High‐Resolution Single‐Molecule Fluorescence Imaging of Zeolite Aggregates within Real‐Life Fluid Catalytic Cracking Particles

Abstract

Fluid catalytic cracking (FCC) is a major process in oil refineries to produce gasoline and base chemicals from crude oil fractions. The spatial distribution and acidity of zeolite aggregates embedded within the 50-150 mm-sized FCC spheres heavily influence their catalytic performance. Singlemolecule fluorescence-based imaging methods, namely nanometer accuracy by stochastic chemical reactions (NASCA) and super-resolution optical fluctuation imaging (SOFI) were used to study the catalytic activity of sub-micrometer zeolite ZSM-5 domains within real-life FCC catalyst particles. The formation of fluorescent product molecules taking place at Brønsted acid sites was monitored with single turnover sensitivity and high spatiotemporal resolution, providing detailed insight in dispersion and catalytic activity of zeolite ZSM-5 aggregates. The results point towards substantial differences in turnover frequencies between the zeolite aggregates, revealing significant intraparticle heterogeneities in Brønsted reactivity.

Characterization of Porous Materials by Fluorescence Correlation Spectroscopy Super-resolution Optical Fluctuation Imaging

“…It is important to note that higher order autocorrelation and cross-correlation would improve the resolution even further, 15,20 to a range of ఙ ೣ √ < ߪ < ߪ ௫௬ where n is the order of the correlation, but require overcoming computational challenges (computation time and memory usage scale as the correlation order squared) 15 and have brightness/sampling artifacts that cause the pixel intensities to vary over a very large dynamic range (spatially highlighting bright areas and masking dim ones). 2,15 For proof-of- concept, we demonstrate here only 2 nd order autocorrelation and deconvolution analysis, similar to use of 2 nd order autocorrelation SOFI reported in the literature. 2 Super-resolution distributions of the diffusion dynamics are obtained from curve fitting analysis and image fusion.…”

“…2,15 For proof-of- concept, we demonstrate here only 2 nd order autocorrelation and deconvolution analysis, similar to use of 2 nd order autocorrelation SOFI reported in the literature. 2 Super-resolution distributions of the diffusion dynamics are obtained from curve fitting analysis and image fusion. Using fitting models for Brownian diffusion reported in previous imaging extensions of FCS, 24, 25 the resulting diffusion coefficient at each pixel is spatially mapped (see Methods).…”

“…[1][2][3][4][5][6][7][8][9][10][11] Despite the importance of these materials, a detailed understanding of the relationship between nanoscale structure and the functional capabilities is lacking due to insufficient characterization techniques. Electron and force microscopy methods have experimental requirements that distort and even destroy the porous structure.…”

Super-resolution microscopy as a powerful tool to study complex synthetic materials

“…For example, SRM has been used to unveil the photophysical and electronic properties of devices made of conductive polymers 43 or perovskite 104 . SRM has had also a dramatic impact in the field of catalysis, in which single reactivity events have been probed with nanometric accuracy in catalytic reactors such as zeolites 84,[105][106][107][108][109] . Finally, SRM mild imaging conditions allow one to study biomaterials in situ, for example in cellular environments.…”

Recent progress on single-molecule nanocatalysis based on single-molecule fluorescence microscopy

“…For a precise understanding of the structurereactivity relationship of the nanocatalysts, it is highly desirable to study the surface reactions at single-molecule or singleparticle level in real time. Recently, the newly-developed technique of single-molecule nanocatalysis based on single-molecule fluorescence microscopy has been proved to be effective for this goal [12][13][14][15][16][17] and has been used extensively as a new tool to study the catalytic properties of heterogeneous nanocatalysts at single molecule or single particle level [12,[18][19][20][21][22][23][24][25][26][27][28][29].…”