Citation: LI Fu-chao, ZHANG Jiu-shun, YUAN Qi-min. Mechanism of methane formation in thermal and catalytic cracking of n-octane[J]. Journal of Fuel Chemistry and Technology, ;2014, 42(6): 697-703. shu

Mechanism of methane formation in thermal and catalytic cracking of n-octane

1.
Research Institute of Petroleum Processing, SINOPEC, Beijing 100083, China

Corresponding author: YUAN Qi-min,
Received Date: 15 October 2013
Available Online: 17 February 2014
Fund Project: 国家科技支撑计划(2012BAE05B01)。 (2012BAE05B01)

The thermal and catalytic cracking reactions of n-octane were carried out in a temperature range of 550~650 ℃ with low conversions (x<15%) in a pulse micro-reactor over quartz and ZRP zeolite. Reaction mechanism of methane formation was analyzed. The results showed that ethylene, propylene and n-butylene were primary products and four paths contributed to methane formation in thermal cracking of n-octane. At 600 ℃, dehydrogenation of terminal C-H bond in the chain attacked by methyl radical led to methane production. Due to higher activation energy of cleavage of terminal C-C bond in octyl radical formed via dehydrogenation of central C-C bond, only methane can form at higher temperature. Protolytic cracking was predominant with relatively remarkable yield of normal paraffin in catalytic cracking of n-octane over ZRP zeolite. Methane was produced by protolytic cracking route as well. By comparison of methane formation between thermal and protolytic cracking, it revealed that methane formed through protolytic cracking below 600 ℃ while thermal cracking dominated the selectivity of methane at higher reaction temperatures.
- n-octane,
- thermal cracking,
- catalytic cracking,
- methane,
- reaction path
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