Loukia Pantzechroula Merkouri

The feasibility of a Dual Function Material (DFM) with a versatile catalyst offering switchable chemical synthesis from carbon dioxide (CO2), was demonstrated for the first time, showing evidence of the ability of these DFMs to passively capture CO2 directly from the air as well. These DFMs open up possibilities in flexible chemical production from dilute sources of CO2, through a combination of CO2 adsorption and subsequent chemical transformation (methanation, reverse water gas shift or dry reforming of methane). Combinations of Ni Ru bimetallic catalyst with Na2O, K2O or CaO adsorbent were supported on CeO2 – Al2O3 to develop flexible DFMs. The designed multicomponent materials were shown to reversibly adsorb CO2 between the 350 and 650oC temperature range and were easily regenerated by an inert gas purge stream. The components of the flexible DFMs showed a high degree of interaction with each other, which evidently enhanced their CO2 capture performance ranging from 0.14 to 0.49 mol/kg. It was shown that captured CO2 could be converted into useful products through either CO2 methanation, reverse water-gas shift (RWGS) or dry reforming of methane (DRM), which provides flexibility in terms of co-reactant (hydrogen vs methane) and end product (synthetic natural gas, syngas or CO) by adjusting reaction conditions. The best DFM was the one containing CaO, producing 104 μmol of CH4/kgDFM in CO2 methanation, 58 μmol of CO/kgDFM in RWGS and 338 μmol of CO/kgDFM in DRM. 

Advanced catalytic materials able to catalyse more than one reaction efficiently are needed within the CO2 utilisation schemes to benefit from end-products flexibility. In this study, the combination of Ni and Ru (15 and 1 wt%, respectively) was tested in three reactions, i.e. dry reforming of methane (DRM), reverse water-gas shift (RWGS) and CO2 methanation. A stability experiment with one cycle of CO2 methanation-RWGS-DRM was carried out. Outstanding stability was revealed for the CO2 hydrogenation reactions and as regards the DRM, coke formation started after 10 h on stream. Overall, this research showcases that a multicomponent Ni-Ru/CeO2 -Al2O3 catalyst is an unprecedent versatile system for gas phase CO2 recycling. Beyond its excellent performance, our switchable catalyst allows a fine control of end-products selectivity.

The use of fossil fuels is primarily responsible for the increasing amounts of greenhouse gas emissions in the atmosphere and, unless this issue is quickly addressed, the effects of global warming will worsen. Synthesis gas (syngas) is an attractive target chemical for carbon capture and utilisation and dry reforming of methane (DRM) enables the conversion of methane (CH4) and CO2, the two most abundant greenhouse gases, to syngas. This paper presents a techno-economic analysis of a syngas-to-dimethyl ether (DME) process, by utilising landfill gas as feedstock. The process developed herein produces DME, methanol and high-pressure steam as products, resulting in an annual income of €3.49 m and annual operating expenses of €1.012 m. Operating profit was calculated to be €2.317 m per year and the net present value (NPV) was €11.70 m at the end of the project’s 20-year lifespan with a profitability index of 0.83€/€. The process was expected to have a payback time of approximately 10 years and an internal rate of return of 12.47%. A key aspect of this process was CO2 utilisation, which consumed 196,387 tonnes of CO2 annually. The techno-economic analysis conducted in this paper illustrates that greenhouse gas utilisation processes are currently feasible both in terms of CO2 consumption and profitability.

CO2 emissions in the atmosphere have been increasing rapidly in recent years, causing global warming. CO2 methanation reaction is deemed to be a way to combat these emissions by converting CO2 into synthetic natural gas, i.e., CH4. NiRu/CeAl and NiRu/CeZr both demonstrated favourable activity for CO2 methanation, with NiRu/CeAl approaching equilibrium conversion at 350 °C with 100% CH4 selectivity. Its stability under high space velocity (400 L·g−1·h−1) was also commendable. By adding an adsorbent, potassium, the CO2 adsorption capability of NiRu/CeAl was boosted, allowing it to function as a dual-function material (DFM) for integrated CO2 capture and utilisation, producing 0.264 mol of CH4/kg of sample from captured CO2. Furthermore, time-resolved operando DRIFTS-MS measurements were performed to gain insights into the process mechanism. The obtained results demonstrate that CO2 was captured on basic sites and was also dissociated on metallic sites in such a way that during the reduction step, methane was produced by two different pathways. This study reveals that by adding an adsorbent to the formulation of an effective NiRu methanation catalyst, advanced dual-function materials can be designed.

Innovating technologies to efficiently reduce carbon dioxide (CO2) emission or covert it into useful products has never been more crucial in light of the urgent need to transition to a net-zero economy by 2050. The design of efficient catalysts that can make the above a viable solution is of essence. Many noble metal catalysts already display high activity, but are usually expensive. Thus alternative methods for their production are necessary to ensure more efficient use of noble metals. Exsolution has been shown to be an approach to produce strained nanoparticles, stable against agglomeration while displaying enhanced activity. Here we explore the effect of a low level of substitution of Ni into a Rh based A-site deficient titanate aiming to investigate the formation of more efficient, low loading noble metal catalysts. We show that this design principle not only fulfils a major research need in the conversion of CO2 but also provides a step-change advancement in the design and synthesis of tandem catalysts by the formation of distinct catalytically active sites.    

Carbon dioxide (CO2) is one of the most harmful greenhouse gases and it is the main contributor to climate change. Its emissions have been constantly increasing over the years due to anthropogenic activities. Therefore, efforts are being made to mitigate emissions through carbon capture and storage (CCS). An alternative solution is to close the carbon cycle by utilising the carbon in CO2 as a building block for chemicals synthesis in a CO2 recycling approach that is called carbon capture and utilisation (CCU). Dual Function Materials (DFMs) are combinations of adsorbent and catalyst capable of both capturing CO2 and converting it to fuels and chemicals, in the same reactor with the help of a co-reactant. This innovative strategy has attracted attention in the past few years given its potential to lead to more efficient synthesis through the direct conversion of adsorbed CO2. DFM applications for both post combustion CCU and direct air capture (DAC) and utilisation have been demonstrated to date. In this review, we present the unique role DFMs can play in a net zero future by first providing background on types of CCU methods of varying technological maturity. Then, we present the developed applications of DFMs such as the synthesis of methane and syngas. To better guide future research efforts, we place an emphasis on the connection between DFM physiochemical properties and performance. Lastly, we discuss the challenges and opportunities of DFM development and recommend research directions for taking advantage of their unique advantages in a low-carbon circular economy.