Boosting Stability and Efficiency: Defect-Rich Pd/NC Catalysts for Nitric Acid Reduction to Methyl Nitrite

Abstract

Reduction of nitric acid reaction (2NO + HNO₃ + 3CH₃OH → 3CH₃ONO + 2H₂O) can convert by-product nitric acid into raw material methyl nitrite in the coal to ethylene glycol (CTEG) technology. This not only realizes the efficient recycling of nitrogen resources but also plays a crucial role in mitigating environmental pollution. Despite being a promising catalyst, the Pd/C catalyst face challenges due to its high metal loading, substantial loss rate, and consequent issues of poor stability, presenting obstacles in meeting industrial requirements. To address this issue, a defect strategy has been employed to develop a low-loaded 0.3% Pd/NC catalyst with robust metal-support interaction, resulting in a significant enhancement of catalyst stability. Remarkably, even after undergoing five cycles, the catalyst maintains a high nitric acid conversion rate of 90%. This improved performance can be attributed to the strong metal-support interaction driven by electron transfer from the nitrogen-doped carbon (NC) substrate to the Pd nanoparticles evident in the Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma (ICP) results. This interaction effectively suppresses the leaching of the active Pd nanoparticles, leading to significantly enhanced stability and a noticeable reduction in the loss rate. Raman spectrum and electron paramagnetic resonance (EPR) results can further reveal that the increase in the defect density lead to the strong metal-support interaction after nitrogen doping (pyridinic-N-dominated). These findings highlight the significant potential of the Pd/NC catalyst and its applicability in expediting the industrialization process of catalyst.

Graphical Abstract