Liquid-phase thermal decomposition of hexadecane: reaction mechanisms

Abstract

Thermal decomposition experiments were performed with n -hexadecane to get a better understanding of liquidphase thermal decomposition. Gas chromatography and mass spectrometry were used to identify the decomposition products. At low conversions, liquid-phase thermal decomposition produced low molecular weight straight-chain alkanes and alkenes. This is in good agreement with the Fabuss, Smith, and Satterfield thermal cracking mechanism. At conversions above 5 %, liquid-phase thermal decomposition produced more complex products. High molecular weight branched-chain alkanes were formed in addition to the low molecular weight products described above. The branched-chain alkanes were formed by the reaction of straight-chain alkenes with hexadecyl radicals. A liquid-phase thermal decomposition model was developed that accounts for the main products formed.Research has been undertaken to evaluate the liquidphase thermal decomposition of saturated hydrocarbons. Hexadecane was chosen as a model compound for this research.Considerable work has been reported on the thermal decomposition of saturated hydrocarbons in the gas phase but very little on their liquid-phase decomposition. Rice et al. (1933Rice et al. ( , 1934Rice et al. ( , 1943 showed that the main products of the low-pressure gas-phase thermal decomposition of straight-chain alkanes are low molecular weight straightchain alkanes and alkenes. They developed a free-radical mechanism that accounts for the main products formed. Fabuss, Smith, and Satterfield (1964) modified Rice's mechanism to account for the products formed in highpressure gas-phase decompositions. More recently, Doue and Guiochon (1969) and Hazlett (1977) studied the liquid-phase decomposition of straight-chain alkanes; these workers also reported that only straight-chain products are formed. However, they found more alkanes than alkenes,

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.…”

“…The thermal cracking of aliphatic hydrocarbons involves their conversion into lower molecular weight alkanes and alkenes, and with minor yields of aromatic compounds (Rice, 1931;1933;Voge and Good, 1949;Ford, 1986;Zhou et al, 1987;Bounaceur et al, 2002a) together with branched alkanes of higher molecular weight than the starting alkane. Experimental observations show that the concentration of alkenes decrease with increasing conversion, while the alkanes increase in concentration, especially those with a higher number of carbon atoms than the reactant (Khorasheh and Gray, 1993a;Ford, 1986;Dominé, 1989;Dominé et al, 1990).…”

Effect of temperature on the release of hexadecane from soil by thermal treatment

“…Several studies about the cracking of n-hexadecane have been performed by different authors [19][20][21][22][23][24]. Depeyre et al [20] detected, for operating conditions close to the thermal treatments reported in this work, the following light gases: H 2 , CH 4 , C 2 H 6 , C 2 H 4 , C 3 H 8 , C 3 H 6 , butanes, butadiene, among others.…”

High pressure pyrolysis of n-heptane

“…These authors also modified the free radical mechanism of Rice and Kossiakoff to account for the products formed under high pressure gas-phase pyrolysis [25]. Pyrolysis of several hydrocarbons such as n-hexadecane [26][27][28][29][30][31][32], decalin [28], C 21 -C 27 paraffins [30], dodecane [33], C 9 -C 22 alkanes [34], and pristane, phytane and squalane [35] have been investigated at high pressures. Song et al [36] investigated the condensed-phase pyrolysis of n-tetradecane at elevated pressures.…”