Vibrational spectra of a ferrocenyl phosphine derivative chemisorbed on 3-aminopropylsilyl modified silica gel

Samples of silica gel dried at different temperatures, silica gel modified with 3-aminopropylsilyl (APS) and silica gel modified with APS and further with a ferrocenyl phosphine derivative were investigated by DRIFT, transmission FTIR and MicroRaman spectroscopy. The reaction between 3-aminopropyltrimethoxysilane (APTMS) and silica gel was mainly identified by the diminishing or vanishing intensity of the stretching band of the free OH groups in the silica gel. Further chemical reaction of the APS groups with a ferrocenyl phosphine derivative (suitable as ligand in homogeneous catalysis) was identified in the IR spectra by the appearance of the CN stretching band of the formed Schiff base, and diminishing intensity of the δ(NH₂) modes. According to the IR spectra the reaction of the ferrocenyl phosphine derivative with the APS-modified silica gel is almost quantitative. From the recorded IR and Raman spectra, conclusions concerning the substitution of APTMS methoxy groups during the chemisorption on silica gel were derived. Through deconvolution of the complex Raman band in the siloxy stretching region of the APS-modified silica gel, the newly formed siloxy bond was identified.     

Polyaniline-coated silica gel

Silica gel microspheres 7 and 15 μm in diameter were coated with an overlayer of polyaniline camphorsulfonate or hydrochloride during the oxidative polymerization of aniline. Coated silica gel and polyaniline precipitate were separated using a difference in sedimentation rate. In an alternative approach, the microspheres were modified with polyaniline in the presence of 35 nm colloidal silica. This technique prevented the macroscopic precipitation of polyaniline. Coatings of neat, 3-aminopropyl- and octadecyl-modified silica gel with polyaniline hydrochloride were compared. The surface composition of coated microspheres was characterized by X-ray photoelectron spectroscopy. Potential applications of particles in electrorheology, organic catalysis, and in modeling of conductivity behavior in composites are demonstrated.     

Solvent-free cyclopalladation on silica gel

Tertiary, secondary and primary benzylamines, as well as structurally different oxazolines readily reacted with Pd(OAc)₂ on silica gel to form cyclopalladated complexes containing a five or six-membered palladacycle with a (sp²)C-Pd or (sp³)C-Pd bond. The complexes were obtained in 45-98% yield, which is comparable with or exceeds the yields reported for preparation of the same compounds in solution. Aliphatic (sp³)C-H bond activation took place in the cyclopalladation of (S)-2-tert-butyl-4-phenyl-2-oxazoline on SiO₂ leading to the exclusive formation of the corresponding endo palladacycle, whereas two products were reported for the same reaction performed in AcOH.     

Radiation effect on polystyrene deposited and grafted on silica gel

The effect of radiation on polystyrene was studied in the presence and absence of silica gel by molecular weight measurement with GPC. Polystyrene crosslinked under vacuum in the absence of silica gel, but it either crosslinked or degraded by radiation, depending on the molecular weight of the polymer in the presence of silica gel. Part of the deposited polymer bonded to silica gel by radiation; the G value for graft-chain formation is in the range of 0.01–0.1. Irradiation of polystyrene grafted on silica gel resulted in degradation of the graft chain because of the transfer of energy from silica gel. The G value for main chain scission was about 2 when graft polymer was irradiated in the absence of homopolymer. The degradation of graft polymer was suppressed when the polymer was irradiated in the presence of homopolymer, and the amount of unextractable polymer from silica gel increased with increasing irradiation. This adds evidence to the estimation that an increase in grafting percent coupled with a slight decrease in molecular weight at a later stage of radiation-induced polymerization of styrene adsorbed on silica gel is due to a secondary effect of radiation on the polymer.     

变色硅胶吸附脱除模拟柴油中各种碱性氮化物

研究了变色硅胶吸附脱除氮含量为960.56μg/g模拟柴油中的碱性氮化物喹啉、苯胺和吡啶。比较了氧化铝、硅藻土、硅胶及变色硅胶对模拟柴油中喹啉的吸附脱除效果。采用XRD、低温N_2吸附-脱附和NH_3-TPD等方法对硅胶和变色硅胶进行了表征。考察了粒径、吸附温度、吸附时间、剂油质量比及共存芳香化合物(萘、苯或甲苯)对变色硅胶吸附脱除各种碱性氮化物的影响。变色硅胶吸附脱除碱性氮化物的顺序均为苯胺吡啶喹啉。吸附时间对三种氮化物的吸附脱除没有影响;吸附温度、变色硅胶粒径和共存芳香化合物对苯胺和吡啶的吸附脱除效果影响不大,对喹啉的吸附脱除效果影响较为明显;剂油质量比对三种氮化物的吸附脱除影响均较大,尤其是对喹啉影响最大。结果表明,变色硅胶吸附各种氮化物时Co能够与其中的N原子形成配位络合吸附。经焙烧再生,变色硅胶几乎完全恢复了对喹啉和吡啶的吸附脱除能力,并可多次再生,但变色硅胶再生后对苯胺的吸附能力损失较大。     

Cucurbituril anchored silica gel

A cucurbit[6]uril anchored silica gel is synthesized via reaction of perallyloxycucurbit[6]uril and mercaptopropyl functionalized silica gel and fully characterized by various spectroscopic methods; the amount of accessible host molecules attached on silica surface is quantified by fluorescence spectroscopy using FITC-spermine as a guest molecule.     

基于L-谷氨酸的手性硅胶球的制备及其应用

无机介孔硅球因其具有足够的机械强度、热稳定性,以及适应多种流动相的优点,成为高效液相色谱(HPLC)柱填料中使用最广泛和最重要的材料.但在此研究领域中,并未见球形的全无机手性硅胶用作HPLC手性固定相.该文以无机球形介孔硅胶作为研究对象,通过堆砌硅珠法,以硅溶胶为原料,L-谷氨酸(L-Glu)为手性源,在手性环境中制造...     

Ozonolysis of olfefins and acetylenes adsorbed on silica gel

Ozonation of phenyl ethylenes adsorbed on untreated silica gel results in aromatic aldehydes and on dried silica gel in ozonides and aldehydes. On the other hand ozonation of alkyl ethylenes on both types of silica gel results in a mixture of ozonides or polymeric peroxides similar to that obtained in aprotic solvents.     

Interrupted Nazarov cyclization on silica gel

Exposure of a mixture of propargyl vinyl ketone and a nucleophilic primary or secondary amine to activated dry silica gel in the absence of solvent leads to a cascade of reactions that results in the formation of an aminocyclopentenone. The reaction with triethylamine leads to a cross-conjugated cyclopentadienone.     

Study of radiation-induced polymerization of vinyl monomers adsorbed on inorganic substances. VII. Effect of pretreatment temperature of silica gel on styrene–silica gel system

To investigate the reaction mechanism of radiation-induced polymerization of styrene adsorbed on silica gel, the effect of pretreatment temperature of silica gel was studied. Preheating of silica gel was carried out at 200, 500, and 800°C. The number of silanol groups of silica gel surface decreased as preheating temperature increased. The rate of polymerization on the silica gel preheated at 500°C was faster than that at 200°C, but the polymerization rate on the silica gel preheated at 800°C was the lowest. These results suggest that rate of polymerization on the silica gel is affected by the conditions of silica gel surface such as the number of silanol groups and the pore size. At the same monomer conversion, percent grafting decreased as preheating temperature of silica gel increased. The GPC spectra of both graft polymers and homopolymers have two peaks at all preheating temperatures. The monomer conversion of low molecular weight peaks of graft polymers decreased as preheating temperature of silica gel increased. This result suggests that there is a probability that the grafting sites of low molecular weight peaks of graft polymers somehow interact with silanol groups.     

Energy and electron transfer reactions on silica gel and titania–silica mixed oxide surfaces

Research on Chemical Intermediates - The energy and electron transfer reactions of anthracene co-adsorbed with an electron donor on silica gel and titania–silica mixed oxides have been...     

Rheological studies of diatom encapsulation in silica gel

The mutual influence of the mineral and biological components of a specific bio-hybrid system consisting of diatom cells entrapped in a silica gel was studied by rheological methods. Small amplitude shear stress oscillatory measurements indicate that the culture medium alone has a strong impact on the silica network formation and viscoelastic properties. In contrast, the presence of diatoms does not significantly perturb the sol–gel process, and leads to a moderate change in the gel elasticity. Compression tests show that a large difference exists between the mechanical properties of silica gels and diatom shells, suggesting a limited impact of the gel strength on the diatom survival rate. We also show that the biological activity of entrapped diatoms can modify the structural evolution of the silica gel. This work indicates that rheological methods may be important tools for the optimization of whole cells encapsulation procedures and further confirms that encapsulated diatoms are able to interact with the surrounding silica materials.     

Spectroscopic kinetic characteristics of the fluorescence of anthracene sorbed on silica gel

The spectroscopic kinetic characteristics of the fluorescence of anthracene adsorbed on silica gel have been investigated. The formation of charge-transfer (CT) complexes between the anthracene molecules and acceptor sites on silica gel which had been heat-treated in a vacuum has been discovered. Along with the emission of the CT complexes, the luminescence of an excited CT complex, i.e., an exciplex, has been detected. Hypotheses regarding the nature of the electron-acceptor sites on silica gel have been advanced.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 1, pp. 118–123, January–February, 1985.     

Graft polymerization onto poly(methylvinylsiloxane)-bonded silica gel by gamma-ray irradiation

Poly(methylvinylsiloxane)-bonded silica gel was synthesized by condensation reaction between silica gel and the hydrolysis product of methylvinyldichlorosilane. Graft polymerization of styrene or indene onto poly(methylvinylsiloxane)-bonded silica gel was carried out by gamma-ray irradiation and compared with that onto silica gel. Homopolymer was found to be formed through a radical mechanism concurrently with an ionic mechanism in the graft polymerization. Probably genuine graft polymers are formed in the graft polymerization onto poly(methylvinylsiloxane)-bonded silica gel, while the product formed in the graft polymerization onto silica gel may be apparent graft polymers.     

Study of silica gel and copper silicate gel solubilities in high performance liquid chromatography

Summary After summarizing published results on silica gel and alkyl-bonded silica gel solubilities, the experimental solubility of unmodified silica and copper silicate gel (used in ligand exchange chromatography) in watermethanol-ammonia and water-acetonitrile-ammonia mixtures are given. These results demonstrate that silica gel solubility, measured by a static method, varies greatly with the water volume fraction of a ternary mixture. Curiously, no influence from the organic nature of the solvent was demonstrated. This observation is inconsistent with the fact that the copper silicate gel used in ligand-exchange chromatography with water-methanol-ammonia as mobile phase is attacked more rapidly than with water-acetonitrile-ammonia.An explanation based upon the variations of acid-base properties of silicic acid versus mobile phase dielectric constant values in conjunction with the methanol protophilic properties is proposed. Finally, it is shown that chromatographic columns filled with copper silicate gel have lifetimes of several months, if they are used with a procolumn (of copper silicate gel) and with acetonitrile as organic solvent with a volume fraction greater than 0.5 in the mobile phase.     

Fractality of materials based on silica gel

Based on the analysis of the isotherms of N₂ adsorption, the fractal dimension and other texture geometric parameters were determined for silica gel, modified silica gel, and relevant composite materials. The correlations between the texture parameters were found. A criterion for the estimation of the efficiency of using the composite adsorbent volume was proposed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 781–785, May, 2000.     

多孔活性硅胶的制备及吸附性能的研究

以硅酸钠和氯化铵为原料,通过添加表面活性剂制备高吸附活性的多孔硅胶.采用SEM,IR和XRI)等手段对硅胶样品的结构和形貌进行表征,并利用紫外分光光度法研究硅胶样品对垃圾渗滤液中有机污染物的吸附性能.结果表明,合成的硅胶样品是由纳米量级的无定形二氧化硅颗粒组成的多孔性、疏松状物质,对垃圾渗滤液中的有机物分子具有较强的吸...     

硅胶的表面硅烷化处理及其吸附性能研究

为研究改性硅胶对挥发性有机废气的吸附性能,分别采用十六烷基三甲氧基硅烷、辛基三乙氧基硅烷、苯基三甲氧基硅烷、一甲基三乙氧基硅烷对硅胶进行气相改性处理,试验研究了不同改性剂、改性时间对硅胶饱和吸附率的影响,考察了改性硅胶对甲苯、水二组分体系的吸附选择性.结果表明,硅胶对甲苯的吸附主要为物理吸附,长链的硅烷改性剂在60℃、...     

Adsorption of midmolecular peptides by fullerene modified silica gel

The adsorption properties of raw and processed silica gels and of silica gels modified with fullerene (fullerene-silica gel nanosystems) toward serum midmolecular peptides of ischemic origin were examined. A high adsorption capacity of the nanosorbents was found. The influence of fullerenes on the condition of silica gel was studied by solid-state NMR, and an increase in the silanol fraction at the adsorbent surface was demonstrated. It was shown that presence of fullerene C₆₀ in nanosorbents enables oxidation reaction of the adsorbed peptides, i.e., sorption of metabolites.     

The optimization of silica gel synthesis from chemical bottle waste using response surface methodology

To reduce the amount of hazardous chemical bottle waste in the environment, we report the optimization research of silica extraction in chemical bottle waste into silica gel. Alkali fusion and sol–gel process were utilised to prepare silica gel effectively. The alkali fusion process was carried out by adding sodium hydroxide to produce sodium silicate. Afterwards, silica gel was prepared by the sol–gel method using hydrochloric acid. Box-Behnken Design (BBD) was applied to Optimisation factors the poptimiseactors affecting the silica recovery. The factors that optimised mass ratio, particle size, and temperature. The optimum recovery of silica gel was obtained by SiO₂: NaOH mass ratio of 1:3, the particle size of 63–74 µm, and a temperature of 800 °C. The purity of silica gel optimum is 63.74% characterised using X-ray fluorescence. The structure of silica gel is the appearance of amorphous peaks at 2θ 20-30° characterised using an x-ray diffractogram. The silica gel surface was characterises using scanning electron microscopy-energy dispersive x-ray. It showed an irregular surface and characteristic showed that silica gel had a radius of 15.74 nm and a specific surface area of 297.08 m².