Water-gas shift reaction over supported Pt and Pt-CeOx catalysts

Abstract

A comparison study was performed of the water-gas shift (WGS) reaction over Pt and ceria-promoted Pt catalysts supported on CeO 2 , ZrO 2 , and TiO 2 under rather severe reaction conditions: 6.7 mol% CO, 6.7 mol% CO 2 , and 33.2 mol% H 2 O in H 2 . Several techniques--CO chemisorption, temperature-programmed reduction (TPR), and inductively coupled plasma-atomic emission spectroscopy (ICP-AES)--were employed to characterize the catalysts. The WGS reaction rate increased with increasing amount of chemisorbed CO over Pt/ZrO 2 , Pt/TiO 2 , and Pt-CeO x /ZrO 2 , whereas no such correlation was found over Pt/CeO 2 , Pt-CeO x /CeO 2 , and Pt-CeO x /TiO 2 . For these catalysts in the absence of any impurities such as Na + , the WGS activity increased with increasing surface area of the support, showed a maximum value, and then decreased as the surface area of the support was further increased. An adverse effect of Na + on the amount of chemisorbed CO and the WGS activity was observed over Pt/CeO 2 . Pt-CeO x /TiO 2 (51) showed the highest WGS activity among the tested supported Pt and Pt-CeO x catalysts. The close contact between Pt and the support or between Pt and CeO x , as monitored by H 2 -TPR, is closely related to the WGS activity. The catalytic stability at 583 K improved with increasing surface area of the support over the CeO 2 -and ZrO 2 -supported Pt and Pt-CeO x catalysts.

Propane combustion over supported Pt catalysts

“…The particle size was estimated from the full width at half maximum of the XRD line of ZrO 2 using the Scherrer equation [26]. The mole fraction of the tetragonal phase in ZrO 2 was estimated as described in previous work [27].…”

Sour water–gas shift reaction over Pt/CeZrO2 catalysts

“…Ceria-containing catalysts can suffer from deactivation under WGSR conditions. Several reasons for deactivation have been reported, such as sintering of platinum [34,87,88], overreduction of support [89][90][91], and poisoning by carbonate species [33,34,89].…”

Low-Temperature WGS Reaction

“…Kim et al [81] then investigated the effect of support (Al 2 O 3 , SiO 2 , TiO 2 (P-25), CeO 2 , SiO 2 -Al 2 O 3 , yttria-stabilized zirconia (YSZ) and ZrO 2 ) on the WGS activity of bimetallic Pt-Ce catalysts. Figure 3.12 shows the effect of support on the WGS activity of bimetallic catalysts.…”