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1.
Effects of Cs +, H + and Cu 2+ counterions in the vanadium containing heteropoly compounds Cs xH 1-xVO[PMo 12O 40] and Cs yH 0.5-yCu 0.25VO[PMo 12O 40] on the catalytic oxidation of isobutane and characterization by TGA, IR and ESR spectroscopies are reported. A high selectivity of 76% for methacrylic acid and methacrolein together has been obtained with Cs 0.75H 0.25VO[PMo 12O 40] catalysts at a reactivity of 5.3x10 -1 mmol/h cm 3. 相似文献
2.
A route for the synthesis of hybrid materials using multiwalled carbon nanotubes (MWCNTS) and Cs 3PMo 12O 40 was confirmed. The Cs 3PMo 12O 40 salt was synthesized from H 3PMo 12O 40·14H 2O and CsCl. All compounds were characterized by Raman spectroscopy. The synthesis method can produce a chemically stable Cs 3PMo 12O 40 molecule and pure and oxidized MWCNTS. Raman spectroscopy showed that the chemical interaction between MWCNTS and Cs 3PMo 12O 40 was essentially of electrostatic nature. Raman spectra obtained with different wavelengths showed thermal decomposition of H 3PMo 12O 40·14H 2O (raw materials) from laser heating process. On the contrary, the synthesized compound (i.e. Cs 3PMo 12O 40) was stable under the experimental conditions. 相似文献
3.
Recent progress on the catalytic decomposition of lignin model compounds to aromatics was reported in this review. Cesium-exchanged heteropolyacid catalysts (Cs xH 3.0?xPW 12O 40), palladium catalysts supported on cesium-exchanged heteropolyacid (Pd/Cs xH 3.0?xPW 12O 40), and palladium catalysts supported on various activated carbon aerogels (ACAs) (Pd/ACA-SO 3H (X), Pd/XCs 2.5H 0.5PW 12O 40/ACA, Pd/Cs xH 3.0?xPW 12O 40/ACA, and Pd/Cs 2.5H 0.5PW 12O 40/ACA-SO 3H) were prepared, and they were employed for the decomposition of C–O bond in lignin to aromatics. Phenethyl phenyl ether, benzyl phenyl ether, and 4-phenoxyphenol were used as dimeric lignin model compounds representing for β-O-4, α-O-4, and 4-O-5 bonds in lignin, respectively. It was observed that Cs xH 3.0?xPW 12O 40 and Pd/Cs xH 3.0?xPW 12O 40 were highly active for the decomposition of phenethyl phenyl ether and benzyl phenyl ether to aromatics. However, these catalysts showed very low catalytic performance in the decomposition of 4-phenoxyphenol. Palladium catalysts supported on various ACAs (Pd/ACA-SO 3H (X), Pd/XCs 2.5H 0.5PW 12O 40/ACA, Pd/Cs xH 3.0?xPW 12O 40/ACA, and Pd/XCs 2.5H 0.5PW 12O 40/ACA-SO 3H) were efficient for the decomposition of 4-phenoxyphenol to aromatics. Acidity of the catalysts played a key role in determining the catalytic performance in the decomposition of 4-phenoxyphenol to aromatics. 相似文献
4.
Summary UV-visible spectroscopic studies of solid H 3PMo 12O 40were carried out to elucidate the effect of crystalline water molecules, and in turn, to provide a guideline for utilizing
UV-visible spectra of solids to probe reduction potentials of HPA catalysts. UV-visible spectra of reduced/reoxidized H 3PMo 12O 40were also measured to check the possibility of utilizing UV-visible spectroscopy as a probe of reduction/oxidation states
of H 3PMo 12O 40catalyst. Absorption edges of solid H 3PMo 12O 40 shifted to longer wavelength with heating to decrease the number of crystalline water molecules. It was also revealed that
UV-visible spectra of the H 3PMo 12O 40catalyst varied in a systematic way depending on the reduction/oxidation states of the H 3PMo 12O 40catalyst.</o:p> 相似文献
5.
H 3PMo 12O 40-polysulfone and H 3PMo 12O 40-polyphenylene oxide composite film catalysts were prepared by a membrane preparation technique. They showed the higher catalytic activities than H 3PMo 12O 40 in the vapor-phase synthesis of ethyl tert-butyl ether. 相似文献
6.
Polyaniline(PAN) supported H 6P 2W 18O 62(PW) , H 3PMo 12O 40 (PMo) and H 4PMo 11VO 40(PMoV) catalysts were prepared and their activities for hexanol conversion were tested. IR, XRD, ICP and SEM measurements
proved that the heteropolyacids (HPA) could be supported on this type of polymer. The PAN supported HPA catalysts exhibit
higher redox activities and low acid-base activities for the hexanol conversion. The redox activities increase with increasing
amount of the heteropolyacid. Substitution of Mo ion by V ion results in an increase of redox activities of the catalysts.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
7.
A series of studies of hydrocarbon oxidation by the O 2 + H 2 mixture in the presence of catalytic systems based on Pt or Pd and a heteropoly compound (HPC) is reviewed. The catalytic systems were prepared from Pd(II) complexes with the heteropoly tungstate anions PW 11O 29 7? and PW 9O 34 9? , the complex salt [Pt(NH 3) 4][H 2Mo 12O 40] 2 · 7H 2O, mixtures of H 2PtCl 4 or H 2PtCl 6 with H 3 + n PMo 12 ? n V n O 40 ( n = 0–3) heteropoly acids, or supported platinum dispersed in HPC solutions. The interaction of metal ions and particles with HPCs in the initial state and after thermal and redox treatments was investigated by NMR, IR spectroscopy, XPS, EXAFS, HREM, and TPR. The catalytic systems were tested in the liquid-phase oxidation of alkanes, cyclohexane, cycloalkenes, benzene, toluene, and phenol with the O 2 + H 2 mixture at low temperatures. Effective supported catalysts based on platinum nanoparticles associated with the redox-active HPCs H 3PMo 12O 40 and H 4PMo 11VO 40 were prepared for gas-phase benzene oxidation into phenol. The oxidation mechanism includes the interaction between dioxygen and platinum (or palladium) and the participation of the HPC in the formation of active oxygen species of radical nature. 相似文献
8.
HDS catalysts were prepared by loading H 3PMo 12O 40 or H 4PMo 11V 1O 40 polyoxometallates on TiO 2 (0.5 and 1.0 mmol (Mo+V)). Activity of the catalysts was tested in the HDS of thiophene. The activity of catalysts of low
concentration was 2–3 times higher than the activity of those of high concentration. Temperature programmed reduction (TPR)
and IR spectroscopy were used to determine the properties of the catalyst. TPR measurements proved that vanadium promotes
and stabilizes HDS activity due to an increase in the Mo 5+/Mo 4+ ratio. 相似文献
9.
A series of Cs 2Te 0.2H 0.6 + x PMo 12 − x V x O n ( x = 0–3) heteropoly compounds has been prepared and tested in the partial oxidation of isobutane. Catalytic tests show that at 350°C very high selectivity to methacrylic acid (60.1%) can be achieved at isobutane conversion of 12.2% over a Cs 2.0Te 0.2H 1.6PMo 11VO n catalyst with only one molybdenum atom per unit cell substituted by vanadium. The presence of Te 4+ in the heteropoly compounds appears to interfere with the dehydrqgenation step and favor the formation of methacrolein and methacrylic acid. 相似文献
10.
Boehmite nano‐particles with a high degree of surface hydroxyl groups were covalently functionalized by 3‐(trimethoxysilyl)‐propylamine to support H 3[PMo 12O 40], H 3[PW 12O 40], H 4[SiMo 12O 40] and H 4[SiW 12O 40] Keggin‐type heteropolyacids. After characterization of these catalysts by FT‐IR, powder X‐ray diffraction, TG/differential thermal analysis, CHN, inductively coupled plasma and transmission electron microscopy techniques, they were applied to the epoxidation of cis‐cycloocten. The progress of the reactions was investigated by gas–liquid chromatography, and the catalytic procedures were optimized for the parameters involved, such as the solvent and oxidant. The results showed that 25 mg of supported H 3[PMo 12O 40] catalyst in 1 ml C 2H 4Cl 2 with 0.5 mmol cyclooctene and 1 mmol tert‐butylhydroperoxide at reflux temperature gave 98% yield over 15 min. Recycling experiments revealed that these nanocatalysts could be repeatedly applied up to five times for a nearly complete epoxidation of cis‐cycloocten. The optimized experimental conditions were also used successfully for the epoxidation of some other alkenes, such as cyclohexene, styrene and α‐methyl styrene. 相似文献
11.
A facile and efficient method for the formation of 3,4-dihydro-1H-2,3-benzothiazine 2,2-dioxides 2, compounds from benzylsulfonamides and formaldehyde is described using heteropolyacids H 3PW 12O 40 and H 3PMo 12O 40 supported on silica as catalysts. 相似文献
12.
Keggin-type molybdovanadophosphoric acids(HPA),H_4PMo_(11)VO_(40)(1),H_5PMo_(10)V_2O_(40)(2)and H_6PMo_9V_3O_(40)(3)were anchored onto γ-aminopropyltriethoxysilane(APTS)aminosilylated silica mesoporous SBA-15 throughacid-base neutralization and the resulting HPA/APTS/SBA-15 were characterized by BET,TEM,XRD,ICP,FTIRand ~(31)P MAS NMR.The characterization results indicate that the Keggin-structure of these HPAs is preservedwithin the mesoporous silica host.The samples were tested for catalytic aerobic oxidation of acetaldehyde hetero-geneously in liquid phase under ambient condition.The electrostatic force between heteropoly acid and aminogroups grafted on the silica channel surface leads to strong immobilization of HPA inside SBA-15 which is againstthe leaching during the reaction.The good catalytic performance and easy recycle of these catalysts make them aspotential environmental friendly catalysts for elimination of indoor air pollutants. 相似文献
13.
Acid salts Cs x H 3 + n ? x PMo 12 ? n V n O 40 ( n = 0, 1, 2, or 3; x = 2.5 or 3.5) with coprecipitated or supported platinum were studied using thermogravimetry, IR spectroscopy, and temperature-programmed reduction. The thermal region of the full stability of these salts is limited by the decomposition temperature of the corresponding acid H 3PMo 12O 40 (~400°C) or H 3 + n PMo 12 ? n V n O 40 (~300–350°C). The degree of reduction of heteropoly anions with hydrogen is regulated by temperature. Deeply reduced heteropoly anions (at 300°C) are slowly oxidized with oxygen with structure and composition regeneration. The states of molybdenum and vanadium on the surface of samples with coprecipitated platinum Pt 0.1-Cs 2.5H 0.5PMo 12O 40 ( 1) and Pt 0.1-Cs 2.5H 2.5PMo 10V 2O 40 ( 2), which were studied using XPS, correspond to reduced or reoxidized heteropoly anions in the bulk. Platinum metal particles of ~5 nm in size were observed in high-resolution TEM images obtained after the reduction and storage of sample 1 in air. A heteropoly compound forms two texture levels: spherical nanoparticles of 10–20 nm in size are collected in closely packed globules of 100–300 nm in size. Detailed texture studies, which were performed using nitrogen adsorption isotherms, demonstrated texture mobility under the ambient conditions. The cesium salts of the heteropoly acids were tested in the gas-phase oxidation of benzene to phenol with an O 2 + H 2 mixture at 180°. The effect of platinum concentration on the specific catalytic activity in the presence of deeply reduced heteropoly anions was monitored. The samples containing the salt Cs 2.5H 0.5PMo 12O 40 exhibited the highest activity in the formation of phenol. The introduction of vanadium into the heteropoly anion impaired the catalytic performance of both deeply and slightly reduced samples. 相似文献
14.
Summary. Acetylation of primary, secondary, and tertiary alcohols was carried out in some refluxing alkyl acetates and in two carboxylic
acids with the participation of catalytic amounts of H 3PW 12O 40, H 3PMo 12O 40, and H 14P 5W 30O 110 with good yields and high stereo(regio)specificity under mild reaction condition. H 3PW 12O 40 and H 3PMo 12O 40 have also shown excellent reactivity in the formylation of 1-butanol with ethyl formate at room temperature and in short
reaction times. Heteropolyacid catalysts could be separated after a simple work up and reused for several times. 相似文献
15.
The Keggin-structured heteropolyacid H 4PMo 11VO 40 and its triethylamine-modified derivative [(C 2H 5) 3NH] 4PMo 11VO 40 were prepared and characterized by FT-IR and UV–visible spectrometry, and elemental analysis. Direct hydroxylation of benzene to phenol by H 2O 2 over these two catalysts was then compared. The effect of the triethylamine in [(C 2H 5) 3NH] 4PMo 11VO 40 on the catalytic hydroxylation of benzene was investigated in detail. The results showed that although the triethylamine-modified catalyst is not significantly more active than the parent heteropolyacid catalyst, its reaction-controlled phase-transfer characteristics enable easy separation of the catalyst from the reaction medium, and its reuse, suggesting its potential for application to the hydroxylation of benzene to phenol with H 2O 2. 相似文献
16.
One-pot three-component synthesis of twelve different chromeno[2,3-b]indole derivatives were achieved by the condensation of β-naphthol, oxindole and various substituted aldehydes. Two more chromeno[2,3-b]indole derivatives were also synthesized through one-pot two-component condensation of salicylaldehyde with oxindole/chlorooxindole. Both the condensations were achieved by using Keggin-type heteropoly-11-molybdo-1-vanadophosphoric acid, H4[PVMo11O40] supported on montmorillonite K-10 clay for about 10% as catalyst under environmentally benign solvent-free reaction condition. Shorter reaction time, excellent yield of product, sustainability of catalytic material and simple workup procedure under green experimental conditions are the advantages of this protocol. 相似文献
17.
Heteropoly acids of the general formula H 3+x[PMo 12-xV xO 40] (where x = 1,2,3) catalyzed the oxidation of aromatic hydrocarbons at 65°C with H 2O 2 to give oxygenated products. Among the catalysts, H 4[PMo 11VO 40] was found to be a more active catalyst and its activities have been reported in the oxidation of cyclohexane, methyl cyclohexane, naphthalene, 1-methyl naphthalene and biphenyl. 相似文献
18.
Summary Thiophene conversion on, and Mössbauer spectra of sulfided FePMo/TiO 2 catalysts prepared using H 3PMo 12O 40 and its Fe salt have been studied. Iron and phosphorus promoting effect on catalytic activity of the HDS catalysts is discussed. 相似文献
19.
Deposited catalysts composition H 3PMo 12O 40/SiO 2 and Ag/H 3PMo 12O 40/SiO 2 have been synthesized on the basis of fumed silica, including milling technique. Physical–chemical characteristics of prepared
catalysts have been studied by means of XRD, DTA-TG, FTIR, UV–Vis spectroscopy, and adsorption of nitrogen. Catalysts possess
meso- or meso-macroporous structure and contain deposited Keggin heteropolycompounds. Deposition of heteropolycompounds on
support with high specific surface area results in increase of selectivity to epoxide in epoxidation reactions. The use of
milling during catalyst synthesis leads to further growth of selectivity of epoxides formation. 相似文献
20.
For ultra-deep desulfurization of diesel fuel, this study applied the ultrasound-assisted catalytic ozonation process to the dibenzothiophene (DBT) removal process with four Keggin-type heteropolyacids (HPA) as catalysts and acetonitrile as extractant. Through experimental evaluations, H 3PMo 12O 40 was found to be the most effective catalyst for the oxidative removal of DBT. Under favorable operating conditions with a temperature of 0 °C, H 3PMo 12O 40 dosage of 2.5 wt.% of n-octane, and ultrasonic irradiation, DBT can be effectively removed from simulated diesel. Moreover, the reused catalyst exhibited good catalytic activity in recovery experiments. This desulfurization process has high potential for ultra-deep desulfurization of diesel. 相似文献
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