CHARACTERIZATION OF THE PRODUCTS REMAINING IN THE SOLID AFTER PARTIAL THERMAL-DECOMPOSITION OF PR4NF-MFI, PR3NHF-MFI, AND PR4NOH-MFI PRECURSORS

Siliceous MFl-type zeolite precursors, containing the templates Pr4NOH (besides other Pr4N+ species), Pr4NF and Pr3NHF (Pr = n-propyl) were submitted to a programmed heating in inert gas atmosphere. After characterization by thermal analysis (t.g., d.t.a., d.s.c.), the samples including the template partly degraded at various temperatures were studied by i.r. and C-13 CP-MAS n.m.r. spectroscopy. For the Pr4NF-MFl precursor, the transformation of Pr4N+ into Pr3NH+ in a first stage corresponding to the first d.t.a. peak (460-degrees-C) was complete, whereas the following transformations into the Pr2NH and PrNH2 species were less clearly separated (second d.t.a. peak at 521-degrees-C). For the Pr3NHF-MFl precursor, the degradation is produced in a narrower and higher temperature range (480-550-degrees-C) with transformation of Pr3NH+ into Pr3N in a first stage. For the Pr4NOH-MFl precursor, the C-13 n.m.r. spectra showed a different behavior. In this case, Pr4N+ remained present until completion of the decomposition (almost-equal-to 450-degrees-C), but in a slightly modified environment. In all cases, when the degradation approaches completion, the formation of various hydrocarbons resulted from the catalytic properties of these materials.