Measurements of Methane Pyrolysis in a Constant Volume Batch Reactor at High Temperatures and Pressures

Abstract

Methane pyrolysis is a process used to generate hydrogen gas and carbon black without the creation of carbon dioxide. Methane pyrolysis in a constant volume batch reactor was investigated at temperatures of 892 K, 1093 K, and 1292 K with reaction times of 15 s, 30 s, 60 s, 180 s, and 300 s with an initial pressure of 399 kPa. A quartz vessel (32 ml) was placed inside an oven where it was heated to high temperatures. The temperature and pressure inside the vessel were measured during the reaction. To begin the process, the quartz vessel was vacuumed, then flushed with nitrogen before being vacuumed again prior to every experiment. Pressurized methane was then injected into the vessel for an allocated reaction time and collected in a sample bag post reaction for analysis. The molar concentration of the product gas was analyzed using gas chromatography. Due to the accumulation of carbon on the vessel after a reaction, the vessel was cleaned with high pressure air after each experiment. Hydrogen molar concentration increased as temperature and reaction time increased. For experiments completed at 892 K the hydrogen molar concentration varied from 10.0 ± 5.9 % with a 15 s reaction time to 26.5 ± 0.8 % for a 300 s reaction time. For experiments completed at 1093 K the hydrogen molar concentration varied from 21.8 ± 3.7 % for a 15 s reaction time to 53.0 ± 2.9 % for a 300 s reaction time. For experiments completed at 1292 K the hydrogen molar concentration varied from 31.5 ± 1.7 % for a 15 s reaction time to 53.0 ± 2.4 % for a 300 s reaction time. Minor species concentrations were the greatest for experiments completed at 1292 K when compared to 892 K and 1093 K. There was a general decrease in minor species concentration for experiments completed at 1093 K when compared to 892 K. The summation of all minor species molar concentrations never exceeded 1 % of the total species detected.