Incorporation of Transition Metal Ions into MeAPO/MeAPSO Molecular Sieves

Abstract

The synthetic incorporation of transition metal ions into aluminophosphate and silicoaluminophosphate molecular sieve frameworks is studied by electron spin−echo modulation (ESEM) spectroscopy. Based mainly on bulk chemical composition of the product, it has been suggested that divalent and trivalent metal ions such as Mn(II), Co(II), Cr(III), and Fe(III) substitute for framework aluminum sites. On the basis of 31P ESEM results, we originally suggested a framework phosphorus site for the incorporation of metal ions such as Ni(II) and Cr(III) in NiAPSO-5 and CrAPSO-5 molecular sieves. This site was later supported for other metal ions such as Ti(IV), V(IV), and Cu(II). In this work, we have extended such studies to Mn(II) and Fe(III) to better understand the metal substitution sites in AlPO4 frameworks. Irrespective of the particular metal ion, the 31P ESEM spectra of MeAPO/MeAPSO molecular sieves can be interpreted best on the basis of metal incorporation at a framework phosphorus site. Strong 27Al modulations are also observed for these materials, which supports the 31P ESEM result that incorporated metal ions are located nearer to aluminum than phosphorus.

Towards an understanding of the oxidation state of cobalt and manganese ions in framework substituted microporous aluminophosphate redox catalysts: An electron paramagnetic resonance and X-ray absorption spectroscopy investigation

“…This is principally because previous attempts to resolve this issue have focussed upon investigating cobalt or manganese ions substituted into structures such as AlPO-5, AlPO-11 and AlPO-44, despite the fact that X-ray absorption spectroscopic results clearly suggested that high conversions of Co(II) to Co(III) can be achieved only in particular structures such as AlPO-18 or AlPO-34. [6][7][8][9][10][11] In addition to the redox quandary, the nature of the manganese substitution in many of the AlPO-5, AlPO-44 and AlPO-11 structures has been interpreted differently by various researchers, although again X-ray absorption spectroscopic results combined with computer modelling studies clearly showed that the Mn(II) ions are located in the framework tetrahedral sites, in place of Al(III) [12][13][14][15][16] and undergo a change in oxidation state to Mn(III) upon calcination. [16][17][18] In order to investigate the discrepancy between the results of these techniques and to answer the questions outlined above, we carried out an EPR and in situ X-ray absorption spectroscopic investigation on cobalt and manganese substituted AlPO-5 and AlPO-18 materials.…”

Research on the direct amination of benzene to aniline by NiAlPO4–5 catalyst

“…For the same type of metal ions, the migration extent of d values reflects the amount of nickel substitution into the molecular sieve. The greater increasing of d is, the more of metal ions go into the molecular sieve framework, as shown in Figure 1, angle shifting to a small angle of Ni (0.3) AlPO 4 -5 sample (100) is the most obvious, it shows that the amount of Ni metal ions which isomorphously substitute P 5+ [32] in molecular sieve skeleton is the largest. This has been verified by the fact that, when the doping amount of Ni is 0.3, the catalyst shows the highest activity.…”

“…The catalyst was prepared by static hydrothermal method according to literature after modifications, isopropanol aluminum, phosphoric acid and nickel nitrate hexahydrate as a source of Al, P and metal source, triethylamine as the template. The gel started from the mixture of 1.0 TEA: (0–0.4) NiO: 0.95 Al 2 O 3 : 1 P 2 O 5 : 40 H 2 O.…”

Synthesis of hierarchical MeAPO-5 molecular sieves – Catalysts for the oxidation of hydrocarbons with efficient mass transport

“…The weight loss stages can be described as follows: (1) the weight loss at the first stage was attributed to the desorption of water; (2) the second stage was related to the slow decomposition of TEA; (3) the third stage was attributed to the decomposition of glucose and the protonized form of TEA [33][34][35], which compensated the anionic framework of MeAPO-5-meso; (4) the weight loss above 755 K was due to the dehydration of OH and the combustion of carbon deposition. It is reported that Co 2+ , Mn 2+ , Fe 3+ /Fe 2+ , and Mg 2+ mainly substitute for Al 3+ , and, Ti 4+ substitutes for P 5+ in the AlPO-5 framework according to the isomorphous substitution mechanism [36]. For FeAPO-5-meso, if the substitutive metal ion is Fe 3+ only, there would be no charge compensation because of the same valence of Fe 3+ and Al 3+ .…”