An internal static mixing system such as a disperser of mesh wire or expanded metal co-knit with a multi filament material selected from inert polymers, catalytic polymers, catalytic metals or mixtures in combination with a vertical reactor having a reaction zone and the disperser disposed in said reaction zone, particularly for carrying out paraffin alkylation using acid catalyst is disclosed. The wire mesh provides the structural integrity of the system as well as the open space required in reactors for the movement of vapors and liquids though the system. The disperser may be in sheets, bundles or bales or positioned within a frame.