Hexagonal-, cubic-, and lamellar-mesostructured vanadium-phosphorus oxides were hydrothermally synthesized by using V metal as a reducing agent and a V source. The respective phases were tunably synthesized in the ranges of pH 2. 63-2.95, 3.00-3.36, and 3.45-4.45. It is suggested that the formation of these mesostructured materials depends on the solution species of vanadium and phosphorus. The unit cell constants of hexagonal, cubic, and lamellar phases were determined to be a ) 5.05 nm, a ) 8.54 nm, and c ) 3.22 nm, respectively. IR spectroscopy, XRD, and elemental analyses show that hexagonal-and cubicmesostructured materials possess an amorphous wall of vanadium-phosphorus oxides and their P/V ratios were 0.99 and 0.76, respectively. On the other hand, the lamellar mesostructured material possessed more crystalline layers of vanadium-phosphorus oxide with a P/V ratio of 0.50. The cetyltrimethylammonium templates could be exchanged with K + or Cs + .
Previously unknown cubic mesostructured vanadium–phosphorus oxide was synthesized by using V metal not only as a V source but also as a reducing agent for V2O5.
The reaction of hydrous titanium dioxide (TiO 2•nH 2 O, n=0.15-1.23) and dialkyl carbonates at 453-573 K offers a convenient synthetic method for titanium tetraalkoxides which are free from chlorine-containing impurities. Thus, hydrous titanium dioxide was almost completely converted into Ti(OEt) 4 by its reaction with diethyl carbonate at 493 K for 16 h. The reaction proceeded faster in the presence of a sodium hydroxide catalyst. From the hydrous titanium dioxide and dipropyl carbonate, Ti(OPrn) 4 was obtained in a high yield.
VOHPO 4 ‚0.5H 2 O is a good catalyst precursor of (VO) 2 P 2 O 7 , which is an active phase or active component for the industrialized oxidation of n-butane into maleic anhydride. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] In addition, the (100) plane of (VO) 2 P 2 O 7 , which is an active plane for the selective oxidation, 2,3,7,8,11,13 originates from the (001) plane of VO-HPO 4 ‚0.5H 2 O. 8,21,22 Therefore, the easy synthesis of VOHPO 4 ‚0.5H 2 O with a high growth of the (001) plane is interesting from the standpoint of catalyst preparation. VOHPO 4 ‚0.5H 2 O is also a catalyst precursor of (NH 4 ) 2 [(VO) 3 (P 2 O 7 ) 2 ] active for ammoxidation. [23][24][25] To date, four methods have been reported for the preparation of VOHPO 4 ‚0.5H 2 O: (1) the reduction of V 2 O 5 with alcohols followed by reaction with H 3 -PO 4 , [1][2][3][4]8,12,[14][15][16]21,22,[26][27][28] (2) the reaction of a mixture of V 2 O 5 and H 3 PO 4 with NH 2 OH‚HCl or oxalic acid followed by heat treatment at 403 K, 1,3,5,10,12,25,26,29 (3) the preparation of VOPO 4 ‚2H 2 O followed by reduction with alcohols, 3,8,12,13,21,22,30 and (4) hydrothermal synthesis with V 2 O 4 and H 3 PO 4 at 773 K. 31 Methods 1-3 consist of two steps and method 4 requires a high temperature of 773 K.Here, we report the one-pot synthesis of highly crystalline VOHPO 4 ‚0.5H 2 O at 473 K and its successive transformation to (VO) 2 P 2 O 7 by using V metal not only as a V source but also as a reducing agent for V 2 O 5 .The reagents used were commercially obtained and used without further purification. The synthesis of VOHPO 4 ‚0.5H 2 O was carried out in a Teflon vessel as follows: 2.31 g of H 3 PO 4 (85%) was added to an aqueous solution of cetyltrimethylammonium chloride (30 cm 3 , 0.66 mol‚dm -3 ), followed by the addition of V metal (0.204 g, 4.00 × 10 -3 mol) and V 2 O 5 (1.46 g, 8.00 × 10 -3 mol) or NaVO 3 (1.95 g, 1.60 × 10 -2 mol), or only VOSO 4 (4.35 g, 2.00 × 10 -2 mol) at room temperature. The resulting suspension was purged with Ar and then the Teflon vessel was moved to a stainless autoclave. The autoclave was kept at 473 K for 48 h. Finally, the solution was filtered and the resulting powder was washed with ca. 700 cm 3 of water followed by evacuation at room temperature for 5 h. The yield was ca. 50% on a V basis. The BET surface area was 4 m 2 ‚g -1 . Samples a-c of VOHPO 4 ‚0.5H 2 O were prepared according to methods 1-3, respectively, which were described in refs 5 and 12.The powder X-ray diffraction (XRD) patterns were recorded on a powder X-ray diffractometer (Materials Analysis and Characterization, MXP 3 ) by using Cu KR radiation. The infrared spectra of KBr pellets were recorded on a Perkin Elmer Paragon 1000PC spectrometer. Thermogravimetric and differential themal analysis (TG/DTA) was carried out in a N 2 flow (10 cm 3 ‚min -1 ) with Seiko Instruments TG/DTA 220. Transmission electron micrograph (TEM) and scanning electron micrograph (SEM) analyses were carried out with JEOL JEM-4000 FXII and JEOL TSM-T...
One-Pot Synthesis of VOHPO 4 ·0.5H 2 O with High Growth of the (001) Plane: An Important Catalyst Precursor of (VO) 2 P 2 O 7 .-VOHPO 4 ·0.5H 2 O is prepared in a one-pot synthesis and transformed to the catalyst by use of V metal as V source and as reducing agent. The synthesis is carried out by heating an aqueous slurry of H 3 PO 4 , cetyltrimethylammonium chloride, V metal and V 2 O 5 , NaVO 3 or VOSO 4 (473 K, autoclave, 48 h, 50% yield). The XRD pattern shows an orthorhombic structure. -(MIZUNO, N.; HATAYAMA, H.; MISONO, M.; Chem. Mater. 9 (1997) 12, 2697-2698 Dep. Appl. Chem., Grad. Sch. Eng., Univ. Tokyo, Bunkyo, Tokyo 113, Japan; EN)
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