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Multi‐metallic catalysts rely on the synergistic effect between metals to perform better catalytic effect in biomass hydrogenation experiments compared with mono‐metallic catalysts. A series of CuNiAl composite metal oxide catalysts promoted by silicotungstic acid (HSiW), which were prepared by co‐precipitation and impregnation methods, were characterized by powder X‐ray diffraction (XRD), N2‐physisorption, scanning electron microscope (SEM) and NH3 program temperature desorption (NH3‐TPD) and pyridine infrared adsorption (Py‐FTIR). Their catalytic performance was evaluated in the hydrogenation of levulinic acid (LA) to prepare γ‐valerolactone (GVL). The results showed that the addition of Cu could improve the hydrogenation activity of Ni, and the addition of HSiW could further increase the amount of acid sites in the catalysts. Both of them could enhance the conversion of LA to some extent. CuNiAl‐5SiW, the par excellence catalyst, relied on the synergistic interactions between metals as well as the Brønsted and Lewis acid active sites to show efficient hydrogenation performance. The CuNiAl‐5SiW catalyst demonstrated 96.9 % conversion of LA and more than 99 % selectivity to GVL under 2 hours of reaction time, 180 °C of reaction temperature, 3.0 MPa of initial hydrogen pressure and solvent‐free conditions. [ABSTRACT FROM AUTHOR]

Nonthermal plasma (NTP), for the first time, was integrated in glycerol dehydration reaction catalyzed by silicotungstic acid supported on mesoporous silica with argon as the carrier and discharge gas. A range of reaction temperatures (220–320°C) and NTP discharge field strengths (2.06–6.87 kV/cm) were studied for the individual and interactive effects regarding the glycerol conversion and product selectivity. Results showed that the presence of NTP always improved the glycerol conversion, and NTP increased acrolein selectivity if properly conditioned. An optimal condition of 275°C and 4.58 kV/cm NTP field strength achieved a glycerol conversion of 94.4 mol%, acrolein selectivity of 88.0 mol%, with an acrolein yield of 83.1 mol%, representing a 10% improvement in acrolein production over that conducted at the same temperature but without NTP. Results of this study will also have significant implication for other heterogeneously catalyzed dehydration reactions. Simulation of the high‐voltage electric field distribution as function of NTP electrical conductivity and relative permittivity of catalyst materials also offers insight for the future design of reactors and catalysts. [ABSTRACT FROM AUTHOR]

Poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) is one of the most important engineering plastics commonly utilized in various fields. Herein, chemical recycling of PPO was performed via oxidative depolymerization to form 2,6‐diemthyl‐p‐benzoquionone (26DMBQ) as a sole aromatic product in 66 % yield using nitronium ions (NO2+) as a mild oxidant. Mechanistic studies revealed that PPO is oxidized by NO2+ generated from the combination of a silicotungstic acid and nitrate salts, and then subsequently attacked by H2O to achieve C−O bond cleavage, resulting in the formation of 26DMBQ, which was sublimed at the headspace of the reaction vessel in pure form. 26DMBQ was applied to polymerization with dianilines to form polyimides. Thus, an upgrade recycling process of PPO was demonstrated. [ABSTRACT FROM AUTHOR]

In this article, silicotungstic acid (STA)-loaded metal–organic framework (MOF)-derived composites (C-STA@ZrO2) were successfully synthesized by simple strategies. X-ray diffraction, Fourier transform infrared, scanning electron microscopy, energy-dispersive X-ray, N2 physisorption, UV-vis diffuse reflection spectroscopy, and X-ray photoelectron spectroscopy techniques were used to characterize the as-obtained composites. Intriguingly, C-STA@ZrO2 exhibits excellent photocatalytic performance, and rhodamine B (RhB) (40 mg·L−1) in water can be degraded to 93.9% after 120 min of irradiation. Moreover, various catalysts, catalyst dosage, and dye concentrations on RhB degradation were evaluated. Besides, the reusability of C-STA@ZrO2 was also investigated. This work may provide a new and significant guideline for exploring excellent performance of MOF-derived hybrid material for wastewater purification.

To facilitate value-added chemical production from renewable glycerol, gas-phase glycerol dehydration to acrolein was conducted using supported silicotungstic acid as solid acid catalysts, focusing on the effects of mesoporous catalyst supports on the catalytic performance. One alumina (Al) support with average mesopore size of 30 nm and two silica supports (Si1254 and Si1252) with mesopore size of 6 nm and 11 nm, respectively, were comparatively evaluated in this study. It was found that the Si1254 silica support with the smallest pore size (6 nm) deactivated the fastest, decreasing both the glycerol conversion and acrolein selectivity along the time-on-stream. The other silica support Si1252 with 11 nm pore size provided an acrolein yield comparable to the Al support over the tested 7.5 h time-on-stream (73.9 mol% for Si1252 vs. 74.1 mol% for Al). However, the mechanisms for achieving the comparable yield are different. Si1252 showed higher acrolein selectivity than Al, but it also deactivated faster than Al due to its quicker coking. On the other hand, Al showed more stable performance in terms of glycerol conversion rate and less coking, but it had lower acrolein selectivity and a higher selectivity to byproducts, especially the undesired byproducts of acetaldehyde and propionaldehyde, which posed difficulties in downstream separation.

The electroactive composites based on reduced graphene oxide (RGO), poly‐o‐phenylenediamine (PPD) and heteropolyacids – H4SiW12O40nH2O (SiW) and H3[PW12O40] ⋅ nH2O (PW) was applied to a screen‐printed carbon electrode (SPCE) as a planar three‐electrode cell as the first step to creating various devices, in particular, sensors and catalysts. We studied potential use of the modified and unmodified SPCE planar electrode in determining the concentration of antitubercular antibiotic isoniazid (isonicotinic acid hydrazide C6H7N3O or INH). The best result was observed for SPCE+RGO‐PPD‐SiW. CV of normal saline with various concentrations of C6H7N3O demonstrated linear dependence of the relevant anodic peak current either in the bulk solution upon immersion of the modified electrode or in a droplet on the electrode surface. [ABSTRACT FROM AUTHOR]

A new redox-active composite material based on reduced graphene oxide (RGO), poly-o-phenylenediamine (PPD), and silicotungstic acid (SiW) is studied. The SEM data showed an abrupt decrease in the content of oxygen atoms in the composite as compared to pure graphene oxide (GO). This is associated with its reduction to RGO in the course of RGO–PPD–SiW synthesis. A combination of RGO conductivity and redox catalysis due to the electroactive components (PPD and SiW) enables one to develop various sensors by applying RGO–PPD–SiW onto planar electrodes (screen-printed carbon electrodes, SPCE). In this work, the possibility of developing a sensor for the content of antituberculous antibiotic isoniazid (isonicotinic acid hydrazide C6H7N3O, INAH) is studied. Using the CVA method, it is shown that the concentration dependence of isoniazid oxidation current is linear. The electrocatalytic behavior of the composite during the isoniazid oxidation is also supported by the impedance spectroscopy. [ABSTRACT FROM AUTHOR]

To facilitate value-added chemical production from renewable glycerol, gas-phase glycerol dehydration to acrolein was conducted using supported silicotungstic acid as solid acid catalysts, focusing on the effects of mesoporous catalyst supports on the catalytic performance. One alumina (Al) support with average mesopore size of 30 nm and two silica supports (Si1254 and Si1252) with mesopore size of 6 nm and 11 nm, respectively, were comparatively evaluated in this study. It was found that the Si1254 silica support with the smallest pore size (6 nm) deactivated the fastest, decreasing both the glycerol conversion and acrolein selectivity along the time-on-stream. The other silica support Si1252 with 11 nm pore size provided an acrolein yield comparable to the Al support over the tested 7.5 h time-on-stream (73.9 mol% for Si1252 vs. 74.1 mol% for Al). However, the mechanisms for achieving the comparable yield are different. Si1252 showed higher acrolein selectivity than Al, but it also deactivated faster than Al due to its quicker coking. On the other hand, Al showed more stable performance in terms of glycerol conversion rate and less coking, but it had lower acrolein selectivity and a higher selectivity to byproducts, especially the undesired byproducts of acetaldehyde and propionaldehyde, which posed difficulties in downstream separation. [ABSTRACT FROM AUTHOR]

In this article, Bi-based metal–organic framework-supported silicotungstic acid (STA) was synthesized by a simple hydrothermal method and used as a precursor for the preparation of the Bi-based MOF-derived catalyst (STA@C-Bi-BDC). Using a combination of FTIR, XRD, SEM-EDS, N2 adsorption–desorption, TG, UV-Vis DRS, and XPS techniques, the successful immobilization of STA groups on Bi-MOF-derived C-Bi-BDC was assessed. Furthermore, the photocatalytic performance of the as-prepared catalysts was investigated in the degradation of the RhB dye process under visible light. Within 120 min of visible light exposure, the high degradation rate of RhB (92.7%) by STA@C-Bi-BDC system was achieved, which was a lot larger than the STA (39.4%), C-Bi-BDC (59.2%), and STA@Bi-BDC (74.0%) system, and cyclic experiments exhibit that the STA@C-Bi-BDC is a relatively stable photocatalyst. More importantly, the catalyst shows high applicability for the degradation of other dyes. This study reveals a comprehensive strategy for the design of efficient Bi-based MOF-derived photocatalyst for organic dye-based wastewater treatment.

In this study, the bimetallic Ni-Zr MOF-derived nickel-zirconium oxide (Ni-Zr-O)-impregnated silicotungstic acid (HSiW) nanocomposite catalyst (HSiW@Ni-Zr-O) was prepared via a hydrothermal procedure followed by a pyrolysis treatment, and its structural, morphological, and surface components and oxidation states were characterized by using XRD, FTIR, TPD-NH3, SEM, TEM, N2 physisorption, and XPS analyses. Then, the nanocomposite catalysts were successfully applied to the esterification of oleic acid (OA) with methanol. According to its characteristics, the obtained HSiW@Ni-Zr-O-1 catalyst would generate larger pores, a higher acidity, and active interfaces at the calcining temperature of 300 °C. Therefore, HSiW@Ni-Zr-O-1 exhibits an excellent catalytic activity of 95.2% under optimal reaction conditions. Additionally, the catalyst can be reused with a good catalytic activity after nine cycles. This study highlights the opportunity of using bimetallic MOFs as precursors to the synthesis of highly nanoporous metal oxide, which supports the larger-industrial scale production of biofuels. [ABSTRACT FROM AUTHOR]

In the present study, a facile solvothermal method was used for the synthesis of silicotungstic acid (HSiW) immobilized on Ce-based metal organic framework (Ce-BDC) and embedded in Zr-based metal-organic framework (UiO-66(Zr)) composite catalyst, namely, Ce-BDC@HSiW@UiO-66 for the production of biodiesel through green fatty acid esterification. The obtained hybrids were characterized by various characterization technologies, including Fourier transform infrared, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 physisorption, X-ray photoelectron spectroscopy, and temperature-programmed desorption of NH3 (NH3-TPD) analysis. The characterization analyses showed that the hybrids have been successfully synthesized. Also, the volume and pore size of UiO-66(Zr) were changed by introducing HSiW@Ce-BDC, and the resulting Ce-BDC@HSiW@UiO-66 possessed the mesoporous structure and relatively high surface area. Simultaneously, the NH3-TPD analysis of Ce-BDC@HSiW@UiO-66 reveals that the acid strength was increased in comparison with HSiW@Ce-BDC. In addition, the composite Ce-BDC@HSiW@UiO-66 demonstrated high catalytic activity, and the oleic acid esterification gave 81.5% conversion at optimum conditions of 0.2 g catalysts, 1:30 oleic acid to methanol molar ratio at 130°C for 4 h. More interestingly, after six recycling cycles, the reduction in the conversion rate was only 4.6%, indicating that Ce-BDC@HSiW@UiO-66 has excellent reusability. Our study provides an effective approach to synthesize multifunctional hybrids for green biofuel production.

Core-shell-type catalysts, which are synthesized by encapsulating the Cu-ZnO-Alumina type methanol synthesis catalyst (CZA) by silicotungstic acid (STA)-incorporated mesoporous alumina, were prepared following a hydrothermal route and tested in DME synthesis from syngas and CO2. Activity tests, which were performed in the pressure range of 30–50 bar, and the temperature range of 200–300 °C, with different feed compositions (CO2/CO/H2: 50/-/50, 40/10/50, 25/25/50, 10/40/50) showed that the best-operating conditions for the highest DME yield were 275 °C and 50 bar. Results proved that the presence of CO2 in the syngas had a positive effect on the DME yield. The total conversion of CO + CO2 increased with an increase in CO2/CO ratio. An overall conversion of CO + CO2 and DME selectivity values were obtained as 65.6% and 73.2%, respectively, with a feed composition of H2/CO2/CO = 50/40/10. Synthesis of methanol using the CZA catalyst from the CO2-containing gas mixtures was also investigated, and the total conversion of CO + CO2 and methanol selectivity values of 32.0% and 83.6%, respectively, were obtained with the H2/CO2/CO = 50/40/10 gas mixture. Results proved that the new STA incorporated core-shell-type bifunctional catalysts were highly promising for the conversion of CO2-containing syngas to DME. [ABSTRACT FROM AUTHOR]

• A catalytic system proposed for N 2 hydrogenation into NH 3 at ambient pressure and low temperature. • SiW 12 used to transfer and stored H 2 from gas phase intensively into bulk liquid over Pt/TiO 2. • SiW 12 released the proton and electron to hydrogenate N 2 into NH 3 on Ru/C. • SiW 12 -induced hydrogenation pathway reduced the energy barrier to a very low value. • Hydrogen poisoning on Ru/C can be eliminated. Catalytic hydrogenation of nitrogen is an important step for synthesis of ammonia. However, hydrogenation of nitrogen usually requires a high hydrogen pressure and high temperature due to the good stability of the N N bonds. Herein, a multiphase hydrogenation of nitrogen at temperatures lower than 100 °C and hydrogen pressures lower than 1 atm was reported using a synergetic catalytic system which consists of silicotungstic acid H 4 SiW 12 O 40 (SiW 12) aqueous solution suspended with Pt/TiO 2 and Ru/C catalysts particles. It is suggested that the low redox potential SiW 12 plays four vital roles in hydrogenation of nitrogen to ammonia. First, it quickly oxidizes and stores the H 2 gas to form reduced SiW 12 in the presence of Pt/TiO 2. Second, it transfers both electrons and H+ ions from the gas–liquid interface to the bulk solution. Third, it releases the electrons and H+ ions to form active H* or H 2 which converts nitrogen N 2 to ammonia NH 3 on the Ru/C surface. Fourth, the active H* released by SiW 12 to be added on nitrogen from bulk phase reduces the hydrogenation energy barriers, which results in elimination of the hydrogen poisoning. The SiW 12 -induced hydrogenation mechanisms are supported by reaction kinetic analysis and density functional theory computations. By these properties of SiW 12 , the hydrogenation of nitrogen to ammonia can be completed at relative low temperature and low hydrogen pressure. [ABSTRACT FROM AUTHOR]

Here, we introduced polyoxometalate (POMs) into polypyrrole (PPy) gas sensitive material for the first time to restrain the electron-hole recombination process and enhance the gas sensing performances. At room temperature, the sensing response value of PPy/POMs composite nanoparticles to 100 ppm NH 3 gas can be improved to 80.85 %, 2.99 times than that of pure PPy nanoparticles. PPy/3 % SiW 12 sensor response-recovery time was 39 s/166 s. It had good linearity (R2 = 0.9958), the LOD of NH 3 was 85 ppb. In 21 days, the sensor still maintained over 90 % of the initial ammonia response value. Selectivity, repeatability and other sensing parameters were systematically investigated. In addition, the mechanism of sensing performance enhancement was analyzed and discussed. The study proved that POMs can separate electrons and holes, finally improved gas sensing properties. This work provides a new idea for the design and construction of high sensitivity PPy-based gas sensor by introducting polyoxometalates. [Display omitted] • First demonstration of the influence of POMs on gas sensing performance of PPy. • The decoration of POMs enhanced the NH 3 gas-sensing performance of PPy. • The PPy/x%SiW 12 sensor exhibit a gas sensing response of 80.85 %–100 ppm NH 3 gas. • The sensing response of composite is 2.99 times higher than pure PPy sensor. • The sensor shows excellent selectivity and long-term stability. [ABSTRACT FROM AUTHOR]

Furfural and levulinic acid are valuable platform compounds that can be produced by acid catalyzed conversion of sugars. Modified MCM-41 with different contents of silicotungstic acid (20 wt%-50 wt%) was successfully prepared via a wet impregnation method in order to regulate the ratio of Brønsted acid to Lewis acid. Among these catalysts, 40 wt% HSiW/MCM-41 with superior acid site density (Brønsted acid 59.35 μmol/g, Lewis acid 33.69 μmol/g) showed excellent catalytic activity as it exposed the most acidic sites and the ratio of Brønsted acid to Lewis acid reached 1.76. The conversion of biomass-based sugar was as high as 99.01 %, the maximum yield of furfural could reach 56.75 %, and the yield of levulinic acid could reach 18.88 % catalyzed by 40 wt% HSiW/MCM-41. This study provided new insights into the development of efficient and sustainable catalytic systems for the production of biomass-derived compounds. [Display omitted] • The acidic sites in MCM-41 were regulated by loading silicotungstic acid. • The maximum yield of furfural and LA was reach 56.75 % and 18.88 % over 40 wt% HSiW/MCM-41. • The high catalytic activity of 40 wt% HSiW/MCM-41 was due to the highest ratio of Brønsted and Lewis acidic site. [ABSTRACT FROM AUTHOR]

[Display omitted] • A mild biphasic pretreatment was desirable for high efficiency fractionation. • High removal of hemicellulose and lignin were achieved. • 85.60% of cellulose was retained with 94.27% of saccharification. • 106.17 mg/g of xylonic acid was obtained by oxidation of xylose in aqueous phase. • Lignin-based film in organic phase was fabricated with good mechanical properties. Developing an efficient and facile pretreatment is of great importance to comprehensive utilization of lignocellulosic biomass. Herein, a biphasic system of 2-phenoxylethanol (EPH) and silicotungstic acid (STA) was employed for fractionation of corn stover. The EPH/STA biphasic system demonstrated remarkable fractionation efficiency to remove 90.23 % of xylan and 88.54 % of lignin, while retaining 85.60 % of cellulose under the mild pretreatment conditions of 130 °C for 90 min with 7/3 of EPH/STA and 40 mM of STA. The xylose of 52.93 % and lignin of 88.01 % were recovered in aqueous phase and organic phase by EPH/STA biphasic pretreatment, respectively. In the further process, 94.27 % of saccharification was achieved by enzymatic hydrolysis of cellulose-rich solid residue, and 106.17 mg/g of xylonic acid was obtained by oxidation of xylose in aqueous phase. Additionally, the recovered lignin in organic phase could be fabricated to lignin-based films with good mechanical properties. Notably, acid solvent in biphasic system had an important role in fractionation efficiency of corn stover. The STA had the best effect among the different acid solvents. This work provided a promising route to full components utilization of corn stover for biomass valorization. [ABSTRACT FROM AUTHOR]

The electrochemical behavior of electroactive composites based on reduced graphene oxide (RGO), poly‐o‐phenylenediamine (PPD) and heteropolyacids (HPA) (silicotungstic [SiW] and phosphotungstic [PW]) was comparatively studied by means of cyclic voltammetry (CVA), charge–discharge galvanostatic curves, and electrochemical impedance. The composites were applied to planar screen‐printed carbon electrodes as the first step to creating various devices, in particular, sensors based on novel composites. Like RGO‐PPD‐SiW composites, RGO‐PPD‐PW composites also exhibit several redox transitions. With respect to the method of synthesis (order of applying components), RGO‐PPD‐PW can exhibit the properties of a mediator catalyst as was demonstrated for example of the redox transition in the quinone‐hydroquinone couple, where reversibility is significantly enhanced by conducting the reaction on a RGO‐PPD‐PW‐modified electrode. [ABSTRACT FROM AUTHOR]

In this study, the bimetallic Ni-Zr MOF-derived nickel-zirconium oxide (Ni-Zr-O)-impregnated silicotungstic acid (HSiW) nanocomposite catalyst (HSiW@Ni-Zr-O) was prepared via a hydrothermal procedure followed by a pyrolysis treatment, and its structural, morphological, and surface components and oxidation states were characterized by using XRD, FTIR, TPD-NH3, SEM, TEM, N2 physisorption, and XPS analyses. Then, the nanocomposite catalysts were successfully applied to the esterification of oleic acid (OA) with methanol. According to its characteristics, the obtained HSiW@Ni-Zr-O-1 catalyst would generate larger pores, a higher acidity, and active interfaces at the calcining temperature of 300 °C. Therefore, HSiW@Ni-Zr-O-1 exhibits an excellent catalytic activity of 95.2% under optimal reaction conditions. Additionally, the catalyst can be reused with a good catalytic activity after nine cycles. This study highlights the opportunity of using bimetallic MOFs as precursors to the synthesis of highly nanoporous metal oxide, which supports the larger-industrial scale production of biofuels.

The behavior of novel electroactive material based on reduced graphene oxide (RGO), poly-o-phenylenediamine (PPD), and silicotungstic acid (SiW) is studied using the methods of cyclic voltammetry (CVA) and electrochemical impedance. It is found that graphene oxide (GO) has a catalytic effect on the electrochemical codeposition of PPD and SiW onto the GO film during fabricating the RGO–PPD–SiW composite. It is shown that the composite has at least six redox transitions depending on the chosen range of cycling potentials. It is found that, at the potentials of 200 and 500 mV (Ag/AgCl), the conductivity of the composite is by 4 orders of magnitude higher than that of PPD. By the example of quinone-hydroquinone and ferro-ferricyanide redox reactions, it is shown that, in this potential range, the composite exhibits electrocatalytic properties, though neither PPD nor SiW individually exhibit pronounced redox transitions in this potential range. [ABSTRACT FROM AUTHOR]

Core-shell-type catalysts, which are synthesized by encapsulating the Cu-ZnO-Alumina type methanol synthesis catalyst (CZA) by silicotungstic acid (STA)-incorporated mesoporous alumina, were prepared following a hydrothermal route and tested in DME synthesis from syngas and CO2. Activity tests, which were performed in the pressure range of 30–50 bar, and the temperature range of 200–300 °C, with different feed compositions (CO2/CO/H2: 50/-/50, 40/10/50, 25/25/50, 10/40/50) showed that the best-operating conditions for the highest DME yield were 275 °C and 50 bar. Results proved that the presence of CO2 in the syngas had a positive effect on the DME yield. The total conversion of CO + CO2 increased with an increase in CO2/CO ratio. An overall conversion of CO + CO2 and DME selectivity values were obtained as 65.6% and 73.2%, respectively, with a feed composition of H2/CO2/CO = 50/40/10. Synthesis of methanol using the CZA catalyst from the CO2-containing gas mixtures was also investigated, and the total conversion of CO + CO2 and methanol selectivity values of 32.0% and 83.6%, respectively, were obtained with the H2/CO2/CO = 50/40/10 gas mixture. Results proved that the new STA incorporated core-shell-type bifunctional catalysts were highly promising for the conversion of CO2-containing syngas to DME.

The CeO2 modified by silicotungstic acid (impregnation method [SiW/CeO2] and one pot method [CeO2‐Si‐W]) was investigated in the NH3‐SCR reaction. The surface nitrate species and surface acid sites were improved by the introduction of silicotungstic acid into CeO2, which stopped forming stable nitrate, and then improved the N2 selectivity. The interaction between Ce and W species existed and caused the formation of Ce2(WO4)3 at CeO2‐Si‐W, resulting in the abundance of unsaturated W=O, which contributed to the generation of Brønsted acid sites and was responsible for the superior SCR performance. Thus, CeO2‐Si‐W exhibited the best NOx conversion and nearly 100% NOx conversion was obtained at 225–450°C. [ABSTRACT FROM AUTHOR]

The CeO2 modified by silicotungstic acid (impregnation method [SiW/CeO2] and one pot method [CeO2‐Si‐W]) was investigated in the NH3‐SCR reaction. The surface nitrate species and surface acid sites were improved by the introduction of silicotungstic acid into CeO2, which stopped forming stable nitrate, and then improved the N2 selectivity. The interaction between Ce and W species existed and caused the formation of Ce2(WO4)3 at CeO2‐Si‐W, resulting in the abundance of unsaturated W=O, which contributed to the generation of Brønsted acid sites and was responsible for the superior SCR performance. Thus, CeO2‐Si‐W exhibited the best NOx conversion and nearly 100% NOx conversion was obtained at 225–450°C. [ABSTRACT FROM AUTHOR]

The present article reports the synthesis of butyl levulinate, a potential biofuel additive via the esterification of levulinic acid and n-butanol. A sustainable catalytic approach using heterogeneous catalysts based on 12-tungstosilicic acid (SiW 12) and supports, nMCM-48 and MCM-22 was developed via a detailed optimization study to achieve maximum selectivity of butyl levulinate (≥95%) at mild reaction conditions and reused the catalysts for multiple runs. Importantly, the effect of nature as well as the structure of the supports on activity was studied via kinetic experiments and comparative studies. Based on this, the best catalyst was proposed and wide range of alkyl levulinates, possessing fuel-blending properties were synthesized using best catalyst, showcasing its versatile nature. [Display omitted] • Green catalytic approach using sustainable mesoporous and zeolitic catalysts. • Butyl levulinate synthesis under mild conditions (90℃, 4 h) with 100% selectivity. • Study of effect of nature and the structure of the supports on catalytic activity. • Addressing the challenging task of the production of alternative fuel additives. • Evolution in energy transition for industrial synthesis of fuel blending esters. [ABSTRACT FROM AUTHOR]

The biomass-derived furan compound furfuryl alcohol can be utilized to produce fuel substitutes, furfuryl ethers, through etherification reactions with short-chain monohydric alcohols. In order to solve the problems of high reaction temperature and poor product selectivity in this research, a porous carbon-based material with adjustable acidic strength and content, and acid species ratio was synthesized and prepared in this work. Zirconium was employed as Lewis acid and adjusting its loading was the key method to drive the etherification reaction. The physicochemical properties of the material were confirmed based on BET, FTIR, XRD, NH 3 -TPD and other characterization methods. The active sites of the catalysts were identified by poisoning experiments, and the kinetics of the catalytic reactions were designed and discussed. The apparent activation energy of Zr5-ST-C was calculated according to the Arrhenius equation. This study provides an effective solution for the efficient synthesis and industrial application of furfuryl ethers. [Display omitted] • A zirconium based mesoporous carbon material with adjustable acid sites has been synthesized. • Kinetic characterization of catalytic furfuryl etherification reactions was carried out. • An efficient synthesis scheme for furfural ethers is provided. • Development of zirconium-based catalysts with potential application in furfuryl etherification reactions. [ABSTRACT FROM AUTHOR]

The methods of silicotungstic acid (SiW) immobilization on conducting substrates were studied. For SiW immobilization by codeposition, poly-o-phenylenediamine (PPD) redox polymer was used. The most effective codeposition of SiW and PPD was demonstrated on a graphene oxide (GO) film. Meanwhile, GO is reduced to form RGO-PPD-SiW electroactive composite. The structure of the novel material was evidenced by cyclic voltammetry and IR and Raman spectra. PPD-SiW and RGO-PPD-SiW composites were studied by impedance spectroscopy, where an equivalent circuit was proposed. Film resistance Rf was shown to decrease in the series of PPD → RGO-PPD → RGO-PPD-SiW. Further, RGO-PPD-SiW has better transfer properties (bulk film diffusion rate). This enabled suggesting that the composite has better electrocatalytic properties than PPD and RGO-PPD as was evidenced for example of [Fe(CN)6]4−/3− redox transfer on the electrode coated with the novel material. [ABSTRACT FROM AUTHOR]

A heterogeneous catalyst comprising Keggin type polyoxometalate, silicotungstic acid (SiW12), and MCM-22 was synthesized using wet impregnation method and characterized by acidity measurement, BET, FT-IR, XRD, and SEM. Their catalytic activity was evaluated for the degradation of cationic organic dyes like methylene blue (MB), crystal violet (CV), and an azo dye Chryosidine Y (CY) in an aqueous solution. The experimental parameters such as catalyst amount, initial dye concentration, and contact time were studied for the degradation of dyes, and it was found that the cationic dyes like methylene blue and crystal violet show better activity as compared to azo dye Chryosidine Y. This may be attributed to better electrostatic interaction of these cationic dyes with the residual negative surface charge of the catalyst, due to presence of SiW12 ion as it is rich in surface oxygens and surface hydroxyl groups. The control experimental results showed that the presence of SiW12 at the surface of MCM-22 promoted the degradation reactions, and presence of multiple W–O bonds in polyoxometalate also played a key role in this reaction. The catalyst exhibits recycling ability without any significant loss in activity up to four cycles. [ABSTRACT FROM AUTHOR]

Heteropoly acids have attracted great attention as potential solid-state proton-conducting materials owing to their high proton conductivity of 10–2 S cm−1 at room temperature. However, the proton conductivity can be significantly reduced under operating conditions due to the leaching of water molecules out of the acid Keggin structure. In the present study, silicotungstic acid (SiWA) was encapsulated in the mesoporous structure of the chromium (III) terephthalate metal–organic framework (MIL-101) in an attempt to prevent water loss and preserve proton conductivity. This hybrid material was then shaped into a membrane with the aid of polyvinyl alcohol (PVA). This approach of SiWA encapsulation with PVA addition to form a membrane proved to be successful as the proton conductivity of the resulting membranes was found to be of 2.4 × 10–2 S cm−1 at 25 °C and 25% RH. Under low levels of hydration, when the membrane was dried at 80 °C, the proton conductivity still remained high (1.9 × 10–2 S cm−1). This improved proton conductivity is believed to be the result of the continuous channels for facile proton transport created through the immobilisation of the heteropoly acid within the MIL-101 framework. [ABSTRACT FROM AUTHOR]

In the present study, a set of methanol synthesis catalysts with different Cu/Zn/Al or Cu/Zn/Zr molar ratios were synthesized by a co-precipitation method. Silicotungstic acid and tungstophosphoric acid were impregnated into these materials to synthesize new bifunctional catalytic materials to be used in direct synthesis of dimethyl ether (DME) from syngas. In the case of methanol production, synthesized Cu/Zn/Al catalysts exhibited quite high methanol selectivity, reaching to approximately 87%. These results indicated that the dispersion of copper particles profoundly affected the selectivity of methanol. Direct synthesis of DME was investigated in the presence of heteropoly acid impregnated copper-based novel hybrid type bifunctional catalysts. Results revealed that product distributions were strongly influenced by the reaction temperature, pressure, heteropoly acid content, and type. Results proved that silicotungstic acid (STA) impregnated bifunctional catalysts showed much better catalytic performance than the tungstophosphoric acid (TPA) impregnated ones in DME synthesis from syngas. Very high dimethyl ether selectivity values were achieved in direct synthesis of dimethyl ether over the 25%, and 30% STA impregnated methanol synthesis catalysts, at 275 °C and 50 bar. DME selectivity presented an increasing trend due to the increase in heteropoly acid content over methanol synthesis catalysts. The silicotungstic acid incorporated (30%) Cu/Zn/Al catalyst, having a composition of 6/3/1 (30STA@CZA:631), showed the highest CO conversion and DME selectivity. However, coke formation over this catalyst was much more than the catalyst containing 25% STA. This is mainly due to the higher Bronsted acidity of 30STA@CZA:631 than 25STA@CZA:631. Low coke formation, together with quite high DME selectivity values achieved with 25STA@CZA:631, is a worthy distinction of this catalyst for the direct synthesis of DME from synthesis gas. Novel hybrid type catalysts are successfully synthesized for direct synthesis of dimethyl ether process. Heteropoly acid incorporated methanol synthesis catalysts are very active and stable in the direct synthesis of dimethyl ether process. Silicotungstic acid (STA) impregnated copper-based catalyst exhibits a superior performance than the tungstophosphoric acid impregnated catalyst. [ABSTRACT FROM AUTHOR]

Composite organic–inorganic proton exchange membranes for H2–O2 fuel cells were fabricated by ionotropic gelation process combining a biopolymer (chitosan) with a heteropolyacid (silicotungstic acid). According to scanning electron microscopy analysis, compact, homogeneous and free-standing thin layers were synthesized. X-ray diffraction proved the crystallinity of the fabricated membranes and showed the presence of Chitosan Form I polymorph soon after the reticulation step and of the Form II polymorph after the functionalization step. Fourier-transform infrared spectroscopy demonstrated that the Keggin structure of the heteropolyacid is maintained inside the membrane even after the fabrication process. These membranes worked properly as proton conductors in a low-temperature (25 °C) fuel cell apparatus using hydrogen as fuel recording a promising power density peak of 268 mW cm−2 with a Pt loading of 0.5 mg cm−2. [ABSTRACT FROM AUTHOR]

A catalytic oxidation reaction for Acid Blue 7 dye synthesis was evaluated in water. Without lead oxide or manganese oxide derivatives as oxidants, polyoxometalate catalysts were investigated to reduce the usage of harmful heavy metal. A catalyst was prepared by mixing silicotungstic acid with copper oxide, and aqueous hydrogen peroxide (30%) was used as an oxidizing agent. This reaction proceeded to produce Acid Blue 7 from the corresponding leuco acid after 45 min at 95 °C and was viable for a 10 g-scale synthesis.

The solubility and solubility product of the two ion-associates clomipraminium tetraphenylborate (CLP-TPB) and silicotungstate ((CLP)4-ST) were determined using conductimetric and potentiometric measurements applying the standard addition method. The obtained values from both conductimetric measurements and standard addition method are close to each other. Thermodynamic parameters ΔG, ΔH and ΔS have been determined. Sodium tetraphenylborate has been used for the determination of CLP.Cl in model solution and pharmaceutical preparation by conductimetric titrations. The proposed method allowed the determination of CLP.Cl within the range of 0.17–35.15 mg. The accuracy of the method is indicated by the excellent recovery 99.95–101.23%, and the precision is supported by the low relative standard deviation 0.50–1.21%. The ruggedness and robustness of the proposed method were also studied.

Condensation of various isatins with heteroaromatics (indoles and pyrrole) has been carried out in the presence of catalytic amount of silicotungstic acid (STA) at room temperature to form their corresponding 3,3-bis(indolyl)- and 3,3-bis(2-pyrrolyl)oxindoles. The mechanistic aspects of the reaction have also been discussed.

• H 2 and O 2 were produced at separate times in water-organic solvent systems. • H 4 SiW 12 O 40 was an efficient electron-coupled-proton buffer in the present systems. • Organic solvents could regulate the redox property of silicotungstic acid in water. • A high yield of hydrogen (∼85%) was obtained in a water-ethanol system (V/V = 1:1). • Semihydrogenation of organic compounds could be achieved under mild conditions. H 2 and O 2 were produced at separate times from water electrolysis by using silicotungstic acid as an electron-coupled-proton buffer. It was found that the redox property of silicotungstic acid in water could be regulate by the introduction of organic solvents (acetonitrile, DMF and ethanol). The redox wave of silicotungstic acid at ∼0.02 V vs. RHE moved in the negative direction, which was good for the production of hydrogen. A high yield of hydrogen (∼85%) was obtained in a water-ethanol system (V/V = 1:1), which was higher than that in water (∼45%). And the introduction of ethanol didn't affect the rate of hydrogen evolution. Moreover, the semihydrogenation of organic compounds could be achieved in the present system under mild conditions. The conversion of phenylacetylene and acetophenone are 97% and 80% under optimum reaction conditions, while the selectivity of styrene and 1-phenylethanol are 80% and 82%, respectively. [ABSTRACT FROM AUTHOR]

Hybrid membranes were prepared by loading silicotungstic acid (STA) and phosphomolybdic acid (PMA), into polyvinyl alcohol (PVA) matrix. The membranes were characterized by Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), contact angle meter, thermogravimetric analysis (TGA), and X-ray diffraction (XRD). Separation performance of hybrid PVA membranes was compared over that of neat PVA membrane, for dehydration of aqueous isopropanol mixtures by using the pervaporation (PV) process. The PV experiments were conducted over the feed water composition of 5–20 wt.%, temperature range of 3060 °C, and heteropolyacid amount of 5–20 wt%. Usage of hybrid membranes for separating water from the organic solvents, results in high flux and selectivity values. Of all the membranes studied, 5 wt% STA loaded hybrid PVA membrane and 5 wt% PMA loaded hybrid PVA membrane, exhibited best separation performance. While flux and selectivity values are 0.499 kg/m2h and 12848 for 5 wt% STA loaded hybrid PVA membrane, these values are 0.471 kg/m2h and 74991 for 5 wt% PMA loaded hybrid PVA membrane. Flux and selectivity values of neat PVA membrane are quite lower, as compared to the hybrid membranes. Neat PVA membrane has 0.360 kg/m2h of flux, and 36 of selectivity values. From this study, it is concluded that the selectivity and flux values of hybrid membranes, are rather higher than the neat PVA membrane. [ABSTRACT FROM AUTHOR]

High proton conductive x CsHSO 4 -(1- x)H 4 SiW 12 O 40 (CHS-WSiA) composites were successfully prepared via a new liquid-phase shaking method. N,N ‑Dimethylacetamide (DMAc) and zirconium balls were used as a solvent/dispersing medium and a collision medium, respectively. X-ray diffraction characterization confirmed that the liquid-phase shaking treatment induced an ion-exchange reaction between Cs+ ions in CHS and H+ ions in WSiA to form new composite materials. The proton conductivities of these composites were significantly improved over their precursor materials, especially at low temperatures, below the superprotic phase-transition temperature of CHS. The 0.9CHS-0.1WSiA (in mole ratio) composite, for instance, showed the highest proton conductivities of 1.38 × 10−4 to 2.42 × 10−3 S cm−1 from 50 °C to 170 °C under dry conditions of nitrogen atmosphere. The enhanced anhydrous proton conductivities of the Cs-substituted WSiA composites were also corroborated with shortening of the hydrogen bonding distance in these composites for fast proton hopping transport mechanism via 1H NMR evaluation. • Superprotic xCsHSO 4 ·(1-x)H 4 SiW 12 O 40 composites prepared via liquid-phase shaking. • High Cs substitution into WSiA induced shorter H-bonds and lower E A. • Anhydrous proton conductivities due to new hydrogen bonds formation. [ABSTRACT FROM AUTHOR]

A single-stage synthesis of isoprene from methyl tert-butyl ether (MTBE) and formalin in an organic-aqueous two-phase system was studied by using solid acid catalysts, i.e., USY zeolite, silicotungstic acid (STA) 25 wt% encapsulated in MIL-101(Cr) (STA25@MIL-101), and STA 25 wt% encapsulated in SBA-15 (STA25@SBA-15). From preliminary experiments, the catalytic activity decreased in the order: STA25@MIL-101 > SBA25@SBA-15 > USY zeolite. This suggested that isoprene formation was favored with high surface area and high acid strength of catalyst. Then, the porous hybrid material of a MIL-101 metal organic framework and STA was studied in more detail. MIL-101 was not efficient for isoprene synthesis at mild reaction condition. On increasing STA loading, which was well correlated with the Brӧnsted acid property, the catalyst activity increased in the order: MIL-101 < STA30@MIL-101 < STA60@MIL-101. The high acidity catalyst gave high isoprene yield at optimum low temperature and low side reaction products. For the STA30@MIL-101 and STA60@MIL-101 catalysts, the isoprene yield could be sustained at 18.5% (0.4% SD) and 30.0% (1.5% SD), respectively over three recycling runs. It is apparent that no STA leaching from the low STA loading catalyst occurred. [ABSTRACT FROM AUTHOR]

Spiramycin is a widely used macrolide antibiotic and exists at high concentration in production wastewater. A thermal-acid hydrolytic pretreatment using silicotungstic acid (STA) under microwave (MW) irradiation was suggested to mitigate spiramycin from production wastewater. Positive correlations were observed between STA dosage, MW power, interaction time and the hydrolytic removal efficiencies, and an integrative equation was generalized quantitively. Rapid and complete removal 100 mg/L of spiramycin was achieved after 8 min of reaction with 1.0 g/L of STA under 200 W of MW irradiation, comparing to 30.1% by MW irradiation or 15.9% by STA alone. The synergetic effects of STA and MW irradiation were originated from the dissociated-proton catalysis by STA and the dipolar rotation heating effect of MW. STA performed much better than the mineral acid H 2 SO 4 under MW, due to the much stronger Brönsted acidity and higher Hammett acidity. After 8 min, 98.0% of antibacterial potency was also reduced. The m/z 558.8614 fragment (P1) and m/z 448.1323 fragment (P2) were identified as the primary products, which were formed by breaking glucosidic bonds and losing mycarose and forosamine for P1 and further mycaminose moiety for P2. Finally, production wastewater with 433 mg/L of spiramycin was effectively treated using this thermal-acid hydrolytic method. Spiramycin and its antibacterial potency both dropped to 0 after 6 min. The potency drop was supposed from the losing of mycarose and/or forosamine. To decrease both the concentration of spiramycin and its antibacterial potency, combinedly using STA and MW was suggested in this work to break down the structural bonds of the functional groups rather than to destroy the whole antibiotic molecules. It is promising for pretreating spiramycin-contained production wastewater to mitigate both the antibiotic and its antibacterial potency. Image 1 • STA and MW were combinedly used for thermal-acid hydrolytic removal of spiramycin. • Synergetic effect observed was due to proton catalysis and dipolar rotation heating. • Under MW irradiation, STA performed much better than mineral acid H 2 SO 4. • Breaking glucosidic bonds in deoxyhexoses sugars led to antibacterial potency drop. • Spiramycin-contained production wastewater was successfully treated by STA and MW. Combined using silicotungstic acid and microwave were effective in breaking glucosidic bonds of spiramycin, which led to the concentration decay and antibacterial potency mitigation. [ABSTRACT FROM AUTHOR]

Abstract In this work, the influence of silicotungstic acid concentration on the diphenylamine (DPA) electropolymerization in the absence and the presence of reduced graphene oxide (RGO) is studied. The optical properties of the composites based on polydiphenylamine (PDPA) doped with the H 4 SiW 12 O 40 heteropolyanions and RGO are investigated by Raman scattering, IR absorption spectroscopy and photoluminescence (PL). The presence of RGO induces an up-shift of the oxidation maximum of the DPA, as a result of a covalent functionalization process of graphene sheets with the polymer in the doped state. The deposition of PDPA onto RGO sheets surface is confirmed by the Raman scattering studies. Regardless of the H 4 SiW 12 O 40 concentration, an up-shift of the IR bands from 910 to 1014 cm−1 to ∼920 and 1022 cm−1 is reported as a consequence of the compensation of positive charges of PDPA macromolecular chains with of the H 4 SiW 12 O 40 heteropolyanions. An enhancement in the absorbance of the IR bands situated in the spectral range 750–1050 cm−1 accompanied of a decrease in the relative intensity of the PL bands of PDPA and their composites with RGO, as increasing the H 4 SiW 12 O 40 concentration, is reported. In the presence of RGO, a change in the PDPA PL spectra profile is also highlighted. Graphical abstract Image 1018328 Highlights • Electropolymerization of DPA in the presence of RGO and H 4 SiW 12 O 40 is studied. • Functionalization of RGO with PDPA is evidenced by the Raman and IR studies. • FTIR spectra proves insertion of the H 4 SiW 12 O 40 heteropolyanions in PDPA matrix. • A PDPA PL quenching process in the presence of RGO is highlighted. [ABSTRACT FROM AUTHOR]

The effect of different pH values (8, 9, 10 and 11) on the catalytic activity over CeSiW catalysts was investigated for the selective catalytic reduction of NO by NH3. CeSiW-9 showed a remarkable higher NOx conversion. The strongest interaction was observed between silicotungstic acid and CeO2 over CeSiW-9, resulting in the improvement of redox ability and surface acidity, which could increase the catalytic activity. The superior catalytic performance of the CeSiW-9 catalyst was attributed to the favored pore structures, excellent redox ability and the abundance of surface acid sites, which depended on pH values in the preparation process of CeSiW catalysts. [ABSTRACT FROM AUTHOR]

The effect of different pH values (8, 9, 10 and 11) on the catalytic activity over CeSiW catalysts was investigated for the selective catalytic reduction of NO by NH3. CeSiW-9 showed a remarkable higher NOx conversion. The strongest interaction was observed between silicotungstic acid and CeO2 over CeSiW-9, resulting in the improvement of redox ability and surface acidity, which could increase the catalytic activity. The superior catalytic performance of the CeSiW-9 catalyst was attributed to the favored pore structures, excellent redox ability and the abundance of surface acid sites, which depended on pH values in the preparation process of CeSiW catalysts. [ABSTRACT FROM AUTHOR]

In this paper, silicotungstic acid (HSiW) was impregnated on natural minerals such as clinoptilolite (HSiW/Clin), mordenite (HSiW/Mord), bentonite (HsiW/Bent) and kaolinite (HSiW/Kaoln) and were evaluated towards photocatalytic degradation of methylene blue in wastewater. The as-prepared photocatalysts were characterized by X-ray powder diffraction (XRD), Field Emission Scanning Microscopy (FESEM), Fourier transform infrared (FTIR) and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS). The results showed that the crystallinty of HSiW was different on above mentioned minerals and HSiW on clinoptilolite had the most crystallinty and the smallest crystallite size. FESEM showed that the supported HSiW had nanometric spherical particles with narrow and uniform distribution. FTIR revealed Keggin structure of HSiW in all photocatalysts and a strong interaction between HSiW and minerals. DRS studies showed HSiW/Clin and HSiW/Mord had photoactivity in both visible and ultraviolet regions while HSiW/Bent and HSiW/Kaoln photocatalysts were just active in UV region. More studies indicated that HSiW/Clin had the lowest band gap of 3.1 eV among studied nano photocatalysts. This sample could degrade 92% of methylene blue after 90 min of UV irradiations and HSiW/Mord, HSiW/Bent and HSiW/Kaoln were in the next positions. Kinetic studies illustrated photocatalytic degradation of methylene blue followed a pseudo first order reaction and the highest rate constant belonged to HSiW/Clin and other photocatalysts had much lower rate constants. Effect of operation parameters like wastewater pH, initial dye concentration, photocatalyst loading and successive runs of HSiW/Clin was investigated and at the end a new mechanism for this photocatalyst was proposed. [ABSTRACT FROM AUTHOR]

Abstract We report on a novel DNA affinity biosensor which utilises the capture of a neutral charged single stranded (ss) morpholino DNA on a gold electrode to trigger an electrostatic repulsion of negatively charged silicotungstate anions and, in turn, enabled detection of the hybridisation of complementary base pairs. The repulsion of the anions, as a redox indicator, is reflected by a decrease in its electrochemical response with increasing target ss-DNA concentration. A theoretical framework for DNA detection by the affinity biosensor is proposed and verified by electrochemical measurements in the presence of the target ss-DNA by either dc cyclic voltammetry or Fourier transformed alternating current voltammetry (FTACV). The optimised conditions for the capture of the target ss-DNA and the electrochemical detection include 1 μM thiolated neutral morpholino oligo-nucleotide probe, hybridisation time of 10 min, 0.25 mM [α-SiW 12 O 40 ]4-, and 25 mM phosphate buffer. In addition, the use of the 5th harmonic component of the FTACV gave the most sensitive response for the detection of the target ss-DNA. Under these conditions, the DNA affinity biosensor, based on FTACV detection, achieved a minimum detectable concentration of 0.1 pM ss-DNA and a linear concentration range of 0.1–1000 pM. The biosensor also successfully distinguished between some matched and mismatched base pairs. Graphical abstract fx1 Highlights • Hybridisation of complementary base pairs via the capture of a single stranded morpholino DNA. • Detection of hybridisation by the triggered repulsion of silicotungstate anions from electrode. • Proposal and verification of the theoretical basis for the operation of the DNA affinity biosensor. • Achievement of a minimum detectable concentration of 0.1 pM ss-DNA and a linear range of 0.1–1000 pM. • Selectively distinction between matched and mismatched sequences by the DNA affinity biosensor. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The mixed solution consisting of silicotungstic acid (SiW 12 for short) and γ-cyclodextrin (γ-CD) to form a novel non-covalent hybrid complex SiW 12 /γ-CD was characterized by electrospray ionization tandem mass spectrometry (ESI-MS/MS) and proton nuclear magnetic resonance spectroscopy (1H NMR) with an aim to elucidate the nature of the intermolecular interactions involved in the complex. • The solid 1:1 SiW 12 /γ-CD complex was obtained by vapor diffusion method and characterized by Fourier Transform Infrared (FT-IR) Spectroscopy. • The solid complex was then used as a catalyst in the epoxidation of cyclooctene with H 2 O 2 as oxidant. The reaction efficiency was evaluated in comparison with the single-component catalyst SiW 12. Abstract A novel non-covalent hybrid complex formed between silicotungstic acid (H 4 SiW 12 O 40 , SiW 12 , an abbreviation also for [SiW 12 O 40 ]4−) and γ-cyclodextrin (γ-CD) was investigated by means of electrospray ionization tandem mass spectrometry (ESI-MS/MS) and proton nuclear magnetic resonance spectroscopy (1H NMR). The experimental results showed that stable noncovalent complexes existing in equilibrium, [ SiW 12 + (γ-CD) m ]4− (m = 1, 2, and 3), can be formed in solution where the predominant species is the 1:1 complex. The significant chemical shift changes for the inner-cavity H-5 protons and the H-6/6′ protons on the primary faces of the CD torus in 1H NMR titration revealed that SiW 12 probably interacts with the primary faces of γ-CD through intermolecular hydrogen-bonding interactions. The gas-phase fragmentation of [ SiW 12 + (γ-CD) m ]4− showed that a proton can be transferred from γ-CD to SiW 12 within the complex upon dissociation, leading to a pair of anionic products, [H SiW 12 + (γ-CD) m-1 ]3- and [γ-CD – H]-, providing further evidence for the nature of the intermolecular interactions. The solid 1:1 adduct catalyst SiW 12 /γ-CD obtained by vapor diffusion method was then used in the epoxidation of cyclooctene to cyclooctene oxide with H 2 O 2 as oxidant as a comparison with SiW 12 alone. The result showed that the catalytic performance of SiW 12 /γ-CD is superior to SiW 12 (SiW 12 /γ-CD is about 10 times better than SiW 12), serving as the best example to demonstrate the synergistic catalysis arising from the supramolecular catalyst. [ABSTRACT FROM AUTHOR]

Zero-valent iron (ZVI) is a promising technology for groundwater treatment, and its efficiency primarily depends on the electron transfer. However, there are still some problems such as low electron efficiency of ZVI particles and high yield of iron sludge that limits the performance, which warrant further investigation. In our study, a silicotungsten acidified ZVI composite (m-WZVI) was synthesized by ball milling to activate PS to degrade phenol. m-WZVI has a better performance on phenol degradation (with a removal rate of 91.82%) than ball mill ZVI(m-ZVI) with persulfate (PS) (with a removal rate of 59.37%). Compared with m-ZVI, the first-order kinetic constant (k obs) of m-WZVI/PS is 2–3 times higher than that of the others. Iron ion was gradually leached in m-WZVI/PS system, being only 2.11 mg/L after 30 min, having to avoid excessive consumption of active substances. The underlying mechanisms of m-WZVI for PS activation mainly include: 1) were elucidated through different characterizations analyses that accounted for silictungstic acid (STA) can be combined with ZVI, and a new electron donor (SiW 12 4−) was obtained, which improved the transfer rate performance of electrons for activating PS; 2) singlet oxygen (1O 2) is the main active substance for phenol degradation, but other radicals also played an important role. Therefore, m-WZVI has good prospects for improving the electron utilization of ZVI. [Display omitted] • Silicotungsten acidified ZVI composite was successfully developed by ball milling. • m-WZVI can effectively activate PS to remove phenol in aqueous phase. • Silicotungsten on the surface of m-WZVI accelerates the electron transfer as a shuttle. • Phenol degradation is mainly attributed to 1O 2 in the m-WZVI/PS system. • The system has a wide operating pH range and good reusability. [ABSTRACT FROM AUTHOR]

Desulfurization of fossil fuel derived oil is needed in order to comply with environmental regulations. Dibenzothiophene and benzothiophene are among the predominant sulfur compound present in raw diesel oil. In this study, mixing-assisted oxidative desulfurization of dibenzothiophene and benzothiophene were carried out using polyoxometalate/H2O2 systems and a phase transfer agent. The effects of reaction time (2–30 min) and temperature (30–70 °C) were examined in the oxidation of model sulfur compounds mixed in toluene. A pseudo first-order reaction kinetic model and the Arrhenius equation were utilized in order to evaluate the kinetic rate constant and activation energy of each catalyst tested in the desulfurization process. Results showed the order of catalytic activity and activation energy of the different polyoxometalate catalysts to be H3PW12O40 > H3PM12O40 > H4SiW12O40 for both dibenzothiophene and benzothiophene.

Marine macroalgae are considered to be one of the most important biomass sources. They can grow rapidly under various conditions, leading to extensive algal blooms. In this work, a reusable solid-acid catalyst, silicotungstic acid, was used to treat the seaweed Enteromorpha prolifera. Under optimum conditions, 237.354 mg/g (23.735%) of total reducing sugar yield was obtained. The hydrolysate was used as the substrate for bioenergy production in an alkaline fuel cell, and the fuel cell achieved the maximum power density of 6.616 W/m2 under the condition of 3 M KOH and 8.572 mg/mL reducing sugar in hydrolysate, which is higher than any other reported algae-fed fuel cells. [ABSTRACT FROM AUTHOR]