Upcycling of hazardous plastic waste by CO2 transformation-enhanced steam reforming over MgO-promoted Ni/C bifunctional catalyst

Abstract

Disposing hazardous plastic waste (e.g., used masks) poses a challenging issue, as these waste plastics often carry the risk of virus infection. CO2 transformation-enhanced steam reforming (CTESR) route was developed and newly synthesized dual-support Ni bifunctional catalysts were explored for the upcycling of disposed mask. Among the single-support Ni catalysts, Ni/CaO presented a high H2 yield (52.18 mmol/g), but it was inferior to Ni/MgO and Ni/C in terms of CO2 transformation capacity. Importantly, Ni/MgO demonstrated the lowest carbon deposition (∼2.67 wt%) due to the interaction between MgO and NiO, forming a NiO-MgO solid solution. In this sense, dual-support Ni catalysts were prepared to achieve extensive H2 production and CO2 reduction. Dual-support Ni/MgO-C was superior to other dual-support catalysts in terms of H2 selectivity (57.77 vol%), H2 yield (51.58 mmol/g), CO2 emission (1.72 mmol/g), and H2 production efficiency (ƞ: 0.74 g CO2/g H2). Moreover, it presented a remarkable synergistic effect on H2 yield and production efficiency, with an enhancement of 117.27 % and 32.58 %, respectively. The super catalytic performance was attributed to the unique properties of Ni/MgO-C, high dispersion of Ni/NiO active core, and proper interaction of Ni/NiO with the dual supports. In addition, MgO-promoted Ni/C catalysts with multiple MgO proportions were examined. Ni/MgO5-C5 was identified as the optimal bifunctional catalyst for H2-rich syngas production and CO2 elimination. Overall, this study established a highly effective and promising route by using dual-support Ni catalysts for upcycling hazardous plastic waste into H2-rich syngas while suppressing CO2 emission.