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

Abstract

Direct visualization of spatiotemporal evolution of molecules and active sites during chemical transformation in individual catalyst crystal will accelerate the intuitive understanding of heterogeneous catalysis. So far, widespread imaging techniques can only provide limited information either with large probe molecules or in model catalyst of large size, which are beyond the interests of industrial catalysis. Herein, we demonstrate a feasible deep data approach via synergy of multiscale reaction-diffusion simulation and super-resolution structured illumination microscopy to illustrate the dynamical evolution of spatiotemporal distributions of gas molecules, carbonaceous species and acid sites in SAPO-34 zeolite crystals of several micrometers that are typically used in industrial methanol-to-olefins process. The profound insights into the inadequate utilization of activated acid sites and rapid deactivation are unveiled. The notable elucidation of molecular reaction-diffusion process at the scale of single catalyst crystal via this approach opens an interesting method for mechanism study in materials synthesis and catalysis.

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

“…Structured illumination microscopy (SIM) was used to resolve the location of carbonaceous species for ZEOL samples. According to the previous experimental work 46 – 48 and theorical calculations 49 – 51 , the excitation wavelengths of B n + , N n + , PH n + , and PYR n + are situated around 390, 480, 560, and 640 nm, respectively, and the corresponding emission wavelengths are located in the range of 480–490, 500–520, 620–630, and 670–700 nm, respectively. The wavelengths of illumination and emission detection of SIM used in this work are 405 (detection at 435–485 nm), 488 (detection at 500–545 nm), 561 (detection at 570–640 nm), and 640 nm (detection at 663–738 nm), respectively, which can cover the characteristic area of excitation and emission wavelengths of B n + , N n + , PH n + , and PYR n + .…”

“…The interatomic interactions were described by the condensed-phase-optimized molecular potentials for atomistic simulation studies (COMPASS) force field. The applicability of the used force field was checked in the previous work 51 . The Ewald & Group summation method has an Ewald accuracy of 10 −5 kcal mol −1 when it is used for calculating electrostatic potential energy.…”

Nature‐Inspired, Computer‐Assisted Optimization of Hierarchically Structured Zeolites

“…Gao et al. [ 79 ] developed a deep data method by coupling multiscale reaction‐diffusion simulations and super‐resolution structured illumination microscopy to explore the characteristics of the SAPO‐34 catalyzed methanol‐to‐olefins reactions. This method realizes the direct visualization of the spatiotemporal evolution of molecules (including coke) and active sites in a micrometer‐sized crystal, while conventional imaging techniques can only provide limited information with probe molecules or catalysts of large size.…”

Implications of Co‐Feeding Water on the Growth Mechanisms of Retained Species on a SAPO‐18 Catalyst during the Methanol‐to‐Olefins Reaction

“…Other research works have demonstrated the formation of larger (and insoluble) polycyclic aromatics in small-pore catalysts, which have been hypothesized to be on the external surface of the crystal [25] or forming cross-cavity polycyclic aromatic species at the edge of the crystal. [42] In two recent works from Liu and co-workers, [43,44] the nature of the coke species have been revealed using Fourier transformed ion cyclotron resonance (FT-ICR/MS). These works indicate, for the first time, that coke growths in SAPO-18 or -34 following a cage-passing mechanism, cross-linking multicore aromatics.…”