磷钼钒酸盐的电子结构与催化性质的研究

本文通过CNDO/2量子化学方法对Keggin型磷钼钒酸盐的电子结构和催化性质的理论研究,导出了该类杂多化合物的价成键轨道结构普适规则,并推广到其他同多杂多化合物。本文根据对前线分子轨道和化学键性质的分析,探讨了随杂阴离子中钒原子数目的变化,磷钼钒酸盐的氧化性质和氧化催化性质变化的规律。     

Catalytic synthesis of diphenolic acid from levulinic acid over cesium partly substituted Wells–Dawson type heteropolyacid

A series of insoluble cesium partly substituted Wells–Dawson type heteropolyacids, Cs_xH_6−xP₂W₁₈O₆₂ (x = 1.5–6.0), were synthesized and characterized using the techniques including UV–vis/DRS, FT-IR, XRD, XPS, and N₂ porosimetry. As the unique and reusable solid acid catalysts, Cs_xH_6−xP₂W₁₈O₆₂ salts were applied to produce diphenolic acid by the condensation reaction of phenol with bio-platform molecule, levulinic acid. For comparison, cesium partly substituted Keggin type heteropolyacids (Cs_xH_3−xPW₁₂O₄₀, x = 1.0–3.0), HCl, HZSM-5, and MCM-49 were also tested. Influences on the catalytic activity and selectivity were considered for factors including solvent, molar ratio of phenol to levulinic acid, amount of catalyst, reaction temperature, stirring speed, and reaction time. The experimental results demonstrated that both Cs_1.5H_4.5P₂W₁₈O₆₂and Cs_2.5H_0.5PW₁₂O₄₀ exhibited excellent catalytic performance under solvent-free conditions. Furthermore, both selectivity and activity of Cs_1.5H_4.5P₂W₁₈O₆₂ were higher than those of Cs_2.5H_0.5PW₁₂O₄₀. Reasons for the different catalytic behaviors between two types of cesium partly substituted heteropolyacids were investigated.     

Preparation, luminescent, structural and electrical properties of Langmuir-Blodgett films of new organomercurial acetylide complex/heteropolyoxometalate hybrid composites

A new family of organometallic/inorganic nanohybrid Langmuir-Blodgett (LB) films consisting of rigid-rod organomercury acetylide complex (OMA) as the π-conjugated organometallic composite and heteropolyacid salts MPA (MPA = K₃PMo₁₂O₄₀, K₅BW₁₂O₄₀, Na₅IMo₆O₆₂) of the Keggin and Anderson structures as the inorganic composite, were prepared and characterized by π−A isotherms, UV−Vis absorption spectra, fluorescence spectra, scanning tunneling microscopy, atomic force microscopy imaging and low-angle X-ray diffraction. Our experimental results indicate that steady Langmuir and LB films are formed in pure water and heteropolyacid salt subphases. Luminescence spectra of hybrid LB films show that MPA can quench the emission of OMA to some extent. These alkynylmercury(II) based LB films display interesting electrical conductivity behavior. They all show decent electrical conductivity, and the tunneling current amounts to ±100 nA when the voltage is set at ±3 ∼ ±5 V.     

SiO2表面硅钼酸的稳定性和还原性

采用ＦＴ－ＩＲ、ＸＲＤ、ＢＥＴ、ＴＰＲ等方法,研究了ＳｉＯ２负载硅钼杂多酸的热稳定性和还原性。结果表明,虽然ＳｉＭｏ的负载量达到２个理论单层,但仍以非晶形态高度分散在ＳｉＯ２上;负载的硅钼酸稳定性提高,热分解温度在３５０～６００℃,同时,可还原性能降低,杂多酸的稳定性和ＴＰＲ性能相关。     

丙烯选择氧化制丙烯酸杂多酸催化剂的探索

丙烯选择氧化制丙烯酸是丙烯有效利用的途径之一 .目前工业上采用两步法生产 ,即丙烯先被氧化为丙烯醛 ,丙烯醛再被氧化为丙烯酸 .两步法中所使用的催化剂多为复合氧化物[1 ] .杂多酸催化剂由于富含晶格氧 ,有可能使丙烯一步被氧化为丙烯酸 [2 ] .其中具有 Keggin结构的杂多酸易于制备 ,化学稳定性及热稳定性好 ,被广泛用作多相选择氧化反应的催化剂 .我们选取 Keggin结构的杂多酸催化剂 ,调变其阴阳离子组成 ,用于丙烯一步氧化制丙烯酸 ,并对反应条件进行了考察 .1实验部分1 .1催化剂制备含铜、铬的杂多酸催化剂的制备方法见文献[3] .将三…     

杂多酸催化合成戊二酸二正戊酯

环已烷空气氧化生产己二酸过程中，副产大量黄绿色固体二羧酸，其中含己二酸３０％、戊二酸５０％、丁二酸２０％左右［１］，如辽阳石油化纤公司每年副产这种二羟酸几千吨，多年来一直没有很好利用。国外对二羟酸的开发利用较早，研究了各种分离二羟酸的方法［２，３］。...     

Heteropolyacid-encapsulated TiHY zeolite as an inorganic photosynthetic reaction center mimicking the plant systems

A tremendous breakthrough was required for the researchers trying to find a way to photodecomposition of water by using semiconductor photocatalysts without electricity. In this regard, we attempted to prepare the heteropolyacid (HPA)-encapsulated TiHY zeolite a new photocatalyst mimicking the plant photosynthetic system. This photocatalyst (0.3 g/40 ml) was observed to generate hydrogen (4.08±0.7 μl/h) and oxygen (6.86±0.7 μl/h) from the aqueous solutions upon illumination by two photon reactions (UV and visible lights), which is quite analogous to the “Z-scheme” mechanism for plant photosynthetic systems. The turnover number of the photocatalyst was determined to be 11 with the quantum yield of the water splitting about 27±6% at 352 nm. Thus, this inorganic material must be very useful as a reaction center mimicking the plant photosynthetic system without electrical energy.     

Acetylation of Alcohols Catalyzed by Dodeca-tungsto(molybdo)phosphoric acid

Summary. Acetylation of primary, secondary, and tertiary alcohols was carried out in some refluxing alkyl acetates and in two carboxylic acids with the participation of catalytic amounts of H₃PW₁₂O₄₀, H₃PMo₁₂O₄₀, and H₁₄P₅W₃₀O₁₁₀ with good yields and high stereo(regio)specificity under mild reaction condition. H₃PW₁₂O₄₀ and H₃PMo₁₂O₄₀ have also shown excellent reactivity in the formylation of 1-butanol with ethyl formate at room temperature and in short reaction times. Heteropolyacid catalysts could be separated after a simple work up and reused for several times.     

杂多酸引发甲氢呋喃开环聚合反应——Ⅶ.以1，1，1—三羟甲基丙烷为分子量调节剂

聚氨酯是由硬段和软段组成,其中的软段主要来源于聚醚或聚酯,通过化学交联反应可改变聚氨酯的力学性能,由过氧化物引发或使用小分子的三醇作为扩链剂对聚氨酯的硬段进行化学交联,所得聚氨酯的性能会变坏;而使用环氧丙烷（PO）与四氢呋喃（THF）的共聚醚三醇来制备在软段化学交联的聚氨酯,所得聚氨酯与由PO－THF共聚醚二醇制备的聚氨酯相比,断裂伸长率有轻微的下降,但抗拉强度得取了很大改善,由此可见,通过聚醚多元醇对聚氮酯的软段进行化学交联,有利于改善其力学性能。     

Characterizations and stability of polyimide-phosphotungstic acid composite electrolyte membranes for fuel cell

Organic-inorganic composite membranes from partially aliphatic sulfonated polyimides and heteropolyacids (HPAs) were synthesized. A series of composite membranes with varying amounts of heteropolyacid were prepared by altering the weight ratio of polyimide and HPA. The partially aliphatic sulfonated polyimides are synthesized from 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,4′-diaminobiphenyl 2,2′-disulfonic acid as the sulfonated diamine, and decamethylenediamine as the aliphatic diamine. The incorporation of HPA is confirmed by FT-IR analyses. When appropriately embedded in a hydrophilic polymer matrix, the hydrated HPAs are expected to endow the composite membrane with their high proton conductivity, while retaining the desirable mechanical properties of the polymer film. These composite membranes were evaluated for thermal stability, ion exchange capacity, water uptake and proton conductivity. Also the extraction of HPA from the polyimide membranes and their stability in water were determined. Though water uptake and IEC decreased with increase in HPA content, the proton conductivity of the composite membranes increased with increase in HPA weight content. This study shows that partially aliphatic sulfonated polyimide composite membranes with HPA can be a viable substitute for Nafion^® for fuel cells which show good conductivity comparable to Nafion^®117 at temperatures nearing 100 °C, keeping in mind that polyimides have good thermal stability and low cost.