Alkylation of Isobutane with C₃−C₄ Olefins:  Identification and Chemistry of Heavy-End Production

The chemistry of the production of C 10 −C 16 isoparaffins during the alkylation of isobutane has been significantly clarified based on the new analytical information obtained in this investigation. These heavy isoparaffins are produced when isobutane is alkylated with C 3 −C 4 olefins using either sulfuric acid or HF as the catalyst: at least 14 families of isomers are present in this heavy-end fraction, and many C 10 −C 12 isoparaffins present in larger quantities have now been identified. This new information also permits better evaluation of process conditions for alkylation and improved calculation of yields. Since 10−16 wt % of industrial alkylates often are C 10 −C 16 isoparaffins, these heavier isoparaffins often have a significant effect on alkylate quality (or octane number) when they are left in motor fuels. To obtain this new analytical evidence, seven alkylates produced using different olefins and/or different acid catalysts were analyzed using a gas chromatographic unit, and the results were compared. In addition, mass spectrometric results and the normal boiling points of C 10 −C 12 isoparaffins were employed.