The heterogenation of melamine and its catalytic activity

The immobilization of melamine (Mela) onto silica extracted from rice husk ash (RHA) has been done via 3-chloropropyltriethoxysiline (CPTES). The resulting catalyst was designated as RHAPrMela. The melamine loading on the silica was found to be ca. 65.74%. The 29Si MAS NMR showed the presence of T2, T3, Q3 and Q4 silicon centers. The 13C MAS NMR showed that RHAPrMela had three chemical shifts at 14.83, 31.17 and 52.24 ppm, consistent with the three carbon atoms, and two chemical shifts at 161.52 and 169.67 ppm with double spinning side bands, indicating that the three carbon atoms in melamine ring are not equivalent in RHAPrMela. The catalytic potential of RHAPrMela was tested for the esterification of acetic acid with several alcohols. A conversion of 73% was achieved with 100% selectivity for the respective esters. The catalyst was easily regenerated and could be reused many times without loss of catalytic activity.

The melamine molecule has been immobilized onto silica to form RHAPrMela. The nitrogen atoms were believed to be involved in the reaction mechanism for the esterification of ethyl alcohol with acetic acid. Several other alcohols were also studied with the same catalyst. A conversion of 73% was achieved with 100% selectivity for the respective esters.Figure optionsDownload high-quality image (59 K)Download as PowerPoint slide