CO2 Hydrogenation to Renewable Methane on Ni/Ru Modified ZSM-5 Zeolites: The Role of the Preparation Procedure

Mono- and bimetallic Ni- and Ru-modified micro-mesoporous ZSM-5 catalysts were prepared by wet impregnation. The influence of the Ni content, the addition of Ru and the sequence of the modification by two metals on the physicochemical properties of the catalysts were studied. They were characterized by X-ray powder diffraction (XRD), N2 physisorption, temperature-programmed reduction (TPR-TGA), TEM and XPS spectroscopy. Formation of finely dispersed nickel and/or ruthenium oxide species was observed on the external surface and in the pores of zeolite support. It was found that the peculiarity of the used zeolite structure and the modification procedure determine the type of formed metal oxides, their dispersion and reducibility. XPS study revealed that the surface became rich in nickel and poorer in ruthenium for bimetallic catalysts. Ni had higher dispersion in the presence of ruthenium, and TPR investigations also confirmed its facilitated reducibility. The studied catalysts were tested in CO2 hydrogenation to methane. 10Ni5RuZSM-5 material showed the highest activity and high selectivity for methane formation, reaching the equilibrium conversion and 100% selectivity at 400 °C. Stability and reusability of the latter catalyst show that it is appropriate for practical application.

Synergistically Promoting Coking Resistance of a La0.4Sr0.4Ti0.85Ni0.15O3-δ Anode by Ru-Doping-Induced Active Twin Defects and Highly Dispersed Ni Nanoparticles

The development of anodes with highly efficient electrochemical catalysis and good durability is crucial for solid oxide fuel cells (SOFCs). This paper reports a superior Ru-doped La_0.4Sr_0.4Ti_0.85Ni_0.15O_3-δ (L0.4STN) anode material with excellent catalytic activity and good stability. The doping of Ru can inhibit the agglomeration of in situ-exsolved Ni nanoparticles on the surface and induce the formation of abundant multiple-twinned defects in the perovskite matrix, which significantly increase the concentration of oxygen vacancies. The reduced L0.4STRN (R-L0.4STRN) anode shows an area-specific resistance (ASR) of 0.067 Ω cm² at 800 °C, which is only about one-third of that of stochiometric R-L0.6STN (0.212 Ω cm²). A single cell with the R-L0.4STRN anode shows excellent stability (∼50 h at 650 °C) in both H₂ and CH₄. Furthermore, R-L0.4STRN exhibits outstanding resistance to carbon deposition, which can be attributed to the synergistic effect of highly dispersed Ni nanoparticles and active twinned defects induced by Ru doping.

Unveiling the mechanism of methylcellulose-templated synthesis of Al2O3 microspheres with organic solvents as swelling agents in microchannel

Herein, we report a systematic investigation of the preparation of large-pore-volume Al₂O₃ microspheres using a complex synthesis system with methylcellulose (MC) as the template and gelation initiator and organic solvents as the swelling agent and carrier medium under the flow characteristics of a coaxial microchannel. The adsorption of MC micelles on boehmite colloidal nanoparticles (NPs) was proven and determined by interfacial tension measurements, dynamic light scattering, and cryogenic transmission electron microscopy. Isothermal titration calorimetry demonstrated that the adsorption process was caused by nonspecific hydrophobicity; one binding site was involved, and the affinity constant was 1060 M^-1. When the MC:NPs mass ratio exceeded 0.1, the template-NP bridged each other to form large aggregates, thereby forming large mesopores and enhancing the gelation speed. Alkanes, alcohols, and amines were applied to further enhance the porosity, and the swelling capacities were investigated experimentally and theoretically. Amines were efficient swelling agents owing to their excellent ability to swell MC micelles and insert into the acid colloid network. The coaxial microchannel was subjected to molding; this process significantly influenced the morphology and textural properties owing to the internal circulation during droplet formation. When trihexylamine with suitable steric hindrance, alkalinity, and polarity was used as the swelling agent, the microspheres exhibited an optimal specific surface area of 403 m²/g and a pore volume of 1.85 cm³/g.

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.

Experimental Study on CO2 Methanation over Ni/Al2O3, Ru/Al2O3, and Ru-Ni/Al2O3 Catalysts

CO2 methanation is recognized as one of the best technologies for storing intermittent renewable energy in the form of CH4. In this study, CO2 methanation performance is investigated using Ni/Al2O3, Ru/Al2O3, and Ru-Ni/Al2O3 as the catalysts under conditions of atmospheric pressure, a molar ratio of H2/CO2 = 5, and a space velocity of 5835 h−1. For reaction temperatures ranging from 250 to 550 °C, it was found that the optimum reaction temperature is 400 °C for all catalysts studied. At this temperature, the maximum values of CO2 conversion, H2 efficiency, and CH4 yield and lowest CO yield can be obtained. With temperatures higher than 400 °C, reverse CO2 methanation results in CO2 conversion and CH4 yield decreases with increased temperature, while CO is formed due to reverse water-gas shift reaction. The experimental results showed that CO2 methanation performance at low temperatures can be enhanced greatly using the bimetallic Ru-Ni catalyst compared with the monometallic Ru or Ni catalyst. Under ascending-descending temperature changes between 250 °C and 550 °C, good thermal stability is obtained from Ru-Ni/Al2O3 catalyst. About a 3% decrease in CO2 conversion is found after three continuous cycles (74 h) test.

The Role of Alkali and Alkaline Earth Metals in the CO2 Methanation Reaction and the Combined Capture and Methanation of CO2

CO2 methanation has great potential for the better utilization of existing carbon resources via the transformation of spent carbon (CO2) to synthetic natural gas (CH4). Alkali and alkaline earth metals can serve both as promoters for methanation catalysts and as adsorbent phases upon the combined capture and methanation of CO2. Their promotion effect during methanation of carbon dioxide mainly relies on their ability to generate new basic sites on the surface of metal oxide supports that favour CO2 chemisorption and activation. However, suppression of methanation activity can also occur under certain conditions. Regarding the combined CO2 capture and methanation process, the development of novel dual-function materials (DFMs) that incorporate both adsorption and methanation functions has opened a new pathway towards the utilization of carbon dioxide emitted from point sources. The sorption and catalytically active phases on these types of materials are crucial parameters influencing their performance and stability and thus, great efforts have been undertaken for their optimization. In this review, we present some of the most recent works on the development of alkali and alkaline earth metal promoted CO2 methanation catalysts, as well as DFMs for the combined capture and methanation of CO2.

Nano-Ru Supported on Ni Nanowires for Low-Temperature Carbon Dioxide Methanation

In this study, we investigated the catalytic performance of Ru nanoparticles (NPs) supported on Ni-nanowires for the first time. This appears to be a highly efficient catalyst for low-temperature methanation, e.g., ca. 100% conversion and 100% of CH4 selectivity can be achieved at ca. 179 °C, while the turnover frequency (TOF) value was 2479.2 h−1. At the same time, the onset of a reaction was observed at a temperature as low as 130 °C. The comparison of nano-Pd and nano-Ru supported on Ni-nanowires enabled us to prove that oxidized surface metals are highly important for the high activity of the investigated nano-Ru@nanowired-Ni. Moreover, similar to the microscopic Sabatier rule, which indicates that some optimal reactivity level of a catalyst exists, we showed that Ni-nanowires (a higher specific surface area than a standard metal surface, e.g., in the form of a metal foam, but lower than nano-sized materials) significantly enhances the performance of the Ru-Ni catalytic system.

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.

Tuning the Selectivity of LaNiO3 Perovskites for CO2 Hydrogenation through Potassium Substitution

Herein, we demonstrate a method used to tune the selectivity of LaNiO3 (LNO) perovskite catalysts through the substitution of La with K cations. LNO perovskites were synthesised using a simple sol-gel method, which exhibited 100% selectivity towards the methanation of CO2 at all temperatures investigated. La cations were partially replaced by K cations to varying degrees via control of precursor metal concentration during synthesis. It was demonstrated that the reaction selectivity between CO2 methanation and the reverse water gas shift (rWGS) could be tuned depending on the initial amount of K substituted. Tuning the selectivity (i.e., ratio of CH4 and CO products) between these reactions has been shown to be beneficial for downstream hydrocarbon reforming, while valorizing waste CO2. Spectroscopic and temperature-controlled desorption characterizations show that K incorporation on the catalyst surface decrease the stability of C-based intermediates, promoting the desorption of CO formed via the rWGS prior to methanation.

Analysis of Research Status of CO2 Conversion Technology Based on Bibliometrics

The concentration of carbon dioxide in the air has risen sharply due to the use of fossil fuels, causing environmental problems such as the greenhouse effect, which seriously threatens humans’ living environment. Reducing carbon dioxide emissions while addressing energy shortages requires the conversion of CO2 into high added-value products. In this paper, the status of CO2 conversion research in the past ten years is analyzed using the bibliometric method; the influence of countries and institutions, journal article statistics and other aspects are statistically analyzed, and the research status of carbon dioxide catalytic conversion is briefly introduced. Finally, according to the analysis results and the existing problems of CO2 catalytic conversion research, the future development direction of CO2 catalytic conversion research is prospected.

CO2 Methanation over Hydrotalcite-Derived Nickel/Ruthenium and Supported Ruthenium Catalysts

In this work, in-house synthesized NiMgAl, Ru/NiMgAl, and Ru/SiO2 catalysts and a commercial ruthenium-containing material (Ru/Al2O3com.) were tested for CO2 methanation at 250, 300, and 350 °C (weight hourly space velocity, WHSV, of 2400 mLN,CO2·g−1·h−1). Materials were compared in terms of CO2 conversion and CH4 selectivity. Still, their performances were assessed in a short stability test (24 h) performed at 350 °C. All catalysts were characterized by temperature programmed reduction (TPR), X-ray diffraction (XRD), N2 physisorption at −196 °C, inductively coupled plasma optical emission spectrometry (ICP-OES), and H2/CO chemisorption. The catalysts with the best performance (i.e., the hydrotalcite-derived NiMgAl and Ru/NiMgAl) seem to be quite promising, even when compared with other methanation catalysts reported in the literature. Extended stability experiments (240 h of time-on-stream) were performed only over NiMgAl, which was selected based on catalytic performance and estimated price criteria. This catalyst showed some deactivation under conditions that favor CO formation (high temperature and high WHSV, i.e., 350 °C and 24,000 mLN,CO2·g−1·h−1, respectively), but at 300 °C and low WHSV, excellent activity (ca. 90% of CO2 conversion) and stability, with nearly complete selectivity towards methane, were obtained.

Deactivation mechanism of hydrotalcite-derived Ni–AlOx catalysts during low-temperature CO2 methanation via Ni-hydroxide formation and the role of Fe in limiting this effect

Ni–Fe/AlO_x with nanosheet structure, enhance the reducibility and stability of the Ni-hydroxide during the catalytic reaction due to the formation of spinel phase which stabilize smaller Ni nanoparticle with a weaker interaction with the support.

Design of highly active cobalt catalysts for CO2 hydrogenation via the tailoring of surface orientation of nanostructures

Catalyst design by tuning surface structures to suppress unreactive species in order to achieve higher reactivity for CO₂ conversion.

Collateral hydrogenation over proton-conducting Ni/BaZr0.85Y0.15O3−δ catalysts for promoting CO2 methanation

Despite the importance of CO₂ methanation for eco-friendly carbon-neutral fuel recycling, the current technologies, relying on catalytic hydrogenation over metal-based catalysts, face technological and economical limitations. Herein, we employ the steam hydrogenation capability of proton conductors to achieve collateral CO₂ methanation over the Ni/BaZr_0.85Y_0.15O_3−δ catalyst, which is shown to outperform its conventional Ni/Al₂O₃ counterpart in terms of CH₄ yield (8% higher) and long-term stability (3% higher for 150 h) at 400 °C while exhibiting a CH₄ selectivity above 98%. Moreover, infrared and X-ray photoelectron spectroscopy analyses reveal the appearance of distinct mobile proton-related OH bands during the methanation reaction.

A novel steam hydrogenation process is demonstrated by applying collateral CO₂ methanation over Ni/BaZr_0.85Y_0.15O_3−δ, which outperforms its conventional Ni/Al₂O₃ counterpart.

CAT-ACT-A new highly versatile x-ray spectroscopy beamline for catalysis and radionuclide science at the KIT synchrotron light facility ANKA

CAT-ACT-the hard X-ray beamline for CATalysis and ACTinide/radionuclide research at the KIT synchrotron radiation facility ANKA-is dedicated to X-ray spectroscopy, including "flux hungry" photon-in/photon-out and correlative techniques and combines state-of-the-art optics with a unique infrastructure for radionuclide and catalysis research. Measurements can be performed at photon energies varying between 3.4 keV and 55 keV, thus encompassing the actinide M- and L-edge or potassium K-edge up to the K-edges of the lanthanide series such as cerium. Well-established X-ray absorption fine structure spectroscopy in transmission and fluorescence detection modes is available in combination with high energy-resolution X-ray emission spectroscopy or X-ray diffraction techniques. The modular beamline design with two alternately operated in-line experimental stations enables sufficient flexibility to adapt sample environments and detection systems to many scientific challenges. The ACT experimental station focuses on various aspects of nuclear waste disposal within the mission of the Helmholtz association to contribute to the solution of one of the greatest scientific and social challenges of our time-the safe disposal of heat producing, highly radioactive waste forms from nuclear energy production. It augments present capabilities at the INE-Beamline by increasing the flux and extending the energy range into the hard X-ray regime. The CAT experimental station focuses on catalytic materials, e.g., for energy-related and exhaust gas catalysis. Characterization of catalytically active materials under realistic reaction conditions and the development of in situ and operando cells for sample environments close to industrial reactors are essential aspects at CAT.

Environmentally benign selective hydrogenation of α,β-unsaturated aldehydes and reduction of aromatic nitro compounds using Cu based bimetallic nanoparticles supported on multiwalled carbon nanotubes and mesoporous carbon

The catalytic activity of these materials was investigated in the hydrogenation of α,β-unsaturated aldehydes and reduction of aromatic nitro compounds using different hydrogen sources.

Recent advances in methanation catalysts for the production of synthetic natural gas

This review summarizes the recent progress in methanation catalysts for SNG production, which will provide insights for future catalysts design.

Enhancing catalytic activity and stability for CO2 methanation on Ni@MOF-5 via control of active species dispersion

A novel high active catalyst Ni@MOF-5 showed unexpected higher activity under the low temperature for CO₂ methanation. The characterization results indicated that Ni was in highly dispersed uniform state over MOF-5. This catalyst performed high stability and showed almost no deactivation in long term stability tests up to 100 h.

Nickel-promoted mesoporous ZSM5 for carbon monoxide methanation

Synergistic effect of Ni and the mZSM5 support led to high methanation activity of Ni/mZSM5. Two possible reaction routes emerged: (1) adsorbed CO may be reacted with H₂ to form CH₄ and H₂O; (2) adsorbed H may be reacted with CO to form CH₄ and CO₂.

The difference of roles of alkaline-earth metal oxides on silica-supported nickel catalysts for CO2 methanation

Modification of alkaline-earth oxides to Ni/SiO₂ catalyst could affect significantly the reducibility of Ni species under the given reduction conditions.