溶胶凝胶法制备的Cu/SiO2催化剂及其催化草酸二甲酯加氢反应

采用溶胶凝胶法制备了用于草酸二甲酯加氢合成乙二醇的Cu/SiO2催化剂,在优化的反应条件下,当催化剂中Cu含量为15%～25%时,草酸二甲酯转化率和乙二醇选择性分别达到99.9%和95.0%.通过N2吸附-脱附、透射电镜、X射线衍射、氢气程序升温还原、N2O滴定法和X射线光电子能谱等手段对各Cu/SiO2催化剂进行了表...     

Synthesis of a triblock copolymer: Poly(ethylene glycol)‐poly(alkylene phosphate)‐poly(ethylene glycol) as a modifier of CaCO3 crystallization

Triblock copolymer poly(ethylene glycol)‐poly(alkylene phosphate)‐poly(ethylene glycol) was prepared by first reacting hexamethylene glycol with dimethyl‐H‐phosphonate at conditions of transesterification and then replacing the CH₃OP(O)(H)O‐… end‐groups by monomethyl ether of poly(ethylene glycol). The course of reaction was studied by ³¹P NMR indicating complete conversion. After oxidation the poly(alkylene H‐phosphonate was converted into the final triblock polyphosphate. This triblock copolymer was used as a modifier of CaCO₃ crystallization. Unusual semi open empty spheres resulted, composed of small crystallites of the size (diameter) equal to 40–90 nm. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 650–657, 2005     

Novel copolymer networks via the combination of polyaddition and anionic polymerization

A two‐step synthetic route to novel copolymer networks, consisting of polymethacrylate and polyacetal components, was developed by combining the polyaddition and anionic polymerization techniques. The functional polymethacrylates containing hydroxyl or vinyloxyl side groups were used as crosslinkers. They were anionically synthesized as follows: the copolymer of 2‐hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA) was prepared by the anionic copolymerization of 2‐(trimethylsiloxy)ethyl methacrylate and MMA, followed by hydrolysis. The copolymer poly(HEMA‐co‐MMA) thus obtained possessed a hydroxyl group in each of its HEMA units. Another kind of vinyloxyl‐containing (co)polymer was prepared by the anionic homopolymerization of 2‐(vinyloxy)ethyl methacrylate (VEMA) or its copolymerization with MMA. The resulting (co)polymer possessed reactive vinyloxyl side groups. The copolymer networks were obtained by reacting each of the above‐mentioned (co)polymers with a polyacetal prepared via the polyaddition between a divinyl ether and a diol. Three divinyl ethers (ethylene glycol divinyl ether, 1,4‐butanediol divinyl ether, and 1,6‐hexanediol divinyl ether) and three diols (ethylene glycol, 1,4‐butanediol, and 1,6‐hexanediol) were employed as monomers in the polyaddition step, and their combinations generated nine kinds of polyacetals. When a polyaddition reaction was terminated with a divinyl ether monomer, a polyacetal with two vinyloxyl end groups was obtained, which could further react with the hydroxyl groups of poly(HEMA‐co‐MMA) to generate a copolymer network. On the other hand, when a diol was used as terminator in the polyaddition, the resulting polyacetal possessed two hydroxyl end groups, which could react with the vinyloxyl groups of poly(VEMA) or poly(VEMA‐co‐MMA), to generate a copolymer network. All the copolymer networks exhibited degradation in the presence of acids. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 117–126, 2001     

A column packing for isothermal gas chromatographic analysis of C1−C5 paraffins and monoolefins and dimethyl ether

Summary An analytical GC method was developed which uses a single packed column consisting of three packings in series prepared with the following liquid phases: dimethyl sulfolane, propylene carbonate, and silver nitrate. This system provides satisfactory resolution of mixtures of C₁–C₅ hydrocarbons and dimethyl ether obtained when converting methanol to gasoline. Due to the high capacity of the column it is possible to inject larger sample amounts permitting trace analysis.     

Thermophysical properties of methanol+some polyethylene glycol dimethyl ether by UNIFAC and DISQUAC group-contribution models for absorption heat pumps

Several group-contribution models including three different versions of UNIFAC, GC-UNIMOD and DISQUAC are tested for their capabilities of predicting vapour–liquid equilibria, excess enthalpies and viscosities of methanol+some polyethylene glycol dimethyl ethers over a wide range of temperature. Also, the literature experimental thermophysical property database of these serial systems are collected, and new experimental excess enthalpies of methanol+pentaethylene glycol dimethyl ether at 303.15 K and densities and kinematic viscosities of methanol with monoethylene glycol dimethyl ether, triethylene glycol dimethyl ether, or pentaethylene glycol ether at 303.15 K are reported as a supplement to this experimental database. The predictions for vapour–liquid equilibria and excess enthalpies from modified UNIFAC of Gmehling et al. are the best, yielding the average relative deviation around 3% for vapour pressure and 30% for excess enthalpy. GC-UNIMOD viscosity group-contribution model gives the average relative deviation around 20% for viscosity predictions of the studied systems     

Sulfur-containing polymers. IV. Preparation and properties of poly(sulfenyl thiocarbonates)

Poly(sulfenyl thiocarbonates) have been prepared for the first time by the stepwise condensation of chlorocarbonylsulfenyl chloride with diols and dithiols. The polymers were obtained in high yield. Generally they were crystalline solids and were soluble in chlorinated hydrocarbons. On treatment with benzyl mercaptan in the presence of triethylamine, the polymers afforded a diol, carbonyl sulfide, and a disulfide compound. This reaction was extended to the preparation of alternating copolydisulfides.     

琥珀酸酐均相加氢制备γ-丁内酯的研究

研究了不同催化剂对琥珀酸酐加氢生成γ -丁内酯的反应 ,并考察了配体、溶剂及PPh3/Ru摩尔比对催化反应的影响。结果发现Ru络合物是最佳催化剂 ,PPh3是最佳配体 ,乙二醇二甲醚为最佳溶剂。在SA ,2 0mmol;催化剂Ru ,0 .10mmol;PPh3/Ru ,8;以乙二醇二甲醚为溶剂( 8ml) ;H2 ,3.0MPa ;反应温度为 12 0℃的反应条件下 ,γ -丁内酯的产率可达 86.5%。     

Solvent Effect and Reactivity Trend in the Aerobic Oxidation of 1,3‐Propanediols over Gold Supported on Titania: NMR Diffusion and Relaxation Studies

In recent work, it was reported that changes in solvent composition, precisely the addition of water, significantly inhibits the catalytic activity of Au/TiO₂ catalyst in the aerobic oxidation of 1,4‐butanediol in methanol due to changes in diffusion and adsorption properties of the reactant. In order to understand whether the inhibition mechanism of water on diol oxidation in methanol is generally valid, the solvent effect on the aerobic catalytic oxidation of 1,3‐propanediol and its two methyl‐substituted homologues, 2‐methyl‐1,3‐propanediol and 2,2‐dimethyl‐1,3‐propanediol, over a Au/TiO₂ catalyst has been studied here using conventional catalytic reaction monitoring in combination with pulsed‐field gradient nuclear magnetic resonance (PFG‐NMR) diffusion and NMR relaxation time measurements. Diol conversion is significantly lower when water is present in the initial diol/methanol mixture. A reactivity trend within the group of diols was also observed. Combined NMR diffusion and relaxation time measurements suggest that molecular diffusion and, in particular, the relative strength of diol adsorption, are important factors in determining the conversion. These results highlight NMR diffusion and relaxation techniques as novel, non‐invasive characterisation tools for catalytic materials, which complement conventional reaction data.     

Protic ionic liquid-promoted synthesis of dimethyl carbonate from ethylene carbonate and methanol

In this work,the protic ionic liquid[DBUH][Im](1,8-diazabicyclo[5.4.0]-7-undeceniumimidazolide)was developed as an efficient catalyst for the transesterification of ethylene carbonate with methanol to produce dimethyl carbonate.At 70℃,up to 97%conversion of ethylene carbonate and 91%yield of dimethyl ca rbonate were obtained with 1 mol%[DBUH][Im](relative to ethylene carbonate)as catalyst in 2 h.Even at room temperature,the conversion of ethylene carbonate can reach 94%and the yield of dimethyl carbonate can approach 81%for 6 h.Catalytic mechanism investigation showed the high catalytic efficiency of this ionic liquid results from the synergistic activation effect,wherein the cation can activate ethylene carbonate and the anion can activate methanol through hydrogen bond formatio n.Although the reusability of the ionic liquid need to be further improved,high efficiency and comme rcial availability of[DBUH][Im]render it a promising catalyst for the preparation of dimethyl carbonate.     

介孔/大孔Al2O3-SiO2复合氧化物的制备与表征

 以正硅酸甲酯和硝酸铝为硅和铝的前驱体,以非离子表面活性剂C16EO10为结构导向剂,采用溶胶-凝胶法制备了双孔结构硅铝复合氧化物材料. 扫描电镜和N2吸附/脱附分析表明,材料具有三维连续大孔和骨架介孔的双孔分布结构. 微米范围的连续大孔结构是由于溶胶-凝胶过程中诱发了Spinodal相分离所致,而骨架介孔的形成则可能是由于表面活性剂分子进入凝胶骨架中,起到构建介孔结构的模板作用. 骨架元素分析结果表明,制备过程中添加的铝大部分进入了凝胶骨架中,取代部分硅而形成酸性硅铝复合氧化物. 采用Hammett指示剂法和吡啶吸附红外光谱法分析了材料的表面固体酸性,结果显示,硅铝复合氧化物属于中强酸,酸强度H0在-5.6～-3.0 之间的酸中心数约为0.35 mmol/g, 并且材料表面的L酸位较为丰富, B酸位相对较少.     

Negative-ion electrospray and fast atom bombardment mass spectrometry of esters of boron acids

It is shown that both electrospray and fast atom bombardment mass spectrometry provide excellent negative-ion mass spectra of the anionic esters of boric, boronic and borinic acids. For electrospray, contact of the esters with water causes some hydrolysis but, in most cases, spectra of the intact molecular anions are readily obtained. For fast atom bombardment, solvents that chelate with the boron esters must be avoided, Tetraethylene glycol diethyl ether, pentaethylene glycol dimethyl ether or hexaethylene glycol dimethyl ether are suitable solvents. Negative-ion electrospray mass spectra showed few, if any, fragment ions, whereas fast atom bombardment generally produced abundant M^? ions and several fragment ions of low abundance. It is shown that a simple reaction with dibenzene-borinic acid converts diols such as monoglycerides and monoalkyl glyceryl ethers into anionic borinate esters as a pre-ionization procedure for analysis by electrospray or fast atom bombardment mass spectrometry.     

Conversion of Oxygenates to Aromatic Hydrocarbons on a Commercial Zeolite Catalyst: Comparison of Ethanol and Dimethyl Ether

Conversion of oxygenates to aromatic hydrocarbons in the syngas medium in the presence of a commercial zeolite-containing catalyst was studied. The influence of pressure on aromatization of dimethyl ether and ethanol was examined. At 400°C, an increase in the pressure from 0.1 to 3.0–10.0 MPa leads to a sharp increase in the yield of aromatic compounds. Dimethyl ether and ethanol, which are isomers belonging to different classes of compounds, were compared as substrates in conversion to aromatic hydrocarbons. At elevated pressure, dimethyl ether compared to ethanol exhibits higher selectivity in formation of the desired synthesis products, allowing synthesis of liquid hydrocarbons with increased content of arenes.

     

The influence of furanyl monomer on the self‐healing polyurethanes by reverse Diels‐Alder cross‐link

In this work, several furanyl diols with amide, imide, or amine groups were synthesized, each diol was subsequently polymerized with 4,4′‐dicyclohexylmethane diisocyanate and polytetramethylenene ether glycol to prepare polyurethanes. Bis(4‐maleimidophenyl) methane was then added as a cross‐linker to give self‐healing polyurethanes. DSC and DMA analysis were used to measure the DA/rDA temperature of these polyurethanes with different chemical structures. It was demonstrated that the polyurethane prepared from amide furanyl diol had the highest DA/rDA temperature, followed with the order of amide > imide > amine. This expands the versatility of monomers that have different self‐healing activity, which is expected to have the application for preparing various polyurethane coatings.     

Heterogeneous Cu_2O-mediated ethylene glycol production from dimethyl oxalate

An efficient process for the conversion of dimethyl oxalateinto ethylene glycol with high selectivity and high yield over Cu_2O was investigated. In situ formed Cu as a true catalytically active species showed a good catalytic performance for DMO conversion to produce EG in 95% yield.     

乙二醇甲醚中电解锡电解液直接水解制备纳米SnO2

采用锡金属为阳极，在无隔膜电解槽中，电化学溶解锡于乙二醇甲醚中制备得到纳米SnO2前驱体Sn(OCH2CH2OCH3)4，将电解液直接水解经溶胶-凝胶法制备纳米SnO2，前驱体通过拉曼和红外光谱进行表征.纳米SnO2采用X射线粉末衍射(XRD)和透射电子显微镜(TEM)进行表征.实验表明,电解合成的Sn(OCH2CH2OCH3)4能够溶解于乙醇中, 适宜作为溶胶-凝胶(sol-gel)法制备纳米SnO2的原料，制得的纳米SnO2经600 ℃煅烧后呈球形单分散结构，晶型为四方锡石型, 比表面为62.58 m2·g－1，平均粒径在(10.0±0.4) nm左右.产率为89.3％，电流效率为86.9％.     

Synthesis,characterization, and thermal properties of new flavor compounds

Synthesis, characterization, and thermal properties of new, flavor, long chain esters were presented. The new compounds were obtained in the catalytic esterification process of a stoichiometric ratio of trans-3,7-dimethyl-2,6-octadien-1-ol, succinic anhydride, and aliphatic chain diol. As diols ethylene glycol, 1,4-buthylene glycol, 1,5-pentylene glycol, and 1,6-hexylene glycol were applied. The spectroscopic analyses completely confirmed that the applied synthesis conditions allowed obtaining the new compounds with high yield and purity. Their thermal properties were studied in inert and oxidative atmospheres. The esters were less thermally stable in inert (IDT 186–195 °C) than in oxidative (IDT 210–228 °C) atmosphere. Two, non-completely divided decomposition steps were visible during their pyrolysis. In contrast, the new, long chain compounds decompose in three major steps in air. The analyses of the volatile products emitted during their pyrolysis indicated on the asymmetrical disrupt of their bonds. The formation of acyclic and alicyclic monoterpene hydrocarbons, succinic anhydride, diols, alcohols, alkenes, and water was observed. It indicated mainly on the β-elimination reactions during their pyrolysis. Also, β-elimination reactions of esters are mainly expected in air. Initially, it resulted in the formation of acyclic and alicyclic monoterpene hydrocarbons, hydroxyl compounds (diols, alcohols), and its β-elimination products: aldehydes, alkenes, and water. However, the presence of oxygen in the medium causes the partial decarboxylation and oxygenation of aldehydes and thus the formation of alkenes and carbon dioxide. In addition, the beginning of evaporation of succinic anhydride was detected at T _max1. At T _max2 the evaporation of succinic anhydride, their partial decarboxylation to CO₂, the small amounts of diols, alcohols, and aldehyde fragments were indicated. Finally, succinic anhydride, water, and carbon dioxide were only observed during decomposition of studied esters in air.     

Synthesis and Thermal Properties of Biodegradable Poly(ester‐urethane)s Based on Chemo‐Synthetic Poly[(R,S)‐3‐hydroxybutyrate]

A series of telechelic oligo[(R,S)‐3‐hydroxybutyrate]‐diols (PHB‐diols) was synthesized from ethyl (R,S)‐3‐hydroxybutyrate (ethyl (HB)) and four different aliphatic diols, namely, 1,4‐butanediol, 1,6‐hexanediol, 1,8‐octanediol and 1,10‐decanediol by transesterification and condensation in bulk. The structures of the synthesized oligomers were confirmed by ¹H NMR spectroscopy and MALDI‐TOF mass spectroscopy. The use of 1,4‐butanediol results in an oligoester with hydroxyl functionality of approximately 2. In the case of the higher aliphatic diols, the number average functionalities were found to be lower than 2. These differences were ascribed to side reactions which occur during polymerization, yielding unreactive end groups. Other novel families of biodegradable poly(ester‐urethane)s were synthesized either from PHB‐diol alone, or PHB‐diol mixed with poly(ε‐caprolactone)‐diol (PCL‐diol), poly(butylene adipate)‐diol (PBA‐diol) or poly(diethylene glycol adipate)‐diol (PDEGA‐diol). In each case, 1,6‐hexamethylene diisocyanate was used as a nontoxic connecting agent. The homopolymers prepared from PCL‐diol, PBA‐diol and PDEGA‐diol were also synthesized for the sake of comparison. All the prepared copolymers possess high molecular weight with glass transition temperature (T_g) values varying from –54 to –23°C. Some of the prepared copoly(ester‐urethane)s are partially crystalline with melting temperatures (T_m's) varying from 37 to 56°C.     

Synthesis of nanocrystalline γ-Al_2O_3 by sol-gel and precipitation methods for methanol dehydration to dimethyl ether

The capability of sol-gel and conventional precipitation techniques for the synthesis of nanocrystalline γ-alumina was investigated. These catalysts were used for vapor-phase dehydration of methanol to dimethyl ether in a fixed-bed reactor under the same operating conditions (T = 300 ?C, P = 1 bar, LHSV = 2.8, 11.7, 26.1 h?1) and characterized by means of N2 adsorption-desorption, NH3-TPD, XRD, TGA and SEM techniques. According to the experimental results, the catalysts prepared using sol-gel method in non-aqueous medium showed better performance compared with those prepared by other methods.     

New method of dimethyl sulfide synthesis

The synthesis of dimethyl sulfide consists in the reaction of dimethyl disulfide with methanol in the presence of solid catalyst, aluminum γ-oxide. The yield of dimethyl sulfide grows with growing temperature, contact time, and content of methanol in the reaction mixture. At 350–400°C, molar ratio methanol-dimethyldisulfide 2.0–2.5, and total conversion of the reagents the yield of dimethyl sulfide reached 95 mol%.     

Selective monotetrahydropyranylation of symmetrical diols using P_20_5/Si0_2 under solvent-free conditions and their depyranylation

Selective protection of one of the hydroxyl group in 1,n-symmetrical diols is achieved by P_2O_2/SiO_2-catalyzed reaction of the diol with dihydropyran under solvent-free conditions at room temperature.This selective protection is simple and it occurred under economically cheap conditions in high yield.The deprotected diol is simply obtained by refluxing of this compound in methanol using the same catalyst without any byproduct formation or additional purifications.