Concentrates, aromatic

Increase in naphthene, olefin, and aromatic concentration, which is indicated by an increase in the refractive index and decreases in aniline point and K factor... 

The first kinetic study appears to have been that of Martinsen148, who found that the sulphonation of 4-nitrotoluene in 99.4-100.54 wt. % sulphuric acid was first-order in aromatic and apparently zeroth-order in sulphur trioxide, the rate being very susceptible to the water concentration. By contrast, Ioffe149 considered the reaction to be first-order in both aromatic and sulphur trioxide, but the experimental data of both workers was inconclusive. The first-order dependence upon aromatic concentration was confirmed by Pinnow150, who determined the equilibrium concentrations of quinol and quinolsulphonic acid after reacting mixtures of these with 40-70 wt. % sulphuric acid at temperatures between 50 and 100 °C the first-order rate coefficients for sulphonation and desulphonation are given in Tables 34 and 35. The logarithms of the rate coefficients for sulphonation... 

Kinetics studies of acid-catalysed chlorination by hypochlorous acid in aqueous acetic acid have been carried out, and the mechanism of the reactions depends upon the strength of the acetic acid an<( the reactivity of the aromatic. Different groups of workers have also obtained different kinetic results. Stanley and Shorter207 studied the chlorination of anisic acid by hypochlorous acid in 70 % aqueous acetic acid at 20 °C, and found the reaction rate to be apparently independent of the hydrogen ion concentration because added perchloric acid and sodium perchlorate of similar molar concentration (below 0.05 M, however) both produced similar and small rate increases. The kinetics were complicated, initial rates being proportional to aromatic concentration up to 0.01 M, but less so thereafter, and described by... 

Kinetic studies have been carried out using the 1 1-complex iodobenzene dichloride as a source of molecular chlorine. In acetic acid solutions, the dissociation of this complex is slower than the rate of halogenation of reactive aromatics such as mesitylene or pentamethylbenzene, consequently the rate of chlorination of these is independent of the aromatic concentration. Thus at 25.2 °C first-order chlorination rate coefficients were obtained, being approximately 0.2 x 10-3 whilst the first-order dissociation rate coefficient was 0.16 xlO-3 from measurements at 25.2 and 45.6 °C the corresponding activation energies... 

The most valuable and comprehensive kinetic studies of alkylation have been carried out by Brown et al. The first of these studies concerned benzylation of aromatics with 3,4-dichloro- and 4-nitro-benzyl chlorides (these being chosen to give convenient reaction rates) with catalysis by aluminium chloride in nitrobenzene solvent340. Reactions were complicated by dialkylation which was especially troublesome at low aromatic concentrations, but it proved possible to obtain approximately third-order kinetics, the process being first-order in halide and catalyst and roughly first-order in aromatic this is shown by the data relating to alkylation of benzene given in Table 77, where the first-order rate coefficients k1 are calculated with respect to the concentration of alkyl chloride and the second-order coefficients k2 are calculated with respect to the products of the... 

Hon (Informing A continuous catalytic reforming process for producing aromatic concentrates and high-octane gasoline. It used a fixed bed of a platinum catalyst. Developed in the 1950s by the Houdiy Process Corporation. 

Often it is called, reasonably enough, benzene concentrate or aromatics concentrate. Benzene concentrate is about 50% benzene, plus some other C5 s, Ce s, and Cys. All of them boil at about 176°F, the boiling point of benzene. Since the boiling temperature of the benzene is so close to that of the other hydrocarbons in the concentrate stream, simple fractionation is not a very effective way of isolating the benzene from benzene concentrate. Instead, one of two processes is used to remove the benzene, solvent extraction process or extractive distillation. The two differ in the primary mechanism they use. One operates on a liquid-liquid basis, the other on a vapor-liquid basis. 

Like the solvent extraction process, extractive distillation relies on the intimate contact of the liquid solvent and the aromatics concentrate vapors to allow the aromatics to be preferentially dissolved in the solvent. The usual list of solvents includes DEG (Diethylene glycol), TEG (Triethylene glycol), NMP (N-methyl pyrrolidone), or methyl formamide. 

The benzene leaves the olefins plant fractionator mixed with the other gasoline components so it is handled the same way as a refinery stream. An aromatics concentrate is made and run through one of the two separation processes you just read about, solvent extraction or extractive distillation. 

Separation of toluene from the other components can be by solvent extraction or extractive distillation, just as described in the benzene chapter. The boiling points of benzene and toluene are far enough apart that the feed to separation unit of choice can be split (fractionated) rather easily into benzene concentrate and a toluene concentrate. Alternatively, the separation unit can be thought of as aromatics recovery unit. Then an aromatics concentrate stream is fed to the solvent extraction unit, and, the aromatics outturn can be split into benzene and toluene streams by fractionation. Both schemes are popular. 

Mussels (Mytilis edulis) exposed to a small spill (approximately 6,000 liters) of fuel oil no. 2 were followed for 86 days post-spill to assess the uptake and retention of the fuel oil components. Alkanes, cycloalkanes, and aromatic concentrations increased significantly in the mussel tissue the 1st day however, by day 5 post-spill, the -alkanes were barely detectable, and by day 21, the concentration of the... 

The photocatalyzed oxidation of gas-phase contaminants in air has been demonstrated for a wide variety of organic compounds, including common aromatics like benzene, toluene, and xylenes. For gas-phase aromatic concentrations in the sub-lOO-ppm range, typical of common air contaminants in enclosed spaces (office buildings, factories, aircraft, and automobiles), photocatalytic treatment leads typically to complete oxidation to CO2 and H2O. This generality of total destruction of aromatic contaminants at ambient temperatures is attractive as a potential air purification and remediation technology. 

However, the photocatalytic reactivity of aromatics, especially benzene, is lower than some of the more promising pollutants for this emerging technology. Also, at aromatic concentrations of as little as 10 ppm, photocatalysts may exhibit apparent deactivation. Here, we summarize achievements to date and discuss methods for increasing aromatic reactivity, minimizing photocatalyst deactivation, and periodically regenerating used protocatalysts. 

Most photocatalytic studies conducted at low aromatic concentrations report no detectable concentrations of gas-phase intermediates [12,17,18]. Traces of intermediates may be present in the gas phase, but at levels below the detection limits of the analytical instruments employed in these studies. There is evidence, however, for either reaction intermediates or reaction by-products on the catalyst surface, even at these low concentrations. Catalyst discoloration, typically a yellowish or brownish color, is often reported following the photocatalytic oxidation of aromatic contaminants at low to moderate gas-phase concentrations [3,4,7,17,52]. These intermediates or reaction by-products may be largely trapped on the catalyst surface by the higher affinity of oxygenated species, like alcohols and aldehydes, for TiO, surfaces when compared to the aromatic parent compounds. 

Mixtures of gaseous or liquid hydrocarbons which can be vaporized represent the raw materials preferable for the industrial production of carbon black. Since aliphatic hydrocarbons give lower yields than aromatic hydrocarbons, the latter are primarily used. The best yields are given by unsubstituted polynuclear compounds with 3-4 rings. Certain fractions of coal tar oils and petrochemical oils from petroleum refinement or the production of ethylene from naphtha (aromatic concentrates and pyrolysis oils) are materials rich in these compounds. These aromatic oils, which are mixtures of a variety of substances, are the most important feedstocks today. Oil on a petrochemical basis is predominant. A typical petrochemical oil consists of 10-15% monocyclic, 50-60% bicyclic, 25-35% tricyclic, and 5-10% tetracyclic aroma tes. 

Reduced Aromatics—Substantial alkylation and isomerization capacity increases would have to accompany any reduction in aromatics content. With limits on aromatics concentration, alkylate and isomerate would be the major tools available for controlling octanes. 

The application of several methods for structural analysis of mineral oils is, in general, limited to those fractions in which no structural elements are present in larger quantities than normally occur in mineral oil fractions. In highly aromatic concentrates, for instance, the normal analytical methods (n-d-M v-n-d) may give inaccurate results, because different types of aromatics may influence the physical constants of the oil differently. 

These formulas, which have been deduced for individual aromatic compounds, are also suitable for the characterization of aromatic mineral oil fractions,aromatic concentrates, etc., provided that only small amounts of tri-aromatics and higher aromatic compounds are present. For sulphur-containing oils the value of Rn should be corrected ... 

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