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

Abstract

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.

Highly Efficient Decarboxylation of L-Lysine to Cadaverine Catalyzed by RuO2 Encapsulated in FAU Zeolite

“…Our previous work showed that active surface oxygen vacancies in catalysts facilitated the adsorption of intermediate in the decarboxylation of L-lysine [13]; therefore, the relationship between the quantity of oxygen vacancies in catalysts and their catalytic performances were studied. The high-resolution O 1s spectra for RuO 2 @FAU, RuO 2 @FAU-12 and RuO 2 @FAU-NH 4 -3 catalyst were depicted in Figure 7A-C.…”

“…Products were determined using LC-UV (Waters) equipped with a C18 column (100 Å, 5 µm, 4.6 mm × 250 mm) according to the method described in our previous work [13]. To be brief, 50 µL of the diluted solution and 50 µL of dansyl chloride (5 mg/mL in acetone) were successively added into a 4 mL centrifuge tube, and the mixture was heated by ultrasonic pretreatment for 10 min in the dark.…”

“…It indicated that a Ru-based catalyst was a candidate for the decarboxylation of L-lysine to cadaverine. In our previous works [12,13], Ru-based catalysts with different kinds of supports were prepared by the traditional impregnation method and further evaluated in the decarboxylation of L-lysine. Among those tested supports, zeolite supported ruthenium oxide catalyst performed much better with a greatly enhanced selectivity of cadaverine (54%).…”

Cerium-Doped Manganese Oxide Catalyst for the Oxidative Coupling Synthesis of Fluorescent 2-Amino-1,9-dimethyl-3H-phenoxazin-3-one Using Atmospheric Oxygen

“…), and create unique synergistic effects and interactions between elements. 19,20 Appropriate element doping can provide an effective route to improve oxygen activation capacity. 21,22 Among them, Ce-doped metal oxide catalysts exhibit good catalytic oxidation performance, which can be ascribed to their unique amphoteric properties, and to the Ce 4+ /Ce 3+ redox pair.…”

“…Doping metal oxide with another element can change lattice parameters, generate additional active sites (defects, vacancies, etc. ), and create unique synergistic effects and interactions between elements. , Appropriate element doping can provide an effective route to improve oxygen activation capacity. , Among them, Ce-doped metal oxide catalysts exhibit good catalytic oxidation performance, which can be ascribed to their unique amphoteric properties, and to the Ce 4+ /Ce 3+ redox pair. − Therefore, a cerium-doped manganese oxide may create a unique synergy between Mn and Ce, greatly enhancing their oxygen activation ability, realizing the replacement of H 2 O 2 with O 2 (or atmospheric oxygen) as the oxidant …”