Adsorption of Acetaldehyde,Propionaldehyde, and Butyraldehyde on Molecular Sieve 13X

Abstract

Adsorption isotherms for acetaldehyde, propionaldehyde, and butyraldehyde on Davison molecular sieve 13X were determined gravimetrically at three temperatures. The isoteric heat of adsorption of acetaldehyde and propionaldehyde decreased initially with the increase in loading, then increased up to a certain point after which it decreased again. For butyraldehyde the heat of adsorption initially increased and then decreased with increased loading. The equilibrium adsorption data reduce to a single characteristic curve when correlated according to Polanyi's potential theory. Recently proposed isotherm equations for heterogeneous surfaces by Sircar and Hines et al. were used to correlate the isotherm data. The BET equation gave a good correlation of the data for a relative pressure range of 0.05 ≤ P/P, ≤ 0.25. The monolayer surface coverage and surface area were calculated by the Langmuir and the BET equations. The Langmuir equation consistently provided a larger estimate of the surface area than did the BET equation.     

Adsorption of Chlorinated Hydrocarbon Pollutants on Silica Gel

Abstract

A survey of indoor air pollutants was conducted. The removal of six chlorinated hydrocarbons, including methyl chloride, methylene chloride, chloroform, carbon tetrachloride, 1,1,1-trichloroethane, and tetrachloroethylene was performed using adsorption methods. The equilibrium uptakes of the six indoor pollutants on silica gel were determined gravimetrically at 25°C and at pressures up to saturation. The modified potential theory proposed by Dubinin and coworkers was used to correlate the adsorption data.     

Correlation of Methyl Chloride,Methylene Chloride,Chloroform, and Carbon Tetrachloride Adsorption Data on Silica Gel

Abstract

Adsorption data of the homologous series methyl chloride, methylene chloride, chloroform, and carbon tetrachloride on silica gel were measured gravimetrically at 288, 293, and 298 K. For all the chlorinated hydrocarbons examined, the isotherms were Type I, showing no apparent hysteresis between the adsorption and desorption cycles. Experimental data were compared with the calculated equilibrium uptake as predicted by a synthetic heterogeneous isotherm model in which the local isotherm on a site is given by the Jovanovic equation and the distribution of energetically different sites is represented by a Morse-type energy distribution function. The absolute errors between the values calculated by the heterogeneous isotherm model and the experimental data ranged from 1.17 to 2.67%. Energy distribution functions showed that silica gel exhibits the same degree of heterogeneity for all of the adsorbates in the homologous series.     

Nitrogen Production Efficiency for Acetaldehyde and Propionaldehyde in Lean NO x Reduction over Anatase Titania

The nitrogen formation efficiencies, defined as the number of nitrogen molecules formed for every reductant molecule consumed were determined for acetaldehyde and propionaldehyde in the reduction of NO₂ under lean conditions over anatase TiO₂. The efficiency increased with increasing NO₂/reductant in the feed, reaching 0.61 ± 0.05 for NO₂/acetaldehyde between 1.5 and 3.0 and 0.85 ± 0.08 for NO₂/propionaldehyde between 3.8 and 5.7. Simultaneously, the CO/CO₂ ratio as well as the small concentration of N₂O in the product stream increased. The results suggested that at higher NO₂/reductant ratios, the reaction between the reductant and adsorbed NO₂ accounted for a large majority of the reaction. The results were consistent with the IR results, which showed that surface nitro groups reacted readily with acetaldehyde. The implications of these results on the NO₂ reduction mechanism were discussed.     

Oxidation of Acetaldehyde and Propionaldehyde on a VOx/TiO2 Catalyst in the Presence of Water Vapor

The partial oxidation of acetaldehyde and propionaldehyde on a TiO₂ supported VO_x catalyst in the presence of water vapor was investigated at temperatures from 120 to 280 °C. Depending on the kind of aldehyde and reaction temperature, the selective oxidation to the appropriate carboxylic acid and an oxidative splitting to lower carboxylic acids took place. Acetaldehyde was oxidized to acetic acid with selectivities up to 82 % at ～ 200 °C whereas propionic acid was formed only with selectivities of about 20 % at ～ 140 °C in the oxidation of propionaldehyde. The oxidative cleavage of propionaldehyde led to the formation of more acetic acid than formic acid, which was in agreement with the higher formation of CO_x compared to that in the acetaldehyde oxidation. The presence of water and the increasing concentration of oxygen in the feed was found to enhance the selectivity towards the formation of C₁ to C₃ carboxylic acids by inhibiting the total oxidation of aldehydes and carboxylic acids.     

活性炭硅胶吸附法油气回收技术及其应用

油库在运行过程中,其油气排放过程主要发生在发油阶段。基于此对油库发油阶段实施油气回收。吸附法油气回收技术,采用吸附剂活性炭加硅胶进行填充,降低吸附床层的吸附热,提高安全性,延长活性炭的寿命。     

Adsorption of Uranium(VI) and Zirconium(IV) from Acid Solutions on Silica Gel

Abstract

Adsorption of uranium(VI) and zirconium(IV) from aqueous solutions on silica gel was investigated by the batch equilibration method. The influence of shaking time and concentrations of nitric acid (i.e., pH of solution) and metal ions in solution were studied. Adsorption of uranium(VI) and zirconium(IV) increases with an increase of pH (decrease of nitric acid concentration) and ion concentrations. The adsorption mechanism of uranium(VI) and zirconium(IV) from aqueous solutions on silica gel is proposed. It is shown that zirconium(IV) and uranium(VI) can be separated if the concentration of nitric acid in solution is higher than 0.01 mol/dm³.     

气相二氧化硅和胶体电池

通过对气相二氧化硅本身的特性和气相二氧化硅成胶性能的分析,提出优异的触变性能是气相二氧化硅用于胶体电池的关键因素,也是未来胶体发展的方向。使用优质气相二氧化硅,配合完善的电池组件设计和选择,可以保证较高的胶体电池气体再化合效率,也使得胶体电解液不易干涸,这样的胶体电池才会有着较长的循环寿命。     

Adsorption of Colloidal Silica on Alumina and of Colloidal Alumina on Silica

The mutual adsorption of colloidal silica on alumina and of colloidal alumina on silica and silicate materials occurs in aqueous suspension at about pH 4. It is shown that the adsorption of colloidal particles on the surface of opposite charge is limited to essentially a monoparticle layer. An adsorbed layer of fibrils of colloidal alumina on the surfaces of silica, asbestos, graphite, and finely divided clay is shown in electron micrographs. The effect of the adsorbed colloid on dispersibility of the substrate materials is discussed.     

Pore Structure of Silica Gel

The effect of washing on the texture of silica gel has been investigated in terms of parameters such as porosity, pore size distribution, surface area and absorption of moisture. It was observed that if silica gel (before activation) is washed with water containing dissolved ions such as Ca and Mg wider pores are formed at the expense of smaller ones. This phenomenon has been explained in terms of change in the size distribution of gel particles which is brought about by solution of very fine particles followed by growth, through condensation, of larger particles. The experimental observations have been interpreted to suggest guidelines to control the texture of gels by washing with solutions comaining different cations.     

Adsorption of Noble Metals Using Silica Gel Modified with Surfactant Molecular Assembly Containing an Extractant

Silica gel modified with a surfactant, Triton X-100 molecular assembly containing an extractant, 1-(2-pyridylazo)-2-naphthol, was prepared as an adsorbent to adsorb palladium, platinum, and gold. In this study, methods of metal recovery and mutual separation from the metal coexisting solution were studied by using the modified silica gel (PT100S). The effects of pH, chloride-ion, and metal-ion concentrations on the metal adsorption rate were evaluated through batch experiment. Pd(II) and Au(III) were adsorbed on PT100S, while Pt(IV) was not adsorbed. Furthermore, it was found that Pd(II) reacted with an adsorption site on PT100S, and that Au(III) reacted with a different adsorption site from Pd(II). These results enabled to separate the metals using a column packed with PT100S.     

硅烷化硅胶的制备和性能测定

利用氯丙基三氯硅烷与硅胶反应生成硅烷化硅胶,从不同的条件下合成CP-硅胶并对其性能进行评定和表征,同时对CP-硅胶的反应机理进行了初步的探讨,对未来的研究方向进行了展望.     

硅胶的制备及应用现状

硅胶不溶于水和任何溶剂,无毒无味,化学性质稳定,除强碱、氢氟酸外不与任何物质发生反应。根据其孔径的大小分为：大孔硅胶、粗孔硅胶、B型硅胶、细孔硅胶。由于孔隙结构的不同,因此它们的吸附性能各有特点。硅胶是一种高活性的吸附材料,通常以硅酸钠和硫酸为原料制备,文中介绍了各种硅胶的生产工艺,论述了硅胶的应用现状。     

浅谈硅胶的类型结构、性能特点及其应用

在涂料工业中,硅胶是最重要的无机消光剂。硅胶层析技术在中药化学中的应用越来越广泛。现在,硅胶的应用技术已经渗透到各行各业。分别介绍了基础硅胶,微粉硅胶,功能化硅胶的组织结构、功用原理及其特点,同时分别阐述了硅胶在工业生产中的典型应用,硅胶在涂料工业中的典型应用,硅胶在其他行业中的典型应用。     

聚维酮碘在硅胶表面的固载化及其杀菌性能

将N-乙烯基吡咯烷酮(NVP)接枝聚合到硅胶表面,制得接枝微粒PVP/SiO2;使接枝微粒PVP/SiO2在乙醇溶液中与碘发生络合反应,形成水不溶的聚维酮碘PVP-I2/SiO2,即实现了聚维酮碘的固载化. 考察了各种因素对络合反应的影响规律,用红外光谱与化学分析法对功能微粒PVP-I2/SiO2的化学结构与组成进行了表征. 以大肠杆菌为致病菌体,采用平板活菌计数法研究了PVP-I2/SiO2的杀菌性能. 研究结果表明,PVP/SiO2与碘的络合反应的适宜温度为60℃,经12 h后达到络合平衡,络合度随溶液中碘浓度的增大而提高,最大约为0.16%(w). 固载化的功能微粒PVP-I2/SiO2具有很强的杀菌能力,在药剂量为5 g/L的条件下,与浓度为109 CFU/mL的菌悬液接触3 min,即可使杀菌率达100%;胞外DNA和RNA测定与TTC-脱氢酶活性测定结果验证了水不溶聚维酮碘PVP-I2/SiO2的杀菌机理.     

Methanol Vapor Adsorption on Silica and Soda-Lime-Silica Glass

Methanol vapor adsorption isotherms on vitreous silica and soda-lime-silica glasses were measured by gas chromatography in the low-pressure region of the physical adsorption isotherms after the adsorbents had been degassed in a dry atmosphere at successively higher temperatures. The isosteric heats of adsorption indicate that after strong degassing treatments each methanol molecule is adsorbed by the formation of a single hydrogen bond with the surface, but after low-temperature degassing more than one hydrogen bond is formed for each adsorbed molecule.     

Adsorption of Methyl Chloride on Molecular Sieves,Silica Gels,and Activated Carbon

Adsorption of methyl chloride (CH₃Cl or MeCl) on five different types of adsorbents was investigated experimentally at increasing pressures and room temperature. Prior to adsorption, all adsorbents were analyzed to assess their physical and chemical characteristics. The experimental data was then used to determine the adsorption isotherms, heats of adsorption, adsorption rates, and their respective theoretical models. The MeCl adsorption capacity was found to reasonably correlate with the adsorbent's surface area. The MeCl adsorption isotherm and adsorption rates were fitted for the first time to a Freundlich isotherm model and pseudo first-/second-order kinetic models, respectively. The range of heat of adsorption indicated a physisorption type of bonding; hence, the investigated adsorbents can potentially be regenerated for cyclic adsorption.     

硅胶行业用耐湿热、耐酸涂料的研制

介绍了以诺夫勒克改性环氧树脂为基料,TDI预聚物为固化剂的涂料。该涂料能够满足高湿热和含酸气体的硅胶生产条件的防腐蚀要求。     

微波下硅胶负载交联壳聚糖的制备及其对Cr~(6+)的吸附

以硅胶为栽体,将壳聚糖负载于其上,辅以交联剂,在微渡条件下进行交联反应,制备出一种新型的吸附树脂.探讨无机基质、交联剂的种类及加入量对吸附性能的影响.结果表明:在以硅胶为基质时,戊二醛为交联剂且加入量为3.0%时,吸附性能最好,对Cr~(6+)的吸附率可达到98.51%.