Abstract: An apparatus for converting heavy hydrocarbons to light hydrocarbons includes an inlet capable of supplying a pre-foaming mixture comprising a hydrocarbon to be processed and a processing gas, wherein the processing gas is dissolved in the hydrocarbon to be processed; a foam generator configured to receive the pre-foaming mixture at a first pressure, compress the pre-foaming mixture to a second pressure that is higher than the first pressure by routing it through a nozzle; and generate a foam by allowing the pre-foaming mixture at the second pressure to expand in a chamber at a third pressure that is lower than the first or second pressures; a plasma reactor, wherein the plasma reactor is capable of receiving the foam and comprises at least one pair of spark gap electrodes capable of subjecting the foam to a plasma discharge to yield a processed mixture; and an outlet capable of receiving the processed mixture.