Described is a method for purifying a flow of natural gas, comprising the steps: a) processing a portion of the flow by pyrolysis at a temperature in the range from 1000 C. to 2000 C. to decompose the hydrocarbons comprising at least two carbon atoms into elemental carbon and dihydrogen to obtain a processed flow, b) eliminating the elemental carbon present in the processed flow from step a) to obtain a processed flow without elemental carbon; c) when a) and b) have been carried out on a portion of the natural gas flow, mixing the processed flow without any elemental carbon from step b) with the portion of the non-processed flow; d) obtaining a flow of purified natural gas consisting of either the mixture from step c) or the processed flow without any elemental carbon from step b). The invention also relates to preparing fuel from natural gas purified in this manner.