Thermal decomposition of SO42--intercalated Mg-Al layered double hydroxide Elimination behavior of sulfur oxides

The thermal properties of SO4 (2-)-intercalated Mg-Al layered double hydroxide (SO4 center dot Mg-Al LDH) were investigated using simultaneous thermogravimetry-mass spectrometry (TG-MS), and the elimination behavior of sulfur oxides from this double hydroxide was examined. The TG-MS results showed that SO4 center dot Mg-Al LDH decomposed in five stages. The first stage involved evaporation of surface-adsorbed water and interlayer water in SO4 center dot Mg-Al LDH. In the second, third, and fourth stages, dehydroxylation of the brucite-like octahedral layers in SO4 center dot Mg-Al LDH occurred. The fifth stage corresponded to the elimination of SO4 (2-) intercalated in the interlayer of Mg-Al LDH, producing SO2 and SO3. The thermal decomposition of SO4 center dot Mg-Al LDH resulted in the formation of SO2 and SO3 at 900-1000 degrees C, which then reacted with H2O to form H2SO3 and H2SO4. The elimination of sulfur oxides increased with the decomposition time and temperature. Almost all of the intercalated SO4 (2-) was desulfurized from SO4 center dot Mg-Al LDH at 1000 degrees C; however, Mg-Al oxide was not formed due to the production of MgO and MgAl2O4.