Alkylnaphthalene concentrate

The C10-C13 or alkylnaphthalene concentrate fraction boiling from 400° =-550°F contains principally bicyclic aromatics of the naphthalene series. Also present are methylindene and higher indenes plus biphenyls, higher alkylstyrenes, and alkylbenzenes. Nonaromatics are present in low concentrations. 

Case 04 (Figure 4) adds hydrodealkylation of both toluene and the alkylnaphthalene concentrate fraction. To produce the necessary hydrogen as well as to increase BTX production catalytic reforming of all naphtha in the crude is added. Case 04 represents a relatively complete development of the all-chemical configuration of the petrochemical refinery. 

Determination of degradation by measurement of loss may be ambiguous since this fails to take into account transformation to metabolites. At field sites, loss by other processes such as volatilization is difficult to assess, but may be inferred, for example, from low concentrations of the more volatile alkylnaphthalenes. The use of stable isotopes is discussed in Chapter 13. 

There are indications that pure naphthalene (a constituent of mothballs, which are, by definition, toxic to moths) and alkylnaphthalenes are from three to 10 times more toxic to test animals than are benzene and alkylbenzenes. In addition, and because of the low water solubility of tricyclic and polycyclic (polynuclear) aromatic hydrocarbons (i.e., those aromatic hydrocarbons heavier than naphthalene), these compounds are generally present at very low concentrations in the water-soluble fraction of oil. Therefore, the results of this smdy and others conclude that the soluble aromatics of crude oil (such as benzene, toluene, ethylbenzene, xylenes, and naphthalenes) produce the majority of its toxic effects in the enviromnent. 

Studies of Lewis acid-catalyzed isomerization of alkylnaphthalenes were carried out by Olah and Olah in connection with alkylation of naphthalene with alkyl halides.88 Methyl-, ethyl-, isopropyl- and ferf-butylnaphthalene readily undergo isomerization with A1C13 in CS2 solution. The rate of isomerization and the equilibrium concentration of the p isomer were found to increase with increasing branching of the alkyl substituent (Table 4.3). 

Surfactant solubilization in liquid cleaners may be limited due to a high concentration of the surfactant or a high amount of electrolytes present in the formulations. In order to enhance the solubility and to increase the cloud point for nonionic-based systems, hydrotropes are often added. This phenomenon has already been pointed out in Section 3.5 above, where the cloud points of solutions with nonionic surfactants were elevated upon the addition of alkyl polyglucosides (16). Hydrotropic activity can be evaluated by determining the amount of hydrotrope required to clarify a cloudy solution or the cloud point elevation obtained for a specific concentration of a hydrotrope. The efficacy of hydrotropes varies for different classes of compounds. This has been observed for short-chain alkylbenzene and alkylnaph-thalene sulfonates when added to a number of detergent formulations (21). The alkylnaphthalene sulfonates were found to be more efficient than the alkylbenzene sulfonates in elevating the cloud point. 

In other petroleum-derived naphthalene feedstocks of lower aromaticity, such as reforming residues and cat-cracker recycling oils, there is, as a result of their lower aromaticity, a higher proportion of alkylnaphthalenes thus the naphthalene content is not sufficient for direct recovery in an economic manner. Dealkylation processes must therefore be used to increase the concentration of naphthalene. 

In the first process stage, the naphthalene homologs are further concentrated in a pre-column. Dealkylation of alkylnaphthalenes takes place at 35 bar and at a temperature of 540 to 620 °C. The molar ratio of hydrogen to feedstock material is around 4-10 1. The conversion is restricted to about 60%, in order to limit the hydrogenation of naphthalene. 

Alkylbenzenes and alkylnaphthalenes were studied on a silica colunui using hexane, hexane/1-chlorobutane, hexane/l-bromobutane, or hexane/IPA as the mobile phase [619]. Modifier levels ranged fiom 0.005% to 10%. Capacity fiictors versus carbon number were plotted for each solvent mixture. Selectivity decreased for all solvent modifiers except 1-chlorobutane, for which selectivity increased as the level increased from 2% to 8%. The authors attribute diis to the formation of n-complexes between the 1-chlorobutane and the PAH solutes. Selectivity decreased, as expected, for the alkylnaphthalenes when I-bromobutane was used. Selectivity was lost rapidly as the level of IPA increased from 0.01%0.05% indicating that at low IPA concentrations IPA (or the water contained in the IPA) readily modifies or deactivates the silica support. 

---