Mn-Doped Highly Dispersed RuO₂ Catalyst with Abundant Oxygen Vacancies for Efficient Decarboxylation of l‑Lysine to Cadaverine

Chemical decarboxylation of l-lysine is a promising route for producing cadaverine, which is the key monomer of new polyamide, polyurethane, and nylon materials. Currently, the wide application of Ru-based catalysts is restricted by its low efficiency which was mainly caused by the severe agglomeration of ruthenium nanoparticle. In this study, manganese (Mn) doped ruthenium oxide catalyst was synthesized through the wetness impregnation method with Beta zeolite as the candidate support for efficient decarboxylation of l-lysine to cadaverine. Structure characterization showed that RuO₂ was the main phase of ruthenium oxide nanoparticles. The prepared Ru–Mn/Beta catalysts exhibited a high dispersion of ruthenium oxide nanaoparticle on Beta, which maximized the utilization of active sites. Meanwhile, abundant oxygen vacancies were generated after Mn doping to balance the charge of the disturbed long-term periodic structure in the RuO₂ crystalline, which greatly facilitated the adsorption and activation of l-lysine by the capture of carboxylic groups. A full conversion was obtained with Ru–Mn/Beta, and a selectivity of cadaverine up to 54% was reached in a short time of 1.5 h. The cadaverine production rate in Ru–Mn/Beta was 60.8 mg/L/min, which was almost triple that in Ru/Beta (17.7 mg/L/min). The synergetic catalysis of metal active sites and oxygen vacancies provides a new opportunity to design efficient catalyst of decarboxylation of amino acids.