On the Choice of Ion Exchange Method for FAU Type Zeolite to Synthesize an Active and Selective Catalyst for Isobutane Alkylation with Butylenes
A comparative study of the trends in ion exchange of NaX zeolite (molar ratio Si/Al = 1.34) pelletized without binder has been performed using successive treatment with calcium, lanthanum, and ammonium nitrate solutions at 80°C with intermediate calcination after each ion exchange stage or by ion exchange in an autoclave at 180°C with calcium nitrate and lanthanum and ammonium nitrate solutions without intermediate calcinations. It has been found that for the complete replacement of sodium cations in the zeolite framework (less than 1 wt % residual sodium oxide), a fourfold ion exchange at 80°C with vigorous stirring and intermediate calcinations or a twofold ion exchange at 180°C in an autoclave without intermediate calcinations is required. Comparison of the physicochemical and catalytic properties of the obtained catalyst samples with almost identical chemical composition has shown a significant advantage of ion exchange in the autoclave, since the zeolite retains its initial structural characteristics.
Keywordsion exchange NaX zeolite autoclave alkylation isobutane butylene porous structure acidity X-ray diffraction phase analysis
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