Porous Nitrogen-Doped Carbon Ni Nanocatalysts for H2-Free and Solvent-Free Pyrolysis of Real Coal Tar to Light Aromatics (C6–C10)

Catalytic fast pyrolysis (CFP) for aromatics production is a key strategy to achieve high-value-added utilization of real medium-low temperature coal tar (CT). However, this technology still suffers from low yield of aromatics and low selectivity for light aromatics (C₆–C₁₀). Herein, we found that Ni nanocatalysts (Ni/BNC) prepared by activation and N-doping of biochar can catalyze CT pyrolysis to produce light aromatics (C₆–C₁₀) without H₂ and solvent. Experimental and theoretical evidence suggests that N-doping can subtly improve the defect structure and optimize the electron transfer and charge distribution of Ni⁰ in Ni/BNC, favoring the adsorption and activation of CT pyrolysis components. Meanwhile, this strategy endows Ni/BNC with a large specific surface area, strong Ni⁰ metallicity, good dispersion, and suitable acidic sites, thus stabilizing the Ni⁰ activity center and accelerating the aromatization of aliphatic hydrocarbons and the cracking of polycyclic aromatic hydrocarbons (PAHs). The Ni/BNC catalyst achieves an 83.14% yield of aromatics at 500 °C without H₂ and solvent, among which the selectivity of light aromatics (C₆–C₁₀) reached 95.06%. Moreover, the N-doped carbon (BNC) achieves a high aromatics yield (70.73%) and light aromatics (C₆–C₁₀) selectivity (82.58%) without Ni loading. Additionally, Ni/BNC demonstrates applicability to a variety of coal tars. The experimental results show that this strategy extends to other transition metals (Fe, Co, Cu) with promising potential for application.