Synthesis of novel orthorhombic Mo and v based complex oxides coordinating alkylammonium cation in its heptagonal channel and their application as a catalyst

Article abstract of DOI:10.1021/cm400239c

The effects of several alkylammonium cations on the synthesis of orthorhombic Mo₃VO_11.2 complex oxides (MoVO) were investigated. First, we synthesized various alkylammonium isopolymolybdates as precursors for the synthesis of MoVO. Methylammonium heptamolybdate, dimethylammonium trimolybdate, ethylammonium trimolybdate, and ethylenediammonium trimolybdate were obtained as pure materials in new crystalline structures. Orthorhombic MoVO complex oxides were synthesized under hydrothermal conditions when (CH₃NH₃)₆Mo ₇O₂₄ and ((CH₃)₂NH₂) ₂Mo₃O₁₀·H₂O were used. It was found for the first case that methylammonium cations and dimethylammonium cations were incorporated into the orthorhombic MoVO structure, forming compounds of Mo_32.3V_7.7O₁₁₂(CH ₃NH₃)_4.0·9.7H₂O and Mo _30.2V_9.8O₁₁₂((CH₃) ₂NH₂)_2.5·8.5H₂O, respectively. These alkylammonium cations play an important role as a stabilizer in the synthesis of MoVO and act as a structure-directing agent for the orthorhombic phase.

Full text of DOI:10.1021/cm400239c

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Article
Synthesis of novel orthorhombic Mo and V based
complex oxides coordinating alkylammonium cation in
its heptagonal channel and their application as a catalyst
Satoshi Ishikawa, Toru Murayama, Shunpei Omura, Masahiro Sadakane, and Wataru Ueda
Chem. Mater., Just Accepted Manuscript • DOI: 10.1021/cm400239c • Publication Date (Web): 02 May 2013
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Chemistry of Materials
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Synthesis of novel orthorhombic Mo and V based complex oxides
coordinating alkylammonium cation in its heptagonal channel and
their application as a catalyst
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Satoshi Ishikawaa), Toru Murayama a)*, Shunpei Ohmura a), Masahiro Sadakane b), Wataru Ueda
*
a)
a) Catalysis Research Center, Hokkaido University, N-21, W-10, Sapporo, 001-0021, Japan
b) Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, 1-4-
1 Kagamiyama, Higashi-Hiroshima, 739-8527, Japan
E-mail: ueda@cat.hokudai.ac.jp, murayama@cat.hokudai.ac.jp.
Mo-V-O complex oxide, alkylammonium isopolymolybdate, orthorhombic structure, selective oxidation of ethane.
ABSTRACT: The effects of several alkylammonium cations on the synthesis of orthorhombic Mo3VO11.2 complex oxides
(MoVO) were investigated. First, we synthesized various alkylammonium isopolymolybdates as precursors for the synthe-
sis of MoVO. Methylammonium heptamolybdate, dimethylammonium trimolybdate, ethylammonium trimolybdate and
ethylenediammonium trimolybdate were obtained as pure materials in new crystalline structures. Orthorhombic MoVO
complex oxides were synthesized under hydrothermal conditions when (CH3NH3)6Mo7O24 and ((CH3)2NH2)2Mo3O10∙H2O
were used. It was found for the first case that methylammonium cations and dimethylammonium cations were incorpo-
rated into the orthorhombic MoVO structure, forming compounds of Mo32.3V7.7O112(CH3NH3)4.0∙9.7H2O and
Mo30.2V9.8O112((CH3)2NH2)2.5∙8.5H2O, respectively. These alkylammonium cations play an important role as a stabilizer in
the synthesis of MoVO and act like as a structure-directing agent for the orthorhombic phase.
KEYWORDS: Mo-V-O complex oxide, alkylammonium isopolymolybdate, orthorhombic structure, selective oxidation of
ethane.
INTRODUCTION
Mo–V–M–O (M= Nb, Te, Sb, etc.) complex oxide cata-
lysts have attracted interest in the selective oxidation and
the ammoxidation of light alkanes [1-16]. We have recent-
ly reported a hydrothermal synthesis method for prepar-
ing single phase Mo and V based complex metal oxides
(MoVO) with orthorhombic structure and successfully
demonstrated the roles of the elements of the catalysts in
the catalysis [17-20]. The orthorhombic MoVO is a layered
Fig. 1 Structure model of orthorhombic MoVO complex
oxide and ammonium cation: a-b plane (a) and image of
heptagonal channel (b). (green: pentagonal {Mo6O21} unit,
light blue: Mo or V octahedral, red: oxygen, blue: nitrogen
and white: hydrogen)
structure with slabs with 4.0 Å d-spacing and the slabs
stack each other with anisotropically growing along the
c−axis to form a rod crystal. The a-b plane of the ortho-
rhombic MoVO is composed by the arrangement of the
pentagonal {Mo6O21} units and MO6 (M = Mo, V) octahe-
dra with the formation of hexagonal and heptagonal ring
channels [21-25].
treatment at 673K in air or under N2 flow without collapse
of the crystalline structure and with formation of
Brønsted acid sites which may relate to the catalytic activ-
ity of MoVO. The ammonium cation is not only for
charge compensation but also regarded as a structure-
directing agent like in the synthesis of aluminosilicates.
This suggests that alkylammonium cations with different
molecular size have effects on the crystallization of Mo-
VO and on crystalline state as structure-directing agents.
We proposed that the pentagonal {Mo6O21} unit de-
rived from ammonium heptamolybdate (AHM) is a build-
ing block in the synthesis of the orthorhombic MoVO
under hydrothermal conditions [26-31]. Ammonium ion,
as a counter cation of the Mo precursor, is confined in the
heptagonal channel of MoVO during the crystal growth
(Fig. 1). This ammonium cation can be removed by heat
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Organic structure-directing agents with appropriate
der was washed with 1 L of water and dried in air at 353 K
overnight. These prepared powder were abbreviated as
EDATM (ethylenediammonium trimolybdate),
1,2−PDATM (1,2−propanediammonium trimolybdate), and
1,3−PDATM(1,3−propanediammonium trimolybdate).
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size and shape should be selected for efficient crystalliza-
tion [32-34]. A variety of organic structure-directing
agents have been studied in zeolites [35], mesoporous
oxides of the MCM-41 class [36-37], biomineralized mate-
rials [38], and microporous octahedral–tetrahedral or
square pyramidal–tetrahedral transition metal phosphate
frameworks (TMPO) [39-40]. Although in the case of the
orthorhombic MoVO catalyst the structural space in the
heptagonal channel is 4.0 Å diameter and limits to coun-
ter cations with smaller molecular size like an ammonium
cation with 2.8 Å size, organic structure-directing agents
may afford advantages in the self-assembly process of the
building units to form the crystalline structure.
Preparation
of
MoVO
mixed
oxide.
(NH4)6Mo7O24∙4H2O (Mo: 50 mmol, Wako) or prepared
alkylammonium isopolymolybdate (Mo: 50 mmol) was
dissolved in 120 mL of distilled water. Separately, an
aqueous solution of VOSO4 (Mitsuwa Chemicals) was
prepared by dissolving 12.5 mmol of hydrated VOSO4 in
120 mL distilled water. These two solutions were mixed at
293 K and stirred for 10 min before being introduced into
an autoclave (300 mL Teflon inner tube). After 10 min of
nitrogen bubbling to replace the residual air, hydrother-
mal reaction was carried out at 448 K for 48 hours. Ob-
tained gray solids were washed with distilled water and
dried at 353 K overnight. These solids were purified by
treatment with oxalic acid; dry solids were added to an
aqueous solution of oxalic acid (0.4 M; 25 mL / 1 g solids)
and this mixture was stirred at 333 K for 30 min. Solids
were isolated from the suspension by filtration, washed
with distilled water, and dried at 353 K overnight. Yield of
the catalyst was calculated based on MoO3 and V2O5.
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The synthesis of alkylammonium isoplolymolybdate
has also attracted extensive interest as hybrid organic-
inorganic materials for electron conductivity, magnetism
and photochemistry. There are reports about the synthe-
sis of crystalline alkylammonium isopolymolybdate [41-
45]. A large number of alkylammonium isopolymolyb-
dates have been isolated using secondary and tertiary
amines, whereas only a few alkylammonium isopoly-
molybdates of (di-, tri-) methylamine, ethylamine, prop-
ylamine, ethylenediamine and propyldiamine have been
investigated [references].
Characterizations of catalyst. Powder XRD patterns
were recorded on a diffractometer (RINT Ultima+,
Rigaku) with Cu-Kα radiation. For XRD measurement,
samples were ground and put on a horizontal sample
holder. Diffraction patterns were recorded in 2 theta = 4 –
60˚. Raman spectra (inVia Reflex Raman spectrometer,
RENISHAW) were taken in air on a static sample with Ar
laser powers. Each spectrum was collected for 10 s accu-
mulated once and normalized for comparison. CHN ele-
mental composition was determined using Micro Corder
JM10 (Yanaco). TG analysis was carried out in an air flow
(50 ml min-1) by using TG8120 (Rigaku). The sample (ca.
0.01 g) was placed on a sample pan and the temperature
was raised at a rate of 10 K min-1. FT-IR analysis was car-
ried out using a spectrometer (FT/IR-660, JASCO) with a
MCT detector. IR spectra were obtained by integration of
more than 256 scans with a resolution of 4 cm-1. X-ray
photoelectron spectroscopy (XPS) measurements were
carried out using JPS-9010MC spectrometer (JEOL) with
Al irradiation and monochromator. ICP−AES was carried
out with a VISTA−PRO apparatus (Varian). N2 adsorption
was performed at 77 K in a gas adsorption analyzer
(BELSORP-max; BELJAPAN, Inc. Japan). The measure-
ments were performed at relative pressures from 10-8 to 1.0
in an incremental dose mode. Prior to the adsorption
measurements, samples were outgassed at 573 K under
vacuum for 2h. Pore volume and external surface area
were calculated by t-plot method in the t-range from 0.15
to 0.90. TPD was carried out using a BELSORP apparatus.
The measurement procedure is as follows: 50 mg of sam-
ples were set between two layers of quartz wool and left
under 50 mL min-1 He at 313 K for 40 min. Then, desorp-
tion profile was recorded with a mass spectrometer (M-
200GA-DM, Anelva Co.) from 313 K to 873 K with the
ramp rate at 10 K min-1 under helium flow. The following
In this paper, several alkylammonium isopolymolyb-
dates were prepared with the above amines and charac-
terized. Then, crystalline orthorhombic MoVO were hy-
drothermally synthesized by using the prepared al-
kylammonium isopolymolybdates instead of AHM. We
found that the obtained MoVO possessed the al-
kylammonium cations in the heptagonal channel of the
structure. This is the first example of orthorhombic Mo-
VO crystal containing the alkylammonium cation in the
structure.
EXPERIMENTAL SECTION
Preparation of alkylammonium isopolymolybdate
by evaporation. The preparation method for me-
thylammonium ispolymolybdate are shown as a typical
example. 22.594 g of MoO3 (0.150 mol, Kanto) was dis-
solved in 33.2 ml of 40% methylamine solution (methyla-
mine: 0.300 mol, Wako). After completely dissolved, the
solution was evaporated under vacuumed condition of
P/P0= 0.03 at 343 K and then solid powder was obtained.
The powder was dried in air at 353 K overnight. Thus pre-
pared alkylammonium isopolymolybdate is abbreviated as
MAHM (methylammonium heptamolybdate). The details
preparation method and abbreviated name for other al-
kylammonium isopolymolybdates were described in sup-
porting information.
Preparation of alkylammonium isopolymolybdate
by precipitation. In the case of ethylenediamine,
1,2−propanediamine and 1,3−propanediamine, 40 ml of
35% of HCl (HCl: 1.3 mol, Wako) was added into the mix-
ture solution of amine solutions (0.30 mol) and 22.594 g
of MoO3 (0.15 mol), then stirred for 30 min. During stir-
ring, white crystal powder was deposited. Then, the pow-
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Chemistry of Materials
desorption species were monitored by corresponding m/z
species: H2O (m/z= 18), NH3 (m/z= 16), N2 (m/z= 14, 28),
CO (m/z= 12, 28), CO2 (m/z= 44), CH3NH2 (m/z= 31), and
C2H5NH2 (m/z= 45).
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Catalytic test for ethane selective oxidation. Ethane
selective oxidation tests were performed at atmospheric
pressure using a fixed-bed flow reactor. The inner diame-
ter of the catalyst bed was 10 mm and the length was 30
mm. The catalysts ground in an agate mortar were cal-
cined in air at 673K for 2 h beforehand. The obtained
samples were diluted with SiO2 (50-80 mesh, Miyazaki
Chemicals). Then, the mixed powder (net catalyst weight;
0.5 g) was set into the reactor and heated at 623K under
N2 flow (40 mL min-1). N2 gas was replaced to the reaction
gas with the composition of C2H6/O2/N2= 1: 1: 8 (the total
flow rate was 50 mL min-1) and the condition was kept for
2 h at 623K. Then the catalytic test was started at the re-
action temperature of 573 K. The reactants and products
were analyzed with three on-line gas chromatographs,
Molecular Sieve MS13X with TCD (for O2, N2 and CO),
Gaskuropack 54 with TCD (for CO2, C2H4 and C2H6), and
Porapak Q with FID (for CH3COOH). The carbon balance
was always more than 98%.
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Fig. 2 Raman spectra of alkylammonium isopolymolybdates,
(a) AHM; (b) MAHM; (c) DMATM; (d) TMATM; (e) EATM;
(f) PAHM; (g) EDATM; (h) 1,2-PDATM; (i) 1,3-PDATM.
RESULTS AND DISCUSSION
Characterization of prepared alkylammonium iso-
polymolybdates. Alkylammonium isopolymolybdates
were prepared and isolated. MAHM, DMATM, TMATM,
EATM and PAHM were synthesized by the evaporation,
while EDATM, 1,2−PDATM and 1,3−PDATM were synthe-
sized by the precipitation method. Obtained isopoly-
molybdates were dried at 353K and analyzed by the Ra-
man spectroscopy in order to identify the species of mo-
lybdate anion. Fig. 2 shows Raman spectra of AHM and
the prepared alkylammonium isopolymolybdate. All sam-
ples exhibit a strong band around 930–950 cm−1, which
are characteristic stretching modes of Mo=O bonds [41].
AHM sample showed the Raman band at 937 cm−1 which
can be attributed to the asymmetric stretching vibrations
of Mo=O bond of heptamolybdate (Mo7O246−) anion. This
band was also observed in MAHM and PAHM at 940 cm−1,
indicating the formation of Mo7O246− in these compounds
too. The other alkylammonium isopolymolybdates
(DMATM, TMATM, EATM, EDATM, 1,2−PDATM and
1,3−PDATM) showed the band at 950 cm−1 which can be
attributed to the asymmetric stretching vibrations of
Mo=O bond of trimolybdate (Mo3O102−) anion. Observed
other week bands beside the main bands might be ascrib-
able to vibrations of Mo-O-Mo of the isopolymolybdates
with band shifts depending on alkylammonium cations.
DMA, and EA, the initial pH values of the mixture solu-
tion of alkylamine (0.30 mol) and MoO3 (0.15 mol) were
8.55, 6.93, 8.45, 7.91, and 7.55, respectively, so that the
2−
isopolymolybdate anions of either of Mo7O246− or Mo3O10
were formed by the simple evaporation method. On the
other hand, in the synthesis of EDATM, 1,2−PDATM, and
1,3−PDATM, the initial pH values of the mixture solution
were 8.93, 8.55, and 9.88, respectively. The pH values
6−
were so high that isopolymolybdates such as Mo7O24 or
2−
Mo3O10 were not formed by the evaporation but com-
−
pounds of molybdate anion (MoO4 ) was generated. The-
se molybdates were identified as (NH2CH2CH2NH2)MoO3,
(NH2CH2CH2(NH2)CH2)MoO3
and
(NH3CH2CH2CH2NH3)MoO4 by CHN analysis and Raman
spectra [46]. We found that these alkylammonium mo-
lybdates afforded no MoVO materials. Therefore, we em-
ployed the precipitation method with the addition of HCl
for these amines. The adjusted pH values of the solution
were 6.12 (EDA), 4.65 (1,2−PDA) and 6.72 (1,3−PDA) and
2−
as expected, alkylammonium molybdates of Mo3O10
were obtained.
Table 1 shows the results of CHN elemental analysis and
the percentage degree of weight loss measured by thermal
gravimetric (TG) analysis. Chemical formula for each
alkylammonium isopolymolybdate was determined on
the basis of stoichiometry between isopolymolybdates
anions and alkylammonium cations. Then the values of
CHN were calculated. Theoretical weight loss was calcu-
lated from the chemical formulas and by assuming that
the residue was MoO3 after the analysis of TG. These cal-
culated values are also summarized in Table 1. The ob-
It is well known that pH value and cationic species af-
2−
fect the formation of molybdate anion [41]. MoO4 anion
is produced when MoO3 is dissolved in alkaline solution.
The dominant molybdate species in aqueous solution
depending on pH are MoO42− (pH>6.3), Mo7O246− (pH=5.0)
2−
and Mo3O10 (pH=4.0). In the present work, the predom-
6−
2−
inant species were either Mo7O24 or Mo3O10 depending
on alkylammonium cations. In the case of MA, PA, TMA,
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tained data showed good agreements between the calcu- tion pattern. Since it was difficult to obtain crystal infor-
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lated elemental composition and the percent weight loss,
suggesting that corresponding stoichiometric al-
kylammonium isopolymolybdates were formed and iso-
lated. It should be noted that in the case of PAHM, the
measured values were well-consistent with the calculated
CHN and the percent weigh loss by assuming the compo-
sition of CH3CH2CH2NH2 (CH3CH2CH2NH3)6Mo7O24 in
which neutral CH3CH2CH2NH2 is occluded. Fig. S1 shows
the XRD patterns of MoO3 (starting material), AHM (rea-
gent) and synthesized alkylammonium isopolymolyb-
mation on TMATM, PAHM and 1, 2−PDATM due to their
poor crystallinity, we are undertaking experiments to find
suitable synthetic conditions.
The characterization data of obtained material were
summarized below.
(CH3NH3)6Mo7O24 (MAHM):
Anal.
Calcd
for
(CH3NH3)6Mo7O24: C, 5.8; H, 2.9; N, 6.7. Found: C, 5.8; H,
2.8; N, 6.8. IR (1700-500 cm-1): 1616, 1540, 1497, 1483, 1461,
1430, 1390, 1257, 1006, 973, 933, 914, 902, 885, 864, 834,
662, 634 cm-1. Raman (1000-800 cm-1): 937, 906, 895, 888,
851 cm-1. TG-DTA: 423~473 K, -6.6% (endothermic);
473~533 K, -4.2%; 533~563 K, -6.1% (exothermic); 563~673
K, -3.8% (exothermic). The crystal phase of MAHM was
monoclinic (space group C121) phase with a = 16.508, b =
11.254, c = 15.542 Å, α = γ = 90°, β = 100.0°, Vc = 2887.4 Å3.
The structure model was refined to Rwp = 19.63% and Rp =
13.89% for 914 reflection peaks.
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dates. MoO3 gives the main peaks at 2θ= 12.6, 23.3, 25.6,
27.3 and no these diffractions were observed in the ob-
tained alkylammonium isopolymolybdates. The XRD Pat-
terns of the synthesized alkylammonium isopolymolyb-
dates did not match those of related compounds in the
database of the International Centre for Diffraction Data
(ICDD). These are considered new patterns of single pha-
sic crystal powders. Thus, the patterns of the x-ray pow-
der diffraction were indexed and the symmetry and cell
dimensions were calculated with the X-Cell (Powder In-
dexing, Accerlys). The calculated results were refined by
Pawley method after indexing.
((CH3)2NH2)2Mo3O10∙H2O (DMATM)
: Anal. Calcd
for ((CH3)2NH2)2Mo3O10∙1H2O: C, 8.6; H, 3.2; N, 5.0.
Found: C, 8.7; H, 3.1; N, 5.1. IR (1700-500 cm-1): 1633, 1600,
1462, 1433, 1415, 1383, 1230, 1030, 1017, 936, 926, 911, 897,
884, 827, 789, 649, 611, 593, 579, 570, 557, 531, 521, 508 cm-
1. Raman (1000-800 cm-1): 950, 916 cm-1. TG-DTA: 423~473
K, -3.9% (endothermic); 473~563 K, -8.8% (exothermic);
563~763 K, -5.1% (small exothermic). The crystal phase of
DMATM was orthorhombic (space group C2) phase with
a = 20.772, b = 10.775, c = 7.973 Å, α = β = γ = 90°, Vc =
1784.5 Å3. The structure model was refined to Rwp = 7.66%
and Rp = 17.92% for 824 reflection peaks.
Fig. S2 shows the simulated patterns for MAHM,
DMATM, EATM and EDATM. The crystal group of
DMATM, EATM and EDATM were found to be ortho-
rhombic (space group C2) and the crystal group of
MAHM was found to be monoclinic (space group C121).
Yamase et al. reported that DMATM was synthesized by
the precipitation method from Na2MoO4.2H2O and
(CH3)2NCS2∙2H2O with the addition of hydrochloric acid
[43]. EDATM synthesized by hydrothermal method was
reported by Guillou et al. [44]. The XRD patterns of
DMATM and EDATM prepared by the evaporation meth-
od employed here were different from those reported in
the literatures. No structural reports were found concern-
ing MAHM and EATM to the best of our knowledge. 1,3-
PDATM Synthesized under hydrothermal conditions was
reported by Ding et al. and possessed a triclinic structure
[45]. However, 1,3-PDATM synthesized by the precipita-
tion method in the present work gave a different diffrac-
((CH3)3NH)2Mo3O10 (TMATM): Anal. Calcd for
((CH3)3NH)2Mo3O10: C, 12.7; H, 3.5; N, 4.9. Found: C, 12.7;
H, 3.5; N, 5.0. IR (1700-500 cm-1): 1620(s), 1480(s), 1454,
1416, 1370, 1046, 986(s), 928(s), 900(s), 840, 817, 712(s),
696(s) cm-1. Raman (1000-800 cm-1): 948, 925, 904, 893,
820cm-1. TG-DTA: 373~423 K, -5.5% (endothermic);
423~523 K, -6.6% (endothermic); 523~583 K, -8.1% (exo-
thermic); 583~733 K, -4.5% (exothermic).
Table. 1 Elemental composition of prepared alkylammonium isopolymolybdate analyzed by CHN elemental
analysis and TGA
Abbreviation of al-
kylammonium iso-
polymolybdates
C [wt%]
H [wt%])
N [wt%]
weight loss[wt%]
Composition of alkylammonium iso-
polymolybdates
obs. (calc.) obs. (calc.) obs. (calc.) obs.
(calc.)
(19.2)
(19.7)
(24.0)
(19.7)
MAHM
DMATM
TMATM
EATM
(CH3NH3)6Mo7O24
((CH3)2NH2)2Mo3O10∙1H2O
((CH3)3NH)2Mo3O10
5.8
8.7
12.7
9.0
(5.8)
(8.6)
(12.7)
(8.9)
2.8
3.1
(2.9)
(3.2)
(3.5)
(3.0)
6.8
5.1
(6.7)
(5.0)
(4.9)
(5.2)
20.7
17.8
24.7
18.7
3.5
2.9
5.0
5.2
(CH3CH2NH3)2Mo3O10
CH3CH2CH2NH2
(CH3CH2CH2NH3)6Mo7O24
PAHM
17.1
(17.1)
4.8
(4.7)
6.7
(6.6)
28.1
(31.7)
EDATM
(NH3CH2CH2NH3)Mo3O10∙1H2O
(NH3CH2CH(NH3)CH3)Mo3O10∙1H2O
(NH3CH2CH2CH2NH3)Mo3O10∙1H2O
4.7
6.9
6.7
(4.6)
(6.6)
(6.6)
2.4
2.4
2.8
(2.3)
(2.6)
(2.6)
5.5
5.4
5.2
(5.3)
(5.2)
(5.2)
15.8
17.1
17.1
(15.3)
(17.6)
(17.6)
1,2-PDATM
1,3-PDATM
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Chemistry of Materials
under hydrothermal condition at 448 K for 48 h. The ob-
tained samples were abbreviated as MoVO-
1
2
3
4
5
6
7
8
9
(CH3CH2NH3)2Mo3O10 (EATM): Anal. Calcd for
(alkylammine). Dark gray samples were obtained after the
hydrothermal synthesis, except with PAHM. Of key im-
portance is the pH of precursor solution in synthesizing
the crystalline MoVO complex oxide. In the case of AHM,
orthorhombic MoVO can be synthesized at the range of
pH value from 2.7 to 3.4 [47]. The pH=4.1 in the PAHM
solution was high probably due to the occluded amine
and thus prevented the formation of MoVO oxide. The
pH value of the other precursor solution after mixing with
vanadyl sulfate was 3.2 (MoVO-MA), 2.5 (MoVO-EA), 2.7
(MoVO-DMA), 2.6 (MoVO-TMA), 3.0 (MoVO-EDA), 2.5
(MoVO-1, 2-PDA), and 2.8 (MoVO-1, 3-PDA). Except for
MoVO- PA, the pH values were within the range for form-
ing the orthorhombic structure.
(CH3CH2NH3)2Mo3O10: C, 8.9; H, 3.0; N, 5.2. Found: C, 9.0;
H, 2.9; N, 5.2. IR (1700-500 cm-1): 1613, 1510, 1482, 1458,
1403, 1319, 1201, 1051, 996, 983, 953, 928, 916, 890, 880, 864,
793, 786, 652, 605, 573, 562, 552, 543, 526, 503 cm-1. Raman
(1000-800 cm-1): 950, 915, 902 cm-1. TG-DTA: 473~543 K, -
9.8% (exothermic); 563~663 K, -5.1%; 663~733 K, -3.8%
(exothermic). The crystal phase of EATM was ortho-
rhombic (space group C2) phase with a = 7.598, b =
22.424, c = 15.776 Å, α = β = γ = 90°, Vc = 2687.90 Å3. The
structure model was refined to Rwp = 6.84% and Rp =
10.08% for 454 reflection peaks.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
CH3CH2CH2NH2 (CH3CH2NH3)6Mo7O24 (PAHM): Anal.
Calcd for CH3CH2CH2NH2 (CH3CH2CH2NH3)6Mo7O24: C,
17.1; H, 4.7; N, 6.6. Found: C, 17.1; H, 4.8; N, 6.7. IR (1700-
500 cm-1): 1612(s), 1503, 1470, 1392, 1193, 1128, 902(s), 884(s),
863(s), 662(s), 636(s) cm-1. Raman (1000-800 cm-1): 935,
907, 891cm-1. TG-DTA: 373~393 K, -13.1% (exothermic),
393~533 K, -8.0% (exothermic), 533~733 K, -7.0% (exo-
thermic).
Fig. 3 shows XRD patterns of the synthesized MoVO
complex oxides. The characterization results by XRD, ICP
and XPS are also listed in Table 2 and 3. All of the ob-
tained samples possessed diffraction peaks at 2θ= 22° and
45°. These two peaks can be attributed to (001) and (002)
planes, respectively, indicating that the materials have a
layer-type crystal structure. Moreover, the diffraction pat-
terns of MoVO−A, MoVO−MA and MoVO−DMA catalysts
showed the orthorhombic phase. We have previously re-
ported the indexing of these materials in detail [18, 22].
No peaks related to any impurities were observed in these
three samples. The anion unit of alkylammonium isopol-
(NH3CH2CH2NH3)Mo3O10∙H2O (EDATM): Anal. Calcd
for (NH3CH2CH2NH3)Mo3O10∙1H2O: C, 4.6; H, 2.3; N, 5.3.
Found: C, 4.7; H, 2.4; N, 5.5. IR (1700-500 cm-1): 1630, 1616,
1596, 1528, 1512, 1503, 1459, 1454, 1413, 1373, 1337, 1317, 1235,
1215, 1171, 1160, 1085, 1047, 1035, 1007, 981, 926, 912, 894,
830, 821, 653, 531 cm-1. Raman (1000-800 cm-1): 950, 924,
916, 904 cm-1. TG-DTA: 473~563 K, 8.3% (exothermic);
563~733 K, 7.5% (exothermic). The crystal phase of
EDATM was orthorhombic (space group C2) phase with a
= 10.925, b = 13.928, c = 7.555 Å, α = β = γ = 90°, Vc = 1151.2
6-
ymolybdate was Mo7O24 for AHM and MAHM, and
Mo3O102- for DMATM. Mo7O246- and Mo3O102- anion species
in precursor solution, therefore, seems to have less effects
on the formation of the orthorhombic MoVO. The Mo-
VO−A, MoVO−MA and MoVO−DMA catalysts were fi-
brous rod particles, which is also unaffected by the al-
kylammonium cations, as shown in Fig. 4.
Å3 and Z = 8. The structure model was refined to Rwp
7.30% and Rp = 14.56% for 214 reflection peaks.
=
On the other hand, MoVO−TMA, MoVO−EA, Mo-
VO−EDA and MoVO−1, 2−PDA samples had diffraction
patterns different from MoVO−A. The broad peaks
around 2θ = 8°, 27° were observed in addition to 22° and
45°, indicating that these materials were crystallized in
the c-direction only but disordered in the other direc-
tions. In a similar fashion to those reported previously
[17, 48], here in this paper this material is designated as
amorphous MoVO. The MoVO−1,3−PDA sample
contained (NH4)0.38V2O5 and (NH4)2Mo3O10 phases.
(NH3CH2CH(NH3)CH3)Mo3O10∙H2O
(1,2−PDATM):
Anal. Calcd for (NH3CH2CH(NH3)CH3)Mo3O10∙1H2O: C,
6.6; H, 2.6; N, 5.2. Found: C, 6.9; H, 2.4; N, 5.4. IR (1700-
500 cm-1): 1605(s), 1580(s), 1508(s), 1460, 1407, 1395, 1368,
1336, 1317, 1218, 1163, 1080, 1052, 1023, 937(s), 884(s), 861,
765, 718(s), 664(s), 608(s) cm-1. Raman (1000-800 cm-1):
952, 924, 904, 894, 862, 831 cm-1. TG-DTA: 403~573 K, -
8.6% (exothermic); 537~723 K, -8.5% (exothermic).
(NH3CH2CH2CH2NH3)Mo3O10∙H2O (1,3−PDATM)
:
Anal. Calcd for (NH3CH2CH2CH2NH3)Mo3O10∙1H2O: C, 6.6;
H, 2.6; N, 5.2. Found: C, 6.7; H, 2.8; N, 5.2. IR (1700-500
cm-1): 1625(s), 1513(s), 1471(s), 1409, 1202(s), 1121(s), 1049,
937(s), 926(s), 910(s), 886(s), 862, 750, 653(s), 529(s) cm-1.
Raman (1000-800 cm-1): 952, 911, 892, 883, 876 cm-1. TG-
DTA: 423~553 K, -7.5% (exothermic); 553~803 K, -9.6%
(exothermic).
Synthesis of orthorhombic MoVO complex oxide.
MoVO complex oxides were synthesized by using the al-
kylammonium isopolymolybdates and vanadyl sulfate
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1
2
Table. 2 Crystalline phase and the yield of various
MoVO
3
4
5
6
7
8
9
Catalyst
Crystalline phase
Orthorhombic
Orthorhombic
Orthorhombic
Amorphous2
Yield1 [%]
30.0 (11.6)
40.0 (11.6)
58.2 (17.3)
44.4 (9.3)
47.8 (9.7)
79.6 (13.3)
87.9 (10.0)
MoVO-A
MoVO-MA
MoVO-DMA
MoVO-TMA
MoVO-EA
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Amorphous2
Fig. 4 SEM images of (a) MoVO-A; (b) MoVO-MA; and (c)
MoVO-DMA.
MoVO-EDA
Amorphous2
MoVO-1,2-
PDA
Amorphous2
It is reported that the only difference between ortho-
rhombic and amorphous MoVO complex oxide was the
elemental arrangement in the a-b plane of crystal struc-
ture. In fact, all the obtained samples showed fibrous rod
morphology by SEM (not shown). The yields of MoVO-
TMA, -EA, -EDA, -1, 2-PDA and -1, 3-PDA before
purification were higher than that of MoVO-A. However,
these large alkylammonium cations inhibit the formation
for periodic arrays of the pentagonal {Mo6O21} unit and
MO6 (M = Mo, V) octahedral unit, such that they acceler-
ate the random condensation of units for amorphous
MoVO.
MoVO-1,3-
PDA
Amorphous2, (NH4)0.38V2O5
and (NH4)2Mo3O10 phases
90.0 (8.3)
1 Yield after purification was noted in brackets.
2 Amorphous Mo3VOx material well-crystallized in c-
direction but disordered in the other direction.
The obtained orthorhombic Mo3VOx using the alkylammoni-
um isomolybdates were characterized by Mo/V ratio in bulk
and on surface by ICP and XPS, and by CHN elemental anal-
ysis. The elemental composition of MoVO-A has been de-
termined to be Mo28.6V11.4O112(NH4)3.7∙10.0H2O in our previous
work [20]. In the present study, the compositions of MoVO-
MA and MoVO-DMA were determined to be
Mo32.3V7.7O112(CH3NH3)4.0∙9.7H2O
and
Mo30.2V9.8O112((CH3)2NH2)2.5・8.5H2O, respectively, where the
corresponding alkylammonium cations were occluded in the
orthorhombic structure of MoVO. The Mo/V atomic ratios
both in MoVO-MA and MoVO-DMA were appreciably high-
er than that in MoVO-A. The reason for this change is un-
clear at the present stage. On the other hand, the ortho-
rhombic structure was practically unaffected at all by the
presence of the alkylammonium cations in the structure. The
lattice parameters changed only slightly when the al-
kylammonium cations were incorporated; the lattice parame-
ters (Å) for MoVO-MA were a= 21.15 b= 26.48 c= 4.00, for
MoVO-DMA were a= 21.06 b= 26.49 c= 4.00, and for MoVO-
A were a= 21.05 b= 26.47 c= 4.00, respectively.
Fig. 3 XRD patterns of (a) MoVO-A; (b) MoVO-MA; (c)
MoVO-DMA; (d) MoVO-TMA; (e) MoVO-EA; (f) MoVO-
Ammonium cation plays an important role in the formation
of the orthorhombic Mo3VOx mixed-metal oxide from AHM
and vanadyl sulfate under hydrothermal conditions. The
{Mo6O21} and {MO6}(M=Mo or V) units are first formed and
then start condensation to form the heptagonal channels
with occluding NH4+ cation. NH4+ cation is, therefore,
EDA;
(g)
MoVO-1,2-PDA;
(h)
MoVO-1,3-PDA.
((NH4)0.38V2O5(●) and (NH4)2Mo3O10 (○)phases has been
marked with the pattern (h).
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Chemistry of Materials
Table. 3 List of the catalyst abbreviation and elemental composition of synthesized orthorhombic MoVO us-
ing various isopolymolybdate precursors
1
2
3
4
5
6
7
8
9
The ratio of Mo/V
Lattice
Catalyst
Mo precursor
AHM
Composition of catalystb
parameter
Preparativea
ICP
XPS
a= 21.05
b= 26.47
c= 3.996
MoVO-A
1 / 0.25
1 / 0.38
1 / 0.24
Mo28.6V11.4O112(NH4)3.7・10.0H2O
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
a= 21.15
b= 26.48
c= 3.997
MoVO-MA
MAHM
1 / 0.25
1 / 0.25
1 / 0.24
1 / 0.32
1 / 0.18
1 / 0.21
Mo32.3V7.7O112(CH3NH3)4.0・9.7H2O
a= 21.06
b= 26.49
c= 3.995
MoVO-DMA
DMATM
Mo30.2V9.8O112((CH3)2NH2)2.5・8.5H2O
a Preparative composition of elements in the slurry, b Calculated by CHN elemental analysis and ICP.
accommodate in the heptagonal channel such as smaller
alkylammonium cations. However, the MoVO were syn-
thesized from these alkylammonium isopolymolybdates
in relatively high yield as listed in Table 2. Apparently,
these cations promoted the condensation of {Mo6O21} and
{MO6}(M=Mo or V) units although the promotion was to
the direction of the formation of amorphous-type phase.
It is interesting to note that dimethylammonium cation
induced to form the orthorhombic MoVO while amor-
phous MoVO was formed when ethylammonium cation
was introduced, even though the cation size of
ethylammonium cation is almost the same as that of di-
methylammonium cations. The slight difference of cation
size would be decisive factor for the formation of ortho-
rhombic structure under hydrothermal conditions.
considered not only to neutralize the charge of metal oxide
but also to play a role of promoting the structure formation
and stabilization of the orthorhombic phase. Fig. 5 shows the
image of orthorhombic MoVO incorporated with al-
kylammonium cations. The diameter of the micropores at-
tributed to heptagonal channel is estimated to be 4.0 Å [22].
The molecular size of methylammonium cation is about 3.8
Å in diameter of horizontal configuration and that of dime-
thylammonium cation is about 3.1 Å in diameter of the
smallest configuration. Therefore, methylammonium and
dimethylammonium cations could be incorporated into the
heptagonal channel without collapsing the whole crystal
structure and even work as a stabilizer of the crystalline or-
thorhombic structure. The number of heptagonal channels in
the unit cell of the orthorhombic structure is 4.
The existence of the alkylammonium cations in the
MoVO was also proven using FT-IR spectroscopy. Fig. 6
illustrates FT-IR spectra of the synthesized MoVO sam-
ples. According to the previous IR study on MoVO mate-
rials, the absorption at 875 cm-1 assigned to symmetric
stretching vibrations of the Mo=O cis-dioxo groups, while
absorption at 799, 720 and 646 cm-1 are due to antisym-
metric vibrations of Mo–O–Me (Me= Mo, V) bridging
bond [9, 49]. Moreover, absorption bands at 915, 601 cm-1
relate to V=O groups and V–O–Me (Me= Mo) bonds. All
these absorption bands based on the metal-oxygen bonds
were observed in the present MoVO samples, revealing
that the basic structure of the metal oxide framework is
the same. Detailed analyses of the FT-IR spectra of al-
kylammonium in the orthorhombic MoVO synthesized
by AHM, MAHM and DMATM were conducted in Fig. 6b.
Concomitantly, the number of methylammonium cation was
determined to be 4.0 and that of ammonium cation was 3.7
in the unit cell. Obviously, these cations fully occupied the
heptagonal channel. The steric hindrance is considered to be
excluded the possibility of the vertical array of methylammo-
nium cation, thus, methylammonium cation might be ar-
rayed horizontally. On the other hand, dimethylammonium
cations can locate only in a longitudinal direction in the hep-
tagonal channel. Large cation cannot exist periodically be-
cause of the unit cell length in the c- direction (4.00 Å). In
fact, the number of dimethylammonium cations in the unit
cell of MoVO-DMA was 2.5, which suggests that 62.5% of
heptagonal channel was occupied and the other may be oc-
cupied by H+.
The amorphous MoVO were formed when TMATM,
EATM, EDATM and 1, 2−PDATM used as Mo precursors.
The molecular size of trimethylammonium cation, eth-
ylendiammonium cation, and 1,2-propyldiammonium
cation are undoubtedly much larger than that of heptag-
onal channel, indicating that these cations are unable to
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1466 cm-l assigned to asymmetric deformation vibration
1
2
3
4
5
6
7
of the CH3 vibration and C–H stretching and the band at
1499 cm-1 assigned to deformation vibration of NH3+ were
observed [50, 51]. In MoVO-DMA, the band at 1080 cm-l
assigned to the stretching vibration of C-N-C bond was
observed in addition of CH3 vibration adsorption. These
results are clear evidences that can support the existence
of alkylammonium species in the structure of MoVO.
8
9
The IR spectra of MoVO-TMA, MoVO-EA, MoVO-EDA
and MoVO-1,2-PDA are shown in Fig. 6c. There showed
the adsorption bands on its alkylamine or
alkylammonium cation [52, 53], but were of low intensity
in the MoVO samples synthesized with lager
alkylammonium cations. The spectra of these amorphous
MoVO samples shows the adsorption at 1396 cm-1 as-
signed to an asymmetric deformation vibration of the
ammonium ions, suggesting that the alkylammonium
cations were decomposed to ammonium cations.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Fig. 5 Polyhedral presentations of a-b plane and the image
of heptagonal channel for MoVO-MA (a, b) and MoVO-
DMA (c, d). (green: pentagonal {Mo6O21} unit, light blue:
Mo or V octahedral, red: oxygen, blue: nitrogen, gray:
carbon and white: hydrogen)
Microporosity of synthesized orthorhombic MoVO
complex oxide. We have previously reported that the
orthorhombic MoVO synthesized by AHM shows N2 ab-
sorption of type I which is typical for microporous mate-
rials [23]. Ammonium cations can be removed from the
heptagonal channel by heat treatment at 673K in air
without collapse of the structure and microporosity de-
rived from the empty heptagonal channel appears[22].
Microporosity in MoVO-MA and MoVO-DMA should be
also expected similar to MoVO-A if the alkylammonium
cations can be removed without collapsing the crystal
structure. Therefore, N2 adsorption isotherms were meas-
ured for MoVO-MA and MoVO-DMA before and after
calcination. The MoVO-MA and MoVO-DMA samples
were first calcined at 673K in air for 2 h and then further
pretreated at 673K for 2 h under vacuum just before N2
adsorption measurement. As for the uncalcined samples,
the heat-treatment at 423K for 2 h under the vacuum
condition was only conducted. As ascertained by the XRD
pattern, the crystalline structure of the orthorhombic
phase was kept unchanged after the heat treatment ex-
cept for a small change in the unit-cell parameters (not
shown). Samples were ground well by an agate mortar
and N2 adsorption isotherms were measured at 77 K. The
results are shown in Fig. 7. Clear adsorption of N2 at low
pressure (P/P0 ≈ 10−7) was observed in both the calcined
MoVO-MA and MoVO-DMA samples, while such adsorp-
tion was not observed in both the uncalcined samples.
Adsorption at low pressure below 10-5 P/P0 is the indica-
tion of microporosity, so that it is evident that the cal-
cined MoVO-MA and MoVO-DMA samples are a mi-
croporous material. The results at the same time support
that methylammonium and dimethylammonium cations
were incorporated into heptagonal channel and these
cations were removed by the calcination in air, leaving
empty heptagonal channels.
Fig. 6 IR spectra of (a) synthesized MoVO catalyst, (b)
enlarged spectra of orthorhombicMoVO-A, MoVO-MA and
MoVO-DMA, (c) enlarged spectra of MoVO-TMA, MoVO-EA,
MoVO-EDA, MoVO-1,2-PDA, MoVO-1,3-PDA.
External surface area was calculated by the t-plot
method. The external surface area of MoVO-MA and Mo-
VO-DMA were 18.6 and 15.9 m2 g-1, which were larger than
In the IR spectra of MoVO-A, adsorption at 1401 cm-1 as-
signed to an asymmetric deformation vibration of the
ammonium cation. In MoVO-MA, the bands at 1451 and
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Chemistry of Materials
Table. 4 The results of nitrogen adsorption and selec-
that of MoVO-A (7.3 m2 g-1). According to the results of
1
2
3
4
5
6
SEM image (Fig. 4), the shape of the particle is responsi-
ble for the increase of external surface area. Fig. S3 illus-
trates the distribution of particle diameters obtained from
analysis of SEM images. The average diameter was 0.22
μm (MoVO-MA) and 0.15 μm (MoVO-DMA), which were
smaller than that of MoVO-A (0.42 μm).
tive oxidation of ethane over the synthesized ortho-
rhombic MoVO catalysts at 300°Ca
catalyst
C2H6
conv.
Sel. [%]
Aextb Pvolc
[m2 g-1] [cm3 g-1]
Temp.
[°C]
C2H4
83.4
COx
12.5
AcOHd
3.0
[%]
7
8
9
MoVO- 7.2 0.0130 300.1
A
20.9
This means that longer fibrous MoVO were synthesized
by using methylammonium or dimethylammonium cati-
ons than by ammonium cation.
MoVO- 16.7 0.0137 298.8
MA
23.7
28.3
86.0
87.2
9.1
3.6
3.8
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
MoVO- 15.0 0.0161 298.8
DMA
8.6
Fig. 8 shows the TPD profile of (a) MoVO-MA and (b)
MoVO-DMA samples. The rate of temperature increase
was 10 K min-1 for the desorption of species formed by the
decomposition of alkylammonium cation under the TPD
in flowing He. Several desorption of NH3 (m/z=16), CO
and N2 (m/z=28), and CO2 (m/z=44) were observed at
603K in both MoVO-MA and MoVO-DMA samples. The
high temperature desorption of these species clearly
proves that alkylammonium cations existed in the hep-
tagonal channel are decomposed.
a Reaction conditions: 0.5 g catalyst, flow rate 50 ml min-1,
composition C2H6/O2/N2 = 1: 1: 8, b Aext: External surface
area calculated by t-plot, c Pvol : pore volume calculated by t-
plot, d AcOH : Acetic acid
firmed that the structures remained unchanged. External
surface area and pore volume of the catalysts after the
reaction were calculated by the t-plot method and are
listed in Table 4. The pore volume of MoVO-DMA was
larger than that of MoVO-A and MoVO-MA, potentially
due to the different configuration of the counter cations
in the heptagonal channel. MoVO-A showed high catalyt-
ic activity for the reaction as reported previously [19, 48].
Similarly, MoVO-MA and MoVO-DMA showed the con-
version of 24% and 28%, which is a little higher compared
to that of MoVO-A.
The selectivity to ethylene was also slightly higher in
the MoVO-MA catalyst and the MoVO-DMA catalysts.
The active site of ethane oxidation has been suggested not
to relate to the lateral face of the rod particle, rather to
the heptagonal channel of the a-b plane by comparison of
the catalytic activity using several crystalline structures
[48]. The present work also supports that the ethane oxi-
dation takes place in the heptagonal channel, since the
three samples with the same crystalline structure showed
comparable catalytic activity although different external
surface areas.
Fig.7 Adsorption isotherms of (a) MoVO-MA and (b) MoVO-
DMA. ▲, ■: samples were dried with air at 373K, ●, ♦: sam-
ples were heat-treated under air flow at 673 K.
CONCLUSIONS
Various alkylammonium isopolymolybdates were syn-
thesized by the evaporation or by precipitation methods
and pure materials comprised of methylammonium hep-
tamolybdate,
dimethylammonium
trimolybdate,
ethylammnium trimolybdate and ethylenediammonium
trimolybdate were obtained. The orthorhombic MoVO
materials incorporating methylammonium and dime-
thylammonium cations in their heptagonal channel were
synthesized for the first time by using the corresponding
alkylammonium isopolymolybdate. The morpholgy of the
crystalline particles were fibrous and their diameters were
much small compared with MoVO-A. These alkylammo-
nium cations could act as a stabilizer for the orthorhom-
bic structure under hydrothermal conditions. The incor-
porated cations were removed from the synthesized Mo-
Fig. 8 TPD spectra of synthesized MoVO-MA (a) and MoVO-
DMA (b). Samples were outgassed at 423 K under vacuum for
2h.
Catalytic activity of synthesized MoVO samples.
The catalytic activity of the synthesized orthorhombic
MoVO was tested in the oxidative dehydrogenation of
ethane (Table 4). After the reaction, XRD patterns con-
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[16] N.R. Shiju, V.V. Guliants, ChemPhysChem. 2007, 8, 1615.
VO complex oxide by the calcination. The pore volume of
MoVO-DMA was larger than that of MoVO-A and MoVO-
MA, suggesting that dimethylammonium cation assists
well-arrangement of the heptagonal channel. The for-
mation of the micropore resulted in the catalytic activity
for ethane selective oxidation.
1
2
3
4
[17] W. Ueda, K. Oshihara, D. Vitry, T. Himeno, Y. Kayashima,
Catalysis surveys from Japan. 2002, 6, Nos. 1/2, 33-44.
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Chem. Intermed. 2006, 32, No. 3–4, 217–233.
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237-240.
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607-614.
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Chem. Int. Ed. 2008, 47, 2493 -2496.
[22] M. Sadakane, K. Yamagata, K. Kodato, K. Endo, K. Tori-
umi, Y. Ozawa, T. Ozeki, T. Nagai, Y. Matsui, N. Sakaguchi, W.
D. Pyrz, D. J. Buttrey, D. A. Blom, T. Vogt, W. Ueda, Angew.
Chem. Int. Ed. 2009, 48, 3782 –3786.
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K. Shimidzu, T. Murayama, W. Ueda, Chem. Commun. 2011, 47,
10812–10814.
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Ueda, T. Vogt, D. J. Buttrey, Chem. Mater. 2010, 22, 2033-2040.
[25] W. D. Pyrz, D. A. Blom, M. Sadakanec, K. Kodato, W.
Ueda, T. Vogt, D. J. Buttrey, PNAS. 2010, 107, 6153.
[26] A. Müller, P. Kögerler, A. W. M. Dress, Coord. Chem. Rev.
2001, 222, 193.
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Peters, Angew. Chem. Int. Ed. 1998, 37, 3360-3363.
[28] A. Müller, S.-Q.-N. Shah, H. Bögge, M. Schmidtmann, Na-
ture, 1999, 397, 48-50.
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M.Schmidtmann, B. Hauptfleisch, Angew. Chem. Int. Ed. 1999,
38, 3241-3245.
[30] M. Sadakane, N. Watanabe, T. Katou, Y. Nodasaka, W.
Ueda, Angew. Chem. Int. Ed. 2007, 46, 1493 –1496.
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[32] P. J. Hagrman, R. C. Finn, J. Zubieta, Solid State Sci. 2001,
3, 745–774.
ASSOCIATED CONTENT
Supporting Information.
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Preparation conditions of alkylammonium isopolymolyb-
dates, XRD data of alkylammonium isopolymolybdate,
the refinements results by Pawley method, distribution of
the diameter of MoVO particle, TPD spectra of calcined
MoVO. This material is available free of charge via the
Internet at http://pubs.acs.org.
■AUTHOR INFORMATION
Corresponding Author
*E-mail: murayama@cat.hokudai.ac.jp (T. Murayama);
ueda@cat.hokudai.ac.jp (W. Ueda)
Funding
This work has been supported by JSPS KAKENHI Grant
Number 2324-6135.
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concept, or theorem, etc., that is discussed in the manuscript. Consult the journal’s Instructions for Authors for
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Supporting Information
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Preparation of alkylammonium isopolymolybdate by evaporation.
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Alkylammonium isopolymolybdates were prepared by evaporation method. 22.594 g of MoO3 (Kanto;
0.150 mol) was added into the mixed solutions prepared each amount of the amine solution and water,
followed by the stirring for 30 min. The reason for the water addition is to reduce the viscosity of the
mixed solutions. The amine solutions used this time were 40% methylamine solution, 40% dimetylaꢀ
mine solution, 30% trimethylamine solution, 70% ethylamine solution, 98% of propylamine, 99% of
etylenediamine, 99% of 1,2ꢀpropanediamine, and 97% of 1,3ꢀpropanediamine, respectively. All of the
reagents were purchased from Wako. The amounts of the amine solution and water are shown in Table
S1. After MoO3 was dissolved completely, the mixed solutions were evaporated under vacuumed condiꢀ
tion of P/P0= 0.03 at 343 K for 30 min. Time was measured from the time that white powder was started
to precipitate. Obtained powder was dried in air at 353 K overnight. Prepared alkylammonium isopolyꢀ
molybdates are abbreviated as Table S1.
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Table. S1 Amount of amine solution and water for preparing alkylammonium isopolymolybdates and
the name of the obtained materials
Abbreviation of
alkylammonium isopolymolybdate
Amount of amine [ml]
Amount of water [ml]
40% metylamine
40% dimetylamine
30% trimetylamine
70% ethylamine
33.2
50.5
88.2
28.0
25.2
20.0
25.0
25.0
0
MAHM
DMATM
TMATM
EATM
0
0
28.0
88.2
40.0
100.0
100.0
98% propylamine
PAHM
99% etylenediamine
99% 1,2ꢀpropanediamine
97% 1,3ꢀpropanediamine
EDAMM
1,2ꢀPDAMM
1,3ꢀPDADM
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Fig. S1 Normalized XRD patterns of MoO3 (a); AHM reagent (b), and prepared isopolymolybdate precursors: MAHM
(c); DMATM (d); TMATM (e); EATM (f); PAHM (g); EDATM (h); 1,2ꢀPDATM (i); and 1,3ꢀPDATM (j).
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(a)
MAHM
Rwp = 19.63% Rwp(w/o bck) = 34.74% Rp = 13.89%
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sim
obs
difference
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(b)
DMATM
Rwp = 7.66% Rwp(w/o bck) = 7.81% Rp = 17.92%
sim
observed
difference
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2θ / ° (CuKα)
(c)
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sim
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2θ / ° (CuKα)
(d)
EDATM
Rwp = 7.30% Rwp(w/o bck) = 7.40% Rp = 14.56%
sim
obs
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2θ / ° (CuKα)
Fig. S2 The calculated results by Pawley method with the experimental results of (a)MAHM, (b)DMATM, (c)EATM
and (d)EDATM. Peaks of (Int/ Intmax)> 0.10 were identified below.
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ꢀ
ꢀ
ꢀ
MAHM
: 2θ= 9.5, (110); 2θ= 10.6, (111); 2θ= 10.9, (200); 2θ= 11.4, (201); 2θ=13.2, (201); 2θ=25.6, (403);
2θ=27.1, (420)
DMATM
EATM
: 2θ = 9.0, (200); 2θ= 9.8, (110); 2θ= 25.1, (420)
: 2θ = 9.7, (021); 2θ= 11.2, (002); 2θ= 26.0, (202)
: 2θ = 10.3, (110); 2θ= 12.7, (020); 2θ= 26.8, (022), 2θ= 31.1, (330)
EDATM
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0
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0
MoVO-DMA
MoVO-MA
MoVO-A
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0.2
0.4
0.6
0.8
0.2
0.4
0.6
0.8
0.2
0.4
0.6
0.8
Diameter [ꢀm]
Diameter [ꢀm]
Diameter [ꢀm]
Fig. S3 Distribution of the diameter of rod particle in orthorhombic MoVO samples.
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m/z = 16
m/z = 18
m/z = 28
m/z = 44
m/z = 45
m/z = 18
m/z = 16
m/z = 28
m/z = 31
m/z = 44
(a)
(b)
20000
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0
20000
10000
0
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100 200 300 400 500
Temperature / °C
Temperature / °C
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Fig. S4 TPD spectra of calcined samples. (a) MoVOꢀMA and (b) MoVOꢀDMA.
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