Identification of superactive centers in thermally treated formamide-intercalated kaolinite

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 \ud 230 - 350 degrees Celsius temperature range 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 super-active centers as a result of mechanochemical activation and heat treatment (thermal deintercalation). \ud The structural variance of surface species decreases with the increase of grinding time. The ungrounded mineral contains a low amount of weakly acidic and basic centers. After 3 hours of grinding, the number of acidic centers increases significantly, while on further grinding the super-active centers show increased basicity.\ud With the increase of grinding time and treatment temperature the amount of bicarbonate- and bidentate-type structures decreases in favor of the carboxylate- and monodentate

XRD, TEM and thermal analysis of yttrium doped boehmite nanofibres and nanosheets

Yttrium doped boehmite nanofibres with varying yttrium content have been prepared at low temperatures using a hydrothermal treatment in the presence of poly (ethylene oxide) surfactant (PEO). The resultant nanofibres were characterized by X-ray diffraction (XRD), and transmission electron microscopy (TEM). TEM images showed the resulting nanostructures are predominantly nanofibres when Y doping is less than 5 %; in contrast Y rich phases were formed when doping was around 10 %. \ud The doped boehmite and the subsequent nanofibres/ nanotubes were analyzed by thermogravimetric and controlled rate thermal analysis methods. The boehmite nanofibres produced in this research thermally transform at higher temperatures than boehmite crystals and boehmite platelets. Boehmite nanofibres decompose at higher temperatures than non-hydrothermally treated boehmite

Conventional and Controlled Rate Thermal analysis of nesquehonite Mg(HCO3)(OH)•2(H2O)

The understanding of the thermal stability of magnesium carbonates and the relative metastability of hydrous carbonates including hydromagnesite, artinite, nesquehonite, barringtonite and lansfordite is extremely important to the sequestration process for the removal of atmospheric CO2. The conventional thermal analysis of synthetic nesquehonite proves that dehydration takes place in two steps at 157, 179 degrees Celsius and decarbonation at 416 degrees Celsius and 487 degrees Celsius. Controlled rate thermal analysis shows the first dehydration step is isothermal and the second quasi-isothermal at 108 and 145 degrees Celsius. In the CRTA experiment carbon dioxide is evolved at 376 degrees Celsius. CRTA technology offers better resolution and a more detailed interpretation of the decomposition processes of magnesium carbonates such as nesquehonite via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition. Constant-rate decomposition processes of non-isothermal nature reveal partial collapse of the nesquehonite structur

Dynamic and Controlled Rate Thermal analysis of hydrozincite and smithsonite

The understanding of the thermal stability of zinc carbonates and the relative stability of hydrous carbonates including hydrozincite and hydromagnesite is extremely important to the sequestration process for the removal of atmospheric CO2. The hydration-carbonation or hydration-and-carbonation reaction path in the ZnO-CO2-H2O system at ambient temperature and atmospheric CO2 is of environmental significance from the standpoint of carbon balance and the removal of green house gases from the atmosphere. The dynamic thermal analysis of hydrozincite shows a 22.1% mass loss at 247 degrees Celsius. The controlled rate thermal analysis (CRTA) pattern of hydrozincite shows dehydration at 38 degrees Celsius, some dehydroxylation at 170 degrees Celsius and dehydroxylation and decarbonation in a long isothermal step at 190 degrees Celsius.(erre meg visszaterni) The CRTA pattern of smithsonite shows a long isothermal decomposition with loss of CO2 at 226 degrees Celsius. CRTA technology offers better resolution and a more detailed interpretation of the decomposition processes of zinc carbonate minerals via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition. The CRTA technology offers a mechanism for the study of the thermal decomposition and relative stability of minerals such as hydrozincite and smithsonite

Dynamic and Controlled Rate Thermal analysis of attapulgite

The thermal decomposition of the clay mineral attapulgite has been studied using a combination of dynamic and controlled rate thermal analysis. In the dynamic experiment two dehydration steps are observed over the 20-114 and 114-201 degrees Celsius temperature range. In the dynamic experiment three dehydroxylation steps are observed over the temperature ranges 201-337, 337-638 and 638-982 degrees Celsius. The CRTA technology enables the separation of the thermal decomposition steps. Calculations show the amount of water in the attapulgite mineral is variable. Dehydration in the CRTA experiment occurs as quasi-isothermal equilibria. Dehydroxylation occurs as a series of non-isothermal decomposition steps. CRTA technology offers better resolution and a more detailed interpretation of the decomposition processes of a clay mineral such as attapulgite via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition. Constant-rate decomposition processes of non-isothermal nature reveal partial collapse of the layers of attapulgite as the attapulgite is converted to an anhydride