title: Identification of superactive centers in thermally treated formamide-intercalated kaolinite.
abstract: The thermal behavior of a formamide-intercalated mechanochemically activated (dry-ground) kaolinite was investigated by thermogravimetry-mass spectrometry (TG-MS) and diffuse reflectance Fourier transform infrared spectroscopy (DRIFT). After the removal of adsorbed and intercalated formamide, a third type of bonded reagent was identified in the temperature range 230-350 degrees C decomposing in situ to CO and NH3. The presence of formamide decomposition products, as well as CO2 and various carbonates identified by DRIFT spectroscopy, indicates the formation of superactive centers as a result of mechanochemical activation and heat treatment (thermal deintercalation). The structural variance of surface species decreases with the increase of grinding time. The unground mineral contains a small amount of weakly acidic and basic centers. After 3 h of grinding, the number of acidic centers increases significantly, while on further grinding the superactive centers show increased basicity. With the increase of grinding time and treatment temperature the number of bicarbonate- and bidentate-type structures decreases in favor of the carboxylate- and monodentate-type ones.
authors: Department of Environmental Engineering and Chemical Technology, University of Veszprém, Hungary.
authors: Erzsébet
authors: E
authors: Horváth
authors: János
authors: J
authors: Kristóf
authors: Ray L
authors: RL
authors: Frost
authors: Emma
authors: E
authors: Jakab
authors: Eva
authors: E
authors: Makó
authors: Veronika
authors: V
authors: Vágvölgyi
mesh_terms: D005559:Formamides / Q000737:chemistry*; D007364:Intercalating Agents / Q000737:chemistry*; D007616:Kaolin / Q000737:chemistry*; D015394:Molecular Structure; D013499:Surface Properties; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D005559:Formamides; D007364:Intercalating Agents; D007616:Kaolin; C031066:formamide