| http://www.w3.org/ns/prov#value | - m, neodymium, praseodymium, dysprosium, samarium, yttrium, gadolinium, erbium, ytterbium, holmium, terbium, europium, thulium, and lutetium, with the proviso that the catalyst is substantially free of iron, copper, and manganese, and with the further proviso that when cerium is present, the catalyst further comprises at least one more rare earth element other than cerium, and (b) recycling ethylen
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