29Si CP/MAS NMR spectra

Fig. 12.12 29Si CP-MAS NMR spectra of star gels obtained from Star A and Star B precursors. Trifunctional silicon centers were named with the conventional T notation, where T refers to (SiO) R Si(OR)3 units and n to the number of bridging oxygen atoms surrounding the central silicon atom. In both BSC materials, the T2, T1 and T° relative contribution was...

Fig. 2 29Si CP/MAS-NMR spectra of sepiolite a) unheated b) heated to 120°C in air for 20 h and c) sample b after exposure to acetone vapor for 4 days.

Figure 3.4 29Si CP MAS NMR spectra ofLSA silica gel before (a) and after (b and b ) H/D exchange in liquid D20, (b) plotted on the same intensity scale as (a), (b ) at 26 times this intensity scale. Taken from ref. (51) with permission.

Figure 9.19 29Si CP MAS NMR spectra of modified silica (a) APTS modified, vacuum cured (b) APTS modified air cured (c) APDMS modified, air cured.

Figure 9.20 29Si CP MAS NMR spectra ofmesoporous silica gel, pretreated at 473 K and modified with APTS in toluene solvent, after curing under vacuum at indicated temperature taken from ref. (22) with permission.

In figure 9.33 the 29Si CP MAS NMR spectra of the APTS modified silica samples with variable pretreatment temperature are displayed. The spectrum contains two broad bands, which may be decomposed into three or four peaks. The surface Si atoms are found in the (-85, -125 ppm) region, while the (-45, -80 ppm) signals are due to silane Si atoms. Band assignments of the silane Si region have been made previously as indicated in table 9.8. 

Figure 9.33 29Si CP MAS NMR spectra of APTS modified silica gel with variable silica pretreatment temperature (a) 473 K, (b) 673 K, (c) 973 K.

Deuterated silicas were modified with APTS. 29Si CP MAS NMR spectra of the deuterated modified substrates are analogous to the spectra of the non-predeuterated... 

Figure 9.35 29Si CP MAS NMR spectra of silica gel after pretreatment at 973 K, deuteration and modification with APTS, measured with variable contact time, (a) 8 ms, (b) 5 ms, (c) 2.5 ms, (d) same sample before APTS modification at same scale,with 5 ms contact time.

Figure 5. 29Si CP-MAS NMR spectra of a mixture of TES-APS hydrolyzed by atmospheric water 2000 accumulations and contact time of 4 ms.

The 29Si CP-MAS NMR spectra recorded for the modified MF membranes were given, on Fig. (16c). This spectra can be divided into two regions. The first region, from +50ppm to... 

Chemical shifts in ppm spectra recorded at room temperature. b Isotropic chemical shifts obtained by 29Si CP/MAS NMR experiments. c Experiment failed. d No experiment performed. 

Si MAS-NMR and CP/MAS-NMR spectra have been reported for me-soporous silica catalysts derivatised with bis(halogeno)dioxomolybdenum(VI)... 

Si CP/MAS-NMR was used to characterise mesoporous materials derived from sodium silicate and organotrialkoxysilanes.493 Multinuclear NMR studies have been reported on periodic mesoporous organosilicas.494,495 13C and 29Si MAS-NMR spectra were used to characterise ordered macroporous organo-silica materials.496 A similar study has been made of mesoporous organosilica/ clay heterostructures.497... 

Three distinct peaks observed in the 29Si NMR spectra of the fluoroalkoxysilane indicating three distinct silicon chemical environments Fig. (16a). These peaks at chemical shifts of apvproximately -48.14 ppm, -54.52 ppm and -61.65 ppm are representatives respectively of Ti, T2 and T3 resonances. In Fig. (16b) we reported the 29Si CP/MAS NMR spectrum of used... 

Figure 6.15 (a) MAS and 29Si H CP/MAS NMR spectra (9.4 T) of a white portland cement hydrated for 28 days, acquired with spinning speeds of = 5.0... 

Figure 2a shows the 29Si MAS NMR spectra of calcined NbS-1, TaS-1 and ZSM-5 The spectral shapes of NbS-1 and TaS-1 are similar to those of aluminum-containing ZSM-5 with ns/nAi = 45, Three lines are observed for NbS-l(41) and TaS-l(74) whose chemical shifts are -103, -112 and -115 ppm. The line at -103 ppm is due to the presence of [SiO (OH)] units in defect sites within the silicalite-1 structure This assignment was confirmed by H - 29Si crosspolarization (CP) experiments in which the intensity of the signal at -103 ppm increased... 

The 29Si CP-MAS solid state NMR spectra of the crystal modifications of 60 and its hydrate were found to depend on the crystal structure, as shown in Table 6. In fact, the chemical shift difference between the pure (anhydrous) crystalline modifications was used to demonstrate the kinetic transformation in the solid state of one crystal structure to the other (Figure 7)47. 

MAS NMR spectra were obtained with a Bruker 400 MSL spectrometer. The experimental conditions used in the 29Si DEC, 29Si CP, 27Al, 27A1 CP and 31P DEC were as follows ... 

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