Carbon2Polymer – Chemical Utilization of CO₂ in the Production of Isocyanates

Abstract

CO2 was investigated as carbon source for the synthesis of the polymer precursor toluene‐2,4‐diisocyanate (TDI). A four‐step synthesis was envisaged. The first step, i.e., the Ru‐catalyzed CO2 hydrogenation to [HCOOH·amine] adducts, was carried out under biphasic conditions allowing for straightforward reutilization of the catalyst phase. The investigation of the second step, the esterification of formic acid with methanol to yield methyl formate (MF), is ongoing with a strong focus on the integration with the hydrogenation step. The potential hazards of the third step, the Pd‐catalyzed oxidative carbonylation of toluene‐2,4‐diamine with MF, have been addressed developing a sophisticated protocol for a safe operation with organics/CO/O2 mixtures. For the final step, the carbamate cleavage of toluene‐2,4‐dicarbamate (TDC) towards TDI, monofunctional model substrates and TDC were cleaved in the presence of bifunctional catalysts. The obtained kinetic data allowed to implement the reaction in a continuous stirred‐tank reactor and will serve as starting point for further process optimization.

Methylformate from CO2: an integrated process combining catalytic hydrogenation and reactive distillation

“…To achieve preferential partitioning of the catalyst in the n-decane phase, the solubility properties of the catalyst must be adjusted accordingly. The complex cis-[Ru (dppm) 2 Cl 2 ] 37 (dppm = Ph 2 P-CH 2 -PPh 2 ) is a powerful catalyst for CO 2 hydrogenation to FA 38,39 and thus was selected as lead structure for tagging with long alkyl chains at the aryl groups. The ligand synthesis starts from commercially available bromo aryl compounds bearing an octyl or a dodecyl chain in para-position.…”

“…2). Initially, methyl diethanolamine (MDEA), successfully used in biphasic organic/water systems for stabilizing FA, 38,39 was chosen to validate the approach. Catalytic hydrogenation of CO 2 using complex 1 was carried out under a standard set of reaction conditions and the stability of the catalyst system was tested by repetitive batch recycling of the alkane phase ( Table 1).…”

“…5). 39 The set-up comprises a 900 mL high pressure reservoir containing a CO 2 -saturated solution of 1,2-DMI in MeOH. This is placed on a magnetic stirring plate which is located on a balance to monitor the delivery of feed.…”

Carbon2Polymer: A CO2‐based Route to Polyurethanes via Oxidative Carbonylation of TDA with Methyl Formate

“…The carbamate cleavage of toluene‐2,4‐dicarbamte (TDC) provides a non‐phosgene access to toluene‐2,4‐diisocyanate (TDI), which is utilized in large quantities as the most important building block in polyurethane chemistry . For this reason, effective and environmentally benign methods for the synthesis of N ‐aryl carbamates such as TDC are subject of the joined research project Carbon2Polymer with academic and industrial partners.…”

“…In order to overcome the challenges associated with the low reactivity of CO 2 , the use of carbon dioxide as building block is achieved via an indirect pathway in the Carbon2Polymer project (Fig. ) . As “activated form” of CO 2 , methyl formate (MF) is envisaged, which can be produced by CO 2 hydrogenation with integrated esterification of formic acid (FA) with methanol (step I and II) .…”