Methods of preparing single walled carbon nanotubes are provided. Carbon containing gas is contacted with a supported metal catalyst under reaction conditions to yield at least 90% single walled carbon nanotubes and at least 1 gram single walled carbon nanotubes/gram metal catalyst. The support material may be calcined at temperatures between 150 and 600° C., and may have at least one oxidized planar surface. Reaction conditions include less than 10 atmospheres pressure and less than 800° C.