Specificity, hydrocarbon adsorption

To avoid chemisorption problems, an alternative and more universal adsorption method was proposed [89,90], The method is based on the differences in potentials of physical adsorption on the different components. The background of this method is discussed in Problem 8. It advances a CM, and its efficiency was tested on the model mechanical mixtures and PS type of C/SiOz, C/A1203, C/MgO, Si02 + A1203, etc. by adsorption of COz or hydrocarbons. The main requirement of the adsorbate for such measurements is the existence of some specificity of adsorption on different components. 

As far as simple modelling of self-assembly is concerned, the treatment of single component lipid molecules given here has probably been pushed as far as it can. The refinement of our theory of self-assembly requires a proper examination of Stern layers, consequences of deviations from liquid-like properties of hydrocarbon chains, head group steric elfects, specific ion adsorption and other effects. While such a more rigorous analysis would undoubtedly provide specific insights into the properties of particular molecules, it is doubtful if a more refined theory will provide a better overview. 

Specific retention volume Vm (cm /g) and differential heat of adsorption Qa (kj/mol) for hydrocarbons adsorption on natural palygorskite, and natural and tetramethylammonium -modified montmorillonite at 150°C... 

Specific retention volumes Vj (cm /m ) and differential heats Qa (kj/mol) of hydrocarbons adsorption on cetylammonium montmorillonite with different amounts of presorbed modifier a (meq/g) at 150°C... 

Some specific factors should be considered when using zeolites as catalysts in isobutane/olefin alkylation. The first is the strong hydrocarbon adsorption of zeolites, especially at low temperatures, which makes the actual concentration of the reactants in the zeolite quite high. In addition, and due to the high concentration of acid sites in the zeolite cavities, zeolite would behave as a liquid-acid catalyst but with a high solubility of reactants. Taking this into account it can be easily assumed that the Si/Al ratio can determine the nature of reaction products. In this way, it has been proposed that zeolites... 

Most chemical and reaction path models currently account only for the aqueous carboxylic acids and their cation complexes, amino acids, some liquid hydrocarbons, alcohols, and certain other compounds entered into the data base for project-specific purposes. Adsorption of trace metals onto solid humic substances, for example, requires the user to create a fictitious solid and use an empirical adsorption coefficient. Scattered reports of carboxylic acid solids such as calcium oxalate (Marlowe 1970 Naumov et al. 1971 Galimov et al. 1975 Graustein et al. 1977 Campbell and Roberts 1986) emphasize the necessity to perform sensitivity analyses on the formation of such solids and indicate another area of uncertainty in the interpretation of chemical and reaction path model results. 

Adsorption at surfaces. There are two kinds of adsorption, the indiscriminate and the specific. Indiscriminate adsorption is shown by amphiphilic substances, i.e. those having a water-attracting end-group attached to a comparatively large residue that has little affinity for water. Ordinary soap is an example of this class of substances. It will be recalled that water molecules are extensively hydrogen-bonded to one another and that substances dissolve in water only by virtue of their ability to break some of these bonds and form new bonds with water molecules. Amphiphilic molecules, dissolved in water, are in a state of imeasy equilibrium, because the hydrocarbon portion is constantly being squeezed out by the water molecules in their endeavour to unite with one another. 

The following are some of the typical industrial applications for liquid-phase carbon adsorption. Generally liquid-phase carbon adsorbents are used to decolorize or purify liquids, solutions, and liquefiable materials such as waxes. Specific industrial applications include the decolorization of sugar syrups the removal of sulfurous, phenolic, and hydrocarbon contaminants from wastewater the purification of various aqueous solutions of acids, alkalies, amines, glycols, salts, gelatin, vinegar, fruit juices, pectin, glycerol, and alcoholic spirits dechlorination the removal of... 

The adsorption of aliphatic alcohols, which adsorb on metals with the hydrocarbon tail facing the electrode surface, shows different patterns on real Ag crystal faces440,441 with respect to quasi-perfect single-crystal face electrodes.442-444 This specific point will be discussed in detail in Section III. 

The second part of the book covers zeolite adsorptive separation, adsorption mechanisms, zeolite membranes and mixed matrix membranes in Chapters 5-11. Chapter 5 summarizes the literature and reports adsorptive separation work on specific separation applications organized around the types of molecular species being separated. A series of tables provide groupings for (i) aromatics and derivatives, (ii) non-aromatic hydrocarbons, (iii) carbohydrates and organic acids, (iv) fine chemical and pharmaceuticals, (v) trace impurities removed from bulk materials. Zeolite adsorptive separation mechanisms are theorized in Chapter 6. 

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