杂多酸(盐)用于油品氧化脱硫的研究进展

综述了杂多酸(盐)催化剂的结构特征及催化特性,包括磷钨酸(盐)体系、磷钨酸(盐)/季铵盐体系、磷钨酸季铵盐体系、负载型磷钨酸体系、磷钼酸(盐)体系、杂原子改性杂多酸体系等。介绍了几种类型杂多酸(盐)在油品氧化脱硫中的应用进展,并指出了其现存的问题及今后的研究方向。     

紫外分光光度法在固载杂多酸催化剂溶脱量测定中的应用

采用紫外分光光度法测定了乙酸乙酯催化体系中磷钨酸阴离子的舍量.结果表明,6次反应后杂多酸基本上不再从载体上脱落下来,这与实验结果完全相符.这就充分说明采用紫外分光光度法能够较好地测定该反应体系中目载杂多酸催化剂中杂多酸的溶脱程度.     

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 Cs-modified 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.     

Performance of potassium 12-tungstophosphoric salts as catalysts for isobutane/butene alkylation in subcritical and supercritical phases

Potassium salts of H₃PW₁₂O₄₀ heteropolyacid have been synthesised with different K contents and studied for their acid and catalytic properties in liquid phase isobutane alkylation by but-2-ene or but-1-ene. Subcritical and supercritical conditions have been chosen for comparison in a batch reactor.

The influence of the protonic site density has been studied. High acid density was observed to be detrimental for akylation reaction which was explained by increased olefin dimerisation, the main side reaction responsible of catalyst poisoning. A K_2.6H_0.4P sample was tested in a batch reactor in liquid subcritical, near supercritical and in low and high density supercritical isobutane/butene mixture (418 K, P=4–9 MPa). An increase in the quality of the alkylate with the density of the supercritical phase was observed which almost counterbalanced the negative effect of the high temperature necessary to reach supercritical isobutane conditions.

In the presence of porous alkaline salts of 12-tungstophosphoric acid, alkylation to oligomerisation ratio is significantly improved over solids with a low density of strong Brønsted sites and by the use of high density supercritical isobutane conditions, the latter preserving hydride transfer and trimethyl pentane (TMP) formation.     

Recent progress in the practical applications of heteropolyacid and perovskite catalysts: Catalytic technology for the sustainable society

Recent progresses in practical applications of (i) supported heteropolyacid and (ii) Pd/perovskite catalysts are described. (i) Two industrial catalytic processes, ethyl acetate and acetic acid syntheses both from ethylene, utilize silicotungstic acid, alone and together with Pd, respectively, carefully supported on silica, and exhibit high performance from green chemical and economical viewpoints. The layer structure of heteropolyacid on silica and physical properties of silica are among the key factors of the high performance. (ii) Pd/perovskite catalyst is applied for the treatment of automotive emission, where the catalyst life is very much elongated by embedding Pd into the perovskite lattice and hence resulted in much reduced usage of Pd. These are good examples of green catalytic technology that will contribute to the sustainable society.     

Simulation of NO and NO2 sorption–desorption–reduction behaviours on Pt-impregnated HPW supported on TiO2

NO and NO₂ (NO_x) sorption, desorption and reduction by hydrogen, carbon monoxide and/or propene were investigated on a TiO₂-supported heteropolyacid, 12-tungstophosphoric acid hexahydrate (HPW), promoted by platinum. A model taking into account NO_x sorption, desorption and reduction was established. Kinetic constants for NO_x sorption, desorption and reduction were extracted by modelling for the investigated range of temperature (170–300 °C).     

Heterogenization of 12-tungstophosphoric acid on stabilized zeolite Y

Topics in Catalysis - 12-tungstophosphoric acid (PW12) has been supported on dealuminated zeolite Y, containing a secondary pore system with the predominant pore radii of 15 Å. The interaction...     

Sorption–desorption of NO x from a lean gas mixture on H3PW12O40 · 6H2O supported on carbon nanotubes

Topics in Catalysis - NO x sorption capacities and efficiencies were measured on a new type of sorbent formed by 12-tungstophosphoric acid (HPW) supported on carbon nanotubes. On such a system, the...     

Novel gallium and indium salts of the 12-tungstophosphoric acid: Synthesis,characterization and catalytic properties

The objective of this study was the preparation, characterization and testing of the catalytic properties of the GaPW₁₂O₄₀ and InPW₁₂O₄₀ salts of 12-tungstophosphoric heteropolyacid (HPW). The samples were characterized by XRD, IR, SEM, and ³¹P and ¹H MAS NMR spectroscopy. The acid properties of the solids were directly accounted for by applying ¹H MAS NMR. The salts were screened in the etherification of 1-phenylethanol with C₁–C₄ alkanols in dichloromethane as a solvent to yield the corresponding C₆H₅CH(OR)CH₃ unsymmetrical ethers. In comparison with pure HPW, the new salts revealed generally a higher selectivity of ethers formation at 65 °C.     

杂多酸对丙烯酸酯合成的催化、阻聚作用

本文研究了以杂多酸为催化剂 ,合成丙烯酸酯的工艺条件 ,及其对丙烯酸酯的阻聚作用。     

杂多酸-金属双功能催化剂在庚烷异构化中的研究进展

简述了双功能催化剂上正庚烷的异构化机理,综述了负载杂多酸和金属的MCM-41、SiO2、USY、ZrO2、TUD-1、β沸石双功能催化剂上正庚烷异构化的研究进展,重点介绍了正庚烷异构化中杂多酸-金属双功能催化剂催化性能的影响因素。包括催化剂酸性、孔结构、杂多酸含量、金属含量、反应条件等。对杂多酸-金属双功能催化剂的优点和不足进行了总结,并预测了该类催化剂的发展趋势。     

Effect of water on silica-supported phosphotungstic acid catalysts for 1-butene double bond shift and alkane skeletal isomerization

The thermal stability, acidity, catalytic activity and regenerability of silica-supported phosphotungstic acid were evaluated in reference to the bulk solid acid. Samples were prepared with 5, 10, and 25 wt.% heteropolyacid (HPA) on fumed silica to examine the effect of loading on the properties of supported acid catalysts. X-ray absorption spectroscopy indicated that the supported heteropolyacids did not completely decompose when heated to 573 K. The catalytic activity of both bulk and supported HPAs for double bond shift and skeletal isomerization of light hydrocarbons decreased with increasing pretreatment temperatures, which suggests that the level of hydration is critical for acid catalysis. After pretreatment at 573 K, a well dispersed sample (5 wt.% HPA) catalyzed 1-butene double bond isomerization, a reaction that requires weak acid sites, whereas the sample was inactive for pentane skeletal isomerization, a reaction that requires strong acid sites. Evidently, the well dispersed HPAs did not have sufficient acidity to catalyze pentane isomerization since higher loaded samples were active for the reaction under identical conditions. Ammonia sorption microcalorimetry results correlated well with reactivity, revealing that 5 wt.% HPA on silica had the lowest heat of ammonia sorption, while a 25 wt.% sample had initial heats near that of bulk heteropolyacid (150 kJ mol⁻¹). Treatment of the catalysts with water at mild conditions recovered activity for the bulk and supported heteropolyacids for the 1-butene and pentane isomerization reactions whereas treatment in air or N₂O was ineffective. These findings suggest that water treatment regenerates acid sites by rehydrating partially decomposed Keggin units. Results from in situ UV–VIS spectroscopy of the catalyst samples support the above conclusion.     

The interaction of alkaline earth cations with metal-oxygen cluster compounds and the implications for their use as heterogeneous catalysts

The magnesium, calcium, strontium and barium salts of 12-tungstophosphoric and 12-molybdophosphoric acids have been prepared. Evidence of the presence of the Keggin anion (primary structure) was obtained from infrared spectroscopic measurements but powder X-ray diffraction and differential thermal analysis measurements indicated that changes to the secondary structure had occurred. BET surface areas were small for all of the materials studied and no dependence on the cation radius was observed. A crystallographic investigation demonstrated that divalent cations were not incorporated into the lattice suggesting that materials believed to be divalent 12-heteropoly salts are mixtures of the parent acid and a divalent cation salt.     

Heteropolyacid salts catalysts supported on silylated attapulgite for cyclohexane oxidation

以硅烷化凹凸棒黏土为载体,满孔浸渍法制备了负载型杂多酸盐催化剂,采用X射线衍射、比表面积测定、傅里叶变换红外光谱等手段对催化剂进行了表征。分别考察了双氧水用量、杂多酸盐负载量及循环使用次数等因素对环己烷氧化反应的影响。结果表明,负载型杂多酸盐CoH₇P₂Mo₁₅V₃O₆₂能显著提高环己烷氧化能力;催化剂回收烘干后可直接重复利用,催化活性没有明显降低。在优化条件下,环己烷转化率达到35.28%,目标产物环己醇和环己酮的总收率达到12.48%。实验表明,负载型杂多酸盐CoH₇P₂Mo₁₅V₃O₆₂是一种具有应用前景的催化剂,便于与产物分离,且对设备和环境污染小。     

Study of the Keggin structure and catalytic properties of Pt-promoted heteropoly compound/Al-MCM-41 hybrid catalysts

Aluminum-containing mesoporous molecular sieves (referred as WSAn, where n = Si/Al molar ratio = 50, 30 and 10) were synthesized via a surfactant templated approach by using fumed silica and aluminum sulfate as Si and Al precursors, respectively. When the 12-tungstophosphoric acid was grafted onto the surface of WSAn, a high dispersion of the heteropolyacid was achieved on the heteropoly compound/WSAn hybrid catalysts. The Keggin structure of the dispersed 12-tungstophosphoric acid was primarily preserved without destruction, but it was distorted in some degree, as confirmed by FTIR, ³¹P NMR-MAS and UV–vis spectroscopic characterizations. The surface Brönsted acidity of the catalysts was greatly enhanced by several times in comparison to that of the bare WSAn support. In the hydroisomerization reaction of n-heptane, the Pt/H₃PW₁₂O₄₀/WSA30 catalyst exhibited the highest catalytic activity and the best isomerization selectivity among the catalysts tested, which can be generally correlated with its large number of Brönsted acid sites and high structural regularity. After the n-heptane hydroisomerization reaction, a high molar ratio of multibranched to monobranched isohexanes was obtained, indicating that Pt-promoted heteropoly compound/WSAn hybrid catalysts have a great potential for the hydroisomerization of long carbon chain hydrocarbons.     

2,2-二(4-羟基苯基)丁烷的催化合成

以活性炭固载磷钨杂多酸为催化剂,苯酚和丁酮为原料,催化缩合了2,2-二(4-羟基苯基)丁烷(双酚B),并使用红外光谱法鉴定了产物的化学结构。通过正交试验筛选出最优反应条件,在此基础上考察了助催化剂巯基乙酸对产物收率的影响及催化剂的稳定性。最终确定的反应条件为:苯酚与丁酮摩尔比为8∶1,催化剂用量为反应物总质量的12%,助催化剂巯基乙酸与丁酮的摩尔比为0.014∶1,反应温度为130℃,反应时间为7 h,产物收率可达56.7%。     

活性炭固载杂多酸催化剂的研究现状

杂多酸是一类同时具有酸催化特性和氧化一还原能力的催化剂，有着广泛的应用前景。杂多酸固载化后，能够在液相氧化和酸催化反应中把催化剂从反应介质中很方便地分离出来，且能使这类均相催化反应多相化。本文介绍了以活性炭为载体的固载型杂多酸催化剂的研究状况，包括制备方法、影响负载量的因素及负载量对催化性能的影响，文章同时阐述了有关活性炭固载杂多酸的机理分析，总结了近年来活性炭固载杂多酸催化剂的应用研究及进展。     

Activation of propane and butanes over niobium- and tantalum-based oxide catalysts

Niobium and tantalum are important elements for the activation of alkanes in the viewpoints of acidic property and the formation of unique mixed metal oxides. And the difference of the ability of alkane activation between niobium- and tantalum-based oxide catalysts is studied. Although hydrated niobium and tantalum oxides show strong acid property, only hydrated tantalum oxide is activated to a solid superacid by the treatment with sulfuric acid, and isomerizes n-butane to isobutane at room temperature. The sulfuric acid treated tantalum oxide activates P–Mo–V heteropolyacid compounds for the selective oxidation of isobutane to methacrolein (MAL) and methacrylic acid (MAA). The difference of ability of alkanes activation between niobium and tantalum is studied by using surface science technique. Mo–V–Nb–Te mixed metal oxide catalysts are active for the ammoxidation of propane to acrylonitrile (AN). However, Mo–V–Ta–Te mixed metal oxide is less active. The effect of catalyst preparation condition is studied. Mo–V–Nb–Te mixed metal oxide catalysts are also active for the oxidation of propane to acrylic acid (AA).     

负载型磷钨杂多酸的制备及在醚化反应中的应用

以活性炭为载体,制备了催化剂Ｈ３ＰＷ１２Ｏ４０（ＰＷ１２）／Ｃ,并进行了混合烯烃与甲醇的醚化反应。研究了制备条件、ＰＷ１２负载量对催化活性的影响,并对醚化反应条件进行了系统考察。     

改性凹凸棒石固载杂多酸钴盐催化合成苯乙酮的研究

以硅烷偶联剂3-氨丙基三乙氧基硅烷改性的活性凹凸棒石（PG）为载体,采用浸渍法制备了负载型杂多酸钴盐Co4HP2 Mo15V3O62(CoHPAs)催化剂(CoHPAs/MPG),对催化剂进行红外光谱表征。考察了反应条件对合成苯乙酮的影响。结果表明：负载型杂多酸盐CoHPAs/MPG具有较好的催化活性,乙苯的转化率为72.74 %,苯乙酮的选择性达到95.42 %。且催化剂具有较高的稳定性,重复使用5次后催化活性未见明显下降,有一定的应用前景。