Giancarlo Luongo

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Luongo

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Giancarlo

ORCID

0000-0001-6398-8085

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Publications 1 - 8 of 8

Structural and thermodynamic study of Ca A- or Co B-site substituted SrFeO3−δ perovskites for low temperature chemical looping applications
Luongo, Giancarlo; Donat, Felix; Müller, Christoph R. (2020)
Physical Chemistry Chemical Physics
Perovskite-structured materials, owing to their chemical–physical properties and tuneable composition, have extended their range of applications to chemical looping processes, in which lattice oxygen provides the oxygen needed for chemical reactions omitting the use of co-fed gaseous oxidants. To optimise their oxygen donating behaviour to the specific application a fundamental understanding of the reduction/oxidation characteristics of perovskite structured oxides and their manipulation through the introduction of dopants is key. In this study, we investigate the structural and oxygen desorption/sorption properties of Sr1−xCaxFeO3−δ and SrFe1−xCoxO3−δ (0 ≤ x ≤ 1) to guide the design of more effective oxygen carriers for chemical looping applications at low temperatures (i.e. 400–600 °C). Ca A- or Co B-site substituted SrFeO3−δ show an increased reducibility, resulting in a higher oxygen capacity at T ≤ 600 °C when compared to the unsubstituted sample. The quantitative assessment of the thermodynamic properties (partial molar enthalpy and entropy of vacancy formation) confirms a reduced enthalpy of vacancy formation upon substitution in this temperature range (i.e. 400–600 °C). Among the examined samples, Sr0.8Ca0.2FeO3−δ exhibited the highest oxygen storage capacity (2.15 wt%) at 500 °C, complemented by excellent redox and structural stability over 100 cycles. The thermodynamic assessment, supported by in situ XRD measurements, revealed that the oxygen release occurs with a phase transition perovskite-brownmillerite below 770 °C, while the perovskite structure remains stable above 770 °C.
Chemical looping oxidative dehydrogenation of ethane: Elucidating the role of alkali metal salt promoters to suppress overoxidation
Luongo, Giancarlo; Donat, Felix; Müller, Christoph R. (2022)
Online Abstracts: 27th North American Catalysis Society Meeting
The molecular O2 feed in the oxidative dehydrogenation (ODH) of ethane is replaced by oxygen storage materials that release in situ gaseous O2 in a chemical looping scheme, without compromising the selectivity towards the desired product when suitable alkali metal salt coatings are applied.
Chemical Looping for Process Efficiency Enhancement
Luongo, Giancarlo (2023)
Highly Selective Oxidative Dehydrogenation of Ethane to Ethylene via Chemical Looping with Oxygen Uncoupling through Structural Engineering of the Oxygen Carrier
Luongo, Giancarlo; Donat, Felix; Bork, Alexander H.; et al. (2022)
Advanced Energy Materials
The oxidative dehydrogenation of ethane (ODH) to produce ethylene offers advantages compared to the industry standard steam cracking, but its industrial application is hindered by costly air separation units needed to supply oxygen. A chemical-looping-based oxidative dehydrogenation (CL-ODH) scheme is presented, in which oxygen carriers supply gaseous oxygen in situ, which then reacts with ethane in the presence of a catalyst at a comparatively low temperature (500 °C). A common challenge of chemical looping processes beyond combustion is to suppress the overoxidation of hydrocarbons to COx to enable high product yields. It is demonstrated that the overoxidation of ethane can be eliminated completely through structural engineering of the perovskite oxygen carrier involving alkali-metal-based carbonate coatings, while maintaining the materials’ ability to generate oxygen. Through CL-ODH, higher ethylene selectivity (≈91%) and yields (≈39%) are achieved compared to the conventional ODH scheme without oxygen carrier and cofeeding air/ethane. 18O-labeling experiments demonstrate that the carbonate layer functions like a diffusion barrier for ethane while being permeable for oxygen. Both the CL-ODH scheme and the material design strategy can be extended to other catalytic oxidation or dehydrogenation reactions requiring oxygen at different temperatures, offering enormous potential to intensify such processes.
Oxygen Nonstoichiometry and Defect Models of Brownmillerite-Structured Ca2MnAlO5+δ for Chemical Looping Air Separation
Tian, Yuan; Luongo, Giancarlo; Donat, Felix; et al. (2022)
ACS Sustainable Chemistry & Engineering
Brownmillerite-structured Ca2MnAlO5+δ has demonstrated excellent oxygen storage capacity that can be used for chemical looping air separation (CLAS), a potentially efficient approach to produce high-purity oxygen from air. To effectively utilize this material as an oxygen sorbent in CLAS, it is necessary to comprehensively understand its thermodynamic properties and the structure–performance relationships in the operating range of interest. In this work, the oxygen nonstoichiometry (δ) of Ca2MnAlO5+δ was systematically measured by thermogravimetric analysis (TGA) in the temperature ranging from 440 to 660 °C and under an oxygen partial pressure ranging from 0.01 to 0.8 atm. The partial molar enthalpy and entropy for the oxygen-releasing reaction were calculated using the van’t Hoff equation with an average value of 146.5 ± 4.7 kJ/mol O2 and 162.7 ± 5.1 J/K mol O2, respectively. The experimentally measured nonstoichiometry (δ) was well fitted by a point defect model applied in two regions divided by the predicted equilibrium P–T curve. The equilibrium constants for appropriate defect reactions were also determined. The thermochemical parameters, molar enthalpy and entropy for the main reaction, obtained from the defect model were 136.9 kJ/mol O2 and 225.3 J/K mol O2, respectively, showing reasonable agreement with the aforementioned values. The applicability of the defect model was also verified at a higher oxygen partial-pressure environment of up to 4 atm and exhibited reasonable prediction of the trend. The experimental studies on oxygen nonstoichiometry combined with the defect modeling provide useful insights into oxygen sorbents’ redox performances and helpful information for the design and optimization of oxygen sorbents in CLAS.
Activation in the rate of oxygen release of Sr0.8Ca0.2FeO3-δ through removal of secondary surface species with thermal treatment in a CO2-free atmosphere
Luongo, Giancarlo; Bork, Alexander H.; Abdala, Paula Macarena; et al. (2023)
Journal of Materials Chemistry A
We elucidate the underlying cause of a commonly observed increase in the rate of oxygen release of an oxygen carrier with redox cycling (here specifically for the perovskite Sr0.8Ca0.2FeO3-delta) in chemical looping applications. This phenomenon is often referred to as activation. To this end we probe the evolution of the structure and surface elemental composition of the oxygen carrier with redox cycling by both textural and morphological characterization techniques (N-2 physisorption, microscopy, X-ray powder diffraction and X-ray absorption spectroscopy). We observe no appreciable changes in the surface area, pore volume and morphology of the sample during the activation period. X-ray powder diffraction and X-ray absorption spectroscopy analysis (at the Fe and Sr K-edges) of the material before and after redox cycles do not show significant differences, implying that the bulk (average and local) structure of the perovskite is largely unaltered upon cycling. The analysis of the surface of the perovskite via X-ray photoelectron and in situ Raman spectroscopy indicates the presence of surface carbonate species in the as-synthesized sample (due to its exposure to air). Yet, such surface carbonates are absent in the activated material, pointing to the removal of carbonates during cycling (in a CO2-free atmosphere) as the underlying cause behind activation. Importantly, after activation and a re-exposure to CO2, surface carbonates re-form and yield a deactivation of the perovskite oxygen carrier, which is often overlooked when using such materials at relatively low temperature (<= 500 degrees C) in chemical looping.
On the Importance of Benchmarking the Gas-Phase Pyrolysis Reaction in the Oxidative Dehydrogenation of Propane
Nadjafi, Manouchehr; Cui, Yifan; Bachl, Marlon; et al. (2023)
ChemCatChem
The oxidative dehydrogenation of propane (ODP) proceeds catalytically on a gas-solid interface (heterogeneous reaction) and/or in the gas phase (homogeneous reaction) via a radical chain process. ODP may therefore combine interrelated contributions from the heterogeneous dehydrogenation and gas-phase reactions, which can be initiated by a catalyst. This study demonstrates that relatively high propene and ethene selectivities (ca. 80 % and 10 %) and propane conversions (viz., 10 % at 500 degrees C) can be achieved with an empty quartz reactor, which is comparable to the performances of state-of-the-art ODP catalysts (boron-based or supported VOx). Optimization of the post-catalytic volume of a h-BN catalyst bed tested at 490 degrees C allows to increase the conversion of propane from 9 % to 15 % at a propene selectivity of 77 %, highlighting this parameter as an important variable for improving catalytic ODP performances.
Experimental data supported techno-economic assessment of the oxidative dehydrogenation of ethane through chemical looping with oxygen uncoupling
Luongo, Giancarlo; Donat, Felix; Krödel, Maximilian; et al. (2021)
Renewable and Sustainable Energy Reviews
Ethylene is an essential building block in the petrochemical industry and it is almost exclusively produced via ethane steam cracking, a well-established albeit highly energy and carbon dioxide intensive process. The oxidative dehydrogenation of ethane is a promising alternative to steam cracking reactions due to its exothermic nature, which decreases the overall energy requirements and carbon footprint. The need of a capital intensive air separation unit for producing oxygen limits its potential for industrial application. The current study investigates an alternative route, i.e. the production of oxygen via chemical looping, where oxygen is released in-situ by suitable oxygen carriers. The chemical looping oxidative dehydrogenation, supported by original experimental data, and the steam cracking processes are simulated with ASPEN Plus®. A comprehensive analysis of the energy requirements and an economic assessment are carried out for both processes. Compared with state-of-the-art ethane steam cracking, the proposed process provides ~28% energy savings per tonnes of ethylene produced and ~21% reduction in the resulting ethylene price. Sensitivity analysis show that the economy of the chemical looping oxidative dehydrogenation process is strongly sensitive to the feedstock price.

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Giancarlo Luongo

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