HIGH-PRESSURE THERMAL-CRACKING OF N-HEXADECANE

Thermal cracking of n-hexadecane was carried out in a tubular flow reactor at 380-450-degrees-C, 13.9 MPa, and residence times ranging from 0.06 to 2.0 h, giving conversions of 1.5-10%. Primary reaction products were C1 to C-14 n-alkanes and C2 to C-15 alpha-olefins, in agreement with a free-radical chain mechanism. Under high-pressure conditions, radical addition to alpha-olefins became significant. Addition of parent hexadecyl radicals to alpha-olefins resulted in the formation of alkyl hexadecanes in the C18 to C31 range. Addition of lower primary alkyl radicals to alpha-olefins gave higher n-alkanes including n-C-15 and n-C-17. Addition of lower secondary alkyl radicals resulted in the formation of C-7 to C-17 branched alkanes. A simple kinetic model based on a free-radical mechanism was developed to account for the observed product distributions and overall n-C-16 conversion.