Promoted RhPt bimetallic catalyst supported on δ-Al2O3 and CeO2–ZrO2 during full-scale autothermal reforming for automotive applications: Post-mortem characterization

• Mesoporosity:CAT1 > CAT 2. Enhances conversion of heavy hydrocarbons and selectivity.
• Heavy HC were mostly converted at the front of CAT 1. Large coke deposition at CAT 1M
• Encapsulation of active sites in CAT 1 is more significant than in CAT 2
• S-poisoning is significant in CAT 2, S-capacity is reduced by loss of surface area.
• The highest θs after 40 h was 0.15, which is below the RhPt sulfur capacity, ∼ 0.19.

The influence of sulfur and coke formation on the steam reforming of diesel was evaluated for two promoted RhPt bimetallic catalysts, composed of 1:1 Rh:Pt/10:10 La2O3: CeO2/ δ-Al2O3 (CAT 1) and 1:1 Rh:Pt/4:5 MgO: Y2O3/CeO2 − ZrO2 (CAT 2). The intrinsic activity is related to the total Rh and Pt area observed after the exposure to sulfur. Therefore, the degree of deactivation is related to the amount of sulfur deposited on the active metal sites. Sulfur analysis on the aged catalyst washcoat showed a decreasing sulfur concentration in the axial direction of the reformer. The estimated sulfur coverage related to metal surface area after 40 h on stream reached values of 0.145 in CAT 2, below the equilibrated sulfur coverage of 0.19 after tests with DIN 590. Thus, showing a partial deactivation due to sulfur poisoning. Further catalyst characterization on carbon deposits and thermal aging was performed by TPO, TGA, BET, CO chemisorption, and TEM analysis.

Spent catalyst after 40 h on stream. Aged washcoat samples taken at the poited locations. F: front, M: middle, B: back.Figure optionsDownload high-quality image (157 K)Download as PowerPoint slide