Revisiting the synthesis of Au/TiO2 P25 catalyst and application in the low temperature water–gas shift under realistic conditions

Abstract

The performance of Au/TiO2 P25 synthesized at different pH's (8, 9 and 10) is studied over time-on-stream in low temperature water–gas shift (WGS) at 21bar under semi-industrial conditions. Furthermore, their performance is compared with a commercial CuO/ZnO/Al2O3 low temperature WGS catalyst and AUROlite 1wt.% Au/TiO2 as a reference. Sulfur severely poisons the Au/TiO2 catalyst, which is irreversible over time-on-stream under high pressure (21bar) WGS conditions.The Au/TiO2 P25 catalysts are synthesized using deposition precipitation to a targeted loading of gold close to 1wt.% and are carried at three different pH (8, 9 and 10) under controlled conditions. The influence of parameters such as final pH, rate of addition of basic solution, type of basic solution are discussed. A higher final pH resulted in smaller gold particles deposited on TiO2-P25. The Au/TiO2-P25 catalyst prepared at the higher final pH (pH 10) showed higher WGS activity which relates to the averaged smaller particle size of the gold on TiO2-P25. The Au/TiO2-P25 catalyst prepared at lower final pH (pH of 8) is stable, while the catalysts prepared at pH of 9 and 10 deactivate over 130h timeon stream.