Separation of organic sulfides from aromatic concentrates by ligand exchange chromatography

Abstract

Alkyl and aryl sulfides were separated from aromatic hydrocarbons by liquid chromatography on a copper-loaded carboxylic cation exchange resin. The sulfides were strongly absorbed from n-pentane solution while the hydrocarbons eluted relatively rapidly and in the order of the increasing number of aromatic rings in the compound. Sulfides were then recovered from the column by backwashing with a mixture of pentane and ethyl ether. All sulfides examined were recovered from the column without loss. The separation method is not limited by the molecular weight range of the sulfides and hydrocarbons tested and therefore may be used to Isolate sulfides from such materials as high-boiling petroleum fractions. Sulfides were isolated by this procedure from petroleum aromatic concentrates that had been prepared by alumina-silica gel chromatography. Mass spectral examination of these sulfide extracts showed the presence of cyclic and aryl sulfides as well as other materials.The problem of separating sulfur compounds from the hydrocarbons and other materials in petroleum has received much attention for many years. An extensive review of separation methods has been presented by Rall et al. (I), including valuations of the quality of the products and the types of materials for which the methods are useful. The purpose of this investigation was the development of a method for isolation of sulfides as a class that would be suitable for petroleum fractions.No separation method has been found to be completely satisfactory for the higher boiling fractions of crude oil. Formation of sulfonium halides by reaction of hydrogen halides with the sulfides has been the most satisfactory method for these materials (1 1. However, separations have been incomplete owing to occlusion of polycyclic aromatic hydrocarbons in the sulfonium halide fraction and excessive solubility of the sulfonium halides in the hydrocarbon fractions. Alkyl aryl sulfides and diary1 sulfides are not separated satisfactorily from aromatic hydrocarbons by the sulfonium halide method.Organic sulfides are known to form adducts with metal cations and many other substances (2-4), particularly those that may be classified as "soft" acids (5, 6). This characteristic has been used for separations by liquid extraction ( I , 7 ) and by liquid-liquid chromatography (8). The chromatographic procedure utilized an aqueous solution of mercury or zinc salts as the stationary phase and an aliphatic hydrocarbon as the mobile phase. Application of this method was limited to the lower molecular weight sulfides, presumably because of insolubility of higher sulfides in aqueous phases. In fact, the sulfides are eluted in the probable order of their solubility in water. This suggests that a chromatographic system that eliminates the water solubility effect may permit a class separation of sulfides without regard to the molecular weight range.Ligand exchange chromatography techniques have been developed to resolve mixtures that present somewhat similar problems (9, I O ) . Most often, this tech...

Aromatic sulfur compounds other than condensed thiophenes in fossil fuels: enrichment and identification

“…Cyclic sulfides, Cj-to C3-dihydrobenzothiophenes, present as major compounds in the P-3 fraction, eluted in the P-3 fraction. Although the retentions of alkylbenzothiophenes are identical with those of alkyldihydrobenzothiophenes in GC, the alkyldihydrobenzothiophenes were isolated and identified in this study, some of which have been previously identified in crude 13 1415 JZ, 19 Figure 9. FPD gas chromatograms of (A) P-2 and (B) P-3 fractions of an SRC-I process solvent.…”

Ligand exchange chromatography of alkyl phenyl sulfides

“…which are responsible for Rf differences observed in different experiments. The (2) ethyl 0.534 0.477 0.600 0.600 (3) n-propyl 0.557 0.503 0.600 0.600 (4) isopropyl 0.545 0.497 0.603 0.600 (5) n-butyl 0.537 0.503 0.600 0.600 (6) ferf-butyl 0.545 0.520 0.603 0.603 (7) sec-butyl 0.545 0.508 0.603 0.603 (8) isobutyl 0.537 0.497 0.600 0.600 (9) In order to determine the effect of electron donation by the sulfur atom on chromatographic behavior of individual alkyl phenyl sulfides the ñM(corr) for Hg2+-chloroform data were plotted against Taft * substituent constants (Figure 1). The negative slope of the straight line Ryi(cozt, , ^ ) = "1-400 * -0.320, (r = 0.994) provides an evidence of an increase in ligand strength of the sulfur atom with an increase in electron donation from alkyl groups in the series of four isomeric butyl phenyl sulfides.…”

Ligand-exchange high-performance liquid chromatography of dialkyl sulfides

“…In the design of an LEG system, the choice of the column packings is one of the most important factors to be considered. Vough and Dooley reported early partial separation of some alkyl and aryl sulfides using a Cu(II) impregnated cationexchange resin column (11), although their system was not efficient. The recent development of high-performance liquid chromatography (HPLC) has led to the production of many types of silica gel based chelating packing materials for LEG, of which nitrogen-containing chelates are most commonly used.…”