Closed-loop ppm-level H2 micro-dosing to DOC–DPF–SCR for cold-start: WLTC-resolved low-temperature NOx control without detectable H2 slip or N2O penalty


Yilmaz A.C. Shambilova A.
23 January 2026Elsevier Ltd

International Journal of Hydrogen Energy
2026#203

In this study, cold-start emissions were addressed by ppm-level hydrogen (H2) micro-dosing at the inlet of a diesel oxidation catalyst (DOC) to accelerate low-temperature chemistry and shape nitrogen dioxide to total NOx ratio (NO2/NOx) for a downstream selective catalytic reduction (SCR) system within a DOC–diesel particulate filter (DPF)–SCR–ammonia slip catalyst (ASC) line. Cold-start emissions were mitigated by ppm-level hydrogen (H2) micro-dosing at the diesel oxidation catalyst (DOC) inlet to accelerate low-temperature chemistry and shape the NO2/NOx ratio for the downstream selective catalytic reduction (SCR) within a DOC–diesel particulate filter (DPF)–SCR–ammonia slip catalyst (ASC) line. Engine-bench tests followed a WLTC-derived transient at 23 °C and −7 °C soaks. Closed-loop H2 (0–1000 ppm, dry) was enabled only for DOC-inlet temperature <200 °C, with a mid-bed limit ≤230 °C. Metrics included T50 for CO and total hydrocarbons (THC), SCR-inlet NO2/NOx over 140–200 °C, integrated NOx (0–900 s), selectivity (H2, NH3, N2O), and robustness across space velocity (SV) = 8–55 s−1. H2 micro-dosing lowered light-off temperature at 50 % conversion (T50) by ~ 28–32 K (e.g., 23 °C: CO 179 → 151 °C; THC 198 → 170 °C at 500 ppm), raised NO2/NOx at 160 °C from 0.09 to 0.26, and reduced cold-start NOx by ∼29–31 % (23 °C: 0.34 → 0.24 g·test−1; −7 °C: 0.52 → 0.36 g·test−1). With modest early urea (α = 0.3–0.5 from 150 °C), the 23 °C reduction reached ∼36 %. Selectivity remained acceptable: H2 slip <5 ppm (limit of detection, LOD), N2O unchanged, and NH3 peaks <3.3 ppm (early-urea transient ≈ 6 ppm, ASC-managed). Exotherms were mild (ΔT(mid–inlet) 12–18 K at 500 ppm; peak Q < 0.35 kW). Benefits saturated beyond ∼500 ppm yet persisted across SV, yielding ∼40–64 mg NOx per normal liter of H2. An operational envelope of 100–500 ppm under T < 200 °C was indicated, providing a WLTC-resolved calibration basis for deployment.

Cold-start emissions , DOC light-off , Hydrogen micro-dosing , NO2/NOx shaping for SCR , WLTC-Derived engine transients

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Cukurova University, Department of Motor Vehicles and Transportation Technologies, Adana, Turkey
M.Auezov South Kazakhstan University, Department of Technological Machines and Equipment, Shymkent, Kazakhstan

Cukurova University
M.Auezov South Kazakhstan University

10 лет помогаем публиковать статьи Международный издатель

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