structure (XAFS), TEM, ...
본 연구에서는 졸-겔법으로 각각 Pt/Alumina와 Mo/Alumina를 제조하고 solid state 27Al NMR, X-ray absorption fine structure (XAFS), TEM, XRD, BET, 수소 흡착법, 에탄 수소분해반응, 벤젠수소첨가반응, 티오펜 탈황반응 등으로 촉매의 특성을 분석하고, 일반적인 함침법으로 제조한 촉매와 비교하였다. 또한 졸-겔법으로 Co-Mo/Al2O3 촉매를 제조하여 코발트에의한 상승효과도 조사하였다. 졸-겔법으로 제조한 Pt/Al2O3 촉매의 BET 표면적, 기공 크기, 기공 부피 등의 물리적 특성은 함침법으로 제조한 촉매와 거의 비슷하였다. 또한 EXAFS 결과에 의하면, 졸-겔법, 함침법으로 제조한 촉매의 백금 입자의 크기는 약 1 nm 이하로서 거의 비슷한 크기를 가지고 있었다. 그러나 수소가 흡착할 수 있는 백금 입자의 표면적이 함침촉매보다 졸-겔 촉매가 작았다. 즉, 졸-겔 촉매의 수소흡착량은 함침촉매보다 약 30 \% 정도 감소하였다. 그런데, 벤젠 수소첨가반응의 turn over frequency (TOF)는 졸-겔 촉매와 함침 촉매사이에 차이가 거의 없었다. 그러나 에탄 수소분해반응의 TOF 는 함침 촉매에 비해 졸-겔 촉매가 one order 정도 작았다. 이것은 에탄과 수소가 접근 불가능한 활성점들이 존재하는 것을 보여주는 것으로서, 백금 입자 일부 표면이 알루미나에 의해 둘러싸여 있는 것을 시사한다. 이러한 백금 입자와 알루미나 사이의 강한 상호작용으로 인해 졸-겔 촉매는 고온에서 열적 안정이 함침촉매보다 우수한 특성을 보였다. 알루미나 졸(sol)에 Mo 전구체를 혼합하여 제조한 Mo/Al2O3 졸-겔 촉매에서 몰리브데늄 원자는 알루미나 네트워크에 들어가지 않음을 solid state 27Al NMR로 확인할 수 있었다. 그리고 함침 촉매에 비해 미세한 크기의 몰리브데늄 황화물(MoS2)이 얻어지며, 높은 함량(20\%)까지 미세한 입자 크기를 유지하는 것을 EXAFS 로부터 알 수 있었다. 그래서 졸-겔 촉매에서는 티오펜 탈황반응속도가 함침 촉매에 비해 컸으며, 함량에 따라 선형적으로 증가함을 보였다. 그리고 Co-Mo/Alumina 촉매에서는 코발트 원자가 높은 분산도의 MoS2 활성 입자와 결합하여, 티오펜 탈황반응에서 코발트에 의한 강한 상승효과를 보였다.
본 연구에서는 졸-겔법으로 각각 Pt/Alumina와 Mo/Alumina를 제조하고 solid state 27Al NMR, X-ray absorption fine structure (XAFS), TEM, XRD, BET, 수소 흡착법, 에탄 수소분해반응, 벤젠수소첨가반응, 티오펜 탈황반응 등으로 촉매의 특성을 분석하고, 일반적인 함침법으로 제조한 촉매와 비교하였다. 또한 졸-겔법으로 Co-Mo/Al2O3 촉매를 제조하여 코발트에의한 상승효과도 조사하였다. 졸-겔법으로 제조한 Pt/Al2O3 촉매의 BET 표면적, 기공 크기, 기공 부피 등의 물리적 특성은 함침법으로 제조한 촉매와 거의 비슷하였다. 또한 EXAFS 결과에 의하면, 졸-겔법, 함침법으로 제조한 촉매의 백금 입자의 크기는 약 1 nm 이하로서 거의 비슷한 크기를 가지고 있었다. 그러나 수소가 흡착할 수 있는 백금 입자의 표면적이 함침촉매보다 졸-겔 촉매가 작았다. 즉, 졸-겔 촉매의 수소흡착량은 함침촉매보다 약 30 \% 정도 감소하였다. 그런데, 벤젠 수소첨가반응의 turn over frequency (TOF)는 졸-겔 촉매와 함침 촉매사이에 차이가 거의 없었다. 그러나 에탄 수소분해반응의 TOF 는 함침 촉매에 비해 졸-겔 촉매가 one order 정도 작았다. 이것은 에탄과 수소가 접근 불가능한 활성점들이 존재하는 것을 보여주는 것으로서, 백금 입자 일부 표면이 알루미나에 의해 둘러싸여 있는 것을 시사한다. 이러한 백금 입자와 알루미나 사이의 강한 상호작용으로 인해 졸-겔 촉매는 고온에서 열적 안정이 함침촉매보다 우수한 특성을 보였다. 알루미나 졸(sol)에 Mo 전구체를 혼합하여 제조한 Mo/Al2O3 졸-겔 촉매에서 몰리브데늄 원자는 알루미나 네트워크에 들어가지 않음을 solid state 27Al NMR로 확인할 수 있었다. 그리고 함침 촉매에 비해 미세한 크기의 몰리브데늄 황화물(MoS2)이 얻어지며, 높은 함량(20\%)까지 미세한 입자 크기를 유지하는 것을 EXAFS 로부터 알 수 있었다. 그래서 졸-겔 촉매에서는 티오펜 탈황반응속도가 함침 촉매에 비해 컸으며, 함량에 따라 선형적으로 증가함을 보였다. 그리고 Co-Mo/Alumina 촉매에서는 코발트 원자가 높은 분산도의 MoS2 활성 입자와 결합하여, 티오펜 탈황반응에서 코발트에 의한 강한 상승효과를 보였다.
Physical and chemical properties of alumina-supported Pt and Mo catalysts prepared by sol-gel method were investigated by using BET, chemisorption, transmission electron microscopy (TEM), solid state $^{27}Al$ NMR spectroscopy, X-ray powder diffraction (XRD), and X-ray absorption fine structure (XAF...
Physical and chemical properties of alumina-supported Pt and Mo catalysts prepared by sol-gel method were investigated by using BET, chemisorption, transmission electron microscopy (TEM), solid state $^{27}Al$ NMR spectroscopy, X-ray powder diffraction (XRD), and X-ray absorption fine structure (XAFS), and compared with impregnated catalysts. A series of $CoO-MoO_3/Al_2O_3$ sol-gel catalysts were also prepared to investigate whether the synergistic promotion effect by Co was observed, or not. Catalytic activities of benzene hydrogenation and ethane hydrogenolysis reaction for $Pt/Al_2O_3$ catalysts were measured. For alumina-supported Mo and Co-Mo catalysts, thiophene hydrodesulfurization (HDS) reaction was carried out. The physical properties such as BET surface area, pore size and pore volume of $Pt/Al_2O_3$ prepared by sol-gel method was not significantly changed, compared with those of impregnated catalysts. Extended X-ray absorption fine structure (EXAFS) results showed that the sizes of platinum particles in the sol-gel catalyst were less than 1 nm and were almost same as that of impregnated catalyst. However, hydrogen uptake of sol-gel catalyst was about 30 \% less than that of impregnation catalysts, regardless of metal loading, which indicated that the available metal surface area for chemisorption of hydrogen gas molecules decreased in the sol-gel catalysts than in the impregnated catalysts. No distinct difference in catalytic activity of benzene hydrogenation was observed for both catalysts. However, catalytic activity of the ethane hydrogenolysis for $Pt/Al_2O_3$ sol-gel catalysts was considerably lower than that of impregnated catalyst. This result was from the difference of morphology of platinum particles. In the $Pt/Al_2O_3$ sol-gel catalyst, the platinum particles are strongly anchored into the alumina surface, which was confirmed by the higher thermal resistance against sintering of metal particles than the impregnated catalyst. The $Mo/Al_2O_3$ catalysts with various molybdenum loading was prepared by adding $MoO_2(acac)_2$, dissolved in ethanol, to the boehmite alumina sol driven from aluminum isopropoxide(AIP). Solid state $^{27}Al$ NMR spectroscopy showed that the addition of molybdenum species to alumina sol had no effect on the alumina structure when the molybdenum loading was lower than 20 \%, which indicated that no incorporation of molybdenum species to alumina lattice was occurred. EXAFS results showed that the finely dispersed $MoS_2$ particle was obtained upon sulfidation in the $Mo/Al_2O_3$ catalysts prepared by sol-gel method and that the dispersion of $MoS_2$ on the alumina surface was higher than that of impregnated catalysts. The thiophene HDS activities of $Mo/Al_2O_3$ sol-gel catalysts increased linearly with the molybdenum loading, while, for the $Mo/Al_2O_3$ prepared by impregnation method, the HDS activity leveled off. The $Co-Mo/Al_2O_3$ catalysts prepared by sol-gel method showed a strong synergistic promotional effect by cobalt. This results supports that active- phase of $MoS_2$ is present on the alumina surface in a highly dispersed form.
Physical and chemical properties of alumina-supported Pt and Mo catalysts prepared by sol-gel method were investigated by using BET, chemisorption, transmission electron microscopy (TEM), solid state $^{27}Al$ NMR spectroscopy, X-ray powder diffraction (XRD), and X-ray absorption fine structure (XAFS), and compared with impregnated catalysts. A series of $CoO-MoO_3/Al_2O_3$ sol-gel catalysts were also prepared to investigate whether the synergistic promotion effect by Co was observed, or not. Catalytic activities of benzene hydrogenation and ethane hydrogenolysis reaction for $Pt/Al_2O_3$ catalysts were measured. For alumina-supported Mo and Co-Mo catalysts, thiophene hydrodesulfurization (HDS) reaction was carried out. The physical properties such as BET surface area, pore size and pore volume of $Pt/Al_2O_3$ prepared by sol-gel method was not significantly changed, compared with those of impregnated catalysts. Extended X-ray absorption fine structure (EXAFS) results showed that the sizes of platinum particles in the sol-gel catalyst were less than 1 nm and were almost same as that of impregnated catalyst. However, hydrogen uptake of sol-gel catalyst was about 30 \% less than that of impregnation catalysts, regardless of metal loading, which indicated that the available metal surface area for chemisorption of hydrogen gas molecules decreased in the sol-gel catalysts than in the impregnated catalysts. No distinct difference in catalytic activity of benzene hydrogenation was observed for both catalysts. However, catalytic activity of the ethane hydrogenolysis for $Pt/Al_2O_3$ sol-gel catalysts was considerably lower than that of impregnated catalyst. This result was from the difference of morphology of platinum particles. In the $Pt/Al_2O_3$ sol-gel catalyst, the platinum particles are strongly anchored into the alumina surface, which was confirmed by the higher thermal resistance against sintering of metal particles than the impregnated catalyst. The $Mo/Al_2O_3$ catalysts with various molybdenum loading was prepared by adding $MoO_2(acac)_2$, dissolved in ethanol, to the boehmite alumina sol driven from aluminum isopropoxide(AIP). Solid state $^{27}Al$ NMR spectroscopy showed that the addition of molybdenum species to alumina sol had no effect on the alumina structure when the molybdenum loading was lower than 20 \%, which indicated that no incorporation of molybdenum species to alumina lattice was occurred. EXAFS results showed that the finely dispersed $MoS_2$ particle was obtained upon sulfidation in the $Mo/Al_2O_3$ catalysts prepared by sol-gel method and that the dispersion of $MoS_2$ on the alumina surface was higher than that of impregnated catalysts. The thiophene HDS activities of $Mo/Al_2O_3$ sol-gel catalysts increased linearly with the molybdenum loading, while, for the $Mo/Al_2O_3$ prepared by impregnation method, the HDS activity leveled off. The $Co-Mo/Al_2O_3$ catalysts prepared by sol-gel method showed a strong synergistic promotional effect by cobalt. This results supports that active- phase of $MoS_2$ is present on the alumina surface in a highly dispersed form.
Keyword
#Sol-Gel Pt Mo Alumina Catalyst 솔-겔 백금 몰리브데늄 알루미나 촉매
학위논문 정보
저자
Cho, Ihl-Hyun
학위수여기관
한국과학기술원
학위구분
국내박사
학과
화학공학과
지도교수
박승빈,Park Seung-Bin
발행연도
1997
총페이지
ix, 114 p.
키워드
Sol-Gel Pt Mo Alumina Catalyst 솔-겔 백금 몰리브데늄 알루미나 촉매
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