Catalytic degradation of polyurea: synthesis of N-substituted carbamates with CuO–ZnO as the catalyst

Li, Qinghe; Wang, Peixue; Liu, Shimin; Fei, Yuqing; Deng, Youquan

doi:10.1039/c6gc01884j

Cited by 35 publications

(24 citation statements)

References 40 publications

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“…The activity of Zn/Al/Ce0 might originate from the surface acidic sites of Zn/Al mixed oxide 38 as well as zinc element that is generally used as the active component for carbamates synthesis. 2,6,22,41 Nevertheless, methylation proceeds obviously, giving the NMA and DMA selectivity of 10.9% and 24.3%, respectively. Aniline conversion, MPC selectivity and MPC yield increase over the Ce-containing Zn/Al/Ce catalysts, among which Zn/Al/Ce2.5 shows the highest carbamoylation catalytic activity.…”

Section: Catalytic Performancementioning

confidence: 99%

Methyl N-phenyl carbamate synthesis over Zn/Al/Ce mixed oxide derived from hydrotalcite-like precursors

et al. 2019

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Section: Catalytic Performancementioning

confidence: 99%

Methyl N-phenyl carbamate synthesis over Zn/Al/Ce mixed oxide derived from hydrotalcite-like precursors

et al. 2019

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“…[70] For the second step, the degradation of polyureas has been studied in detail using cheap urea as the carbonyl source over CuO-ZnO for the first time, 96% EHDC yield could be obtained with polyurea-hexamethylenediamine (PU-HDA). [71] The polyureas degradation involving urea and alcohols for the synthesis of dicarbamates could also be considered as a benign process for the indirect utilization of CO 2 . Further development and application of this reaction for various polyureas will be the issues of our next work.…”

Section: Methodsmentioning

confidence: 99%

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

2017

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Currently, industrial production of isocyanates, or diisocyanates in particular, has been exclusively based on phosgene processes. Phosgene is extremely toxic and large amounts of corrosive HCl are produced as a side product. In the view of environment protection and society safety, development of non-phosgene processes for isocyanates production will be highly desired, and this should be one of the most important missions for green chemistry and catalysis. In this review, efforts for development of non-phosgene method for syntheses of isocyanates, i.e., catalytic syntheses of N-substituted carbamates from nitro-or amino-compounds with CO, dimethyl carbonate (DMC), urea and even CO 2 etc. as carbonyl sources, then thermal cracking of N-substituted carbamates to afford corresponding isocyanates, are summarized, and a brief prospect for non-phosgene syntheses of isocyanates is also addressed.

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“…In our previous work, the polyureas could be successfully degraded in the existence of DEC or urea, the corresponding carbamates yields over 95 %. [16,17] Recently, we studied the formation and depolymerization of polymers generated during thermal cracking diethyl hexamethylenedicarbamate (EHDC). The polymers could be successfully converted by the alcoholysis reaction in the presence of ethyl carbamate.…”

Section: Introductionmentioning

confidence: 99%

Formation and Depolymerization of Oligomers during Thermal Cracking of Silicon‐Containing Carbamates

et al. 2019

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Polymerization reactions in the thermal cracking of N‐substituted carbamates to produce the corresponding isocyanates significantly reduce the yield of isocyanates and thus vastly hinder the industrial application of such non‐phosgene routes. Herein, we tried to recycle the oligomers generated during the thermal cracking of 3‐ethylcarbamatopropyltriethoxysilane (CPTS) to produce 3‐isocyanatopropyltriethoxysilane (IPTS). Firstly, the polymerized substrates of the pyrolysis reaction were analyzed by NMR, IR, MALDI‐TOF‐MS and TG, indicating the pyrolysis substrates were mixtures of CPTS (25 wt%), polyureas (74 wt%), imines, and other compounds (<1 wt %). The polyureas were generated by reaction of CPTS and IPTS. Then, the depolymerization of these polyureas was realized via alcoholysis in the presence of urea. It was found that the urea not only provides a carbonyl group source, but also forms hydrogen bonds with polyureas. In addition, NH3 co‐produced can also modify the reaction system microenvironment, which might be favorable for the dissociation of polyureas. With optimized conditions, more than 96 % of polymerized substrates could be reverted to CPTS for secondary cracking.

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Catalytic degradation of polyurea: synthesis of N-substituted carbamates with CuO–ZnO as the catalyst

Abstract: N-Substituted carbamates were successfully synthesized in two consecutive steps with the generation of H2O as the only side product over CuO–ZnO, i.e. synthesis of PUs by fixation of CO2 with aliphatic and aromatic diamines and the degradation of PUs subsequently.

Cited by 35 publications

References 40 publications

Methyl N-phenyl carbamate synthesis over Zn/Al/Ce mixed oxide derived from hydrotalcite-like precursors

Methyl N-phenyl carbamate synthesis over Zn/Al/Ce mixed oxide derived from hydrotalcite-like precursors

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

Formation and Depolymerization of Oligomers during Thermal Cracking of Silicon‐Containing Carbamates

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