Starch bio-template synthesis of W-doped CeO2 for selective catalytic reduction of NOx with NH3: Influence of ammonia titration

Abstract

Herein, the influence of ammonia titration on the NH3-SCR activity of the tungsten-doped CeO2 catalyst synthesized via the starch bio-template spread self-combustion (SSC) method was investigated. The titration of ammonia water restrains the growth of cubic CeO2 crystallite and the formation of Ce4W9O33 in Ce4W2Oz(w/o) when the titration pH value of solution is up to 7.0, thus enhances the dispersion of cerium species and the concentration of tungsten on the surface of catalyst. Meanwhile, the further titration of ammonia water promotes the growth of cubic CeO2 in Ce4W2Oz(pH ≈ 7), decreases its BET surface area and increases its surface concentration of cerium species. And Ce4W2Oz(pH ≈ 9) presents less surface acid sites than Ce4W2Oz(pH ≈ 7) and Ce4W2Oz(w/o), although its surface concentration of tungsten species is higher than that of Ce4W2Oz(w/o). Ce4W2Oz(pH ≈ 7) exhibits the best NH3-SCR activity with more than 86% NOx conversion obtained at the temperature range of 275–500 °C. In addition, the formation of the smaller particle size cubic CeO2 crystallite plays an important role on the catalytic performance of the tungsten-doped CeO2 catalyst synthesized via the starch bio-template SSC method.