Didymium catalyst

Neodymium-based catalysts are favored over other Ln metals because they are highly active and the catalyst precursors are readily available for reasonable prices. In addition, Nd catalyst residues do not catalyze aging of the rubber. The use of didymium catalyst systems is also reported in the literature. Didymium consists of a mixture of the three lanthanides neodymium (72 wt. %), lanthanum (20 wt. %) and praseodymium (8 wt. %). 

In the context of ternary catalyst systems Throckmorton s pioneering work is worth mentioning although in this study Ce rather than Nd-based catalyst systems were used. For the two catalyst systems Ce octanoate/TIBA/DEAC and Ce octanoate/TIBA/EADC catalyst activities increased up to TiBA/ Ce = 20. Further increases in the TiBA/ Ce-ratios from 20-60 did not result in further activity improvements [34]. For a ternary didymium (Di)-based oc-tanoate catalyst system Witte described a similar dependence. Within the wAl/ Di-range 20-40 significant increases of polymerization rates were reported. Further increases of the nAi//iDi-ratios did not have an additional effect [49]. 

For ternary catalyst systems the decrease in cis- 1,4-contents with increasing Ai/ Nd-ratios is a common feature. The first report in which the decrease of ds-1,4-contents with increasing cocatalyst concentrations is addressed dates back to Throckmorton s study in which Ce-based catalyst systems were used [34]. The same dependence was confirmed in a subsequent study in which didymium octanoate-based catalysts were used [49]. In this study BD was polymerized and a decrease of the cis- 1,4-content from 95% at Al/ Di = 20 to 90% at Ai/ r)i = 60 is reported. 

Neodymium 60 Nd Electronics, steel manufacture, glazes and coloured glass (including didymium glass), lasers, magnets, petroleum cracking catalysts, misch metal ... 

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