Kinetic analysis of the pathways to naphthalene formation from phenyl+1,3-Butadiyne reaction

Having a better understanding of polycyclic aromatic hydrocarbon (PAH) formation under flame conditions contributes to optimizing the fuel reforming process, where soot poisons the downstream catalyst. In this work, the phenyl + 1,3-Butadiyne reaction is systematically investigated to examine its contribution to naphthalene formation. The reaction potential energy surfaces were calculated using DFT/M06-2X/ccpvtz and G4 methods. The temperature- and pressure-dependent reaction rate constants were calculated using RRKM theory with solving master equation. The results revealed that 2-naphthyl could be directly formed by phenyl + 1,3-Butadiyne reaction. With H assistance, naphthalene could be formed by the pathway of phenyl + 1,3-Butadiyne - C 6 H 5 CHCCCH ( + H ) - C 6 H 5 CHCHCCH ( + H ) - naphthalene + H . The proposed pathway is kinetically favorable, and featured by relatively low energy barrier. The importance of the proposed pathway reaction was confirmed in a premixed and a diffusion C 2 H 4 /O 2 /Ar flame simulations, where the enhancement of naphthalene by the investigated reactions is notable. The mole fraction of A 2 is promoted by a factor of 10% in premix C 2 H 4 /O 2 /Ar flame and 30% in C 2 H 4 /O 2 /Ar counterflow flame, bringing the prediction results closer to the experimental results. The relative contribution of different reaction route to A 2 formation is evaluated for HACA, cyclopentadienyl radical-cyclopentadienyl radical, phenyl-vinylacetylene[1], benzyl radical-propargyl radical, indene-CH 2 and phenyl-1,3-Butadiyne routes in premixed and diffusion C 2 H 4 /O 2 /Ar flames. This work suggests that the PAH growth by 1,3-Butadiyne addition reaction is an effective pathway for A 2 formation, which should be considered in future PAH mechanism. & COPY; 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

The formation of naphthalene from the reaction between phenyl and 1,3-butadiyne is investigated, and it is found that 2-naphthyl can be directly formed and naphthalene can be formed through a pathway with the assistance of H. The importance of this pathway is confirmed in flame simulations.