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.
The development of an efficient catalyst especially with a high productivity for decarboxylation of L-lysine to cadaverine, is of both industrial and economic significance. Here, we reported the synthesis of RuO2 well-confined in the supercage of FAU zeolite (RuO2@FAU) through in situ hydrothermal strategies. A set of characterizations, such as XRD, Raman, TEM, XPS, NH3-TPD and N2 physical adsorption, confirmed the successful encapsulation of RuO2 clusters (~1.5 nm) inside the FAU zeolite. RuO2@FAU had the higher cadaverine productivity of 120.9 g/L/h/mmol cat., which was almost six times that of traditionally supported ruthenium oxide catalysts (21.2 g/L/h/mmol cat.). RuO2@FAU catalysts with different ammonia exchange degrees, as well as different Si/Al ratios were further evaluated. After optimization, the highest cadaverine productivity of 480.3 g/L/h/mmol cat. was obtained. Deep analysis of the electronic properties of RuO2@FAU indicated that the surface defect structures, such as oxygen vacancies, played a vital role in the adsorption or activation of L-lysine which finally led to a boosted performance. Furthermore, the mechanism of decarboxylation of L-lysine to cadaverine was proposed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.