| Issue |
HWAHAK KONGHAK,
Vol.35, No.6, 814-818, 1997
Vol.35, No.6, 814-818, 1997
분무 열분해법으로 제조한 비담지 Co-Mo 촉매의 티오펜 탈황반응
Thiophene Hydrodesulfurization of Un supported Co-Mo Catalysts Prepared by Spray-Pyrolysis Method
Co/Mo 몰비에 따라 분무 열분해법으로 제조한 비담지 Co-Mo 촉매에서 Mo와 Co의 역할을 조사하였다. 비담지 Co-Mo 촉매의 구조와 형태를 알아보기 위하여 BET surface area, X-Ray diffraction pattern(XRD), scanning election microscopy(SEM)과 transmission electron microscopy(TEM) 등으로 조사하였다. 촉매 반응성은 400℃, 상압에서 thiophene hydro-desulfurization(HDS)으로 실험하였다. 비담지 Co-Mo의 결정상은 Co/Co+Mo(=r)의 비에 따라 달라지는 것을 XRD로 확인하였다. r=0.20 이하에서는 MoO3와 CoMoO4 결정이 형성되었다. H2/H2S로 황화 후 벌크의 MoO2와 Co9S8과 나노결정의 MoS2이 생성되었다. 여기서 MoO2는 MoO3의 환원에 의해서, Co9S8은 CoMoO4에서 분리되어 각각 형성되었다. 이 구간에서(r=0.10-0.20) thiophene HDS 반응에 대해 전형적인 상승 효과를 보였고, 반응속도가 가장 컸다. 이러한 결과는 MoO2와 Co9S8가 MoS2를 잘 분산시켜 주는 지지체 역할을 하고 있다는 것으로 설명되었다. 한편 Co의 양이 증가하면(r>0.2), CoMoO4 결정만이 생성되고, CoMoO4 결정은 황화과정에 의해 벌크의 Co9S8와 나노결정인 MoS2으로 바뀌었다. 여기서 벌크의 Co9S8는 MoO2 처럼 지지체 역할을 하여 MoS2를 분산시켜 HDS 반응에서 상승 효과를 일으켰다.
The role of Mo and Co in unsupported Co-Mo catalysts of various Co/Mo ratio prepared by spray pyrolysis method was investigated. The structure and morphology of unsupported Co-Mo were studied by BET surface area, X-Ray diffraction pattern(XRD), scanning electron microscopy(SEM), and transmission electron microscopy(TEM). The catalytic activity was tested by the thiophene hydrodesulfurization(HDS) at 400℃ and atmospheric pressure. The crystal phase of unsupported Co-Mo was changed with Co/Co+Mo(=r) ratio, as revealed by XRD. The MoO3 and CoMoO4 were formed below r=0.2. After the sulfidation with H2S/H2, the bulk MoO2 crystals, Co9S8 crystals, and MoS2 nanocrystal were formed. The MoO2 was formed by the reduction of MoO3, and the Co9S8 was formed by the segregation of CoMoO4. A typical synergistic effect and the highest catalytic activities were observed for the unsupported Co-Mo catalysts when r varies from 0.1 to 0.2 in the thiophene HDS reaction. These results indicated that both MoO2 and Co9S8 act as a support for highly dispersed MoO2. The further addition of Co(r>0.2) leaded to the formation of only CoMoO4 which was transformed into the Co9S8 and MoS2. after the sulfidation. The bulk Co sulfide, like MoO2, served as a carrier for good dispersion of MoS2. The promotional effect was also observed in HDS reaction.
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