The role of Mn doping in CeO₂ for catalytic synthesis of aliphatic carbamate from CO₂

Abstract

A novel highly active Mn-doping ceria heterogeneous catalyst IJMnO x -CeO 2 ) was prepared and dedicated to the catalytic synthesis of aliphatic carbamates from CO 2 , aliphatic amines and methanol in one step. The as-obtained catalyst can attain a high yield of carbamate up to 82%, and can also be recycled at least four times through a simple procedure. It was observed that the Mn doping to ceria can alleviate the catalyst deactivation in consecutive catalytic recycles. In this regard, the role of Mn doping in the ceria in the synthesis of the aliphatic carbamates was investigated by means of X-ray diffraction (XRD), Raman spectra, specific surface areas (BET), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), CO 2 -temperature programmed desorption (CO 2 -TPD) and in situ diffuse reflectance infrared Fourier transform (DRIFT). The characterization demonstrated that the presence of MnO x in the ceria can not only inhibit the formation of stable carbonate species on the surface of the catalyst but also promote the decomposition/consuming of the carbonaceous species during the synthesis of aliphatic carbamates so as to allow improvement of the recyclability of the catalyst.

CO2 Conversion with Alcohols and Amines into Carbonates, Ureas, and Carbamates over CeO2 Catalyst in the Presence and Absence of 2‐Cyanopyridine

“…For example, the carbamate synthesis using CeO 2 or MnÀCeO 2 catalysts has been reported recently. [24] We expect that the development of heterogeneous catalysts for the synthesis of carbamates will be more important in terms of one of options of CO 2 utilization.…”

A Simple Zinc Catalyst for Carbamate Synthesis Directly from CO2

“…Catalyticsynthesis of 1 from aniline, CO 2 ,a nd TMOS. Decreased yields of 1 were observed at high CO 2 pressures (10)(11)(12)(13)(14). The catalyst could be reused at least three times without losing its activity.C ompared with the other reaction systems, such as Pd-catalyzedd irect arylation, [23] the Zn(OAc) 2 /phen system was both catalytic and reusable, and thereby its applications in industrial processes are extended.…”

“…[5] The carbamate group (RNHCOOR')i sakey motif in medicinal chemistry, [6] insecticide products, [7] andp olyurethanes (PU). Severalr outes for carbamate synthesis directly from CO 2 are shown in Scheme 1: A) Application of organic halides; [10] B) Addition of the corresponding alcohol; [11] C) Addition of acetal with adehydrating agent; [12] and D) The use of tin alkoxide. [8] Traditionally, industrialp olycondensation processes used to produce PUs begin with ar eactionb etween an amine and phosgene, followed by the polyaddition of polyols.…”

“…[9] One strategy involves designing novel synthetic routest oc arbamates via isocyanate obtainedb yh eating carbamates. Severalr outes for carbamate synthesis directly from CO 2 are shown in Scheme 1: A) Application of organic halides; [10] B) Addition of the corresponding alcohol; [11] C) Addition of acetal with adehydrating agent; [12] and D) The use of tin alkoxide. [13] The use of N-tosylhydrazone [14] or diaryl iodonium salt [15] for carbamate synthesis is considered to be an alternative method, but only for aliphatic amine activation.…”

Important Green Chemistry and Catalysis: Non‐phosgene Syntheses of Isocyanates – Thermal Cracking Way

“…Under 5 MPa CO 2 , 150 ℃, 12 h, ＞99% benzylamine conversion and 92% methyl benzylcarbamate selectivity were obtained even in the absence of the dehydrating agents. The CeO 2 catalyst could be reused after the calcination at 600 ℃ for 3 h. Recently, Hou and co-workers [60] successfully prepared a Mn-doping ceria heterogeneous catalyst (MnO x -CeO 2 ), which displayed high activity in synthesis of aliphatic carbamates from CO 2 , aliphatic amines and methanol. The as-obtained catalyst could attain a high yield of carbamate (up to 82%), and it could be also recycled at least four times through a simple procedure.…”