Comparison of Liquid-Phase and Gas-Phase Pure Thermal Cracking of n-Hexadecane

Abstract

Thermal cracking of n-hexadecane in the mild temperature (330−375 °C) range has been investigated in liquid and gas phases. The kinetic data of liquid-phase cracking are shown to be very similar to those of gas-phase cracking. However, the pattern and distribution of the products are greatly phase dependent. In liquid-phase cracking, there is an equimolar distribution of n-alkane and 1-alkene products in the C3−C13 range at low conversion; when the conversion is increased, more alkanes than alkenes are produced. To the contrary, more alkenes than alkanes are always determined in products from gas-phase cracking. Liquid-phase cracking gives a low selectivity of gas products and a high selectivity of addition compounds (C18−C30), whereas gas-phase cracking produces a large amount of gas products and no addition compounds. The phase dependence of products can be interpreted in terms of a low concentration of hexadecane, under which β-scission occurs more preferentially than in liquid phase. Reaction mechanisms are suggested based on the product analysis to account for cracking behaviors of liquid-phase and gas-phase cracking.

Retardation of oil cracking to gas and pressure induced combination reactions to account for viscous oil in deep petroleum basins: Evidence from oil and n-hexadecane pyrolysis at water pressures up to 900 bar

“…For n-hexadecane, the product distribution from the non-hydrous (20 bar) pyrolysis (Figures 4a and 4b) was entirely consistent with previous studies using similar conditions (Ford, 1986;Wu et al, 1996), with the lower molecular weight (˂C 14 )…”

“…Ford (1986) and Wu et al (1996) concluded that the C 18 -C 31 straight and branched chain alkanes were formed by alkylation reactions between lower molecular weight (˂C 14 ) alkenes and C 16 radicals. Under normal pressure (175 bar) hydrous conditions (Figures 4a and 4b), the concentration of ˂C 14 alkenes decreased and the formation of C 18 -C 31 alkanes was completely suppressed.…”

Distribution Kinetics of Plastics Decomposition

“…In light hydrocarbon cracking, addition products are observed by GC upon liquid-phase cracking rather than gas-phase cracking 36) . Radical addition of polymer will yield MWDs shifted to higher MWs.…”

HDPE liquefaction: Random chain scission model

“…Model compound studies have shown the existence of trace levels of such side reactions. 18 We have not incorporated a specific step for scission at chain branch sites (tertiary carbons). This step would be based on measurement of tertiary carbons in the polymer, possibly by nuclear magnetic resonance (NMR) characterization.…”

“…Degradation rates for light model compounds (MW Ͻ 300) show that gas phase reactions can have significant impact. 18 As time increases, the proportion of the gas phase increases as more volatiles are formed. Using b ϭ 0.85 and molecular weight of 226 (hexadecane), the rate constant was calculated to be 2.4*10 Ϫ4 s…”