Novel TaPO5−xN2x/3 oxynitrides

Transesterification of vegetable oils by AlPOxNy heterogeneous catalysts

“…Amorphous citrate route. The citrate route is also a method of interest to prepare high specific surface area phosphate precursors [27]. Aqueous solutions of aluminum chloride and ammonium dihydrogen phosphate corresponding to anAl/P ratio = 1 were mixed under stirring.…”

“…The EDX analysis system works as an integrated feature of a scanning electron microscope (JEOL JSM 6400). 27 Al NMR was set to 12 KHz with a /16 pulse and a 0.5 sec delay between two pulses. An aluminum nitrate solution was used as a reference for the chemical shifts.…”

“…Due to the amorphous feature of the samples, NMR 31 P and 27 Al analyses were undertaken to characterize any modification of the aluminum and phosphorus environments with nitridationin samples listed in Table 1. NMR 27 Al spectrum of AlPO 4 displays a major peak at 40 ppm and a second one less intensive at -10 ppm, as well as a shoulder at 10 ppm ( Figure 2). According to different authors, the main peak is attributed to aluminum in tetrahedral environment [36][37][38][39][40].…”

“…% nitrogen[22] and assigned to a nitrided aluminum tetrahedral environment.An attempt to deconvoluate the signal of this sample gives the following quantitative distribution:10-15% (52 ppm), 25-30% (30 ppm) and 60% (-10 ppm). But it is not obvious to do a simple determination with such a quadrupolar27 Al nuclei and the presence of asymmetric peaks. This result needstherefore to be taken with precaution.…”

“…P and27 Al NMR studies show that phosphorus and aluminum atoms are mainly in tetrahedral sites of the "AlPON" structure. The progressive nitridation of AlPO 4 results in the shift of the resonance peaks towards higher chemical shifts, a typical feature encountered with nitrogen insertion.AlPO 4 used as an acid catalyst provided the best catalytic activity compared to nitrided phosphates.…”