In this work we report the production of carbon nanotubes by direct vapourization of graphite targets containing different couples of catalysts using a 2 kW solar furnace. With this small-scale experimental set-up we observed the evolution of the structure of the produced nanotubes with experimental conditions, pressure and flow rate of the inert gas (argon) and target composition. High pressure favours the production of bundles of single-wall nanotubes (SWNTs) and the purity of the produced material depends on the target temperature and the cooling rate of the vapour. We also discuss the influence of the target composition.