Silica Gel- and MCM-41-Supported MoS2 Catalysts for HDS Reactions

MCM-41- and silica gel-supported MoS₂ catalysts were prepared. MCM-41 was synthesized and impregnated with precursor, then activated to obtain the active phase. The sol–gel method was used for providing the SiO₂ support as well as for including the catalyst precursors in one single step of preparation. Such catalysts have applications particularly in hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) processes. A comparison of the activities of the catalysts was made. The catalytic activity results showed the method of preparation used in this study was successful in producing very efficient catalysts for the HDS of dibenzothiophene (DBT).A higher selectivity for direct C–S bond cleavage was observed for the MoS₂ catalyst supported on SiO₂ by the sol–gel method. X-ray diffraction studies showed that the catalysts were poorly crystallized with a very weak intensity of the (002) line of 2H-MoS₂.     

Polymeric sol–gel coatings as protective layers of aluminium alloys

Sol–gel route is an emerging technology to synthesize coatings of a wide variety of properties taylored. In this work three low temperature cured coatings has been studied to evaluate their protective properties in order to be used as protective barrier coatings for aluminium alloys with potential architectural and automotive applications. These three coatings are novel modified silane nanocomposites coatings obtained mixing two sols separately prepared: a pre-hydrolysed 3-glycidyloxypropyl trimethoxysilane (GPTS) with acidic catalyst and another obtained from tetraethylorthosilicate/methyltriethoxysilane (TEOS/MTES). Particulated coatings were obtained by addition of 25 wt.% particles of Aerosil 300 and Aerosil R972, respectively. The protective properties of the coatings were evaluated by electrochemical impedance spectroscopy (EIS) which showed notably differences among them not only from the protective viewpoint but the hydrophobic nature of the coatings and the controlling corrosion mechanism in each case.     

二甲醚燃烧用掺杂钡、镍六铝酸盐催化剂的研究

二甲醚是易液化，便于运输，清洁化的新能源。当作为燃料使用时，采用催化燃烧的方法能使得燃烧的起燃温度降低和提高燃烧转化率，克服了普通燃烧的缺点，实现了清洁燃烧。对二甲醚催化燃烧用的催化剂BaNiAl11O19-δ进行了制备与研究。采用溶胶-凝胶法制备六铝酸盐催化剂BaNiAl11O19-δ,考察其对新能源二甲醚催化燃烧反应的活性，并用TG—DTA对催化剂的性质进行考察。结果表明，加入经800℃焙烧4h后又在1200℃焙烧了2h的催化剂，比未加催化剂的燃烧体系T10降低了50℃。用溶胶一凝胶法制备的六铝酸盐催化剂BaNiAl11O19-δ对二甲醚催化燃烧反应具有较高的催化活性。     

Biocidal hydantoinylsiloxane polymers. IV. N‐halamine siloxane‐functionalized silica gel

The monomer 5,5‐dimethyl‐3‐(3′‐triethoxysilylpropyl)hydantoin and its hydrolysis product polymer poly[3‐(5,5‐dimethylhydantoinylpropyl)hydroxysiloxane] were employed to functionalize the surfaces of silica gel particles in order to produce an adhered film that becomes biocidal upon chlorination with dilute sodium hypochlorite bleach. The biocidal efficacy of the functionalized silica gel was demonstrated in a cartridge filter experiment against the bacterial pathogens Staphylococcus aureus and Escherichia coli O157:H7. Complete 6 log inactivations of the two bacterial species were observed within 30 s of contact. Moreover, upon loss of biocidal activity due to depletion of bound chlorine, the coated silica gel particles could be recharged by further exposure to dilute bleach. Potential uses of the biocidal silica gel include disinfection and odor control in water treatment facilities and recirculating baths. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3448–3454, 2006     

Electrochemical performance of nanocrystalline Li3V2(PO4)3/carbon composite material synthesized by a novel sol–gel method

A novel sol–gel method based on V₂O₅·nH₂O hydro-gel was developed to synthesize nanocrystalline Li₃V₂(PO₄)₃/carbon composite material. In this route, V₂O₅·nH₂O hydro-gel, NH₄H₂PO₄, Li₂CO₃ and high-surface-area carbon were used as starting materials to prepare precursor, and the Li₃V₂(PO₄)₃/carbon was obtained by sintering precursor at 750 °C for 4 h in flowing argon. The sol–gel synthesis ensures homogeneity of the precursors and improved reactivity. The sample was characterized by XRD, SEM and TEM. X-ray diffraction results show Li₃V₂(PO₄)₃ sample is monoclinic structure with the space group of P2₁/n. The TEM image indicates that the Li₃V₂(PO₄)₃ particles modified by conductive carbon are about 70 nm in diameter. The Li₃V₂(PO₄)₃/carbon system showed that the discharge capacities in the first and 50th cycle are about 155.3 and 143.6 mAh/g, respectively, in the range of 3.0–4.8 V. The sol–gel method is fit for the preparation of Li₃V₂(PO₄)₃/carbon composite material which may offer some favorable properties for commercial application.     

凉水塔混凝土结构的腐蚀与防护

分析了大化肥凉水塔钢筋混凝土结构受体不水及大气的腐蚀渗透原因，提出了防护方法。     

Large deformation and ultimate properties of biopolymer gels: 2. Mixed gel systems

Biphasic, mixed gels of agarose and gelatin were prepared, and their mechanical behaviour in tensile tests was determined, up to failure, utilising four decades of (constant) strain rate. The behaviour of pure agarose and pure gelatin in such tests has been determined previously. Suitable ‘blending-laws’ relating the small deformation shear modulus of the composite to the moduli of the component phases have also been discussed elsewhere. This report extends the latter treatment to the more aggressive large deformation regime, deriving bounds for modulus and break stress which closely model observed behaviour.     

Influence of operation parameters on the separation of mixtures by pervaporation and vapor permeation with inorganic membranes. Part 1: Dehydration of solvents

The separation performance of two different commercially available tubular inorganic membranes was studied for solvent dehydration. The separation layers consisted of A-type zeolite and microporous silica. The membrane characteristics were determined as function of operating conditions such as feed composition, temperature, and permeate pressure in pervaporation and vapor permeation. Among different membranes of the same batch, flux and selectivity were reproducible within 10%. The partial flux of water as the preferentially permeating component increases linearly with the water vapor pressure difference between feed and permeate and depends only marginally (viscosity influence) upon the properties of the organic component. The flux of the organic (retained) component is low and can best be described by assuming a substance and membrane specific permeance (flux over partial pressure difference) that is independent of composition. At very low water concentration in the feed one would expect a strong increase in permeability of the retained component through non-zeolite pores and larger silica pores as predicted by pure component measurements. However, this effect was not observed in mixtures within the concentration range studied here. A temperature rise improves flux rates exponentially while selectivity remains high. Thus, higher module cost in comparison to polymeric membranes can be compensated by reduced membrane area if a higher operating temperature can be chosen. Flux and selectivity decline as a function of permeate pressure with decreasing driving force. In vapor permeation with inorganic membranes superheating of the vaporous feed improves their performance while for polymeric materials a steep flux decline is observed. High flux and selectivity are obtained in the separation of water from alcohols. The normalized flux values of the A-type zeolite membrane are roughly 10 kg/m² h bar with a mixture selectivity of 2000 for methanol, 4000 for ethanol and 8000 for n-butanol. The average permeance of the amorphous silica membrane lies above 12 kg/m² h bar with mixture selectivity of 50 for methanol, 500 for ethanol and 2000 for n-butanol. The separation mechanism is mainly based on adsorption and diffusion enhanced by shape selectivity and size exclusion in some cases. The transport characteristics could be described with a simple transport model based on normalized permeate fluxes. With regard to the operation stability of the membranes, no deterioration of the performance was observed for the A-type zeolite in solvent dehydration or in separation of water from reaction mixtures. The silica membrane showed an initial conditioning effect involving a rearrangement of Si-OH groups with an increase in selectivity and decrease in flux of about 30%. After a few hours the performance stabilized and remained constant during further operation.     

CO2‐facilitated transport through poly(N‐vinyl‐γ‐sodium aminobutyrate‐co‐sodium acrylate)/polysulfone composite membranes

Poly(N‐vinyl‐γ‐sodium aminobutyrate‐co‐sodium acrylate) (VSA–SA)/polysulfone (PS) composite membranes were prepared for the separation of CO₂. VSA–SA contained secondary amines and carboxylate ions that could act as carriers for CO₂. At 20°C and 1.06 atm of feed pressure, a VSA–SA/PS composite membrane displayed a pure CO₂ permeation rate of 6.12 × 10^?6 cm³(STP)/cm² s cmHg and a CO₂/CH₄ ideal selectivity of 524.5. In experiments with a mixed gas of 50 vol % CO₂ and 50 vol % CH₄, at 20°C and 1.04 atm of feed pressure, the CO₂ permeation rate was 9.2 × 10^?6 cm³ (STP)/cm² s cmHg, and the selectivity of CO₂/CH₄ was 46.8. Crosslinkages with metal ions were effective for increasing the selectivity. Both the selectivity of CO₂ over CH₄ and the CO₂ permeation rate had a maximum against the carrier concentration. The high CO₂ permeation rate originated from the facilitated transport mechanism, which was confirmed by Fourier transform infrared with attenuated total reflectance techniques. The performance of the membranes prepared in this work had good stability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 275–282, 2006     

以硅胶为载体的茂金属催化剂研究进展

综述了近年来硅胶载体经甲基铝氧烷(MAO)化学处理后负载茂金属催化剂的一些研究进展，指出硅胶的化学活化是茂金属催化剂负载化的关键，单组分化学处理剂处理硅胶载体不能完全满足人们对负载型茂金属催化剂烯烃聚合的需求，采用含MAO的多组分化学处理剂化学活化硅胶后负载催化剂是该领域发展的趋势。