Formation and catalytic characterization of various rare earth phosphates

TLDR

The work investigates how the choice of rare earth element and phosphate type influences catalytic behavior, considering various phosphorus resources. The authors synthesized a series of rare earth phosphates (La, Ce, Pr, Nd, Sm, Yb, Y) by heating rare earth oxides with diammonium hydrogenphosphate or phosphoric acid, then characterized their composition by XRD, FT‑IR, TG–DTA, measured surface area by BET, acidity by n‑butylamine titration and ammonia adsorption, and evaluated catalytic activity in 2‑propanol dehydration, cumene cracking/dehydrogenation, and butene isomerization.

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.