Molecular elucidating of an unusual growth mechanism for polycyclic aromatic hydrocarbons in confined space

Abstract

Extension and clustering of polycyclic aromatic hydrocarbons (PAHs) are key mechanistic steps for coking and deactivation in catalysis reactions. However, no unambiguous mechanistic picture exists on molecule-resolved PAHs speciation and evolution, due to the immense experimental challenges in deciphering the complex PAHs structures. Herein, we report an effective strategy through integrating a high resolution MALDI FT-ICR mass spectrometry with isotope labeling technique. With this strategy, a complete route for aromatic hydrocarbon evolution is unveiled for SAPO-34-catalyzed, industrially relevant methanol-to-olefins (MTO) as a model reaction. Notable is the elucidation of an unusual, previously unrecognized mechanistic step: cage-passing growth forming cross-linked multicore PAHs with graphene-like structure. This mechanistic concept proves general on other cage-based molecule sieves. This preliminary work would provide a versatile means to decipher the key mechanistic step of molecular mass growth for PAHs involved in catalysis and combustion chemistry.

Directed transforming of coke to active intermediates in methanol-to-olefins catalyst to boost light olefins selectivity

“…Besides GC-MS, the matrix-assisted laser desorption/ionization Fourier-transform ion cyclotron resonance mass spectrometer (MALDI FT-ICR MS) was also used to obtain the complementary spectrum for the evolution of coke species 19 ranged from 300 to 1600 Da confined in CHA cavity during steam cracking, as shown in Fig. 4b .…”

“…These hydrocarbon pool species (HCPs), typically including the methyled-benzene carbocations 10 , 11 and cyclopentadienyl species 12 , 13 , are decisive for light olefins selectivity, owning to the altering of acidity 14 , reaction paths 15 , kinetics 8 , 9 , molecular transport 16 , and among others. However, the HCPs are also coke precursors that can readily evolve to polycyclic aromatic hydrocarbons (PAHs), the typical coke species, through cyclization 17 and cross-linked mechanism 18 , 19 , accelerating catalyst deactivation 20 . Therefore, such dual-role of HCPs impedes achieving superior light olefins selectivity while maintaining long catalyst lifetime in MTO over zeolitic catalyst.…”

Imaging spatiotemporal evolution of molecules and active sites in zeolite catalyst during methanol-to-olefins reaction

“…In addition, the adsorption bands at ~561 nm (PH n + ) and ~640 nm (PYR n + ) are relatively unconspicuous in the small crystal. It has been recently shown that carbonaceous species located in adjacent cavities can be further connected through windows during reaction to form heavier carbonaceous species 48 , 55 . As can be seen from Fig.…”

“…The organic compounds were extracted by addition of 1 mL CH 2 Cl 2 with 100 ppm internal standard C 2 Cl 6 for 1 h. Analysis of the extracted phase was performed on an Agilent 7890A/5975C GC/MS instrument, equipped with a HP-5 capillary column and FID detector. Then the carbonaceous species in the extracted phase were then mixed with matrix 1,8,9-anthracenetriol and further analyzed by a 15-T SolariX XR FT-ICR MS (Bruker Daltonics) 55 . The instrument was equipped with a Nd:YAG laser ( λ = 335 nm) and a time-of-flight mass analyzer in reflection mode.…”

Risk Evaluation and Molecular Biomarkers Identification of Firefighter Suffering Lung Cancer Via the TCGA Database

“…In our study, the major chemical that produced by a flame-proof door when it is on fire was PAHs, VOCs, SO2 and cyanide, they were well-known carcinogens for a long time. All the combustion byproducts in our study were researched in many other kinds of research [50][51][52]. Research showed that in hundreds of lung cancer cases there was a clear trend of increasing risk of lung cancer with increasing cumulative exposure to PAHs [53].…”