沸石分子筛的生成机理与晶体生长(Ⅻ)——ZSM-5沸石生成过程中液相硅酸根离子聚合态的研究

自从1964年Lentz等人提出三甲基硅烷化(TMS)方法研究硅酸盐结构后,人们意识到这种方法能够较真按着地反映硅酸盐结构及聚合状态。又由于硅烷化所得的衍生物(硅酯)易溶于有机溶剂,可以采用多种方法进行分析鉴定。本文应用TMS-GLC及TMSGPC二种方法研究了ZSM-5沸石生成过程中液相硅酸根离子聚合状态的变化。     

高聚硅酸根离子与单态铝酸根离子聚合反应及其水热晶化行为的研究

用核磁共振技术、紫外吸收光谱和硅钼酸反应等方法研究了反应体系中硅酸根离子和铝酸根离子的聚合态。发现反应产物的形态与硅酸根的聚合态有关,单态铝酸根离子与高聚硅酸根离子(聚合度>40)反应生成凝胶;单态铝酸根离子与单态或二聚态硅酸根离子反应生成沉淀。本文还研究了相同条件下的水热晶化行为,在沉淀区、混合区、凝胶区和溶胶区分别晶化得到沸石A、X、Y和P。     

分子轨道法研究硅酸盐分子结构

Pauling提出的硅酸盐结构规则,原则上只适用于纯粹离子键化合物。硅酸盐中硅酸根与金属原子之间的化学键是离子键,但是硅氧键却没有证据说明它是离子键。 Stewart等从X射线衍射实验和轨道电负性理论论证,α-石英中Si—O键仅有25％的离子性。还有人认为Si—O键的离子性为31～37.5％。我们用CNDO/2法计算得     

高聚硅酸根离子与单态铝酸根离子聚合反应及其水势晶…

用核磁共振技术，、紫外吸收光谱和硅钼酸反应等方面研究了反应体系中硅酸根离子和铝酸根离子的聚合态，发现反应产物的形成与硅酸根的聚合态有关，单态铝酸根离子民高聚硅酸根离子（聚合度＞４０）反应生成凝胶；单态铝酸离子与单态或二聚态硅酸根离子反应生成沉淀。本文还研究了相同条件下的水热晶人，在沉淀区、混合区、凝胶区和溶胶区分别晶化得到沸石Ａ、Ｘ、Ｙ和Ｐ。     

硅铝酸盐聚合反应的研究

应用NMR技术、激光拉曼光谱和硅钼酸方法研究了碱性硅铝酸盐聚合反应中铝酸根离子和硅酸根离子的存在状态及其变化.发现聚合反应是低分子量硅铝酸根离子之间或低分子量硅铝酸根离子与低分子量硅酸根离子之间的反应.     

L沸石导向剂陈化机制的研究

应用核磁共振和拉曼光谱研究了L沸石导向剂的陈化机制。实验结果表明,当铝源与硅源混合后铝酸根离子与硅酸根离子之间聚合反应很快,同时高聚态硅酸根离子发生了解聚。L沸石导向剂陈化反应的控制步骤是低聚态硅铝酸根离子之间或低聚态硅铝酸根离子与低聚态硅酸根离子之间的定向聚合反应。     

离子液体中5,5-二甲基-1,3-环己二酮与N-芳亚甲基芳胺反应合成 吖啶衍生物

在离子液体[bmim]Br中, 5,5-二甲基-1,3-环己二酮与N-芳亚甲基芳胺反应合成了一系列四氢吖啶-1,8-二酮衍生物, 该反应具有适应性广、产率高、污染少、环境友好等优点.     

毛细管色谱测定硅酸钙结构的研究

1964年Lentz首先用三甲基硅烷化法(TMS法)把一些含有不同聚合形态硅酸根的天然矿物(如橄榄石、浊沸石等)在保留原有硅酸根结构单元的前提下转化为相应的三甲基硅烷化衍生物(硅酸酯)。衍生物溶解在有机溶剂中,用气—波色谱法鉴定和测定,从而确定该矿物中硅酸根的聚合形态。这个方法既避免了化学分析法在溶解试     

非水介质中全硅沸石分子筛合成的研究 全硅方钠石和全硅ZSM-39 的晶化

在乙醇胺及甘油和乙二胺混合物两种非水介质中合成了全硅方钠石,在广泛的有机介质中进行了全硅沸石合成的研究,首次获得了全硅ZSM-39及未知结构硅酸盐K相,通过X射线衍射、红外光谱、组成分析、差热与热重分析等方法对合成的晶体产物进行了鉴定,应用液相电导率-硅酸根离子浓度测量方法对非水溶液的性质及对非水介质中全硅沸石生成的必要条件进行了探讨。     

钙镁硅酸盐溶度积常数的测定

借助高频等离子体发射光谱分别测定了一定温度下钙镁硅酸盐(CaO.mSiO2、MgO.mSiO2,其中m为模数)饱和溶液中Ca2 、Mg2 的平衡浓度,从而计算该温度下钙镁硅酸盐的溶度积常数,并研究了温度及水玻璃模数对钙镁硅酸盐溶度积常数的影响。结果表明,在同一温度下钙硅酸盐溶度积常数比镁硅酸盐溶度积常数小,在30℃下,水玻璃模数m为3.29时,钙硅酸盐的溶度积常数为1.14×10-8,而镁硅酸盐的溶度积常数为2.29×10-5;随着温度升高钙镁硅酸盐溶度积常数减小,当温度升高至90℃时,钙硅酸盐的溶度积常数减小至0.92×10-8,而镁硅酸盐的溶度积常数减小至1.68×10-5;在同一温度下随着水玻璃模数的增加,与其对应钙镁硅酸盐溶度积常数减小,由于模数的增加使沉淀中硅酸根离子直径变大,与钙镁离子反应生成钙镁硅酸盐晶体更易于沉淀,且更不易溶解,从而使钙镁硅酸盐的溶度积常数减小。     

Structure and dynamics of polymer-grafted clay suspensions

The structure and dynamics of polymer-grafted two-dimensional silicate layers in solution were investigated. The geometry of the individual silicate layers was examined by looking at both polarized and depolarized light scattering from dilute solutions, while higher-concentration systems were used to study the interaction and dynamics of polymer-grafted silicate layers in suspension. The form factor for an oblate ellipsoid was used to fit the polarized intensity profile, and values of a approximately 80 nm and b approximately 380 nm for the semi-axes were obtained. The 80 nm value compares reasonably with the dimensions of the polymer brushes grafted on the surface of the silicate layers. The modulus of the grafted silicate in solution, as determined by Brillouin scattering, is of the order of 10 GPa. The cooperative diffusion mechanism, typical of interacting polymer chains, is suppressed due to the high polymer osmotic pressure. The osmotic pressure is also responsible for the weak interpenetration of the densely grafted polymer chains on the surface of the silicate layers. The scattering data indicates that the polymer-grafted nanoparticles move via collective diffusion and experience significant decrease in mobility above their overlap concentration.     

Studies of the mechanism of formation of calcium silicate compounds by titration based on emission and atomic absorption spectroscopy

In this paper, the inhibition effect of silicate on emission or absorption of calcium was used for an investigation of the mechanism of formation of calcium silicate compounds. For that purpose, calcium chloride solutions were continuously titrated with a standard solution of sodium silicate (Na₂SiO₃), with simultaneous aspiration of the titrand into an air-hydrogen flame. During the titration, changes in the emission of the CaO-band at 622 nm and the CaOH-band at 554 nm were registered automatically on the recorder. Changes in the absorption of calcium were also registered at 422 nm. Thus curves of the same shape were obtained, with the same number of characteristic points, in which the SiO₂/Ca ratio is constant, when the concentration of silicate in the titrant varies. This fact suggests that calcium reacts with silicate to form compounds with a constant composition.Curves of the same shape were obtained by titration of a standard solution of sodium silicate, with a calcium chloride solution, while monitoring the changes in the absorption of calcium at 422 nm and changes in the emission of the CaO-band at 622 nm. In this case, the mole ratios SiO₂/Ca at the characteristic points of the curves were the same as in the case of the titration of calcium chloride solution with the silicate solution.On the basis of the mole ratios SiO₂/Ca at the characteristic points on the titration curves, which amount to 0.21, 0.33 and 0.50, the mechanism of formation of calcium silicate compounds was represented by chemical equations.It may be concluded that in the process of evaporation of spray droplets a chain of reactions take place, resulting in compounds that can be represented by the general formula xCaO·SiO₂.     

Effect of formulation of silica‐based solution on corrosion resistance of silicate coating on hot‐dip galvanized steel

Several silica‐based solutions with 50 g/l of SiO₂ were prepared from sodium silicate solutions and silica sol; the silicate conversion coatings were obtained by immersing hot‐dip galvanized steel sheets in these solutions. These solutions were characterized using high‐resolution transmission electron microscopy and ²⁹Si nuclear magnetic resonance; the morphology of the coatings was observed by SEM and atomic force microscopy while the corrosion resistance was evaluated by electrochemical measurements as well as neutral salt spray tests. The results show that the coatings obtained from the single silica sol solution had poor adhesion and the coating obtained from the sodium silicate solution with low SiO₂/Na₂O molar ratio was uneven. By adding the silica sol to the silicate solution with low molar ratio, uniform coatings with better protection property were obtained. According to the results of ²⁹Si nuclear magnetic resonance spectra, the effects of the distribution of silicate anions with various polymerization degrees in the silica‐based solutions on the microstructure and corrosion resistance of the silicate coatings are discussed. Copyright © 2016 John Wiley & Sons, Ltd.     

In vitro response of hFOB cells to pamidronate modified sodium silicate coated cellulose scaffolds

The aim of the present study was to evaluate the suitability of cellulose-based scaffolds coated with pure sodium silicate gel and sodium silicate gels accumulated with different concentrations of the bisphosphonate pamidronate as scaffolds for attachment, proliferation and differentiation of human fetal osteoblasts (hFOB 1.19). Human osteoblasts were cultured in vitro for a period up to 14 days on different cellulose scaffolds. Unmodified and sodium silicate coated cellulose scaffolds were used as control. Two surface-coated modifications of cellulose were applied. The scaffolds were coated in a modified two-step dip coating process with pure sodium silicate gel and pamidronate enriched sodium silicate gel, respectively. In order to investigate the influence of the pamidronate, concentrations of 0.667 mg Na-pamidronate/ml sodium silicate solution, 0.333 mg Na-pamidronate/ml sodium silicate solution and 3.33 x 10(-3) mg Na-pamidronate/ml sodium silicate solution were used for the coating process. Cell proliferation, vitality and attachment were examined by means of cell counting, WST-1 test, fluorescence and scanning electron microscopy. The relative grade of differentiation of hFOB cells was examined by using quantitative real-time polymerase chain reaction (qRT-PCR) analysis for the gene expression of alkaline phosphatase and osteocalcin. Proliferation and differentiation of human osteoblasts was enhanced by the sodium silicate coatings accumulated with pamidronate compared to pure sodium silicate coatings. There was a reciprocal correlation of vitality with the concentration of pamidronate. The highest vitality was found on surfaces with the lowest pamidronate accumulation. Alkaline phosphatase, an early differentiation marker, was overexpressed after 7 days in cells on all pamidronate-containing surfaces (up to 350% compared to untreated cellulose). Osteocalcin, a late differentiation marker, was overexpressed after 14 days in cells on all coated surfaces (up to 300,000% compared to untreated cellulose). The results indicate that due to the modified coating procedure a homogeneous coating and thus, an enhancement of cell attachment and subsequent cellular functions can be achieved. Low concentrations of pamidronate seem to have a relevant effect on cell proliferation and vitality and, therefore, can be recommended for the improvement of the properties of a biomaterial.     

Geopolymerization process of alkali–metakaolinite characterized by isothermal calorimetry

The geopolymerization process of metakaolinite activated by alkali and alkali silicate solutions was revealed. The effects of alkali concentration, modulus of alkali silicate solution and reaction temperature on geopolymerization were studied systematically by isothermal calorimetry, as well as X-ray diffraction and ²⁷Al/²⁹Si MAS NMR. Results show that the geopolymerization process of metakaolinite under alkali activation condition can be reasonably supposed into three stages: (I) destruction, (II) polymerization and (III) stabilization. The rate of geopolymerization in KOH solution is higher than in NaOH solution and reaches the maximum in 15 mol/L KOH solution during stage II. The extent of geopolymerization increases with increasing of alkali content regardless of the existence of silicate anions in activator.     

SiO2载体表面原位合成MCM-41的结构特征

以溶液硅源和表面硅源两种合成路线在SiO₂颗粒表面进行了MCM-41的原位合成,结果发现以两种方式均可得到MCM-41的有序结构。溶液硅源原位合成MCM-41的长程结构较好,两种硅源原位合成的MCM-41均能够在脱除模板剂过程中保持其长程有序结构。表面硅源原位合成MCM-41的孔径分布较窄,最可几孔径为3.81nm。本文还考察了OH/CTABr及SiO₂/OH比对表面硅源原位合成MCM-41长程结构特征的影响。     

Equilibrium and heat of adsorption of diethyl phthalate on heterogeneous adsorbents

The sorption of sodium silicate by synthetic magnetite (Fe3O4) at different pH conditions (pH 7-11) and initial silicate concentrations (1 x 10(-3) and 10 x 10(-3) molL(-1)) was studied using in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The analysis of infrared spectra of sodium silicate in solution as well as adsorbed on magnetite nano-particles clearly showed the evolution of different silicate species depending on pH and silica concentration. The silicate concentration studied (10 x 10(-3) molL(-1)) contained polymeric or condensed silicate species at lower pH as well as monomers at high pH, as evident from infrared spectra. Condensation of monomers resulted in an increased intensity of absorptions in the high frequency part (>1050 cm(-1)) of the spectral region, which contains information about both silicate in solution and sorbed silicate viz. 1300 cm(-1)-850 cm(-1). In the pH range studied, infrared spectra of sorbed silicate and sorbed silicate during desorption both indicated the presence of different types of surface complexes at the magnetite surface. The sorption mechanism proposed is in accordance with a ligand exchange reaction where both monodentate and bidentate complexes could exist at low surface loading level, the relative proportion of the complexes being due to both pH and concentration in solution. Oligomerization occurred on the magnetite surface at higher surface loading.     

Studies on silicic acid and its salts: XV. 29Si NMR study of sodium silicate in solution

The ²⁹Si NMR study of aqueous solution of sodium silicate of mole ratio SiO₂ to Na₂O equals one shows that the degree of polymerization of sodium silicate decreases with the decrease of the concentration, but the concentration of monosilicate anion increases, and that the lower the salt concentration, the faster is the rate of increase of the anionic concentration. The effect of SiO₂/Na₂O mole ratio and the concentration of sodium silicate on chemical shifts and spin-lattice relaxation time, T₁, of Si species and the effect of salt on degree of polymerization of sodium silicate in solution were also investigated.     

Attenuated total reflectance fourier transform infrared analysis of fly ash geopolymer gel aging

Structural changes in fly ash geopolymers activated with different sodium hydroxide and silicate concentrations are investigated using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy over a period of 200 days. A strong correlation is found between the concentration of silicate monomer in the activating solution and the position of the main Si-O-T stretching band in the FTIR spectrum, which gives an indication of the relative changes in the gel Si/Al ratio. The FTIR spectra of geopolymer samples with activating solution concentrations of up to 1.2 M SiO2 indicate that an Al-rich gel forms before the final gel composition is reached. The time required for the system to reach a steady gel composition depends on the silicate activating solution concentration and speciation. Geopolymers activated with solutions containing predominantly high-order silicate species rapidly reach a steady gel composition without first forming an Al-rich gel. A minimum silicate monomer concentration of approximately 0.6 M is required to shift the geopolymer synthesis mechanism from hydroxide activation to silicate activation. Silicate speciation in the activating solutions also affects zeolite formation and geopolymer microstructures, with a more homogeneous microstructure and less zeolite formation observed at a higher SiO2 content.     

非抑制电导检测离子色谱法测定硅藻培养液中硅酸根

采用戴安阴离子AS23(4 mm×250 mm)分析柱和AG23(4 mm×50 mm)保护柱、恒温电导检测器,建立了测定硅藻培养液中硅酸根(SiO2-3)含量的非抑制电导检测离子色谱法。以4 mmol/L碳酸钠为淋洗液,淋洗液流速1.0 mL/min,进样体积100 μL,采用峰高定量。该法测定SiO2-3的线性范围为0~40 mg/L,检出限为0.017 mg/L,重复测定同一标样的相对标准偏差( RSD,n=7 ) 小于5%,峰面积和峰高的RSD分别为10.9%、4.8%。测定不同生长时期硅藻培养液中的SiO2-3,样品的加标回收率为102%~120%。该法灵敏、准确、简便易行,适用于硅藻培养液中SiO2-3的检测。