醇硫化聚醚型聚氨酯水声透声橡胶

本文介绍了聚醚型醇硫化聚氨酯水声透声橡胶的硫化剂、催化剂变量试验对力学性能的影响。并探讨了醇硫化聚氨酯水声透声橡胶硫化机理。通过实验与初步使用,显示出它有良好的声学性能,尤其是高频透声性能好。同时具有硫化温度低,硫化速度快,周期短,毒性小等优点。

端烷氧基聚甲基三氟丙基硅氧烷的合成表征和室温交联特性

以α,ω-端羟基聚甲基三氟丙基硅氧烷为初始聚合物,通过与含氢硅氧烷脱氢缩合合成了相对分子质量、官能度和官能团各异的6种氟硅聚合物(M1~M4,M5和E1)。通过傅里叶变换红外光谱和核磁共振波谱对封端聚合物进行了表征,并通过流变学手段研究了聚合物在室温交联硫化过程中黏度(η)和模量(G′和G″)的变化,为交联反应速率提供依据。结果表明,封端聚合物在不外加交联剂时亦能发生自交联。当采用同一交联剂M1时,与初始聚合物H4相比,封端后的聚合物M4具有较快的黏度上升趋势和交联反应速率,溶胶-凝胶转变点的时间由2 h以上缩短为22.5 min,原因在于烷氧基封端降低了三氟丙基侧基对活性端基的屏蔽作用,因而反应性大为提高。以M2~M4为基础聚合物制得的氟硅密封胶,具有较好的交联密度、力学性能和耐高低温性能。

Sulfated Sterols Isolated from Starfish Asterias amurensis Lutken

Aim To study the chemical constituents of starfish Asterias amurensis. Methods The constituents were separated and purified by different chromatographic methods, and their structures were elucidated by MS and NMR. Results Six compounds were isolated from Asterias amurensis Lutken. Their structures were identified as 3β-O-sulfated-cholest-5-en sodium salt （1）, 3β-O-sulfated-6α-ol- pregn-9（ 11 ） -en-20-one sodium salt （ 2 ）, 3β-O-sulfated-6α-ol-cholest-9 （ 11 ） -en-23-one sodium salt （3）, 3β-O-sulfated-6α, 20β-diol-cholest-9 （ 11 ）-en-23-one sodium salt （ 4 ）, 3β-O-sulfated-6α-ol- cholesta-9 （ 11 ）, 20 （ 22 ） -dien-23-one sodium salt （ 5 ）, and 3β-O-sulfated-6ct-ol-ergost-9 （ 11 ） -en-23- one sodium salt （6）. Conclusion Compounds 1 - 6 were obtained from this species for the first time.

Tungsten carbide-reduced graphene oxide intercalation compound as co-catalyst for methanol oxidation

Highly dispersed tungsten carbide（WC） nanoparticles（NPs） sandwiched between few-layer reduced graphene oxide（RGO） have been successfully synthesized by using thiourea as an anchoring and inducing reagent.The metatungstate ion,[H2W（12）O（40）]^6-,is assembled on thiourea-modified graphene oxide（GO） by an impregnation method.The WC NPs,with a mean diameter of 1.5 nm,are obtained through a process whereby ammonium metatungstate first turns to WS2,which then forms an intercalation compound with RGO before growing,in situ,to WC NPs.The Pt/WC-RGO electrocatalysts are fabricated by a microwave-assisted method.The intimate contacts between Pt,WC,and RGO are confirmed by X-ray diffraction,scanning electron microscope,transmission electron microscope,and Raman spectroscopy.For methanol oxidation,the Pt/WC-RGO electrocatalyst exhibited an electrochemical surface area value of 246.1 m^2/g Pt and a peak current density of1364.7 mA/mg Pt,which are,respectively,3.66 and 4.77 times greater than those of commercial Pt/C electrocatalyst（67.2 m^2/g Pt,286.0 mA/mg Pt）.The excellent CO-poisoning resistance and long-term stability of the electrocatalyst are also evidenced by CO stripping,chronoamperometry,and accelerated durability testing.Because Pt/WC-RGO has higher catalytic activity compared with that of commercial Pt/C,as a result of its intercalated structure and synergistic effect,less Pt will be required for the same performance,which in turn will reduce the cost of the fuel cell.The present method is facile,efficient,and scalable for mass production of the nanomaterials.

Adsorptive Desulfurization of Propylmercaptan and Dimethyl Sulfide by CuBr_2 Modified Bentonite

Adsorptive desulfurization for removing propylmercaptan （PM） and dimethyl sulfide （DMS） over CuBr2 modi- fied bentonite was investigated under ambient conditions in this work. A saturated sulfur capacity as high as 196 mg of S per gram of adsorbent was demonstrated. The influence of loading amount of Cu （II） and calcination temperature on adsorptive desulfurization was investigated. Test results revealed that the optimum loading amount of Cu （II） was 15%, and the calcination temperature was 150 ℃. The pyridine-FTIR spectroscopy showed that a certain amount of Lewis acid could contribute to the increase of adsorption capacity. Spectral shifts of the v（C-S） and v（Cu-S） vibrations were detected from the Raman spectra of the Cu （II） complex which was a reaction product of CuBr2 with DMS. According to the hybrid orbital theory and the complex adsorption reaction, the desulfurization of PM and DMS over the CuBr2 modified bentonite is ascribed to the formation of S-M （σ） bonds.

Oxidation of Mercaptans from Light Oil Sweetening by Fe_2O_3/MgO/Al_2O_3 Supported CoPcS Catalyst

MgO/Al2O3 and Fe2O3/MgO/Al2O3 solid bases were prepared through mixing method. After sulfonated cobalt phthalocyanine （CoPcS） being supported on these solid bases, the catalytic performance of these catalysts was evaluated by means of mercaptan oxidation reaction. The samples were characterized by X-ray diffraction （XRD）, CO2 temperature-programmed desorption （CO2-TPD）, FTIR spectroscopy, and X-ray photoelectron spectroscopy （XPS）. Investigation was focused on the effect of Fe2O3 on activity, crystal structure, basicity, and stability of the catalyst and also on the role of Fe2O3 in the mercaptan oxidation processes. Test results have shown that the Fe2O3/MgO/Al2O3- CoPcS catalyst has a higher initial activity and a much longer service life than the MgO/Al2O3-CoPcS catalyst. The increased types of basic sites coupled with an enhanced oxidation ability resulted from the addition of Fe2O3 have contributed to the improvement of the catalytic activity of the MgO/Al2O3-CoPcS catalyst.

Thiol-free route to diaryl sulfides by Cu catalyzed coupling of sodium thiosulfate with aryl halides

A method for the synthesis of diaryl sulfides from aryl halides in polyethylene glycol was reported.Inodorous Na2S2O3·5H2O,which is readily available as a stable salt,is an effective source of sulfur in the presence of Cu I as catalyst.

Kinetics of Glucose Ethanolysis Catalyzed by Extremely Low Sulfuric Acid in Ethanol Medium

The kinetics for production of ethyl levulinate from glucose in ethanol medium was investigated. The experiments were performed in various temperatures （433-473 K） and initial glucose concentrations （0.056-0.168 mol·L-1） with extremely low sulfuric acid as the catalyst. The results show that higher temperature can improve the conversion of glucose to ethyl levulinate, with higher yield of ethyl levulinate （44.79%, by mole） obtained at 473 K for 210 min. The kinetics follows a simplified first-order kinetic model. For the main and side reactions, the values of activation energy are 122.64 and 70.97 kJ·mo1-1, and the reaction orders are 0.985 and 0.998, respectively.

A Mechanism Study of a Novel Acid-Activatable Michael-Type Fluorescent Probe for Thiols

A Michael addition is usually taken as a base-catalysed reaction. However, our synthesized 2-（quinolin-2-ylmethylene） malonic acid （QMA） as a Michael-type thiol fluorescent probe is acid-active in its sensing reaction. In this work, based on theoretic calculation and experimental study on 7-hydroxy-2-（quinolin-2-ylmethylene） malonic acid, we demonstrated that QMA as a Michael acceptor is acid-activatable, i.e., it works only in solutions at pH〈7, and the lower the pH of solutions is, the higher reactivity QMA has. In alkaline solution, the malonate QMA[-2H＋]2- cannot react with both RSand RSH. In contrast, 2-（quinolin-2- ylmethylene） malonic ester （QME）, the ester of QMA, reveal a contrary pH effect on its sensing reaction, that is, it can sense thiols in alkaline solutions but not in acidic solutions, like a normal base-catalysed Michael addition. The values of activation enthalpies from theoretic calculation support the above sensing behavior of two probes under different pH conditions. In acidic solutions, the protonated QMA is more highly reactive towards electrophilic attack over its other ionized states in neutral and alkaline solutions, and so can react with lowly reactive RSH. In contrast, there is a big energy barrier in the interaction of QME with RSH （acidic solutions）, and the reaction of QME with the highly reactive nucleophile RS- is a low activation energy process （in alkaline solutions）. Theoretic calculation reveals that the sensing reaction of QMA undergoes a 1,4-addition process with neutral thiols （RSH）, and a 1,2-addition pathway for the sensing reaction of QME with RS-. Therefore, the sensing reaction of QMA is an acid-catalysed Michael addition via a 1,4-addition, and a normal base-catalysed Michael addition via a 1,2-addition.

Electron Momentum Spectroscopy of Ethanethiol Complete Valence Shell

The binding energy spectra and electron momentum distributions for the complete valence orbitals of ethanethiol were measured for the first time by binary （e, 2e） electron momentum spectroscopy employing non-coplanar symmetric kinematics at an impact energy of 1200 eV plus binding energy. The experimental results are generally consistent with the theoretical calculations using density functional theory and Hartree-Fock methods with various basis sets. A possible satellite line at 17.8 eV in binding energy spectrum was observed and studied by electron momentum spectroscopy.

Ab Initio Investigation of Methanthiol and Dimethyl Sulfide Adsorption on Zeolite

The Hartree-Fock and cluster model methods have been employed to investigate interactions of methanthiol or dimethyl sulfide on zeolites. Molecular complexes formed by adsorption of methanthiol on silanol H3SiOSi（OH）2OSiH3 with five coordination forms and dimethyl sulfide on silanol H3SiOSi（OH）2OSiH3 with four coordination forms, and Bronsted acid sites of bridging hydroxyl H3Si（OH）Al（OH）2OSiH3 entering into interactions with methanthiol or dimethyl sulfide have been investigated. Full optimization and frequency analysis of all cluster models have been carded out using the Hartree-Fock method at 6-31＋G＊＊ basis set level for hydrogen, silicon, aluminum, oxygen, carbon, and sulfur atoms. The structures and energy changes of different coordination forms derived from methanthiol and H3Si（OH）Al（OH）2OSiH3, dimethyl sulfide and H3Si（OH）Al（OH）2OSiH3, methanthiol and H3SiOSi（OH）2OSiH3, dimethyl sulfide and H3SiOSi（OH）2OSiH3 complexes have been comparatively studied. The calculated results showed that the nature of interactions leading to the formation of the bridging hydroxyl-methanthiol, silanol-methanthiol, bridging hydroxyl-dimethyl sulfide, silanol-dimethyl sulfide complexes was governed by the Van der Waals force as confirmed by a small change in geometric structures and properties. Methanthiol and dimethyl sulfide molecules were adsorbed on bridging hydroxyl group prior to silanol group as evidenced by the heat of adsorption, and the protonization of methanthiol adsorption on bridging hydroxyl model, which was supposed in the literature, was not found.

Ternary System of Fe-based Ionic Liquid,Ethanol and Water for Wet Flue Gas Desulfurization

Fe-based ionic liquid （Fe-IL） was synthesized by mixing FeCl3·6H2O and 1-butyl-3-methylimidazolium chloride [Bmim]C1 in this paper. The phase diagram of a ternary Fe-IL, ethanol and water system was investigated to construct a ternary desulfurization solution for wet flue gas desulfurization. The effects of flow rate and concentration of SO2, reaction temperature, pH and Fe-IL fraction in aqueous desulfurization solution on the desulfiariza- tion efficiency were investigated. The results shows that the best composition of ternary desulfurization solution of Fe-IL, ethanol and water is 1 ： 1.5 ： 3 by volume ratio, and pH should be controlled at 2.0. Under such conditions, a desulfurization rate greater than 90% could be obtained. The product of sulfuric acid had inhibition effect on the wet desulfurization process. With applying this new ternary desulfurization solution, not only the catalyst Fe-IL can be recycled and reused, but also the product sulfuric acid can be separated directly from the ternary desulfurization system.

Removal of mercaptans from light oils using ionic liquid–NaOH aqueous solution as extractants

The application of ionic liquids as alternatives to conventional organic solvents in the extraction process has been investigated. In the present study, fourteen species of imidazolium-based ionic liquids were added into the NaOH （aq） to remove the mercaptans. The influences of anion species and cation alkyl chain length of the imidazolium-based ionic liquids on the performance of mercaptan removal from light oils have been discussed. The efficiency of extraction for mercaptans exhibited the order of [Ac]- 〉 [OH]- [Br]- 〉 [BF4]-. The longer alkyl chain imidazolium-based ionic liquids contributed to enhance desulfurization rate of l-butyl mercaptan. 100% desulfurization rate of l-butyl mercaptan was achieved by the anion of Ac- ionic liquids and NaOH （aq） at a volume ratio of 40：1 （V（oil]：Vfionic liouid）） and a short eouilibrium time within 10 min.

Optimization of dilute acid hydrolysis of Enteromorpha

Acid hydrolysis is a simple and direct way to hydrolyze polysaccharides in biomass into fermentable sugars. To produce fermentable sugars effectively and economically for fuel ethanol, we have investigated the hydrolysis of Enteromorpha using acids that are typically used to hydrolyze biomass： H2SO4, HC1, H3PO4 and C4H404 （maleic acid）. 5%（w/w） Enteromorpha biomass was treated for different times （30, 60, and 90 min） and with different acid concentrations （0.6, 1.0, 1.4, 1.8, and 2.2%, w/w） at 121~C. H2SO4 was the most effective acid in this experiment. We then analyzed the hydrolysis process in H2SO4 in detail using high performance liquid chromatography. At a sulfuric acid concentration of 1.8% and treatment time of 60 min, the yield of ethanol fermentable sugars （glucose and xylose） was high, （230.5 mg/g dry biomass, comprising 175.2 mg/g glucose and 55.3 mg/g xylose）, with 48.6% of total reducing sugars being ethanol fermentable. Therefore, Enteromorpha could be a good candidate for production of fuel ethanol. In future work, the effects of temperature and biomass concentration on hydrolysis, and also the fermentation of the hydrolysates to ethanol fuel should be focused on.

丙烯酸-2,4,6-三硝基苯乙酯的合成及热分解

以TNT、甲醛为原料,在弱碱性条件下反应合成得到2,4,6-三硝基苯乙醇(PicCH2CH2OH);PicCH2CH2OH在浓硫酸催化下和丙烯酸在甲苯中回流反应24h,合成得到丙烯酸-2,4,6-三硝基苯乙酯,产率为62%。采用紫外可见光谱(UV-Vis)、核磁共振氢谱(1HNMR)、红外光谱(FTIR)、质谱(MS)以及元素分析等对产物结构进行了表征。利用热重分析(TG)对产物热稳定性进行了研究,采用Kissinger方法和Ozawa方法计算其热分解活化能Ea分别为99.78,102.96kJ·mol-1。

Chemical interactions between silver nanoparticles and thiols: a comparison of mercaptohexanol against cysteine

The interaction between citrate capped silver nanoparticles and two different thiols, mercaptohexanol （MH） and cysteine, was investigated. The thiols interacted with silver nanoparticles in a significantly contrasting manner. With MH, a sparingly soluble silver（1） thiolate complex AgSRm （Rm = -（CH2）6OH） was formed on the silver nanoparticle surface. Cyclic voltammograms and UV-vis spectra were used to infer that the AgSRm complex on the nanoparticle surface undergoes a phase transition to give a mixture of AgSRm and Ag2S-like complexes. In contrast, when silver nanoparticles were exposed to cysteine, the citrate cap- ping agent on the silver nanoparticles was replaced by cysteine to give cysteine capped nanoparticles. As cysteine capped nanoparticles form, the electrochemical data displayed a decrease in oxidative peak charge but the UV-vis spectra showed a constant signal. Therefore, cysteine capped nanoparticles were suggested to have either inactivated the silver surface or else pro- moted detachment from the electrode surface.