CH3COONa as an effective catalyst for methoxycarbonylation of 1,6-hexanediamine by dimethyl carbonate to dimethylhexane-1,6-dicarbamate

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 decreased slightly with increasing temperature, while that for 5 decreased very slightly over the temperature range 413 to 433 K, and rapidly at the temperature higher than 433 K. This could be due to the fact that a higher temperature accelerates the synthesis of 2 by the above reactions, including Reactions (5), (6) and (9) [17,20,27]. Although a higher conversion of HDA could be attained at high temperatures, a very high temperature reduced the yield of 2, possibly because of the partial decomposition of 2 to 1 [17,27]. Thus, the optimum temperature for the production of 2 from urea, HDA and butanol is around 493 K. Figure 5 presents the effect of reaction temperature on the conversion of HDA, yield of 2, and selectivities for four of the main byproducts under the reaction conditions: HDA 0.9 mol, ZnAlPO 4 3.0 g, butanol 7.74 mol (708.0 mL), urea/HDA molar ratio 2.6, time 6 h and pressure 1.2 MPa.…”

“…With the amount of ZnAlPO 4 catalyst increasing from 3.0 to 3.5 g, the yield of 2 decreased slowly while the selectivity of 1 increased. The reason could be that the decomposition of 2 to 1 is predominant compared with the synthesis of 2 via further reaction of 1, urea, and butanol by Reaction (8) [17,27]. With the amount of ZnAlPO 4 catalyst increasing, the selectivities for both 3 and 4 first increased, followed by a decrease.…”

“…The selectivity for 1 first decreased and then increased, on increasing reaction temperature, and achieved a minimum value at 493 K. This suggests that the activation energy for the formation of 2 is higher than that for 1. The decrease in yield for 2 and the increase in selectivity for 1 at temperatures higher than 493 K may be due to the decomposition of 2 to 1, because 2 as a secondary product can been formed via the further reaction of 1, urea and butanol [17,20,27]. The selectivities to both 3 and 4 decreased slightly with increasing temperature, while that for 5 decreased very slightly over the temperature range 413 to 433 K, and rapidly at the temperature higher than 433 K. This could be due to the fact that a higher temperature accelerates the synthesis of 2 by the above reactions, including Reactions (5), (6) and (9) [17,20,27].…”

“…The decrease in yield for 2 and the increase in selectivity for 1 at temperatures higher than 493 K may be due to the decomposition of 2 to 1, because 2 as a secondary product can been formed via the further reaction of 1, urea and butanol [17,20,27]. The selectivities to both 3 and 4 decreased slightly with increasing temperature, while that for 5 decreased very slightly over the temperature range 413 to 433 K, and rapidly at the temperature higher than 433 K. This could be due to the fact that a higher temperature accelerates the synthesis of 2 by the above reactions, including Reactions (5), (6) and (9) [17,20,27]. Although a higher conversion of HDA could be attained at high temperatures, a very high temperature reduced the yield of 2, possibly because of the partial decomposition of 2 to 1 [17,27].…”

“…For the synthesis of 2, two different reaction routes, i.e., the alkoxycarbonylation of diamines with 3 [17,27] and the alcoholysis of 5 with alcohols [20], have been reported. 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].…”