Effect of decomposition of catalyst precursor on Ni/CeO2 activity for CO methanation

Silica-Decorated NiAl-Layered Double Oxide for Enhanced CO/CO2 Methanation Performance

CO/CO₂ hydrogenation has attracted much attention as a pathway to achieve carbon neutrality and production of synthetic natural gas (SNG). In this work, two-dimensional NiAl layered double oxide (2D NiAl-LDO) has been successfully decorated by SiO₂ nanoparticles derived from SiCl₄ and used as CO/CO₂ methanation catalysts. The as-obtained H-SiO₂-NiAl-LDO exhibited a large specific surface area of 201 m²/g as well as high ratio of metallic Ni⁰ species and surface adsorption oxygen that were beneficial for low-temperature methanation of CO/CO₂. The conversion of CO methanation was 99% at 400 °C, and that of CO₂ was 90% at 350 °C. At 250 °C, the CO methanation reached 85% whereas that of CO₂ reached 23% at 200 °C. We believe that this provides a simple method to improve the methanation performance of CO and CO₂ and a strategy for the modification of other similar catalysts.

A review of the advances in catalyst modification using nonthermal plasma: Process, Mechanism and Applications

With the continuous development of catalytic processes in chemistry, biology, organic synthesis, energy generation and many other fields, the design of catalysts with novel properties has become a new paradigm in both science and industry. Nonthermal plasma has aroused extensive interest in the synthesis and modification of catalysts. An increasing number of researchers are using plasma for the modification of target catalysts, such as modifying the dispersion of active sites, regulating electronic properties, enhancing metal-support interactions, and changing the morphology. Plasma provides an alternative choice for catalysts in the modification process of oxidation, reduction, etching, coating, and doping and is especially helpful for unfavourable thermodynamic processes or heat-sensitive reactions. This review focuses on the following points: (i) the fundamentals behind the nonthermal plasma modification of catalysts; (ii) the latest research progress on the application of plasma modified catalysts; and (iii) main challenges in the field and a vision for future development.

Study on the monolayer dispersion behavior of SnO2 on ZSM-5 for NOx-SCR by C3H6: the remarkable promotional effects of air plasma treatment

Aiming to fabricate more practical catalysts for NO_x-SCR with C₃H₆, SnO₂/ZSM-5 having different SnO₂ loadings was prepared and treated with DBD air plasma. The dispersion of SnO₂ on the H-ZSM-5 support and their interactions were investigated with both experimental methods and DFT calculations. SnO₂ displays evident monolayer dispersion behavior, getting a threshold of 0.271 mmol 100 m^-2 support. Plasma treatment improves significantly the SnO₂ dispersion, hence amplifying the monolayer dispersion threshold to 0.380 mmol 100 m^-2. XPS and DFT calculations have testified that plasma treatment strengthens strongly the SnO₂-ZSM-5 support interaction, mainly through donating electrons from Sn⁴⁺ to Al³⁺ in the support, thus improving the dispersion of SnO₂ at the same loadings. Consequently, the catalytic performance is remarkably improved because of the generation of more abundant surface acid sites and superoxide species devoted to the reaction. The sample having a SnO₂ loading near the monolayer dispersion threshold shows the optimal activity in the corresponding catalyst series, demonstrating an evident threshold effect. Over SnO₂/ZSM-5, the reaction goes through a Langmuir-Hinshelwood pathway, involving the adsorption and activation of both NO and C₃H₆ molecules. Surface mono-dentate/bridged-nitrate and carbonate species are the main reaction intermediates.

Hydrogen reverse spillover eliminating methanation over efficient Pt–Ni catalysts for the water–gas shift reaction

Hydrogen reverse spillover from Ni0 sites to Pt sites completely eliminated the side reaction of methanation and improved the catalytic activity of Ni0 sites over a nickel phyllosilicate-supported Pt–Ni catalyst during the water–gas shift reaction.

Structural effect of Ni/TiO2 on CO methanation: improved activity and enhanced stability

CO methanation over a supported Ni catalyst has attracted increasing attention for its applications in synthetic natural gas production, CO removal for ammonia synthesis and fuel cells, among others. However, the deactivation of the Ni catalyst caused by sintering and carbon deposition hinders further application of the Ni catalyst. The activity of Ni catalysts needs further improvement as well. In this work, the structural effect of the Ni/TiO₂ catalyst on CO methanation was investigated. A plasma decomposition, initiated at room temperature and operated around 150 °C, of the nickel precursor was applied to prepare the catalyst. Compared to the thermally decomposed Ni/TiO₂ catalyst, the plasma-decomposed catalyst shows improved activity with enhanced stability. The catalyst characterization shows that the plasma-decomposed Ni/TiO₂ catalyst possesses smaller Ni particle size and higher Ni dispersion, resulting in improved coke resistance and enhanced anti-sintering ability for CO methanation. The present study confirms that a catalyst with good activity for CO methanation possesses good activity for CO₂ methanation as well, if the CO₂ methanation takes the CO methanation pathway.

Highly dispersed Ni/TiO₂ catalyst with Ni (111) obtained by cold plasma decomposition shows improved activity and carbon resistance for CO methanation.

Mechanochemical synthesis of ZnO.Al2O3 powders with various Zn/Al molar ratios and their applications in reverse water-gas shift reaction

ZnO.Al₂O₃ powders with various Zn/Al molar ratios were prepared via a solid-state reaction using a mechanochemical synthesis method, and the selected powder with a ZnO/Al₂O₃ molar ratio of 1 was used as support for the preparation of 15% Ni/ZnO.Al₂O₃ catalyst. The activity of the prepared catalyst was studied in the reverse water-gas shift (RWGS) reaction. The synthesized samples were characterized by XRD, BET, TGA/DTA, TPR, FTIR, and SEM techniques. The results indicated that the prepared powders possessed mesoporous structure with pores having small diameters with crystallite sizes in the nanometer range (6.35-12.08 nm). The results showed that the increment in Zn/Al molar ratio reduced the BET area and the pure Al₂O₃ powder possessed the highest BET area (235.4 m² g^-1). The results also indicated that the rise of calcination temperature remarkably decreased the BET area. The prepared nickel-based catalyst also exhibited a high activity in RWGS reaction.

CO activation and methanation mechanism on hexagonal close-packed Co catalysts: effect of functionals, carbon deposition and surface structure

Regardless of the functionals used and the presence of graphitic carbon, the CO methanation rate on Co(0001) is mainly controlled by CHO decomposition.