Synthesis of Al-rich Beta zeolite through surface response design

Abstract

A central composite design was proposed to analyze the effects of temperature, time, and Si/Al and H₂O/SiO₂ ratios on the crystallization of Al-rich Beta framework. The proposed response variable was based on X-ray diffraction patterns of synthesized materials. Si/Al ratios of synthesized Beta zeolites were predominantly larger than those employed in synthesis gels, indicating loss of Si during sample washing. Crystal sizes of synthesized Beta zeolites tended to increase with decreasing values of Si/Al ratio. It was also found that crystallinity is inversely proportional to temperature and directly proportional to Si/Al ratio. However, this latter correlation is only valid for zeolites synthesized at H₂O/SiO₂ ratios lower than 15.22, a value that is independent of synthesis temperature and time. For H₂O/SiO₂ values larger than the respective threshold, crystallinity becomes inversely proportional to the Si/Al ratio.

Keywords:

• Al-rich Beta zeolite
• Si/Al
• H₂O/SiO₂
• crystallinity
• crystal size

Acknowledgement

The authors also thank the Faculty of Chemical Engineering of the Federal University of Uberlândia for making available the Scanning Electron Microscopy and X-ray Fluorescence multiuser laboratories.

Additional information

Funding

The authors would like to thank the Brazilian National Council for Scientific and Technological Development, CNPq [grant number 141042/2008-7] and Minas Gerais Research Foundation, FAPEMIG [grant number APQ-01009-16] for financial support.