title: Towards a full understanding of the nature of Ni(II) species and hydroxyl groups over highly siliceous HZSM-5 zeolite supported nickel catalysts prepared by a deposition-precipitation method.
abstract: Highly siliceous HZSM-5 zeolite supported nickel catalysts prepared by a deposition-precipitation (D-P) method were characterized by Fourier transform infrared (FT-IR), hydrogen temperature programmed reduction (H2-TPR), X-ray diffraction (XRD), N2-absorption/desorption, field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and (27)Al magic-angle nuclear magnetic resonance (MAS NMR) techniques. The results showed that the D-P of nickel species occurred predominantly on the internal surface of highly siliceous HZSM-5 zeolite, in which the internal silanol groups located on the hydroxylated mesopores or nanocavities played a key role. During the D-P process, nickel hydroxide was first deposited-precipitated via olation/polymerization of neutral hydroxoaqua nickel species over the HZSM-5 zeolite. With the progress of the D-P process, 1 : 1 nickel phyllosilicate was formed over the HZSM-5 via the hetero-condensation/polymerization between charged hydroxoaqua nickel species and monomer silicic species generated due to the partial dissolution of the HZSM-5 framework. The 1 : 1 nickel phyllosilicate could also be generated via the hydrolytic adsorption of hydroxoaqua nickel species and their subsequent olation condensation. After calcination, the deposited-precipitated nickel hydroxide was decomposed into nickel oxide, while the 1 : 1 nickel phyllosilicate was transformed into 2 : 1 nickel phyllosilicate. According to the above mechanism, Ni(ii) species were present both in the form of nickel oxide and 2 : 1 nickel phyllosilicate, which were mutually separated from each other, being highly dispersed over HZSM-5 zeolite.
authors.affiliation: State Key Laboratory of Disaster Prevention & Reduction for Power Grid Transmission and Distribution Equipment, Hunan Electric Power Corporation Disaster Prevention and Reduction Center, State Grid Key Laboratory of Power Transmission and Distribution Equipment Anti-icing & Reducing-disaster Technology, Changsha 410007, China.
authors.forename: Bao-Hui
authors.initials: BH
authors.lastname: Chen
authors.forename: Zi-Sheng
authors.initials: ZS
authors.lastname: Chao
authors.forename: Hao
authors.initials: H
authors.lastname: He
authors.forename: Chen
authors.initials: C
authors.lastname: Huang
authors.forename: Ya-Juan
authors.initials: YJ
authors.lastname: Liu
authors.forename: Wen-Jun
authors.initials: WJ
authors.lastname: Yi
authors.forename: Xue-Ling
authors.initials: XL
authors.lastname: Wei
authors.forename: Jun-Fang
authors.initials: JF
authors.lastname: An