Nickel–zeolite composite catalysts with metal nanoparticles selectively encapsulated in the zeolite micropores

Abstract

Metal zeolite composite catalysts have found numerous applications in adsorption, gas separation, petroleum refining and chemical industry. The key issue in the design of these catalysts is the localization of the metal within the zeolite structure. This paper focuses on a new approach to the synthesis of nickel-zeolite composite catalysts selectively containing metal nanoparticles inside the zeolite pores. In the catalysts prepared by conventional impregnation, metal particles from the external surface of the zeolites were selectively removed by extraction with bulky polymer molecules of poly-4-styrenesulfonic acid. The method is particularly suitable for the ZSM-5 zeolite with relatively narrow micropores. The nickel zeolite catalysts were tested in hydrogenation of toluene and 1,3,5-tri-isopropyl benzene (TIPB). The removal of nickel particles from the zeolite external surface leads to a considerable decrease in the hydrogenation rate of the bulky TIPB molecules, while toluene hydrogenation was affected to a much lesser extent and was almost proportional to the nickel content. The proposed methodology can be extended to other types of microporous catalysts.

Versatile Roles of Metal Species in Carbon Nanotube Templates for the Synthesis of Metal–Zeolite Nanocomposite Catalysts

“…Thus, the low-temperature peaks observed between 400 and 500 °C in the TPR profiles of nickel–zeolite catalysts may correspond to the reduction of small NiO particles. Note that the Ni/ZSM-5 zeolite prepared by impregnation usually contains a significant concentration of NiO on the zeolite outer surface. These NiO nanoparticles are detected in Ni/ZSM-5 by XRD (Figure S1).…”

“…Only minor changes are observed in the microporous and mesoporous zeolite volume after the impregnation with metals. In agreement with the literature, this indicates that the metal cations are preferentially located in the zeolite micropores, whereas metal oxides species are located on the external surface of ZSM-5. , …”

Recent developments in the control of selectivity in hydrogenation reactions by confined metal functionalities

“…Host-guest assembly allows facile incorporation of metallic cations or complexes into/onto the zeolite by ion-exchange 50,51 or incipient wetness impregnation. 52 While the ion-exchange capacity is highly dependent on the number of countercations per unit cell, the quantity of metal introduced by wetness impregnation is limited by the pore size and volume. 22 Despite the ease of these methods, surface deposition of NPs is often unavoidable.…”

“…This phenomenon was demonstrated by impregnating nickel precursor on ZSM-5, leading to nickel oxide nanoparticles on the surface and in the ZSM-5 channels. 52 This random distribution allowed hydrogenating both toluene and 1,3,5-tri-isopropyl benzene regardless of their different molecular size. Selectively extracting surface NPs by poly-4-styrenesulfonic acid decreased the conversion of 1,3,5-tri-isopropyl benzene considerably.…”

Sustainable development and enhancement of cracking processes using metallic composites

“…Desulphurization mechanism and pathways ( Adapted from Yang et al [70] Copyright 2015 Elsevier BV)two commonly employed methods of synthesizing metallic composites[77].…”