Improved gel synthesis enables routes to Al-rich chabazite

Phase pure Al-rich CHA(1.6-2.0) was prepared both from seed-assisted and non-seeded gel routes. Two different gel composition spaces were explored and both cation composition and the addition of seeds had a large effect on the product phase. A working hypothesis that guided the initial synthesis work is that the product phase and SAR is a strong function of the SiO2 solubility for the given gel system and addition of a seed would nucleate a CHA phase. Adsorption studies on pure and mixed alkali/alkaline earth CHA(2.0) showed homogeneous isosteric heats and low N-2 Henry's constants for the pure Na and Li forms as well as Ca(2)Li(8)CHA(2.0); whereas a heterogenous heat and significant increase in Henry's constant were observed for higher Ca loadings in this mixed Ca/Li system. This behavior strongly suggests that in the dehydrated form, <2Ca/uc site inside the hexagonal prism of CHA, inaccessible to N-2. This work shows the specific cation content of the phase pure, Al-rich CHA can be tailored to exhibit highly effective adsorbents for removing N-2 from N-2-containg streams.

Automated summary

Phase-pure, Al-rich CHA was prepared through gel routes, with the product phase being influenced by cation composition and seed addition. Adsorption studies revealed variations in adsorption properties in mixed Ca/Li systems with different Ca loadings.