Synthesis of bio-based diethyl pentane-1,5-diyldicarbamate via the carbonylation of pentanediamine with CO2 over a zirconium-doped CeO2 catalyst

Abstract

Diethyl pentane-1,5-diyldicarbamate (PDC), a bio-based intermediate used for isocyanate and polyurethanes, was synthesized by the direct carbonylation of CO2 and pentanediamine (PDA) with 2-cyanopyridine (2-CP) over Zr-doped CeO2. In this study, Zr-doped CeO2 catalysts with different contents of Zr are successfully synthesized to produce PDC from PDA, CO2, and ethanol. Among them, Zr0.05Ce exhibits enhanced reaction activity and the productivity reached 6.0 mmol·g−1·h−1. Characterizations based on X-ray photoelectron spectroscopy, Raman, and CO2/NH3-temperature-programmed desorption prove that the doping of Zr atoms into CeO2 regulates the acid–base sites and promotes oxygen vacancy formation, which is primarily responsible for the formation of monoethyl carbonate, an intermediate for diethyl carbonate (DEC). In-situ diffuse reflectance Fourier-transform spectrometry and Fourier-transform infrared spectroscopy reveal that PDA reacts with 2-CP to form N, N'-(pentane-1,5-diyl)dipicolinamide, which are transformed into PDC. Finally, the catalytic activity could be regenerated after calcination. This study presents a green route for producing bio-based carbamate by constructing C-N bond using CO2 as a carbonyl source, which can replace carbamates derived from petrochemical resources in the future.