Pyrolysis kinetics of ZnAl LDHs and its calcined products for H2S removal

This paper reports the calcined products of the hydrotalcite-based ZnAl-layered double hydroxides (LDHs) for H2S removal. The thermal behavior of ZnAl LDHs was investigated by thermogravimetry-differential scanning calorimetry (TG-DSC) and thermogravimetry-mass spectrum (TG-MS). The activation energies were estimated by the Kissinger method and Flynn-Wall-Ozawa (FWO) method. To clarify the physical and chemical transformation during pyrolysis, the initial sample (ZnAl LDHs) and its pyrolysis products calcined at several different temperatures were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscope. The results show that there are two major stages of the thermal decomposition of ZnAl LDHs: Stage I with an intense endothermic peak at 196 A degrees C in DSC curve is ascribed to the removal of water (both the physically absorbed water and the interlayer water) and a small loss of CO2. Stage II with a broad endothermic peak is due to the decomposition of the carbonate anions and a little part of dehydroxylation from brucite-like sheets. The activation energies calculated by the Kissinger and FWO method are 110.7 and 112.8 kJ mol(-1) of stage I and 94.3 and 98.1 kJ mol(-1) of stage II, respectively.