Abstract
The reaction of FeCl3, SeO2, and Pyridine (Py) in the presence of methanol (MeOH) under CO pressure generates a black precipitate, which has been confirmed as ferric di-selenide, FeSe2 through different structure characterization methods. Furthermore, impregnation of 5 wt% of FeSe2 onto γ-Al2O3 exhibits better catalytic performance than FeSe2 due to the highly dispersed and smaller particle sizes ca. 200–300 nm. The reductive carbonylation of nitrobenzene (NB) was investigated over FeSe2/γ-Al2O3 as a heterogeneous catalyst, delivering an excellent yield and high selectivity of methyl-N-phenyl carbamate (MPC). Moreover, a set of reactions was performed with variation in the reaction time, temperature, and pressure to investigate the effects of these factors. In particular, FeSe2/γ-Al2O3 is highly stable and can be recycled for up to five cycles without significant loss in catalytic performance. A mechanistic study was also conducted on this low-cost catalyst system, especially proposing a crucial role of FeSe2 (μ-CO) active species.
Highlights
Urethanes are essential precursors for producing isocyanates, the main material for manufacturing polyurethane, due to their transformation ability into isocyanates via thermal cracking.Conventionally, the production of urethanes involves the employment of phosgene, which is extremely toxic and harmful to the environment and human beings
A remarkable yield of methyl-N-phenyl carbamate (MPC) was obtained via the reductive carbonylation of NB over a catalyst system consisting of FeCl3, SeO2, and Py, which appeared to be converted into a heterogeneous ferrous diselenide, FeSe2
FeSe2 /γ-Al2 O3, which exhibited an impressive enhancement in terms of catalytic performance in the conversion of NB to MPC
Summary
Urethanes (carbamates) are essential precursors for producing isocyanates, the main material for manufacturing polyurethane, due to their transformation ability into isocyanates via thermal cracking. 6000 h−1 turnover frequency (TOF), which is the highest reported record to date [6,38] Even though these catalyst systems showed high efficiency, there are still some limits in recyclability and leaching problems of noble metals-based catalysts. Selenium metal or selenium compounds have been widely used in catalytic reductive or oxidative carbonylation processes to produce carbamates from the corresponding aliphatic and aromatic amines. Throughout our study on the reductive carbonylation of NB over different catalyst combinations consisting of Se-based and other metal halides to prepare MPC, we found that CuII Se2 , which has been already found by our research group as an active and novel heterogeneous catalyst [46], and FeII Se2 is found to be far more active than CuII Se2 species. The reductive carbonylation of nitroarenes over FeSe2 /γ-Al2 O3
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