Crystalline CrV0.95P0.05O4 catalyst for vapor-phase oxidation of picolines

Song, Zhaoxia; Matsushita, Toshiyuki; Shishido, Tetsuya; Takehira, Katsuomi

doi:10.1039/b202779h

Cited by 12 publications

(30 citation statements)

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“…35,36 In the breadth of this band for 10V12CrAl and 12Cr10VAl and in the absence of CrVO 4 , diffraction lines for these samples suggest that the CrVO 4 domains are disordered and highly dispersed. 27,[37][38][39] The 820 cm -1 band may reflect the presence of polychromates, polyvanadates, or mixed V-O-Cr oligomers, but its specific origin remains unclear. Figure 2 shows X-ray absorption near-edge spectroscopy (XANES) spectra for 10VAl, 12CrAl, 10V12CrAl, and 12Cr10VAl after treatment at 773 K for 2 h in flowing dry air and for three crystalline compounds V 2 O 5 , CrO 3 , Cr 2 O 3 .…”

Section: Resultsmentioning

confidence: 99%

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Nature, Density, and Catalytic Role of Exposed Species on Dispersed VO_x/CrO_x/Al₂O₃ Catalysts

2006

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The structure and surface composition of binary oxides consisting of CrO x and VO x dispersed on alumina and their effects on the rate and selectivity of oxidative dehydrogenation (ODH) of propane were examined and compared with those for CrO x and VO x dispersed on alumina. VO x deposition on an equivalent CrO x monolayer on alumina and deposition of CrO x on an equivalent monolayer of VO x deposited on alumina led to CrVO 4 species during thermal treatment with concomitant reduction of Cr 6+ to Cr 3+ .

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Section: Resultsmentioning

confidence: 99%

“…Crystalline CrVO 4 -I was identified by comparison with literature XRD patterns. 39 2.2. Catalyst Characterization.…”

Section: Introductionmentioning

confidence: 99%

Nature, Density, and Catalytic Role of Exposed Species on Dispersed VO_x/CrO_x/Al₂O₃ Catalysts

2006

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“…The two phases have the same chemical composition but different crystalline structures Figure 5. The new metastable phase has shown good catalytic properties especially when it is mixed with other metals (Song et al, 2002;Shishido et al, 2003;Song et al, 2003;Zhaoxia et al, 2001). Similar to the chromium vanadate system a new metastable phase was also found on the indium vanadate system Touboul et al, 1994).…”

Section: Preparation Of Metastable Phasementioning

confidence: 99%

Soft Chemistry Routes to New Nanosize Materials

Melghit

2007

SQU Journal for Science

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The old classical method for preparing inorganic materials is by the ceramic route or solid state reaction. It consists of mixing the starting materials at an elevated temperature. This method has been used for preparing numerous new materials until today. Three decades ago, the materials science community was aware of soft chemistry synthesis or chimie douce, especially with the emergence of nanotechnology field. Instead of the classical method, which involves high temperature, soft chemistry techniques use lower temperatures. In general, starting materials are dissolved in a liquid phase and different parameters such as pH, temperature and reaction time are adjusted in order to obtain the desired product. By using a lower temperature of preparation, the product obtained shows nanosize particles, with sizes lower than 100 nanometers. In contrast, the ceramic route (or solid state reaction) using higher temperatures leads to bigger particles size that are out of the nanosize range. Also, some interesting phases that are not stable at elevated temperatures (named metastable phases) and are not accessible by the classical method, are now prepared by the soft chemistry technique. Usually these metastable phases have interesting structural features and important physical properties. Adding to that, the product is obtained with a higher level of purity.

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“…A totally replaced CrPO4 showed only an amorphous phase even after the calcination at 973 K (i). Different hydrates of CrPO4 are known 52) ; their calcinations at high temperature allow the anhydrous material to be formed in two types of their polymorphic forms: β-CrPO4 above 1273 K and α-CrPO4 above 1448 K. Thus, amorphous CrPO4 is stable and does not crystallize even at high temperature of 1173 K in the DTA curves 25) . FT-IR spectra of CrV1-xPxO4 well correlated with the results of XRD analyses.…”

Section: Crv1 _ Xpxo4 Catalystsmentioning

confidence: 99%

“…A sharp exothermic peak was observed at 810 K with CrVO4 by differential thermal analysis (DTA) 25) and was assigned to the crystallization of CrVO4-I by Touboul and Melghit 27) . In the case of CrV1-xPxO4, the crystallization to the CrVO4-I structure during calcination was clearly observed and those two typical examples, i.e., CrV0.95P0.05O4 and CrV0.75P0.25O4, are shown in Fig.…”

Section: Crv1 _ Xpxo4 Catalystsmentioning

confidence: 99%

Preparation of Crystalline CrVO<sub>4</sub> Catalyst by Soft Chemistry Technique and Application for Vapor-phase Oxidation of Picolines

Shishido

2011

J. Jpn. Petrol. Inst.

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A series of Cr _ V mixed oxide catalysts (CrVO4, Cr1-xAlxVO4 and CrV1-xPxO4) have been prepared by "soft chemistry" technique. By mixing the aqueous solution of the raw materials and controlling the pH value, chromium vanadates (CrVO4-I and III) were prepared as the pure orthovanadate crystalline form. Prepared chromium vanadates were employed in the vapor phase oxidation of 2-, 3-, and 4-picolines in order to investigate the relationship between the catalysis and structure of chromium vanadate. CrVO4-I (monoclinic) showed much higher activity than CrVO4-III (orthorhombic), suggesting that the bridging oxygen in the V _ O _ Cr bond is responsible for the catalytic activity. When a part of Cr or V was replaced with Al or P without changing the CrVO4-I type structure, the activities were enhanced. The acidity increased by the replacement of Cr with Al and V with P in CrVO4-I, resulting in the accelerating desorption of products. A partial replacement of V with P significantly improved activity and this is probably due to the modification of the redox properties of V _ O _ Cr site in addition to the accelerating desorption of products. An addition of large amount of steam in the reactants improved the yield of desired products. Both Lewis and Brønsted acid sites were detected on the surface of CrV0.95P0.05O4, and the number of the latter increased by the addition of steam. The enhanced activity by the addition of steam is interpreted by the fact that Brønsted acid sites are produced by the hydrolysis of V _ O _ Cr bond on the surface and activate picoline molecules by withdrawing the electrons of the pyridine ring, and at the same time, enable to accelerate the desorption of the acid products. Even in the absence of gaseous oxygen, the oxygenated products were formed, thus, a Mars and van Krevelen mechanism was suggested. KeywordsChromium vanadate catalyst, Soft chemistry, Picoline, Vapor phase oxidation, Brønsted acid site, Mars and van Krevelen mechanism viewed 21) recently. Shishido and co-workers have reported that CrVO4 prepared by "soft chemistry" technique in the pure crystalline form (CrVO4-I, monoclinic) is also active for the vapor phase oxidation of picolines 22)～26) . In this article, the characterization of Cr _ V mixed oxide catalysts by using XRD, FT-IR, TG-DTA, NH3-TPD, Raman, and TPR techniques, and their catalysis in vapor phase oxidations of 2-, 3-and 4-picolines are demonstrated. The correlation between surface structure and catalytic behavior of a series of Cr _ V mixed oxide catalysts prepared by "soft chemistry" technique are briefly reviewed. Experimental 1. Catalyst PreparationA series of CrVO4, Cr1-xAlxVO4 (x 0.25, 0.5, 0.75 and 1.0) and CrV1-xPxO4 (x 0.02-1.00) catalysts were prepared following method proposed by Touboul and co-workers 27),28) . Aqueous solutions of NH4VO3, Cr(NO3)3 9H2O, Al(NO3)3 9H2O and NH4H2PO4 were mixed and the pH value of the solution was lowered below 1.0 to form homogeneous solution by adding 3 M (1 M 1 mol ・dm -3 ) nitric acid. Then, the pH value of the solution...

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Crystalline CrV0.95P0.05O4 catalyst for vapor-phase oxidation of picolines

Abstract: CrV0.95P0.05O4 prepared as a pure crystalline form was found to be highly active for the vapor-phase oxidation of picolines to the corresponding aldehydes and acids in the presence of water.

Cited by 12 publications

References 13 publications

Nature, Density, and Catalytic Role of Exposed Species on Dispersed VO_x/CrO_x/Al₂O₃ Catalysts

Nature, Density, and Catalytic Role of Exposed Species on Dispersed VO_x/CrO_x/Al₂O₃ Catalysts

Soft Chemistry Routes to New Nanosize Materials

Preparation of Crystalline CrVO<sub>4</sub> Catalyst by Soft Chemistry Technique and Application for Vapor-phase Oxidation of Picolines

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Crystalline CrV0.95P0.05O4 catalyst for vapor-phase oxidation of picolines

Abstract: CrV0.95P0.05O4 prepared as a pure crystalline form was found to be highly active for the vapor-phase oxidation of picolines to the corresponding aldehydes and acids in the presence of water.

Cited by 12 publications

References 13 publications

Nature, Density, and Catalytic Role of Exposed Species on Dispersed VOx/CrOx/Al2O3 Catalysts

Nature, Density, and Catalytic Role of Exposed Species on Dispersed VOx/CrOx/Al2O3 Catalysts

Soft Chemistry Routes to New Nanosize Materials

Preparation of Crystalline CrVO<sub>4</sub> Catalyst by Soft Chemistry Technique and Application for Vapor-phase Oxidation of Picolines

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Nature, Density, and Catalytic Role of Exposed Species on Dispersed VO_x/CrO_x/Al₂O₃ Catalysts

Nature, Density, and Catalytic Role of Exposed Species on Dispersed VO_x/CrO_x/Al₂O₃ Catalysts