Direct synthesis of dimethyl toluene - 2,4 - dicarbamate from 2,4 - toluene diamine, urea, and methanol / Xinqiang Zhao in Industrial & engineering chemistry research, Vol. 50 N° 24 (Décembre 2011)  

Public ISBD [article]  inIndustrial & engineering chemistry research > Vol. 50 N° 24 (Décembre 2011) . - pp. 13636–13641 Titre : Direct synthesis of dimethyl toluene - 2,4 - dicarbamate from 2,4 - toluene diamine, urea, and methanol Type de document : texte imprimé Auteurs : Xinqiang Zhao, Auteur ; Na Wang, Auteur ; Yanlou Geng, Auteur Année de publication : 2012 Article en page(s) : pp. 13636–13641 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Dimethyl Toluene Dicarbamate Résumé : Dimethyl toluene-2,4-dicarbamate (TDC) was directly synthesized from 2,4-toluene diamine (TDA), urea, and methanol in order to overcome the drawbacks of other technological routes to TDC. First the thermodynamic analysis for this reaction was made and the results show that the reaction is endothermic and can occur spontaneously beyond 413.8 K. Then the effects of catalyst and reaction conditions were studied. TDA conversion of 98.8% and TDC selectivity of 41.6% were attained in the presence of zinc chloride catalyst and under the suitable conditions of molar ratio of TDA/zinc chloride/urea/methanol = 1/0.07/5/80, reaction temperature of 190 °C, reaction pressure of 3.0 MPa, and reaction time of 9 h. Low TDC selectivity is attributed to the difficulty in the conversion of the intermediates, methyl 2-methyl-5-amino N-phenylcarbamate (TMC1) and methyl 3-amino-4-methyl-N-phenylcarbamate (TMC2), to TDC. Finally on the basis of analyses of HPLC–MS, HPLC, and GC, three possible reaction paths were proposed. One path is the reaction of TDA with urea to toluene-2,4-bisurea (TBU) and then the formation of TDC from the succeeding reaction of TBU with methanol. Another path is the generation of TMC1 and TMC2 from the reaction of TDA with first urea and then methanol, and the succeeding reaction of the formed TMC1 and TMC2 with first urea and then methanol to TDC. Still another path is the formation of methyl carbamate (MC) by the reaction of urea and methanol and then the reaction of TDA with MC to TMC1 and TMC2, and finally a further reaction of TMC1 and TMC2 with MC to TDC. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie201891p [article] Direct synthesis of dimethyl toluene - 2,4 - dicarbamate from 2,4 - toluene diamine, urea, and methanol [texte imprimé] / Xinqiang Zhao, Auteur ; Na Wang, Auteur ; Yanlou Geng, Auteur . - 2012 . - pp. 13636–13641. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 24 (Décembre 2011) . - pp. 13636–13641 Mots-clés : Dimethyl Toluene Dicarbamate Résumé : Dimethyl toluene-2,4-dicarbamate (TDC) was directly synthesized from 2,4-toluene diamine (TDA), urea, and methanol in order to overcome the drawbacks of other technological routes to TDC. First the thermodynamic analysis for this reaction was made and the results show that the reaction is endothermic and can occur spontaneously beyond 413.8 K. Then the effects of catalyst and reaction conditions were studied. TDA conversion of 98.8% and TDC selectivity of 41.6% were attained in the presence of zinc chloride catalyst and under the suitable conditions of molar ratio of TDA/zinc chloride/urea/methanol = 1/0.07/5/80, reaction temperature of 190 °C, reaction pressure of 3.0 MPa, and reaction time of 9 h. Low TDC selectivity is attributed to the difficulty in the conversion of the intermediates, methyl 2-methyl-5-amino N-phenylcarbamate (TMC1) and methyl 3-amino-4-methyl-N-phenylcarbamate (TMC2), to TDC. Finally on the basis of analyses of HPLC–MS, HPLC, and GC, three possible reaction paths were proposed. One path is the reaction of TDA with urea to toluene-2,4-bisurea (TBU) and then the formation of TDC from the succeeding reaction of TBU with methanol. Another path is the generation of TMC1 and TMC2 from the reaction of TDA with first urea and then methanol, and the succeeding reaction of the formed TMC1 and TMC2 with first urea and then methanol to TDC. Still another path is the formation of methyl carbamate (MC) by the reaction of urea and methanol and then the reaction of TDA with MC to TMC1 and TMC2, and finally a further reaction of TMC1 and TMC2 with MC to TDC. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie201891p

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