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Mineral Processing and Extractive Metallurgy
Transactions of the Institutions of Mining and Metallurgy: Section C
ISSN: 0371-9553 (Print) 1743-2855 (Online) Journal homepage: http://www.tandfonline.com/loi/ympm20
Investigation on ammonium perrhenate
behaviour in nitrogen, argon and hydrogen
atmosphere as a part of rhenium extraction
process
Shaya Sharif Javaherian, Hossein Aghajani & Hamed Tavakoli
To cite this article: Shaya Sharif Javaherian, Hossein Aghajani & Hamed Tavakoli (2017):
Investigation on ammonium perrhenate behaviour in nitrogen, argon and hydrogen atmosphere as
a part of rhenium extraction process, Mineral Processing and Extractive Metallurgy
To link to this article: http://dx.doi.org/10.1080/03719553.2017.1375707
Published online: 18 Sep 2017.
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Date: 28 October 2017, At: 04:42
MINERAL PROCESSING AND EXTRACTIVE METALLURGY, 2017
https://doi.org/10.1080/03719553.2017.1375707
Investigation on ammonium perrhenate behaviour in nitrogen, argon and
hydrogen atmosphere as a part of rhenium extraction process
Shaya Sharif Javaherian
a
, Hossein Aghajani
a
and Hamed Tavakoli
b
Department of Materials Engineering, University of Tabriz, Tabriz, Iran; bFaculty of Materials and Metallurgical Engineering, Iran University
of Science and Technology, Tehran, Iran
Downloaded by [University of Florida] at 04:42 28 October 2017
a
ABSTRACT
ARTICLE HISTORY
Ammonium perrhenate (APR) is an intermediate product in rhenium extraction process, by
which it is possible to produce rhenium powder. The main purpose of this research is to
investigate the behaviour of APR in different atmospheres as a part of reduction process. In
this research, differential thermal analysis and thermo gravimetric analysis are used to peruse
the APR behaviour in nitrogen, argon and hydrogen atmospheres. Also for further validation,
X-ray diffraction analysis and the scanning electron microscopy were used. The results
indicate that APR behaves almost the same in the argon and nitrogen atmospheres. In these
conditions, APR decomposes to rhenium oxides during thermal decomposition. However,
APR in hydrogen reductive atmosphere is reduced to pure rhenium powder without any
reactions. SEM images showed that hydrogen reduced APR had a spherical morphology, but
on the other hand the directly reduced rhenium powder in hydrogen atmosphere showed
flake morphology.
Received 21 October 2016
Accepted 31 August 2017
Introduction
Rhenium is a refractory metal which melts at 3180°C,
exceeded only by tungsten among metals. It is also
widely known for its high-elasticity modulus and its
withstanding alternative thermal cycles without any
damage. It also shows no ductile to brittle transmission
and its ductile behaviour remains constant until its
melting point. So, rhenium and its alloys are widely
used in such areas as aerospace, electronics and petro
chemistry (Busby et al. 2007; Lou et al. 2010; Naor
et al. 2010). High-melting point of rhenium leads its
components to be produced by powder metallurgy
techniques. So the preparation of rhenium powder,
which has favourable performance in powder metallurgy industry, has to be concerned (Trybus et al.
2002).
It is well known that ammonium perrhenate (APR)
is the most important initial substance in the production of pure rhenium powder. There are several
methods to produce rhenium from APR but generally,
hydrogen reduction of APR through gas–solid reactions is a common method in preparation of rhenium
powder commercially. Some properties of the rhenium powder produced by these methods such as
morphology, size distribution, tap density and fluidity
has been studied before (Bai et al.; Shen et al.; Schrebler and Cury 2001; Schrebler et al. 2001; Mnnheim
and Garin 2003; Stefan and Helmut 2007; Naor
et al. 2009).
CONTACT Hossein Aghajani
KEYWORDS
Rhenium; rhenium dioxide;
rhenium heptoxide;
ammonium perrhenate;
hydrogen reduction;
extraction
As mentioned, hydrogen reduction of APR is a
favourable method in producing pure rhenium powder. Depending on the required particle size and morphology, the hydrogen reduction of APR could be a
one- or two-step process (Millensifer et al. 2014).
In thermodynamic point of view, hydrogen
reduction of APR can be accomplished based on several reactions. In the one-step process, APR can be
reduced by hydrogen directly based on the reaction
illustrated in Equation (1). Furthermore it would be
possible to achieve rhenium through indirect hydrogen
processes. It is reported that not only would it be possible to thermally decompose APR to rhenium oxides
and then reduce it to rhenium powder (Equations 2
and 3), but also rhenium can be produced by oxidation
of APR to rhenium heptoxide and its reduction by
hydrogen (Equations 4 and 5). There are several
methods which have been published based on these
theories but there are still some aspects that have to
be concerned (Goncharov et al. 1999; Leonharot et al.
2001; Li et al. 2001; Hu et al. 2003; Leonhardt et al.
2003; Jurewicz and Guo 2005).
NH4 ReO4(g) + 3.5H2(g) = Re(s) + NH3(g)
+ 4H2 O(g)
(1)
NH4 ReO4(s) = ReO(s) + 0.5N2(g) + 2H2(g)
(2)
ReO2(s) + 2H2(g) = Re(s) + 2H2 O(g)
(3)
h_aghajani@tabrizu.ac.ir
© 2017 Institute of Materials, Minerals and Mining and The AusIMM Published by Taylor & Francis on behalf of the Institute and The AusIMM
2
S. SHARIF JAVAHERIAN ET AL.
2NH4 ReO4(s) + 1.5O2(g) = Re2 O7(g) + N2(g)
+ 4H2 O(g)
Downloaded by [University of Florida] at 04:42 28 October 2017
Re2 O7(g) + 7H2(g) = 2Re(s) + 7H2 O(g)
(4)
(5)
There are some details about these processes, but
thermodynamics of rhenium reduction is also unclear.
For the two-step rhenium reduction process it has
reported the temperature of the first and second step
is around 300 and 900°C, respectively (Habashi 1997;
Li et al. 2001; Hu et al. 2003). It has been concluded
that in the two-step reduction processes of rhenium
and some other refractory metals which reduce the
same as rhenium such as molybdenum and tungsten,
the first step of the reduction process plays an important role in the properties of the final products (Habashi 1997; Li et al. 2001; Hu et al. 2003).
Although the extraction process of rhenium has
been industrialised in some countries, there are few
details that have been published so far and the process
suffers from lack of details. Therefore, the main idea of
this study is to publish some additional details about
the rhenium production process through the hydrogen
reduction of APR.
Procedure
To investigate the behaviour of APR in the nitrogen,
argon and hydrogen atmosphere the commercially
available APR powder (∼250 µm) was used. Hydrogen,
nitrogen and argon with purity of 99.999% were used
in the experiments and the flow rate was fixed at
40 cc/min during the tests.
The initial APR sample was characterised by XRF
analysis (Table 1). The characterisation of the samples
was performed by X-ray diffraction (XRD) analysis and
scanning electron microscopy (SEM).
In this study, first, the behaviour of APR in hydrogen,
nitrogen and argon atmospheres was studied by thermo
gravimetric analysis (TGA). In each test, around 50–
60 mg of initial material was charged into the alumina
boat of the TGA furnace. Then, according to the TGA
data, favourable reactions were tried to simulate in an
atmosphere control tube furnace. In each run, 3 g of
APR was placed into a quartz boat and charged into
the furnace in a favourable atmosphere. After thermal
treatments, the samples were cooled in the furnace
down to ambient temperature. During the tests heating
rate and also the gas flow were kept constant at
10 cc/min and 40 cc/min respectively. Weight
reduction measurements, X-ray analysis and also scanning electron microscopy (SEM) were used to characterise the final products. At the end, decomposition of
APR in nitrogen and argon atmosphere were compared
with the direct hydrogen reduction of APR and the
effects of the first step atmosphere on the final product
properties were investigated, too.
All the thermodynamic data were extracted from
HSC chemistry version 5.11. TGA analysis was carried
out by Metler Toledo (TGA/SDTA 851e). The nitrogen
gas flow with purity of 99.999% was used in all TGA
experiments as a protective gas with a constant flow
of 40 cc/min.
The high-temperature experiments were held in an
ATRA1200°C tube furnace with constant heating rate
of 10 cc/min. The samples were weighted with a four
digit balance. SEM images were taken by TESCAN
(MIRA3) and the samples were prepared by dispersing
in alcohol.
Results and conclusions
In this study, first the investigation on the behaviour of
ARP in the reductive hydrogen atmosphere would be
discussed. For this aim, TG analysis of APR in hydrogen atmosphere was carried out with a heating rate of
10 ◦ C/min and constant hydrogen flow of 40 cc/min.
TGA result of the sample has been shown in Figure 1.
The weight reduction of the sample was equal to the
stoichiometric weight reduction of production of
Figure 1. Weight reduction of APR in hydrogen atmosphere at
TGA analysis.
Table 1. XRF analysis of the initial APR.
TiO2
0.002%
Pb
1ppm
Rb
16ppm
Re
MgO
K2O
Na2O
CaO
Fe2O3
Al2O3
SiO2
68.71%
Zn
21ppm
Y
2ppm
0.02%
Cu
40ppm
Zr
1ppm
Nb
2ppm
0.04%
Sr
4ppm
W
5ppm
Ga
1ppm
0.02%
Ba
12ppm
La
1ppm
Mo
1ppm
0.21%
Cl
57ppm
Ce
4ppm
Th
5ppm
0.03%
SO3
0.002%
V
2ppm
U
2ppm
0.16%
P2O5
0.001%
Cr
1ppm
As
2ppm
0.22%
MnO
0.001%
Ni
4ppm
Co
4ppm
MINERAL PROCESSING AND EXTRACTIVE METALLURGY
3
pure rhenium approximately. High-negative DG◦ of
the reaction in comparison with other reactions of
Re–H–O–N system also indicates the highest possibility of accomplishing reaction (1). Thermodynamic
data of some important reactions of Re–O–H–N system have been collected in Figure 2 which shows the
most negative belongs to the reaction (1).
NH4 ReO4(s) +3.5H2(g) =Re(s) +NH3(g) +4H2 O(g)
MAPR
= 268.2g mol
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MRe = 186.2g mol
(1)
Stoichiometric ratio
Stoichiometric
weight
reduction
ratio
MRe
mRe
=
= 0.69
MAPR mAPR
mAPR − mRe
× 100 = 31%
mAPR
In order to determine the stable phases and verify
the thermodynamics claims, 3 g of APR was placed
in a quartz boat and set into a tube furnace with hydrogen atmosphere. The prepared sample, which was kept
at 300°C for 1 h with constant hydrogen flow of
40 cc/min and heating rate of 10 ◦ C/min, was
measured and showed 31.04% weight reduction. The
X-ray analysis of the sample (Figure 3) showed a sort
of wide peaks in the same places of the referenced rhenium peaks (PDF2 No. 00-005-0702). It is reported
that the wide rhenium diffraction pattern in the direct
reduction process was due to dissolution of oxygen,
nitrogen and hydrogen gaseous atoms in the final product (Mannheim and Garin 2003). The dissolution
causes a lattice strain in the crystalline structure of
the final product which would weaken the intensity
and increase the width of XRD peaks. It has also
been reported that at higher temperatures the amount
of dissolved gaseous atoms and so the lattice strain in
the crystalline structure would decrease.
Figure 2. Thermodynamic data of Re–O–H–N system reactions.
Figure 3. XRD of APR reduced at 300°C in hydrogen
atmosphere.
The thermal treatment of the sample at hydrogen
atmosphere continued for another 1 h at 900°C to
investigate the dependence of rhenium diffraction pattern on the temperature of thermal treatment step. The
XRD analysis of the rhenium powder produced by
direct hydrogen reduction of APR, which was kept
for 1 h at 300°C and 1 h at 900°C, has been shown in
Figure 4. Accordingly, in comparison with the rhenium
diffraction pattern reduced at 300°C (Figure 3) the diffraction peaks became sharper and it could be the result
of releasing crystalline structure strain of the final product at higher reduction temperature.
On the other hand, the wide peaks of the rhenium
reduced at 300°C could be a result of the low crystallisation kinetics of rhenium, directly produced from
APR at this temperature. The reduction at higher
temperatures shows that the reduction kinetic increases
at higher temperatures which could lead to full crystalline structure of rhenium. The claim needs to be verified through a kinetic study. Also, the sharp peaks of
4
S. SHARIF JAVAHERIAN ET AL.
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Figure 4. XRD pattern of rhenium powder produced at 900°C
in hydrogen atmosphere.
rhenium reduced at 900°C could be a result of grain
growth of fine rhenium powder produced at 300°C.
SEM images of the rhenium powder produced at
300°C are shown in Figure 5. The images show that
the rhenium powders produced by direct hydrogen
reduction have porous and flaky shapes. Figure 5(a)
shows the porous particles of rhenium reduced at
300°C. According to the previous claims, the tendency
of the gaseous atoms to leave the initial APR would
possibly result in the porous shape of final particles.
Figure 5(b) shows some blebs remained on the particles
surface which could be due to the gaseous atoms tendency of leaving the particles at 300°C. In these images
the particles do not contain any flaky shapes but in
Figure 5(c) which shows the image of rhenium directly
reduced at 900, the flaky shape of the rhenium can be
observed. It could be said that the porosity of particles
increases at higher temperatures and the particles
obtain flaky shapes because of high porosity (Figure 5
(c)). In other words, higher rate of leaving gaseous
atoms at higher temperature causes higher porosity
and probably such explosions in particles which
make them flaky.
To survey the behaviour of APR in nitrogen and
argon atmosphere TG analysis was done in both
atmospheres. Figure 6 shows the TGA-DTA analysis
of APR in nitrogen atmosphere. Nitrogen atmosphere
with constant flow of 40 and a heating rate of
10 ◦ C/min was the atmosphere condition of the
Figure 5. SEM images of the rhenium reduced at (a) 300°C with magnification of 260× (b) 300°C with magnification of 1.49kx (c)
900°C with magnification of 1kx and (d) 900°C with magnification of 2.5kx.
MINERAL PROCESSING AND EXTRACTIVE METALLURGY
5
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Figure 6. TG-DTA analysis of the APR in nitrogen atmosphere with constant flow of 40 cc/min and a heating rate of 10 °C/min.
Figure 7. TG-DTA analysis of APR in argon atmosphere with constant flow of 40 cc/min and a heating rate of 10 °C/min.
analysis. As can be witnessed, the sample showed a
two-step weight reduction while the temperature was
increasing. The DTA analysis of the sample shows
that the first weight reduction is due to an endothermic
reaction which was followed by an exothermic one.
Thermodynamic data of APR decomposition indicate
that in Re–O–N–H system there can be only one
exothermic reaction that can thermodynamically take
place at this temperature. The reaction belongs to the
decomposition of APR to ReO2 (Equation 2). Other
decomposition reactions of APR such as decomposition to Re2O7, ReO3 or Re (Equations 6–8) have
either positive Gibbs free energy or positive enthalpy
around 400°C (Figure 2).
NH4 ReO4(s) = Re(s) + 0.5N2(g) + 2H2 O(g)
+ O2(g)
(8)
NH4 ReO4(s) = 0.5Re2 O7(g) + NH3(g)
+ 0.5H2 O(g)
(6)
NH4 ReO4(s) = ReO3(s) + NH3(g) + 0.5H2 O(g)
+ 0.25O2(g)
(7)
Figure 8. XRD pattern of APR, decomposed for 1 h in argon
atmosphere with a constant flow of 40 cc/min and heating
rate of 10 °C/min.
6
S. SHARIF JAVAHERIAN ET AL.
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Figure 9. XRD pattern of the Re reduced from ReO2 in hydrogen atmosphere with a constant flow of 40 cc/min and heating
rate of 10 °C/min.
Thermodynamic data also show that the second
peak in the DTA analysis can belong to either
equations (8) or (9) due to their high-negative Gibbs
free energy and high levels of negative enthalpy. As it
seems, the activation of the second reaction follows
the endothermic one and it can be claimed that the
exothermic reaction was activated when the products
of endothermic reaction were produced and so the
second reaction is more possibly the oxidation of rhenium dioxide to rhenium heptoxide. It should be noted
that the oxygen in the reactions (4) and (9) can be prepared by the impurities of the protective gas.
◦
NH4 ReO4(s) + 0.75O2(g) = 0.5Re2 O7(g) + 0.5N2(g) + 2H2 O(g) DH400 = −140.113KJ (4)
2ReO2(s) + 1.5O2(g) = Re2 O7(g)
◦
DH400 = −152.399KJ (9)
The behaviour of APR in argon atmosphere was also
investigated through another TG-DTA analysis with the
same condition as TG-DTA analysis in nitrogen atmosphere. The weight reduction manner of the sample was
the same as the nitrogen atmosphere. As shown in
Figures 7 and 8, both samples weight at the first step
was reduced by 14%, followed by another 20% of weight
reduction. But it should be noticed that the starting
temperature of the reaction was 20° higher in nitrogen
atmosphere compared to the argon atmosphere. Also
at higher temperatures, APR showed 5% higher weight
reduction in nitrogen atmosphere.
Considering these TG analyses, around 3gr of initial
APR were put into a quartz boat and then kept for 1 h
in argon atmosphere with a constant flow of 40 cc/min
and heating rate of 10 ◦ C/min. The sample showed
17.26% of weight reduction which is approximately
equal to stoichiometric weight reduction in decomposition of APR to ReO2 according to reaction (4).
NH4 ReO4(s) = ReO2(s) + 0.5N2(g) + 2H2(g)
MAPR = 268.2g mol Stoichiometric ratio
(2)
Stoichiometric weight
reduction ratio
MReO2 mReO2
mAPR − mReO2
=
= 0.81
× 100 = 18.6%
MReO2 = 218.2g mol
MAPR
mAPR
mAPR
It is obvious that the difference between the weight
reduction of the sample (17.26%) and the stoichiometric amount of APR decomposition to ReO2
(18.6%) is due to the second reaction known in the
DTA analysis. But the X-ray analysis of the sample
showed a ReO2 single phase (MoO2 Type) as the process product (Figure 8). It should be noted that the
temperature of the second reaction, which produces
rhenium heptoxide, is higher than the boiling temperature of Re2O7 (360°C) and so it possibly evaporates
after formation. No existence of any other phases in
Figure 10. Morphology of the two-step reduced rhenium powder (a) with magnification of 5kx (b) with magnification of 30kx.
MINERAL PROCESSING AND EXTRACTIVE METALLURGY
the X-ray pattern except ReO2, could be a proof of the
claim.
The ReO2 produced in decomposition process of APR
in argon atmosphere was hold for 1 h in the reductive
atmosphere of hydrogen to produce pure rhenium powder through reaction (10). The heating rate and the
hydrogen flow were 10 cc/min and 40 °C/min, respectively. X-ray analysis of the product showed sharp peaks
of rhenium without any impure phases (Figure 9). Also
the weight reduction was 14.6% equal to the stoichiometric amount of reduction of ReO2 through the reaction
(3). So it can be claimed that the reduction of ReO2 by
hydrogen was completely done in the last step.
ReO2(s) + 2H2(g) = Re(s) + 2H2 O(g)
MReO2 = 268.2g molStoichiometric ratio
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MRe = 186.2g mol
(3)
Stoichiometric weight
reduction ratio
MRe
mRe
mReO2 − mRe
=
= 0.85
× 100 = 14.6%
MReO2 mReO2
mReO2
The morphology of the two-step reduced rhenium
powder can be seen in Figure 10. Rhenium particles
are fine and in polygonal shape which would be more
appropriate in powder metallurgy applications than
the flaky shape.
Conclusion
In this paper the differences between two common
methods to reduce APR were investigated. It was
shown that APR can directly reduce in hydrogen
atmosphere but the morphology of final product
would be in a porous and flaky shape. Additionally, it
was also shown that APR can be reduced in an indirect
process which produces ReO2 as a semi product. In the
indirect process the final rhenium powder particles
would be finer and the morphology would be polygonal
that are more appropriate for further powder metallurgy applications.
Disclosure statement
No potential conflict of interest was reported by the authors.
ORCID
Shaya Sharif Javaherian http://orcid.org/0000-0001-82511290
Hossein Aghajani http://orcid.org/0000-0001-8251-1290
Hamed Tavakoli http://orcid.org/0000-0003-2329-514X
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