Olefinic fractions, acid absorption

The saturate and aromatic hydrocarbons were separated from the alcohols by elution chromatography on alumina deactivated with 3.8% water in a ratio of 5 g of alumina to 1 g of oil, by successive elutions with (1) 30 mL of cyclohexane and (2) 50 mL of 2% benzene in cyclohexane. The alcohols were recovered for future analysis by washing the column with 100 mL of ethyl ether. The solvent was removed from the hydrocarbon fraction and the yield of saturates plus aromatics calculated back to the neutral oil. The percentage of olefins was determined by difference. The percentage of aromatic material was determined as the difference between the saturates and aromatics from the hydroboration and the saturates from acid absorption. 

The three fractions resulting from the silica gel chromatography of the shale oil neutral naphtha were examined in detail to provide information regarding the degree of cross-contamination of the various fractions. The saturate s fraction was examined by IR, UV, and proton NMR and showed no aromatic or olefinic contamination, but when subjected to the acid absorption procedure it gave a 3% loss. The lack of any UV, IR, or NMR absorptions owing to aromatic or olefinic materials accompanied by the shrinkage upon acid absorption indicates that the nonsaturate material is probably tetra-substituted olefins. The low concentration, however, may... 

For the selective absorption of Cs-Cg olefins a reactor (2.0 x0.4 cm) containing silica gel impregnated with concentrated sulphuric acid, was used. The adsorbent was prepared by mixing concentrated sulphuric acid and silica gel (fraction of 60-200 mesh) (3 2, w/w). Silica gel is a good filler for sulphuric acid, as it remains friable even on absorption of a larger amount of acid than its own weight. Other supports (cement, refractory brick) were found to be inefficient. The absorbent must be stored in hermetically sealed vessels as the olefins are no longer absorbed quantitatively if the content of water in the sulphuric acid is about 12% or above. 

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