Oxidation of propane over substituted Keggin phosphomolybdate salts

Ammonium salts, （NH4）6HPMo11MO40 （M = Ni, Co, Fe）, have been investigated for the oxidation of propane, with molecular oxygen, at temperature ranging between 380 ℃ and 420 ℃ after in-situ pre-treatment performed at two heating rate of 5 or 9 ℃/min. They were characterized by BET method, XRD, 31p NMR, UV-Vis and IR techniques. The catalysts were found active in the propane oxidation and selective to propene or acrolein, in particular for samples pre-treated with the heating rate of 9 ℃/min.

Oxidation of propane over ammonium-transition metal mixed keggin phosphomolybdate salts

Mixed ammonium-transition metal salts with formula of （NH4）xMyHzPMo12O40 （M = Ni^2＋, Co^2＋ or Fe ^3＋） denoted as MPMo12 have been investigated for the oxidation of propane, with molecular oxygen, at temperature range between 380 ℃ and 420 ℃ after in-situ pre-treatment performed at two heating rate of 5 or 9℃/min. They were characterized by BET method, XRD, UV-Vis and IR techniques. The catalysts were found to be active in the propane oxidation and selective to propene or acrolein, in particular for samples pre-treated with the heating rate of 9℃/min. FePMo12 was found to be a more active catalyst for propene （17.2% yield） with minimal over deep oxidation （0.3% yield in COx）.

Hydrothermal Synthesis, Crystal Structure and Property of a Novel Inorganic-organic Hybrid Compound Based on Phosphomolybdate Anion [H-IDP]_4[PMo_(12)O_(40)]·8H_2O (IDP = 4-(Imidazole-1-yl)phenol)

A novel compound [H-IDP]4[PMo12O40]·8H2O 1 based on Keggin-type phosphor- molybdate has been synthesized by hydrothermal method and characterized by IR spectroscopy, elemental analyses and single-crystal X-ray diffraction. The composite crystallizes in the mono- clinic system, space group C2/m with a = 13.937（5）, b = 27.033（5）, c = 10.857（5） A, β = 122.489（5）°, V = 3450（2）A^3, Mr = 2611.11, Z = 2, Dc = 2.498 g/cm^3, F（000） = 2486,μ = 2.243 mm^-1, the final R = 0.0568 and wR = 0.1216 for 2707 observed reflections with I 〉 2σ（I）. X-ray structural study shows that 1 consists of a [PMo12O40]^4- polyanion, four protonated IDP cations and eight H2O molecules. In the structure of 1, a 3D network forms by hydrogen bond of [PMo12O40]^4- polyanion, HIDP^＋ cation and H2O molecules. Upon excitation wavelength of 280 nrn in hydroxylic solvents at room temperature, 1 shows fluorescence property.

Hydroisomerization of n-heptane on Pt promoted phosphomolybdate catalysts

Phospbomolybdate （PMo） with varying Mo loadings ranging from 5-30 wt% on alumina were prepared by incipient wetness impregnation method. 0.5 wt% of Pt was further loaded in order to prepare the bifunctional （metal-acid） Pt-PMo/Al2O3 catalysts. Thus prepared catalysts showed very high catalytic activities for n-heptane hydroisomerization compared with Pt impregnated MoO3 catalysts supported either on Al2O3 or on AIPO4. The conversion of n-heptane increased with Mo loading up to 20 wt% and slightly decreased with further Mo loading. However, the selectivity towards isomers showed an increasing trend up to 30 wt% of Mo in the catalyst. A relationship between catalytic activity and acidic strength was established in the present study.

Conjugated organic component-functionalized hourglass-type phosphomolybdates for visible-light photocatalytic Cr(VI)reduction in wide pH range

Abstra ct Utilizing efficient and durable photocatalysts for the removal of carcinogen Cr(Ⅵ)in wide pH water environment is of great significance for environment remediation.Herein,three conjugated organic component-functionalized hourglass-type phosphomolybdate hybrids with the formulas(H_(2)DBQ)[Fe(-H_(2)O)_(3)]_(2){Fe[P_(4)Mo_(6)0_(31)H_(7)]_(2)}·7H_(2)O(1),(H_(2)DBQ)_(2)(H_(2)DBP)[Fe(H_(2)O)_(4)]{Fe[P_(4)Mo_(6)O_(31)H_(7)]_(2)}·4H_(2)O(2),(H_(2)DBP)_(2){Fe[P_(4-)Mo_(6)O_(31)H_(9)]_(2)}·10H_(2)O(3)(DBQ=2,2'-dimehyl-6,6'-biquinoline;DBP=4,4'-diaminobiphenyl)were synthesized via hydrothermal method as photocatalysts for reducing Cr(Ⅵ)under visible light illumination.Structure analysis showed that hybrids 1-3 consist of hourglass-type[Fe(P_(4)Mo_(6)O_(31)H_(6))_(2)]^(10)-(abbr.Fe{P_(4)Mo_(6)}_(2))poly anionic clusters functionalized with different proportional of conjugated organic components(DBQ and DBP)effectively regulated their visible-light absorption capabilities and electron structures,which could be employed to reflect the structure-activity relationship of materials.When used as catalysts for reducing Cr(Ⅵ),hybrids 1-3 displayed distinct photocatalytic activities with Cr(Ⅵ)removal efficiencies of 91%,86%and 81%with only 10 W of white light being used as illumination,which are superior to that of pristine Fe{P_(4)Mo_(6)}_(2) salt(62%).Moreover,hybrid 1 also maintained high Cr(Ⅵ)removal efficiencies above~85%and high structural stabilities in solutions with wide pH ranges of2.5-10.0.Mechanism investigation showed that the higher organic component conjugation levels could promote the optic al absorption and facilitate the electron transfer between Fe{P_(4)Mo_(6)}_(2) and org anic components,thus resulting in effective Cr(Ⅵ)reduction photocatalytic efficacy.This work provides a viable way to design the photocatalysts based on polyoxometalates for removing wastewater pollutants.

Hydrothermal Synthesis, Structure and Properties of a New Phosphomolybdate Based on Novel [Co（H2O）4（HP2Mo5O23）]8 Anions and [H8（H2O）16]8＋ Water Cluster Cations

A pure inorganic {P2MO5O23}6- based cobalt complex [Hs（H2O）16][Co（H2O）4（HP2Mo5O23）2] with a sandglass4ike shape was synthesized and characterized by means of single-crystal X-ray diffraction, powder X-ray diffraction（PXRD）, infrared spectroscopy（IR）, thermogravimetry/differential scanning calorimetry（TG/DSC）, ultraviolet-visible spectroscopy（UV-Vis） and cyclic voltammogram（CV）. Single-crystal X-ray diffraction analysis reveals that the asymmetric unit of compound 1 consists of a half cobalt ion, one {P2M05O23}6- anion, two coordinated water molecules and eight lattice water molecules. It is especially intriguing to note that two {P2Mo5O23}6- clusters are symmetrical about the Co ion, like a sandglass. And a chair-like water cluster with an unprecedented centrosymmetric [Hs（H2O）16]8＋ can be observed in compound 1. Additionally, the electrochemical and catalytic properties of compound I were also investigated.

Insight into the Alkali Resistance Mechanism of CoMnHPMo Catalyst for NH_(3) Selective Catalytic Reduction of NO

The existence of alkali metals in fl ue gases originating from stationary sources can result in catalyst deactivation in the low-temperature selective catalytic reduction(SCR)of nitrogen oxides(NO_(x)).It is widely accepted that alkali metal poisoning causes damage to the acidic sites of catalysts.Therefore,in this study,a series of CoMn catalysts doped with heteropolyacids(HPAs)were prepared using the coprecipitation method.Among these,CoMnHPMo exhibited superior catalytic performance for SCR and over 95%NO_(x) conversion at 150-300.Moreover,it exhibited excellent catalytic activity and stability after alkali poisoning,demonstrating outstanding alkali metal resistance.The characterization indicated that HPMo increased the specifi c surface area of the catalyst,which provided abundant adsorption sites for NO_(x) and NH_(3).Comparing catalysts before and after poisoning,CoMnHPMo enhanced its alkali metal resistance by sacrifi cing Brønsted acid sites to protect its Lewis acid sites.In situ DRIFTS was used to study the reaction pathways of the catalysts.The results showed that CoMnHPMo maintained high NH_(3) adsorption capacity after K poisoning and then reacted rapidly with NO intermediates to ensure that the active sites were not covered.Consequently,SCR performance was ensured even after alkali metal poisoning.In sum-mary,this research proposed a simple method for the design of an alkali-resistant NH_(3)-SCR catalyst with high activity at low temperatures.

Synthesis of Pt/PMA-MIL-101 Catalyst and Its Performance in n-Heptane Isomerization

Hydroisomerization of n-heptane is an efficient method for producing gasoline with a high octane number.The focus of this study was to find a highly efficient catalyst that could both promote the conversion of n-heptane and inhibit the cracking side reaction.MIL-101(Cr)is a chromium-based metal-organic framework(MOF)with good hydrothermal stability,and exhibits a three-dimensional pore structure that is similar to that of zeolites.Using phosphomolybdic acid(PMA;H3PMo12O40·xH2O)can increase the number of Brønsted acid sites on MIL-101(Cr),which contributes to improving the catalytic performance during isomerization.In this study,0.4%Pt/PMA-MIL-101(Cr)catalyst was successfully crystallized at 220℃using a hydrothermal synthetic method.The results showed that the synthesized samples were mesoporousmicroporous composite materials with the typical octahedral structure,and the MIL-101(Cr)framework was not damaged following modification with PMA.It was found that 0.4%Pt30%PMA-MIL-101(Cr)exhibited the best performance for isomerization of n-heptane,with a conversion rate and selectivity at 260°C of 47.6%and 96.6%,respectively.After five hours of reaction,the conversion rate and selectivity of the catalyst remained above 38%and 80%,respectively.

Unusual hexa-nuclear cadmium cluster functionalized phosphomolybdate as effective photoelectrochemical sensor for trace Cr(Ⅵ)detection

Photo-assisted electrochemical technique provides a promising approach towards carcinogen chromium(Ⅵ)detection,which requires reasonable catalyst design.Herein,an unusual hexa-nuclear cadmium cluster functionalized reductive phosphomolybdate hybrid as photo-electrochemical sensor was designed and synthesized with formula of{[Cd(H_(2)O)_(2)]_(2)[Cd(btmbp)]_(2)}{Cd(P_(4)Mo_(6)O_(31)H_(7))_(2)}·20H_(2)O(1)(btmbp=4,4′-bis((^(1)H-1,2,4-triazol-1-yl)methyl)biphenyl),in which the photoactive hexa-nuclear{Cd_(6)}clusters cooperated with reductive phosphomolybdate[P_(4)Mo_(6)O_(31)]^(12)−endow the material with wide light absorption and remarkable redox activity,thus achieving efficient photo-assisted electrochemical Cr(Ⅵ)detection performance.Under visible-light assistance,the detection limit(LOD)and sensitivity of Cr(Ⅵ)is 4.17 nmol/L(0.225 ppb)and 226.32μA L/μmol,which is apparently superior to the performance without photo-assistance(6.25 nmol/L and 106.95μA L/μmol)and far satisfies the demands of world health organization(WHO)for potable water(50 ppb).Moreover,compound 1 showed prominent Cr(Ⅵ)detection performance in practical water samples together with remarkable anti-interference capacity and good electrochemical durability.This work provides an important guidance for designing efficient polyoxometalate-based crystalline sensors for Cr(Ⅵ)detection.

Highly Active Sulfided NiPMo Hydrodesulfurization Catalyst Prepared from Keggin-type Phosphomolybdic Acid

A highly active sulfided NiPMo/MCM-41(NiPMo-S/M41)hydrodesulfurization(HDS)catalyst was successfully synthesized using Keggin-type phosphomolybdic acid as the phosphorus and molybdenum source and thioacetamide as the sulfur source.The supported catalysts NiPMo/M41,Ni_(2)P-Mo/M41,and Ni_(2)P/M41 were also prepared to investigate the effects of Mo,S,and the Keggin structure on the HDS performance.The HDS activities of NiPMo/M41 and NiPMo-S/M41 toward dibenzothiophene were much higher than that of Ni_(2)P-Mo/M41,demonstrating that the active phases in the Keggin-structured catalysts were significantly superior to the Mo-modified Ni_(2)P phase.The HDS activities of the catalysts followed the order NiPMo-S/M41(96.7%)>NiPMo/M41(89.9%)>Ni_(2)P-Mo/M41(53.5%)>Ni_(2)P/M41(48.9%).For Ni_(2)P/M41,Ni_(2)P-Mo/M41,and NiPMo/M41,cyclohexylbenzene(CHB)was formed in low concentrations(<21.0%),indicating that direct desulfurization was the favored reaction route and that this did not change for Keggin-structured NiPMo/M41.By contrast,the CHB selectivity of NiPMo-S/M41 increased to 44.6%,much higher than that of NiPMo/M41(17.6%),demonstrating that sulfidation enhanced the hydrogenation ability,which was ascribed to a metal-acid synergistic effect.

Ultra-deep oxidative desulfurization of fuel with H_2O_2 catalyzed by phosphomolybdic acid supported on silica

A highly active catalyst of phosphomolybdic acid ~HPMo） was prepared and applied in the catalytic oxidative desulfurization （CODS） system. The catalyst was characterized by FT-IR, XRD, XPS and superconducting NMR. The influences of rn（catalyst）/m（oil）, V（H202）fV（oil）, reaction temperature and reaction time on the fractional conversion of benzothiophene （BT） and dibenzothiophene （DBT） were investigated. GC-MS and micra-coulometric methods were employed to investigate the reaction. The catalyst has high desulfurization activity in the removal of BT and DBT under mild conditions. The recycling experiments indicated that DBT and BT removal could still reach 95.2% and 95.7% after 10 cycles.

Preparation, Electrochemical Property and Application in Bulk-modified Electrode of Dawson-type Phospho-molybdate-doped Polypyrrole Composite Nanoparticles

A kind of inorganic-organic hybrid semiconductor composite nanoparticles： Dawson-type phosphomolybdate- doped polypyrrole （P2Mo18-PPy） was designed and prepared using microemulsion oxidation-polymerization at room temperature and characterized by TEM and IR. The P2Mo18-PPy was used as a bulk-modifier to fabricate a chemically modified carbon paste electrode（CPE） by direct mixing, which represents the example of polyoxometalates（ POMs）- doped semiconductor polymer nanoparticles modified electrode. Both the advantage of POMs-doped polymer and the surface-renewal property of the CPE were fully utilized. The electrochemical behavior of the P2Mo18-PPY bulk-modified CPE（P2Mo18-PPy-CPE） was investigated with cyclic voltammetry. Three couples of reversible redox peaks were observed in the range from ＋ 800 to 0 mV, which corresponded to the reduction and oxidation through two-, four- and six-electron processes, respectively. The P2 Mo18-PPY-CPE showed a high electrocatalytic activity for the reduction of nitrite, which expanded the application of POMs-doped semiconductor polymer nanoparticles.

Oxidation Reactivities of Organic Sulfur Compounds in Fuel Oil Using Immobilized Heteropoly Acid as Catalyst

Heteropoly acid of Keggin structure phosphotungstic（HPW） and phosphomolybdic（HPMo） were chemically anchored to the modified SBA-15 channel. The materials were used as catalyst for oxidative desulfurization of organic sulfur compounds including benzothiophene （BT）, dibenzothiophene （DBT） and 4,6-dimethydibenzothiophene （4,6-DMDBT）. The experimental results show that the catalysts are efficient and reusable, the catalytic activity is hardly reduced even in the 5th cycle of use.

Synthesis,Characterization and Catalytic Properties of Mesoporous HPMo/SiO_2 Composite

A novel mesoporous HPMo/SiO2 composite was synthesized by the sol-gel method with triblock copolymer EO20PO70EO20 as template.The properties of the product were characterized by X-ray diffraction,transmission electron microscopy,N2 adsorption-desorption isotherms,Fourier transform infrared spectrometer and inductively-coupled plasma analysis.The experimental results show that the product has a very ordered hexagonal mesostructure,and the HPMo is immobilized into the framework of silica.The final mesoporous composite shows excellent stability in polar solvents.Results of catalytic tests indicate that the composite is an effective catalyst for oxidation of dibenzothiophen,and there are few activity losses even after the third cycle of uses.The high catalytic activity and good insolubility make it a promising catalyst in oxidative desulfurization process.

SYNTHESIS AND CHARACTERIZATION OF HYBRID PROTON CONDUCTING MEMBRANES OF POLY(VINYL ALCOHOL) AND PHOSPHOMOLYBDIC ACID

Hybrid proton conducting membranes of poly（vinyl alcohol） （PVA） and phosphomolybdic acid （PMA） were prepared by solution casting method. The effect of PMA doping and PVA crosslinking density on the membrane properties and proton conductivity were investigated. The crosslinking reaction between the hydroxyl group of PVA and the aldehyde group of glutaraldehyde （GA） was characterized by IR spectroscopy. Proton conductivity of the membranes increases with an increase in concentration of the doped PMA and also with an increase in crosslinking density of the membranes. Proton conductivity results indicate that a significant amount of PMA was maintained in the membranes even after several hours of immersion in water. A maximum conductivity of 0.0101 S cm^-1 was obtained for the membrane with 33.3 wt% PMA and crosslinking density of 5.825 mol%. X-ray diffraction studies were carried out to investigate the influence of PMA doping and crosslinking density on the nature of the membranes. These properties make them very good candidates for polymer electrolyte membranes for direct methanol fuel cell application.

Oxidative Desulfurization of Model Sulfur Compound by Potassium Ferrate in the Presence of Phosphomolybdic Acid Catalyst

In this work, the removal of thiophene from simulated oil has been studied by using the adsorption, extraction and oxidation/adsorption methods, respectively. In the adsorptive desulfurization process, different commercial adsorbents were used to eliminate thiophene at ambient pressure and mild temperature, and the results showed that carbon powder had the best adsorption ability. In the extractive desulfurization process, the best desulfurization result was obtained when DMF is used. In the oxidative/adsorptive desulfurization procedure using synthesized potassium ferrate as the oxidant and phosphomolybdic acid solution as the catalyst, thiophene was oxidized and removed from hydrocarbons in combination with active carbon adsorption, and the residual sulfur content of simulated oil could be reduced to 15.3mg/L from the original level of 200mg/L, with the desulfurization rate reaching 92.3%.

Molecularly imprinted sensor based on carboxylated carbon nanotubes/Keggin-type polyoxometalates nanocomposite for the detection of furazolidone

Due to its properties of mutagenic,teratogenic,and carcinogenic,the detection of furazolidone(FZD)in aquaculture is of great importance for food safety and human health.In this study,molecularly imprinted fi lms modifi ed with carboxylated multi-walled carbon nanotube-phosphomolybdic acid composite were used to fabricate an electrochemical sensor for the determination of FZD.The nanocomposites were characterized using infrared spectroscopy,scanning electron microscopy,energy-dispersive X-ray spectroscopy,and X-ray diff raction.The electrochemical characteristics of the modifi ed electrodes were examined using electrochemical impedance spectroscopy,cyclic voltammetry,and diff erential pulse voltammetry.The sensor exhibited exceptional catalytic performance.The calibration curves were acquired in the concentration range of 6 nmol·L^(−1)to 0.6μmol·L^(−1),with a limit of detection of 3.38 nmol·L^(−1).Additionally,the sensor proved successful in recognizing FZD in shrimp samples with satisfactory recoveries and precision.The method provides a strategy to construct a molecularly imprinted electrochemical sensing platform using nanomaterials,which has great promise in the field of food safety.

A Simple and Novel Electrochemical Sensor Based on Phosphomolybdic-Polypyrrole Film Modified Electrode for Highly Sensitive Detection of Cholic Acid

A simpe electrochemical sensor for detection of cholic acid （CA） was designed by modifying phosphomolybdate （PMol2） doped polypyrrole （PPy） film on glassy carbon electrode （PMo12-PPy/GCE）. The electrochemical behavior of CA on PMo12-PPy/GCE was investigated by cyclic voltammetry and 0.5 order differential voltammetry. The results indicated that CA had high inhibitory activity toward the peak currents of PMo12-PPy/GCE. The reduction peak currents were linearly related to the logarithmic value of the concentration of CA from 1.0 × 10^- 7 to 1.0 × 10^-3 mol/L with a low detection limit of 1.0 × 10^- 8 mol/L. The developed sensor exhibited excellent sensitivity, selectivity and stability for detection of CA, and it could be successfully applied to detect the level of CA in the urine samples. Moreover, the response mechanism of CA on the PMo12-PPy/GCE was discussed in detail.

Electrochemical detection of cell concentration based on reaction of DNA with molybdate

This article describes a fast and simple electrochemical assay for detecting cell concentration.After cell death,the membrane of cells will be broken,and DNA molecules contained in the cells will be released,but this does not happen in living cells.Sodium molybdate can react with the phosphate backbone of the released DNA molecules to form phosphomolybdate precipitation and produces a corresponding redox current.The higher the concentration of DNA,the stronger the intensity of the current generated.Sodium molybdate solution and centrifuged cell supernatant were added onto the glassy carbon electrode to determine the cell concentration by measuring the current intensity.The cell viability,which means the ratio of living cells to the total cells,can also be determined by this method.This assay has the advantages of high sensitivity,low detection limit,and wide detection range.In addition,this method was successfully applied to the detection of cell concentration in human serum,which has potential clinical applications.

Preparation and Visible-light Photochromism of Phosphomolybdic Acid/Polyvinylpyrrolidone Hybrid Film

The visible-light photochromic hybrid film was constructed by entrapping phosphomolybdic acid（PMoA） into polyvinylpyrrolidone（PVPd） networks. The microstructure, photochromic properties and mechanism were inves- tigated with transmission electron microscopy（TEM）, atomic force microscopy（AFM）, Fourier transform infrared （FTIR） spectroscopy, ultraviolet-visible（UV-Vis） spectra and X-ray photoelectron spectroscopy（XPS）. The results in- dicate that the Keggin geometry of PMoA and the basic structure of PVPd are not destroyed during the composite process. Irradiated with visible light, the transparent PMoA/PVPd film changes color from colorless to blue and ex- hibits reversible photochromism in the presence of oxygen. According to the XPS analysis, the charge-transfer bridge of N-H-O has been built between PMoA and PVPd matrix via non-covalent bonding, and the appearance of Mo5＋ species indicates that the photo-reduction process is in accordance with the proton transfer mechanism.