Controllable Synthesis and Structure-Performance Relationship of Silicalite-1 Nanosheets in Vapor Phase Beckmann Rearran
- PDF / 1,793,766 Bytes
- 11 Pages / 595.276 x 790.866 pts Page_size
- 47 Downloads / 183 Views
Controllable Synthesis and Structure‑Performance Relationship of Silicalite‑1 Nanosheets in Vapor Phase Beckmann Rearrangement of Cyclohexanone Oxime Chao Ge1 · Xiaojuan Sun1 · Dandan Lian1 · Zhikai Li2 · Jianbing Wu3 Received: 30 July 2020 / Accepted: 20 September 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Bulky silicalite-1 shows high catalytic activity for vapor phase Beckmann rearrangement of cyclohexanone oxime. However, it often deactivates rapidly and the structure-performance relationship is unclear. Here, a series of well-crystallized silicalite-1 catalysts from three-dimensional micron particles (n < 10) to two-dimensional nanosheets (10 ≤ n ≤ 18) were controllably synthesized using diquaternary ammoniums [CnH2n+1-N+(CH3)2-C6H12-N+(CH3)2-C6H13](Br−)2 (n = 6–18) as the structure directing agent. The influence of morphology of catalysts on active sites distribution and the pore confinement effect on caprolactam selectivity and the catalytic stability were studied by XRD, SEM, TEM, In situ vacuum IR, 29Si MAS NMR and N2 adsorption/desorption isotherms. The silicalite-1 nanosheets with relatively high crystallinity exhibited superior catalytic activity to almost 100% and remarkably high caprolactam selectivity (92%). The catalytic lifetime of silicalite-1 nanosheets could be increased by 28 times in comparison to bulky silicalite-1 zeolite. The external surface area and mesopore volume of the synthesized catalyst dramatically increase with increasing the tail length of surfactant from C 6 to C18, leading to high active sites and coke tolerance capacity. It was found the lifetime of the catalysts is almost linearly related to the product of area of silanol nest and volume of mesopore (Asilanol·nest*Vmeso) with correlation coefficient of 0.97, which strongly supports the excellent performance of nanosheets results from the synergetic effect of its high active sites and high coke tolerance capacity. This provides a theoretic guide for designing new catalysts with high catalytic activity. Graphical Abstract Silicalite-1 nanosheets were controllable synthesized through adjusting alkyl tail length of diquaternary ammoniums, resulting in large mesoporous volume and external surface area, which effectively improve high coke tolerance capacity and active sites of catalysts and exhibit much longer catalytic lifetime and high selectivity.
Keywords Controllable synthesis · Structure-performance relationship · Silicalite-1 nanosheets · Cyclohexanone oxime · Beckmann rearrangement Extended author information available on the last page of the article
13
Vol.:(0123456789)
1 Introduction The Beckmann rearrangement of cyclohexanone oxime (CHO) to ε-caprolactam (CPL) is a green and efficient chemical production route in Nylon-6 industrial production [1–4]. The conventional liquid phase Beckmann rearrangement makes use of H2SO4 as catalyst which results in production of low-value ammonium sulfate, environmental pollution and some corrosion problems [4]. To overcome these
Data Loading...
