镍基气凝胶催化CH4-CO2重整制取合成气反应的研究 Ⅲ.影响催化剂积碳性能因素的探讨

考察了823K焙烧的干凝胶xNCA550、气凝胶aNCA550及浸渍型催化剂iNCA550在923K、1073K、1173K反应温度下的积碳行为，对催化剂表面碳的活性及类型进行了分析，并探讨了影响催化剂积碳的因素。实验结果表明，随反应温度的提高，催化剂的积碳能力减弱，尤以气凝胶催化剂aNCA550明显。催化剂的积碳主要发生在反应的初期，反应温度越高，到达积碳量相对稳定期所需要的时间越短；随着反应时间的延续，催化剂积碳量缓慢增长，并且表面碳的活性降低。催化剂的酸性和镍晶粒大小是影响其积碳性能的主要内在因素，而它们对积碳的影响程度受反应温度的影响，反应温度越高，催化剂表达酸性中心利于积碳的作用越小，小晶粒镍抑制催化剂积碳的能力越强。     

Photochemical deuterium exchange of the m-methyl group of 3-methylbenzophenone and 3-methylacetophenone in acidic D2O

Photolysis of the title compounds in acidic aqueous solution results in "activation" of the distal m-methyl group, resulting in deuterium exchange (Phi approximately 0.1) when D(2)O is used. The reaction is not observed in neutral aqueous solution or in deuterated organic solvents such as CD(3)CN. The reaction is best rationalized by a mechanism involving initial protonation at the carbonyl oxygen of the triplet excited state. [reaction: see text]     

Fourier transform infrared spectroscopy study of the effect of pH on anion and cation adsorption onto poly(acrylo‐amidino diethylenediamine)

The role of hydrogen bonding in the chemistry of transition‐metal complexes remains a topic of intense scientific and technological interest. Poly(acrylo‐amidino diethylenediamine) was synthesized to study the effects of hydrogen bonding on complexes at different pHs. The polymer was synthesized through the coupling of diethylene triamine with polyacrylonitrile fiber in the presence of AlCl₃ · 6H₂O addition. The adsorption capacity of this polymer was 11.4 mequiv/g. The ions used for the adsorption test were CrO, PO, Cu²⁺, Ni²⁺, Fe²⁺, and Ag⁺. All experiments were confirmed with Fourier transform infrared. In the study of anion adsorption, at low pHs, only ionic bonds existed, whereas at high pHs, no bonds existed. However, in the middle pH region, both ionic bonds and hydrogen bonds formed between poly(acrylo‐amidino diethylenediamine) and the chromate ion or phosphate ion. When poly(acrylo‐amidino diethylenediamine) and metal ions (Cu²⁺, Ni²⁺, Fe²⁺, and Ag⁺) formed complexes, a hydrogen‐bonding effect was not observed with Fourier transform infrared. The quantity of metal ions adsorbed onto poly(acrylo‐amidino diethylenediamine) followed the order Ag⁺ > Cu²⁺ > Fe²⁺ > Ni²⁺. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2010–2018, 2004     

Penicillin biosynthesis: Retention of configuration at c-3 of valine during its incorporation into the arnstein tripeptide

[3-³H]-valine was efficiently synthesised from sodium α-ketoisovalerate. With a β-lactam negative mutant of C. acremonium, l-[1-¹⁴C-3-³H]-valine and dl-[1-¹⁴C-3-³H]-valine were independently incorporated into the Arnstein tripeptide dimer, i.e. Bis-δ-(l-α-aminodipyl)-l-cystinyl-bis-d-valine, with full retention of trieium at C-3 of the d-valine residue. This result strongly suggested retention of configuration at C-3 of valine when the tripeptide was biosynthesised, and further limited the number of possible mechanisms for the biosynthesis of penicillins.     

CIDEP studies of the photolysis of the lignin model compound α-guaiacoxylacetoveratrone: the role of triplet reactions in aqueous and hydroxylic solvents

Free radical reactions induced by the photolysis of the lignin model compound α-guaiacoxylacetoveratrone have been studied by conventional and time-resolved ESR spectroscopy. In the presence of efficient hydrogen donors such as aqueous and hydroxylic solvents the primary reaction involves photoreduction of the triplet phenacyl ether to form the ketyl radical followed by rapid cleavage to the phenacyl radical and guaiacol. Subsequent formation of polarized guaiacoxyl radicals is due to secondary photo-oxidation. The cleavage of the ketyl radical is retarded in basic media and accelerated in acetic acid. Minor reaction pathways involving excited singlets cannot be ruled out by the current CIDEP observations.     

Direct STM investigation of cinchona alkaloid adsorption on Cu(III)

Scanning tunneling microscopy (STM) combined with cyclic voltammetry has been employed to investigate the adsorption of cinchonine on Cu(111). Similar to cinchonidine, cinchonine forms a long-range ordered adlayer with (4 x 4) symmetry on the substrate. The structural details on molecular adsorption were obtained by high-resolution STM images. On the basis of the previous results and obtained STM images, the quinoline ring is proposed to lie parallel to Cu(111) and serve as an anchoring group. The chiral quinuclidine moiety extends out of the surface to facilitate the interaction with the prochiral reactants.     

Colloidal adhesion of phospholipid vesicles: high-resolution reflection interference contrast microscopy and theory

High-resolution reflection interference contrast microscopy (HR-RICM) was developed for probing the deformation and adhesion of phospholipid vesicles induced by colloidal forces on solid surfaces. The new technique raised the upper limit of the measured membrane–substrate separation from 1 to 4.5 μm and improved the spatial resolution of the heterogeneous contact zones. It was applied to elucidate the effects of wall thickness, pH and osmotic stress on the non-specific adhesion of giant unilamellar vesicles (ULV) and multilamellar vesicles (MLV) on fused silica substrates. By simultaneous cross-polarization light microscopy and HR-RICM measurements, it was observed that ULV with the wall thickness of a single bilayer would be significantly deformed in its equilibrium state on the substrate as the dimension of its adhesive–cohesive zone was 29% higher than the theoretical value of a rigid sphere with the same diameter. Besides, electrostatic interaction was shown as a significant driving force for vesicle adhesions since the reduction in pH significantly increased the degree of deformation of adhering ULV and heterogeneity of the adhesion discs. The degree of MLV deformation on the solid surfaces was significantly less than that of ULV. When the wall thickness of vesicle increased, the dimension of contact zone was reduced dramatically due to the increase of membrane bending modulus. Most important, the adhesion strength of colloidal adhesion approached that of specific adhesion. Finally, the increase of osmotic stress led to the collapse of adhering vesicles on the non-deformable substrate and raised the area of adhesive contact zone. To interpret these results better, the equilibrium deformation of adhering vesicle was modeled as a truncated sphere and the adhesion energy was calculated with a new theory.     

Non-covalent reconfigurable microgel colloidosomes with a well-defined bilayer shell

Microgels are extremely interfacially active and are widely used to stabilize emulsions. However, they are commonly used to stabilize oil-in-water emulsions due to their intrinsic hydrophilicity and initially dispersed in water. In addition, there have been no attempts to control microgel structural layers that are formed at the interface and as a result it limits applications of microgel in advanced materials. Here, we show that by introducing octanol into poly(N-isopropylacrylamide-co-methacrylic acid) (PNIPAM-co-MAA) microgels, octanol-swollen microgels can rapidly diffuse from the initially dispersed oil phase onto the water droplet surface. This facilitates the formation of microgel-laden interfacial layers with strong elastic responses and also generates stable inverse water-in-oil Pickering emulsions. These emulsions can be used as templates to produce microgel colloidosomes, herein termed ‘microgelsomes’, with shells that can be fine-tuned from a particle monolayer to a well-defined bilayer. The microgelsomes can then be used to encapsulate and/or anchor nanoparticles, proteins, vitamin C, bio-based nanocrystals or enzymes. Moreover, the programmed release of these substances can be achieved by using ethanol as a trigger to mediate shell permeability. Thus, these reconfigurable microgelsomes with a microgel-bilayer shell can respond to external stimuli and demonstrate tailored properties, which offers novel insights into microgels and promise wider application of Pickering emulsions stabilized by soft colloids.

Inverse W/O Pickering emulsions and reconfigurable microgelsomes with a well-defined bilayer structure are prepared from octanol-swollen PNIPAM-co-MAA microgels and the combination of binary microgels, which promise wider application of soft colloids.     

大体积直接进样离子色谱法检测四甲基氢氧化铵中痕量阳离子

以抑制型电导离子色谱法检测四甲基氢氧化铵溶液中痕量碱金属和碱土金属离子.色谱条件为:IonPac CS12A阳离子交换色谱柱,20mmol/L甲烷磺酸淋洗液等度淋洗,抑制型电导检测.稀释液样品通过Dionex OnGuardⅡ氢型聚苯乙烯基强酸性树脂柱和0.22μm微孔尼龙膜处理.该方法的检测限(S/N=3)在0.024μg/L～0.156μg/L之间,标准曲线在低ng/L到低μg/L范围内呈现良好线性,RSD在10%左右,回收率为88%～115%.