Coking and decoking chemistry for resource utilization of polycyclic aromatic hydrocarbons (PAHs) and low-carbon process

Low-carbon process for resource utilization of polycyclic aromatic hydrocarbons (PAHs) in zeolite-catalyzed processes, geared to carbon neutrality-a prominent trend throughout human activities, has been bottlenecked by the lack of a complete mechanistic understanding of coking and decoking chemistry, involving the speciation and molecular evolution of PAHs, the plethora of which causes catalyst deactivation and forces regeneration, rendering significant CO2 emission. Herein, by exploiting the high-resolution matrix-assisted laser desorption/ionization Fourier-transform ion cyclotron resonance mass spectrometry (MALDI FT-ICR MS), we unveil the missing fingerprints of the mechanistic pathways for both formation and decomposition of cross-linked cage-passing PAHs for SAPO-34-catalyzed, industrially relevant methanol-to-olefins (MTO) as a model reaction. Notable is the molecule-resolved symmetrical signature: their speciation originates exclusively from the direct coupling of in-cage hydrocarbon pool (HCP) species, whereas water-promoted decomposition of cage-passing PAHs initiates with selective cracking of inter-cage local structures at 8-rings followed by deep aromatic steam reforming. Molecular deciphering the reversibly dynamic evolution trajectory (fate) of full-spectrum aromatic hydrocarbons and fulfilling the real-time quantitative carbon resource footprints advance the fundamental knowledge of deactivation and regeneration phenomena (decay and recovery motifs of autocatalysis) and disclose the underlying mechanisms of especially the chemistry of coking and decoking in zeolite catalysis. The positive yet divergent roles of water in these two processes are disentangled. These unprecedented insights ultimately lead us to a steam regeneration strategy with valuable CO and H2 as main products, negligible CO2 emission in steam reforming and full catalyst activity recovery, which further proves feasible in other important chemical processes, promising to be a sustainable and potent approach that contributes to carbon-neutral chemical industry.