Electrically driven SiC-based structured catalysts for intensified reforming processes

Distributed electrified heating for efficient hydrogen production

This study introduces a distributed electrified heating approach that is able to innovate chemical engineering involving endothermic reactions. It enables rapid and uniform heating of gaseous reactants, facilitating efficient conversion and high product selectivity at specific equilibrium. Demonstrated in catalyst-free CH4 pyrolysis, this approach achieves stable production of H2 (530 g h-1 L reactor -1) and carbon nanotube/fibers through 100% conversion of high-throughput CH4 at 1150 °C, surpassing the results obtained from many complex metal catalysts and high-temperature technologies. Additionally, in catalytic CH4 dry reforming, the distributed electrified heating using metallic monolith with unmodified Ni/MgO catalyst washcoat showcased excellent CH4 and CO2 conversion rates, and syngas production capacity. This innovative heating approach eliminates the need for elongated reactor tubes and external furnaces, promising an energy-concentrated and ultra-compact reactor design significantly smaller than traditional industrial systems, marking a significant advance towards more sustainable and efficient chemical engineering society.

A Review of the CFD Modeling of Hydrogen Production in Catalytic Steam Reforming Reactors

Global demand for alternative renewable energy sources is increasing due to the consumption of fossil fuels and the increase in greenhouse gas emissions. Hydrogen (H₂) from biomass gasification is a green energy segment among the alternative options, as it is environmentally friendly, renewable, and sustainable. Accordingly, researchers focus on conducting experiments and modeling the reforming reactions in conventional and membrane reactors. The construction of computational fluid dynamics (CFD) models is an essential tool used by researchers to study the performance of reforming and membrane reactors for hydrogen production and the effect of operating parameters on the methane stream, improving processes for reforming untreated biogas in a catalyst-fixed bed and membrane reactors. This review article aims to provide a good CFD model overview of recent progress in catalyzing hydrogen production through various reactors, sustainable steam reforming systems, and carbon dioxide utilization. This article discusses some of the issues, challenges, and conceivable arrangements to aid the efficient generation of hydrogen from steam reforming catalytic reactions and membrane reactors of bioproducts and fossil fuels.

Ni-CeO2/SBA-15 Catalyst Prepared by Glycine-Assisted Impregnation Method for Low-Temperature Dry Reforming of Methane

Developing low-temperature nickel-based catalysts with good resistance to coking and sintering for dry reforming of methane (DRM) is of great significance. In this work, Ni (5 wt%) and CeO2 (5 wt%) were supported on SBA-15 porous material by glycine-assisted impregnation method to obtain Ni-CeO2/SBA-15-G catalyst. XRD and TEM results showed that the addition of glycine can effectively promote the dispersion of NiO and CeO2 in the pores of SBA-15. H2-TPR and XPS results confirmed the formation of stronger metal-support interaction. In addition, after the addition of glycine, the NixCe1−xOy solid solution content was increased significantly, meanwhile, the Ce3+ concentration was increased from 31% to 49%, accompanied by more oxygen vacancies and generation of active oxygen species. For the above reasons, Ni-CeO2/SBA-15-G had better catalytic performance in the low-temperature DRM test (20 h, 600 °C) with high GHSV (600,000 mL/gcat/h), its CH4 conversion after reaction of 20 h was 2 times that of Ni-CeO2/SBA-15-C catalyst prepared by a conventional impregnation method. TGA-DTA test also proved that Ni-CeO2/SBA-15-G almost completely eliminated carbon deposition. The above advantages of the Ni-CeO2/SBA-15-G catalyst may have originated from the complexation of glycine with metal cations and can prevent them from gathering.

Electrified Hydrogen Production from Methane for PEM Fuel Cells Feeding: A Review

The greatest challenge of our times is to identify low cost and environmentally friendly alternative energy sources to fossil fuels. From this point of view, the decarbonization of industrial chemical processes is fundamental and the use of hydrogen as an energy vector, usable by fuel cells, is strategic. It is possible to tackle the decarbonization of industrial chemical processes with the electrification of systems. The purpose of this review is to provide an overview of the latest research on the electrification of endothermic industrial chemical processes aimed at the production of H2 from methane and its use for energy production through proton exchange membrane fuel cells (PEMFC). In particular, two main electrification methods are examined, microwave heating (MW) and resistive heating (Joule), aimed at transferring heat directly on the surface of the catalyst. For cases, the catalyst formulation and reactor configuration were analyzed and compared. The key aspects of the use of H2 through PEM were also analyzed, highlighting the most used catalysts and their performance. With the information contained in this review, we want to give scientists and researchers the opportunity to compare, both in terms of reactor and energy efficiency, the different solutions proposed for the electrification of chemical processes available in the recent literature. In particular, through this review it is possible to identify the solutions that allow a possible scale-up of the electrified chemical process, imagining a distributed production of hydrogen and its consequent use with PEMs. As for PEMs, in the review it is possible to find interesting alternative solutions to platinum with the PGM (Platinum Group Metal) free-based catalysts, proposing the use of Fe or Co for PEM application.

Electrified methane steam reforming on a washcoated SiSiC foam for low‐carbon hydrogen production

In view of largely available renewable electricity as a green future resource, here we report the electrification of a Rh/Al₂O₃ washcoated SiSiC foam for methane steam reforming (MSR). We show that, thanks to the suitable bulk resistivity of the SiSiC foam, its direct Joule heating up to relevant temperatures is feasible; the interconnected geometry greatly reduces heat and mass transfer limitations, which results in a highly active and energy efficient system for low-carbon H₂ production. The foam-based electrified MSR (eMSR) system showed almost full methane conversion above 700°C and methane conversions approaching equilibrium were obtained in a range of conditions. Energy efficiency as high as 61% and specific power consumption as low as 2.0 kWh/ N m H 2 3 were measured at 650°C, at gas hourly space velocity (GHSV) of 150,000 cm³/h/g_cat. When driven by renewable electricity, the proposed reactor configuration promises a high potential to address the decarbonization challenge in the near-term future.

Recent Advances in the Development of Highly Conductive Structured Supports for the Intensification of Non-adiabatic Gas-Solid Catalytic Processes: The Methane Steam Reforming Case Study

Structured catalysts are strong candidates for the intensification of non-adiabatic gas-solid catalytic processes thanks to their superior heat and mass transfer properties combined with low pressure drops. In the past two decades, different types of substrates have been proposed, including honeycomb monoliths, open-cell foams and, more recently, periodic open cellular structures produced by additive manufacturing methods. Among others, thermally conductive metallic cellular substrates have been extensively tested in heat-transfer limited exo- or endo-thermic processes in tubular reactors, demonstrating significant potential for process intensification. The catalytic activation of these geometries is critical: on one hand, these structures can be washcoated with a thin layer of catalytic active phase, but the resulting catalyst inventory is limited. More recently, an alternative approach has been proposed, which relies on packing the cavities of the metallic matrix with catalyst pellets. In this paper, an up-to-date overview of the aforementioned topics will be provided. After a brief introduction concerning the concept of structured catalysts based on highly conductive supports, specific attention will be devoted to the most recent advances in their manufacturing and in their catalytic activation. Finally, the application to the methane steam reforming process will be presented as a relevant case study of process intensification. The results from a comparison of three different reactor layouts (i.e. conventional packed bed, washcoated copper foams and packed copper foams) will highlight the benefits for the overall reformer performance resulting from the adoption of highly conductive structured internals.

Mechanistic and multiscale aspects of thermo-catalytic CO2 conversion to C1 products

The increasing environmental concerns due to anthropogenic CO2 emissions have called for an alternate sustainable source to fulfill rising chemical and energy demands and reduce environmental problems. The thermo-catalytic activation and conversion of abundantly available CO2, a thermodynamically stable and kinetically inert molecule, can significantly pave the way to sustainably produce chemicals and fuels and mitigate the additional CO2 load. This can be done through comprehensive knowledge and understanding of catalyst behavior, reaction kinetics, and reactor design. This review aims to catalog and summarize the advances in the experimental and theoretical approaches for CO2 activation and conversion to C1 products via heterogeneous catalytic routes. To this aim, we analyze the current literature works describing experimental analyses (e.g., catalyst characterization and kinetics measurement) as well as computational studies (e.g., microkinetic modeling and first-principles calculations). The catalytic reactions of CO2 activation and conversion reviewed in detail are: (i) reverse water-gas shift (RWGS), (ii) CO2 methanation, (iii) CO2 hydrogenation to methanol, and (iv) dry reforming of methane (DRM). This review is divided into six sections. The first section provides an overview of the energy and environmental problems of our society, in which promising strategies and possible pathways to utilize anthropogenic CO2 are highlighted. In the second section, the discussion follows with the description of materials and mechanisms of the available thermo-catalytic processes for CO2 utilization. In the third section, the process of catalyst deactivation by coking is presented, and possible solutions to the problem are recommended based on experimental and theoretical literature works. In the fourth section, kinetic models are reviewed. In the fifth section, reaction technologies associated with the conversion of CO2 are described, and, finally, in the sixth section, concluding remarks and future directions are provided.

A Numerical Investigation of Electrically-Heated Methane Steam Reforming Over Structured Catalysts

The use of electric energy as an alternative system to provide heat of reaction enables the cut-off of CO2 emissions of several chemical processes. Among these, electrification of steam methane reforming results in a cleaner production method of hydrogen. In this work, we perform for the first time a numerical investigation of a compact steam reforming unit that exploits the electrical heating of the catalyst support. First, for such unit we consider the optimal thermodynamic conditions to perform the power to hydrogen conversion; the process should be run at atmospheric pressure and in a close temperature range. Then, among possible materials currently used for manufacturing structured supports we identify silicon carbide as the best material to run electrified steam reforming at moderate voltages and currents. The temperature and concentration profiles in idealized units are studied to understand the impact of the catalyst geometry on the process performances and open-cell foams, despite lower surface to volume show the best potential. Finally, the impact of heat losses is analyzed by considering different operative conditions and reactor geometries, showing that it is possible to obtain relatively high thermal efficiencies with the proposed methodology.

Main Hydrogen Production Processes: An Overview

Due to its characteristics, hydrogen is considered the energy carrier of the future. Its use as a fuel generates reduced pollution, as if burned it almost exclusively produces water vapor. Hydrogen can be produced from numerous sources, both of fossil and renewable origin, and with as many production processes, which can use renewable or non-renewable energy sources. To achieve carbon neutrality, the sources must necessarily be renewable, and the production processes themselves must use renewable energy sources. In this review article the main characteristics of the most used hydrogen production methods are summarized, mainly focusing on renewable feedstocks, furthermore a series of relevant articles published in the last year, are reviewed. The production methods are grouped according to the type of energy they use; and at the end of each section the strengths and limitations of the processes are highlighted. The conclusions compare the main characteristics of the production processes studied and contextualize their possible use.