화학공학소재연구정보센터
Journal of the Korean Industrial and Engineering Chemistry, Vol.3, No.1, 53-63, March, 1992
MoO3/bismuth molybdate 혼합 2상 촉매의 구조에 따른 프로필렌 선택산화반응 특성
Effect of the Structure of MoO3/bismuth molybdate Binary Phase Catalysts on the Selective Oxidation of Propylene
초록
프로필렌을 선택산화시켜 아크로레인을 제조하는 반응을 Bi-molybdate 촉매상에서 고정층 반응기를 사용하여 연구하였다. α-Bi2Mo3O12 위에 MoO3를 담지시킨 M/BM-series 촉매는 함침법으초 제조되었고, 역으로 BM/M-series 촉매는 MoO3 위에 α-Bi2Mo3 O 12 을 침전시켜 제조하였다. 또한 촉매의 특성분석을 위하여 질소흡착과 XRD, SEM을 이용하였다. M/BM-series 촉매에서는 MoO3가 작은 입자로 분산되고 α-Bi2Mo3O12의 결정구조는 MoO 3상이 추가되어도 그 형상이 변하지 않는 채로 유지되었으나, BM/M-series 촉매의 표면형상 및 전체 구조는 촉매제조 중에 생기는 침전물인 Bi(OH)3가 소성 도중 MoO3와 반응하여 α-Bi2Mo3O 12 을 형성하는 관계로 그 조성에 따라 매우 불규칙적으로 변화하였다. 반응실험 결과, 두 종류의 촉매 모두에서 excess MoO3가 포함되었을 때 활성이 크게 증가하였는데, 이는 선별산화반응이 주로 α-Bi2Mo3O12 에서 일어나고 MoO3는 α-Bi2Mo3O 12에 산소 공급을 원활히 하여 활성을 증가시키기 때문으로 판명되었다. 또한 이러한 활성 증가는 α-Bi2Mo3O12와 기계적 혼합물 (mechanical mixture)에서도 관찰되었다.
M/BM -series catalysts, MoO3 supported on α-Bi 2Mo 3O12were also prepared by impregnation method. BM/M-series catalysts, α-Bi2Mo3O12 supported on MoO 3 were also prepared by coprecipitation. Structure and catalytic properties of the two phase catalysts were studied by means of using nitrogen adsorption, X-ray diffraction, and scanning electron microscopy. The reaction test for the selective oxidation of propylene to acrolein over Bi -molybdate catalysts was studied using a fixed-bed reactor system. In M/BM-series catalysts, MoO3 was dispersed on α-Bi2Mo3O12, and the crystal structure of α-Bi2Mo3O12 remains unchanged by the pres- ence of excess MoO3. However the surface morphology and bulk structure of BM/M-series catalysts were altered probably because the precipitated Bi(OH) 3 reacted with MoO3 during the calcination to form α-Bi2 Mo3O12 phase. The results of propylene oxidation on both series catalysts showed that the reaction took place over the surface of α-Bi2Mo3O12 particle and the role of excess MoO3 was to supply oxygen to α-Bi2Mo3O 12. These increasing effects on activity were also observed in the mechanical mixtures of α-Bi2Mo3O12 and MoO3.
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