Thermal coupling of methane: Influence of hydrogen at 1330°C. Experimental and simulated results

• Published in: Journal of analytical and applied pyrolysis 1994, Vol.29 (2), p.183-205
• Main Authors: Guéret, C., Billaud, F.
• Format: Article
• Language: English
• Subjects: Chemistry; Exact sciences and technology; Hydrogen; Kinetics and mechanisms; Methane; Organic chemistry; Pyrolysis; Reactivity and mechanisms; Thermal coupling
• ISSN: 0165-2370; 1873-250X
• DOI: 10.1016/0165-2370(94)00798-5

Methane was decomposed in a plug-flow reactor at 1330°C and 1 atm. The methane feed was diluted with hydrogen (H 2:CH 4 = 0.5, 1 and 2). For simulations, the reactor was imitated with a cascade of 60 perfectly stirred reactors, and consideration was given to the temperature profile of the actual reactor. The chemkin code was used for numerical modeling. Simulations and analysis of the reaction rates showed that hydrogen acts as a diluent as well as a chemical agent via the following process: CH 4 + H· ⇄ ·CH 3 + H 2 Because of the reversibility of this process, the ·CH 3 concentration decreases, and hence the processes involving the ·CH 3 radical are less important. We also show that the ·C 2H 3 radical is the intermediate responsible for C 2H 2 formation by the following process: ·C 2H 3 ⇄ C 2H 2 + H· which is more favorable than the addition process because of the temperature (1330°C): C 2H 2 + ·C 2H 3 ⇄ ·C 4H 5 Considering the effect of hydrogen on ·CH 3 concentrations and hence on ·C 4H 5, the following process C 2H 2 + ·C 4H 5 ⇄ C 6H 6 + H· will also be disadvantaged, and this will be all the greater as dilution by H 2 is high. On the basis of experience, simulation shows that the increase in the H 2/CH 4 ratio leads to slower formation of benzene and heavy products, mainly to the benefit of C 2H 2.