Various calcium loading and plasma-treatment leading to controlled surface segregation of high coke-resistant Ca-promoted NiCo–NiAl2O4 nanocatalysts employed in CH4/CO2/O2 reforming to H2

Abstract

High coke-resistant Ca-promoted NiCo–NiAl2O4 nanocatalysts with different calcium loading (0, 0.25, 0.5 and 1.5 wt%) were synthesized via hybrid sol-gel-plasma method. Synthesized samples were applied in the CH4/CO2/O2 reforming to H2 reactions. Analyses revealed that the calcium addition caused the lower surface area, non-uniform distribution and larger particle size. Therefore, higher activity and yield were found for the nanocatalyst without calcium while catalytic activity and yield were descended for the other ones. This trend was according to the covering effect of calcium and undesirable effect of calcium over the surface area and particle size distribution. But owing to the enhanced coke gasification rate of Ca-rich samples, by increasing of Ca amount, coke deposition was descended and stable performance was promoted. Due to the time on stream performance (TOS) during the 48 h and at 750 °C, 1.5 wt% Ca-promoted NiCo–NiAl2O4 (NCCa1.5A (SGP)) was stable, but demonstrated the lower yield. Moreover, 0.25 wt% Ca-promoted NiCo–NiAl2O4 nanocatalyst (NCCa0.25A (SGP)) was illustrated the higher yield in comparison with NCCa1.5A (SGP). It must be noted that just 2.7% deactivation for H2 yield was detected for NCCa0.25A (SGP) during the 48 h TOS performance. H2 yield of the NCCa0.25A (SGP) at 850 °C was 84%. Based on the reverse trends of the yield and TOS performance, NCCa0.25A (SGP) was able to present as a promising nanocatalyst for CH4/CO2/O2 reforming to H2. Moreover, this offer was ascribed to the excellent coke resistance and superior catalytic performance of NCCa0.25A (SGP).