Enhancement of Power-to-Gas via Multi-catalyst Reactors Tailoring Reaction Rate and Heat Exchange

The Sabatier reaction is a key element of power-to-gas development. For this reason, even though the process is known since more than one century, the Sabatier reaction is currently the object of important research efforts towards the development of new catalysts for performance improvement. However, the industrial exploitation of the Sabatier reaction depends on the development of reactors that match the best catalyst with an appropriate heat management. For this reason, this paper develops a methodology for the contemporary optimization of the reactor concept and the catalysts. It is observed that the reactor can be divided into three sections with contrasting requirements. In the first section, the main requirement concerns the reach of the reaction activation conditions. Hence, an adequate match between catalyst and reactor is needed, for example with an appropriate pre-heater. Once the reaction is activated, a reaction hotspot is formed, so that the cooling becomes determining and the main requirement for the catalyst is the resistance to poisoning and sintering. In the last section of the reactor, the low temperature activity of the catalyst is determining, so that a high-performing catalyst is needed. This paper indicates a strategy for the rational design of this catalyst, based on mechanistic evidences

Assessment of global sustainability of bioenergy production in a water-food-energy perspective

One of most demanding problems for decision makers and for process engineers is the design of a proper energy strategy to guarantee clean energy supply. This problem is complex and cannot be assessed considering only the standard efficiency criteria used in the past. The process of energy production needs to be analyzed in its completeness, from seed to consumption. This paper deals with the issue of bioenergy production following a nexus perspective, considering the link among water, food and energy. In particular, an objective function depending on the most important resources required in bioenergy production is defined so that it can be simply optimized. Considering the parameter interrelationship among water, food and land (the so-called water-food-energy nexus) the method gives the instruments to determine, in one single function, the optimal condition with respect to these resources. Two cases of study are analysed, dissimilar regarding the geographical location, environmental resources availability for energy production and food security. Results show how the proposed method is able to describe the present sustainability of bioenergy production in a certain site. Furthermore, it can help to investigate the existence of bottlenecks related to the current situation of the site and, at the same time, it can highlight future opportunities in producing sustainable bioenergy

NaWuReT Colloquium: From PhD Student to Assistant Professor – Early Career Chemical Engineers in Academia

The Nachwuchs Reaktionstechnik (NaWuReT) are early-career scientists from the ProcessNet Division Reaction Engineering. In autumn 2021, they organized an online colloquium with international early-career scientists from the chemical engineering community. Five guests were invited to give a scientific talk and provide insights into their career paths. The guests gave advice and emphasized the main challenges and opportunities during their early careers. Crucial points are networking, guidance, mentoring, as well as funding acquisition and the personal work-life balance

In situ Control of the Adsorption Species in CO2 Hydrogenation: Determination of Intermediates and Byproducts

CO2 hydrogenation over catalysts is a potentially exciting method to produce fuels while closing the CO2 cycle and mitigating global warming. The mechanism of this process has been controversial due to the difficulty in clearly identifying the species present and distinguishing which are reaction intermediates and which are byproducts. We in situ manipulated the independent formation and hydrogenation of each adsorption species produced in CO2 hydrogenation reaction over Ru/Al2O3 using operando diffuse reflectance infrared Fourier transformation spectroscopy (DRIFTS) and executed a novel iterative Gaussian fitting procedure. The adsorption species and their role in the CO2 hydrogenation reaction have been clearly identified. The adsorbed carbon monoxide (CO*) of four reactive structures was the key intermediate of methane (CH4) production. Bicarbonate (HCO3–*), formed on the metal–support interface, appeared to be not only the primary product of CO2 chemisorption but also a reservoir of CO* and consisted of the dominate reaction steps of CO2 methanation from the interface to the metal surface. Bidentate formate (Bi-HCOO–*) formed on Ru under a certain condition, consecutively converting to CO* to merge into the subsequent methanation process. Nonreactive byproducts of the reaction were also identified. The evolution of the surface species revealed the essential steps of the CO2 activation and hydrogenation reactions which were inevitably initiated from HCO3–* to CO* and finally from CO* to CH4

Identifying Reaction Species by Evolutionary Fitting and Kinetic Analysis: An Example of CO2 Hydrogenation in DRIFTS

Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) investigations of molecules at the surface of catalysts exhibit a strong overlap of the adsorption peaks. Therefore, the investigation of the CO2 hydrogenation on a highly active catalyst surface requires a deconvolution of the adsorption spectra to clearly assign the signal to the chemical species. We developed an autonomous and efficient bi-level evolutionary Gaussian fitting (BEGF) procedure with a genetic algorithm at the upper level and a multipeak Gaussian fitting algorithm at the lower level to analyze self-consistently the set of spectra of an entire experiment. We show two examples of the application of BEGF procedure by analyzing the DRIFTS spectral sets of ex situ HCOO–* and CO2 hydrogenation on Ru/Al2O3. The fitting procedure deconvoluted the overlapped peaks and identified the bond vibrations of carbon monoxide, formate, bicarbonate, and carbonate through the developing trends of the peak intensities along the reaction. These revealed the progression of those species over the reaction timeline

Infrared Thermography as an Operando Tool for the Analysis of Catalytic Processes: How to Use it?

Infrared (IR) thermography is a powerful tool to measure temperature with high space and time resolution. A particularly interesting application of this technology is in the field of catalysis, where the method can provide new insights into dynamic surface reactions. This paper presents guidelines for the development of a reactor cell that can aid in the efficient exploitation of infrared thermography for the investigation of catalytic and other surface reactions. Firstly, the necessary properties of the catalytic reactor are described. Secondly, we analyze the requirements towards the catalytic system to be directly observable by IR thermography. This includes the need for a catalyst that provides a sufficiently high heat production (or absorption) rate. To achieve true operando investigation conditions, some dedicated equipment must be developed. Here, we provide the guidelines to assemble a chemical reactor with an IR transmitting window through which the reaction can be studied with the infrared camera along with other best practice tips to achieve results. Furthermore, we present selected examples of catalytic reactions that can be monitored by IR thermography, showing the potential of the technology in revealing transient and steady state chemical phenomena

A techno-economic-environmental analysis of the methanol production from biogas and power-to-X

Methanol is a key ingredient for the chemical industry and for the energy sector. Towards a transition into carbon-neutral future, it would be of great interest to reduce the fossil carbon footprint of the methanol synthesis by investigating alternative routes. A potential way to produce methanol in a sustainable manner is to utilize biogas, which is a carbon-neutral feedstock. However, it is challenging to provide sufficient biogas to large-scale plants. For this reason, we investigate in this paper the possibility of producing methanol in small-scale decentralised plants. We analysed the techno-economic-environmental performance of the downscaling of the standard methanol production via steam reforming and we compared it with the novel synthesis via direct CO2 hydrogenation with green H2. We observed that, with cheap electricity and high methanol value, these processes are both profitable, with a slight advantage for the steam-reforming route. However, the direct CO2 hydrogenation route can be improved by developing tailor-made less costly equipment, thus showing a potential for application in an energy storage context (i.e. with extremely cheap electricity). We also observed that the use of biomethane as feedstock for centralized methanol production shows a similar performance as the localized methanol synthesis, due to the high cost of the raw material. Therefore, we can conclude that, with every technology analysed, the shift towards a biogas-based methanol manufacture results in a more expensive product and that small-scale localized production may play a role in the bio-based methanol supply

Renewable energy storage via CO2 and H-2 conversion to methane and methanol: Assessment for small scale applications

This study analyses the power to methane - and to methanol processes in the view of their efficiency in energy storage. A systematic investigation of the differences on the two production systems is performed. The energy storage potential of CO2 to methanol and methane is assessed in a progressive way, from the ideal case to the actual simulated process. In ideal conditions, where no additional energy is required for the reaction and CO2 is fully converted into products, energy storage is 8% more efficient in methanol than methane. However, the Sabatier reaction can be performed with a lower degree of complexity compared to the CO2 to methanol reaction. For this reason, the methanol production process is analysed in detail. The influence of the process configuration and the energy requirements for the various necessary unit operations is investigated, and an efficiency ranking among the various alternatives is obtained. Single stage, recycle and cascade reactors are compared and assessed in terms of energy requirements for the operation and energy storage in the product. For small scale applications, the cascade reactor is the most suitable process technology, because it does not require additional energy and allows high yield to methanol. With the current technology, we demonstrate that a hybrid process, including both the CO2 hydrogenation to methanol and methane, is the most effective method to achieve a high conversion of renewable energy to carbon-based fuels with a significant fraction of liquid product

Parametric sensitivity in the Sabatier reaction over Ru/Al2O3 - theoretical determination of the minimal requirements for reactor activation

The methanation of carbon dioxide is an option for chemical storage of renewable energy together with greenhouse gas reutilization because it offers a product with a high energy density. The reaction CO2 + 4H(2) CH4 + 2H(2)O is performed on a Ru/Al2O3 catalyst and is strongly exothermal. For this reason, the reactor design must take into account an efficient thermal management system to limit the maximal temperature and guarantee high CO2 conversion. Additionally, the methanation reactor is subject to parameter sensitivity. This phenomenon can generate instability in the operation of a power to gas plant, due to the variability in the hydrogen production rate. Here we present a parametric study of the thermal properties of the reaction and determine the minimal feed temperature for the normal operation of a reactor. The minimal temperature required is determined by several parameters, such as pressure, space velocity and properties of the cooling system. For adiabatic reactors, the required feed temperature is 210 degrees C for a space velocity of 3000 h(-1) and a pressure of 10 bar. The space velocity strongly affects the positioning of the ignition point, causing a large variability of the feed temperature required. At the same time, the optimal working point of the reactor is at the minimal activation temperature. The properties of cooled reactors are elucidated, showing how the interrelationship between cooling and feed temperature makes the management of this class of reactors more challenging. On the base of the modelling results, we propose a reactor configuration that adjusts the thermodynamic limitations and respects the minimal requirements for reaction ignition, allowing a more stable operation and avoiding the functioning at excessive temperature