Aromatic hydrocarbons solvent power

Figure 2.3 Solvent power aromatic hydrocarbon solvents.

There are several criteria used to define solvent power. Chemical analysis is ideal because it can indicate the proportion of hydrocarbons known to be good solvents in particular, the aromatics. 

Lube oil extraction plants often use phenol as solvent. Phenol is used because of its solvent power with a wide range of feed stocks and its ease of recovery. Phenol preferentially dissolves aromatic-type hydrocarbons from the feed stock and improves its oxidation stability and to some extent its color. Phenol extraction can be used over the entire viscosity range of lube distillates and deasphalted oils. The phenol solvent extraction separation is primarily by molecular type or composition. In order to accomplish a separation by solvent extraction, it is necessary that two liquid phases be present. In phenol solvent extraction of lubricating oils these two phases are an oil-rich phase and a phenol-rich phase. Tne oil-rich phase or raffinate solution consists of the "treated" oil from which undesirable naphthenic and aromatic components have been removed plus some dissolved phenol. The phenol-rich phase or extract solution consists mainly of the bulk of the phenol plus the undesirable components removed from the oil feed. The oil materials remaining... 

Liquid solvents are used to extract either desirable or undesirable compounds from a liquid mixture. Solvent extraction processes use a liquid solvent that has a high solvolytic power for certain compounds in the feed mixture. For example, ethylene glycol has a greater affinity for aromatic hydrocarbons and extracts them preferentially from a reformate mixture (a liquid paraffinic and aromatic product from catalytic reforming). The raffinate, which is mainly paraffins, is freed from traces of ethylene glycol by distillation. Other solvents that could be used for this purpose are liquid sulfur dioxide and sulfolane (tetramethylene sulfone). 

The physical properties of many macrocyclic polyethers and their salt complexes have been already described. - Dibenzo-18-crown-6 polyether is useful for the preparation of sharpmelting salt complexes. Dicyclohexyl-18-crown-6 polyether has the convenient property of solubilizing sodium and potassium salts in aprotic solvents, as exemplified by the formation of a toluene solution of the potassium hydroxide complex (Note 13). Crystals of potassium permanganate, potassium Lbutoxide, and potassium palladium(II) tetrachloride (PdClj + KCl) can be made to dissolve in liquid aromatic hydrocarbons merely by adding dicyclohexyl-18-crown-6 polyether. The solubilizing power of the saturated macrocyclic polyethers permits ionic reactions to occur in aprotic media. It is expected that this [)ropcrty will find practical use in catalysis, enhancement of... 

Organic contaminants. The concentration of polynuclear aromatic hydrocarbons (PAH) in the particulate phase of flue gases of oil-shale-combusting thermal power plants has been estimated to range from 0.04 to 3.16 mg/m3 (Aunela et al. 1995). The solvent-extractable fraction (<1.5 wt%) from fly ash particles collected from Narva power plant smog chambers included several PAHs (phenanthrene,... 

KAURI-BUTANOL VALUE. A measure of the aromatic content and hence the solvent power of a hydrocarbon liquid Kauri gum is readily soluble in butanol but insoluble in hydrocarbons. The kb value is Ihe measure of the volume of solvent required to produce turbidity in a standard solution containing kauri gum dissolved in butanol. Naphtha fractions have a kb value of about 30. and toluene about 105. 

Rubbers are plasticized with petroleum oils, before vulcanization, to improve processability and adhesion of rubber layers to each other and to reduce the cost and increase the softness of the final product. Large quantities of these oil-extended rubbers are used in tire compounds and related products. The oil content is frequently about 50 wt% of the styrene-butadiene rubber. The chemical composition of the extender oil is important. Saturated hydrocarbons have limited compatibility with most rubbers and may sweat-out. Aromatic oils are more compatible and unsaturated straight chain and cyclic compounds are intermediate in solvent power. 

Apart from the generalised solvating power of the medium, there exist more specific interactions between solvent and other components of a polymerisation system vriiich must sometimes be taken into account. We have already mentioned examples of catalyst-solvent interactions of a detrimental nature. In other situations the solvent can play a cocatalytic role, or have peculiar beneficial properties, as in the case of liquid SO2, a compound of modest polarity (e = 12.4 at 22 °C), but very conductive towards cationic polymerisation and related reactions The active species can also give specific reactions with some solvents, as in the case of aromatic hydrocarbons which can suffer Friedel-Crafts alkylations under certain conditions. These transfer and termination reactions are however outside the scope of the present work. 

Effect of Tertiary Amines.—Though the influence of ethereal solvents and additives in anionic polymerizations has been widely investigated, it is only relatively recently that attention has been focussed on the effect of tertiary amines. The complex between Bu"Li and tetramethylethylene diamine (TMEDA) is known to be a powerful base readily capable, for example, of abstracting a proton from aromatic hydrocarbons and generating lithiated derivatives. Not surprisingly, therefore, tertiary amines do indeed have significant effects in carboanionic propagations. 

Liquid deuterium bromide has proved a solvent well suited for isotope exchange and it is also a powerful deuteron-donor.106 The hydrogen of polycyclic aromatic hydrocarbons is rapidly exchanged at 20° the hydrogen of... 

Short oil alkyd resins require special solvent mixtures for each area of use. Principal solvents include aromatic hydrocarbons (e.g., xylene), solvent naphtha fractions, and glycol ethers. Lower alcohols, even in small amounts, have a powerful viscositylowering effect. The choice of solvent depends on the solvent power for the resins and the application method. The last solvent to evaporate during drying must be a true solvent for the binders because otherwise the paint film becomes opaque or inhomogeneous. 

Sodium hydroxide, tin(II) chloride and iron(II) sulphate can all destroy dioxane peroxides, but to avoid boiling to dryness in recovery, a heel of hydrocarbon should be considered to keep the peroxides in solution at the end of a distillation. Cg or Cg aromatic hydrocarbons which do not azeotrope with dioxane and have a fairly good solvent power might be suitable for this duty. Dioxane is very hygroscopic. 

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