Reaction Of Phosgene Research Articles

Study on reactivity characteristic of TDA droplet group with gaseous phosgene for preparing TDI

Toluene diisocyanate stands as a pivotal chemical, predominantly synthesized through the phosgenation reaction between toluene diamine and phosgene. To address the inherent limitations of existing phosgenation methods, we pioneered a novel phosgenation reaction based on flash atomization and confirmed its feasibility with preliminary theoretical calculations. This manuscript delves deeper into the superiority of this method and refines its reaction parameters. By integrating the discrete phase model with the Eulerian model, we studied the reaction dynamics of droplet sprays, exploring the effects of spray velocity, droplet size, phosgene temperature, and particle size distribution on the reaction. Our results highlight that, with a mean droplet diameter of 70 μm and a spray velocity of 40 m/s, an impressive reaction yield of 97.4 % can be achieved. This research enriches our understanding of the gas–liquid two-phase phosgenation method, setting the stage for its future exploration and potential applications in Toluene diisocyanate and other isocyanate industry.

Photo-on-Demand In Situ Phosgenation Reactions That Cross Three Phases of a Heterogeneous Solution of Chloroform and Aqueous NaOH.

Here, we report a novel photo-on-demand in situ phosgenation reaction that crosses three phases of a heterogeneous solution of chloroform (CHCl3) and aqueous NaOH containing an aryl alcohol or amine. This reaction system enables the safe, convenient, and inexpensive synthesis of carbonate esters, polycarbonates, and N-substituted ureas from aryl alcohols, aryl diols, and primary/secondary amines, respectively, on a practical scale and with good yield. The photochemical oxidation of CHCl3 to phosgene (COCl2) occurs upon irradiation with UV light from a low-pressure mercury lamp of both the gas and liquid phases of the reaction system under O2 bubbling of the vigorously stirred sample solution. The following reaction mechanisms are suggested: The aryl alcohol reacts in situ with the generated COCl2 at the interfaces of the organic/aqueous phases and aqueous/gas phases, in competition with the decomposition of COCl2 due to hydrolysis. Nucleophilicity and hydrophilicity are enhanced by the formation of aryl alkoxide ion through the reaction with NaOH, whereas the reaction of amine proceeds through neutralization of the generated HCl by the aqueous NaOH.

Photo-On-Demand Synthesis of α-Amino Acid N-Carboxyanhydrides with Chloroform.

Amino acid N-carboxyanhydrides (NCAs) are conventionally synthesized from α-amino acids and phosgene. The present study reports in situ photo-on-demand phosgenation reactions of amino acids with CHCl3 for synthesizing NCAs. A series of NCAs were obtained on a gram scale upon photo-irradiation of a mixture solution of CHCl3 and CH3CN containing an amino acid at 60-70 °C under O2 bubbling. This method presents a safe and convenient reaction controlled by light without special apparatuses and reagents.

Synthesis of sustainable production chains for phosgene-related byproducts

Phosgenation reactions are accompanied by the formation of the byproduct hydrogen chloride, as well as the production of carbon dioxide. Byproduct recovery and valorization may have implications for resource recovery and elimination of pollutive practices. However, phosgene-related byproducts with respect to resource utilization, environmental performance, and techno-economic issues are yet to be investigated using a proactive and integrated approach. This study aims to systematically investigate the comprehensive utilization of phosgenation reaction byproducts. Different detailed utilization routines are proposed. The hydrogen chloride processing methods were evaluated and compared in terms of equipment investment, operation cost, waste discharge, and profit. The results show that, based on the processing of 1 t of hydrogen chloride, polyvinyl chloride, and epichlorohydrin have the best economic benefits, which are CNY 1418.73 and CNY 1463.22, respectively. However, they are wastewater-intensive. The operation cost of preparing hydrochloric acid and the amount of wastewater (CNY 305.72 and 0.028 t, respectively) are both less than that of alkali neutralization (CNY 3903.92 and 3.718 t, respectively). This study establishes an industrial chain scheme for phosgene-related byproducts that meet the requirements of a circular economy to achieve environmental sustainability.

Photo-on-demand Phosgenation Reactions with Chloroform Triggered by Cl2 upon Irradiation with Visible Light: Syntheses of Chloroformates, Carbonate Esters, and Isocyanates

Chloroform (CHCl3) upon bubbling with O2 containing ∼2% Cl2 underwent oxidative photochemical conversion to phosgene (COCl2) when exposed to a white LED light. Cl2 may serve as a visible light-responsive radical initiator in the radical chain reactions of CHCl3 and O2. This photochemical reaction allowed both in situ and stepwise one-pot phosgenation reactions, which are simple and safe methods, without expensive apparatus. It can be applied to a variety of conventional organic syntheses using phosgene and phosgene oligomers.

Simulation and optimization of the thermally coupled reactive distillation column for producing toluene diisocynate

AbstractToluene diisocyanate is an important chemical intermediate prepared by phosgenation reaction with two steps named cold and thermal phosgenation, respectively. The thermal phosgenation reaction is a complex reactive distillation process with high energy consumption and multiple targets of reaction and separation, so it is of great significance to optimize the step. The reactive distillation model of the thermal phosgenation was established for an industrial installation by aspen plus, and the effects of the different parameters of temperatures, residence times, etc., were investigated firstly; then a thermally coupled reactive distillation column was presented to perform the thermal phosgenation process, and the optimal operation and configuration parameters were obtained by simulation. The results showed that the proposed process can save the heat and cold energy with 7.29% and 32.78%, respectively, and reduce the total annual cost by about 17.11%.

Photo-on-Demand Phosgenation Reactions with Chloroform for Selective Syntheses of N-Substituted Ureas and Isocyanates.

Two new reaction processes involving the in situ oxidative photochemical conversion of CHCl3 to COCl2 allowed selective syntheses of N-substituted ureas and isocyanates from amines. (I) A CHCl3 solution containing an amine and an organic base under O2 bubbling provided the urea derivative under exposure to UV light generated from a low-pressure mercury lamp at 20–40 °C. (II) A two-step reaction involving the oxidative photodecomposition of CHCl3 at lower temperatures and subsequent sequential injections of an amine and organic base into the sample solution provided the isocyanate in high yield. The reaction processes of (I) and (II) capitalize on the solution conditions of [COCl2] < [amine] and [COCl2] > [amine], respectively, to result in 1:2 and 1:1 reactions. In general, isocyanates, especially aromatic and haloalkyl ones, readily undergo hydrolysis in the presence of an organic base. However, with the advantage of synthesizing the isocyanates in CHCl3 solvent, direct addition of monoalcohols and diols to the as-prepared sample solution containing the diisocyanate allowed the one-pot syntheses of biscarbamates and polyurethanes, respectively. The reactions developed in this study are simple, safe, and inexpensive methods of synthesizing N-substituted ureas and isocyanates, and derivatives of isocyanates such as carbamates and polyurethanes. The present new methods can replace current synthetic methods using COCl2 in both academia and industry.

Ruthenium(II) Polypyridine Complex-Based Aggregation-Induced Emission Luminogen for Rapid and Selective Detection of Phosgene in Solution and in the Gas Phase.

A bis-heteroleptic ruthenium(II) complex, Ru-1, of 4,7-bis(2-aminoethylamino)-1,10-phenanthroline for selective "turn-on" detection of highly toxic chemical warfare agent phosgene is presented. Probe Ru-1 exhibits aggregation-induced emission (AIE), and the restricted intramolecular motion is responsible for the AIE activity. In a CHCl3/CH3CN [95:5 (v/v)] solvent mixture, a unique self-assembled vesicular structure was formed after aggregation, which was supported by transmission electron microscopy, field emission scanning electron microscopy, and atmoic force microscopy studies. Probe Ru-1 showed a rapid and highly selective luminescence turn-on response for phosgene over other competitive chemical warfare agents with a low detection limit (13.9 nM) in CH3CN. The 2-aminoethylamino groups in Ru-1 act as a reacting site for nucleophilic addition to the carbonyl center of phosgene and undergo intramolecular cyclization. The final product of the phosgene-mediated reaction, Ru-1-Phos, contains 2-imidazolidinone groups, which has been confirmed by electrospray ionization mass spectometry and 1H nuclear magnetic resonance (NMR) spectroscopy. 1H NMR titration of Ru-1 with phosgene supported the reaction mechanism and also pointed to the simultaneous reaction of phosgene at two 2-aminoethylamino sites. For the first time, the crystal structure of the phosgene reaction product, Ru-1-Phos, containing the cyclized 2-imidazolidinone group was confirmed by single-crystal X-ray diffraction, which indubitably validates the reaction mechanism. Triplet state time-dependent density functional theory calculations showed that the weak luminescence of Ru-1 was mostly due to the population of the non-emissive 3MC state. The cyclization reaction with phosgene and the corresponding 2-imidazolidinone product formation populated the emissive 3MLCT state in Ru-1-Phos and is the key reason for the enhanced luminescence. Furthermore, a low-cost portable test paper strip has been fabricated with Ru-1 for the real-time selective monitoring of phosgene gas at the nanomolar level.

An effective synthesis of bio-based pentamethylene diisocyanate in a jet loop reactor

A highly efficient jet loop reactor (JLR) with a submerged nozzle was developed to enhance the mixing and dispersion capacity of a phosgenation reaction, which was implemented in the preparation of pentamethylene diisocyanate (PDI). Model test of air–water two-phase flow was carried out first, which provided references for the control conditions of the phosgenation of 1,5-pentanediamine (PDA). Carbon dioxide (CO2) was used to protect PDA as 1,5-pentanediamine carbonate (PDAC). Both the carbonate-forming and phosgenation reactions were preferably carried out in the JLR. The phosgene inlet pressure, asynchronous speed of the circulating pump, PDI content, and reaction completion time in the JLR system were investigated. Interestingly, we found that the PDI content exceeded 0.6–0.7%, the yields of PDI exceeded 7–8.5%, and the reaction time was decreased by approximately 50% compared to that of the traditional stirred-tank reactor (STR). The JLR is thus applicable for the preparation of PDI and is superior to the STR system.

A Crystallographic, Spectroscopic, and Computational Investigation of Carbonyl and Oxalyl Diisothiocyanate.

Carbonyl diisothiocyanate (1) and oxalyl diisothiocyanate (2) were synthesized by reactions of phosgene and oxalyl chloride with ammonium thiocyanate, respectively. Their structures were elucidated by single-crystal X-ray diffraction. 1 exhibits weak intermolecular S-O contacts forming a loosely connected network of molecules, whereas 2 exhibits weak intermolecular Ccarbonyl-O contacts resulting in the formation of layers. Both compounds were further characterized by nuclear magnetic resonance, infrared, and Raman spectroscopy. Quantum-chemical calculations reproduced the experimental structures and enabled the interpretation of the vibrational spectra.

Design and control of an energy-saving phosgenation reaction distillation for toluene diisocyanate

In this paper, the conventional reactive distillation (CRD) of toluene diisocyanate (TDI) production process is designed and optimized by minimizing the total annual cost (TAC). In order to make the HCl content in the side stream of the reactive distillation correspond with the specifications of the CRD process, a lot of energy needs to be consumed. Therefore, a reactive distillation dividing-wall column (RD-DWC) is comparatively proposed. The results illustrate that compared with CRD process, the TAC and energy consumption of RD-DWC process decreases by 40.625% and 46.038%, respectively. Apart from that, the RD-DWC will also improve the safety of the TDI production process. During the design process, the control of CCA conversion rate of reactive column is a key factor for achieving this process efficient. Furthermore, a feasible control scheme is investigated. Specifically, the residence time is controlled by liquid level for the reactive distillation that could obviously reduce the generation of by-products. This control scheme can effectively control the process and achieve good dynamic performance when ±10% flow rate and feed composition disturbances are introduced. Research on control performance is significant to develop energy saving technology for RD-DWC process.

Design of a Flow Reactor System for Safe Handling of Phosgenation Reactions: Scale-Up Study of T-Shaped Mixers for Industrial Chemical Production

Design of a Flow Reactor System for Safe Handling of Phosgenation Reactions: Scale-Up Study of T-Shaped Mixers for Industrial Chemical Production

A naphthalimide-based probe for phosgene sensing based on the phosgene-induced beckmann rearrangement

A new probe for selective and sensitive phosgene sensing in acetonitrile was developed. The sensing mechanism was based on the mechanism of the phosgene-induced Beckmann rearrangement of the naphthalimide fluorophore. An electron-withdrawing ketoxime, which was used as the phosgene receptor, was attached to the 4-position on the 1,8-naphthalimide chromophore to constituted a nonfluorescent probe. The reaction of phosgene with ketoxime induced a Beckmann rearrangement, which was followed by conversion of the nonfluorescent probe into the 4-acetamido-1,8- naphthalimide fluorophore, which emits bright blue fluorescence at 488 nm. The probe exhibited a detection limit of 6.3 nM for phosgene. In addition, the probe-loaded filter stripe for successful monitoring of gaseous phosgene was also demonstrated.

A theoretical study on the phosgenation of methylene diphenyl diamine (MDA)

G3MP2B3 calculations were used to investigate the mechanism of the phosgenation reactions of 4,4′-methylenedianiline (MDA) resulted in the formation of methylene diphenyl diisocyanate (MDI). Due to o-dichlorobenzene solvation the reaction barriers are dramatically reduced compared to the gas phase reaction mechanism. The mechanisms of the ‘phosgenations first’ and ‘stepwise phosgenations’ are energetically compared. Standard enthalpy of formation for MDI (14.8 ± 5.2 kJ/mol) and the group additivity increments for OCN and NHCOCl groups linked to phenyl ring are proposed (Δf,iH0(-NCO) = −61.2 kJ/mol and Δf,iH0(-NHCOCl) = −195.0 kJ/mol). A thermodynamic stabile charge separated amine hydrochloride intermediate can mask the amine toward phosgene.

Safe and Efficient Phosgenation Reactions in a Continuous Flow Reactor

Phosgene is widely used in organic synthesis owing to its high reactivity, utility, and cost efficiency. However, the use of phosgene in batch processes on the industrial scale is challenging owing to its toxicity. An effective method to minimize reaction volumes and mitigate the safety risks associated with hazardous chemicals is the use of flow reactors. Consequently, we have established a flow reaction system using triphosgene and tributylamine, which affords a homogeneous reaction that avoids clogging issues. In addition, we have demonstrated that this methodology can be applied to a wide variety of phosgene reactions, including the preparation of pharmaceutical intermediates, in good to excellent yields.

New poly(ester urea) derived from L-leucine: electrospun scaffolds loaded with antibacterial drugs and enzymes.

Electrospun scaffolds from an amino acid containing poly(ester urea) (PEU) were developed as promising materials in the biomedical field and specifically in tissue engineering applications. The selected poly(ester urea) was obtained with a high yield and molecular weight by reaction of phosgene with a bis(α-aminoacyl)-α,ω-diol-diester monomer. The polymer having L-leucine, 1,6-hexanediol and carbonic acid units had a semicrystalline character and relatively high glass transition and melting temperatures. Furthermore it was highly soluble in most organic solvents, an interesting feature that facilitated the electrospinning process and the effective incorporation of drugs with bactericidal activity (e.g. biguanide derivatives such as clorhexidine and polyhexamethylenebiguanide) and enzymes (e.g. α-chymotrypsin) that accelerated the degradation process. Continuous micro/nanofibers were obtained under a wide range of processing conditions, being diameters of electrospun fibers dependent on the drug and solvent used. Poly(ester urea) samples were degradable in media containing lipases and proteinases but the degradation rate was highly dependent on the surface area, being specifically greater for scaffolds with respect to films. The high hydrophobicity of new scaffolds had repercussions on enzymatic degradability since different weight loss rates were found depending on how samples were exposed to the medium (e.g. forced or non-forced immersion). New scaffolds were biocompatible, as demonstrated by adhesion and proliferation assays performed with fibroblast and epithelial cells.

A Method to Predict Phosgenation Reaction Performance To Produce Toluene Diisocyanate in Jet Reactors

Toluene diisocyanate (TDI) is a widely used intermediate in the production of polyurethanes. Phosgenation reaction is the most important operation in the process of producing TDI, which is commonly performed in a jet reactor. Because of the high toxicity of phosgene, it is unpractical to evaluate the performance of the reaction by sampling intermediate products. To overcome this difficulty, first, a mapping table was created for reaction path and temperature. Next, various parameters that affect temperature, such as reaction path, ratio of phosgene, diethyl iso-phthalate (DEIP), etc. were investigated by simulation studies. The results show that the ratio of phosgene is the most important parameter. On the basis of the mapping table, easily available experimental reaction temperature data can be utilized to infer the reaction path, and consequently the performance of jet reactor can be predicted. The method was validated after being used in an experimental setup of 1000 tons/annum TDI capacity.

ChemInform Abstract: Phosgenation Reactions with Phosgene from Triphosgene

AbstractReview: 29 refs.

Continuous in situ generation and reaction of phosgene in a microflow system

Continuous in situ generation of phosgene and its use in acid chloride formation in a microflow system were demonstrated. The acid chloride was subsequently coupled with an amine in high yield without severe epimerization.

Solvent-Free and Safe Process for the Quantitative Production of Phosgene from Triphosgene by Deactivated Imino-Based Catalysts

Phosgene is quantitatively formed from solid triphosgene in a solvent-free and safe process without any reaction heat, catalyzed by planar N-heterocycles with deactivated imino functions. The rate of phosgene generation is adjustable to the rate of phosgene consumption in the subsequent phosgenation reaction by thermal control, catalyst concentration, and in some cases, specific properties of selected metal phthalocyanines. A thermal runaway reaction of this process is impossible.