A Semi‐continuous Process for the Synthesis of Methyl Carbamate from Urea and Methanol

Abstract

A semicontinuous process for the synthesis of methyl carbamate from urea and methanol was investigated in the autoclave without the catalyst. Some significant parameters were determined in terms of the methyl carbamate yield. The optimal reaction conditions were found at an initial molar ratio of methanol/urea of 6:1, a reaction temperature of 423 K, a flow rate of fresh methanol at 4 mL/min, a stirring speed of 800 rpm and a reaction time of 6 hours, respectively. A MC yield of 98.7 % was obtained at the optimal reaction conditions. Furthermore, the kinetics of this reaction were researched and the reaction activation energy was obtained as 110.498 kJ/mol. It was demonstrated that removing methanol containing ammonia from the autoclave and replacing it with continuously feeding fresh methanol resulted in a higher reaction rate and a high MC yield.

One-Pot Synthesis of Dialkyl Hexane-1,6-Dicarbamate from 1,6-Hexanediamine, Urea, and Alcohol over Zinc-Incorporated Berlinite (ZnAlPO4) Catalyst

“…The selectivities to both 3 and 4 increased gradually with urea/HDA molar ratios rising from 2.0:1 to 3.0:1, while that for both 1 and hexane-1,6-diurea (5) first increased with urea/HDA molar ratios rising from 2.0:1 to 2.2:1, and then followed by a decrease at urea/HDA molar ratio higher than 2.2. The reason could be due to the rate of both 3 and 4 production from Reactions (1) and (2) [24,25], being higher with an increase of urea/HDA molar ratio from 2.0 to 3.0 than that of the consumption from Reactions (3), (4), (5) and (6), respectively. On the other hand, for both 1 and 5, the rate of production from Reactions (3), (4) and (7) [20,26], were lower at the urea/HDA molar ratio higher than 2.2 than that of consumption from Reactions (8) and (9), respectively.…”

“…The selectivities for 3 and 4 increased for butanol/HDA molar ratios over the range of 2:1 to 9:1, while that for 5 decreased, and that for 1 remained unchanged. The reason could be due to the rate of both 3 and 4 production from Reactions (1) and (2) [24,25], being, respectively, higher with the increase of butanol/HDA molar ratio from 2.0 to 9.0 than that of consumption from Reactions (3), (4), (5) and (6). For 5, the rate of production from Reaction (7) was lower than that of consumption from Reaction (9) [20,26].…”

“…At the same time, the catalytic formation of both 3 and 5 via reaction of urea by alcoholysis and ammonolysis, respectively, have also been developed [19,24,25]. In other words, during the one-pot synthesis of dibutyl hexane-1,6-dicarbamate from HDA, urea and butanol, there may be two different reaction intermediates, i.e.…”

Novel process for synthesis of 1,1,3,3-tetrabutyl-1-methoxy-3-isocyanatodistannoxane

“…Some researchers disclosed the new process that DMC can be synthesized in a two step reaction from urea and methanol via methyl carbamate (MC) intermediate [12][13][14][15]. …”

“…Dibutyldimethoxytin, dibutylisocyanatomethoxytin and TBMI have similar activity and are more active than dibutyloxotin for the synthesis of DMC. They are also suitable for various other applications such as transesterification, esterification and transamination [13][14][15][16][17].…”