Modeling of Isocyanate Synthesis by the Thermal Decomposition of Carbamates

Abstract

The presented work is devoted to isocyanate synthesis by the thermal decomposition of carbamates model. The work describes the existing isocyanate-obtaining processes and the main problems in the study of isocyanate synthesis by the thermal decomposition of carbamates, which can be solved using mathematical and computer models. Experiments with carbamates of various structures were carried out. After processing the experimental data, the activation energy and the pre-exponential factor for isocyanate synthesis by the thermal decomposition of carbamates were determined. Then, a mathematical model of the reactor for the thermal decomposition of carbamates using the COMSOL Multiphysics software was developed. For this model, computational experiments under different conditions were carried out. It was shown that the calculation results correspond to the experimental ones, so the suggested model can be used in the design of the equipment for isocyanate synthesis by the thermal decomposition of carbamates.

How To Get Isocyanate?

“…While carbamate thermal decomposition reactions can also occur in the gas phase, 70 the requisite reaction temperatures generally range from 350 to 550 °C. These high temperatures accelerate raw material decomposition, resulting in elevated equipment costs, increased energy consumption, and greater byproduct formation, which diminish isocyanate selectivity.…”

Polymers without Petrochemicals: Sustainable Routes to Conventional Monomers

“…Carbamates, also known as urethanes, are key intermediates in isocyanate synthesis, and can also be directly converted to polyurethanes via transesterification with a diol, bypassing the need for diisocyanates . Previously, silanes and boron halogenides were used as catalysts, limiting the reaction scale due to toxicity and high prices, and aliphatic carbamates were avoided due to side reactions in the thermal fragmentation. , Recently, the conversion of carbamates to isocyanates via thermal decomposition was modelled, although this focused on the preparation of mono-isocyanates, and the authors note that many industrial patents exist concerning this process, suggesting companies have calculated the process to be commercially viable . Carbamates have traditionally been produced from alcohols and amines with phosgene derivatives, such as chloroformates, which is suitable for lab-scale peptide chemistry but not appropriate for large-scale synthesis .…”

“…1258,1268 Recently, the conversion of carbamates to isocyanates via thermal decomposition was modelled, although this focused on the preparation of mono-isocyanates, and the authors note that many industrial patents exist concerning this process, suggesting companies have calculated the process to be commercially viable. 1269 Carbamates have traditionally been produced from alcohols and amines with phosgene derivatives, such as chloroformates, which is suitable for lab-scale peptide chemistry but not appropriate for large-scale synthesis. 1259 Three well-known rearrangements enable carbamate produc-tion from carboxylic acids; the Curtius rearrangement of acyl azides, the Lossen rearrangement of hydroxamic acids and the Hoffman rearrangement of carboxamides.…”

Synthesis of organic carbamates as polyurethane raw materials from CO2: the quest for metal alkoxides as regenerable reagents

“…By contrast, Ti(O n Bu) 4 is a more suitable for this purpose because it can be regenerated using n BuOH that can be obtained via the pyrolysis of butyl carbamate in the isocyanate production process, as shown in Scheme 2. [21][22][23][24] However, considering the efficiency of the isocyanate production process by pyrolysis of organic carbamates, it is clear that methyl carbamates can be cracked at lower energy and cost than butyl carbamates due to the difference in the boiling points of the corresponding alcohols that must be removed. To reduce CO 2 emission, energy consumption must be reduced as much as possible.…”

“…Instead, a stepwise isocyanate synthesis method has been proposed, in which organic carbamates (RNHCOOR′) are synthesized from CO 2 and amines, followed by the pyrolysis of the carbamates (Scheme 2, red text and arrow). 13,[21][22][23][24][25] Considering that alcohol is a by-product in the process of obtaining isocyanates from organic carbamates, it would be ideal to synthesize organic carbamates from the dehydration reaction of amine, CO 2 , and alcohol, assuming that the alcohol is recovered and reused. However, it is known that the dehydration reaction of amine, CO 2 , and alcohol is thermodynamically unfavorable (Scheme 3a).…”