(314c) Mercury Oxidation Over Cupric Chloride/Alumina Catalyst for Mercury Emissions Control

Based on our previous mechanistic study of the heterogeneous catalytic oxidation of elemental mercury (Hg(0)) vapor over cupric chloride (CuCl₂)-based catalyst on α-Al₂O₃ was conducted in our previous study.  The objective of this work is to evaluate the performance of CuCl₂/γ-Al₂O₃ under simulated flue gas conditions.  Performance tests were conducted in a fixed bed reactor, and both fresh and spent CuCl₂/g-Al₂O₃ catalysts were characterized by SEM-EDX, TPD, XRD, XPS, and XAFS.

CuCl₂ impregnated on γ-Al₂O₃ showed excellent mercury oxidation performance at 140 °C under a simulated flue gas containing 10 ppbv Hg(0), 10 ppm HCl, 2,000 ppm SO₂, 6% O₂, 7% H₂O, 12% CO₂, and 400 ppm NO.  Over 90% Hg(0) oxidation during 150 hours evaluation was achieved and high SO₂ gas concentration (up to 2,000 ppm) did not show any negative effect due to increased acidity on the catalysts surface from CuCl₂.  Similar to other metal oxide catalysts, NH₃ gas has an inhibition effect on mercury oxidation efficiency. The competitive adsorption of NH₃ gas on active sites may have prohibited the adsorption of reactive species such as HCl.  The inhibitory effect of NH₃ gas can be mitigated by increasing HCl concentration.  CuCl₂ is expected to be able to be used as a catalyst in a temperature window after the air preheater.