Catalysis is at the core of almost every established and emerging chemical process and also plays a central role in the quest for novel technologies for the sustainable production and conversion of energy. Particularly since the early 2000s, a great surge of interest exists in the design and application of micro- and nanometer-sized materials with hollow interiors as solid catalysts. This review provides an updated and critical survey of the ever-expanding material architectures and applications of hollow structures in all branches of catalysis, including bio-, electro-, and photocatalysis. First, the main synthesis strategies toward hollow materials are succinctly summarized, with emphasis on the (regioselective) incorporation of various types of catalytic functionalities within their different subunits. The principles underlying the scientific and technological interest in hollow materials as solid catalysts, or catalyst carriers, are then comprehensively reviewed. Aspects covered include the stabilizat...

Hollow Nano- and Microstructures as Catalysts

CO2 methanation is a well-known reaction that is of interest as a capture and storage (CCS) process and as a renewable energy storage system based on a power-to-gas conversion process by substitute or synthetic natural gas (SNG) production. Integrating water electrolysis and CO2 methanation is a highly effective way to store energy produced by renewables sources. The conversion of electricity into methane takes place via two steps: hydrogen is produced by electrolysis and converted to methane by CO2 methanation. The effectiveness and efficiency of power-to-gas plants strongly depend on the CO2 methanation process. For this reason, research on CO2 methanation has intensified over the last 10 years. The rise of active, selective, and stable catalysts is the core of the CO2 methanation process. Novel, heterogeneous catalysts have been tested and tuned such that the CO2 methanation process increases their productivity. The present work aims to give a critical overview of CO2 methanation catalyst production and research carried out in the last 50 years. The fundamentals of reaction mechanism, catalyst deactivation, and catalyst promoters, as well as a discussion of current and future developments in CO2 methanation, are also included.

Supported Catalysts for CO2 Methanation: A Review

CO2 hydrogenation to hydrocarbons is a promising way of making waste to wealth and energy storage, which also solves the environmental and energy issues caused by CO2 emissions Much efforts and research are aimed at the conversion of CO2 via hydrogenation to various value-added hydrocarbons, such as CH4, lower olefins, gasoline, or long-chain hydrocarbons catalyzed by different catalysts with various mechanisms This review provides an overview of advances in CO2 hydrogenation to hydrocarbons that have been achieved recently in terms of catalyst design, catalytic performance and reaction mechanism from both experiments and density functional theory calculations In addition, the factors influencing the performance of catalysts and the first C–C coupling mechanism through different routes are also revealed The fundamental factor for product selectivity is the surface H/C ratio adjusted by active metals, supports and promoters Furthermore, the technical and application challenges of CO2 conversion into useful fuels/chemicals are also summarized To meet these challenges, future research directions are proposed in this review

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A short review of recent advances in CO2 hydrogenation to hydrocarbons over heterogeneous catalysts

Catalytic conversion of CO2 to produce fuels and chemicals is attractive in prospect because it provides an alternative to fossil feedstocks and the benefit of converting and cycling the greenhouse gas CO2 on a large scale. In today's technology, CO2 is converted into hydrocarbon fuels in Fischer-Tropsch synthesis via the water gas shift reaction, but processes for direct conversion of CO2 to fuels and chemicals such as methane, methanol, and C2+ hydrocarbons or syngas are still far from large-scale applications because of processing challenges that may be best addressed by the discovery of improved catalysts-those with enhanced activity, selectivity, and stability. Core-shell structured catalysts are a relatively new class of nanomaterials that allow a controlled integration of the functions of complementary materials with optimised compositions and morphologies. For CO2 conversion, core-shell catalysts can provide distinctive advantages by addressing challenges such as catalyst sintering and activity loss in CO2 reforming processes, insufficient product selectivity in thermocatalytic CO2 hydrogenation, and low efficiency and selectivity in photocatalytic and electrocatalytic CO2 hydrogenation. In the preceding decade, substantial progress has been made in the synthesis, characterization, and evaluation of core-shell catalysts for such potential applications. Nonetheless, challenges remain in the discovery of inexpensive, robust, regenerable catalysts in this class. This review provides an in-depth assessment of these materials for the thermocatalytic, photocatalytic, and electrocatalytic conversion of CO2 into synthesis gas and valuable hydrocarbons.

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Core–shell structured catalysts for thermocatalytic, photocatalytic, and electrocatalytic conversion of CO2

The abrupt and massive deactivation of methane dry reforming catalysts especially Ni-based is still a monumental impediment towards its industrialization and commercialization for production of value-added syngas via Fischer-Tropsch process. The need for further and more critical understanding of inherent and tailored interactions of catalyst components for performance and stability enhancement during reforming reaction cannot be over-emphasized. This review provides a contemporary assessment of progresses recorded on synergistic interplay among catalyst components (active metals, support, promoters and binders) during dry reforming using state-of-the-art experimental and theoretical techniques. Advancements achieved during interplay leading to improvements in properties of existing catalysts and discovery of novel ones were stated and expatiated. Reaction pathways, catalytic activities, selection of appropriate synthesis route and metal/support deactivation via sintering or carbon deposition have over time been successfully studied and explained using information from these crucial component interactions. This perspective describes the roles of these interactions and their applications towards development of robust catalysts configurations for successful industrial applications.

A review on catalyst development for dry reforming of methane to syngas: Recent advances

In this paper, a novel sandwiched core–shell structured Ni-SiO2@CeO2 catalyst, with nickel nanoparticles encapsulated between silica and ceria, was developed and applied for dry reforming of biogas (CH4 / CO2 = 3/2) under low temperature conditions to test its coke inhibition properties. Ni-phyllosilicate was used as the Ni precursor in order to produce highly dispersed Ni nanoparticles on SiO2. Cerium oxide was chosen as the shell due to its high redox potential and oxygen storage capacity, that can reduce coke formation under severe dry reforming conditions. The core shell Ni-SiO2@CeO2 catalyst showed excellent coke inhibition property under low temperature (600 °C) reforming of biogas, with no coke detected after a 72 h catalytic run. Under the same conditions, Ni-SiO2 catalyst deactivated within 22 h due to heavy coke formation and reactor blockage, while Ni-CeO2 catalyst showed very low activity. The higher activity of the core–shell catalyst is attributed to its higher Ni dispersion and reducibility. TEM and XRD results show that the core–shell catalyst shows higher resistance to Ni particle sintering and agglomeration during the reaction than the Ni-SiO2 and Ni-CeO2 catalysts. In-situ DRIFTS on the Ni-SiO2@CeO2 catalyst indicate a change in the reaction mechanism from a mono-functional pathway on the Ni-SiO2 catalysts to a bi-functional route on the Ni-SiO2@CeO2 catalyst with active participation of oxygen species from CeO2 in carbon gasification. The confinement effect of the sandwich structure and the bifunctional mechanism of dry reforming are the primary reasons for the excellent coke resistance of the Ni-SiO2@CeO2 catalyst.

Silica–Ceria sandwiched Ni core–shell catalyst for low temperature dry reforming of biogas: Coke resistance and mechanistic insights

Iron–alumina-supported nickel–iron alloy catalysts were tested in a fixed-bed reactor for steam reforming of toluene as a biomass tar model compound. The influence of the calcination temperature of the iron–alumina support was also explored for the steam reforming reaction. Ni supported on an Fe2O3–Al2O3 support calcined at 500 °C [NFA(500)] gave superior catalytic performance in terms of activity and stability over other catalysts. NFA(500) gave a toluene conversion of more than 90% for a period of 26 h with a H2/CO value of 4.5. According to XRD analysis, the Ni–Fe alloys were formed and stable throughout the reforming reaction. It was observed from XPS results that the surface of the reduced NFA(500) catalyst was enriched with Fe species, where the other catalysts were enriched with Ni species. These surface Fe species play the role of cocatalysts by increasing the coverage of oxygen species during the reforming reaction to enhance the reaction of toluene and suppresses coke formation. The presence of ...

Jangam Ashok

Papers

Silica–Ceria sandwiched Ni core–shell catalyst for low temperature dry reforming of biogas: Coke resistance and mechanistic insights

Nickel–Iron Alloy Supported over Iron–Alumina Catalysts for Steam Reforming of Biomass Tar Model Compound

Enhanced activity of CO2 methanation over Ni/CeO2-ZrO2 catalysts: Influence of preparation methods

Steam reforming of toluene as a biomass tar model compound over CeO2 promoted Ni/CaO–Al2O3 catalytic systems

A review of recent catalyst advances in CO2 methanation processes