Understanding the pyrolysis of ethane over an extended pressure range can help improve the understanding of the pressure dependence of pyrolysis of higher alkanes. For this work, a variable pressure flow reactor was operated at 1073 K at pressures of 0.1 and 2.0 MPa to gain insight into the effect of pressure on the rate of ethane decomposition and formation of the major products and deposit precursors, such as benzene and toluene. Ethane conversion was achieved by sweeping through residence times over a range from 0.2 to 6 s at 0.1 MPa and from 2 to 30 s at 2.0 MPa. The results showed that, at higher pressure, more ethane is converted to benzene and toluene, species that readily lead to deposit formation; additionally, at an elevated pressure, the selectivity of hydrogen, ethylene, and methane is significantly affected. The experimental results were compared to several chemical kinetic mechanisms to gauge the performance of the mechanisms under the various test conditions. A mechanistic analysis showed that the variation in the selectivity of the products as a result of pressure was in large part due to the shift in the kinetics of ethyl radicals: unimolecular β-scission dominated at lower pressures, while bimolecular addition and abstraction reactions become important at high pressures.

Thermally cracking fuel in a fuel processing facility or undergoing pyrolysis in the anode channel of a fuel cell can lead to coke deposition. The formation of coke occurs via chemical kinetic pathways that are largely dependent on poly aromatic hydrocarbons (PAHs). The formation of PAH's largely depends on species which include ethylene, acetylene, butadiene, benzene and toluene. Pentane is a relatively simple structure for modeling purposes, yet large enough that it produces some of the relevant chemistry of real fuels. Experiments were conducted in a newly designed variable pressure flow reactor (VPFR) built to process both liquid and gaseous reactants at pressures to 4.0 MPa and temperatures to 1373 K. The VPFR was initially validated via ethane pyrolysis experiments and comparing the results with existing literature data. Pentane experiments were done over a range of temperatures (923 K -1073 K), pressures (1 -2.0 MPa) and residence times (30 ms -40 s). The product selectivity appeared to be greatest influenced by pressure and level of fuel conversion. Pressure increases ethylene production but has an inverse effect on ethane production. Soot precursors appeared at higher levels of conversion. The results of the experiments were compared to an existing chemical kinetic mechanism with good agreement.