Halogen Free Methods for Catalysts Regeneration

摘要CTS-9502141 这一努力为用α-二酮取代用于再分散负载型金属催化剂的氯奠定了基础。 先前的工作表明，β-二酮与过渡金属及其氧化物反应形成β-二酮，并且这些可以还原为活性催化剂。 初步实验表明，氧化铝上的铂可以用六氟-2，4-戊二酮（hfac）处理再分散。 本研究详细探讨了再分散过程。 透射电子显微镜（TEM）用于确定再分散是否通过蚀刻机制或扩散机制进行。 采用程序升温脱附（TPD）方法研究了β-二酮与金属表面及载体的相互作用，包括结合能随配体性质的变化。 光谱和TPD测量与再分散率相关。 对模型催化剂和真实的工业催化剂进行了研究。 目前的实践使用氯来再分散负载的金属催化剂。 虽然这种方法被认为在技术和经济上是令人满意的，但它有一些环境缺点，涉及氯释放到大气中和由留在催化剂上的氯残留物形成氯化二恶英。 那里研究的方法避免了这两个问题，并且可以在不损失任何有效性的情况下做到这一点。 ***

ABSTRACT CTS-9502141 This effort lays the basis for replacing chlorine used for redispersion of supported metal catalysts with a (-diketone. Previous work has shown that (-diketones react with transition metals and their oxides to form (-diketonates, and that these can be reduced back to active catalysts. Preliminary experiments suggest that platinum on alumina can be redispersed by treatment with hexafluoro-2,4-pentanedione (hfac). The present study examines the redispersion process in detail. Transmission electron microscopy (TEM) is used to determine if redispersion goes through an etching, mechanism or a spreading mechanism. Temperature-programmed desorption (TPD) is used to examine the interaction of (-diketones with metal surfaces and supports, including the variation of binding energy with nature of the ligand. Spectroscopic and TPD measurements are correlated with redispersion rates. Studies are done on both model catalysts and real industrial catalysts. Current practice uses chlorine to redisperse supported metal catalysts. While this process is regarded as technologically and economically satisfactory, it has some environmental drawbacks relating both to release of chlorine to the atmosphere and the formation of chlorinated dioxins from chlorine residues left on the catalyst. The approach investigated there avoids both of these problems, and may do so without any loss of effectiveness. ***