TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Component: The microchannel reactor comprises process microchannels containing the catalyst, a header providing a flow passageway for fluid to enter the process microchannels, and a footer providing a flow passageway for fluid to leave the process microchannels. Each process microchannel has an entrance; an exit; an elongated section extending between the entrance and the exit; and additional entrance(s) in the elongated section. Reactant(s) enters the process microchannels through the additional entrance(s). The microchannel reactor includes heat exchange channels in thermal contact with the process microchannels. The heat exchange channels comprise microchannels. The process microchannels exchange heat with a heat exchange fluid flowing through the heat exchange channels.Preferred Parameter: Each process microchannel has an internal dimension of width or height of up to 10 mm.    TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Process: The product formed in the conversion process is an intermediate product. The conversion process includes flowing the intermediate product through the microchannel reactor in contact with a combustion catalyst under reaction conditions to form a final product comprising carbon dioxide (CO2) and water (H2O). The reactant composition is preheated prior to the step of flowing the reactant composition. The reactant composition and oxygen or oxygen source are mixed prior to the step of flowing the reactant composition. The heat exchange fluid undergoes a phase change as it flows through the heat exchange channels. The process microchannels are cooled by an endothermic chemical reaction conducted in the heat exchange channels. The endothermic chemical reaction comprises a steam reforming reaction or a dehydrogenation reaction. The reactant composition flows through the process microchannels in a first direction, and a heat exchange fluid flows through the heat exchange channels in a second direction that is cross current, co-current, or counter current relative to the first direction.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Material: The reactant composition includes H2O. The product comprises H2, CO, and CO2. The process microchannels are made silicon, monel, inconel, aluminum (Al), titanium (Ti), nickel (Ni), and/ or copper (Co). The source of oxygen comprises air. A heat exchange fluid flows through the heat exchange channels, the heat exchange fluid comprising air, steam, liquid water, carbon dioxide, gaseous nitrogen, liquid nitrogen, a gaseous hydrocarbon or a liquid hydrocarbon. The fin is made of Al, Ti, Fe, Ni, platinum (Pt), rhodium (Rh), copper (Co), chromium (Cr), or silicon. It can be aluminum oxide, or chromium oxide. The catalyst comprises Rh, Pt, Ni, Cr, Ru, Pd, osmium (Os), iridium and/or their oxide. It is represented by Rh/LaAl11O18 or Rh/LaAlO3. The promoter or stabilizer comprises lanthanum or magnesium.Preferred Catalyst: The support structure has a flow-by configuration, a flow-through configuration, or a serpentine configuration. It has a flow-by configuration with an adjacent gap, a foam configuration with an adjacent gap, a fin structure with gaps, a wash coat on a substrate, or a gauze configuration with a gap for flow. It can be in the form of a fin assembly comprising fin(s) having parallel spaced fins. The fin has an exterior surface and a porous material overlies the exterior surface of the fin, and fibers or protrusions extending from the exterior surface of the fin. The catalyst may be supported by the protrusions. It is wash coated on the exterior surface of the fin, grown on the exterior surface of the fin from solution, or deposited on at least part of the exterior surface of the fin using vapor deposition. The fin assembly comprises spaced fins having a height that is different than the height of the other fins.Preferred Configuration: The fin has a cross section having the shape of square, rectangle, or trapezoid.    TECHNOLOGY FOCUS - METALLURGY - Preferred Material: The process microchannels may be made of steel, brass, and/or alloy of monel, inconel, Al, Ti, Ni, or Co. The catalyst is supported by a support structure of alloy comprising Ni, chromium (Cr), or iron (Fe); or an alloy comprising Fe, Cr, Al, or yttrium (Y). It is the form of particulate solids. The fin can be made of steel, brass or alloy of Al, Ti, Fe, Ni, Pt, Rh, Co, or Cr; an alloy comprising Ni, Cr and Fe; or an alloy comprising Fe, Cr, Al and Y.    TECHNOLOGY FOCUS - POLYMERS - Preferred Material: The process microchannels may be a composite comprising a polymer and fiberglass. The fin can be a polymer, and/or a composite comprising polymer and fiberglass.    TECHNOLOGY FOCUS - CERAMICS AND GLASS - Preferred Material: The process microchannels may be made of quartz. The fin can be made of quartz, ceramics, or glass.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Material: The hydrocarbon reactant includes an aliphatic compound, and/or an aromatic compound; an alkane containing 2-20C/molecule; alkene containing 2-20C; ethane, propane, isopropane, butane, isobutane, a pentane, a hexane, a heptane, an octane, a nonane, and/or a decane; natural gas; ethylene, propylene, 1-butene, 2-butene, isobutylene, 1-pentene, 2-pentene, 3-methyl-1-butene, 2-methyl-2-butene, 1-hexene, 2,3-dimethyl-2butene, 1-heptene, 1-octene, 1-nonene, and/or 1-decene; polyene containing 3-20C; 1,2-propadiene, 1,3-butadiene, 2-methyl-l,3-butadiene, 1,3-pentadiene, 1,4-pentadiene, 1,5-hexadiene, 2,4-hexadiene, and/or 2,3-dimethyl-l,3-butadiene; alkyl or alkylene substituted aromatic compound; toluene, o-xylene, m-xylene, p-xylene, hemimellitene, pseudocumene, mesitylene, prehnitene, isodurene, durene, pentamethylbenzene, hexamethylbenzene, ethylbenzene, n-propylbenzene, cumene, n-butylbenzene, isobutylbenzene, sec-butylbenzene, tert-butylbenzene, p-cymene, and/or styrene; natural oil and/or synthetic oil; distillate fuel; naphtha, diesel fuel, fuel oil, kerosene or gasoline; hydrocarbon derived from a vegetable source, and/or mineral source; hydrocarbon derived from soybean, rapeseed, palm, shale, coal, and/or tar sands; or diluent material.