Development Of PtSnIn Catalyst Applied To Propane Dehydrogenation

Propylene is a vital raw material for the industrial production of polypropylene, acrolein, polyacrylonitrile and acrylic acid. Since the demand for propylene is continuous growing, much more attention is paid to new technologies to produce propylene. The bimetallic platinum-tin(Pt-Sn) supported catalysts exhibited rather good catalytic performance in propane dehydrogenation. Our previous work demonstrated that the trimetallic Pt Sn In/Al catalysts exhibited high catalytic performances in propane dehydrogenation reaction. However, the catalytic stability of Pt Sn In/Al catalysts still needs further improvement. The purpose of this paper is to improve the catalytic acitivity and stability of Pt Sn In/Al catalysts for propane dehydrogenation reaction. The contents of this paper are listed as follows:1. Determined the promotion effects of alkaline earth metals(Mg, Ca) or alkali metals(K, Na) addition in Pt Sn In/Al catalysts for propane dehydrogenation reaction. The catalytic stability of the trimetallic Pt Sn In supported catalysts for propane dehydrogenation reaction is markedly improved by using Ca-doped γ-Al2O3 as support. The NH3-TPD measurements verify that the surface acidity of the synthesized Pt Sn In/x Ca-Al catalysts decreases with the addition of Ca. The TEM images reveal that Pt Sn In/1.5Ca-Al catalyst has the smallest Pt particle size of 5 nm and satisfied particle distribution. The XPS and H2-TPR verify that the state of metal species and its interaction with support are influenced by Ca species. After adding 0.6-1.5 wt.% Ca species, the catalytic stability of the Pt Sn In/x Ca-Al catalysts is evidently improved. However, over high Ca loading leads to a decrease of propane conversion and catalytic stability. For Pt Sn In/1.5Ca-Al catalyst, the propane conversion has little decline and keep at high level above 58.0% until 25 h reaction time, and the final propane conversion of 34.0% is obtained even after 100 h reaction. In addition, Mg has similar effect with Ca addition. However, Na and K addition have no such effective influences.2. The performances of zirconia-, alumina-, and zirconia-alumina-supported Pt Sn In catalysts for propane dehydrogenation to propylene are studied with several state-of-art characterizations including XRD, BET, NH3-TPD, FESEM with corresponding EDX, TEM, H2-TPR and XPS measurements. The results show that zirconia-loaded alumina sample used as support for trimetallic Pt Sn In catalysts improves the catalytic performances signi?cantly. Zirconia deposited on alumina decreases the Lewis acidity of the support, which can be verified by NH3-TPD measurements. The TEM images show that Pt Sn In/08Zr-Al catalyst has the smallest Pt particle size of 12 nm and homogenized particle distribution. The XPS and H2-TPR techniques verify that zirconia-loaded alumina influences the state of metals and its interactions with support. In this study, it could keep the initial propane conversion and propylene selectivity above 55% and 98% for Pt Sn In/08Zr-Al catalyst, respectively. In addition, the catalytic performances of Pt Sn In/08Zr-Al catalyst are maintained excellent even used for four recycles. The initial propane conversions in four recycles are all above 55% and only decrease little(~3%) in the fourth recycle. However, bare zirconia supported Pt Sn In catalyst displays the worst catalytic activity and the most serious deactivation, which due to a decoration effect of Pt by zirconia support in hydrogen atmosphere.3. The yttrium(Y)-modified γ-Al2O3 was used as support for trimetallic Pt Sn In catalysts(Pt Sn In/x Y-Al) and applied in propane dehydrogenation reaction. The Pt Sn In/x Y-Al catalysts were characterized by several state-of-art techniques such as XRD, BET, NH3-TPD, FETEM, H2-TPR, XPS, and TG measurements. The results show that the catalytic performance of Pt Sn In/x Y-Al catalysts for propane dehydrogenation reaction is clearly improved. The NH3-TPD curves demonstrate that Y-modified γ-Al2O3 could greatly weaken the acidity of support. The Pt Sn In/0.6Y-Al catalyst has the smallest Pt particle size of 16 nm and homogenized particle distribution, which can be observed by TEM images. XPS and H2-TPR techniques verify that the loading of Y influences the state of metals and its interactions with support. In this study, it could keep the initial propane conversion and propylene selectivity above 50% and 97% for Pt Sn In/0.6Y-Al catalyst, respectively. The TG analysis proves that the spent Pt Sn In/0.6Y-Al catalyst has the least coke content. However, with excessive Y loading, the agglomerations of Pt particles and the increase in percentage of metallic(Sn0) are found, which leads to the loss of catalytic activity and serious deactivation of catalyst.