Issue 7, 2015

Direct synthesis of HZSM-5 from natural clay

Abstract

Highly crystalline HZSM-5 zeolite was directly synthesized through the steam-assisted conversion (SAC) approach using kaolin as the raw material, where NH3·H2O was used as an alkaline vapor source. The catalytic performance of the obtained HZSM-5 with SiO2/Al2O3 ratios from 25.67 to 80 was investigated for converting methanol to light olefins (MTO). The results indicated that NH3·H2O provided alkalinity to dissolve the raw materials and NH4+ cations to balance the charge of the framework. Highly crystalline HZSM-5 with crystal size in the range of 0.8–1 μm was obtained within 1.0 h at 190 °C. The obtained HZSM-5 possessed high SBET (above 440 m2 g−1) and high total pore volume (above 0.3 cm3 g−1). The acidity of the HZSM-5 was affected by the SiO2/Al2O3 molar ratio and residual metallic elements (such as Fe, Ti, Ca, P, etc.) in the leached metakaolin. The existence of the metallic elements similarly affected HZSM-5 modified with metal cations. HZSM-5 with a higher SiO2/Al2O3 molar ratio was favourable for the formation of C2–C4 olefins. The selectivity of C2–C4 olefins reached 68% when the SiO2/Al2O3 molar ratio was 68.79. This productive and facile method is inexpensive because the ammonium and calcination ion exchange processes are unnecessary.

Graphical abstract: Direct synthesis of HZSM-5 from natural clay

Article information

Article type
Paper
Submitted
28 Oct 2014
Accepted
22 Dec 2014
First published
22 Dec 2014

J. Mater. Chem. A, 2015,3, 4058-4066

Author version available

Direct synthesis of HZSM-5 from natural clay

F. Pan, X. Lu, Q. Zhu, Z. Zhang, Y. Yan, T. Wang and S. Chen, J. Mater. Chem. A, 2015, 3, 4058 DOI: 10.1039/C4TA05791K

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