Thermochimica Acta 484 (2009) 77–81
Thermochimica Acta
Short communication
Kinetic analysis of dechlorination and oxidation of PrOCl by using
a non-isothermal TG methodଝ
H.C. Yang∗, H.C. Eun, Y.Z. Cho, H.S. Lee, I.T. Kim
Nuclear Fuel Cycle R&D Department, Korea Atomic Energy Research Institute, P.O. Box 150 Yuseong, Daejeon 305-353, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Thermal dechlorination and oxidation process of praseodymium oxychloride, PrOCl, was studied from the
view point of reaction kinetics. On the basis of data of thermogravimetry under different oxygen partial
pressures at various heating rates, a kinetic analysis was performed using an isoconversional method and
a master plot method. The results of the isoconversional method of TG data suggested that the dechlo-
rination and oxidation of PrOCl followed a single step with activation energy of 112.6 3.4 kJ mol−1, and
from master plot methods, the reaction was described by a linear-contracting phase boundary reaction.
© 2008 Elsevier B.V. All rights reserved.
Received 28 July 2008
Received in revised form
21 November 2008
Accepted 26 November 2008
Available online 3 December 2008
Keywords:
Praseodymium oxychloride
Thermal dechlorination
Oxidation
Kinetic model
1. Introduction
of PrOCl have not been reported in the literature as yet. A non-
isothermal TG study has an advantage in that a wide range of
Praseodymium oxide, also called praseodymia, is used as an
ingredient of color glasses and enamels. As an important addi-
tive, praseodymium oxide is used as a yellow pigment in photonic
applications. Glass containing praseodymium oxide is used to man-
ufacture didymium glass, which is a colorant for welder’s goggles.
A thin praseodymium oxide film is widely used in the sensor, semi-
conducting, and ceramic industries. An increased industrial use of
pure praseodymium and its oxide requires more advanced separa-
tion technologies.
temperatures are covered with a single experiment [7–9]. This
study investigated the kinetics of a thermal dechlorination and
oxidation of PrOCl by using a non-isothermal TG method. The objec-
tives of this study were to establish a detailed kinetic model and the
kinetic parameters of the dechlorination and oxidation reaction of
PrOCl under high-temperature oxidizing atmospheres. The results
of this study will be used to determine the operating conditions for
a thermal treatment furnace for the dechlorination and oxidation
of PrOCl.
An electrochemical separation and an electrochemical synthesis
in molten chloride salts are promising technologies for obtaining
pure metals and oxides of rare earth elements [1–4]. By-products
of these electrochemical processes include rare earth oxychlorides
(REOCl). Pure RE oxides are obtained by a thermal treatment of the
RE oxychlorides to emit gaseous chlorines in the presence of oxygen
as:
2. Experimental methods
2.1. Synthesis and analysis of PrOCl and its thermal oxidation
products
Powdered PrOCl was synthesized in LiCl–KCl eutectic molten
salt. The experimental apparatus for synthesizing the PrOCl is found
elsewhere [5,6]. Anhydrous PrCl3 with a purity of 99.99% was
premixed with a LiCl–KCl solid salt with a purity of 99.9% (LiCl:
44.2 wt.%, eutectic point: 633 K) in an alumina crucible. The crucible
containing the mixture was heated up to 723 K in a stainless-steel
column and oxygen was sparged into it from the bottom. After a
10-h oxygen sparging, the mixture of the precipitate was sampled
and dissolved in distilled water. A pure sample powder of PrOCl
was then obtained by a vacuum filtration. SEM (Leo 1455VP; KBSI)
photographs of the obtained PrOCl powder and its thermal oxida-
tion product, PrO2 powder, are shown in Fig. 1. Speciation of the
REOCl + 1/2O2(g) = REO2 + 1/2Cl2(g)
Kinetic studies of the above reaction for GdOCl and NdOCl
were performed by using a non-isothermal thermogravimetric (TG)
method [5,6]. Detailed kinetics of a dechlorination and oxidation
ଝ
This paper was presented at 8th Symposium of the Korean Society of
Thermophysical Properties held at POSTECH, Korea from April 24–25, 2008.
∗
Corresponding author. Tel.: +82 42 868 2575; fax: +82 42 868 2329.
0040-6031/$ – see front matter © 2008 Elsevier B.V. All rights reserved.