Quantification of Aluminum Coordinations in Amorphous Aluminas by Combined Central and Satellite Transition Magic Angle Spinning NMR Spectroscopy

Abstract

An amorphous alumina formed by partial dehydration of gibbsite is characterized by observation and simulation of the central and satellite transitions of 27Al magic angle spinning Nh4R spectra. The improved resolution of the Mod, AlOs, and A106 sites in the (f3/2, f ' / 2 ) transitions allows the individual sideband manifolds to be simulated so that the NMR interaction parameters and the distribution of the quadrupolar interaction of each coordination can be deduced. Based on these parameters, simulation of the centerband provides the most accurate information to date on the distribution of aluminum between the three coordinations in an amorphous alumina.

The nature and impacts of fines in smelter-grade alumina

“…gamma-, theta-and alpha-alumina). The peaks centred at a chemical shift of approximately 30 ppm, could either indicate the presence of quasi-octahedral [15,23] or pentahedral (AlO 5 ) aluminium coordination in accordance with previously reported values for the chemical shift [17,24,25]. However, the higher value of C Q and ΔC Q more likely indicates the presence of pentahedral coordination.…”

Solid-state NMR characterisation of the thermal transformation of a Hungarian white illite

“…Both the shift and χ Q of the peak at ~12 ppm are characteristic of a transitional alumina [12,45,46].…”

Do Sodium Oxofluoroaluminates Exist at Room Temperature?

“…In addition to the peaks corresponding to different starting constituents of the mixture, that is, cryolite and α-alumina, we can also detect at least two other signals, with broad quadrupolar line shapes identified by their maxima at δ Ϸ 65 ppm and at δ Ϸ 75 ppm. [14] By combining the 27 Al MAS spectra obtained at 9.4 T and 17.6 T, we tried to model the NMR spectra more precisely and to determine the different contributions (see Table 2). We can propose some quantitative description of the different phases, in agreement with the XRD conclu- 27 Al MAS NMR spectra of the samples 4a, 3b, 3c, 7a and 7b in relation with the spectra of the starting materials: cryolite and alumina.…”