An investigation has been made of the conversion of n-hexane by irradiation in the near-UV and visible region at high temperatures in the presence of a sensitizer - phthalic anhydride. It has been shown that, under the conditions investigated, n-hexane breaks down to form light hydrocarbons enriched with low-molecular weight alkenes - ethylene and propylene. The degree of conversion of n-hexane reaches 60% with an irradiation time of <10 min. The dependences of the yield of the main products of high-temperature photodegradation of n-hexane on the degree of conversion have been established. On the basis of the distribution of photodegradation products, it is suggested that the process has a radical mechanism.