With the rare-earth complex catalyst, the catalytic converter can reach Euro3 and Euro4 emission standard, and reduce cost. Brief introduction1.The rare-earth elements (REE) are the elements Sc (scandium) Y (yttrium) and the 15 lanthanide elements with atomic numbers 57 through 71, namely, La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium ...