Tungstophosphoric heteropolyacid supported onto neutral alumina: characterization and synthesis of acetals and ketals

Tungstophosphoric acid （HPW） catalyst supported on the neural alumina was studied. It was prepared by means of an equilibrium and incipient wetness impregnation technique. Solution of HPW in 50% V/V ethanol-water was used to impregnate Al2O3 at 25℃. It was found that the catalyst containing 30% PW by calcination at 500℃ showed a higher catalytic activity in the synthesis of acetals and/or ketals. In the following condition, that is, the molar ratio of aldehyde/ketone to glycol being 1：1.5, the mass fraction of the catalyst used was 0.5%, and the reaction time was 1.0 h; the yields of ketals and acetals could reach up to 60.5%-86.7%. Moreover, it could be easily recovered and reused.

Synthesis of ethyl acetate by esterification of acetic acid with ethanol over a heteropolyacid on montmorillonite K10

In present work,liquid phase esterification of acetic acid with ethanol over dodecatungestophosphoric acid （DTPA） supported on K10 montmorillonite was systematically studied and optimization of process parameters was carried out.The 20% m/m DTPA/K10 was found to be the optimum catalyst with 90% acetic acid conversion and 100% ethyl acetate selectivity.The study was also explored to see the feasibility of 20% m/m DTPA/K10 as a catalyst for the alkylation of acetic acid with other alcohols like methanol,iso-propanol and n-butanol.The 20% m/m DTPA/K10 has shown increased activity with the increase in carbon number,at the same alcohol reflux.The results are novel.

Keggin type heteropolyacids-catalyzed synthesis of quinoxaline derivatives in water

Keggin type heteropolyacids was found to be an efficient and reusable catalyst for the synthesis of biologically active quinoxaline derivatives from the condensation of 1,2-diamine with 1,2-dicarbonyl compounds in excellent yields in water. This method provides a new and efficient protocol in terms of small quantity of catalyst, a wide scope of substrates, and simple work-up procedure.

Preparation of the Supported Heteropolyacids Catalyst by Ultrasound-plasma Treatment

Novel catalysts of phosphotungstic heteropolyacids （PW12） supported on neutral alumina were prepared by assistance of ultrasound and plasma treatment. The prepared catalysts were characterized by FT-IR pyridine adsorption （Py-IR）, temperature programmed desorption of Pyridine （Py-TPD）, BET and X-ray diffraction （XRD）, and their catalytic performances were evaluated by the cationic polymerization of tetrahydrofuran. The results indicate that plasma treatment remarkably increases the surface acidity of the prepared catalyst while ultrasonic treatment induces PW12 to uniformly disperse on the support surface and expose more active sites for the acid catalytic reaction. A higher catalytic activity （69.7%） is obtained on the novel catalyst, which significantly outstripped that on the conventional sample （57.5%）.

A kinetic model for a single step biodiesel production from a high free fatty acid (FFA) biodiesel feedstock over a solid heteropolyacid catalyst

Production of biodiesel from yellow grease(waste cooking oil and waste animal fats) is fast emerging as a promising alternative to address the twin challenges before the biodiesel industry today-fluctuation in prices of vegetable oil and the food versus fuel debate. Yellow grease has a high percentage of free fatty acids(FFA) and proves to be an unsuitable feedstock for biodiesel production from commercially viable alkalicatalyzed production systems due to saponification problems.'Green' methodologies based on heterogeneous solid acid catalyzed reactions have the potential to simultaneously promote esterification and transesterification reactions of yellow grease to produce biodiesel without soap formation and offer easy catalyst separation without generation of toxic streams. This paper presents kinetic studies for the conversion of model yellow grease feeds to biodiesel using a heteropolyacid supported on alumina(HSiW/Al2O3) using a batch autoclave. Three model yellow grease feeds were prepared using canola oil with added FFA such as palmitic, oleic and linoleic acid. A pseudo homogeneous kinetic model for the parallel esterification and transesterification was developed. The rate constants and activation parameters for esterification and transesterification reactions for the model yellow grease feeds were determined. The rate constants for esterification are higher than the transesterification rate constants. The kinetic model was validated using the experimental biodiesel data obtained from processing a commercial yellow grease feed. The kinetic model could be used to design novel processes to convert various low-value waste oils, fats and non-food grade oils to sustainable biodiesel.

Heteropolyacids-Immobilized Graphitic Carbon Nitride:Highly Efficient Photo-Oxidation of Benzyl Alcohol in the Aqueous Phase

Benzaldehyde is a highly desirable chemical due to its extensive application in medicine,chemical synthesis and food sector among others.However,its production generally involves hazardous solvents such as trifluorotoluene or acetonitrile,and its conversion,especially selectivity in the aqueous phase,is still not up to expectations.Hence,developing an environmentally benign,synthetic process for benzaldehyde production is of paramount importance.Herein,we report the preparation of a photocatalyst(PW_(12)-P-UCNS,where PW_(12)is H3PW_(12)O_(40)xH_(2)O and P-UCNS is phosphoric acid-modified unstack graphitic carbon nitride)by incorporating phosphotungstic acid on phosphoric acid-functionalised graphitic carbon nitride(g-C_(3)N_(4))nanosheets.The performance of PW_(12)-P-UCNS was tested using the benzyl alcohol photo-oxidation reaction to produce benzaldehyde in H_(2)O,at room temperature(20℃).The asprepared PW12-P-UCNS photocatalyst showed excellent photocatalytic performance with 58.3%conversion and 99.5%selectivity within 2 h.Moreover,the catalyst could be reused for at least five times without significant activity loss.Most importantly,a proposed Z-scheme mechanism of the PW_(12)-P-UCNScatalysed model reaction was revealed.We carefully investigated its transient photocurrent and electrochemical impedance,and identified superoxide radicals and photogenerated holes as the main active species through electron spin-resonance spectroscopy and scavenger experiments.Results show that the designed PW_(12)-P-UCNS photocatalyst is a highly promising candidate for benzaldehyde production through the photo-oxidation reaction in aqueous phase,under mild conditions.

A Novel Synthesis of Polyaniline Doped with Heteropolyacid and its Special Property

Polyaniline doped with heteropolyacid was synthesized using solid-state synthesis method. XRD pattern showed that polyaniline molecule has highly ordered arrangement. Fluorescence property of the polyaniline materials was found.

Heteropolyacids Catalysis in Synthesizing Butylacrylate

The catalytic activities of some heteropolyacids(HPAs) in synthesizing butyl acrylate are reported. It has been demonstrated that 12 tungstophosphoric acid is the most effective catalyst among more than 20 HPA(salts). Various factors concerned in this reaction have been investigated. The optimum conditions have been found, that is, the molar ratio of alcohol to acid is 1.2∶1.0 , the catalyst concentration 1%(mass fraction), the reaction time 2 h, the temperature 98—124 ℃ and a certain amount of polymerization inhibitor exists.

High dispersion of heteropolyacid nanoparticles on hydrothermally Cs-modified three-dimensionally ordered macroporous SiO2 with excellent selectivity in methacrolein oxidation

Heteropolyacid nanoparticles(NPs)were supported on Cs-modified three-dimensionally ordered macroporous(3DOM)SiO2 and used as the catalyst for the oxidation of methacrolein(MAL)to methacrylic acid(MAA).Hydrothermal treatment and incipient wetness impregnation were employed respectively for the Cs-modification.It was found that hydrothermal Cs-modification of 3DOM SiO2 promoted the dispersion of the supported heteropolyacid,which showed an average particle size of 5.2 nm,much smaller than that(17.6 nm)on the Csmodified 3DOM SiO2 prepared by incipient wetness impregnation.The effects of hydrothermal treatment on the structure and catalytic performance of the catalyst were investigated.Results showed that the ion exchange between Cs+and the surface silanol groups on 3DOM SiO2 was promoted with the increase of the hydrothermal temperature.Meanwhile,Cs-modification helped the heteropolyacid to retain intact Keggin structure,inhibiting the formation of MoO3.Highly dispersed heteropolyacid NPs with enhanced structural stability exhibited excellent selectivity to MAA in the oxidation of MAL.

Etherification of Methanol with Propylene Oxide Catalyzed by Heteropolyacids

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Hydrothermal Synthesis and Characterization of a Novel Organically-templated Tungsten Heteropolyacid with a Microporous Structure

A microporous organically-templated tungsten heteropolyacid, (C2N2H10)2 [H2P2W18O62]?8H2O, with a new type was hydrothermally synthesized by using ethylenediamine as the structure-directing agent. Its structure was determined by single-crystal X-ray diffraction analysis. Crystal data: monoclinic, space group P21/c, a = 14.633(4), b = 19.432(5), c = 26.776(5) ?, β = 117.849(11)o, V = 6732(3) ?3, Z = 4, Mr = 4615.48, Dc = 4.554 g/cm3, μ(MoKα) = 30.781 mm-1, F(000) = 7976, the final R = 0.0678 and wR = 0.1359. The crystal of the title compound is constructed by Dawson anions and organic dications forming a novel “hollow” channel system.

Coupling biomass pretreatment for enzymatic hydrolysis and direct biomass-to-electricity conversion with molybdovanadophosphoric heteropolyacids as anode electron transfer carriers

Owing to their acidity,oxidizing ability and redox reversibility,molybdovanadophosphoric heteropolyacids(H_(n+3)PMo_(12-n)VnO40,abbreviated as PMo_(12-n)Vn) were employed as electron transfer carriers for coupling biomass pretreatment for enzymatic hydrolysis and direct biomass-to-electricity conversion.In this novel coupled process,PMo_(12-n)Vn pretreatment that causes deconstruction of cell wall structure with PMo_(12-n)Vn being simultaneously reduced can be considered as the "charging" process.The reduced PMo_(12-n)Vn are further re-oxidized with release of electrons in a liquid flow fuel cell(LFFC) to generate electricity is the "discharging" process.Several Keggin-type PMo_(12-n)Vn with different degree of vanadium substitution(DSV, namely n) were prepared.Compared to Keggin-type phosphomolybdic acid(PMo_(12)),PMo_(12-n)Vn(n=1-6) showed higher oxidizing ability but poorer redox reversibility.The cellulose enzymatic digestibility of PMo_(12-n)Vn pretreated wheat straw generally decreased with increase in DSV, but xylan enzymatic digestibility generally increased with DSV.PMo_(12) pretreatment of wheat straw at 120℃ obtained the highest enzymatic glucan conversion(EGC) reaching 95%,followed by PMo11V1 pretreatment(85%).Discharging of the reduced heteropolyacids in LFFC showed that vanadium substitution could improve the maximum output power density(Pmax).The highest Pmax was obtained by PMo9 V3(44.7 mW/cm^(2)) when FeCl_(3) was used as a cathode electron carrier,while PMo_(12) achieved the lowest Pmax(27.4 mW/cm^(2)).All the heteropolyacids showed good electrode Faraday efficiency(>95%) and cell discharging efficiency(>93%).The energy efficiency of the coupled process based on the heat values of the products and generated electric energy was in the range of 18%-25% depending on DSV.PMo_(12) and PMo11V1 seem to be the most suitable heteropolyacids to mediate the coupled process.

One-Pot Process of Naphthoquinones Synthesis from Hydroquinone in the Presence of Solutions of Mo-V-P Heteropolyacids as Bifunctional Catalysts

1,4-Naphthoquinones (NQ) is a class of organic compounds with a number of important properties. However, the existing methods of their synthesis either give a low NQ yield or multistage and require a lot of time. In the present work new one-pot process of NQ synthesis from hydroquinone (HQ) and substituted 1,3-dienes at room temperature is proposed. The solution of heteropolyacid H7PMo8V4O40 (HPA-4) is used as a bifunctional (acid and redox) catalyst for this process. The influence of a number of factors on key process parameters has been studied. It is demonstrated that unsubstituted and a number of alkyl substituted NQ with the yields of 50% - 80% and purity of 92% - 99% can be obtained by this method. The results obtained allow to significantly simplify the synthesis of NQ directly from HQ in comparison with the described similar methods.

杂多酸型离子液体杂化材料的第一性原理研究

构建了三种同系杂多酸型离子液体模型,随后用密度泛函理论分析并讨论了它们微观结构、结合能、载流子有效质量.结果表明杂多酸的取代配位原子数目会对杂化物的性质产生较大影响.在钼取代的磷钨酸中,当钼取代数目低时,杂化物载流子有效质量较低,呈较强的导电性.高钼取代数时载流子的相对质量较大,因此传输阻力增大,其导电性于低钼取代数目的杂化物.以此对所合成材料的性质进行预测与验证,为以后合成、分析这类物质提供理论依据和指导作用.

离子液体多酸在燃油氧化脱硫中的研究进展

氧化脱硫,因其反应条件温和、成本较低等特点被广泛应用于燃油脱硫领域。近年来,有研究者发现离子液体中的阴阳离子结构具有可调性,可借此通过物理化学法制备出高效的催化剂,为更深度的氧化脱硫提供有利条件。本文总结了离子液体多酸的合成与分类,详细叙述了单纯离子液体多酸和以金属有机框架或无机非金属材料为载体的负载型离子液体多酸的特点以及目前其在燃油氧化脱硫领域的研究进展,包括脱硫率和重复使用次数等脱硫效果。单纯离子液体多酸的初次脱硫效率都在80%以上,最高可达99.2%,而负载后的离子液体多酸的脱硫率都在98%以上,大多数高达100%,重复利用次数最高可达13次。众多研究者一致认为负载型离子液体多酸不仅能有效增强多酸的催化活性,而且可提高催化剂的热稳定性与重复利用性,在燃油氧化脱硫中有着良好的使用效果。最后对离子液体多酸在氧化脱硫领域的发展方向提出了展望,指出了具有良好催化性能、可重复利用性好、绿色高效的离子液体多酸是未来的研究方向,为进一步研究离子液体多酸提供了参考。

锌系杂多酸离子液体催化合成聚戊二酸乙二醇酯的研究

制备了4种锌系杂多酸离子液体催化剂,利用FT-IR、UV、TGA及SEM对其进行表征与测试。将4种杂多酸离子液体用于催化戊二酸二甲酯与碳酸乙烯酯反应合成聚戊二酸乙二醇酯,并利用FT-IR、TGA、DSC、CTM、GPC对聚戊二酸乙二醇酯进行测定分析。结果表明,[Bmim]_(6)ZnW_(11)TiO_(39)(H_(2)O)催化剂催化效果最佳,在220℃、4.5 h、戊二酸二甲酯与碳酸乙烯酯的投料摩尔比为1∶1.5、催化剂质量为总投料质量的0.8%的条件下,聚戊二酸乙二醇酯的预聚物收率达到59.27%,选择性达到63.59%。缩聚反应的温度为235℃时聚酯分子质量达到最高,且具有良好的热稳定性能、拉伸性能及可生物降解性能。

Improved Activity Assay Method for Arginine Kinase Based on a Ternary Heteropolyacid System

This paper presents a new system for the activity assay of arginine kinase (AK), based on the spectrophotometric determination of an ascorbic acid reduced blue ternary heteropolyacid composed of bismuth, molybdate and the released phosphate from N phospho L arginine (PArg) formed in the forward catalysis reaction. The assay conditions, including the formulation of the phosphate determination reagent (PDR), the assay timing, and the linear activity range of the enzyme concentration, have been tested and optimized. For these conditions, the ternary heteropolyacid color is completely developed within 1 min and is stable for at least 15 min, with an absorbance maximum at 700 nm and a molar extinction coefficient of 15.97 (mmol/L) -1 ·cm -1 for the phosphate. Standard curves for phosphate show a good linearity of 0.999. Compared with previous activity assay methods for AK, this system exhibits superior sensitivity, reproducibility, and adaptability to various conditions in enzymological studies. This method also reduces the assay time and avoids the use of some expensive instruments and reagents.

Sulfonated poly(4-vinylpyridine) heteropolyacid salts:A reusable green solid catalyst for Mannich reaction

Sulfonated poly（4-vinylpyridine） heteropolyacid salts acted as a heterogeneous catalyst to effectively catalyze the one-pot synthesis of β-amino carbonyl compounds via the Mannich reaction between aromatic aldehydes, aromatic ketone, and aromatic amines. In addition, the catalyst could be easily recovered by the filtration and reused six times without significant loss of catalytic activity.

Heteropolyacids supported on hierarchically macro/mesoporous TiO_(2):efficient catalyst for deep oxidative desulfurization of fuel

The fabrication of polyoxometalates(POMs)-modified TiO_(2)catalysts with connected pore structure has attracted great interests due to its prominent effect on mass transfer and catalytic oxidation activity.Here,we report a series of hierarchically macro/mesoporous(M/m)phosphotungstic acid(HPW)/TiO_(2)composites,which are fabricated by colloidal crystal template method and applied as deep desulfurization catalyst in fuel oil.As-synthesized hierarchical HPW/TiO_(2)composite is interconnected by ordered macroporous channel with disordered mesoporous embedded on pore walls.Moreover,Keggintype HPW is homogeneously dispersed on the TiO_(2)matrix.Hierarchical macro/mesoporous HPW/TiO_(2)shows an excellent catalytic performance,the removal rate for dibenzothiophene in model fuel reaches 99%under the optimum conditions.This high performance of the three-dimensional ordered macropores(3DOM)HPW/TiO_(2)can be attributed to its hierarchically porous which is highly beneficial for the mass transfer during the catalytic process.Moreover,the used catalyst could be regenerated by centrifugation and only slight decreasing of the catalytic activity after five cycles.