The catalysts were prepared by dispersing metals (Pt, Pd, Ni, Co) on activated carbon by wetness impregnation and their catalytic activities were studied through the dehydrogenation of ethylbenzene to styrene.
It was found that ethylbenzene was activated on the surface of activated carbon and the supported metal played an important role in the dehydrogenation as a vent of hydrogen produced during the reaction, which is so called the "Reverse spillover" phenomenon.
From the activities according to the amount of supported metals, Pt and Pd had Volcano curves, while Ni showed a linearly increasing trend with the increase of the metal amount. In the cases of Pt and Pd, their activities were understood through the competition between their hydrogenation ability and hydrogen-ventilating ability. in the case of Ni, the linear dependence of its activity on increasing metal amount was interpreted due to its relatively low hydrogenation ability.
The PAS spectra of Co catalysts indicated that the metals in the metal-carbon system could be reduced by the produced hydrogen besides their roles in the system for the dehydrogenation.
Activated Carbon에 Group VIII의 금속들 (Pt, Pd, Ni)과 Co를 Wetness Impregnation 방법으로 담지시켜 촉매를 제조하였고, Ethylbenzene의 탈수소 반응을 통하여 이 촉매들의 반응 특성을 조사하였다.
Ethylbenzene의 활성화는 Activated Carbon표면에서 일어나고 담지된 금속들은 반응에서 생성된 수소의 Reverse Spillover의 경로로써 역활을 함을 알 수 있었다.
담지된 금속양에 따른 반응 활성도를 보면 Pt, Pd의 경우 volcano curve를 얻었으며, Ni의 경우엔 담지된 양에 따라 활성도가 선형적으로 증가하였다. Pt, Pd 촉매들의 반응 특성은 metal의 수소화 반응 능력과 수소를 기상으로 배출하는 능력의 경쟁 관계로써 설명하였다. 반면 Ni의 경우 금속의 담지양과 반응 활성도 간에 선형관계를 보이는 것은 Pt, Pd에 비해 현저히 떨어지는 Ni의 수소화 반응 능력 때문으로 설명하였다.
또한 생성된 수소는 금속위에서 기상으로 배출되는 외에 금속을 환원시키기도 함을 Co 촉매의 반응 전-후의 PAS (photoacoustic spectroscopy) data를 통하여 알아 내었다.
