Fluorination of neodymium carbonate monohydrate with anhydrous hydrogen fluoride in a Carberry spinning-basket reactor

Abstract

Neodymium trifluoride is used in the production of neodymium–iron–boron magnets and can be produced by the direct fluorination of neodymium carbonate monohydrate, Nd₂(CO₃)₃·H₂O, using anhydrous hydrogen fluoride, AHF. This reaction was studied in a Carberry spinning-basket reactor in order to minimise the effects of external mass transfer on the reaction kinetics, in the temperature range 100 °C to 250 °C, and at AHF concentrations up to 10 mass%. Since the monohydrate undergoes thermal decomposition, simultaneous competing reactions may take place during fluorination. There is strong evidence for the formation of partially fluorinated intermediate products. The kinetics adheres to a reaction-rate controlled, shrinking-core, heterogeneous reaction model, applicable to the individual particles comprising the pressed Nd₂(CO₃)₃·H₂O pellets used for the work. The rate is independent of temperature, and directly proportional to the AHF concentration. At 10 mass% AHF, the reaction time is 26 ± 3 min. The low operational temperature has significant techno-economic implications, lowering operating cost and costs associated with materials of construction.