Search / Korean Journal of Chemical Engineering
HWAHAK KONGHAK,
Vol.41, No.1, 33-40, 2003
이산화탄소로부터 올레핀 합성을 위한 혼성 촉매와 Fischer-Tropsch 합성 촉매의 비교 연구
Comparative Studies on Catalytic Conversion of CO2 into Olefin with Hybrid Catalysts and Fischer-Tropsch Synthesis Catalysts
이산화탄소로부터 메탄올을 경유하여 올레핀을 생산하는 연계 공정 대신, 이산화탄소로부터 올레핀을 직접 합성하는 일괄 공정을 위하여 두 가지 촉매계를 시험하여 보았다. 즉, 메탄올 합성용 촉매와 메탄올 전환용(Methanol to Olefin process: MTO) 촉매를 혼합하여 구성된 혼성 촉매계와 종래의 Fischer-Tropsch 공정에서 사용되는 철 촉매계를 기반으로 하여 개선된 촉매계를 사용하여 보았다. 일괄 공정 중, 혼성촉매계에서는 Cu/ZnO/Al2O3와 Mg-La/ZSM-5로 구성된 혼성촉매가 가장 우수한 이산화탄소 전환 활성을 나타냈으나 구리에 기인한 중간세기 산점의 증대와 강산점의 소멸로 인하여 올레핀의 선택성은 미비하였다. 반면에 종래에 F-T 공정에 사용되는 철 촉매계의 경우 ZSM-5를 담체로 사용하고 특히 알칼리 금속인 K를 조촉매로 사용할 경우 CO2 흡착량을 증가시키게 되며 동시에 촉매 표면에 흡착된 Fe-C종의 결합 강도를 높여 줌으로 인하여 높은 이산화탄소 전환율과 올레핀 선택도를 확보할 수 있었다.
One-step conversions of CO2 into olefins were investigated over conventional Fischer-Tropsch synthesis(FTS) catalyst and the new hybrid catalysts. The hybrid catalyst was consisted of methanol synthesis catalyst(Cu/ZnO/Al2O3, Cu/ZnO/ZrO3) and methanol to olefin(MTO) catalyst(Mg-La/ZSM-5). The activity of hybrid catalytic system, which was mixed with Cu/ZnO/Al2O3(6:3:1 in weight ratio) and Mg-La-ZSM-5, was superior than others in terms of CO2 conversion and total hydrocarbon yield, but olefin was not produced significantly. The reason was supposed to be caused by Cu-support interaction, which gives rise to the loss of strong Bronsted acid site and consequently the medium strength acid site production. In contrary to hybrid system, the modified F-T catalytic system showed similar enhanced CO2 conversion. However, it showed high selectivity to olefin. When ZSM-5 was used as a support for Fe-K catalyst system, the selectivity of olefin was found to be increased. The addition of potassium promoters give rise to increase amount of CO2 uptake on the surface, and the improvement of stability in adsorbed Fe-C species. Consequently, by carefully selecting the support and additives on modified F-T catalyst system, it was possible to obtain the high CO2 hydrogenation activity as well as high olefin selectivity.