The review focuses on presenting recent findings on CO2 methanation plasma-catalytic process. In order to understand the background of the research, firstly a summary of thermal catalytic CO2 ...methanation is presented. Secondly, discussion on plasma CO2 hydrogenation including various plasma types and process parameters is addressed. Catalytic CO2 methanation is already an industrial process achieving high conversions of CO2 and CH4 yield. However, the need to optimize this process (decrease reaction temperature, increase catalyst activity, selectivity and stability) resulted in the development of plasma technology. It was proven that plasma can actively convert CO2. The main product of plasma CO2 hydrogenation is, however, carbon monoxide. Therefore, a plasma process is not selective for CH4 production and the presence of a catalyst is necessary to effectively convert CO2 to CH4 under plasma conditions. The study of plasma-catalytic CO2 methanation is quite a new topic focused mainly on the application of dielectric barrier discharge plasma and Ni-based catalyst. This review summarizes recent advantages of the plasma catalytic process and discusses possible directions of catalyst development.
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•Plasma-catalytic CO2 methanation may become an important technology for H2 storage and CO2 valorisation.•CO2 activation in plasma requires catalyst to produce CH4.•Catalyst for plasma process should be active in thermal catalysis.•Beneficial effect of plasma-catalysis may be enhanced via adjustment of catalyst properties and plasma operating conditions.
Zeolite H-USY doped with nickel (14% wt.) was used as a catalyst in the plasma-assisted CO
2
hydrogenation under partial vacuum. CO was found to be the main product of the reaction and it is ...generated by plasma-assisted CO
2
dissociation in the gas phase. The CO
2
molecules vibrationally excited by plasma are also adsorbed on metallic nickel as formates which are further transformed into linear carbonyls. These species are then hydrogenated to form methane. Since the catalyst presents a low basic behavior, methane is produced from hydrogenation of linear carbonyls on nickel surface rather than from carbonates species. A detailed mechanism for this reaction assisted by plasma (glow discharge) is proposed using Operando time-resolved FTIR spectroscopic data.
The 2020 plasma catalysis roadmap Bogaerts, Annemie; Tu, Xin; Whitehead, J Christopher ...
Journal of physics. D, Applied physics,
10/2020, Letnik:
53, Številka:
44
Journal Article
Recenzirano
Odprti dostop
Plasma catalysis is gaining increasing interest for various gas conversion applications, such as CO2 conversion into value-added chemicals and fuels, CH4 activation into hydrogen, higher hydrocarbons ...or oxygenates, and NH3 synthesis. Other applications are already more established, such as for air pollution control, e.g. volatile organic compound remediation, particulate matter and NOx removal. In addition, plasma is also very promising for catalyst synthesis and treatment. Plasma catalysis clearly has benefits over 'conventional' catalysis, as outlined in the Introduction. However, a better insight into the underlying physical and chemical processes is crucial. This can be obtained by experiments applying diagnostics, studying both the chemical processes at the catalyst surface and the physicochemical mechanisms of plasma-catalyst interactions, as well as by computer modeling. The key challenge is to design cost-effective, highly active and stable catalysts tailored to the plasma environment. Therefore, insight from thermal catalysis as well as electro- and photocatalysis is crucial. All these aspects are covered in this Roadmap paper, written by specialists in their field, presenting the state-of-the-art, the current and future challenges, as well as the advances in science and technology needed to meet these challenges.
Ethylene is a plant growth regulator that induces accelerated softening and ripening of fruits during transport and storage. Among the most applied methods for ethylene control, adsorption appears as ...a cheap and efficient technique. In this work, the effect of the incorporation of transition metals into natural Chilean zeolite on ethylene adsorption is investigated. Natural zeolite mainly composed of clinoptilotite and mordenite is modified using copper and zinc nitrate solutions and calcined under oxygen flow at 623 K, generating different transition metal modified zeolites. Parent and modified zeolites were characterised by X-ray diffraction, X-ray fluorescence spectroscopy and nitrogen adsorption. Zeolite surface modifications were assessed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Experimental results reveal the incorporation of Cu2+ and Zn2+ as new compensating cations into the zeolite framework. Ethylene adsorption isotherms show an enhancement on the adsorption capacity of Cu-exchanged zeolite. This result is not only associated to the higher micropore surface area of this sample, but also to the higher affinity of ethylene molecules to copper cations incorporated on this zeolite. DRIFTS operando experiments of ethylene adsorption in the absence and in the presence of moisture reveal a competitive mechanism of water and ethylene molecules toward hydroxyl sites. Si-OH-Al and Si-OH sites are rapidly occupied with water, reducing the adsorption of ethylene.
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•Copper doped natural zeolite increases the adsorption capacity towards ethylene.•Ethylene and water molecules compete for similar active adsorption sites.•Adsorption interactions are identified by DRIFTS analyses.
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•Effect of Al2O3, SiO2 and CeO2-ZrO2 support on the performance of Ni catalyst was investigated.•Properties of support influence plasma properties and thus CO2 dissociation in a gas ...phase.•Exposure to plasma modified surface of materials influencing their catalytic properties.•CH4 production after plasma extinction was observed.•Differences between samples in surface reaction mechanisms were established.
Low-pressure, glow discharge plasma catalytic CO2 methanation was investigated in the presence of Ni/Al2O3, Ni/SiO2 and Ni/CeO2-ZrO2 catalyst. The prepared samples were characterized by ICP, XRD, low-temperature N2 sorption, H2-TPR, dielectric constant measurement and FT-IR in-situ adsorption of NO, CO and CO2. The performed characterization allowed selecting the optimal conditions of catalyst preparation as well as explaining the results of plasma-catalytic tests. The application of various supports had a significant effect on plasma properties and thus dissociation of CO2 in the gas phase. It affected plasma stability as well, which decreased with the increasing values of the dielectric constant. Ni/Al2O3 sample showed the best performance in terms of CH4 production. The positive effect on the catalytic activity in thermal CO2 methanation was observed for Ni/Al2O3 and Ni/SiO2 samples. Adsorption of probe molecules (NO, CO and CO2) performed for fresh reduced and spent catalysts allowed to get insights into plasma-catalytic reaction mechanism and to explain the effect of plasma promotion on the performance of the catalysts in thermal CO2 methanation.
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•Efficient Ni and Ni-Co on alumina catalysts were prepared and characterized.•CO2 methanation process is greener when using our Ni and Ni-Co catalysts.•The addition of cobalt improved ...the reducibility of nickel species.•The addition of cobalt improved activity and selectivity towards CH4.•Ni and Ni-Co catalysts showed high stability over 200 h of continuous reaction.
CO2 methanation is one of the most promising ways to store energy based on the power-to-gas concept. In this study, efficient nickel (Ni) and nickel-cobalt (Ni-Co), supported on alumina catalysts with different amounts of Ni and Co were prepared, characterized and used for CO2 methanation under the atmospheric pressure. The catalysts were prepared in the form of extrudates for catalytic tests. The effect of Ni content and the influence of Co on Ni catalysts were studied in a packed bed methanation reactor at laboratory scale. An optimal Ni-Co content was identified based on CO2 and H2 conversion and CH4 selectivity and yield. The addition of Co improved the reducibility of Ni species and Ni particles’ dispersion over the support. Therefore, the presence of Co enhanced the catalyst activity and selectivity towards CH4. Moreover, it was observed that low reaction temperatures (lower than 350 °C) can be used when lowering the Ni content (i.e. 10% wt.). This major fact is favourable to the reduction of the overall process energy consumption and to the decrease of the catalysts’ deactivation at high temperature (>400 °C), such as the active phase sintering. Finally, the Ni and Ni-Co catalysts prepared in this work for CO2 methanation presented a remarkably high stability over 200 h of continuous reaction.
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•A novel description for ZSM-11 zeolite microwave-assisted synthesis is provided.•The ZSM-11 synthesis time is remarkably reduced down to 3days with microwaves.•The crystallinity of ...ZSM-11 zeolites is considerably improved with microwaves.•A new morphology is observed when microwave irradiation is used.•Energy consumption and synthesis time are considerably reduced.
A novel and complete description for ZSM-11 zeolite microwave-assisted synthesis is provided. The time required for the synthesis of ZSM-11 zeolite was remarkably reduced down to 3–4days instead of 14days under classical conditions, without the use of seed crystals and of any pretreatment step such as aging time. The crystallinity degree of ZSM-11 zeolites synthesized under microwave irradiation is considerably improved (39% higher) with respect to the crystallinity of conventional ZSM-11 zeolites. According to SEM images, the particle sizes of ZSM-11 zeolites synthesized by both methods are identical and a new morphology is observed when microwave irradiation is used. The surface area and microporous volume values for both synthesis methods are similar.
In this work, the synthesis of ZSM-11 zeolite has been successfully intensified by using microwave irradiation. Energy consumption and synthesis time are considerably reduced.
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•Plasma-assisted boehmite dehydration into gamma alumina was addressed by operando IR.•Nickel alumina porous extrudate preparation was optimized and fully ...characterized.•Plasma-assisted CO2 methanation was studied using the optimized extrudate catalysts.•Formulation of efficient Ni-Al2O3 porous extrudates for CO2 methanation is provided.
Homogeneous low pressure cold plasma glow discharge was used for both boehmite to gamma alumina transformation as well as for catalytic CO2 conversion into methane.
Novel plasma-assisted boehmite transformation into alumina was successfully achieved at lower temperature (80°C less) and shorter period of time (1h less) than the classical transformation. The final alumina structure properties were improved. The mechanism of the novel plasma-assisted boehmite transformation was addressed. Nickel alumina porous extrudate preparation was optimized and fully characterized. The amounts of binder and nitric acid used during the preparation of extrudates were studied. The concentration of nitric acid presented a major role in the catalytic properties of these catalysts leading to the improvement of the active phase dispersion and reducibility. As a result, methane yield was also improved with support acidity. A simulation study was performed in order to evaluate the influence of the extrudates dimensions on the pressure developed inside the reactor and on the glow discharge stability. It was demonstrated by simulation the need of shaping the nickel alumina catalysts for allowing the generation of a stable plasma discharge through the catalytic bed. Plasma-assisted CO2 hydrogenation under partial vacuum was carried out using the optimized nickel alumina extrudates. Formulation of efficient nickel alumina porous extrudates is provided for plasma or even industrial CO2 methanation reactors.
CO2 methanation is an attractive reaction to convert CO2 into a widespread fuel such as methane, being the combination of catalysts and a dielectric barrier discharge (DBD) plasma responsible for ...synergistic effects on the catalyst’s performances. In this work, a Ru-based zeolite catalyst, 3Ru/CsUSY, was synthesized by incipient wetness impregnation and characterized by TGA, XRD, H2-TPR, N2 sorption and CO2-TPD. Catalysts were tested under thermal and plasma-assisted CO2 methanation conditions using in-situ operando FTIR, with the aim of comparing the mechanism under both types of catalysis. The incorporation of Ru over the CsUSY zeolite used as support induced a decrease of the textural properties and an increase of the basicity and hydrophobicity, while no zeolite structural damage was observed. Under thermal conditions, a maximum CO2 conversion of 72% and CH4 selectivity above 95% were registered. These promising results were ascribed to the presence of small Ru0 nanoparticles over the support (16 nm), catalyst surface hydrophobicity and the presence of medium-strength basic sites in the catalyst. Under plasma-catalytic conditions, barely studied in similar setups in literature, CO2 was found to be excited by the plasma, facilitating its adsorption on the surface of 3Ru/CsUSY in the form of oxidized carbon species such as formates, aldehydes, carbonates, or carbonyls, which are afterwards progressively hydrogenated to methane. Adsorption and surface reaction of key intermediates, namely formate and aldehydic groups, was observed even on the support alone, an occurrence not reported before for thermal catalysis. Overall, similar reaction mechanisms were proposed for both thermal and plasma-catalysis conditions.
Ethylene stimulates ripening and senescence by promoting chlorophyll loss, red pigment synthesis, and softening of tomatoes and diminishes their shelf-life. The aim of this work was to study the ...performance of a novel copper- and zinc-based ethylene scavenger supported by ion-exchange on a naturally occurring zeolite by analyzing its ethylene adsorption capacity and the influence of ethylene scavenging on quality attributes during the postharvest life of tomatoes. The influence of copper- and zinc-modified zeolites on ethylene and carbon dioxide concentrations and postharvest quality of tomatoes was compared with unmodified zeolite. Interactions among ethylene molecules and zeolite surface were studied by diffuse reflectance infrared Fourier transform spectroscopy in operando mode. The percentage of ethylene removal after eight days of storage was 57% and 37% for the modified zeolite and pristine zeolite, respectively. The major ethylene increase appeared at 9.5 days for the modified zeolite treatment. Additionally, modified zeolite delayed carbon dioxide formation by six days. Zeolite modified with copper and zinc cations favors ethylene removal and delays tomato fruit ripening. However, the single use of unmodified zeolite should be reconsidered due to its ripening promoting effects in tomatoes at high moisture storage conditions, as water molecules block active sites for ethylene adsorption.
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