HYDROGENATION OF TOLUENE TO METHYLCYCLOHEXANE OVER PROMOTED SKELETAL NICKEL CATALYSTS

Abstract

Introduction. Methylcyclohexane (MCH) is a key solvent and a promising Liquid Organic Hydrogen Carrier (LOHC). The selective hydrogenation of toluene to MCH requires efficient, stable and cost-effective catalysts. Skeletal nickel (Raney Ni) is widely used but suffers from rapid deactivation. The purpose of this work is to develop multicomponent skeletal nickel catalysts modified by industrial ferroalloys (FeMo, FeTiMn, FeMn) and to study their catalytic performance in toluene hydrogenation. Methods. Catalysts were prepared by high-frequency induction melting of Ni-Al-ferroalloy systems, followed by leaching with 20% NaOH. Surface morphology and composition were characterized by SEM-EDXRS and BET. Kinetic experiments were carried out in a high-pressure autoclave (0.25 L) at 393–473 K and hydrogen pressures of 2.0–12.0 MPa. Results. The addition of 3.0 wt.% FeMo or 5.0 wt.% FeTiMn increased the hydrogenation rate by 2.2–2.5 times compared to unmodified Raney Ni. Specific surface area reached 82.1 m²/g for Ni-Al-FeMo and 78.5 m²/g for Ni-Al-FeTiMn. SEM-EDXRS showed uniform distribution of Fe, Mo, Ti, Mn in the nickel matrix. The reaction order was zero with respect to toluene and first with respect to H₂ (at 2-6 MPa). Apparent activation energy was 34.5 kJ/mol for Ni-Al-FeMo and 38.2 kJ/mol for Ni-Al-FeTiMn. The catalysts exhibited 99.9% selectivity to MCH and maintained >92% of initial activity after 100 h on stream. Conclusion. Ferroalloy-modified skeletal nickel catalysts are highly efficient, selective and stable, making them promising for industrial hydrogen storage and petrochemical applications.