Neodymium is a lanthanide chemical element, which is with the symbol Nd and an atomic number of 60. It has a melting point of 1024℃, a density of 7.004 g/cm3, and is paramagnetic. It is one of the most active rare earth metals, which can quickly darken in the air to form oxides. And it reacts slowly in cold water and reacts rapidly in hot water. The neodymium element is mainly used to prepare permanent magnet materials (Nd2Fe14B) and optical glass. In addition, its compounds are sometimes applied as catalyst and show a good catalytic effect.
Neodymium has few commercial uses, becasue it is expensive to prepare the Nd-catalysts. However, in refinery petroleum cracking (oxidative coupling of methane to ethylene), polymerization and photocatalytic wastewater treatment, certain Nd-containing compounds can be used as an effective catalyst for some reason, such as Nd2O3, Nd(P204)3/TIBA/Al, NdH3P2W18O62, Nd-Bi2O3 and etc. There are some specific examples as shown below:
- In refinery petroleum cracking: Ethylene is one of the most important chemical raw materials, mainly from the petroleum cracking route, but the route is expensive and pollutes the environment. The preparation of ethylene by oxidative coupling of methane has been a research hotspot in recent years. Nd2O3 can be used as a good catalyst in this reaction. The reaction scheme is as follows.
Figure 1. The oxidative coupling reaction of CH4
- In polymerization: In the polymerization of diolefins, alkynes, monoolefins, alkylene oxides, esters and the copolymerization, Nd-containing compounds have good catalytic effects. For example, neodymium phosphate-based catalysts can catalyze the copolymerization of CO2 and epichlorohydrin. The specific reaction formula is as follows:
Figure 2. The Reaction schematic of CO2 and C3H5OCl
- In photocatalytic wastewater treatment: Nd-Bi2O3 can be used as a photocatalyst to catalyze the degradation of methyl orange in sewage, so as to achieve the purpose of purifying water.
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