Core‐shell structured HZSM‐5@mesoSiO₂ catalysts with tunable shell thickness for efficient n‐butane catalytic cracking

Abstract

A series of core‐shell HZSM‐5@mesoSiO2 with tunable shell thickness from 10 to 70 nm was prepared and studied for n‐butane catalytic cracking. With introducing of SiO2 shell, the catalytic performance of HZSM‐5@mesoSiO2 was largely enhanced, and n‐butane conversion rate per Al site reached to 2.43 min−1 over HZSM‐5@mesoSiO2(1:4) at 675°C which is nearly twice to that of HZSM‐5 (1.34 min−1). The diffusion property of n‐butane over as‐prepared sample was quantified by measuring the diffusional time constants using zero length column chromatography technique (ZLC). Combining with chemical reaction kinetic analysis, the quantitative relationship between diffusion property and catalytic performance was effectively established for the first time in n‐butane catalytic cracking. Positive linear correlation between diffusional time constant (D/R2) and n‐butane conversion rate per Al site could be found, which confirms that diffusion enhancement by hierarchical structure is an effective strategy to improve the activity of HZSM‐5 in catalytic cracking.

Modulating the Microenvironment of Silanols in Pure-Silicon Zeolites for Boosting Vapor-phase Beckmann Rearrangement of Cyclohexanone Oxime

“…As shown in Figure a, XRD patterns demonstrate that pure-silicon zeolites possess a target topology and high crystallinity. The characteristic diffraction peaks of S-1 zeolite at 2θ of 7.8°, 8.8°, 23.2°, 23.8°, and 24.3° indicate the formation of the MFI-type structure, and such patterns remain the same with the addition of HF and PHAPTMS. In the case of SSZ-74, the main diffraction peaks at 2θ of 8.6°, 8.9°, 23.1°, and 23.9° indicate the formation of the −SVR structure .…”

Synergetic Regulation of the Microstructure and Acidity of HZSM-5/MCM-41 for Efficient Catalytic Cracking of n-Decane

“…Except for the regulation of acid properties, the modification of the HZSM-5 pore structure is another important aspect for improving the catalytic performance in a catalytic cracking reaction. Decreasing the particle size of HZSM-5 into the nanoscale 21 or introducing a hierarchical structure such as a meso-microporous bimodal structure, 22,23 a macro-mesomicroporous trimodal porous structure, 24,25 a nanosheet structure, 26,27 or forming ZSM-5-based composite zeolites 28,29 could diminish the diffusion resistance of reactants or products and thus enhance the accessibility of active sites, resulting in an enhanced anticoking stability and catalytic performance.…”

“…Except for the regulation of acid properties, the modification of the HZSM-5 pore structure is another important aspect for improving the catalytic performance in a catalytic cracking reaction. Decreasing the particle size of HZSM-5 into the nanoscale or introducing a hierarchical structure such as a meso-microporous bimodal structure, , a macro-meso-microporous trimodal porous structure, , a nanosheet structure, , or forming ZSM-5-based composite zeolites , could diminish the diffusion resistance of reactants or products and thus enhance the accessibility of active sites, resulting in an enhanced anticoking stability and catalytic performance. Although some progress has been made to improve the catalytic performance of alkane catalytic cracking over HZSM-5-based catalysts, most of the research focus on a single modification of acidic properties or the structure; the synergetic regulation of acidic and textural properties as well as the structure–reactivity analysis based on a simple and practical preparation method has rarely been studied.…”