Ni-FeOx synergy induced by metal-support interaction on Ni-impregnated incineration bottom ash for effective tar reforming

The incineration bottom ash (IBA) was impregnated with nickel to catalyze toluene (tar surrogate) steam reforming. A toluene conversion of >80 % was achieved at 800℃ without activity decay in a 100-h test for 15 %Ni/IBA. An activation stage was observed for Ni/IBA catalysts in the initial 50 ∼ 400 min under different reaction conditions. A series of experiments and characterizations were performed to explore the possible mechanisms for the activation. It was found that the iron species in IBA gradually migrated to the catalyst surface and formed a Ni-FeOx complex owing to the metal-support interaction. The synergy of Ni-FeOx played an important role in improving the activity of Ni/IBA due to the enhanced lattice oxygen activity. Additionally, Ni/IBA catalysts showed a much lower coke deposition rate than Ni/Al2O3 (1.12 vs. 3.45 mg-C/gcat∙h) because of the variable states of FeOx and the abundant basic sites caused by the alkali and alkaline earth metals contained in IBA.

Photodriven Methane Conversion on Transition Metal Oxide Catalyst: Recent Progress and Prospects

Methane as the main component in natural gas is a promising chemical raw material for synthesizing value-added chemicals, but its harsh chemical conversion process often causes severe energy and environment concerns. Photocatalysis provides an attractive path to active and convert methane into various products under mild conditions with clean and sustainable solar energy, although many challenges remain at present. In this review, recent advances in photocatalytic methane conversion are systematically summarized. As the basis of methane conversion, the activation of methane is first elucidated from the structural basis and activation path of methane molecules. The study is committed to categorizing and elucidating the research progress and the laws of the intricate methane conversion reactions according to the target products, including photocatalytic methane partial oxidation, reforming, coupling, combustion, and functionalization. Advanced photocatalytic reactor designs are also designed to enrich the options and reliability of photocatalytic methane conversion performance evaluation. The challenges and prospects of photocatalytic methane conversion are also discussed, which in turn offers guidelines for methane-conversion-related photocatalyst exploration, reaction mechanism investigation, and advanced photoreactor design.

Atomic force microscopy bending tests of a suspended rod-shaped object: Accounting for object fixing conditions

The technique of atomic force microscopy (AFM) bending tests of a suspended nano-object (scroll, tube, rod) makes it possible to calculate the Young's modulus of the material it is made of based on experimental data. However, the calculation results involve a large error due to uncertain conditions (console or bridge) of fixing the test object. One of the ways to reduce this error is based on the theoretical consideration of consoles or bridges as beams with one or two ends resting on Winkler elastic foundations. The beam bending problems have been solved in both cases using Krylov's functions. This has allowed for developing an approach to the analytical identification of fixing conditions and including them in the calculations. The application of the approach is illustrated by AFM measurements of the Young's modulus of MgNi_{2}Si_{2}O_{5}(OH)_{4} nanoscrolls.

Methane Dry Reforming by Ni-Cu Nanoalloys Anchored on Periclase-Phase MgAlOx Nanosheets for Enhanced Syngas Production

Stable and efficient syngas production via methane dry reforming is highly desirable as it utilizes two greenhouse gases simultaneously. In this work, active Ni-Cu nanoalloys stably anchored on periclase-phase MgAlO_x nanosheets were successfully synthesized by a hydrothermal method. These highly dispersed small Ni-Cu alloys strongly interacted with the periclase-phase MgAlO_x nanosheets, on which abundant base sites were accessible. On the optimal catalyst (6Ni6CuMgAl-S), methane and carbon dioxide conversion always reached 85 and 90% at 700 °C under a gas hour speed velocity of 40,000 mL/g_cat h for more than 70 h. The hydrogen production rate was maintained at 1.8 mmol/min, and the ratio of H₂/CO was kept at approximately 0.96 under a CH₄ and CO₂ flow rate of 25 mL/min. Coke deposition and Ni sintering were effectively suppressed by the formation of a Ni-Cu alloy, the laminar structure, and the periclase phase of the MgAlO_x support. Moreover, the alloy nanoparticles were reconstructed into a segregated Ni-Cu alloy structure in response to the reaction environment, and this structure was more stable and still active. Density functional theory calculations showed that carbon adsorption was inhibited on the segregated Ni-Cu alloy. Furthermore, the experimental thermogravimetric and O₂-TPO results confirmed the significant decrease in carbon deposition on the Ni-Cu alloy catalysts.

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.

Altering the influence of ceria oxygen vacancies in Ni/CexSiyO2 for photothermal CO2 methanation

While the benefit of CeO₂ surface oxygen vacancies for CO₂ methanation is well established, their role under photothermal conditions has not been probed in depth.

The dry reforming of methane over fly ash modified with different content levels of MgO

Large amounts of industrial waste fly ash (FA) have caused serious pollution to the environment. There are a few reports that this kind of material, with its good thermal stability, can be used as a catalyst support for high-temperature catalytic reactions, and it has a certain application space. Upon the alkali treatment of fly ash, its specific surface area is increased, and it has the potential to be a catalyst support. Using treated fly ash as the carrier, a nickel-based catalyst was prepared via a sol–gel method, and the catalytic performance changes of catalysts with different MgO content levels in the dry reforming of methane are discussed. Under the conditions of a space velocity of 1.8 × 10⁴ mL g⁻¹ h⁻¹ and a reaction temperature of 750 °C, in the presence of Ni/NaFA-M2 (M2 = 20 wt% MgO), the CH₄ conversion rate can reach 84%, and it has good reaction stability. This will provide a way to use fly ash and carry out more research.

Fly ash is a kind of industrial waste, which is used as carrier to prepare nickel based catalyst. The flow chart of catalyst preparation is shown in the figure.

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.

Lanthanum-Modified MCF-Derived Nickel Phyllosilicate Catalyst for Enhanced CO2 Methanation: A Comprehensive Study

For the traditional preparation method, it is challenging to fabricate a supported nickel catalyst with fine size at high loading. In this work, a group of La-modified mesostructured cellular foam (MCF)-derived nickel phyllosilicates was designed and synthetized by a hydrothermal method followed by an impregnation-modification of La₂O₃, whose Ni contents varied from 25.3 to 32.2 wt %. Both the special property of phyllosilicate and the addition of a La₂O₃ modifier played significant roles in achieving high Ni dispersion and excellent catalytic performance. The formed nickel phyllosilicate was beneficial to obtain small Ni nanoparticles (<5 nm) due to its strong metal-support interaction and high specific surface area; the addition of the La₂O₃ modifier could further reduce the Ni particle size and decrease the reduction difficulty of the fabricated samples. On the contrary, a large Ni particle size of 13.0 nm was observed on the impregnated Ni/MCF (N/M-Im) catalyst with a Ni content of 31.7 wt %. As a result, the nickel phyllosilicate catalyst showed higher catalytic activity than the impregnated one, and the La modifier could further improve the catalytic activity especially at low temperature (<400 °C). Among all catalysts, the modified phyllosilicate catalyst N/M-P-32-5L with 180 °C-32 h-hydrothermal treatment and La₂O₃ content of 5 wt % was the best owing to its small-sized Ni particles, high H₂ and CO₂ chemisorption capacity, large turnover frequency (TOF) value, and low activation energy of 69.83 kJ mol^-1. In addition, the intermediates of formate and CO were detected through in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis. In a 100 h-lifetime test under harsh conditions and 600 °C-steam treatment, N/M-P-32-5L showed both high sintering resistance of Ni particles and high thermal stability without the collapse of pores as well as decrease of catalytic activity, which was attributed to the special physical and chemical properties of MCF-derived nickel phyllosilicate, strong metal-support interaction over the catalyst, and the promotion of the La₂O₃ modifier.

NiYAl-Derived Nanoporous Catalysts for Dry Reforming of Methane

Dry reforming of methane can be used for suppressing the rapid growth of greenhouse gas emissions. However, its practical implementation generally requires high temperatures. In this study, we report an optimal catalyst for low-temperature dry reforming of methane with high carbon coking resistance synthesized from NiYAl alloy. A facile two-step process consisting of preferential oxidation and leaching was utilized to produce structurally robust nanoporous Ni metal and Y oxides from NiYAl₄. The catalyst exhibited an optimal carbon balance (0.96) close to the ideal value of 1.0, indicating the optimized dry reforming pathway. This work proposes a facile route of the structural control of active metal/oxide sites for realizing highly active catalysts with long-term durability.

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.

NiO supported on Y2Ti2O7 pyrochlore for CO2 reforming of CH4: insight into the monolayer dispersion threshold effect on coking resistance

An evident monolayer dispersion threshold effect on coking resistance is observed for NiO/Y₂Ti₂O₇ catalysts in DRM reaction. A catalyst with the best activity and anti-coking ability can be fabricated at the monolayer dispersion capacity.

Experimental Study on Dry Reforming of Biogas for Syngas Production over Ni-Based Catalysts

Syngas production from dry reforming of biogas (DRB) is studied experimentally in this work. Ni/Al₂O₃, Pt/Al₂O₃, and Pt-Ni/Al₂O₃ are used as catalysts to examine the effect of CO₂ content in biogas and H₂O addition on DRB performance for reaction temperatures in the 600-800 °C range. It is found that the bimetallic Pt-Ni catalyst exhibits the best activity and thermal stability among the three types of catalysts studied due to better carbon deposition resistance. Because CO₂ functions as the oxidant in combustion, CH₄ conversion is enhanced when the biogas contains more CO₂. One hundred percent CO₂ conversion can be reached for biogas containing a less amount of CO₂ at high temperatures. With H₂O addition in DRB, the steam reforming of methane (SRM) reaction is the dominant reaction, resulting in higher H₂ and CO yields with biogas containing lesser amounts of CO₂. However, lower CH₄ conversion and negative CO₂ conversion do result. With higher CO₂ content in the biogas, higher CH₄ and CO₂ conversions can be obtained. Lower yields of H₂ and CO are obtained due to less SRM dominance. With H₂O addition in biogas, the H₂/CO ratio with a value greater than 1 can be obtained from DRB. It is also found that the H₂/CO ratio with a value of 2.1 can be obtained for reactant composition with a molar ratio of CH₄/CO₂/H₂O = 1:0.25:1 and reaction temperature of 800 °C.

Synthesis of Ni3Si4O10(OH)2 Porous Microspheres as Support of Pd Catalyst for Hydrogenation Reaction

Nickel phyllosilicates have attracted much attention owing to their potential applications in various fields. Herein, Ni₃Si₄O₁₀(OH)₂ porous microspheres (NiSi-PMs) with a diameter of 1.2 to 3.2 μm were successfully fabricated via a urea-assisted hydrothermal method, and subsequently used to prepare supported Pd catalyst. Characterizations of the NiSi-PMs and the obtained catalyst, combined with the catalytic performance for the hydrogenation reaction, are presented and discussed. The BET surface area and pore volume of the NiSi-PMs were 196.2 m² g^-1 and 0.70 cm³ g^-1, respectively. The Pd/NiSi-PMs catalyst exhibited remarkable catalytic activity for the hydrogenation of styrene under mild conditions, with a turnover frequency of 5234 h^-1, and the catalyst was recovered and recycled for six consecutive cycles without any discernible loss of activity. H₂-TPR and H₂-TPD revealed that the activity of the catalysts was closely related to the adsorption property for hydrogen. The present Ni₃Si₄O₁₀(OH)₂ supported Pd catalyst afforded a promising and competitive candidate for heterogeneous catalysis.

Cation Redistribution along the Spiral of Ni-Doped Phyllosilicate Nanoscrolls: Energy Modelling and STEM/EDS Study

Here, we study the stress-induced self-organization of Mg²⁺ and Ni²⁺ cations in the crystal structure of multiwalled (Mg_1-x ,Ni_x )₃ Si₂ O₅ (OH)₄ phyllosilicate nanoscrolls. The phyllosilicate layer strives to compensate size and surface energy difference between the metal oxide and silica sheets by curling. But as soon as the layer grows, the scrolling mechanism becomes a spent force. An energy model proposes secondary compensation of strain: two cations distribute along the nanoscroll spiral in accordance with preferable radii of curvature. To reveal this, we study synthetic (Mg_1-x ,Ni_x )₃ Si₂ O₅ (OH)₄ nanoscrolls by the scanning transmission electron microscopy/energy-dispersive X-ray spectroscopy (STEM/EDS) technique. For a number of scrolls, we have found indeed a change of Ni concentration with increase in distance from the nanoscroll central axis. The concentration gradient, according to our estimates, can reach 50 at.% over 25 nm of the wall thickness.

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.

Incinerator bottom ash derived from municipal solid waste as a potential catalytic support for biomass tar reforming

Environment-friendly and sustainable routes for municipal solid waste (MSW) incineration bottom ash (IBA) recycling and utilization is one of the major concerns for the urbanized countries like Singapore. In this research paper, the possibility of bulk utilization of MSW-IBA as a catalyst support material has been explored for sustainable syn-gas production. The change in the texture of the IBA with simple hydrothermal treatment using NaOH has also been investigated. Furthermore, with hydrothermal treatment for 24 h at 180 °C, the texture of raw IBA with respect to basicity, surface area, total pore volume and reducibility was greatly improved. These textural properties are highly significant for a material to be utilized as a catalyst or catalytic supports for reforming applications. Ni supported on hydrothermally treated IBA was tested for steam reforming of biomass tar reforming reaction between 700 °C and 800 °C at relatively low steam-to-carbon ratio of 2. Among all the catalysts, Ni supported on IBA hydrothermally treated for 24 h gave stable toluene conversion (of 40%) at 700 °C with reduced coke formation (of 7.5 mgC/g·h) than other catalysts. The superior catalytic performance of this catalyst is mainly due to the presence of high amounts of surface Ni° species and improved reducibility and basicity properties among all. The Raman, DT/TGA and XRD analyses on spent catalysts revealed the deposited carbon during steam reforming of tar reaction is majorly amorphous. Due to this, the deposition of carbon did not show any kind of deactivation within the catalyst testing period.

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.

Synthesis of higher alcohols by CO hydrogenation on a K-promoted Ni–Mo catalyst derived from Ni–Mo phyllosilicate

A K_0.5-(Ni₁Mo_0.25)Si-PS catalyst derived from Ni–Mo phyllosilicate exhibits excellent catalytic performance and stability for the synthesis of HAs by CO hydrogenation relative to the catalysts prepared by conventional co-deposition and wetness impregnation methods.

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.