Process for producing isoparaffin-olefin alkylate having improved octane number

A process for producing alkylate having an improved octane number which comprises:

• a. passing total hydrocarbon reactants comprising isoparaffin and olefin through a static mixing zone and therein subjecting said isoparaffin and olefin to thorough mixing;
• b. introducing the mixture of isoparaffin and olefin after passing through said static mixing zone to a riser-reactor in admixture with HF acid catalyst at liquid phase and reaction conditions to convert at least a substantial portion of isoparaffin and olefin into alkylate;
• c. passing the reaction effluent of step (b) to a first settling zone and allowing the reaction effluent to separate into an upper phase comprising hydrocarbons and a lower phase comprising HF;
• d. passing said upper phase to a fractionation zone and therein subjecting same to distillation conditions to separate said upper phase into a fraction comprising alkylate and a fraction comprising isoparaffin;
• e. withdrawing the isoparaffin fraction from step (d) and refrigerating same to a sufficiently low temperature to allow separation of traces of HF still remaining in the isoparaffin fraction;
• f. passing the refrigerated isoparaffin stream to a second settling zone and allowing same to separate therein into an upper isoparaffin phase and a lower HF phase;
• g. recycling a substantially HF-free isoparaffin stream separated in (f) to said mixing zone;
• and
• h. withdrawing the alkylate separated in step (d) as product, said alkylate having a higher octane value than alkylate produced by the same process, but without step (a).