Methanol synthesis and hydrocarbon synthesis from carbon dioxide and hydrogen were studied over the metal oxides catalyst and the metal oxides/molecular sieve hybrid catalysts, respectively.
CuO/ZnO/$ZrO_2$(60/30/10 in weight%) among other mixed metal oxides was the most effective for methanol synthesis. When $Fe_2O_3$ was incorporated in the methanol synthesis catalyst, the $CO_2$ conversion and the selectivity toward hydrocarbons were improved. The hydrocarbon produced had a typical Shultz-Flory distribution as in a Fischer-Tropsch reaction when the reaction temperature was higher than 300℃.
Direct hydrocarbon synthesis was carried out over the hybrid catalysts composed of methanol synthesis catalyst(CuO/ZnO/$ZrO_2$) and molecular sieve (HZSM-5, SAPO-34). SAPO-34 hybrid catalyst was superior to the HZSM-5 hybrid catalyst in view of hydrocarbon yield. SAPO-34 hybrid catalyst also showed a higher selectivity to the $C_2$-$C_5$ hydrocarbon.
The temperature-programmed-desorption(TPD) of ammonia for the hybrid catalysts showed a new spectrum which did not appear in each of methanol synthesis catalyst (CuO/ZnO/$ZrO_2$) and zeolites. This new spectrum was assigned for the acid sites with medium strength. It was observed that the amount of the acid sites with medium acidity was in good correlation with the activity, especially the hydrocarbon yield.
Cu-ion exchanged HZSM-5(Cu-HZSM-5) was mixed with CuO/ZnO/$ZrO_2$ catalyst in order to explain the effect of interaction between Cu of CuO/ZnO/$ZrO_2$ and HZSM-5. The increase in the amount of ion-exchanged Cu resulted in the increase of both the hydrocarbon yield and the amount of medium acid sites. This suggested that the copper was the main component for the interaction and the new acid sites.
The roles of Cu in the hybrid system was also investigated by various characterization tools such as XRD, XPS, TPR and TPO.
이산화탄소와 수소를 반응물로 사용하여 메탄올합성과 탄화수소 합성반응을 금속산화물촉매와 금속산화물/제올라이트 혼성촉매상에서 각각 수행하였다. 메탄올합성에서는 제조된 금속산화물 촉매중 CuO/ZnO/$ZrO_2$(60/30/10)가 가장 큰 활성을 보였다. $Fe_2O_3$이 첨가된 촉매의 경우 300℃ 이상에서 이산화탄소의 전환율이 높아지고 탄화수소로의 선택도가 커졌으며, 생성된 탄화수소는 Shultz-Flory 분포를 나타내었다. 탄화수소 직접합성은 금속산화물과 제올라이트(HZSM-5, SAPO-34)의 물리적 혼합으로 제조된 혼성촉매상에서 이루어졌다. SAPO-34의 혼성촉매가 HZSM-5의 혼성촉매보다 탄화수소 수율면에서 우수하였으며 생성된 탄화수소는 $C_2$-$C_5$의 높은 선택도를 나타내었다. 혼성촉매의 암모니아 승온탈착 실험에서는 금속산화물(CuO/ZnO/$ZrO_2$)이나 제올라이트에서 볼수 없었던 새로운 중간세기 산점으로 생각되는 피크가 나타났다. 이 중간산점의 크기가 클 수록 탄화수소의 수율이 높아졌다. 금속산화물의 활성 금속성분인 구리와 제올라이트와의 상호작용을 규명하기위해 구리가 이온교환된 HZSM-5혼성촉매를 반응에 적용하였다. 이온교환된 구리가 증가할 수록 탄화수소 수율증가와 중간산점양의 증가가 관찰되었다. 이는 구리가 상호작용과 새로운 중간산점의 형성에 관여하는 중요한 원인임을 말해준다. 혼성촉매 시스템에서의 구리의 역활을 설명하기위해 XRD, XPS, TPR, TPO등의 분석을 수행하였다.
