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ISSN 2522-1841 (Online) AZ9RBAYCAN KIMYA JURNALI № 4 2018 25
ISSN 0005-2531 (Print)
UDK 546(656.87.21.22)
X-RAY STUDY OF BINARY VANADIUM OXIDE (W-V-O, SN-V-O AND MO-V-O) SYSTEMS
M.I.Aliyeva, V.L.Bagiev, E.F.Ismayilova-Orujeva*, V.A.Gasymov*
Azerbaijan State Oil and Industry University institute of Catalysis and Inorganic Chemistry, NAS of Azerbaijan
vagif_bagiev@yahoo. com, v-gasymov@rambler. ru
Received 13.12.2017
X-ray studies of binary vanadium-containing catalysts were carried out. The results of the investigations showed that in the W-V-O system three phases are formed, two modifications of WO3 and one V2O5. Based on the analysis of diffraction patterns, it was found that in all samples of the Sn-V-O system are observed the phases of SnO2 and V2O5 oxides. It is found that in the Mo-V-O system, in addition to MoO3 and V2O5 oxides, various ternary compounds and solid solutions with the general formula MomV„Op are formed.
Keywords: X-ray phase analysis, binary catalysts, tungsten oxide, solid solutions, chemical compounds.
Introduction
In previous works, we studied the oxidation of propylene on a number of binary vanadium-containing catalysts [1-3]. It was shown that the main product of the reaction of propylene oxidation over studied catalysts is acetic acid and the by-products are carbon dioxide, acetone and acetaldehyde. It is established that the yields of reaction products strongly depend on both the temperature and the composition of vanadium-containing catalysts. This may be due to a change in the phase composition of binary vanadium catalysts. In this connection, in our work, we carried out an X-ray diffraction study of binary vanadium-containing catalysts.
Experimental part
Vanadium oxide catalysts were prepared by mixing aqueous solutions of ammonium me-tavanadate and ammonium tungstate, ammonium molybdate and tin tetrachloride. Obtained mixture was evaporated and dried at a temperature of 1000C, after which it was transferred to a porcelain dish, and calcined at a temperature of 200-300°C until complete separation of the nitrogen oxides. The catalyst then was calcined at 5500C during 10 hours.
X-ray studies were carried out on an automatic powder diffractometer "D2 Phaser" "Bruker" (CuKa-radiation, Ni-filter, 3<29>800).
We investigated W-V-O, Sn-V-O and Mo-V-O catalysts prepared in various ratios of
components satisfying the following conditions: mA/nB, where A - W, Sn, Mo; B - V, m, n = 1 ^ 9, m + n = 10.
Thus, 9 samples were examined in each catalytic system.
Results and discussion
The results of X-ray studies show that three phases are formed in the W-V-O system: two modifications of WO3 and one V2O5, the crystallographic characteristics of which are presented in the Table 1. As can be seen from Table 1, WO3-I differs from WO3-2 in that they have different symmetries and one of the parameters of the unit cell is twice that of the other, i.e. c2=2c1. The consequence of this is the difference in the diffraction patterns of these modifications. Figure 1 shows the diffraction patterns of all nine collected ratios of W/V. At the beginning and at the end of these diffraction patterns also represented oxides of WO3 and V2O5. X-ray analysis shows that all samples consist of three phases and in all the percentage of components is preserved, which is indicated by a regular change in the intensities of reflexes in diffraction pictures.
Analysis and interpretation of diffraction patterns in the Sn-V-O system showed that in all ratios (mSn/nV) the samples consist of two phases, namely SnO2 and V2O5. Figure 2 shows the X-ray patterns of all nine collected ratios (mSn/nV).
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X-RAY STUDY OF BINARY VANADIUM OXIDE.
Table 1. Crystallographic characteristics of the phases formed in the W-V-O, Sn-V-O and Mo-V-O systems
Compound Shingonia Spatial group Lattice parameters Z Number of molecules Literature
a, Â b, Â c, Â Angle,°
WO3-1 rhombic primitive 7.384 7.512 3.846 - 4 |4|
WO3-2 rhombic P2¡/n 7.306 7.540 7.692 90.88 8 |5|
V2O5 rhombic Pmnm 11.510 4.369 3.563 - 3 |6|
SnO2 rhombic Pnnm 4.708 4.720 3.195 - 2 |7|
MoO3 rhombic Pnma 13.825 3.694 3.954 - 4 |8|
MoV2O8 monoclinic C2 19.398 3.629 4.117 144.9 2 |9|
M02.4V3.6O16 monoclinic C2 19.361 3.625 4.121 90.62 1 |10|
Mo4V;O25 rhombic - 11.99 6.72 8.18 - - 1111
(Moo.88Vo.12)O2.94 hexagonal P63 10.593 - 3.694 - 6 1121
(Mo0.08V0.92)2O5 rhombic Pmmn 11.574 3.578 4.332 - 2 |13|
Fig. 1. Diffraction patterns of tungsten and vanadium oxides, as well as all nine W-V-O catalysts: I - (W/V=1/9), II - (W/V=2/8), III - (W/V=3/7), IV - (W/V=4/6), V - (W/V=5/5), VI - (W/V=6/4), VII - (W/V=7/3), VIII -(W/V=8/2), IX - (W/V=9/1).
2Theis (Coupled TwoTheta/Theta) WL-1 &4060
Fig.2. Diffraction patterns of tin and vanadium oxides, as well as all nine Sn-V-O catalysts: I - (Sn/V=1/9), II - (Sn/V=2/8), III - (Sn/V=3/7), IV - Sn/V=4/6), V - (Sn/V=5/5), VI - (Sn/V=6/4),VII - (Sn/V=7/3), VIII -(Sn/V=8/2), IX - (Sn/V=9/1).
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Fig.3. Diffraction patterns of molybdenum and vanadium oxides, as well as all nine Mo-V-O catalysts: I - (Mo/V=1/9), II - (Mo/V=2/8), III - (Mo/V=3/7), IV - Mo/V=4/6), V - (Mo/V=5/5), VI -(Mo/V=6/4),VII - (Mo/V=7/3), VIII - (Mo/V=8/2), IX - (Mo/V=9/1).
For the comparative analysis, at the beginning and at the end of these diffraction patterns, X-ray diffraction patterns of SnO2 and V2O5 are also presented. X-ray analysis shows that all samples consist of two phases, namely SnO2 and V2O5. In all samples, the percentage of components is preserved, as indicated by a regular change in the intensities of the reflexes in the diffraction pictures.
X-ray diffraction studies of the Mo-V-O system showed that, in addition to the MoO3 and V2O5 oxides, various ternary compounds based on Mo-V-O with the general formula MomVnOp are also formed, the crystallographic characteristics of the obtained phases are given in Table 1.
Figure 3 shows the diffraction patterns of all nine collected ratios (mMo/nV). At the beginning and at the end of these diffraction patterns are also X-ray patterns of MoO3 and V2O5.
Interpretation of the obtained results shows that at the ratios of 1Mo/9V, 2Mo/8V, 3Mo/7V,
Table 2. Phases formed in the Mo-V-O system
8Mo/V and 9Mo/V, three phases are formed, namely MoO3, V2O5 and Mo2.4V3.6O16. And with the ratios of components 4Mo/6V, 5Mo/5V and 6Mo/4V in addition to molybdenum and vanadium oxides, other phases with different compositions of the Mo-V-O system formed.
We also calculated the degree of crystal-linity of all prepared catalysts, the results of which are presented in Table 3. As can be seen from Table 3, the crystallinity of W-V-O and Mo-V-O systems does not practically change with the change of the composition, while for Sn-V-O systems the crystallinity decreases from 79.2% on the sample 1Sn-9V to 62% on the sample 9Sn-1V.
Thus, based on the X-ray investigations we conclude that the W-V-O system consists of three phases (two WO3 modifications and one V2O5), Sn-V-O oxide system consists of two phases (SnO2 and V2O5) and Mo-V-O system consists of MoO3, V2O5 phase and various polymolybdates.
Ratio of components, Mo/V Formed phases
1/9 MoO3, V2O5, Mo2.4V3.6O16
2/8 MoO3, V2O5, Mo2 4V3 6O16
3/7 MoO3, V2O5, Mo2.4V3.6O16
4/6 MoO3, V2O5, Mo, V2O8, (Mo0.86V0,12)O2,94, Mo4V6S25
5/5 MoO3, V2O5, Mo2.4V3.6O16, (Mo0.08V0.92)2O5
6/4 MoOs, V2O5, Mo2.4V3.6O16, (Mo0.88V0.12)O2.94
7/3 MoO3 V2O5, Mo24V36O16
8/2 MoO3, V2O5, Mo24V36O16
9/1 MoO3, V2O5, Mo2 4V3 6O16
28 X-RAY STUDY OF BINARY VANADIUM OXIDE
Table 3. Crystallinity of the samples in the systems W-V-O. Sn-V-O and Mo-V-O
Catalytic system W-V-O to W/V Crystallinity. % Catalytic system Sn-V-O to Sn/V Crystallinity. % Catalytic system Mо-V-O to Mo/V Crystallinity. %
1/9 77.7 1/9 79.2 1/9 82.6
2/8 78.9 2/8 74.5 2/8 78.3
3/7 80.0 3/7 76.5 3/7 79.6
4/6 80.2 4/6 74.9 4/6 75.7
5/5 79.8 5/5 73.8 5/5 80.5
6/4 80.5 6/4 72.1 6/4 77.5
7/3 79.2 7/3 70.4 7/3 81.0
8/2 80.9 8/2 63.5 8/2 77.6
9/1 80.6 9/1 62.0 9/1 77.9
References
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BINAR W-V-O, Sn-V-O VO Mo-V-O SISTEMLORININ RENTGENFAZA TODQIQI
M.i.0liyeva, V.L.Bagiyev, E.F.Ismayilova Orucova, V.O.Qasimov
Vanadiumlu binar katalizatorlarin rentgenoqrafik tadqiqati apanlmi§dir. Tadqiqatlarin naticalari W-V-O sisteminda WO3-ün iki modifikasiyasinin va V2O5 amala galdiyini gostarmi§dir. Sn-V-O sisteminin difraksiya manzaralarinin analizi bütün nümunalarda SnO2 va V2O5 amala galdiyi malum olmu§dur. Mo-V-O sisteminda isa MoO3 va V2O5-dan alava ümumi formulu MomVnOp olan üglü birla§malar va bark mahlullarin amala galdiyi müayyanla§dirilmi§dir.
Agar sozlar: rentgenfaza analizi, binar katalizatorlar, volfram oksidi, bark mahlullar, kimyavi birla§malar.
РЕНТГЕНОГРАФИЧЕСКОЕ ИССЛЕДОВАНИЕ БИНАРНЫХ W-V-O, Sn-V-O И Mo-V-O СИСТЕМ
М.И.Алиева, В.Л.Багиев, Э.Ф.Исмайлова Оруджева, В.А.Гасымов
Проведены рентгенографические исследования бинарных ванадийсодержащих катализаторов. Результаты исследований показали, что в системе W-V-O образуются три фазы: две модификации WO3 и одна V205. На основании анализа дифракционных картин найдено, что в системе Sn-V-O во всех образцах наблюдаются фазы оксидов SnO2 и V2O5. Установлено, что в системе Mo-V-O, кроме оксидов MoO3 и V2O5, образуются также различные тройные соединения и твердые растворы общей формулы MomVnOp.
Ключевые слова: рентгенофазовый анализ, бинарные катализаторы, оксид вольфрама, твердые растворы, химические соединения.
AЗЕPБAЙДЖAHСКИЙ ХИМИЧЕСКИЙ ЖУРНАЛ № 4 2018
