Cr对Pt-Sn／γ-Al2O3催化剂丙烷脱氢性能的影响
摘要
The effect of Cr addition to Pt-Sn/γ-Al2O3 catalyst on the activity, selectivity and deactivation in the propane dehydrogenation was studied. The fresh catalysts were characterized by H2-TPR and the amount of deposited carbon on used catalysts was analyzed by O2-pulse technology. The results of propane dehydrogenation showed that the addition of Cr to Pt-Sn/γ-Al2O3 catalyst can greatly reduce the deactivation rate and increase the selectivity to propene. The mean yield of propene over Pt-CrSn/γ-Al2O3 catalyst reached 38%, which was higher than that of Pt-Sn/γ-Al2O3 catalyst (about 33%). The O2-pulse experimental showed that the amount of deposited carbon on tri-metallic catalyst was much smaller than that on bimetallic catalyst. The synergetic effect between Cr and Pt-Sn took place. Pt promoted the reduction of Cr(superscript 6+) to Cr(superscript 3+), which could increase the selectivity to propene. The addition of Cr to Pt-Sn/γ-Al2O3 also made the reduction of Sn more difficult and stabilizes the oxidation state of tin. The presence of oxidation state of tin would promote the stability of catalyst. This may suggest that the presence of Cr can prevent the formation of PtSn alloy and can promote the stability of Pt-Sn/γ-Al2O3 catalyst in dehydrogenation of propane.