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.

Unsupported Co-Mo Catalyst FEAG Spray Pyrolysis Hydrodesulfurization

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