Synthesis of dimethyl hexane-1,6-diyldicarbamate from 1,6-hexamethylenediamine and methyl carbamate using lead dioxide as catalyst

A series of metal oxides and lead compounds were employed as catalysts for the methoxycarbonylation of 1,6-hexamethylenediamine (HDA) with methyl carbamate (MC) to produce dimethyl hexane-1,6-diyldicarbamate (HDC). Lead-containing compounds showed excellent catalytic behavior, 100% conversion of HDA and 93% yield of HDC could be achieved with lead dioxide (PbO2) as catalyst at 463 K for 6 h in the first cycle, then it goes down to 72%. The X-ray diffraction (XRD) and Infrared spectrum (IR) characterization results indicated that PbO2 catalyst has been converted into lead carbonate (PbCO3) through intermediate dilead oxide carbonate (Pb2OCO3) in the reaction process. This conversion may be the reason for the reduction of PbO2 catalytic activity.

Graphical abstractXRD patterns of the used PbO2 catalyst with recycling.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► PbO2 was selected from a series of metal oxides and leas compounds to catalyze synthesis of HDC from MC and HDA. ► HDC yield could reach 93% with HDA conversion of 100%. ► PbO2 catalyst converted into PbCO3 through intermediate Pb2OCO3 in the reaction process.