Encapsulation of Metal Nanoparticles (MNPs) as Catalyst

Abstract

Metal nanoparticles (MNPs) are the main agents in heterogeneous catalysis. Hence, utilizing the effective physico-chemical methods to engage them to achieve the highest catalysts performance with well-controlled size, shape, and surface properties seems to be essential. The encapsulation of metal nanoparticles is a promising approach that enhances the catalytic activity of the materials. Not only the encapsulating structures can adjust the catalytic properties of metal nanoparticles, particularly selectivity, but also prevents them from agglomeration and sintering. In this chapter, the various encapsulating structures consist of yolk/core-shell and mesoporous structures, and encapsulating materials that are divided into three parts, including inorganic materials, metal–organic frameworks, and organic materials are presented.

Promoting jet fuel production by utilizing a Ru-doped Co-based catalyst of Ru-Co@C(Z-d)@Void@CeO2 in Fischer Tropsch synthesis

“…14 The cobalt and ruthenium NPs were encapsulated in the ZIF-67 matrix, a metal-organic framework (MOF), and then through the thermal treatment steps, pyrolysis (at the 883 K under N 2 for 4 h) and calcination (in the air at the 673 K for 2 h), 14,20 the ZIF-67 complex was converted to a porous carbon layer that encapsulated the cobalt nanoparticles and was doped with the ruthenium nanoparticles at the core of the catalyst. 18,21 The insertion of Ru into the catalyst structures was implemented by adding ruthenium(III) nitrosyl nitrate (RuN 4 O 10 ) as the precursor during the synthesis of the ZIF-67 with a volume ratio of 2% RuN 4 O 10 of the entire solution. 22 RuN 4 O 10 was encapsulated by ZIF-67 crystals.…”

“…Thus, the results from the promoted fabricated catalyst have been compared with the results from the catalyst without the ruthenium. The incorporation of a noble metal as a promoter alongside a base metal in the catalyst can be conducted via the formation of various nanostructures such as alloy, core-shell, and segregation, which are presented in the literature, [15][16][17][18] but intertwining the promoter (Ru) and the base metal (Co) through a porous carbon shell in the core of a MOF-derived catalyst with a hollow void is a new approach in the present work.…”

A hollow void catalyst of Co@C(Z-d)@void@CeO2 for enhancing the performance and stability of the Fischer–Tropsch synthesis

“…6,7 In addition, the core-shell nano-catalysts can provide uniform dispersion of the metal nanoparticles (MNPs) as active sites, and high metal loading leads to signicant improvement of their activity. [2][3][4][6][7][8] There is a wide range of researches on FTS cobalt-based catalysts that utilize the core-shell structure. A prominent achievement is represented by encapsulating the cobalt nanoparticles with two shells consisting of an inert nanolayer of carbon which encapsulates and immobilizes cobalt nanoparticles in the core and the main outer shell is formed by inorganic oxides like SiO 2 or TiO 2 .…”

“…So, these metal oxides can be nominated as the best material for synthesizing the outer shell. 8 Although the inorganic oxide shell has many suitable attributes, its multi-layer matrix structure reduces the reactants' and products' mass transfer rate through the FTS process. Besides, in core-shell structure, the outer shell may cover some of the active Co sites, leading to a decline in the accessibility of the reactants, and then a diminution occurs in the CO conversion.…”

“…6,7 In addition, the core–shell nano-catalysts can provide uniform dispersion of the metal nanoparticles (MNPs) as active sites, and high metal loading leads to significant improvement of their activity. 2–4,6–8…”