Herein disclosed is a reactor comprising a housing; an inlet tube having a section with perforations along its length, wherein the inlet tube section is within the reactor housing; an outlet tube having a section with perforations along its length, wherein the outlet tube section is within the reactor housing; and at least one cylinder made of sintered metal contained within the reactor housing, wherein the sintered metal is catalytically active. In some cases, the sintered metal in the reactor comprises a porous metallic multifunctional (PMM) catalyst. Other reactor designs and the method of use are also described herein.