Phosgene-free synthesis of hexamethylene-1,6-diisocyanate by the catalytic decomposition of dimethylhexane-1,6-dicarbamate over zinc-incorporated berlinite (ZnAlPO4)

How To Get Isocyanate?

Isocyanate, a pivotal chemical intermediate to synthesize polyurethane with widespread applications in household appliances, automobiles, and construction, is predominantly produced via the phosgene process, which currently holds a paramount status in industrial isocyanate production. Nonetheless, concerns arise from the toxicity of phosgene and the corrosiveness of hydrogen chloride, posing safety hazards. The synthesis of isocyanate using nonphosgene methods represents a promising avenue for future development. This article primarily focuses on the nonphosgene approach, which involves the formation of carbamate through the reaction of nitro-amino compounds with carbon monoxide, dimethyl carbonate, and urea, among other reagents, subsequently leading to the thermal decomposition of carbamate to get isocyanate. This paper emphasizes the progress in catalyst development during the carbamate decomposition process. Single-component metal catalysts, particularly zinc, exhibit advantages such as high activity, cost-effectiveness, and compatibility with a wide range of substrates. Composite catalysts enhance isocyanate yield by introducing a second component to adjust the active metal composition. The central research direction aims to optimize catalyst adaptation to reaction conditions, including temperature, pressure, time, and solvent, to achieve high raw material conversion and product yield.

Synthesis mechanism of dimethylhexane-1,6-dicarbamate from 1,6-hexamethylenediamine, urea and methanol: A molecular scale study based on density functional theory

This work provides a molecular scale insight into non-phosgene synthesis based on the reaction of dimethylhexane-1,6-dicarbamate from 1,6-hexamethylenediamine, urea and methanol with computational electronic method. By exploring almost all possible reaction modes and comparing the effective barrier of each channel, this work analyzes the optimal reaction mechanism for both non-catalytic and self-catalytic systems. The mechanism without catalysis has a high effective free energy barrier (FEB) of 47.0 kcal mol^-1. As for self-catalytic system, after sorting out the reaction pathway network, an effective FEB of 24.6 kcal mol^-1 is confirmed which corresponds to dissociation of urea.

Ameliorating end-product inhibition to improve cadaverine production in engineered Escherichia coli and its application in the synthesis of bio-based diisocyanates

Cadaverine is an important C5 platform chemical with a wide range of industrial applications. However, the cadaverine inhibition on the fermenting strain limited its industrial efficiency of the strain. In this study, we report an engineered Escherichia coli strain with high cadaverine productivity that was generated by developing a robust host coupled with metabolic engineering to mitigate cadaverine inhibition. First, a lysine producing E. coli was treated with a combination of radiation (ultraviolet and visible spectrum) and ARTP (atmospheric and room temperature plasma) mutagenesis to obtain a robust host with high cadaverine tolerance. Three mutant targets including HokD, PhnI and PuuR are identified for improved cadaverine tolerance. Further transcriptome analysis suggested that cadaverine suppressed the synthesis of ATP and lysine precursor. Accordingly, the related genes involved in glycolysis and lysine precursor, as well as cadaverine exporter was engineered to release the cadaverine inhibition. The final engineered strain was fed-batch cultured and a titer of 58.7 g/L cadaverine was achieved with a yield of 0.396 g/g, both of which were the highest level reported to date in E. coli. The bio-based cadaverine was purified to >99.6% purity, and successfully used for the synthesis of polyurethane precursor 1,5-pentamethylene diisocyanate (PDI) through the approach of carbamate decomposition.

Recovery of the polymers formed during thermal cracking of N-substituted dicarbamates over Fe–Ni/Al2O3

Regenerated carbamate from the thermal cracking polymers via the alcoholysis reaction in the presence of ethyl carbamate.

Methoxycarbonylation of 1,6-hexanediamine with dimethyl carbonate to dimethylhexane-1,6-dicarbamate over Zn/SiO2 catalyst

The activated Zn(OAc)₂ in Zn/SiO₂ catalysts facilitates the activation of DMC which leads to better catalytic performance.

Lignocellulosic biomass: a sustainable platform for the production of bio-based chemicals and polymers

The ongoing research activities in the field of lignocellulosic biomass for production of value-added chemicals and polymers that can be utilized to replace petroleum-based materials are reviewed.