Particle size evaluation of Ni/γ-Al2O3 catalysts for efficient syngas production via CO2 reforming of CH4

• Ni/γ-Al₂O₃ catalysts with various Ni particles size were prepared. • Prepared catalysts were used in the reaction of CH 4 reforming by CO 2 . • CH 4 conversion improved by increasing the Ni particles size. • Intrinsic TOF decreased with increasing the Ni particles size. • Carbon deposition enhanced as the Ni particles size increased. This work examines how the size of nickel particles impacts CH 4 reforming with CO 2 over Ni/γ-Al 2 O 3 catalysts aimed at syngas production. A set of catalysts containing Ni loadings from 5 to 20 wt% (with particle sizes between 3.5 and 10.5 nm) was prepared and tested at CO 2 /CH 4 =1, GHSV=60 L/(g cat ·h), 700-800 °C, and 1 bar. Increasing the Ni loading enhanced CH 4 conversion from 38.6% (Ni5, 700 °C) to 70.2% (Ni20, 800 °C) and CO 2 conversion from 45.4% to 85.6%. However, turnover frequency (TOF) decreased from 1.23 to 0.90 s -1 by increasing the Ni particle size, which indicates a structure-sensitive reaction. The H 2 /CO ratio stayed under one (0.899–0.919) because of the reverse water-gas shift (RWGS) reaction, while coke formation increased from 0.037 to 0.083 μmol/(g cat ·min). The experimental data were well captured by a size-dependent kinetic model derived from the Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism, achieving a mean absolute relative residual under 3%. The size-independent activation energy (Eₐ ∞ ) for CH 4 reforming with CO 2 was determined as 86.1 kJ/mol. These results highlight the role of Ni particle size in regulating the activity, selectivity, and carbon deposition behavior in the CO 2 reforming of CH 4 .