Mg/Al/Zr hydrotalcite like compounds as catalysts for green synthesis of carbamates

Abstract

A series of Mg/Al/Zr hydrotalcite-like compounds catalysts were prepared using coprecipitation method with $\frac{{\mathrm{Zr}}^{4+}}{{\mathrm{Al}}^{3+}+{\mathrm{Zr}}^{4+}}$ ranging from 0 to 0.62. The catalytic performance of prepared hydrotalcite was evaluated in the synthesis of carbamates from carbon dioxide, amines and alcohols. The effect of Zr incorporation on the structural and textural features was performed using a panel of techniques including transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), elemental analysis (ICP-OES), ${\mathrm{N}}_2$ physisorption at 77 K and temperature-programmed desorption of NH₃ and CO₂. It has demonstrated that the catalyst Mg/Al/Zr containing the lowest amount of Zr exhibited a well crystallized hydrotalcite like phase, a highest specific surface area with an average particle size of 20 nm. The results of catalytic performances were in good correlation with the specific surface area and the basic properties of the catalysts favoring the yield of carbamate. Catalyst HT_0.20 showed the best performance in the phosgene-free-halogen-free synthesis of carbamates with a 46% of amine conversion at 473 K and a CO₂ pressure of 90 bars and selectivity toward the carbamate of 63% in presence of DMP as a dehydrating agent.

Supplemental data for this article can be accessed at the publisher’s website.

Keywords:

• Trimetallic hydrotalcite
• carbon dioxide
• carbamate
• acidic-basic property

Disclosure statement

There are no conflicts to declare.