Synthesis and Characterization of Silver Hollandite and Its Application in Emission Control

Silver hollandite, Ag 1.8 Mn 8 O 16, has been synthesized by ion exchange of cryptomelane in AgNO 3 melt. Compared to the previously described synthesis process, thermal decomposition of AgMnO 4 at 970 °C under 5 kbar oxygen for 7 days, this newly developed synthesis process is easily carried out, enabling synthesis of significant quantities for evaluation, testing, and scale-up. Silver hollandite prepared by this new method has much smaller crystal size and thus much higher surface area compared with the previously available material. Application of silver hollandite for emission control has been examined. This material is an excellent low-temperature SO 2 absorbent as well as a highly active catalyst for CO and NO oxidation. Silver hollandite maintains its catalytic oxidation activity even while it is simultaneously aging by adsorption of SO 2 .