NOVELTY - A carbon-nanotube production apparatus has conversion reactor (B), separator, carbon-nanotube production unit (G), and recycling unit. The reactor converts hydrocarbon (3) and carbon dioxide into converted gas stream comprising hydrogen, carbon monoxide, unreacted carbon dioxide, and unreacted hydrocarbon. The separator separates hydrogen and unreacted hydrocarbon from the converted stream to form principal stream (7) and by-product stream (9). The carbon-nanotube production unit produces carbon nanotubes and a waste carbon-dioxide stream.    USE - Apparatus is used for producing carbon nanotubes, such as single-walled carbon nanotubes, multi-walled carbon nanotubes, and carbon nanofibers.    ADVANTAGE - The apparatus allows carbon monoxide to be produced on an as-needed basis, negating the need to transport carbon monoxide to the production site or store large quantities of carbon monoxide on-site. Carbon-dioxide emission is eliminated by recycling the carbon-dioxide by-product and mixing it with the feed to the partial oxidation process. The permeated waste gas stream may contain majority of hydrogen and can be exported as fuel.    DETAILED DESCRIPTION - A carbon-nanotube production apparatus comprises a conversion reactor, a separator in fluid communication with the conversion reactor, a carbon-nanotube production unit in fluid communication with the separator, and a recycling unit. The reactor converts a mixture of hydrocarbon and carbon dioxide into a converted gas stream comprising hydrogen, carbon monoxide, unreacted carbon dioxide, and unreacted hydrocarbon. The separator separates hydrogen and unreacted hydrocarbon from the converted gas stream to form a principal stream comprising carbon monoxide and unreacted carbon dioxide, and a by-product stream comprising hydrogen and unreacted hydrocarbon. The carbon-nanotube production unit produces carbon nanotubes and a waste stream of carbon dioxide. The recycling unit recycles the waste stream from the carbon-nanotube production unit to the conversion reactor.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the apparatus used for producing carbon nanotubes.    Hydrocarbon (3)    Principal stream (7)    By-product stream (9)    Conversion reactor (B)    Carbon-nanotube production unit (G)