Examinando por Autor "Vizcaíno, Arturo J."

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Hydrogen Production Technologies: From Fossil Fuels toward Renewable Sources. A Mini Review
(ACS, 2021) Megía, Pedro J.; Vizcaíno, Arturo J.; Calles, José A.; Carrero, Alicia
The global economic growth, the increase in the population, and advances in technology lead to an increment in the global primary energy demand. Considering that most of this energy is currently supplied by fossil fuels, a considerable amount of greenhouse gases are emitted, contributing to climate change, which is the reason why the next European Union binding agreement is focused on reducing carbon emissions using hydrogen. This study reviews different technologies for hydrogen production using renewable and non-renewable resources. Furthermore, a comparative analysis is performed on renewablebased technologies to evaluate which technologies are economically and energetically more promising. The results show how biomass-based technologies allow for a similar hydrogen yield compared to those obtained with water-based technologies but with higher energy efficiencies and lower operational costs. More specifically, biomass gasification and steam reforming obtained a proper balance between the studied parameters, with gasification being the technique that allows for higher hydrogen yields, while steam reforming is more energy-efficient. Nevertheless, the application of hydrogen as the energy vector of the future requires both the use of renewable feedstocks with a sustainable energy source. This combination would potentially produce green hydrogen while reducing carbon dioxide emissions, limiting global climate change, and, thus, achieving the so-called hydrogen economy
Hydrogen Production through Oxidative Steam Reforming of Acetic Acid over Ni Catalysts Supported on Ceria-Based Materials
(MDPI, 2022-11-27) Megía, Pedro J.; Morales, Anabel; Vizcaíno, Arturo J.; Calles, José A.; Carrero, Alicia
Oxidative steam reforming allows higher energy efficiency and lowers coke deposition compared to traditional steam reforming. In this work, CeO2-based supports have been prepared with Ni as the active phase, and they were tested in the oxidative steam reforming of acetic acid. The influence of the O2/AcOH molar ratio (0–0.3) has been evaluated over Ni/CeO2. The results stated that by increasing oxygen content in the feeding mixture, acetic acid conversion increases too, with a decrease in coke deposition and hydrogen yield. To have a proper balance between the acetic acid conversion and the hydrogen yield, an O2/AcOH molar ratio of 0.075 was selected to study the catalytic performance of Ni catalysts over different supports: commercial CeO2, a novel mesostructured CeO2, and CeO2-SBA-15. Due to higher Ni dispersion over the support, the mesostructured catalysts allowed higher acetic acid conversion and hydrogen yield compared to the nonporous Ni/CeO2. The best catalytic performance and the lowest coke formation (120.6 mgcoke·gcat -1·h-1) were obtained with the mesostructured Ni/CeO2. This sample reached almost complete conversion (>97%) at 500 ºC, maintaining the hydrogen yield over 51.5% after 5 h TOS, being close to the predicted value by the thermodynamic equilibrium that is due to the synergistic coordination between Ni and CeO2 particles.
Oxidative steam reforming of acetic acid on Ni catalysts: Influence of the La promotion on mesostructured supports
(Elsevier, 2023) Megía, Pedro J.; Morales, Anabel; Vizcaíno, Arturo J.; Calles, José A.; Carrero, Alicia
In this work, the support effect and the La2O3 promotion of Ni-based catalysts on the oxidative steam reforming of acetic acid as bio-oil model compound has been studied. Ni/ SBA-15 showed the worst catalytic performance with an acetic acid conversion dropping below 30% at 500 C ascribed to active phase oxidation. In contrast, Ni supported over mesoporous CeO2 (CeO2-m) reached better catalytic performance and lower coke formation due to the higher Ni dispersion and oxygen mobility of the support. On the other hand, La2O3 promotion to SBA-15 and CeO2-m led to even higher Ni dispersion and prevented sintering during the reforming reaction. This effect resulted in an improvement in the catalytic performance for both promoted samples. As a consequence of low Ni crystallite size and high oxygen mobility, Ni/La2O3eCeO2-m reached almost complete conversion (~96%), the highest hydrogen yield (~53%) maintained for 5 h with the lowest coke formation...
Thermodynamic Comparison between Conventional, Autothermal, and Sorption-Enhanced Bio-oil Steam Reforming
(American Chemical Society, 2025-01-10) Megía, Pedro J.; Rocha, Claudio; Vizcaíno, Arturo J.; Carrero, Alicia; Calles, José A.; Madeira, Luis M.; Soria, Miguel A.
This study presents a comprehensive thermodynamic analysis comparing three bio-oil steam reforming processes: traditional steam reforming, autothermal reforming, and sorption-enhanced steam reforming. Using Aspen Plus V12.1 software, simulations were performed to evaluate the hydrogen production, energy requirements, and influence of key process variables such as the temperature, pressure, or steam-to-carbon ratio. While traditional steam reforming is capable of achieving high hydrogen production, it requires substantial external energy input to drive forward the reaction, given the endothermic nature of the reactions. In comparison, autothermal reforming allows thermally neutral conditions by integrating endothermic steam reforming with exothermic partial oxidation reactions. Although the energy requirements significantly decrease, it also leads to lower hydrogen yields due to its consumption in the oxidation processes. In contrast, sorption-enhanced steam reforming improves hydrogen production compared to the other configurations ascribed to the in situ CO2 capture by using sorbents that shift the equilibrium toward hydrogen with purities over 98%, thus minimizing the need for additional gas separation processes apart from reducing the CO and CH4 formation. Additionally, the exothermic nature of the CO2 capture reactions contributes to reducing the energy requirements or even generates excess energy at certain conditions that can be used as a heat source. The bio-oil composition showed minor variations in hydrogen yields, making these findings applicable to different bio-oil compositions