물리화학적 성질이 다른 α-알루미나상에서 납사의 접촉 열분해 반응을 수행하여 알루미나의 충진 효과를 조사하였다. 납사의 LHSV는 3-10, 반응온도는 800-880 ℃로 조절하면서 상압하에서 납사 분해 반응을 실시하여 알루미나가 납사 분해 반응의 전환율 및 선택도에 미치는 영향을 순수한 열분해 반응 결과와 비교하여 조사하였다. 알루미나 상에서의 접촉 열분해는 동일한 반응 조건에서의 순수 열분해 반응에 비하여 에틸렌 수율은 10%, 프로필렌 수율은 2% 정도 증가하였으며, 에틸렌 및 프로필렌의 선택도는 순수한 열분해의 경우와 동일하였다. 알루미나 접촉 열분해에서 에틸렌 및 프로필렌 수율이 향상되는 것은 알루미나가 열매체로 작용하여 반응물의 온도를 증가시키고, 소위 "표면 효과"에 의하여 알루미나 표면이 라디칼 생성을 촉진하였기 때문인 것으로 해석되었다. 납사의 알루미나 접촉 분해 반응에서는 알루미나의 기공 특성에 따라 에틸렌 수율이 최대 3% 정도 차이가 났는데, 수십 μm 이상의 거대 기공을 갖는 알루미나가 접촉 열분해 반응에 유리한 것으로 나타났다. 알루미나의 기공이 큰 경우에는 내부 물질 전달 저항이 작고, 코킹에 의한 기공 막힘이 천천히 진행되기 때문에, 납사 분해 반응이 쉽게 일어나며 그에 따라 에틸렌 수율도 증가하는 것으로 해석하였다.

We have studied the effect of physical and chemical properties of α-alumina on the catalytic cracking of naphtha at atmospheric pressure in the temperature range 800-880 ℃ and LHSV range of naphtha 3-10 hr-1. Catalytic effect of alumina on the activity and selectivity for the naphtha cracking was investigated, and the performance of catalytic cracking with alumina was compared with that of thermal cracking. The ethylene and propylene yields increased 10% and 2%, respectively, in naphtha cracking in the presence of α-alumina compared with the non-catalytic thermal cracking at the same experimental condition. However, the selectivity toward ethylene and propylene was about the same for both non-catalytic thermal cracking and catalytic cracking on the α-alumina. The enhancement in the ethylene and propylene yields can be attributed to both the enhanced heat transfer from the reactor wall to the reactant through α-alumina acting as a heat transfer medium and “the surface effect” of the alumina enhancing the formation of the radical. We observed the difference in the ethylene yield by 3 wt% depending on the pore characteristics of α-alumina. It was found that the α-alumina having large pore openings of several tens of μm or higher is favorable in catalytic cracking of naphtha. We ascribe the result to the fact that in such large pores, the mass transfer resistance is less and the pore blocking by coking progresses slowly. That is, the naphtha cracking would take place in the large pores more effectively compared to the small pores and as a result, the higher ethylene yield would be expected in naphtha cracking in the presence of the α-alumina having larger pore openings.

Naphtha Catalytic Cracking Ethylene Propylene Alumina

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