Alkylation of isobutane with C-3-C-4 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.