Formation mechanism and catalytic behavior of pyridinium-templated SAPO-5 zeolites using different phosphorus sources

Document Type

Article

Publication Date

2-1-2025

Abstract

SAPO-5 zeolite is crystallized with 5-ethyl-2-methyl-1-propylpyridinium hydroxide (empy]OH) as a new organic template where phosphoric acid (H3PO4) and pyrophosphoric acid (H4P2O7) are used as comparative phosphorus (P) sources. The effects of P source on crystallization rate, crystallinity, empy]+ template occlusion and porous properties of SAPO-5 are studied using various spectroscopy and microscopy techniques. empy]OH is found to be very selective and essential in crystallizing SAPO-5, whereby highly crystalline SAPO-5 (PA-5.0) with hierarchical structure is formed when H3PO4 is employed without adding any mesoporogen. Meanwhile, H4P2O7 facilitates nucleation by inhibiting crystal growth at z direction, producing hexagonal SAPO-5 nanoplates (PyP5.0, ca. 180 nm) with textural mesoporosity. PA-5.0 appear to be more active than PyP-5.0 in the esterification of lactic acid with ethanol (87.0 (+/- 1.8)% conversion, TOF = 0.35 min-1 , 100 % selective to ethyl lactate), whereby its performance is even better than the classical homogeneous catalysts (H2SO4, HCl, H3PO4) and other zeolites (SAPO-20, SAPO-34, H-Y, H-LTL, H-MOR) under non-microwave instant heating condition (160 degrees C, 20 min). Thus, the current study can open a new possibility on the synthesis of various phosphate-based microporous materials with tailored properties by using novel pyridinium templates and P sources.

Keywords

SAPO-5, 5-Ethyl-2-methyl-1-propylpyridinium hydroxide, Crystallization, Phosphoric acid, Pyrophosphoric acid

Publication Title

Materials Chemistry and Physics

Divisions

nanotechnology

Funders

Ministry of Education, Malaysia (FRGS/1/2022/STG05/USM/02/12)

Volume

332

Publisher

Elsevier

Publisher Location

PO BOX 564, 1001 LAUSANNE, SWITZERLAND

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