A pyrolysis process and reactor converts various hydrocarbons such as waste materials, for example, scrap polymers, tires, etc., into various chemical components or amounts thereof, not otherwise produced by conventional pyrolytic processes. A large reactor size is utilized in association with a low heat input per unit weight of charge. A thick pyrolyzate/"char" layer is formed during pyrolysis. The product or various components thereof can be utilized as a fuel or octane additive.