Insights into Coke Formation and Removal under Operating Conditions with a Quantum Nanoreactor Approach

Abstract

The in situ formation and removal of coke is a critical problem in heterogeneous catalysis, but its mechanism is not well understood. This work investigates the mechanism of carbon deposition and hydrogenation on an Fe cluster under high-temperature conditions with the density functional tight-binding (DFTB) based nanoreactor molecular dynamics (NMD) method. Our study shows that successive formation of carbon chains, rings, and fused rings occurred during the carbon deposition on Fe clusters. Hydrogenation of activated carbon happens through direct C–H coupling, while the hydrogenation of graphitic carbon involves hydrogenation of the edge carbon, ring-opening reaction, and dealkylation reaction. The main function of the Fe catalyst is to provide the active sites for H2 dissociation and dissociated H spillover, while its activity toward C–C bond breaking is limited. These results highlight the role of the DFTB-NMD method as an effective tool to investigate reaction mechanisms under operating conditions in heterogeneous catalysis.

Stabilized ε-Fe2C catalyst with Mn tuning to suppress C1 byproduct selectivity for high-temperature olefin synthesis

“…We implemented ab initio molecular dynamics (AIMD) simulations to gain a deeper understanding of the atomic-level mechanism behind the suppressed CO 2 selectivity caused by the highly dispersed manganese particles on ε-Fe 2 C. Given the multiple potential active sites and reaction pathways on the supported catalyst, we utilized a modified ab initio nanoreactor approach 32 , 33 to initially estimate the reaction channels. The simulations commenced with a uniform mixture of CO and H 2 above the catalyst surfaces, with periodic forcing introduced to boost the frequency of collisions and barrier crossing.…”

Kinetics and percolation: coke in heterogeneous catalysts

“…There are also recent studies based e.g. on (i) lattice Boltzmann simulations of multicomponent reaction-diffusion and coke formation in a catalyst with hierarchical pore structure [33], (ii) DFT-backed molecular dynamics method [34], and (iii) population balance theory [35]. Taken together, such models allow one to describe reactions running in various reaction regimes.…”

Celebrating the 10th Anniversary of the Youth Innovation Promotion Association, Chinese Academy of Sciences: Emerging Young Scientists in Physical Chemistry

“…The Letter by Li et al 37 theoretically analyses the surface states of GeSe for solar cell applications. The Letter by Lei et al 38 elucidates the mechanism of the in situ formation and hydrogenation of coke on Fe catalysts with a quantum mechanical nanoreactor approach. The Letter by Lu et al 39 discusses the polymer translocation times in polymer processing.…”

“…theoretically analyses the surface states of GeSe for solar cell applications. The Letter by Lei et al . elucidates the mechanism of the in situ formation and hydrogenation of coke on Fe catalysts with a quantum mechanical nanoreactor approach.…”