Ru and Ni—Privileged Metal Combination for Environmental Nanocatalysis

Spatially Formed Tenacious Nickel-Supported Bimetallic Catalysts for CO2 Methanation under Conventional and Induction Heating

The paper introduces spatially stable Ni-supported bimetallic catalysts for CO₂ methanation. The catalysts are a combination of sintered nickel mesh or wool fibers and nanometal particles, such as Au, Pd, Re, or Ru. The preparation involves the nickel wool or mesh forming and sintering into a stable shape and then impregnating them with metal nanoparticles generated by a silica matrix digestion method. This procedure can be scaled up for commercial use. The catalyst candidates were analyzed using SEM, XRD, and EDXRF and tested in a fixed-bed flow reactor. The best results were obtained with the Ru/Ni-wool combination, which yields nearly 100% conversion at 248 °C, with the onset of reaction at 186 °C. When we tested this catalyst under inductive heating, the highest conversion was observed already at 194 °C.

A Review on Green Hydrogen Valorization by Heterogeneous Catalytic Hydrogenation of Captured CO2 into Value-Added Products

The catalytic hydrogenation of captured CO2 by different industrial processes allows obtaining liquid biofuels and some chemical products that not only present the interest of being obtained from a very low-cost raw material (CO2) that indeed constitutes an environmental pollution problem but also constitute an energy vector, which can facilitate the storage and transport of very diverse renewable energies. Thus, the combined use of green H2 and captured CO2 to obtain chemical products and biofuels has become attractive for different processes such as power-to-liquids (P2L) and power-to-gas (P2G), which use any renewable power to convert carbon dioxide and water into value-added, synthetic renewable E-fuels and renewable platform molecules, also contributing in an important way to CO2 mitigation. In this regard, there has been an extraordinary increase in the study of supported metal catalysts capable of converting CO2 into synthetic natural gas, according to the Sabatier reaction, or in dimethyl ether, as in power-to-gas processes, as well as in liquid hydrocarbons by the Fischer-Tropsch process, and especially in producing methanol by P2L processes. As a result, the current review aims to provide an overall picture of the most recent research, focusing on the last five years, when research in this field has increased dramatically.

Catalytic Removal of NOx on Ceramic Foam-Supported ZnO and TiO2 Nanorods Ornamented with W and V Oxides

Energy consumption steadily increases and energy production is associated with many environmental risks, e.g., generating the largest share of greenhouse gas emissions. The primary gas pollution concern is CO2, CH4, and nitrogen oxides (NOx). Environmental catalysis plays a pivotal role in NOx mitigation (DeNOx). This study investigated, for the first time, a collection of ceramic foams as potential catalyst support for selective catalytic NOx reduction (SCR). Ceramic foams could be an attractive support option for NOx removal. However, we should functionalize the surface of raw foams for such applications. A library of ceramic SiC, Al2O3, and ZrO2 foams ornamented with nanorod ZnO and TiO2 as W and V oxide support was obtained for the first time. We characterized the surface layer coating structure using the XPS, XRF and SEM, and TEM microscopy to optimize the W to V molar ratio and examine NO2 mitigation as the SCR model, which was tested only very rarely. Comparing TiO2 and ZnO systems reveals that the SCR conversion on ZnO appeared superior vs. the conversion on TiO2, while the SiC-supported catalysts were less efficient than Al2O3 and ZrO2-supported catalysts. The energy bands in optical spectra correlate with the observed activity rank.

CO2—A Crisis or Novel Functionalization Opportunity?

The growing emission of carbon dioxide (CO2), combined with its ecotoxicity, is the reason for the intensification of research on the new technology of CO2 management. Currently, it is believed that it is not possible to eliminate whole CO2 emissions. However, a sustainable balance sheet is possible. The solution is technologies that use carbon dioxide as a raw material. Many of these methods are based on CO2 methanation, for example, projects such as Power-to-Gas, production of fuels, or polymers. This article presents the concept of using CO2 as a raw material, the catalytic conversion of carbon dioxide to methane, and consideration on CO2 methanation catalysts and their design.

Synthesis and thermal properties of the heterometallic nickel–ruthenium complex: a potential precursor for catalytically active nanosized Ni–Ru alloy

Thermal decomposition of the novel heterometallic complex [RuNO(NO2)4OHNi(En)2] results in a single-phase metastable solid solution Ni0.5Ru0.5. The catalytic activity of the prepared nanoalloy in the CO methanation reaction was demonstrated.

Functional and Material Properties in Nanocatalyst Design: A Data Handling and Sharing Problem

(1) Background: Properties and descriptors are two forms of molecular in silico representations. Properties can be further divided into functional, e.g., catalyst or drug activity, and material, e.g., X-ray crystal data. Millions of real measured functional property records are available for drugs or drug candidates in online databases. In contrast, there is not a single database that registers a real conversion, TON or TOF data for catalysts. All of the data are molecular descriptors or material properties, which are mainly of a calculation origin. (2) Results: Here, we explain the reason for this. We reviewed the data handling and sharing problems in the design and discovery of catalyst candidates particularly, material informatics and catalyst design, structural coding, data collection and validation, infrastructure for catalyst design and the online databases for catalyst design. (3) Conclusions: Material design requires a property prediction step. This can only be achieved based on the registered real property measurement. In reality, in catalyst design and discovery, we can observe either a severe functional property deficit or even property famine.

Ru/Ce/Ni Metal Foams as Structured Catalysts for the Methanation of CO2

The development of highly conductive structured catalysts with enhanced mass- and heat-transfer features is required for the intensification of the strongly exothermic catalytic hydrogenation of CO2 in which large temperature gradients should be avoided to prevent catalyst deactivation and to control selectivity. Therefore, in this work we set out to investigate the preparation of novel structured catalysts obtained from a commercial open cell Ni foam with high pore density (75 ppi) onto which a CeO2 layer was deposited via electroprecipitation, and, eventually, Ru was added by impregnation. Composite Ru/Ce/Ni foam catalysts, as well as simpler binary Ru/Ni and Ce/Ni catalysts were characterized by SEM-EDX, XRD, cyclic voltammetry, N2 physisorption, H2-temperature programmed reduction (TPR), and their CO2 methanation activity was assessed at atmospheric pressure in a fixed bed flow reactor via temperature programmed tests in the range from 200 to 450 °C. Thin porous CeO2 layers, uniformly deposited on the struts of the Ni foams, produced active catalytic sites for the hydrogenation of CO2 at the interface between the metal and the oxide. The methanation activity was further boosted by the dispersion of Ru within the pores of the CeO2 layer, whereas the direct deposition of Ru on Ni, by either impregnation or pulsed electrodeposition methods, was much less effective.

Bimetallic Ni-Based Catalysts for CO2 Methanation: A Review

CO₂ methanation has recently emerged as a process that targets the reduction in anthropogenic CO₂ emissions, via the conversion of CO₂ captured from point and mobile sources, as well as H₂ produced from renewables into CH₄. Ni, among the early transition metals, as well as Ru and Rh, among the noble metals, have been known to be among the most active methanation catalysts, with Ni being favoured due to its low cost and high natural abundance. However, insufficient low-temperature activity, low dispersion and reducibility, as well as nanoparticle sintering are some of the main drawbacks when using Ni-based catalysts. Such problems can be partly overcome via the introduction of a second transition metal (e.g., Fe, Co) or a noble metal (e.g., Ru, Rh, Pt, Pd and Re) in Ni-based catalysts. Through Ni-M alloy formation, or the intricate synergy between two adjacent metallic phases, new high-performing and low-cost methanation catalysts can be obtained. This review summarizes and critically discusses recent progress made in the field of bimetallic Ni-M (M = Fe, Co, Cu, Ru, Rh, Pt, Pd, Re)-based catalyst development for the CO₂ methanation reaction.