Reaction of Solid Sodium Aluminate with Sulfur Dioxide

The reaction between solid sodium aluminate, one of the binary metal oxides, and SO2 was studied by using a gas flow reactor. - The sodium aluminates were obtained by evaporating sodium aluminate solutions with Na20/Al2O2- ratios (mole) between O.5 and 3.0, which were prepared by dissolving various amounts of metallic aluminum in sodium hydroxide solution. The reaction behavior and mechanism of sodium aluminate with SO2 were examined at 330°C and 130°C.In the case of reaction of sodium aluminate containing excess sodium, it was found that the rate of initial stage was fast, and the reaction in this initial stage occured between SO2 and NaOH involved in the sample. An approximately linear relationship existed between the amount of initial reaction and the amount of NaOH in the sample. On the other hand, the rate of later stage was slow, and in this region the reaction between Na2Al2O2-, involved in the sample, and SO2 occured. 'The rate of the reaction increased with an increase of the reaction temperature.The results of X-ray diffraction and IR analysis of the samples before and after the reaction suggested that the reaction was expressed by the following four equations, 2 NaOH SO2 -4- Na2SO2- + H20Na2Al2O2- + SO2 Na2SO2- + Al2O2-2 Na5A1O2- + 5 SO2 5 Na2SO2- + Al2O2-2 Na2SO3 + O2- -3.2 Na2SO4For Na2SO4 formation, it was recognized that Al2O2-, which was formed from the reaction between Na2Al2O2- and SO2, promoted the oxidation of Na2SO2-.