Production of lower alkenes and light fuels by gas phase oxidative cracking of heavy hydrocarbons

The gas phase oxidative cracking (GOC) and non-oxidative pyrolysis of heavy hydrocarbons were investigated, with decalin (decahydronaphthalene) and tetralin (tetrahydronaphthalene) as the model compounds for naphthenic hydrocarbon and aromatic hydrocarbon, respectively. Unlike pyrolysis, the ring rupture of decalin or tetralin molecule and the decoking ability of system were significantly enhanced due to the introduction of O₂ in GOC. For GOC of decalin, both the lower alkenes and the light fuels were obtained. At lower temperatures the light fuels mainly contained alkyl benzene, alkyl cyclohexane and isoparaffins, while it was rich in BTX (benzene, toluene and xylenes) at higher temperatures. A 38.9% yield of lower alkenes and 48.0% yield of light fuels (BTX mass content: 59.9%) at 100% decalin conversion were obtained under the conditions of 800 °C and decalin / O₂ = 0.5. For GOC of tetralin, both the dehydrogenation and the cracking reactions dominated the reaction routes, resulting in a high mass content of alkyl naphthalene and alkyl benzene in the light fuels. The estimation of O₂ distribution in the products demonstrated that O₂ participated primarily in the oxydehydrogenation reactions at low temperatures, while mainly in the partial oxidation reactions at high temperatures to produce CO_x (x = 1, 2).