Adsorption Cyclohexane, Methanol

The surface areas of the various specimens estimated by applying the Brunauer, Emmett, and Teller equation (4) to the initial adsorption isotherms and using the value of 18 sq. A. (14) are compared with the surface areas calculated from the adsorption of cyclohexane in Table I. The surface areas calculated from the total adsorption of methanol on lepidocrocite as well as its products formed by... 

Silicalite is a microporous crystalline silica that has received attention in both gaseous and liquid applications. The hydrophobic nature of silicalite has led to its use in the adsorption of ethanol from dilute aqueous solutions (Oulman and Chriswell, 1982 Milestone and Bibby, 1981 Bui et al., 1985). The adsorption of methanol, ethanol, acetone, toluene, and cyclohexane in silicalite crystals has also been investigated. 

Adsorption phenomena from solutions onto sohd surfaces have been one of the important subjects in colloid and surface chemistry. Sophisticated application of adsorption has been demonstrated recently in the formation of self-assembhng monolayers and multilayers on various substrates [4,7], However, only a limited number of researchers have been devoted to the study of adsorption in binary hquid systems. The adsorption isotherm and colloidal stabihty measmement have been the main tools for these studies. The molecular level of characterization is needed to elucidate the phenomenon. We have employed the combination of smface forces measmement and Fomier transform infrared spectroscopy in attenuated total reflection (FTIR-ATR) to study the preferential (selective) adsorption of alcohol (methanol, ethanol, and propanol) onto glass surfaces from their binary mixtures with cyclohexane. Om studies have demonstrated the cluster formation of alcohol adsorbed on the surfaces and the long-range attraction associated with such adsorption. We may call these clusters macroclusters, because the thickness of the adsorbed alcohol layer is about 15 mn, which is quite large compared to the size of the alcohol. The following describes the results for the ethanol-cycohexane mixtures [10],... 

We then designed model studies by adsorbing cinchonidine from CCU solution onto a polycrystalline platinum disk, and then rinsing the platinum surface with a solvent. The fate of the adsorbed cinchonidine was monitored by reflection-absorption infrared spectroscopy (RAIRS) that probes the adsorbed cinchonidine on the surface. By trying 54 different solvents, we are able to identify two broad trends (Figure 17) [66]. For the first trend, the cinchonidine initially adsorbed at the CCR-Pt interface is not easily removed by the second solvent such as cyclohexane, n-pentane, n-hexane, carbon tetrachloride, carbon disulfide, toluene, benzene, ethyl ether, chlorobenzene, and formamide. For the second trend, the initially established adsorption-desorption equilibrium at the CCR-Pt interface is obviously perturbed by flushing the system with another solvent such as dichloromethane, ethyl acetate, methanol, ethanol, and acetic acid. These trends can already explain the above-mentioned observations made by catalysis researchers, in the sense that the perturbation of initially established adsorption-desorption equilibrium is related to the nature of the solvent. 

Preparative fractionation of PS with pyrene or OH endgroups was conducted on a silica column (350 x50 mm d0 = 6nm dP 100 pm). The eluent was benzene-cyclohexane (70 30) or chloroform with stepwise increased methanol content (0.01 to 2 %). The fractions obtained formed a series decreasing in molar mass. This might have been due to size exclusion although the column possessed adsorption activity. 

Saturated and aromatic hydrocarbons were separated from the acid-, base-, and neutral nitrogen-free bitumen by adsorption chromatography using silica gel, grade 12, as the adsorbent and cyclohexane as the eluting solvent. The column was dry packed, and the cutpoint was made at two void volumes. At the cut points, the UV absorbance was measured at 270 nm to determine the overlap of aromatics in the saturates. Aromatics were desorbed with 60% benzene-40 % methanol. 

The object of the present investigation was to study the adsorption of cyclohexane and methanol vapors on ferric hydroxide in the form of synthetic lepido-crocite and goethite, and on the oxides prepared in vacuo by their thermal decomposition at different temperatures and for varying lengths of time. 

Apparatus. The adsorption of cyclohexane and methanol vapors was measured with the aid of a simple volumetric apparatus similar to that described earlier (19). 

Table I. Surface Areas Calculated from the Adsorption of Cyclohexane and of Methanol...

A similar technique has been used to determine the acidic character of niobium oxide and niobyl phosphate catalysts in different solvents (decane, cyclohexane, toluene, methanol and isopropanol) using aniline and 2-phenyl-ethylamine as probe molecules [27, 28]. The heat evolved from the adsorption reaction derives from two different contributions the exothermic enthalpy of adsorption and the endothermic enthalpy of displacement of the solvent, while the enthalpy effects describing dilution and mixing phenomena can be neglected owing to the differential design and pre-heating of the probe solution. 

The well characterized and stable surface phases observed on the Sn-Pt(l 11) have provided researchers in the chemisorption and catalysis field with a substrate of great interest for studying the properties of bimetallic interfaces. Simple probe gases such as CO have been studied after adsorption on this system [45] as well as a variety of organic molecules such as acetylene [46], cyclohexane and benzene [47, 48], butane and isobutane [49], methanol, ethanol and water [50]. Several surface reactions of the above gases were also studied. 

Although nitrogen has been most often used to study the energetic heterogeneity of silica [113,114,163,168-172], other adsorbates such as argon [169], benzene [113], cyclohexane and cyclohexene [138,141,142,146,173-175], n-hexane and n-hexene [135,137], n-heptane [134], chlorinated hydrocarbons [132,134,175,176], diethyl ether [132,134], methanol [132,134], ethanol [134] and pyridine [134] were nsed to probe various types of adsorption sites on the silica surface. 

FTIR photoacoustic spectroscopy was used for the study of the adsorption of poly(n-butyl methacrylate) from cyclohexane, benzene and carbon tetrachloride onto alumina. The efficiency of adsorption increased in the order cyclohexane, carbon tetrachloride, benzene, while methanol and tetrahydrofuran showed negative adsorption. Poly(n-butyl methacrylate) had a negative temperature coefficient of adsorption (126). 

Alumina Silicic acid Magnesium sulfate Cellulose paper 1 Increasing adsorption of polar materials Water t Methanol Ethanol Acetone Ethyl acetate Diethyl ether Methylene chloride Cyclohexane Pentane 1 Increasing solvation of polar materials... 

The two sets of activated charcoals studied here, were already characterized by gas adsorption (8) and immersion microcalorimetry into pure liquids (methanol, benzene, cyclohexane, n-hexane and a-pinene) (9). The main results from nitrogen adsorption are summarized in Table I. 

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