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

The chemistry of the production of C10−C16 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 C3−C4 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 C10−C12 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 C10−C16 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. ...