添加非金属元素Si对固体超强酸SO_4~(2-)/TiO_2的改性研究

采用共沉淀法引入Ｓｉ对ＳＯ２－４／ＴｉＯ２进行改性，制得了ＳＯ２－４／Ｔｉ－Ｓｉ－Ｏ系列固体超强酸，试样经ＩＲ、ＳＥＭ、ＸＲＤ表征和低温正戊烷异构化活性测试，发现超强酸中心是硫酸根离子与金属原子Ｔｉ结合形成的双配位螯合结构，在超强酸性的样品中ＴｉＯ２均呈锐钛矿晶型。引入Ｓｉ仅迟滞ＴｉＯ２晶化过程，控制Ｓｉ在ＳＯ２－４／Ｔｉ－Ｓｉ－Ｏ体系中的含量可以有效调节固体超强酸的酸性，并提高正戊烷异构化反应的选择性。     

Spectroscopic study of solid-state photoreaction in organic crystal: Photopolymerization of dimethyl ester of α,α′-dicyano-p-phenylenediacrylic acid and diethyl ester of p-phenylenediacrylic acid

Raman spectroscopy has been used to study solid-state photopolymerization reactions in dimethyl ester of α,α′-dicyano-p-phenylenediacrylic acid (p-CPAMe) and diethyl ester of p-phenylenediacrylic acid (p-PDAEt). The reactants and products were characterized by infrared and Raman spectroscopy. Excitation and emission spectra suggest that in p-CPAMe exciton–phonon coupling is strong, but in the other monomer it is very weak. Raman phonon spectroscopic study reveal that in both the samples the reaction mechanism is homogeneous in the initial stages. However, in the later stages the reaction becomes heterogeneous in p-PDAEt. In p-CPAMe the lattice becomes disordered with the progress of polymerization and finally becomes amorphous whereas in p-PDAEt the lattice remains highly ordered. © 1992 John Wiley & Sons, Inc.     

Grain boundary segregation diagrams of α-iron

Based on thermodynamic analysis of interfacial segregation, the segregation enthalpy H ^o of a solute I in a given matrix was found to depend linearly on two mutually independent terms reflecting the type of interface and the solid solubility limit X _infI ^sup* at temperature T and can be written as In this equation, the structural dependence of interfacial segregation is contained in H ^*() which corresponds to the extrapolated segregation enthalpy of a solute with unlimited solubility in the matrix. The product [Tln(X _infI ^sup* )] is essentially constant with temperature, and can therefore be obtained from data for maximum solid solubility, [Tln(X _infI ^sup* )]_max. The parameter v>0 represents the relationship between the activity a _infI ^sup* of a solute at the bulk solid solubility limit in a given matrix and X _infI ^sup* , a _infI ^sup* =(X _infI ^sup* ) ^v , and is characteristic for the matrix. Using recent experimental data for silicon, phosphorus, and carbon segregation at well-characterized grain boundaries in oriented bicrystals of -iron, the averaged value was determined. Values of H ^*() range from -8 kJ/mol (general grain boundaries) up to +8 kJ/mol (special grain boundaries). These values are discussed and used for a more precise and generalized construction of grain boundary segregation diagrams of -iron.     

Wet carbon-based solid acid/NaNO_3 as a mild and efficient reagent for nitration of aromatic compound under solvent free conditions

Nitro aromatic compound can be obtained in high yields via nitration of aromatic compound with wet carbon-based solid acid and NaNO_3 under solvent free oxidation at room temperature.     

Synthesis of tumor-associated glycopeptide antigens for the development of tumor-selective vaccines

In contrast to normal cells, the glycoprotein profile on epithelial tumor cells is distinctly altered. Due to an incomplete formation of the glycan side-chains resulting from a premature sialylation, additional peptide epitopes become accessible to the immune system in mucin-type glycoproteins on tumor cells. These tumor-associated structure alterations constitute the basis for a selective immunological attack on cancer cells. For the construction of immunostimulating antigens, glycopeptide partial structures from the mucins MUC1 and MUC4 carrying the tumor-associated sialyl-T(N), alpha2,6-sialyl-T and alpha2,3-sialyl-T antigens have been synthesized. Employing different linkers such as the allylic HYCRON or the fluoride-sensitive PTMSEL anchor, the antigenic glycopeptide structures were constructed on the solid phase utilizing pre-assembled glycosyl amino acid building blocks prepared in solution by convergent chemical or chemoenzymatic strategies. The proliferation of cytotoxic T cells has been induced applying a construct composed of a sialyl-T(N) MUC1-glycopeptide conjugated with a tetanus toxin T cell peptide epitope.     

离线超临界流体萃取和气相色谱/质谱联用对实验室内空气中气相有机污染物的测试

通过团体吸附剂富集，再用超临界ＣＯ２脱附后用气相色谱及质谱技术对实验室内空气中气相有机污染物进行了考察。文中对采样和萃取条件进行了优化，并与热脱附所得结果做了比较。结果表明在２２ＭＰａ，８０℃时，用甲醇改性的超临界ＣＯ２进行萃取的结果优于热脱附法。该法鉴定出气相有机污染物中５２个组分，占色谱峰总面积的９９．６％。     

Evidence of a phase transition of RbHCO3 from high-resolution solid-state 13C and 87Rb NMR by comparison with KHCO3

A variable-temperature high-resolution 13C and 87Rb solid-state NMR study of powder rubidium hydrogencarbonate, RbHCO3, is presented for the first time. At ambient temperature, RbHCO3 is formed by centrosymmetric dimers linked by hydrogen bonds, but almost no information is available on this compound concerning proton disorder and the low-temperature phase. However, potassium hydrogencarbonate, KHCO3, which has an isomorphic structure for the high temperature phase, was well studied: it undergoes a non-ferroic, non-ferroelectric phase transition at Tc = 318 K between two monoclinic structures. The protons are disordered in an asymmetric double-well potential in the low-temperature phase, and the double-well potential becomes symmetric in the high-temperature phase. By comparison with recent solid-state NMR experimental results on KHCO3, we show that RbHCO3 undergoes a phase transition at Tc approximately 245 K, and give evidence that the proton dynamic disorder in both compounds is very similar.     

A view and a review of the melting of alkali metal halide crystals

Summary A representational model, proposed to account for the physical changes that accompany the melting of alkali halides, was described in Part 1 [1]. The liquid is portrayed as undergoing continual dynamic structural reorganization of its constituent ions between individual small domains, zones of various regular, crystal-type arrays. These alternative arrangements are stabilized by the enthalpy of melting, which, in liquids, relaxes the restriction for solids that only the single, most stable, crystal structure can be present. The dynamic character of the melt accounts for its fluid character and the loss of long-range order [1, 2]. This model is extended here to consider the phase diagrams of binary, common ion, alkali halide mixtures comprehensively reviewed in [3]. Factors determining whether each of these yields a eutectic, or a solid solution, on cooling are discussed and several trends in the 70-phase diagrams are identified. Eutectic formation, involving maintenance of the liquid state below the melting points of the pure components, is ascribed to the participation, in an extended dynamic equilibrium, of additional domains having the regular structures characteristic of double salts. The known crystalline double binary halides [3], Li/Cs or Rb/F, Cl, Br or I, melt at temperatures well below those of the simpler pure component salts. It is concluded that the set/liq model for melting, proposed in [1, 2], accounts for some important properties of the phase diagrams presented in [3].     

正庚烷在超稳Y沸石(USY)负载超强酸催化剂上加氢异构化

The Pt-bearing SO₄^2-/ZrO₂ superacid catalysts supported on ultra stable Y (USY) zeolite were prepared by impregnation and characterized by X-ray diffraction, nitrogen adsorption and Hammett indicators. Their catalytic activities were evaluated in the hydroisomerization of n-heptane with an atmospheric fixed-bed reactor. The catalysts possessed a high surface area, superacidity and well maintained pore structure of USY support. The supported catalysts with a suitable SO₄^2-/ZrO₂ loading exhibited a higher catalytic activity and selectivity than the unsupported SO₄^2-/ZrO₂ catalyst or the Pt supported on USY catalyst without superacid. At the reaction temperature of 220 ℃, over the catalyst with a Pt loading of 0.8wt% and ZrO₂ loading of 10wt%, the conversion of n-heptane could be as high as 35.2% with a selectivity of 87.9% for isomerization products.     

H3PW12O40 and its cesium salts as pentane isomerization catalysts at ambient temperature

The activity of Mg−Al basic heterogeneous catalysts in the reactions of alcohols with ethylene oxide was studied. The kinetics of alcohol oxyethylation was examined. The kinetic equation of the reaction was determined and the structure of products was studied. The distribution coefficients of the oxyethylation reaction products were calculated. A comparison of the catalytic activity of Mg−Al hydroxides and products of their thermal treatment was made.