Production of C 9 aromatic hydrocarbons by catalytic reforming of gasoline fractions

Abstract

AROMATIC hydrocarbons containing nine C atoms in the molecule are increasingly used in organic synthesis industry [1-4]. Thus, oxidation of pseudocumene produces trimellitic anhydride and 2,4and 2,5-dimethylbenzoic acids. Trimesic acid is prepared from mesitylene. Pseudocumene is also used for the synthesis of durene (1,2,4,5-tetramethylbenzene), by the oxidation of which pyromellitic acid and its dianhydride are obtained. These acids and their anhydrides are used in the production of synthetic materials and for obtaining many other" valuable chemical products. I t should also be mentioned that ethyl toluene isomers can be used for obtaining vinyltoluene [5]. The production of C 9 aromatic hydrocarbons and pseudocumene and mesitylene, in particular, is based on the isolation of these hydrocarbons from catalytically reformed gasolines [1, 5]. From the investigations carried out by several authors [1-7, 9, 10] the isomeric composition of C 9 aromatic hydrocarbon mixtures contained in gasolines from catalytic reforming, was determined. Data of various authors are shown in Table 1. The pseudoeumene and m-ethyltoluene contents of the mixture are the lfighest. Eby and Newman [5] consider that in a conventional petroleum refinery four times more pseudoeumene than benzene can be obtained, while in Grigorescu's report [11] it is pointed out that 3% pseudocumene is contained in the product of catalytic reforming. These studies, however, do not indicate which gasoline fractions should be subjected to catalytic reforming so that the highest C9 aromatic hydrocarbon yield can be obtained. Sufficiently definite information is not available on the problem whether C 9 aromatic hydrocarbon composition is maintained or changed during catalytic reforming of various gasoline fractions. This problem should also be studied as it is well known that the relative quantities of ethylbenzene and xylenes in reforming catalysates depend on the nature of the gasoline fraction used as raw material for the process [12]. Methods of operation. Narrow fractions boiling within the ranges of 130-140, 140-150, 150-165, 165-180 and 180-185 ° were isolated from straight run