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A Review on the Different Aspects and Challenges of the Dry Reforming of Methane (DRM) Reaction

The dry reforming of methane (DRM) reaction is among the most popular catalytic reactions for the production of syngas (H₂/CO) with a H₂:CO ratio favorable for the Fischer-Tropsch reaction; this makes the DRM reaction important from an industrial perspective, as unlimited possibilities for production of valuable products are presented by the FT process. At the same time, simultaneously tackling two major contributors to the greenhouse effect (CH₄ and CO₂) is an additional contribution of the DRM reaction. The main players in the DRM arena-Ni-supported catalysts-suffer from both coking and sintering, while the activation of the two reactants (CO₂ and CH₄) through different approaches merits further exploration, opening new pathways for innovation. In this review, different families of materials are explored and discussed, ranging from metal-supported catalysts, to layered materials, to organic frameworks. DRM catalyst design criteria-such as support basicity and surface area, bimetallic active sites and promoters, and metal-support interaction-are all discussed. To evaluate the reactivity of the surface and understand the energetics of the process, density-functional theory calculations are used as a unique tool.

Simple Synthesis of Molybdenum Carbides from Molybdenum Blue Nanoparticles

In recent years, much attention has been paid to the development of a new flexible and variable method for molybdenum carbide (Mo₂C) synthesis. This work reports the applicability of nano-size clusters of molybdenum blue to molybdenum carbide production by thermal treatment of molybdenum blue xerogels in an inert atmosphere. The method developed made it possible to vary the type (glucose, hydroquinone) and content of the organic reducing agent (molar ratio R/Mo). The effect of these parameters on the phase composition and specific surface area of molybdenum carbides and their catalytic activity was investigated. TEM, UV–VIS spectroscopy, DTA, SEM, XRD, and nitrogen adsorption were performed to characterize nanoparticles and molybdenum carbide. The results showed that, depending on the synthesis conditions, variants of molybdenum carbide can be formed: α-Mo₂C, η-MoC, or γ-MoC. The synthesized samples had a high specific surface area (7.1–203.0 m²/g) and meso- and microporosity. The samples also showed high catalytic activity during the dry reforming of methane. The proposed synthesis method is simple and variable and can be successfully used to obtain both Mo₂C-based powder and supports catalysts.

Finding of a new cycle route in Ni/Mo2C catalyzed CH4–CO2 reforming

A new cycle route of Ni/Mo₂C ↔ MoNi₄ is firstly confirmed in a Ni/Mo₂C catalyzed CH₄–CO₂ reforming reaction.

Effect of Promoters on Steam Reforming of Toluene over a Ni-Based Catalyst Supported on Coal Gangue Ash

The exploration of high-value-added materials using inorganic solid waste is a very important contribution to sustainable development. Coal gangue ash (CGA) as a solid waste was chosen as catalyst support. Five low-cost catalysts modified by different promoters (Co, Ce, Fe, Mn, and Mo) were prepared using a co-impregnation method. The toluene steam reforming tests were carried out at 800 °C under S/C = 2 (steam-to-carbon mole ratio). Catalyst characteristics were evaluated using X-ray diffraction (XRD), the Brunauer-Emmett-Teller (BET) method, temperature-programmed reduction (TPR), and Raman spectroscopy. The results showed that most promoters could interact with a Ni active compound and enhance the toluene conversion and H2 yield. The Mo-Ni/CGA-1d (1d means the acid pretreatment time) catalyst performed the best catalytic activity, and corresponding toluene conversion and H2 yield was equal to 92.6 and 62.3%, respectively, and it should be due to the formation of Mo-Ni alloy. Meanwhile, the Mo-Ni/CGA-1d catalyst exhibited higher stability during the runtime of 300 min compared with the Mn-Ni/CGA-1d catalyst, which can be attributed to the formation of the Mo2C structure with high-carbon-resistance ability. This is perhaps because the dissociation of CO2 or H2O on the Mo2C structure surface is beneficial to the production of free oxygen species, which can accelerate the removal of carbon deposition on the catalyst surface.

Synthesis of Mo2C by Thermal Decomposition of Molybdenum Blue Nanoparticles

In recent years, the development of methods for the synthesis of Mo₂C for catalytic application has become especially important. In this work a series of Mo₂C samples was synthesized by thermal decomposition of molybdenum blue xerogels obtained using ascorbic acid. The influence of the molar ratio reducing agent/Mo [R]/[Mo] on morphology, phase composition and characteristics of the porous structure of Mo₂C has been established. The developed synthesis method allows the synthesis to be carried out in an inert atmosphere and does not require a carburization step. The resulting molybdenum carbide has a mesoporous structure with a narrow pore size distribution and a predominant pore size of 4 nm.

Reactions of water and C1 molecules on carbide and metal-modified carbide surfaces

The formation of carbides can significantly modify the physical and chemical properties of the parent metals. In the current review, we summarize the general trends in the reactions of water and C1 molecules over transition metal carbide (TMC) and metal-modified TMC surfaces and thin films. Although the primary focus of the current review is on the theoretical and experimental studies of reactions of C1 molecules (CO, CO₂, CH₃OH, etc.), the reactions of water will also be reviewed because water plays an important role in many of the C1 transformation reactions. This review is organized by discussing separately thermal reactions and electrochemical reactions, which provides insights into the application of TMCs in heterogeneous catalysis and electrocatalysis, respectively. In thermal reactions, we discuss the thermal decomposition of water and methanol, as well as the reactions of CO and CO₂ over TMC surfaces. In electrochemical reactions, we summarize recent studies in the hydrogen evolution reaction, electrooxidation of methanol and CO, and electroreduction of CO₂. Finally, future research opportunities and challenges associated with using TMCs as catalysts and electrocatalysts are also discussed.

Simple and large-scale synthesis of β-phase molybdenum carbides as highly stable catalysts for dry reforming of methane

The catalytic stability of monometallic β-Mo₂C/CNTs was found to be superior to that of bimetallic Ni/β-Mo₂C under similar reaction conditions.

Improvement of the catalytic stability of molybdenum carbide via encapsulation within carbon nanotubes in dry methane reforming

We reported for the first time the enhancement of the oxidation resistance of Mo₂C nanoparticles by encapsulation within carbon nanotubes (CNTs).

Simple synthesis of ultrasmall β-Mo2C and α-MoC1−x nanoparticles and new insights into their catalytic mechanisms for dry reforming of methane

Ultrasmall β- and α-molybdenum carbide particles were synthesized by a resin route and they showed different oxidation–recarburization cycles.

Insights into the deactivation mechanism of metal carbide catalysts for dry reforming of methane via comparison of nickel-modified molybdenum and tungsten carbides

The Ni–WC catalyst showed more stable DRM activity than the Ni–Mo₂C catalyst.

Molybdenum phosphide as a novel and stable catalyst for dry reforming of methane

A novel MoP catalyst exhibited high coking and oxidation resistance for dry reforming of CH₄with CO₂.

A review of dry (CO2) reforming of methane over noble metal catalysts

Dry (CO2) reforming of methane (DRM) is a well-studied reaction that is of both scientific and industrial importance. This reaction produces syngas that can be used to produce a wide range of products, such as higher alkanes and oxygenates by means of Fischer-Tropsch synthesis. DRM is inevitably accompanied by deactivation due to carbon deposition. DRM is also a highly endothermic reaction and requires operating temperatures of 800-1000 °C to attain high equilibrium conversion of CH4 and CO2 to H2 and CO and to minimize the thermodynamic driving force for carbon deposition. The most widely used catalysts for DRM are based on Ni. However, many of these catalysts undergo severe deactivation due to carbon deposition. Noble metals have also been studied and are typically found to be much more resistant to carbon deposition than Ni catalysts, but are generally uneconomical. Noble metals can also be used to promote the Ni catalysts in order to increase their resistance to deactivation. In order to design catalysts that minimize deactivation, it is necessary to understand the elementary steps involved in the activation and conversion of CH4 and CO2. This review will cover DRM literature for catalysts based on Rh, Ru, Pt, and Pd metals. This includes the effect of these noble metals on the kinetics, mechanism and deactivation of these catalysts.