The present invention includes a process for producing carbon filaments and synthesis gas from a mixture of alkanes, preferably natural gas, comprising converting a first portion of the alkanes, preferably C.sub.2.sup.+ hydrocarbons, directly to carbon filaments and converting a second portion of the alkanes, preferably methane, to syngas. The natural gas may be separated into a first feed stream comprising ethane, propane, and butane and a second feed stream comprising methane. The first feed stream is fed to a carbon filament CF reactor to produce carbon filaments and hydrogen. The second feed stream is fed to a syngas production reactor to produce syngas. Alternatively, the natural gas is fed to at least one carbon filament reactor that is maintained at an effective temperature to convert C.sub.2.sup.+ hydrocarbons in the natural gas to carbon filaments and hydrogen, thereby filtering methane from the natural gas.