Abstract

Various rare earth phosphates [rare earth elements: R = La, Ce, Pr, Nd, Sm, Yb, and Y; phosphates: Monazite-type, Xenotime-type, Rhabdophane-type, and Weinshenkite-type orthophosphates RPO₄, polyphosphate R(PO₃)₃, and ultraphosphate RP₅O₁₄] were synthesized by heating the mixtures of each rare earth oxide and diammonium hydrogenphosphate or phosphoric acid. The compositions of rare earth phosphates were determined by XRD, FT-IR, and TG–DTA. Catalytic properties were studied as one of properties of various rare earth phosphates. Specific surface areas of samples were measured by the BET method. Acid strengths and amounts of acidic sites were measured using several indicators by n-butylamine titration. Acidic properties were also confirmed by adsorption of ammonia. Various rare earth phosphates were characterized by catalytic activities on dehydration reaction of 2-propanol, cracking/dehydrogenation reaction of cumene, and isomerization reaction of butene. The characterization of catalysts was discussed with regard to type of rare earth elements, type of phosphates, and type of phosphorus resources.