Multinuclear MAS n.m.r. and i.r. spectroscopic study of silicon incorporation into SAPO-5, SAPO-31, and SAPO-34 molecular sieves

Crystallization and Si incorporation mechanisms of SAPO-34

“…27 Al NMR showed a typical NMR peak at 38 ppm due to aluminum in tetrahedral environment of the SAPO-34 framework. 31 P and 29 Si NMR each showed a single resonance at À27.4 and À90.5 ppm, respectively, typical of P(Al) and Si(4Al) environments in the SAPOs [14,15,[20][21][22][23]. With the consumption of the amorphous materials with time, the resonance peaks of tetrahedral aluminum, P(Al) and Si(Al) in the SAPO-34 lattice increased rapidly with the decrease of the resonance peaks of the amorphous materials, indicating higher crystallinity of the samples.…”

A study of the acidity of SAPO-34 by solid-state NMR spectroscopy

“…7). In previous studies [34][35][36], the peaks at 3.7 and 1.6 ppm were unambiguously attributed to Brønsted acid sites and SiOH, respectively. However the assignment of the signal at 2.6 ppm is still not clear [37].…”

Framework cobalt and manganese in MeAPO-31 (Me=Co, Mn) molecular sieves

“…The synthesis procedures, chosen according to the literature reports on SAPO-31 [2,[4][5][6][7] and MeAPO-31 [8,[14][15][16], were systematically studied and optimized. Final molar compositions of the reaction mixtures and the synthesis conditions for the preparation of pure AlPO 4 -31 and Me-APO-31 (Me ¼ Co, Mn) phases are given in Table 1.…”

“…Phosphorus substitution was later confirmed using several characterization methods [4][5][6][7] and was supported by several catalytic reactions such as hydrocarbon transformations [8][9][10][11][12]. Suggestions for the incorporation of other metals into the AlPO 4 -31 framework can be found in three publications for TAPO-31 [13], ZnAPO-31 [3] and MgAPO-31 [3,14], and catalytic applications are reported for TAPO-31 [15], VAPO-31 [16], MnAPO-31 [8,17], NiAPO-31 [17], ZnAPO-31 [17] and FeAPO-31 [18].…”