Acta Phys. -Chim. Sin. ›› 2013, Vol. 29 ›› Issue (04): 689-694.doi: 10.3866/PKU.WHXB201302061

• THERMODYNAMICS, KINETICS, AND STRUCTURAL CHEMISTRY • Previous Articles     Next Articles

Pyrolysis of n-Decane and Dimethylbenzene under Supercritical Pressure

ZHOU Hao1, MAO Jia1, WANG Bi-Yao1, ZHU Quan1, WANG Jian-Li2, LI Xiang-Yuan1   

  1. 1 Colledge of Chemical Engineering, Sichuan University, Chengdu 610065, P.R. China;
    2 Colledge of Chemistry, Sichuan University, Chengdu 610064, P.R. China
  • Received:2012-11-15 Revised:2013-02-05 Published:2013-03-25
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (91116001/A0204).

Abstract:

The pyrolysis of n-decane and dimethylbenzene under supercritical pressure was studied using a continuous flow reactor. Samples were heated to a temperature of 650, 700, or 750 ℃ under a pressure of 4 MPa without oxygen. n-Decane pyrolyzed more easily than dimethylbenzene. We analyzed gaseous products by online gas chromatography, and liquid products by gas chromatography-mass spectrometry, allowing us to calculate the cracking gas yield and cracking conversion of these systems. A quantum chemistry computation was used to evaluate the binding energies of C-C and C-H bonds in n-decane and dimethylbenzene. Both experimental and theoretical results were also used to analyze the cracking reactivity of these species. Analysis of the components in the products indicated that the main products of n-decane were C1-C3 hydrocarbons and hydrogen, whereas ethylbenzene, toluene and other aromatic compounds were the main products of dimethylbezene after pyrolysis. Binding energy calculations showed that both C-C and C-H bonds in n-decane possessed lower binding energies than those in dimethylbezene, and a C-C bond was the weakest. In dimethylbenzene, a C-H bond in the methyl groups was the weakest, and its binding energy was much smaller than those of the C-C and CH bonds in the benzene ring. Therefore, the main reactions in the cracking process of n-decane are breakage of a C-C bond and dehydrogenation. However, the cracking process in dimethylbenzene mainly involves the fracture and dehydrogenation of methyl groups. The theoretical calculations reasonably explained the experimental phenomena.

Key words: n-Decane, Dimethylbenzene, Supercritical condition, Pyrolysis, Binding energy

MSC2000: 

  • O643