锡负载量对PtSn/Al2O3催化丙烷脱氢性能的影响

采用羰基合成-浸渍法制备了不同Pt/Sn摩尔比(3:1, 1:1, 1:2和1:3)的PtSn/Al₂O₃催化剂, 利用N₂吸附-脱附实验、 X射线衍射(XRD)、 透射电子显微镜(TEM)、 吡啶吸附红外光谱(Py-IR)和热重-差热分析(TG-DTA)等手段对其进行了表征, 研究了Sn负载量对PtSn/Al₂O₃的结构性质及催化丙烷脱氢性能的影响. 结果表明, 制备的PtSn/Al₂O₃具有较高的丙烯选择性和稳定性. 当Pt/Sn摩尔比为3:1和1:1时, 铂和锡在催化剂上主要以Pt₃Sn和PtSn合金形式存在, 合金的形成明显改善了催化剂的脱氢性能, 可抑制金属颗粒的高温烧结; 当Pt/Sn摩尔比为1:2和1:3时, 铂主要以金属形式存在. 随着Sn负载量的增加, 催化剂上L酸性位逐渐减少, 丙烷转化率降低, 丙烯选择性增加, 同时促使反应积炭从金属表面向载体迁移, 改善了催化剂的稳定性.

Effects of Sn Loading on Catalytic Performance of PtSn/Al2O3 in Propane Dehydrogenation†

PtSn/Al₂O₃ catalysts with different Pt/Sn molar ratios(3:1, 1:1, 1:2 and 1:3) were prepared by carbonylation-impregnation method. The catalysts were characterized by means of nitrogen adsorption-desorption, X-ray diffraction(XRD), transmission electron microscopy(TEM), infrared spectra of pyridine adsorption(Py-IR), and thermogravimetric-differential thermal analysis(TG-DTA). The effect of Sn loading on the catalytic properties of PtSn/Al₂O₃ in the propane dehydrogenation was studied. The results showed that the PtSn/Al₂O₃ catalyst had high propylene selectivity and catalytic stability. Platinum and tin were mainly in the form of Pt₃Sn and PtSn alloys with Pt/Sn ratios of 3:1 and 1:1. With the formation of the alloy, the dehydrogenation performance of the catalyst was improved significantly, and the high temperature sintering of metal particles was effectively suppressed. When the Pt/Sn ratio was 1:2 and 1:3, the metallic Pt was mainly resulted. With the increase of Sn loading, the Lewis acid sites on the catalyst gradually decreased, and the propylene selectivity increased associated with the propane conversion decreased. At the same time, the addition of Sn promoted the migration of carbon deposition from the metal surface to support, and improved the stability of the catalyst.