Interference microscopy and FTIR microscopy are applied to study intracrystalline concentration profiles of methanol in CrAPO-5 zeolite crystals. By using both techniques, the high spatial resolution of interference microscopy is complemented by the ability of FTIR spectroscopy to pinpoint adsorbates by their characteristic IR bands. For the first time two-dimensional concentration profiles of an unprecedented quality are reported which show a nonhomogeneous distribution of adsorbate in zeolite crystal under equilibrium with the adsorbate vapor. These nonhomogeneous profiles are attributed to regular intergrowth effects in CrAPO-5. A possible internal structure of CrAPO-5 crystals is suggested.
Additional component(s) introduced into the reaction gel allow for a stable framework substitution of Cr in significant amounts. Appropriate component(s) and metal compounds, especially those of Al, are primary factors determining the substitution. The products of the system {triethylamine−acetate ions−Cr3+ ions} have been characterized in more detail and compared with those from other synthesis procedures. The Cr heteroatoms are 4-fold bonded to the framework and their coordination is complemented by two ligands from the pores (water molecules in the calcined form) to give the favored octahedral-like coordination. The coordination can be changed reproducibly from 6 to 4 by heating the crystals over 550 K (dehydration) and vice versa by cooling (hydration). The framework Cr(III) cannot be oxidized and causes no framework charge. The reaction conditions, differing from those in the classical syntheses, enable the control of the crystal morphology. The crystals can be grown as flat hexagonal pellets of a perfect morphology with high crystallinity and sorption properties
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.