高效液相色谱法所用大孔硅胶填料的制备

对国产ＧＹＱＧ球形硅胶施加高压水热处理并进行扩孔，制备了用于高效液相色谱法的大孔硅胶填料，考察了扩孔压力，扩孔温度和扩孔时间对平均孔径和比表面积的影响。并将产品日本ＳＩＬ－３００３×１０＾－８ｍ硅胶进行了物理性质和孔分布的对比实验，结果表明ＧＹＱＧ硅胶扩孔后平均孔径为２０～３０ｎｍ接近日本ＳＩＬ－３００３×１０＾－８ｍ硅前平平均孔径２５ｎｍ。display structure     

Mesoporous Titanium-containing Silicas. Synthesis and geometrical characteristics

Mesoporous titanium-containing silicas with TiO₂ contents from 1 up to 70 mol% were prepared. The obtained samples have been characterized by the powder X-ray diffraction data, the diffuse reflectance infrared Fourier transform method, and nitrogen adsorption at 77 K. Specific surface area, total pore volume, distribution pore volume on pore sizes were determined from nitrogen adsorption isotherm for synthesized titanosilicas. This revised version was published online in August 2006 with corrections to the Cover Date.     

Physico-chemical characterization of nanofiltration membranes.

This study presents a methodology for an in-depth characterization of six representative commercial nanofiltration membranes. Laboratory-made polyethersulfone membranes are included for reference. Besides the physical characterization [molecular weight cut-off (MWCO), surface charge, roughness and hydrophobicity], the membranes are also studied for their chemical composition [attenuated total reflectance Fourier spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS)] and porosity [positron annihilation spectroscopy (PAS)]. The chemical characterization indicates that all membranes are composed of at least two different layers. The presence of an additional third layer is proved and studied for membranes with a polyamide top layer. PAS experiments, in combination with FIB (focused ion beam) images, show that these membranes also have a thinner and a less porous skin layer (upper part of the top layer). In the skin layer, two different pore sizes are observed for all commercial membranes: a pore size of 1.25-1.55 angstroms as well as a pore size of 3.20-3.95 angstroms (both depending on the membrane type). Thus, the pore size distribution in nanofiltration membranes is bimodal, in contrast to the generally accepted log-normal distribution. Although the pore sizes are rather similar for all commercial membranes, their pore volume fraction and hence their porosity differ significantly.     

不同环大小分子筛对钼基分子筛催化剂上甲烷无氧芳构化反应的影响

 钼基分子筛催化剂，由于不同分子筛的孔道大小及孔道形状不同\r\n，对甲烷芳构化反应表现出不同的催化性能．具有8元环孔道结构的小\r\n孔ERS－7分子筛没有催化活性，说明甲烷的芳构化反应离不开分子筛孔\r\n道的择形作用，较小的孔道中不能生成苯等芳烃．具有10元环孔道结构\r\n的ZSM－5，ZSM－11和ZRP－1三种分子筛具有较好的催化性能，但由于\r\n其孔道大小及孔道形状的差别在催化行为上表现出一定的差异．具有1\r\n0元环和12元环孔道结构的MCM－22分子筛，尤其对苯等轻芳烃而言，催\r\n化性能最佳．具有12元环孔道结构的JQX－1以及中孔分子筛SBA－15，\r\n虽然具有一定的催化性能，但活性较低．研究结果表明，孔道大小与苯\r\n分子动态直径相近或孔道稍大的分子筛是催化甲烷芳构化反应的良好载\r\n体，孔道过大或过小都不利于苯和萘等芳烃的生成．     

3-D-electron microscopy configuration of TMOS wet silica gels prepared by the quick-freeze,deep-etching-rotary-replication technique

Silica gel provides a useful medium for crystal growth; solution growth is confined to pores left free by the polymer during its development. All growth steps depend on the gel structure, which is not completely known for crystal growth conditions. Therefore, a three-dimensional (3-D) visualization has been performed for two TMOS aqueous gels, which are rather fragile: the quick-freeze, deep-etching, rotary-replication method has been applied for sample preparation. An original surface labeling technique has been used for surface recognition. The results concern the distribution of macropores that are responsible for crystal nucleation; micropores whose total volume is larger have not been visualized due to the limits of the method. These results are discussed in comparison with previous data performed by light scattering.     

Characterization of Titania/Silica Gel by Means of Low-Pressure Nitrogen Adsorption

Adsorbents synthesized by grafting of titania onto mesoporous silica gel surfaces at different temperatures were studied by means of nitrogen adsorption–desorption and water desorption. The pore size distribution f(R_p) of titania/silica gel depends on the titania concentration (C_TiO2) and the temperature of titania synthesis. Nonuniformity of TiO₂ phase is maximal at a low C_TiO2 value (3.2 wt.% anatase deposited at 473 K), and two peaks of the fractal dimension distribution f(D) are observed at such a concentration of titania, but at larger C_TiO2 values, only one f(D) peak is seen. More ordered filling of pores and adsorption sites by nitrogen, reflecting in the shape of adsorption energy distributions f(E) at different pressures of adsorbate, is observed for adsorbent with titania (rutile+anatase) grafted on silica gel at a higher temperature (673 K).     

Effects of type of adsorption isotherms on parallel diffusion of sulfonated dyes into porous cellulose membrane

Transport phenomenon of three sulfonated azo dyes, C.I. Acid Red 88, C.I. Direct Yellow 12, and C.I. Direct Blue 15 into water-swollen cellulose membranes has been analyzed on the basis of parallel transport theory by surface and pore diffusion. Langmuir equation was applied into the mass balance equation to estimate dye concentration in the pores. The results were compared with the results obtained by applying Freundlich equation in our previous papers. The surface diffusivity (D _s) and the pore diffusivity (D _p) for the parallel diffusion model obtained by applying Langmuir equation agreed with those obtained by applying Freudlich equation. The theoretical concentration profiles for parallel diffusion calculated usingD _s andD _p coincided accurately with the experimental data when we applied either Langmuir or Freundlich equations.     

Microfabricated bioreactor chips for immobilised enzyme assays

A microfabricated device is reported that has been designed to permit the in situ packing of a section of channel with enzyme immobilised onto controlled pore glass (CPG). It is fabricated from glass and polydimethylsiloxane and to prevent dead volumes, has dedicated channels for packing the reactor. The device has the advantage of being simple in design, the flow through enzyme reactor channel being simply a widened section of the analyte channel. The system is suitable for both hydrodynamic and electro-osmotic pumping, and is designed such that when the packing is exhausted it can be repacked. Controlled pore glass provides a reproducible none swelling, high porosity medium onto which the enzyme could be immobilised. The large particle size meant that it was vital to optimise the immobilisation procedure in order to achieve acceptable enzyme activity. The microfabricated device was developed with two enzymes of different molecular masses; alkaline phosphatase and xanthine oxidase. The pore size of the CPG was found to be very important for xanthine oxidase, where the 697 Å pore size (120-200 mesh) CPG was found to give the highest activity (18-20% activity retained after immobilisation). The microfabricated device was used for the assay of p-nitrophenyl phosphate and hypoxanthine with spectrophotometric detection at 405 and 470 nm, respectively. The limits of detection were 5 and 8 μM, respectively.     

Structural and Adsorptive Characteristics of Pyrocarbon/Silica Gel Si-60

Pyrocarbon/silica gel adsorbents (carbosils, CS) with mesoporous Si-60 (Merck, granule size 0.2–0.5 mm) modified by pyrolysis of CH₂Cl₂ at 823 K and reaction time from 0.5 to 6 h and then hydrothermally treated at 473 K for 6 h were studied by means of TEM, adsorption and ¹H NMR methods. Changes in the structural and adsorptive characteristics of hybrid adsorbents before and after hydrothermal treatment, which depend on pyrocarbon content (C _C), were analyzed on the basis of TEM micrographs and p-nitrophenol and nitrogen adsorption isotherms treated using a constrained regularization method. Interfacial water layers in aqueous suspension of CS were investigated by means of ¹H NMR with freezing-out of bulk water at T < 273 K showing nonlinear changes in the Gibbs free energy of interfacial water with increasing C _C because of nonlinear dependence of the structural characteristics of pyrocarbon deposits and CS as a whole on C _C.     

高比表面积窄孔分布氧化铝的制备研究 Ⅰ.沉淀条件的影响

 以硫酸铝液为原料，以氨水、氢氧化钠和铝酸钠为碱沉淀剂，采用pH摆动法制备了高比表面积、大孔径、窄孔分布、大孔体积氧化铝，考察了沉淀剂、沉淀温度及沉淀时酸侧pH值对氧化铝物性的影响，并对pH摆动法与等pH沉淀法的结果进行了比较．结果表明，通过改变制备参数可以获得高比表面积、大孔体积的氧化铝，当沉淀温度为70℃，pH摆动3或4次时，氧化铝的孔体积可高达1．0ml／g，比表面积仍大于300m2／g．用pH摆动法制得的样品比用等pH沉淀法制得的样品容易酸溶，对挤压成型有利．不同样品在酸溶液中的分散性表明，用氨水沉淀剂可获得相对较小的沉淀粒子．改变沉淀时酸侧的pH值，可导致沉淀粒子的结构发生变化．