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51.
研究了稀土金属氧化物La2O3,CeO2,Pr2O3,Nd2O3和Sin2O3对Ru-Bd堇青石催化剂的活性的影响。利用BET,BJH,SEM,XRD,CO化学吸附等测试手段对催化剂进行表征,并对催化剂的反应性能进行评价。SEM测试结果显示La2O3呈“虫卵状”聚集在茧青石表面,而CeO2呈立方CaF2型均匀的覆盖在堇青石表面,Ru粒子呈“孤岛状”均匀地分散在铈改性的堇青石载体表面。茧青石载体经CeO2改性后,催化剂的比表面积、比孔容积以及中、微孔数量均有所提高,孔径分布也得到了明显改善。活性数据显示,适量的稀土金属氧化物均能促进Ru-Ba/堇青石催化剂的活性,其中CeO2的改性效果最好,在10MPa,475℃,5000h^-1时CeO2改性的Ru-Ba/茧青石催化剂的氨合成转化率达到9.9%。研究了CeO2对氨浓度随温度、压力、空速变化趋势的影响。 相似文献
52.
LIU Yu LIU Gang XU Yue ZHANG Wen-xiang WU Shu-jie JIA Ming-jun . Key Laboratory of Surface Interface Chemistry of Jilin Province College of Chemistry . Measurement Testing Center Jilin University Changchun P. R. China 《高等学校化学研究》2009,25(3)
Mesoporous carbon monolith was synthesized by the direct carbonization of compressed sucrose/silica composite,which was prepared by using sol-gel method. The structural and textural properties of the materials were investigated by XRD,DRIFT,N2-adsorption and SEM. The characterization study shows that the resultant carbon monolith possesses a relatively high surface area,large pore volume and well interconnected pore system. Addition of a certain amount of citric acid or aluminum nitrate into the sol-gel pre... 相似文献
53.
Dipti Garg J.‐H. Ahn Ghanshyam S. Chauhan 《Journal of polymer science. Part A, Polymer chemistry》2010,48(5):1007-1015
Proline‐based polymer monoliths were synthesized via green protocol using lipase‐catalyzed esterification of methacrylic acid and 4‐hydroxyproline. Prolinyl methacrylate thus prepared was polymerized in situ as crosslinked monolith. The monolith was characterized by various techniques such as Fourier transform infrared, 1H‐NMR, 13C‐NMR, scanning electron microscopy (SEM), X‐ray diffraction (XRD), and nitrogen analysis and used as catalyst in aldol reactions. The swelling behavior of the monolith was also studied as function of various external parameters like pH and temperature. The monoliths synthesized with 1% crosslinker was selected as candidate monolith for use as catalyst in aldol reaction, which was studied as a function of time, temperature, substrate structure, and amount of water:EtOH. The catalysts exhibited high efficiency in the cross aldol reaction, especially with the aromatic substrates having electron withdrawing substituent, and also good activity retention was observed when recycleability was studied up to five cycles. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1007–1015, 2010 相似文献
54.
采用共沉淀法制备了一系列 CexZr0.9-xLa0.1O1.95-Al2O3 储氧材料 (其中 CexZr0.9-xLa0.1O1.95 与 Al2O3 的质量比为 1; x = 0, 0.3, 0.5, 0.7 和 0.9), 以其为载体, 制备了一系列负载铁基整体式催化剂. 考察了该系列催化剂催化甲烷燃烧反应性能, 并用低温 N2 吸附-脱附、储氧能力测试、X 射线衍射和 H2 程序升温还原等手段对载体和催化剂进行了表征. 活性测试结果表明, 当 x = 0.7 时, 催化剂活性最高, 可在 V(CH4) = 1% 和 50 000 h1 条件下使甲烷 465 oC 起燃, 615 oC 完全转化. CexZr0.9-xLa0.1O1.95-Al2O3 样品同时具有较高的储氧能力、较高的比表面积和抗热老化能力. 当 x = 0.5 和 0.7 时, 催化剂载体以 CeZrLaAlO 固溶体存在, 抗老化能力最好, 且 x = 0.7 时, 催化剂最易被还原. 相似文献
55.
Jin‐Xing He Guo‐zhen Fang Yu‐chao Yao Shuo Wang 《Journal of separation science》2010,33(20):3263-3271
In this work, a novel approach of preparing molecularly imprinted film‐derivatized silica monolith materials was developed by a two‐step procedure. The silica monolithic support was first prepared by the sol–gel method with tetramethoxysilane as the precursor. Subsequently, vinyl groups were introduced onto the surface of silica monolith by immobilization of γ‐methacryloxypropyltrimethoxysilane. The prepolymerization mixtures, consisting of methacrylic acid as a functional monomer, ethylene dimethacrylate as a crosslinker, sulfamethazine as a template molecule and an ionic liquid as porogen, were injected into the silica monolith immobilized vinyl groups to form the molecularly imprinted films on the surface of the vinyl functionalized silica monolith. The monolithic materials were characterized by SEM, Fourier transform IR and solid‐state reflection UV spectra. The resulted imprinted materials were evaluated under CEC and HPLC mode. The results indicated that there were enough recognition sites on the surface of the imprinted film‐derivatized monolithic materials for selectively recognizing sulfamethazine from the sulfonamide mixture. Ionic liquids, which was utilized as the porogens, could improve the flow‐through property and the imprinting effect of the molecularly imprinted film‐functionalized silica monolithic materials. 相似文献
56.
The gain in separation efficiency for protein digests using long monolithic columns has been evaluated for a LC‐MS system with capillary monolithic columns of different lengths (150 and 750 mm). A mixture of BSA, α‐casein and β‐casein tryptic digests was used as a test sample. Peak capacity and productivity (peak capacity per unit time) were determined from base peak chromatograms and MS/MS data were used for protein identification by MASCOT database searching. Peak capacity and protein identification scores were higher for the long column. Analyses with similar gradient slope for the two columns produced ratios of the peak capacities that were slightly higher than the expected value of the square root of the column length ratio. Peak capacity ratios varied from 2.7 to 4.0 for four different gradient slopes, while protein identification scores were 2–4 times higher for the long column. Similar values were obtained for the productivity of both columns and the highest productivity was obtained at gradient times of 45 and 75 min for the short and long column, respectively. The use of long monolithic columns improves peptide separation and increases reliability of protein identification for complex digests, especially if longer gradients are chosen. 相似文献
57.
The use of polymeric materials in ion-exchange chromatography applications is advantageous because of their typically high
mechanical stability and tolerance of a wide range of pH conditions. The possibility of using polymeric monoliths in ion-exchange
chromatography is therefore obvious and many of the same strategies developed for polymeric particles have been adapted for
use with polymeric monoliths. In this review different strategies for the synthesis of polymeric monoliths with ion-exchange
functionality are discussed. The incorporation of ion-exchange functionality by co-polymerization is included, as also are
different post-polymerization alterations to the monolith surface such as grafting. The formulations and strategies presented
include materials intended for use in analytical separations in ion-exchange chromatography, sample pre-treatment or enrichment
applications, and materials for capillary electrochromatography. Finally, examples of the use of polymeric monoliths in ion-exchange
chromatography applications are included with examples published in the years 2003 to 2008.
相似文献
Emily F. HilderEmail: |
58.
The separation of three selective serotonin reuptake inhibitors (SSRIs) by capillary electrophoresis (CE) with fully integrated solid-phase extraction (SPE) is described. Polymeric monolithic SPE modules were prepared in situ within a fused silica capillary from either butyl methacrylate-co-ethylene dimethacrylate or 3-sulfopropyl methacrylate-co-butyl methacrylate-co-ethylene dimethacrylate. Using a 1 cm SPE module placed at the inlet of the capillary, a mixture of sertraline, fluoxetine and fluvoxamine was extracted from aqueous solution by applying a simple pressure rinse. Under pressure-driven conditions, efficient elution was possible from both SPE materials investigated using 50 mM phosphate buffer, pH 3.5 in acetonitrile (20/80, v/v). Two different strategies were investigated for the efficient elution and subsequent CE separation. Injection of an aqueous sample plug directly into the non-aqueous elution/separation buffer was found to be unsuitable with poor elution profiles observed in the electrodriven mode. Alternatively, a sample plug equivalent to several capillary volumes could be injected by pressure followed by filling the capillary with the non-aqueous elution/separation buffer from the outlet end using a combination of pressure and electrodriven flow. Using a neutral monolith, efficient elution/separation was not possible due to an unstable electroosmotic flow (EOF), however, by adding the ionisable monomer, 3-sulfopropyl methacrylate to the SPE module to increase and stabilise the EOF, it was possible to achieve efficient elution from the SPE module, followed by baseline separation by CE using a 200 mM acetate buffer, pH 3.5 in acetonitrile (10/90, v/v). With enrichment factors of over 500 achieved for each of the analytes this demonstrates the potential of in-line SPE-CE for the sensitive analysis of these drugs. 相似文献
59.
A new capillary electrochromatography (CEC) column for the simultaneous analysis of cationic, neutral, and anionic compounds
using CEC-ESI-MS is described. Three different silica monolith columns were prepared by changing the poly(ethylene glycol)
(PEG) contents for comparison of the separation property of these columns. Different separation programs were used for the
simultaneous separation of different charged compounds under the same conditions. The column prepared with 80 mg of PEG separated
typical compounds within 15 min using 1 M formic acid as the electrolyte. The analytes migrated in the order of cationic,
neutral, and anionic compounds, which means that the migration order was mainly determined by the electrophoresis. The hydrodynamic
flow by pressure from the inlet side was significant for a stable analysis to be achieved. The effect of the composition of
the sheath liquid was also examined. All analytes (14 amino acids, thiourea, urea, citric acid, and ATP) were detectable when
1% acetic acid in 50% (v/v) methanol was used as the sheath liquid. 相似文献
60.
A novel terminal‐vinyl liquid crystal crown ether (2‐[4‐(3‐undeceny‐1‐yloxy)‐phenyl]‐2‐[4′‐(4′‐carboxybenzo‐15‐crown‐5)‐phenyl] propane) (LCCE) was synthesized and used to modify hybrid silica‐based monolithic column possessing vinyl ligands for CEC. The monolithic silica matrix containing vinyl functionalities was prepared by in situ co‐condensation of tetramethoxysilane and vinyl‐trimethoxysilane via sol–gel process and chemically modified with LCCE by free radical polymerization procedure using α,α'‐azobisisobutyronitrile as an initiator. Morphology of the monolithic column was examined by SEM and mercury porosimetry and the successful incorporation of terminal‐vinyl LCCE to the vinyl‐hybrid monolith was characterized by infrared spectra. Polycyclic aromatic hydrocarbons, benzenediols, carbamate pesticides and steroids, were successfully separated on the column. The separations were dominated hydrogen bonding supplied by crown ether and hydrophobic interaction offered by the liquid crystal. The effect of ACN concentration on separation performance was studied and the result indicated that RP retention mechanism played an important role. Reproducibilities of migration times for the six selected polycyclic aromatic hydrocarbons were reasonable, with relative standard deviation less than 3.50% for five consecutive within‐column runs and were 8.38–9.11% for column‐to‐column measurements of three columns. 相似文献