Experimental and theoretical study on 2-ethylnorbornane pyrolysis under atmospheric and high pressure

A wide pressure range pyrolysis experiment of 2-ethylnorbornane (EthNB), a potential high energy-density fuel, was conducted in a micro-reactor at 773-1098 K, 0.1-3.0 MPa and 2.1-10.3 s to explore its high-pressure pyrolysis mechanism. Altogether 30 pyrolysis products are detected and quantified using online GC-MS/FID, which major products are ethylene, methane, 1,3-cyclopentadiene and benzene in descending order of importance. The first-order kinetic analysis shows that no isomerization of exo-EthNB and endo-EthNB into each other is observed and the activation energies of overall EthNB pyrolysis slightly increase from 0.1 MPa to 3.0 MPa, indicating the unfavorable effect of pressure. A detailed theoretical calculation of the EthNB initial pyrolysis is performed to explain the formation and selectivity of primary products under different pressures, which includes C-C dissociations and H-abstraction reactions leading to the diradical (BR8), C8H13 (BR1), C7H11 (BR2) and six C9H15 (R1-R4, R6, R7) radicals. These radicals undergo further decomposition via beta-C-C scission reactions to generate unstable intermediates and then the intermediates proceed to dissociate or isomerize. Finally, the other aliphatic and aromatic species may mainly come from the secondary reactions of primary products decomposition involving small radicals, C5 cyclic hydrocarbons and aromatics, as well as cross-coupling reactions of them.