Issue 15, 2021

Self-assembly of silicoaluminophosphate nanocrystals in biphasic media with a water-insoluble structure-directing agent

Abstract

The catalytic performance of silicoaluminophosphates is dependent on their acidity and diffusion properties, which can be altered by an organic structure-directing agent (OSDA) as a result of its dominant effect on crystallization. Generally, the solubility of an amine in aqueous media is an important factor for judging whether it is suitable to serve as an OSDA in hydrothermal synthesis of zeolites. This work demonstrates that a hydrophobic molecule, tri-n-heptylamine, could be used as an OSDA for synthesis of hierarchically porous SAPO-31 in biphasic toluene/water media. It provides not only a new method for synthesis of zeolites but also a simple, inexpensive, and porogen-free pathway to generate hierarchical SAPOs. The synthesis allows manipulation of the nSi/(nAl + nP + nSi) ratio from 0.02 to 0.13 without noticeable change of morphological features. The self-assembled, nanocrystalline structure was revealed by combined XRD, SEM/TEM, N2 physisorption, and 27Al, 31P and 29Si MAS NMR spectroscopy, and the acidity was measured with NH3-IR. Catalytic evaluation in n-dodecane hydroisomerization shows that the isomer yield depends on the acid site density of the catalysts, and weak acid strength and high acid site density should be avoided to achieve high selectivity. On the optimized catalyst, the isomer yield has been significantly improved up to 79.7% in contrast to 58.1% for the sample derived from usual hydrothermal synthesis with di-n-hexylamine as an OSDA.

Graphical abstract: Self-assembly of silicoaluminophosphate nanocrystals in biphasic media with a water-insoluble structure-directing agent

Supplementary files

Article information

Article type
Paper
Submitted
14 Apr 2021
Accepted
10 Jun 2021
First published
14 Jun 2021

Catal. Sci. Technol., 2021,11, 5135-5146

Self-assembly of silicoaluminophosphate nanocrystals in biphasic media with a water-insoluble structure-directing agent

H. Ding, Q. Zhou, J. Li, K. Zhu and W. Fan, Catal. Sci. Technol., 2021, 11, 5135 DOI: 10.1039/D1CY00655J

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements