Comparative study of the hydrogen reduction of Ni2+ ions in X- and Y-zeolites

Abstract

NisNa 64H 6(sio2)1 O6(A102)8 6 Ni 3Na2 4 3 0 2 ) 3&4102)56 Ni20Na16(Si02) 136(402)56 Ni~1Na24(Si02)1o6(A102)s6

Electron Spin Resonance and Electron Spin Echo Modulation Studies of Ion-Exchanged NiH−SAPO-17 and NiH−SAPO-35 Molecular Sieves: Comparison with Ion-Exchanged NiH−SAPO-34 Molecular Sieve

“…This preference of Ni(II) for site SI has been verified by XRD and diffuse reflectance spectroscopy for synthetic NiNa-Y and nickel-exchanged natural faujasite. [32][33][34] For higher Ni loading, Ni occupation of site SI is limited by the number of such sites available and by its charge density which depends on the Si/Al ratio. It has been reported that in Na-Y with a Si/Al ratio of 2.4, out of 16 sites per unit cell a maximum of 12 SI sites are occupied by Ni(II) ions.…”

X-ray study of the reduction and reoxidation of nickel(2+) ion in x-type zeolite in the presence of cerium(3+) ion

“…Because of the double peaks, Sr(0.068) sites have been unambiguously attributed to Ce3+ cations and Sr-(0.045) sites to Ni2+ cations. In fact the coordinates of Sp(0.068) sites Eire in good agreement with those found for Ce3+ ions in previous studies on Ce-X zeolites;6 in the same 5.3 (9) 5.9 (9) Ce(I'), X = Y=Z 0.068 (2) 0.068 (2) 0.066 (3) 0.069 (1) 0.067 (2) P 2.7(5) 3.8 (5) 5.5 (3) 4.4 (2) 5.4 (5) Ow(H')> X = Y = z 0.157 (4) 0.166 (2) 0.159 (3) P 10 (2) 17 (2) 18(2) ( ), X= Y=Z 0.202 (3) 0.191 (6) P 4.8 (7) 2.0 (6) Na(II), X = Y= Z 0.232 (1) 0.232 (1)…”

Location and reducibility of nickel(2+) ions in an X-type zeolite in the presence of lanthanum(3+)

“…Long X-ray irradiation can result in a depopulation of the hexagonal prisms.11 On the other hand, in NiNa-X or -Y, Ni2+ cations prefer to occupy first sites S¡ and Sr, after complete dehydration. 1,4,11 The present work is concerned with the study of Ni2+ reduction in an X-type zeolite in the presence of La3+, a 0022-3654/80/2084-0875$01.00/0 © 1980 American Chemical Society particularly hydrophilic cation which could modify both the physicochemical properties of the zeolitic matrix and the Ni2+ cation location. Structural analysis was carried out on samples before reduction and with various degrees of reduction, simultaneously with the kinetic study of the reaction.…”

“…When relative absorbances of the CO and NO absorption bands against bulk metal concentration ratios were plotted, quantitative conclusions regarding surface concentrations could be made. This technique has several advantages over the more conventional spectroscopic techniques such as ESCA, SIMS, ISS, EXAFS, and AES in that (1) only the surface layer is sampled, (2) considerably more chemical information can 0022-3654/80/2084-0878801.00/0 be obtained, (3) when applied to highly dispersed supported bimetallic clusters, techniques such as ESCA and AES essentially sample the entire metal sample, and (4) infrared spectroscopy is inexpensive and can be used to sample the surface at high pressures under reaction conditions, Its major disadvantages are that (1) extensive preliminary experiments to determine surface interactions of adsorbing species are usually required, (2) the method is not as accurate as the above-mentioned spectroscopic techniques, and (3) surface reconstruction may be induced by the chemisorbing species.…”