SAPOs, MeAPOs and VPI

Characterization of the OH stretching region by DRIFT spectroscopy besides TPD measurements was reported by Chen et al. [535] for a series of SAPOs (SAPO-5, SAPO-17, SAPO-18 and SAPO-34), prepared by these authors. Besides 

Attempts to incorporate zinc into the MFI structure were undertaken and controlled by FTIR spectroscopy in a recent work by Valange et al. [ 536]. The authors found that Zn is highly dispersed in the MFI matrix and possibly partly anchored to the zeolite framework (cf. also [345]). The presence of Zn produced a new type of acid OH groups, which were indicated by a medium-to-strong band at 3640 cm did not form ammonium ions with adsorbed ammonia (i.e., they were not true B-sites) but interacted with CO (cf. Sect. 5.5.2.6.6). Also,CO adsorption produced a band at 2200 cm due to Lewis acid C-sites (Zn ). 

CoAPO-5 and CoAPO-11 were shown by Peeters et al. [539] via IR spectroscopy (using CD3CN and CO as probes, vide infra. Sects. 5.S.2.6.4 and 5.S.2.6.6) to possess unusual Lewis acidity and redox properties (cf. also [540]). 

Transmission IR spectra of aliuninophospates with 18-membered ring channels, VPl-5 and VPl-5 modified via introduction of silicon and manganese, designated as [Si] VPl-5 and [Mn] VPI-5, were provided in a contribution by Issakov et al. [541 ]. Pyridine adsorption on the modified materials revealed the presence of strong Br0nsted acidity (cf. Sect 5.5.2.6.2). 

A selection of pertinent IR results related to fimdamental stretching modes of OH groups of molecular sieves and reported in the literature together with the respective references are listed in Table 6 (see also [542]). 

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