摘要
正丁烷分子结构相对稳定,C-C键键能较高,难以有效利用,目前大部分作为低价值燃料,通过脱氢、裂解等反应将正丁烷转化为高附加值的轻烯烃研究具有重要的科学意义.采用分步浸渍法将Pt和Ga负载到CeO2-ZrO2-Al2O3(CZA)载体制备PtGa/CZA催化剂,将Pt-Ga2O3引入作为脱氢位点进行脱氢反应(C4H10→C=4),CZA作为酸位点进行裂解反应(C=4→C=3,C=2),同时PtGa与CZA协同提高表面吸附氧含量降低正丁烷活化温度.结果表明,与负载单Pt或Ga催化剂相比,将Pt和Ga同时负载到CZA载体上,可极大提高反应的转化率和选择性,在500℃时,PtGa/CZA催化剂的正丁烷转化率为64.3%,比Pt/CZA和Ga/CZA催化剂分别高55.9%和53.9%,三者轻烯烃选择性均在95%以上.将PtGa/CZA催化剂制成涂层催化剂,提高了正丁烷转化率和催化剂稳定性.PtGa/CZA催化剂优异的活性归因于较低的Ce4+还原温度和表面吸附氧脱附温度、较多的表面吸附氧位点含量和强酸位点含量.
Abstract
The molecular structure of n-butane is relatively stable with high C—C bond energy,which makes it difficult to be effectively utilized,and most of it is currently burned as a low-value fuel.The study of converting n-butane into high-value-added light olefins through dehydrogenation,cracking,and other reactions is also of great scientific significance.In this study,Pt and Ga were sequentially impregnated onto CeO2-ZrO2-Al2O3(CZA)support by using a stepwise method to prepare the PtGa/CZA catalyst.Pt-Ga2 O3 was introduced as a dehydrogenation catalyst for the conversion of C4 H10 to C=4,while CZA functions as an acid catalyst for the cracking reactions leading to C=4→C=3 and C=2.Simultaneously,PtGa and CZA synergistically enhance the surface oxygen adsorption capacity and reduce the activation temperature required for n-butane.The results demonstrated that simultaneous loading of Pt and Ga onto the CZA support significantly enhanced both conversion rate and selectivity compared to single-loaded Pt or Ga catalysts.At 500℃,the conversion rate of n-butane over the PtGa/CZA catalyst reached 64.3％,which was 55.9％higher than that achieved with the Pt/CZA catalyst and 53.9％higher than that obtained with the Ga/CZA catalyst.All three catalysts exhibited selectivity above 95％.The PtGa/CZA catalyst was made into a coated catalyst to improve n-butane conversion and catalyst stability.The excellent activity of the PtGa/CZA catalysts was attributed to the lower Ce4+reduction temperature and surface adsorbed oxygen desorption temperature,as well as the larger surface adsorbed oxygen site content and strong acid site content.
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