Abstract
The supporting modes of active metal over mesoporous materials play an important role in catalytic performance. The location of Ni nanoparticles inside or outside the mesoporous channel of MCM-41 has a significant influence on the reactivity in partial oxidation of methane to syngas reaction. The characterization data using different techniques (Transmission Electron Microscope (TEM), X-Ray Diffraction (XRD), N2 adsorption-desorption, H2 Temperature-Programmed Reduction (H2-TPR), and Inductively Coupled Plasma (ICP)) indicated that nickel was located outside the mesoporous channels for the impregnation method (Ni/MCM-41), while nickel was encapsulated within MCM-41 via the one-step hydrothermal crystallization method (Ni-MCM-41). The nickel atoms were mainly dispersed predominantly inside the skeleton of zeolite. When the load amount of Ni increased, both of Ni species inside the skeleton or pore channel of zeolite increased, and the ordered structure of MCM-41 was destroyed gradually. Contributed by the strong interaction with MCM-41, the Ni particles of Ni-MCM-41 were highly dispersed with smaller particle size compared with supported Ni/MCM-41 catalyst. The Ni-MCM-41 displayed higher catalytic performance than Ni/MCM-41, especially 10% Ni-MCM-41 due to high dispersity of Ni. The confinement effect of MCM-41 zeolite also afforded high resistance of sintering and coking for 10% Ni-MCM-41 catalyst. Especially, 10% Ni-MCM-41 catalyst showed outstanding catalytic stability.
Highlights
While the natural gas industry is relatively underdeveloped, as the predominant component of natural gas, methane is expected to exceed oil by the known enormous reserves
The results indicated that the prepared catalysts possessed long-range ordered hexagonal mesoporous skeleton structure of MCM-41
For Ni-MCM-41 catalyst, the intensities of all the diffraction peaks were lower compared to Ni/MCM-41
Summary
While the natural gas industry is relatively underdeveloped, as the predominant component of natural gas, methane is expected to exceed oil by the known enormous reserves. In order to improve the stability and performance of the catalyst, variety of strategies have been proposed including introduction of assistant, modification of support, and encapsulation of metal into inert porous material (SiO2 , C) [9,10]. These methods have improved the stability of catalyst to some extent, but it could not solve the underlying problems. MCM-41 makes contributions to the improvement of catalytic activity and stability due to highly dispersed and stabilized active centers on the pore wall surface This anchoring effect promoted the formation of the active Ni nano-clusters with high dispersion and prevented carbon deposition due to the limited growth space of carbon fiber [20,21].
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