Studies of synergism for lowering dynamic interfacial tension in sodium alpha-(n-alkyl) naphthalene sulfonate/alkali/acidic oil systems

Alkylnaphthalene sulfonates with high purity were selected as model components to research synergism for lowering interfacial tension (IFT) in surfactant/alkali/acidic oil systems. The dynamic IFTs between alkylnaphthalene sulfonates with different alkyl chain length and n-decane, oleic acid model oil, or Shengli crude oil were measured. The results showed that the alkylnaphthalene sulfonates with different alkyl chain lengths had different synergism with different acidic components and their ionized acids under the same conditions. The synergism for lowering dynamic IFT in alkylnaphthalene sulfonate/alkali/acidic oil systems was controlled by alkylnaphthalene sulfonate concentration, alkyl chain length, alkali concentration, alkali type, and oleic acid concentration: optimal physicochemical conditions were necessary to the best synergism. This indicates that the synergism among added surfactant acidic components in crude oil and their ionized acids is controlled by the ratio of their interfacial concentrations.     

Synthesis of nanoporous graphite-derived carbon-silica composites by a mechanochemical intercalation approach

A mechanochemical intercalation approach which applies a simple mechanical milling to induce intercalation reaction was applied to introduce controlled amount of tetraethoxylsilane (TEOS) into surfactant-preexpanded graphite oxide, and the relationships between the intercalation structure, the porosities of the calcined products, and the Si addition were examined. It was found that a small added amount of TEOS produced a more expanded ordered layer structure with the interlayer distance and silicon content increasing with the amount of TEOS added, although a large amount of added TEOS easily induces layer delamination, resulting in a less ordered structure. The silica structure in the composite is changed from a disordered structure having enhanced bond strain to a condensed silica network when the amount of TEOS added increases. The porosities of the final calcined samples increase with the increase of silicon content but then decrease slightly after reaching a maximum where silicon content starts to become constant, indicating that both silicon content and the composition state of silica particles and carbon layers play important roles in porosity formation.     

Purification,Characterization and Mechanistic Study of β-Glucosidase from Flavobacterium meningosepticum (ATCC 13253)

A β-glucosidase (EC 3.2.1.21) from Flavobacterium meningosepticum has been purified and characterized. Purity was enhanced at least 530-fold from crude cell extract with 16.6% yield. The estimated molecular mass of the purified enzyme is 150 kDa by gel filtration and 78 kDa by SDS-PAGE. This dimeric enzyme has a pI = 9.0 and an optimal activity at pH 5.0 and temperature of 50 °C. Divalent metal ions (Hg²⁺, Cu²⁺, Ca²⁺, Mg²⁺) and EDTA have negligible effect on the enzyme activity. The enzyme exhibited a high specificity on the glycon portion of aryl-β-D -glycosides. NMR spectroscopy revealed the enzyme catalyzed hydrolysis of p-nitrophenyl-β-D -glucopyranoside with the retention of anomeric configuration, indicating that a double displacement mechanism was involved. A preliminary study of the Bronsted relationship showed a concave-downward plot, which is consistent with the two-step mechanism.     

金属载体催化剂的涂层研究

在高温氧化处理不同时间的金属载体箔片上涂覆MgAl2O4/Al2O3过渡涂层,利用TG-DSC,XRD,SEM,BET和超声振动等分析测试技术,对载体和涂层的微观结构与表面特性进行研究.结果表明,在950 ℃下高温氧化5 h,箔片表面生成板状Al2O3晶须,有利于增强涂层与箔片的附着力.在载体表面涂覆一层MgAl2O4/Al2O3过渡涂层,有助于提高活性组分与金属载体的结合力,可以获得高结合强度的涂层结构,促使活性元素高度分散.     

Study of SPG membrane emulsification processes for the preparation of monodisperse core-shell microcapsules

Experimental investigations on the Shirasu-porous-glass (SPG)-membrane emulsification processes for preparing monodisperse core-shell microcapsules with porous membranes were carried out systematically. The results showed that, to get monodisperse oil-in-water (O/W) emulsions by SPG membrane emulsification, it was more important to choose an anionic surfactant than to consider hydrophile-lipophile balance (HLB) matching. Increasing the viscosity of either the disperse phase or the continuous phase or decreasing the solubility of the disperse phase in the continuous phase could improve both the monodispersity and the stability of emulsions. With increasing monomer concentration inside the disperse phase, the monodispersity of emulsions became slightly worse and the mean diameter of emulsions gradually became smaller. Monodisperse monomer-containing emulsions were obtained when the SPG membrane pore size was larger than 1.0 micro m, and from these emulsions satisfactory monodisperse core-shell microcapsules with a porous membrane were prepared. On the other hand, when the SPG membrane pore size was smaller than 1.0 mciro m, no monodisperse emulsions were obtained because of the formation and chokage of solid monomer crystals in the pores or at the end of the pores of the SPG membrane. This was due to the remarkable solvation and diffusion of the solvent in water. With increasing the emulsification time the average emulsion diameter generally decreased, and the monodispersity of the emulsions gradually became worse.     

锆助剂对低温液相合成甲醇用铜铬硅催化剂性能的影响

考察了含锆的铜铬硅催化剂低温液相合成甲醇性能，并进行了BET、TPR-H2、TPD-H2、TPD-CO、XRD和XPS表征。结果表明，锆作为结构助剂及电子助剂对催化剂在低温液相合成甲醇反应中具有显著的促进作用，反应活性可提高32.25 ％。锆助剂能有效提高催化剂的比表面积，促进催化剂中铜铬组分的分散及表面富集。ZrO2加入在催化剂表面产生的Cu+与催化活性的改善密切相关，Zr4+、Cr3+、Cu+可形成复合中心，为价态的稳定性提供微环境，在H2活化及C O键的断裂等反应步骤中起重要作用。     

纳米碳管电极上氧的电催化还原

以聚四氟乙烯为粘结剂制成了多壁纳米碳管（MWNT）电极.采用恒电位阶跃法和循环伏安法研究了MWNT电极在碱性溶液中的电化学行为，并对碱性溶液中溶解氧在该电极上的电化学还原行为进行了研究.实验结果表明： MWNT电极具有比石墨电极更高的孔隙率和电化学表面积；MWNT电极上O2还原成的反应为准可逆过程；在5～50 mV•s－1的扫描速率范围内，阴极峰电流与扫描速度成线性关系，表明MWNT电极上O2还原成的反应受吸附控制；对碱性溶液中的氧还原反应， MWNT比石墨具有更高的催化活性.     

A new type of noncovalent surface–π stacking interaction occurring on peroxide-modified titania nanosheets driven by vertical π-state polarization

Noncovalent π stacking of aromatic molecules is a universal form of noncovalent interactions normally occurring on planar structures (such as aromatic molecules and graphene) based on sp²-hybridized atoms. Here we reveal a new type of noncovalent surface–π stacking unusually occurring between aromatic groups and peroxide-modified titania (PMT) nanosheets, which can drive versatile aromatic adsorptions. We experimentally explore the underlying electronic-level origin by probing the perturbed changes of unoccupied Ti 3d states with near-edge X-ray absorption fine structures (NEXAFS), and find that aromatic groups can vertically attract π electrons in the surface peroxo-Ti states and increase their delocalization regions. Our discovery updates the concept of noncovalent π-stacking interactions by extending the substrates from carbon-based structures to a transition metal oxide, and presents an approach to exploit the surface chemistry of nanomaterials based on noncovalent interactions.

A new type of noncovalent surface–π stacking interaction occurring on a transition metal oxide, titania, is reported, which is different from the traditional forms on sp²-hybridized planar structures like graphene.     

Transition metal coordination polymers with polycarboxylic acid as bridging ligands: Synthesis and structure characterization of [Fe(μ4-bta)0.5(phen)(OH)]<Subscript>n</Subscript>

A new 2D (two-dimensional) coordination polymer, [Fe(μ4-bta)o.5(phen)(OH)]_n (1), has been hydrothermally synthesized with FeCl₃ 6H₂, Na₄bta (h₄bta = 1,2,4,5-benzentetracarboxylic acid), 1,10-phen (1,10-phenanthroline) and H₂O as raw materials. The crystals of the compound belong to monoclinic P2₁/n space group, a = 1.0129(2) nm, b = 0.9265(2) nm, c = 1.5696(3) nm, β=91.37(3)°V=1.4721(5) nm³,Z=3, final R₁=0.0292, wR ₂=0.0798 for 2572 [/>2σ(/)] observed reflections. The result of structure determination shows that in the compound each bta ligand is connected with four Fe³, forming a new μ4-coordination mode. Four deprotonated carboxylic groups of bta link to Fe³ ions alternatively through monodentate and bidentate coordination fashion, constructing 2D layer network. The measurement of variable temperature magnetic susceptibility indicates that there exist antiferromagnetic interactions between Fe³ ions in the compound. The TGA spectrum displays relatively fine thermal stability of the compound. In addition, IR and UV-Vis spectra of compound 1 have also been measured.