Combining HC-SCR over Ag/Al2O3 and hydrogen generation over Rh/CeO2-ZrO2 using biofuels: An integrated system approach for real applications

• Integrated reactor system setups were used for evaluation of H2-assisted HC-SCR.
• Sol-gel prepared Ag/Al2O3 catalysts on monoliths are evaluated for HC-SCR.
• H2 for the HC-SCR reaction was produced over a Rh/CeO2-ZrO2 reformer catalyst.
• Catalysts were evaluated at real engine exhaust conditions.
• Fuel reformer gas gives a higher promotional effect on NOx reduction cf. bottled H2.

We report on a high NOx reduction activity over Ag/Al2O3 catalysts, using hydrogen produced in a fuel reformer. The focus of the study is to evaluate the performance of a hydrocarbon selective catalytic reduction (HC-SCR) catalyst in real conditions. Initially, the catalytic materials for the fuel reformer (Rh/CeO2-ZrO2) and the HC-SCR (Ag/Al2O3) were evaluated in separate bench-scale reactor setups. These two setups were subsequently joined into an integrated bench-scale reactor setup with the aim to evaluate the influence of the reformate on the HC-SCR activity in a controlled environment. In the final phase of the study a 4 wt.% Ag/Al2O3 catalyst doped with 100 ppm(w) Pt was scaled up and tested in a pilot-scale reactor setup. The pilot-scale reactor setup enabled evaluation of the HC-SCR activity in real exhaust gases generated by a single cylinder engine (genset) together with a hydrogen-rich gas supplied from a fuel reformer. Commercial biodiesel (NExBTL) was used as reducing agent for the HC-SCR as well as fuel in the fuel reformer for both the bench-scale and pilot-scale experiments. This study gives an excellent link between evaluations of the catalytic materials, controlled bench-scale experiments and applied engine experiments, proving a viable concept for lean NOx reduction together with onboard hydrogen production. A NOx conversion of above 70% was reached at temperatures below 250 °C, in bench-scale experiments when hydrogen produced in the fuel reformer is added.

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