The Role of Strontium in CeNiO3 Nano-Crystalline Perovskites for Greenhouse Gas Mitigation to Produce Syngas

The transition metal-based catalysts for the elimination of greenhouse gases via methane reforming using carbon dioxide are directly or indirectly associated with their distinguishing characteristics such as well-dispersed metal nanoparticles, a higher number of reducible species, suitable metal–support interaction, and high specific surface area. This work presents the insight into catalytic performance as well as catalyst stability of Ce_xSr_1−xNiO₃ (x = 0.6–1) nanocrystalline perovskites for the production of hydrogen via methane reforming using carbon dioxide. Strontium incorporation enhances specific surface area, the number of reducible species, and nickel dispersion. The catalytic performance results show that CeNiO₃ demonstrated higher initial CH₄ (54.3%) and CO₂ (64.8%) conversions, which dropped down to 13.1 and 19.2% (CH₄ conversions) and 26.3 and 32.5% (CO₂ conversions) for Ce_0.8Sr_0.2NiO₃ and Ce_0.6Sr_0.4NiO₃, respectively. This drop in catalytic conversions post strontium addition is concomitant with strontium carbonate covering nickel active sites. Moreover, from the durability results, it is obvious that CeNiO₃ exhibited deactivation, whereas no deactivation was observed for Ce_0.8Sr_0.2NiO₃ and Ce_0.6Sr_0.4NiO₃. Carbon deposition during the reaction is mainly responsible for catalyst deactivation, and this is further established by characterizing spent catalysts.

Development of Reaction Kinetics Model for the Production of Synthesis Gas from Dry Methane Reforming

The energy supply systems dependent on fossils and municipal solid waste (MSW) materials are primarily responsible for releasing greenhouse (GHG) gases and their related environmental hazards. The increasing amount of methane (CH4) and carbon dioxide (CO2) is the scientific community's main concern in this context. Reduction in the emission amount of both gases combined with the conversion technologies that would convert these total threat gases (CO2 and CH4) into valuable feedstocks will significantly lower their hazardous impact on climate change. The conversion technique known as dry methane reforming (DMR) utilizes CO2 and CH4 to produce a combustible gas mixture (CO+H2), popularly known as synthesis gas/or syngas. Therefore, this research study aims to explore and enlighten the characteristics of the DMR mechanism. The conversion behaviour of CO2 and CH4 was studied with modelling and simulation of the DMR process using MATLAB. The results showed that inlet gas flow has a significant impact on the reactions. In contrast, the inlet molar composition ratio of the reactions was found to have no substantial effect on the mechanism of DMR. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

State-of-the-art in methane-reforming reactor modeling: challenges and new insights

The reforming of methane is an important industrial process, and reactor modeling and simulation is frequently employed as a design and analysis tool in understanding this process. While much research work is devoted to catalyst formulations, reaction mechanisms, and reactor designs, this review aims to summarize the literature concerning the simulation of methane reforming. Applications in industrial practice are highlighted, and the three main approaches to representing the reactions are briefly discussed. An overview of simulation studies focusing on methane reforming is presented. The three central methods for fixed-bed reactor modeling are discussed. Various approaches and modern examples are discussed, presenting their modeling methods and key findings. The overall objective of this paper is to provide a dedicated review of simulation work done for methane reforming and provide a reference for understanding this field and identifying possible new paths.

Single-Step Flame Aerosol Synthesis of Active and Stable Nanocatalysts for the Dry Reforming of Methane

We introduce a flame-based aerosol process for producing supported non-noble metal nanocatalysts from inexpensive aqueous metal salt solutions, using catalysts for the dry reforming of methane (DRM) as a prototype. A flame-synthesized nickel-doped magnesia (MgO) nanocatalyst (NiMgO-F) was fully physicochemically characterized and tested in a flow reactor system, where it showed stable DRM activity from 500 to 800 °C. A kinetic study was conducted, and apparent activation energies were extracted for the temperature range of 500-650 °C. It was then compared with a Ni-decorated MgO nanopowder prepared by wet impregnation of (1) flame-synthesized MgO (NiMgO-FI) and (2) a commercial MgO nanopowder (NiMgO-CI) and with (3) a NiMgO catalyst prepared by co-precipitation (NiMgO-CP). NiMgO-F showed the highest catalytic activity per mass and per metallic surface area and was stable for continuous H₂ production at 700 °C for 50 h. Incorporation of potential promoters and co-catalysts was also demonstrated, but none showed significant performance improvement. More broadly, nanomaterials produced by this approach could be used as binary or multicomponent catalysts for numerous catalytic processes.

Dry reforming of methane over nickel supported on Nd-ceria: enhancement of the catalytic properties and coke resistance

Nickel (5 wt%) supported on Nd-doped ceria was studied as catalysts in the DRM reaction at stoichiometric conditions in the range of 600–800 °C. Ce_1−xNd_xO_2−δ supports with different Nd contents (x = 0, 0.05, 0.1 and 0.2) were successfully synthesized. The role of oxygen vacancies by the incorporation of Nd³⁺ into the ceria lattice was investigated. These species were quantified by XRD and Raman spectroscopy, showing a linear dependence as a function of Nd content. Ni/Nd–ceria catalysts were prepared by wet impregnation. Although formation of oxygen vacancies, as well as microstructural features of the support (smaller crystallite sizes, higher surface area, and developed mesoporous structure) were improved as a function of the Nd content, no significant differences were observed in the catalytic properties of Ni/Nd–ceria in the DRM reaction. Despite this, compared to undoped ceria, all the Nd-doped CeO₂ catalysts present an enhanced activity and stability, and the best catalytic performance was observed in the Ni/Ce_0.95Nd_0.05O_2−δ sample. Quantification of carbon residues in spent catalysts showed, as expected, lower amounts in the Ni/Nd–ceria samples; nevertheless, among them, the catalyst with the higher amount of oxygen vacancies, is the one with the higher carbon residues. Incorporation of Nd in ceria changes the acid/base properties, diminishing the gasification capacity of the carbonaceous species. These results emphasize that the activity and stability in the Ni/Nd–ceria catalysts for the DRM reaction depend on two key factors, the redox and the acid/base properties of the CeO₂ supports, offering insights about the necessary and adequate balance between these properties.

The Nd-doped CeO₂ support enhances the reactivity of the catalysts, selectivity toward hydrogen and stability by improving coke deposition resistance.