A method for isobutane alkylation is provided using a fixed-bed catalytic alkylation reactor comprises at least one catalytic flow channel. A feed stream comprising a compound to be alkylated is passed into a flow channel having an alkylation catalyst positioned on at least a portion of the flow channel inner surface in the flow channel downstream region. Olefin is injected into the feed stream at a point beyond a flow channel entrance region whereby the olefin contacts the alkylation catalyst by diffusion to the flow channel inner surface thereby reacting the compound with the olefin and produces an alkylate product.