Simultaneous tuning porosity and basicity of nickel@nickel-magnesium phyllosilicate core-shell catalysts for CO₂ reforming of CH₄

Alloying Ni-Cu Nanoparticles Encapsulated in SiO2 Nanospheres for Synergistic Catalysts in CO2 Reforming with Methane Reaction

In this work, we studied CO2 reforming with the methane (CRM) reaction over Ni-Cu alloy nanoparticles encapsulated in SiO2 nanospheres, for which combinational functions of alloy effect, size effect, metal-support interaction, and confinement effect exhibited high performance, good sintering resistance, and trace carbon deposition in CRM. The appropriate Cu-addition catalysts 0.2Cu-Ni@SiO2 and 0.5Cu-Ni@SiO2 had smaller NiCu alloy nanoparticles and a stronger metal-support interaction, exhibiting a better performance than the excessive Cu-addition catalysts 1.5Cu-Ni@SiO2 and 3Cu-Ni@SiO2 having Cu clusters and a weaker metal-support interaction. The best synergy of alloy effect, size effect, confinement effect, and metal-support interaction in the 0.5Cu-Ni@SiO2 catalyst contributed to the highest rates of CH4 and CO2 in CRM reported so far. This work demonstrates the importance of appropriate Cu addition in Ni-Cu@SiO2 catalysts, and the synergy for perfectly resolving sintering and carbon deposition in CRM.

Recent Developments in Dielectric Barrier Discharge Plasma-Assisted Catalytic Dry Reforming of Methane over Ni-Based Catalysts

The greenhouse effect is leading to global warming and destruction of the ecological environment. The conversion of carbon dioxide and methane greenhouse gases into valuable substances has attracted scientists’ attentions. Dry reforming of methane (DRM) alleviates environmental problems and converts CO2 and CH4 into valuable chemical substances; however, due to the high energy input to break the strong chemical bonds in CO2 and CH4, non-thermal plasma (NTP) catalyzed DRM has been promising in activating CO2 at ambient conditions, thus greatly lowering the energy input; moreover, the synergistic effect of the catalyst and plasma improves the reaction efficiency. In this review, the recent developments of catalytic DRM in a dielectric barrier discharge (DBD) plasma reactor on Ni-based catalysts are summarized, including the concept, characteristics, generation, and types of NTP used for catalytic DRM and corresponding mechanisms, the synergy and performance of Ni-based catalysts with DBD plasma, the design of DBD reactor and process parameter optimization, and finally current challenges and future prospects are provided.

Copper Phyllosilicates-Derived Catalysts in the Production of Alcohols from Hydrogenation of Carboxylates, Carboxylic Acids, Carbonates, Formyls, and CO2: A Review

Copper phyllosilicates-derived catalysts (CuPS-cats) have been intensively explored in the past two decades due to their promising activity in carbonyls hydrogenation. However, CuPS-cats have not been completely reviewed. This paper focuses on the aspects concerning CuPS-cats from synthesis methods, effects of preparation conditions, and dopant to catalytic applications of CuPS-cats. The applications of CuPS-cats include the hydrogenation of carboxylates, carboxylic acids, carbonates, formyls, and CO2 to their respective alcohols. Besides, important factors such as the Cu dispersion, Cu+ and Cu0 surface areas, particles size, interaction between Cu and supports and dopants, morphologies, and spatial effect on catalytic performance of CuPS-cats are discussed. The deactivation and remedial actions to improve the stability of CuPS-cats are summarized. It ends up with the challenges and prospective by using this type of catalyst.

Constructing Ni-based confinement catalysts with advanced performances toward the CO2 reforming of CH4: state-of-the-art review and perspectives

The concept of Ni-based confinement catalysts has been proposed and developed to address the challenge of the thermal sintering of metallic Ni active sites during CRM by the space and/or lattice confinement effects.

Smart Designs of Anti-Coking and Anti-Sintering Ni-Based Catalysts for Dry Reforming of Methane: A Recent Review

Dry reforming of methane (DRM) reaction has drawn much interest due to the reduction of greenhouse gases and production of syngas. Coking and sintering have hindered the large-scale operations of Ni-based catalysts in DRM reactions at high temperatures. Smart designs of Ni-based catalysts are comprehensively summarized in fourth aspects: surface regulation, oxygen defects, interfacial engineering, and structural optimization. In each part, details of the designs and anti-deactivation mechanisms are elucidated, followed by a summary of the main points and the recommended strategies to improve the catalytic performance, energy efficiency, and utilization rate.

Low Temperature CO2 Reforming with Methane Reaction over CeO2-Modified Ni@SiO2 Catalysts

Developing high performance catalysts for the low temperature CO₂ reforming with methane (CRM) reaction is a challenge due to the occurrences of metal sintering and carbon deposition. In this study, we synthesized CeO₂ modified Ni@SiO₂ catalysts with excellent properties of sintering-resistance and low carbon deposition for high performance low temperature CRM. The Ni@SiO₂-CeO₂ catalysts displayed a size effect from tiny Ni nanoparticles to enhance CRM performance and a confinement effect from silica encapsulation to limit Ni sintering and exhibited oxygen storage capacity from ceria to reduce carbon deposition. Performance and characterization results revealed that the Ni@SiO₂-CeO₂-W catalyst with smaller ceria size exhibited higher performance and lower carbon deposition than the Ni@SiO₂-CeO₂-E catalyst with bigger ceria size, because the smaller ceria nanoparticles activated more CO₂. This work provided a simple strategy to deposit small sized ceria on the Ni@SiO₂ catalyst surface for the performance enhancement of low temperature CRM.

In Situ X-ray Microscopy Reveals Particle Dynamics in a NiCo Dry Methane Reforming Catalyst under Operating Conditions

Herein, we report the synthesis of a γ-Al₂O₃-supported NiCo catalyst for dry methane reforming (DMR) and study the catalyst using in situ scanning transmission X-ray microscopy (STXM) during the reduction (activation step) and under reaction conditions. During the reduction process, the NiCo alloy particles undergo elemental segregation with Co migrating toward the center of the catalyst particles and Ni migrating to the outer surfaces. Under DMR conditions, the segregated structure is maintained, thus hinting at the importance of this structure to optimal catalytic functions. Finally, the formation of Ni-rich branches on the surface of the particles is observed during DMR, suggesting that the loss of Ni from the outer shell may play a role in the reduced stability and hence catalyst deactivation. These findings provide insights into the morphological and electronic structural changes that occur in a NiCo-based catalyst during DMR. Further, this study emphasizes the need to study catalysts under operating conditions in order to elucidate material dynamics during the reaction.

Coking-resistant dry reforming of methane over BN–nanoceria interface-confined Ni catalysts

Coking-resistant dry reforming of methane over BN–nanoceria interface-confined Ni catalysts was demonstrated.

Catalytic mixed conducting ceramic membrane reactors for methane conversion

Schematic of catalytic mixed conducting ceramic membrane reactors for various reactions: (a) O₂ permeable ceramic membrane reactor; (b) H₂ permeable ceramic membrane reactor; (c) CO₂ permeable ceramic membrane reactor.

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

An in-depth assessment of properties of core–shell catalysts and their application in the thermocatalytic, photocatalytic, and electrocatalytic conversion of CO₂into synthesis gas and valuable hydrocarbons.

Topologically immobilized catalysis centre for long-term stable carbon dioxide reforming of methane

A rooted catalyst, Ni#Y₂O₃, successfully inhibits the growth of carbon nanotubes in DRM.

Methane reforming at low temperatures is of growing importance to mitigate the environmental impact of the production of synthesis gas, but it suffers from short catalyst lifetimes due to the severe deposition of carbon byproducts. Herein, we introduce a new class of topology-tailored catalyst in which tens-of-nanometer-thick fibrous networks of Ni metal and oxygen-deficient Y₂O₃ are entangled with each other to form a rooted structure, i.e., Ni#Y₂O₃. We demonstrate that the rooted Ni#Y₂O₃ catalyst stably promotes the carbon-dioxide reforming of methane at 723 K for over 1000 h, where the performance of traditional supported catalysts such as Ni/Y₂O₃ diminishes within 100 h due to the precluded mass transport by accumulated carbon byproducts. In situ TEM demonstrates that the supported Ni nanoparticles are readily detached from the support surface in the reaction atmosphere, and migrate around to result in widespread accumulation of the carbon byproducts. The long-term stable methane reforming over the rooted catalyst is ultimately attributed to the topologically immobilized Ni catalysis centre and the synergistic function of the oxygen-deficient Y₂O₃ matrix, which successfully inhibits the accumulation of byproducts.

Highly coke resistant Mg-Ni/Al2O3 catalyst prepared via a novel magnesiothermic reduction for methane reforming catalysis with CO2: the unique role of Al-Ni intermetallics

Addition of alkaline promoters is considered to be an effective way to improve the coking resistance of the metal/support composite catalysts for dry reforming of methane (DRM). The traditional metal/promoter/support composites for DRM catalysis are generally obtained from alkaline species impregnation and then high temperature H2 reduction. This two-step process leads to a random distribution of metal-promoter interaction. We herein report a novel magnesiothermic method to reduce Ni from spinel precursor and introduce alkaline Mg(ii) into the composite at the same time, which also gratifies the interaction between the promoter and metal nanoparticles (NPs). The reaction paths to Mg reduction are proposed. The as prepared catalysts show good activity and outstanding coking resistance in DRM. The Ni-Al intermetallics in the catalyst were found for the first time to play an important role in coking resistance as they can be in situ transformed into Ni nanoparticles and MgAl2O4 with strong metal-support interaction during the DRM.

Performance and structural features of LaNi0.5Co0.5O3 perovskite oxides for the dry reforming of methane: influence of the preparation method

LaNiO₃ and LaNi_0.5Co_0.5O₃ as perovskites were synthesized in magnetized and non-magnetized water and the activity of the catalysts was evaluated in the methane dry reforming reaction with CO₂.

Nanoporous Nickel Composite Catalyst for the Dry Reforming of Methane

The development of efficient catalysts with high activities and durabilities for use in the dry reforming of methane (DRM) is desirable but challenging. We report the development of a nanoporous nickel composite (nanoporous Ni/Y₂O₃) via a facile one-step dealloying technique, for use in the DRM. Focusing on the low-temperature DRM, our composite possessed remarkable activity and durability against coking compared with conventional particle-based Ni catalysts. This was attributed to the aluminum oxides present on the Ni surface, which suppress pore coarsening. In addition, the inert bundled Y₂O₃ nanowires are suitable for use as substrates for nanoporous Ni.

Facile synthesis of metal nanoparticles decorated magnetic hierarchical carbon microtubes with polydopamine-derived carbon layer for catalytic applications

It is highly desirable but challenging to fabricate a unique hybrid material comprising nanosized copper/cobalt/nickel nanoparticles (NPs) uniformly distributed on magnetic supports. Herein in this work, hierarchical magnetic metal silicate hollow microtubes were prepared using silica coated magnetic N-doped carbon microtubes (NCMTs@Fe3O4@SiO2) as a chemical template; then polydopamine (PDA) was employed to coat onto magnetic metal silicate carbon microtubes (NCMTs@Fe3O4@CuSNTs/CoSNTs/NiSNTs), which can be carbonized to form hierarchical hybrid composites with uniformly-dispersed metallic copper/cobalt/nickel NPs embedded in PDA-derived carbon layers (NCMTs@Fe3O4@SiO2@C/Cu-Co-Ni). Owing to its hierarchical structure, large specific surface area as well as the high density of metal NPs, the resultant NCMTs@Fe3O4@SiO2@C/Ni-Co-Cu could be applied as catalysts towards the reduction of 4-nitrophenol (4-NP). Furthermore, the NCMTs@Fe3O4@SiO2@C/Ni-Co-Cu catalysts could be easily collected and separated by applying an external magnetic field. In particular, it was found that NCMTs@Fe3O4@SiO2@C/Ni exhibited ultra-high catalytic activity on 4-NP reduction in comparison with Cu and Co supported catalysts. In addition, this unique hierarchical structure combined with magnetic recyclability make NCMTs@Fe3O4@SiO2@C/Ni a highly promising candidate for diverse applications.

Understanding the performance and mechanism of Mg-containing oxides as support catalysts in the thermal dry reforming of methane

Dry reforming of methane (DRM) is one of the more promising methods for syngas (synthetic gas) production and co-utilization of methane and carbon dioxide, which are the main greenhouse gases. Magnesium is commonly applied in a Ni-based catalyst in DRM to improve catalyst performance and inhibit carbon deposition. The aim of this review is to gain better insight into recent developments on the use of Mg as a support or promoter for DRM catalysts. Its high basicity and high thermal stability make Mg suitable for introduction into the highly endothermic reaction of DRM. The introduction of Mg as a support or promoter for Ni-based catalysts allows for good metal dispersion on the catalyst surface, which consequently facilitates high catalytic activity and low catalyst deactivation. The mechanism of DRM and carbon formation and reduction are reviewed. This work further explores how different constraints, such as the synthesis method, metal loading, pretreatment, and operating conditions, influence the dry reforming reactions and product yields. In this review, different strategies for enhancing catalytic activity and the effect of metal dispersion on Mg-containing oxide catalysts are highlighted.

Silica-based micro- and mesoporous catalysts for dry reforming of methane

With wide availability, high thermal stability and high specific surface area, silica-based micro- and mesoporous materials show promising performance for dry reforming of methane reaction, boosting efficient and sustainable utilization of greenhouse gases.

Ni-phyllosilicate structure derived Ni–SiO2–MgO catalysts for bi-reforming applications: acidity, basicity and thermal stability

In this work, Ni–SiO₂–MgO materials synthesized via Ni-phyllosilicate (PS) intermediates were explored for bi-reforming of methane (BRM) reaction.

Multi-Ni@Ni phyllosilicate hollow sphere for CO2 reforming of CH4: influence of Ni precursors on structure, sintering, and carbon resistance

Multi-Ni@Ni phyllosilicate hollow spheres synthesized with Ni(acac)₂ precursor via hydrothermal and H₂ reduction method have unique pore structure and strong interaction between Ni and Ni phyllosilicate which help prevent Ni sintering and carbon deposition, yielding excellent catalytic performance for CO₂ reforming of CH₄ reaction.

Sintering resistant Ni nanoparticles exclusively confined within SiO2 nanotubes for CH4 dry reforming

Ni nanoparticles are exclusively confined within the channels of SiO₂ nanotubes (NTs) using the Ni phyllosilicate@SiO₂ nanocomposite as a precursor where Ni phyllosilicate will in situ decompose into Ni nanoparticles within SiO₂ shell NTs, exhibiting good sintering and carbon resistance for CO₂ reforming of CH₄ reaction.

Geometric design of a Ni@silica nano-capsule catalyst with superb methane dry reforming stability: enhanced confinement effect over the nickel site anchoring inside a capsule shell with an appropriate inner cavity

Ni particles confined in sealed nano-capsule shells with anchoring effect demonstrate improved catalytic performance.

Sc promoted and aerogel confined Ni catalysts for coking-resistant dry reforming of methane

Sc promoted and aerogel confined Ni catalysts were developed for coking-resistant dry reforming of methane.

In situ preparation of Ni nanoparticles in cerium-modified silica aerogels for coking- and sintering-resistant dry reforming of methane

Ni nanoparticles in nanochannels of cerium-modified silica aerogels were in situ prepared for coking-resistant dry reforming of methane.

Ratio-controlled synthesis of phyllosilicate-like materials as precursors for highly efficient catalysis of the formyl group

The design and development of heterogeneous catalysts is very critical for the synthesis of various chemicals and fuels derived from superfluous biomass.