Papers by Keyword: Phosphotungstic Acid

Abstract: In this work, the researchers developed a new composite membrane based on Polyvinyl Alcohol (PVA) doped carboxymethyl cellulose (CMC) matrix to obtain mixed matrix membranes (MMMs) that showed a high methanol resistance and also applied the citric acid (CA) as a crosslinking agent. The addition of Phosphotungstic Acid (PTA) as filler into the CMC/PVA matrix aims to improve the performance of the membranes. The composite membranes were evaluated for chemical stability, scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infra-red (FTIR), water uptake (WU), methanol uptake (MU), methanol permeability, and ion exchange capacity (IEC). The results showed the prominent value of oxidation stability according to its weight loss of 49.81 to 7.39% at 50 °C, the WU in the range of ± to 71.34%, the IEC of 0.17 to 0.72 mmol/g, the MU in the range 31.96 % to 4.38% and permeability of methanol in the range 17.28 × 10^-7 to 2.27 × 10^-7 cm²/s. The methanol permeability and uptake decreased along with the increase of the amount of PTA in the composite membrane. The addition of PTA increased the IEC and demonstrated significant positive effects in the composite membranes. In conclusion, the CMC/PVA/PTA membrane can be recommended as promising biomaterial for polymer electrolyte membrane direct methanol fuel cell (DMFC) applications.

Abstract: Porous montmorillonite (PMMT) was derived from natural montmorillonite (MMT) through functionalization using 3-aminopropyltrimethoxysilane (APTMS) and intercalation with cationic potato starch as the template. Phosphotungstic acid (HPW) supported on PMMT was synthesized by wet impregnation method. The resulting PMMT showed remarkable increase in surface area from the low value of 191 m²g^‒1 for parent MMT to the high value of 930 m²g^‒1 for PMMT. Acidity studies by pyridine adsorption followed by FTIR spectroscopy showed that both MMT and PMMT possessed strong Lewis acid sites. In contrast, the surface acidity of HPW incorporated into PMMT was shown to be significantly enhanced by forming mainly Brönsted acid sites. The catalytic activity of these materials was evaluated in the Friedel-Crafts acylation of anisole with propionic anhydride. The PMMT/30HPW catalyst which possesses the highest number of Brönsted acid sites showed excellent catalytic activity giving selectivity as high as 95% toward the main product, p-methoxypropiophenone.

Abstract: To investigate the photocatalytic degradation of MG by PW₁₂-TiO₂/SiO₂, in this study PW₁₂-TiO₂/SiO₂ composite oxides were prepared by sol-gel and hydrothermal strategy. The prepared photocatalysits were characterized by XRD, BET,TEM and EDS techniques and the configuration charateristics of PW₁₂-TiO₂/SiO₂ nanoparticles were systematically investigated. Photocatalytic activity was checked by the photocatalytic oxidation of MG dye in aqueous solution. The results showed that the phosphotungstic acid still has the Keggin structure. The anatase phase of titanium oxid is identified by XRD. The result of the present work implied that compared with pure TiO₂, the PW₁₂-TiO₂/SiO₂ composite oxides have stronger catalytic activity, good particles dispersion and bigger specific surface area. The optimal concentration of MG was 20mg.L^-1, the best dosage of PW₁₂-TiO₂/SiO₂ was 1g.L^-1. Moreover, after three times of recycling, the catalyst still has high catalytic activity.

Abstract: In this paper, CdS sample and phosphotungstic acid/CdS composite materials were prepared by hydrothermal synthesis and impregnation method, respectively. These samples were characterized by FT-IR, XRD and TEM. The characteristic peaks of phosphotungstic acid and CdS appeared in IR spectra of phosphotungstic acid /CdS composite samples. Using the degradation of Rhodamine B and Methylene blue solutions as the model reaction, respectively, the photocatalytic degradation performance of CdS, phosphotungstic acid and their composite samples was discussed under the irradiation of UV light or sunlight. The results showed the degradation effect of phosphotungstic acid /CdS to Rhodamine B and Methylene blue solution was better than CdS under the irradiation of 250 W mercury lamp or sunlight. Composite sample 1 had the best photocatalytic activity and its degradation rate on Rhodamine B was 85.2 % at 120 mins with pH 3.5 under sunlight, and the degradation rate of Methylene blue reached about 92.1% at 120 mins with pH 6.0 under sunlight.

Abstract: inorganicorganic hybrid nanoparticles between phosphotungstic acid (PTA) and rhodamine 6G (R6G) were synthesized by mixing a solution of 0.1 mmol R6G in ethanol (40 mL) and 40 mL of aqueous solution of PTA (0.2 g). The as-prepared PTA-R6G nanoparticles were characterized by scanning electron microscopy (SEM), UV-vis spectra, and Fourier transform-infrared (FT-IR) spectra. The SEM studies show that the PTA-R6G nanoparticles have an average diameter of about 111 nm and the atomic ratio of W to P is 12.7:1, near to the chemical stoichiometry of PTA. UV-vis spectra confirm that the R6G aggregates formed in PTA-R6G nanoparticles are J-type. The Keggin structure of PTA is maintained in the PTA-R6G hybrid nanoparticles, as demonstrated by FT-IR.

Abstract: Phosphotungstic acid supported over silica catalysts were prepared, characterized and tested. The results show that silica-supported phosphotungstic acid with 50 wt% of loading amount indicates excellent catalytic performance for the polymerization of α-pinene. It is also found that the products are easily separated from reaction mixture and the silica-supported phosphotungstic acid catalysts are low-corrosive. Hence, a clean and environmentally friendly heterogeneous catalyst for α-pinene polymerization is reported.

Abstract: Zeolitic imidazolate frameworks-8(ZIF-8, Zn (MIM) ₂, MIM=2-methylimidazole) was synthesized by solvothermal (S) method and liquid-phase diffusion (D) method. ZIF-8 was then directly impregnated with phosphortungstic acid (PTA) at room temperature. After impregnation, the ZIF-8 retained its integrity of frameworks as proved by several characterizations. The textural properties are heavily dependent on preparation methods. Diffusion method produced well-crystallized particles with larger surface area, whereas solvothermal method yielded poorly-crystallized particles. ZIF-8 and ZIF-8-PTA were applied in the photo-degradation of methylene blue (MB) with the assistance of electron acceptor hydrogen peroxide, in which both of them were found to be highly active photo-catalytic. Moreover, the impregnation of PTA improved clearly the activity of catalysts due to the fast reversible multi-electron redox transformations.

Abstract: This paper aims to study the catalytic effects of phosphotungstic acid on the degradation behaviour of E-51/DDM and E-51/MeTHPA epoxy resins. The results show that phosphotungstic acid promotes the decomposition of E-51/DDM and E-51/MeTHPA in different degree. The decomposition rate of E-51/MeTHPA is relatively higher. According to the GC-MS results, the composition of products when phosphotungstic acid is used as the catalyst is complicated, indicating that the decomposition mechanism is complicated.

Abstract: Oxidative desulfurization of model oil was conducted in emulsion oxidative system (water –in-oil [W/O]) using hydrogen peroxide as the oxidizing agent, N-methyl-2-pyrrolidone (NMP) and water as extractive solvent, span60 as surfactant. The system was evaluated for oxidative desulfurization of BT, DBT and 4.6-DMDBT using hydrogen peroxide as oxidant and exhibit excellent activities in oxidative desulfurization of model compounds.

Abstract: The initial activity, selectivity, and especially catalytic stability of mesoporous MCM-41 supported phosphotungstic acid (HPW) prepared by ultrasonic-assisted impregnation (UAI) method and the HY zeolite were contrastively investigated for alkenylation of p-xylene with phenylacetylene in a fixed-bed continuous flow reactor. N2 adsorption-desorption, FT-IR, X-ray diffraction (XRD) and NH3 temperature-programmed (NH3-TPD) desorption characterization techniques were employed to explore the relationship of catalyst nature and catalytic performance in alkenylation. Results illustrate that the as-prepared HPW/MCM-41 catalyst exhibits notably superior catalytic activity, selectivity and stability to microporous HY zeolite, ascribed to its well-ordered mesoporous architecture, appropriate acidic sites and high dispersity of HPW phase.