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

Economy of scale for green hydrogen-derived fuel production in Nepal

Opportunity for future green hydrogen development in Nepal comes with end-use infrastructural challenges. The heavy reliance of industries on fossil fuels (63.4%) despite the abundance of hydroelectricity poses an additional challenge to the green transition of Nepal. The presented work aims to study the possibility of storing and utilizing spilled hydroelectricity due to runoff rivers as a compatible alternative to imported petroleum fuels. This is achieved by converting green hydrogen from water electrolysis and carbon dioxide from carbon capture of hard-to-abate industries into synthetic methane for heating applications via the Sabatier process. An economy-of-scale study was conducted to identify the optimal scale for the reference case (Industries in Makwanpur District Nepal) for establishing the Synthetic Natural Gas (SNG) production industry. The techno-economic assessment was carried out for pilot scale and reference scale production unit individually. Uncertainty and sensitivity analyses were performed to study the project profitability and the sensitivity of the parameters influencing the feasibility of the production plant. The reference scale for the production of Synthetic Natural Gas was determined to be 40 Tons Per Day (TPD), with a total capital investment of around 72.15 Million USD. Electricity was identified as the most sensitive parameter affecting the levelized cost of production (LCOP). The 40 TPD plant was found to be price competitive to LPG when electricity price is subsidized below 3.55 NPR/unit (2.7 c/unit) from 12 NPR/unit (9.2 c/unit). In the case of the 2 TPD plant, for it to be profitable, the price of electricity must be subsidized to well below 2 NPR/kWh. The study concludes that the possibility of SNG production in Nepal is profitable and price-competitive at large scales and at the same time limited by the low round efficiency due to conversion losses. Additionally, it was observed that highly favorable conditions driven by government policies would be required for the pilot-scale SNG project to be feasible.

A Review on Green Hydrogen Valorization by Heterogeneous Catalytic Hydrogenation of Captured CO2 into Value-Added Products

The catalytic hydrogenation of captured CO2 by different industrial processes allows obtaining liquid biofuels and some chemical products that not only present the interest of being obtained from a very low-cost raw material (CO2) that indeed constitutes an environmental pollution problem but also constitute an energy vector, which can facilitate the storage and transport of very diverse renewable energies. Thus, the combined use of green H2 and captured CO2 to obtain chemical products and biofuels has become attractive for different processes such as power-to-liquids (P2L) and power-to-gas (P2G), which use any renewable power to convert carbon dioxide and water into value-added, synthetic renewable E-fuels and renewable platform molecules, also contributing in an important way to CO2 mitigation. In this regard, there has been an extraordinary increase in the study of supported metal catalysts capable of converting CO2 into synthetic natural gas, according to the Sabatier reaction, or in dimethyl ether, as in power-to-gas processes, as well as in liquid hydrocarbons by the Fischer-Tropsch process, and especially in producing methanol by P2L processes. As a result, the current review aims to provide an overall picture of the most recent research, focusing on the last five years, when research in this field has increased dramatically.

Recent Advances in Catalysis for Methanation of CO2 from Biogas

Biogas, with its high carbon dioxide content (30–50 vol%), is an attractive feed for catalytic methanation with green hydrogen, and is suitable for establishing a closed carbon cycle with methane as energy carrier. The most important questions for direct biogas methanation are how the high methane content influences the methanation reaction and overall efficiency on one hand, and to what extent the methanation catalysts can be made more resistant to various sulfur-containing compounds in biogas on the other hand. Ni-based catalysts are the most favored for economic reasons. The interplay of active compounds, supports, and promoters is discussed regarding the potential for improving sulfur resistance. Several strategies are addressed and experimental studies are evaluated, to identify catalysts which might be suitable for these challenges. As several catalyst functionalities must be combined, materials with two active metals and binary oxide support seem to be the best approach to technically applicable solutions. The high methane content in biogas appears to have a measurable impact on equilibrium and therefore CO2 conversion. Depending on the initial CH4/CO2 ratio, this might lead to a product with higher methane content, and, after work-up, to a drop in-option for existing natural gas grids.

Catalysts for Production and Conversion of Syngas

Synthesis gas, or syngas for short, is a mixture of CO, CO2, and H2 [...]

Thermal CO Oxidation and Photocatalytic CO2 Reduction over Bare and M-Al2O3 (M = Co, Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au) Cotton-Like Nanosheets

Aluminum oxide (Al₂O₃) has abundantly been used as a catalyst, and its catalytic activity has been tailored by loading transition metals. Herein, γ-Al₂O₃ nanosheets were prepared by the solvothermal method, and transition metals (M = Co, Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au) were loaded onto the nanosheets. Big data sets of thermal CO oxidation and photocatalytic CO₂ reduction activities were fully examined for the transition metal-loaded Al₂O₃ nanosheets. Their physicochemical properties were examined by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction crystallography, and X-ray photoelectron spectroscopy. It was found that Rh, Pd, Ir, and Pt-loading showed a great enhancement in CO oxidation activity while other metals negated the activity of bare Al₂O₃ nanosheets. Rh-Al₂O₃ showed the lowest CO oxidation onset temperature of 172 °C, 201 °C lower than that of bare γ-Al₂O₃. CO₂ reduction experiments were also performed to show that CO, CH₃OH, and CH₄ were common products. Ag-Al₂O₃ nanosheets showed the highest performances with yields of 237.3 ppm for CO, 36.3 ppm for CH₃OH, and 30.9 ppm for CH₄, 2.2×, 1.2×, and 1.6× enhancements, respectively, compared with those for bare Al₂O₃. Hydrogen production was found to be maximized to 20.7 ppm during CO₂ reduction for Rh-loaded Al₂O₃. The present unique pre-screening test results provided very useful information for the selection of transition metals on Al₂O₃-based energy and environmental catalysts.

Catalyst-loaded micro-encapsulated phase change material for thermal control of exothermic reaction

CO₂ methanation is a promising technology to enable the use of CO₂ as a resource. Thermal control of CO₂ methanation, which is a highly active exothermic reaction, is important to avoid thermal runaway and subsequent degradation of the catalyst. Using the heat storage capacity of a phase change material (PCM) for thermal control of the reaction is a novel passive approach. In this study a novel structure was developed, wherein catalysts were directly loaded onto a micro-encapsulated PCM (MEPCM). The MEPCM was prepared in three steps consisting of a boehmite treatment, precipitation treatment, and heat oxidation treatment, and an impregnation process was adopted to prepare a Ni catalyst. The catalyst-loaded MEPCM did not show any breakage or deformation of the capsule or a decrease in the heat storage capacity after the impregnation treatment. MEPCM demonstrated a higher potential as an alternative catalyst support in CO₂ methanation than the commercially available α-Al₂O₃ particle. In addition, the heat storage capacity of the catalyst-loaded MEPCM suppressed the temperature rise of the catalyst bed at a high heat absorption rate (2.5 MW m⁻³). In conclusion, the catalyst-loaded MEPCM is a high-speed, high-precision thermal control device because of its high-density energy storage and resolution of a spatial gap between the catalyst and cooling devices. This novel concept has the potential to overcome the technical challenges faced by efficiency enhancement of industrial chemical reactions.

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.

Aqueous Miscible Organic LDH Derived Ni-Based Catalysts for Efficient CO2 Methanation

Converting CO2 to methane via catalytic routes is an effective way to control the CO2 content released in the atmosphere while producing value-added fuels and chemicals. In this study, the CO2 methanation performance of highly dispersed Ni-based catalysts derived from aqueous miscible organic layered double hydroxides (AMO-LDHs) was investigated. The activity of the catalyst was found to be largely influenced by the chemical composition of Ni metal precursor and loading. A Ni-based catalyst derived from AMO-Ni3Al1-CO3 LDH exhibited a maximum CO2 conversion of 87.9% and 100% CH4 selectivity ascribed to both the lamellar catalyst structure and the high Ni metal dispersion achieved. Moreover, due to the strong Ni metal–support interactions and abundant oxygen vacancy concentration developed, this catalyst also showed excellent resistance to carbon deposition and metal sintering. In particular, high stability was observed after 19 h in CO2/H2 reaction at 360 °C.