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<p>Bifunctional catalysts based on SAPO-11 molecular sieves show high selectivity in the hydroisomerization of C<sub>16+</sub> n-paraffins. However, their efficiency is reduced due to diffusion limitations which negatively affect their activity and selectivity. To solve this problem, this paper proposes an approach to optimize the crystallization of hierarchical molecular sieves of SAPO-11 using aluminum isopropoxide and different dialkylamines (ethyl, propyl, isopropyl and butyl) as structure directing agents (SDA). The use of a complex of analytical methods (XRF, XRD, <sup>27</sup>Al/<sup>31</sup>P MAS NMR, Raman spectroscopy, SEM/TEM) allowed us to establish the relationship between the molecular weight of SDA, the reactivity of the gels and the formation of hierarchical porosity. It has been shown that the use of dipropyl-, diisopropyl- and dibutylamines results in the formation of amorphous xerogel-like structures with a particle size of 2–10&#xa0;nm, while diethylamine contributes to the formation of a layered phase with a particle size of ~ 300&#xa0;nm. An increase in the molecular weight of SDA significantly weakens the interaction between Al and P precursors, leading to the formation of nanocrystals with different structural characteristics. A comparative analysis revealed that among the SDAs studied, it is diisopropylamine that provides the formation of primary crystallites of minimal size (~ 50&#xa0;nm), forming a hierarchically porous structure (S<sub>BET</sub> = 254 m<sup>2</sup>/g, V<sub>meso</sub> = 0.22 cm<sup>3</sup>/g). Catalytic tests have confirmed the excellent activity and selectivity of SAPO-11 synthesized using diisopropylamine due to its improved diffusion properties. A correlation has been established between the chemical nature and size of SDA with the key characteristics of SAPO-11 (morphology, crystal size, and porosity). This correlation renders it possible to purposefully design catalytic systems for the hydroisomerization of C<sub>16+</sub> n-paraffins.</p> Graphical Abstract <p></p>

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Enhanced catalytic performance of bifunctional Pt/SAPO-11 in n-hexadecane hydroisomerization: hierarchical porosity engineered via SDA-assisted crystallization

  • 期刊论文

  • 发表日期：

    2025年7月14日

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  • Marat R. Agliullin,
  • Dmitry V. Serebrennikov,
  • Roman E. Yakovenko,
  • Rezeda Z. Kuvatova,
  • Nadezhda A. Filippova,
  • Arthur R. Zabirov,
  • Denis Sh. Sabirov

摘要

Bifunctional catalysts based on SAPO-11 molecular sieves show high selectivity in the hydroisomerization of C16+ n-paraffins. However, their efficiency is reduced due to diffusion limitations which negatively affect their activity and selectivity. To solve this problem, this paper proposes an approach to optimize the crystallization of hierarchical molecular sieves of SAPO-11 using aluminum isopropoxide and different dialkylamines (ethyl, propyl, isopropyl and butyl) as structure directing agents (SDA). The use of a complex of analytical methods (XRF, XRD, 27Al/31P MAS NMR, Raman spectroscopy, SEM/TEM) allowed us to establish the relationship between the molecular weight of SDA, the reactivity of the gels and the formation of hierarchical porosity. It has been shown that the use of dipropyl-, diisopropyl- and dibutylamines results in the formation of amorphous xerogel-like structures with a particle size of 2–10 nm, while diethylamine contributes to the formation of a layered phase with a particle size of ~ 300 nm. An increase in the molecular weight of SDA significantly weakens the interaction between Al and P precursors, leading to the formation of nanocrystals with different structural characteristics. A comparative analysis revealed that among the SDAs studied, it is diisopropylamine that provides the formation of primary crystallites of minimal size (~ 50 nm), forming a hierarchically porous structure (SBET = 254 m2/g, Vmeso = 0.22 cm3/g). Catalytic tests have confirmed the excellent activity and selectivity of SAPO-11 synthesized using diisopropylamine due to its improved diffusion properties. A correlation has been established between the chemical nature and size of SDA with the key characteristics of SAPO-11 (morphology, crystal size, and porosity). This correlation renders it possible to purposefully design catalytic systems for the hydroisomerization of C16+ n-paraffins.

Graphical Abstract