Study of the Dehydrogenation Characteristics of Pt-Sn Catalysts by Propane Pulse Injection

프로판 펄스 주입에 의한 백금주석촉매의 탈수소반응 특성 연구

Abstract

The results of the catalytic reaction by pulsed injection of reactants are useful for studying the initial reaction characteristics in the case of many coke invloved reactions. The dehydrogenation characteristics of alumina supported platinum tin catalysts were investigated by pulsed injection of propane. The yield of propylene was maximized when the reduction time of propane injection catalyst was $550^{\circ}C$. Raman analysis showed that the amount of coke was very small when PtSn (4.5) catalyst was used and the short contact time was simulated by propane pulse injection. n order to differentiate the degree of dispersion of platinum, PtSn (4.5) catalyst was sintered at $900^{\circ}C$ with hydrogen, and then the temperature of air - redispersion was varied and propane pulse was injected. As a result, conversione and yield were the highest when air-redispersion temperature is $600^{\circ}C$. The lower the air-redispersion temperature, the higher the selectivity. As the tin content in the platinum catalyst increased, the propane conversion was lowered, but the selectivity to propylene increased and the yield increased. From this, it can be seen that the tin-added platinum catalyst is less active than the platinum catalyst from the beginning of the reaction, which is less affected by coke. The dehydrogenation reaction by the propane pulse injection shows a higher conversion rate than the result of continuous injection due to the formation of COx, and the amount of coke is very small. Decrease in selectivity due to the formation of COx can be reduced by increasing the reduction temperature and time.

반응물의 펄스주입에 의한 촉매반응결과는 코크가 많은 반응의 경우 초기반응특성을 연구하는데 유용하다. 프로판의 펄스주입으로 알루미나에 담지된 백금주석촉매의 탈수소 반응 특성을 연구하였다. 프로판 주입전 촉매의 환원을 $550^{\circ}C$에서 한 경우, 환원시간이 1시간인 경우 프로필렌의 수율이 최대가 되었다. PtSn (4.5)촉매를 사용하고, 프로판 펄스 주입에 의해 짧은 접촉시간을 모사한 경우 코크의 양이 매우 적었음을 Raman분석으로 알 수 있었다. 백금의 분산도를 다르게 하기위하여 PtSn (4.5)촉매를 수소로 $900^{\circ}C$에서 신터링 후 공기-재분산시의 온도를 다르게 처리한 후, 프로판 펄스 주입한 결과 공기처리 온도가 $600^{\circ}C$ 일 때 프로판의 전환율과 수율은 가장 높았다. 공기-재분산의 온도가 낮을수록 선택도는 높았다. 백금촉매에 주석함량이 증가함에 따라 프로판 전환율은 낮아졌지만, 프로필렌으로의 선택도는 높아져서, 수율은 증가하였다. 이로부터 주석을 첨가한 백금촉매는 코크의 영향이 적은 반응초기부터 백금촉매보다 활성이 낮다는 것을 알 수 있다. 프로판 펄스주입에 의한 탈수소반응은 COx의 생성에 의해 연속주입에 의한 결과보다 높은 전환율을 보이고, 코크의 양이 매우 적은 특징을 보이고 있다. COx의 생성에 의한 선택도 하락은 환원온도와 시간을 증가시키면 줄일 수 있다.

Fig. 1. Shematic diagram for propane pulse-injection dehydrogenation reaction test equipment.

Fig. 2. Propane pulse-injection dehydrogenation performance of PtSn (4.5) with reduction duration time (T = 550 ℃, feed pulse: propane 50/nitrogen 50 = 100 μL, catalyst 01.g).

Fig. 3. Effect of reduction temperature on catalytic performance of propane pulse-injection dehydrogenation (T = 550 ℃, feed pulse: propane 50/nitrogen 50 = 100 μL, catalyst 01.g).

Fig. 4. Effect of air-redispersion temperature after hydrogen sintering on catalytic performance of propane pulse-injection dehydrogenation of PtSn (4.5) (T = 550 ℃, feed pulse: propane 50/nitrogen 50 = 100 μL, catalyst 01.g).

Fig. 5. Effect of added Sn amount to platinum catalyst on propane pulse-injection dehydrogenation reaction (T = 550 ℃, feed pulse: propane 50/nitrogen 50 = 100 μL, catalyst 01.g).

Fig. 6. XRD patterns of PtSn(4.5) catalysts of air-redispersion after hydrogen-sintering with various temperature.

Fig. 7. Raman spectroscopy of used PtSn(4.5) catalysts with various air-redispersion temperature after hydrogen-sintering.

Fig. 8. XPS spectra of used PtSn(4.5) catalysts with various air-redispersion temperature after hydrogen-sintering.

Table 1. XPS analysis of catalysts subjected to different conditions