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Active and selective structured RuO/AlO catalysts for CO methanation using a flow simulating CO-rich reformate gases from WGS and PROX units (H excess, CO presence and 300 ppm CO concentration) were prepared. Both, the RuO/AlO powder and the slurry prepared from it for its structuration by washcoating of the metallic micromonolithic structure, were also active and selective. Both the slurry (S-RuAl) and micromonoliths (M-RuAl) were able to completely and selectively methanate CO at much lower temperatures than the parent RuAl powder. The optimal working temperature in which the CO conversion is maximum and the CO conversion is minimized was determined to be from 149 °C to 239 °C for S-RuAl and from 165 °C to 232 °C for M-RuAl, whilst it was from 217 °C to 226 °C for RuAl powder. TPR, XRD and TEM measurements confirmed that the changes in the activity and selectivity for CO methanation among the considered catalysts can be related with modifications in the surface particle size of ruthenium and its reducibility. These were ascribed to the metallic substrate, the presence of PVA and colloidal alumina in the slurry preparation, the aqueous and acidic media and the thermal treatment used, resulting in a more active and selective catalysts than the parent powder.

The Integrated Carbon Capture and Utilization-Methanation (ICCU-Methanation) requires a Dual Function Material (DFM), which firsts captures CO2 and then converts it into CH4, working in alternating adsorption and hydrogenation periods. The ICCU technology can be applied directly to a flue gas leaving a combustion chamber, which usually contains oxidizing species such as oxygen and nitrogen oxides. In this work, the stability of a DFM with composition 4%Ru-8%Na2CO3-8%CaO/Al2O3 is studied for the CO2 adsorption and hydrogenation in alternate cycles including O2 (0–10%) and NOx (0–2000 ppm) during the adsorption period. The variation of CO2 concentration in the usual range of flue gases (5–15%) has little influence on the global performance of the ICCU technology. However, the incorporation of O2 during the adsorption period decreases the production of CH4, and this decrease is even accentuated with increasing the oxygen concentration. This fact is mainly attributed to the oxidation of metal sites that limits the reduction behavior. On the other hand, the addition of NOx competes with CO2 for the basic adsorption sites, which slightly limits the amount of CO2 stored, and consequently the production of CH4. Helpfully, the proposed DFM presents high stability during the 207 cycles here performed, which corresponds to 34 h of time-on-stream, including different CO2 concentrations, and in the presence or absence of O2 and/or NOx. It is concluded that the proposed DFM formulation is competent for long-term operation in the presence of O2 and NOx during the CO2 adsorption period. The financial support from the Science and Innovation Spanish Ministry (PID2019-105960RB-C21) and the Basque Government (IT1509-22) is acknowledged. The authors thank for technical and human support provided by SGIker (UPV/EHU Advanced Research Facilities/ ERDF, EU).

[EN] The performance of nickel supported on lanthana-modified hydroxyapatite (HAP) catalysts is investigated in the CO2 methanation. The addition of La (1-6.6 wt%) leads to a surface enrichment following a sequential multilayer deposition model. Moreover, La addition systematically improves the dispersion of Ni particles and their reducibility, which in turn increases spectacularly the amounts of basic sites and their thermal stability. Such physicochemical changes impact positively on the activity of the catalysts in CO2 methanation. The estimated turnover frequency (TOF) suggest that the small Ni particles are the most efficient. The latter seem to provide a large density of very active defects on Ni-La2O3 interface. The optimized catalyst proves to be highly resistant to deactivation during 100 h time-on-stream (TOS). The samples were also assayed as dual function materials (DFMs) for CO2 adsorption and methanation. A scheme is proposed to describe the different steps involved in a CO2 adsorption/hydrogenation cycle. The financial support from the Science and Innovation Spanish Ministry (PID2019-105960RB-C21) and the Basque Government (IT1297-19) is acknowledged. The authors also acknowledge the technical support provided by SGIker (UPV/EHU Advanced Research Facilities/ERDF, EU) .

[EN] CO2 methanation could play a significant role in the future energy system. The excess of renewable electric energy can be transformed into storable methane to balance the energy demand when required. Moreover, the CO2 methanation can be performed alternating steps of CO2 storage and reduction, avoiding expensive CO2 purification steps. In this work, we will use a previously developed and validated model to optimize by simulation the CO2 adsorption and hydrogenation cycles timing (t(CO2)/t(H2)). The performance of the catalyst is quantified by the CO2 conversion (X-CO2, %), H-2 conversion (X-H2, %) and CH4 production (Y-CH4, mmol g(-1) cycle(-1)). Long adsorption and hydrogenation times result in high CH4 productions per cycle, however, low CO2 and H-2 conversion. Therefore, adsorption times close to the catalyst saturation (t(CO2)=60 s) and moderate hydrogenation times are preferable. To better select the optimal hydrogenation time, a new catalytic parameter is set, the average formation rate of CH4 (rCH(4), mu mol g(-1) s(-1)). The optimal hydrogenation time is set at 120 s. In addition to having a high average formation rate of CH4, t(CO2)/t(H2)= 60/120 cycle timing would allow to work with three identical beds in parallel, one in adsorption mode and two in regenerating mode. With the optimum cycle timing of 60/120 the production of CH4 results in 148 mu mol g(-1) cycle(-1) (1.2 mu mol CH4 g(-1) s(-1)) and a CO2 and H-2 conversion of 25% and 43%, respectively The financial support from the Economy and Competitiveness Spanish Ministry (CTQ2015-67597-C2-1-R and PID2019-105960RB-C21) and the Basque Government (IT1297-19) is acknowledged. The authors thank for technical and human support provided by SGIker (UPV/EHU Advanced Research Facilities/ ERDF, EU). One of the authors (ABL) also acknowledges the Economy and Competitiveness Spanish Ministry for his PhD grant (BES-2016-077855).

Hollow-structured SiO2, which comprises a void space inside a distinct shell with its intriguing physicochemical properties and huge potential, has been widely applied in many methanation catalysts. However, the common methods for preparing SiO2 hollow microspheres are cumbersome and time consuming. Highly uniform hollow nanoflowers, silica (SiO2) nanospheres with different sizes, were synthesised through a rapid, time-saving method known as flash nanoprecipitation. An assembling particle mechanism of the hollow structure of Mo–polydopamine complex was established and tetraethyl orthosilicate underwent uniform hydrolysis on the surface of the hierarchical structure. Spherical SiO2 samples with different morphologies were prepared as catalyst carriers, and Ni-based methanation catalysts were prepared using an impregnation method. Ni particles with size of 3 nm were successfully attached to the surface of MoDo–H–SiO2, while the particle sizes of Ni on CTS–MoDo–H–SiO2 was 7 nm. The small particles (3 nm) were found to significantly increase in size (20–50 nm), decrease by 90% in stability test with a weight hourly space velocity (WHSV) of 26,000 mL.g−1.h−1, which is detrimental to catalyst stability. However, the medium sized particles (7 nm) remained confined via a suitable interaction involving the support, thus displaying enhanced stability, with 100% CO conversion at 250 °C and no obviously decrease in stability test Although more active sites can be provided with smaller active metals, catalysts with small sized particles deactivate faster and to a larger extent than catalysts with medium sized particles. Thus, the smaller the particle size of the active component, the worse the stability.

The valorisation of CO2 through its capture and in-situ hydrogenation to methane, using dual function materials (DFMs), emerges as promising alternative to reduce CO2 emissions to atmosphere and the global cost of current CO2 Capture and Utilization (CCU) technology. This work investigates the viability of LaNiO3-derived formulations as precursors of DFMs for CO2 capture and in-situ conversion to CH4. For this purpose, a set of DFMs obtained from 30% LaNiO3/CeO2, 30% LaNiO3/Al2O3, 30% LaNiO3/La-Al2O3 and LaNiO3 precursors were synthesized and systematically characterized before and after a controlled reduction process. Results of XRD analysis, STEM-EDX images, H-2-TPR and CO2-TPD experiments reveal that the DFM obtained after reduction of 30% LaNiO3/CeO2 formulation shows the smallest Ni-0 particle size (7 nm) and the highest medium-strong basic sites concentration. In fact, this DFM widens operation window with methane production ranging between 80 and 103 mu mol g(-1) and maintains a selectivity towards methane above 90% in the range of 280-520 degrees C. The best catalytic behaviour is related to a better contact between the different nature basic sites and the homogenously distributed Ni-0 sites, which favours a fast spill-over of dissociated H to near CO2 adsorption sites. The applicability of this formulation is further evidenced by a highly stable CH4 production during long-term experiments and a promoted Ni-0/NiO reversibility in the absence/presence of O-2 during the CO2 adsorption period, which allows a fast and complete recovery of CH4 production in absence of O-2. These aspects favour a versatile application of the 30% LaNiO3/CeO2-based DFM formulation to convert CO2 outlet streams from combustion flue gases of different nature. Support for this study was provided by the Spanish Ministry of Science and Innovation (Project PID2019-105960RB-C21) and the Basque Government (Project IT1297-19). One of the authors (JAOC) acknowledges the Post-doctoral research grant (DOCREC20/49) provided by the University of the Basque Country (UPV/EHU).

Chemical CO2 recycling in the gas phase constitutes a straightforward approach for effective CO2 conversion to added-value products like syngas or synthetic methane. In this scenario, some traditional processes such as the dry and bi-reforming of methane, the CO2 methanation and the reverse water-gas shift have gained a renewed interest from the CO2 utilisation perspective. Indeed, these reactions represent flexible routes to upgrade CO2 and their application at an industrial scale could substantially reduce CO2 emissions. The bottleneck for the implementation of these processes at the commercial level is the development of highly active and robust heterogeneous catalysts able to overcome CO2 activation and deliver sufficient amounts of the upgrading products (i.e. syngas or synthetic natural gas) at the desired operating conditions. This review paper gathers the most recent advances in the design of new catalytic formulations for chemical CO2 recycling in the gas phase and constitutes an overview for experts and newcomers in the field to get fundamental insights into this emerging branch of low-carbon technologies. Ministerio de Ciencia, Innovación y Universidades RTI2018-096294-B-C33, PID2019-108502RJ-I00, IJC2019- 040560-I, RYC2018-024387-I Junta de Andalucía US-1263288, P20-00667 European Union (UE).H2020 101008058

Ex-situ biomethanation (CO2 + 4H2 → CH4 + 2H2O) can simultaneously achieve renewable electricity storage and CO2 valorisation. However, fluctuations in variable renewable electricity may lead to intermittent hydrogen supply, which is shown to adversely affect microbial activity and performance of the biomethanation process. Carbonaceous materials may act as an abiotic additive to enhance microbial robustness and improve system performance. Nanomaterial graphene and pyrochar were compared to assess their effects on biomethanation systems with an intermittent supply of hydrogen. Results revealed that intermittent gas supply caused deterioration in the restart performance with only 66% of theoretical methane production obtained in the control compared with 84% under steady state conditions. The addition of graphene in biomethanation led to 78% of the theoretical methane production after repetitive intermittent supply; this improvement is postulated to be due to its high electrical conductivity and large specific surface (500 m2/g). In comparison, pyrochar amendment did not lead to a significant improvement in upgrading performance. Microbial analysis showed that the OTUs affiliated to bacteria withinin the order SHA-98 (42.9% in abundance) and archaea from the genus Methanothermobacter (99%) may result in the establishment of a new syntrophic relationship to improve the robustness of biomethanation process.

The direct conversion of carbon dioxide (CO2) using green hydrogen is a sustainable approach to jet fuel production. However, achieving a high level of performance remains a formidable challenge due to the inertness of CO2 and its low activity for subsequent C–C bond formation. In this study, we prepared a Na-modified CoFe alloy catalyst using layered double-hydroxide precursors that directly transforms CO2 to a jet fuel composed of C8–C16 jet-fuel-range hydrocarbons with very high selectivity. At a temperature of 240°C and pressure of 3 MPa, the catalyst achieves an unprecedentedly high C8–C16 selectivity of 63.5% with 10.2% CO2 conversion and a low combined selectivity of less than 22% toward undesired CO and CH4. Spectroscopic and computational studies show that the promotion of the coupling reaction between the carbon species and inhibition of the undesired CO2 methanation occur mainly due to the utilization of the CoFe alloy structure and addition of the Na promoter. This study provides a viable technique for the highly selective synthesis of eco-friendly and carbon-neutral jet fuel from CO2., Graphical abstract, Public summary • An alloy is developed for the direct CO2 hydrogenation to jet-fuel-range hydrocarbons • The selectivity of the hydrocarbons (63.5%) exceeds the theoretical maximum value • The CoFe alloy is the active phase in the coupling reaction between surface carbons • The CoFe alloy is a highly efficient catalyst in the presence of a sodium promoter

The conversion of CO2 towards added valuable products is considered as a potential alternative to achieve the increase of the petrochemical industry while reducing the CO2 emissions. In the present work, the effect of Ru loading on CeO2 supports has been studied for the CO2 methanation reaction, and catalysts with different Ru loading in the 1–5 wt. % range have been prepared, characterized, and tested. The optimum Ru loading has been found to be 2.5 wt. %. Ruthenium cations are reduced at the lowest temperature for this optimum loading according to H2-TPR experiments (even at room temperature), and the highest proportion of ruthenium cations with strong interaction with ceria is achieved, as deduced from XPS. XRD characterization suggests partial insertion of ruthenium cations into the ceria lattice. In situ DRIFTS experiments evidenced that the balance between formation upon CO2 chemisorption and further hydrogenation of surface carbon intermediates is optimum for 2.5 wt. % Ru/CeO2. For low metal contents, the CO2 chemisorption is limited and no relevant, while as the metal content is increased, the hydrogenation of carbon species is less favourable. The 2.5 wt.% Ru/CeO2 catalyst comprises a balance between surface-carbon groups formation and further hydrogenation. Generalitat Valenciana (PROMETEO/2018/0765); MICINN (PID2019-105960RB-C22); Junta de Andalucía (Project P18-RTJ-2974); European Union's Horizon 2020 research and innovation program (Marie Skłodowska-Curie grant agreement No 713567); Science Foundation Ireland Research Centre (award 12/RC/2278_P2).

Carbon dioxide emission to the atmosphere is worsened as all the industries emit greenhouse gases (GHGs) to the atmosphere, particularly from refinery industries. The catalytic chemical conversion through methanation reaction is the most promising technology to convert this harmful CO2 gas to wealth CH4 gas for the combustion. Thus, supported neodymium oxide based catalyst doped with manganese and ruthenium was prepared via wet impregnation route. The screening was initiated with a series of Nd/Al2O3 catalysts calcined at 400 °C followed by optimization with respect to calcination temperatures, based ratios loading and various Ru loading. The Ru/Mn/Nd (5:20:75)/Al2O3 calcined at 1000 °C was the potential catalyst, attaining a complete CO2 conversion and forming 40% of CH4 at 400 °C reaction temperature. XRD results revealed an amorphous phase with the occurrence of active species of RuO2, MnO2, and Nd2O3, and the mass ratio of Mn was the highest among other active species as confirmed by EDX. The ESR resulted in the paramagnetic of Nd3+ at the g value of 2.348. Meanwhile nitrogen adsorption (NA) analysis showed the Type IV isotherm which exhibited the mesoporous structure with H3 hysteresis of slit shape pores. Keywords: Neodymium oxide, Methanation, Carbon dioxide, Natural gas, Greenhouse gases

Summary Renewable CO2 electrosynthesis is a potentially promising tool to utilize unwanted greenhouse gas. The greatest barrier to its adoption is rendering the production of CO2-derived chemicals cost-competitive, such that they have higher net value than their fossil-derived equivalents. Among the commodities that have been made using CO2, H2O, and electricity, CH4 is one of the simplest and most researched products. Technoeconomic studies of CO2 methanation make it clear that its high-value applications are limited without significant subsidy on Earth, where it competes with low-cost natural gas. In space, however, CO2 methanation via the Sabatier reaction is already used on the International Space Station to recycle atomic oxygen, and propulsion systems employing cryogenic liquid methane are in development for reusable rocket engines. Comparative analysis of power-to-gas using either CO2 electrosynthesis or the Sabatier reaction from an aerospace perspective identifies research priorities and parameters for deployment. Given its atmospheric CO2 concentration over 95%, Mars may present future opportunities for technology that could also help overcome our climate challenges on Earth., Graphical abstract, Highlights • Carbon dioxide conversion is useful for space exploration today and in the future • Reusable rocket engines can use methane made from carbon dioxide as fuel • This is useful on Mars, where the atmosphere is >95% carbon dioxide • Compact systems that produce fuel from carbon dioxide are demonstrated, Chemical Engineering; Process Engineering; Electrochemistry; Space Sciences; Engineering

Journal of catalysis 400, 407 - 420 (2021). doi:10.1016/j.jcat.2021.06.028, Discrimination between electronic and structural effects in metal-support interactions (MSIs) is often hampered by contributions from either one. We report results of a combined experimental/theoretical study that directly demonstrate the action of electronic MSIs (EMSIs), while structural modifications like a partial overgrowth of metal nanoparticles by a partly reduced oxide due to SMSI, can be excluded. This is demonstrated for CO2 methanation on Ru/ZrO2 with small Ru NPs (~2nm), where a high-temperature reductive treatment results in a significantly increased methanation rate. Based on operando / in situ spectroscopies and other characterizations, SMSI induced structural modifications can be excluded; the enhanced activity results from charge transfer from O-vacancies in the ZrOx surface region to adjacent Ru nanoparticles. DFT calculations reveal that the transferred charge is localized at the interface, leading to stronger Ru-CO bonding and enhanced COad methanation. We believe that these trends are generally relevant for reactions in a reductive atmosphere., Published by Elsevier, Amsterdam [u.a.]

Through electrolysis and methanation coupling, Power to Methane systems have raised as an attractive alternative for power generation while harnessing renewable sources’ potential and reducing carbon dioxide (CO2) emissions. However, there is a research scarcity in their coupling within a Power to Methane context. This study simulates and analyzes an alkaline electrolysis cell coupled to a methanation process in a Power to Methane context to produce electricity by an open Brayton cycle in both steady and dynamic state. Simulation software is used to analyze the operating conditions and specifications’ effects, the effect of the electrolysis power input in a steady-state simulation, and the behavior of a dynamic-simulation with fluctuating renewable energy input for the electrolysis process in two different plant arrangements. Results provide a preliminary glance at the Power to Methane system’s behavior finding its contribution to the continuity issues that renewable energy sources have. However, the importance of continuing the research is highlighted to deeply understand the coupling of these processes in order to improve the profitability and performance of a PtM system.

The fundamental process step within the production of SNG from biomass is methane production. In the present work, methanation is considered to be carried out in a series of adiabatic fixed bed reactors with inter-cooling and product recycle. A robust mathematical model for the considered configuration has been developed that would essentially capture the fundamental operations of the methanation process and help to provide optimal guidelines for industrial operations. In detail, several CO/CO2 feed ratio compositions and recycle ratios were analyzed.

Power-to-Gas technologies could play an important role in future energy systems, since they make it possible to store surplus electric energy from fluctuating renewable energy sources such as solar and wind. In Power-to-Gas concepts, the first step towards storage is the production of H2 by electrolysis, a possible further step is methanation. The Engler-Bunte-Institute, Fuel Technology at Karlsruhe Institute of Technology is conducting research on catalytic methanation in slurry bubble column reactors, which represent a highly load flexible reactor technology. To obtain experimental data at a semi-industrial scale a methanation pilot plant was built and commissioned. The plant is equipped with various safety valves, which may release the hazardous gases H2, CO and CH4 in the chemical reactor into the environment in the unintended case of overpressure, which may lead to a flammable and/or toxic cloud, threatening the safety of the workers and other humans near the plant. In this work, the safety evaluation of the accidental release in the methanation plant is performed using the numerical tool GASFLOW-MPI. Both toxicity and flammability of the hazardous gas cloud are analyzed and discussed. A local-global two-step simulation strategy, including a local computational model and a global computational model, is employed to calculate the hazardous gas dispersion efficiently and accurately. In the first step, a local detailed computational model with fine mesh is used to calculate the release mass flow through the exhaust tube and the complicated shock waves directly without any further assumption model such as the notional nozzle model. In the second step, a large-scale model with the relatively coarse mesh is chosen to efficiently predict the hazardous gas dispersion around the entire methanation plant. Moreover, the performances of two different types of exhaust pipes are compared and discussed, and the recommended exhaust pipe design is provided. The simulation results show that version B of the exhaust tubes is more recommendable from the viewpoint of safety.

The design of fixed-bed reactors has gained interest in the light of load-flexible operation. This is due to the expectation that some process feeds will be more volatile in the near future, for example, within the framework of the power-to-methane concept. In this regard, the application of an inert shell onto the catalyst particles has proven advantageous. In this work, a multi-period design optimization of a fixed-bed methanation reactor is performed by employing a heterogeneous reactor model, in which the catalyst particle is divided into an active core and an inert shell. Due to the model's computational demand, it is reduced by using stoichiometric relations at the reactor and catalyst particle scale. Subsequently, dynamic transition simulations between the optimized steady states coming from the multi-period design optimization as well as a reactor start-up and shut-down simulation are carried out, and the results of the full model are compared to those of the reduced model. Our results show that the model size can be reduced significantly by using the stoichiometric relations without loss of accuracy in steady state and negligible accuracy loss in transient scenarios. The optimized fixed-bed methanation reactor can be operated over a wide load range by optimally adjusting the operating variables and the dynamic simulations show smooth transitions between the steady states.

The objective of this work is the detailed analysis of the performance of an advanced packed-bed reactor with evaporation cooling structure and 1.5 (STP) m3 h−1 reactant throughput. Application of pressurized water as the cooling medium enables stable reactor operation within a safe temperature window at extremely high space-time yield (∼ 1000 m 3 C H 4 /m3reactorh, ∼ 18,000 m 3 C H 4 /m3reaction-volumeh). The performance of the reactor regarding its axial temperature profile and product quality under different process conditions such as water coolant flow rate distribution and pressure in cooling passages is evaluated in detail. The feed throughput and composition influence on reactor performance during start-up, steady-state and transient operational conditions for a technical methanation plant are investigated. For reactor description purposes and computing the heat transfer coefficient, a cascade model of perfectly mixed CSTRs is implemented. The modelling results predict the experimental data very well regarding the temperature profile and product composition.

This chapter of the book is a review of subterranean methanation with an emphasis on Power to Gas technology. The global energy situation and electric system characteristics are analyzed, which shows that it is necessary to develop solutions to better integrate renewable energy into the energy system. Among the different solutions that exist, and as one with the greatest potential is Power to Gas, by transforming electrical energy into hydrogen or methane as energy vectors, able to store energy seasonally and on terawatt-hours (TWh) scale, taking advantage of the storage capacity of the gaseous system. The Sabatier reaction involved in the hydrogen to methane process is usually carried out thermo-chemically in catalytic reactors or biologically in biological reactors.

Among challenges implicit in the transition to the post–fossil fuel energetic model, the finite amount of resources available for the technological implementation of CO2 revalorizing processes arises as a central issue. The development of fully renewable catalytic systems with easier metal recovery strategies would promote the viability and sustainability of synthetic natural gas production circular routes. Taking Ni and NiFe catalysts supported over g-Al2O3 oxide as reference materials, this work evaluates the potentiality of Ni and NiFe supported biochar catalysts for CO2 methanation. The development of competitive biochar catalysts was found dependent on the creation of basic sites on the catalyst surface. Displaying lower Turn Over Frequencies than Ni/Al catalyst, the absence of basic sites achieved over Ni/C catalyst was related to the depleted catalyst performances. For NiFe catalysts, analogous Ni5Fe1 alloys were constituted over both alumina and biochar supports. The highest specific activity of the catalyst series, exhibited by the NiFe/C catalyst, was related to the development of surface basic sites along with weaker NiFe–C interactions, which resulted in increased Ni0:NiO surface populations under reaction conditions. In summary, the present work establishes biochar supports as a competitive material to consider within the future low-carbon energetic panorama.

Tar, a hazardous mixture, produced in biomass gasification can be condensed in the reactor and cause blocking and fouling of engines. Among all the removal technologies, tar removal in the presence of catalyst has been proved to be effective for tar elimination and towards H2-riched syngas production. In recent years, there are many literatures that reported different heterogeneous catalysts in biomass tar reforming, and many catalysts are identified to produce syngas with different compositions. However, further utilization of produced gas (e.g., methanation) is still not well solved, which limited the development of biomass gasification. Hence, in this review, we first reviewed biomass gasification and common methods for produced tar removal. After that, we shed light on the fundamentals (gas clean-up and proportion adjustment) and downstream integration between produced gas from biomass gasification and methanation, etc. Following this, the summary and challenge are concluded to give an insight into the integration between gasification and downstream technologies in the future.