Prediction of Carbon Dioxide and Methane Adsorption on UiO-66 Metal–Organic Framework via Molecular Simulation

Publisher Copyright: © 2023 by the authors.The adsorption equilibrium of methane (CH4) and carbon dioxide (CO2) on the metal–organic framework (MOF) UiO-66 is studied via molecular simulation. UiO-66 is a versatile MOF with vast potential for various adsorption processes, such as biogas upgrading, CO2 capture, and natural gas storage. The molecular simulations employ the grand canonical Monte Carlo (GCMC) method, covering a temperature range of 298–343 K and pressures up to 70 bar for CH4 and 30 bar for CO2. The accuracy of different forcefields in describing the adsorption equilibria is evaluated. Two modelling approaches are explored: (i) lumping each hydrogen atom in the MOF framework to the heavy atom it is bonded to (united atom approximation) and (ii) considering explicit hydrogen atoms. Additionally, the influence of electrical charges on CO2 adsorption is also evaluated. The findings indicate that the most effective forcefield to describe the adsorption equilibrium is a united atom forcefield based on the TraPPE parametrization. This approach also yields an accurate calculation of the isosteric heat of adsorption. In the case of CO2, it is observed that the use of electrical charges enhances the prediction of the heat of adsorption, especially in the low-coverage region.publishersversionpublishe

Adsorption of carbon dioxide, methane, and nitrogen on zn(Dcpa) metal-organic framework

Norma Transitória DL 57/2016 ELAC2014/BEE0367Adsorption-based processes using metal-organic frameworks (MOFs) are a promising option for carbon dioxide (CO2 ) capture from flue gases and biogas upgrading to biomethane. Here, the adsorption of CO2, methane (CH4 ), and nitrogen (N2 ) on Zn(dcpa) MOF (dcpa (2,6-dichloro-phenylacetate)) is reported. The characterization of the MOF by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), and N2 physisorption at 77 K shows that it is stable up to 650 K, and confirms previous observations suggesting framework flexibility upon exposure to guest molecules. The adsorption equilibrium isotherms of the pure components (CO2, CH4, and N2 ), measured at 273–323 K, and up to 35 bar, are Langmuirian, except for that of CO2 at 273 K, which exhibits a stepwise shape with hysteresis. The latter is accurately interpreted in terms of the osmotic thermodynamic theory, with further refinement by assuming that the free energy difference between the two metastable structures of Zn(dcpa) is a normally distributed variable due to the existence of different crystal sizes and defects in a real sample. The ideal selectivities of the equimolar mixtures of CO2 /N2 and CO2 /CH4 at 1 bar and 303 K are 12.8 and 2.9, respectively, which are large enough for Zn(dcpa) to be usable in pressure swing adsorption.publishersversionpublishe

Two-column relay simulated moving-bed for gas-phase separations

A new two-column, relay, simulated moving bed process (2-column R-SMB) for gas-phase separations has been designed and implemented experimentally in this work. R-SMB differs from classical SMB processes by avoiding the partial withdrawal of products, since the outlet streams are handled in a relay mode. The outlet streams are either fully collected as product/waste or completely recycled to another column. In this work, the relay concept is applied for the first time in 2-column SMB processes and gas-phase separations. The process is designed and optimized through model-based computational simulation and the results obtained are validated experimentally. For the purpose, a new experimental lab-scale unit was designed and assembled. Please click Additional Files below to see the full abstract

A ubiquitous learning approach on robotics

Ubiquitous learning refers to the integration of learning processes with everyday environments and activities using technology. By leveraging ubiquitous learning principles in the field of robotics, we can foster an immersive and interactive learning environment that promotes continuous learning and knowledge acquisition. This paper presents an in-depth exploration of a ubiquitous learning approach for robotics with the aim to enhance the educational experiences and capabilities of robotic systems. Furthermore, it explores the potential benefits and challenges of ubiquitous learning in the field of robotics, such as increased adaptability, personalized learning experiences, and the development of lifelong learning skills. The results indicate that a ubiquitous learning approach can significantly enhance the learning capabilities of students.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support through national funds FCT/MCTES (PIDDAC) to CeDRI (UIDB/05757/2020 and UIDP/05757/2020) and SusTEC (LA/P/0007/2021).info:eu-repo/semantics/publishedVersio

Sorption of fluorinated greenhouse gases in silica-supported fluorinated ionic liquids

the contracts of Individual Call to Scientific Employment Stimulus 2020.00835.CEECIND (J.M.M.A.) / 2021.01432.CEECIND (A.B.P.), the Norma Transitória DL 57/2016. Publisher Copyright: © 2022 The Authors.The Kigali Amendment to the Montreal Protocol limits the global use of fluorinated greenhouse gases (F-gases) and encourages the development of a new generation of refrigerants with lower global warming potential. Therefore, there is a need to develop efficient and sustainable technologies to selectively capture and recycle the F-gases as new environmentally sustainable refrigerants. Here, ionic liquids (ILs) with high F-gas uptake capacity and selectivity were supported on silica and their potential as media for selective F-gas sorption was studied. For this purpose single-component sorption equilibria of difluoromethane (R-32), pentafluoroethane (R-125), and 1,1,1,2-tetrafluoroethane (R-134a) were measured at 303.15 K by gravimetry. The sorption data were successfully correlated using classical models of sorption thermodynamics. The results show that the IL supported in the porous volume and on the external surface of the porous silica controls the F-gas uptake in the composites and that changing the IL's cations and anions allows fine-tuning the selectivity of the sorption process. This work brings crucial knowledge for the development of new materials based on ILs for the selective sorption of F-gases.publishersversionpublishe

Absorption of Fluorinated Greenhouse Gases Using Fluorinated Ionic Liquids

funding of the KET4F-Gas project, SOE2/P1/P0823, co -funded by the Interreg Sudoe Programme through the European Regional Development Fund (ERDF). FCT/MCTES for financial support through IF/00190/2014 , IF/00210/2014 financial support through the Norma TransitOria DL 57/2016 Program Contract (FCT/MCTES). FCT/MCTES (UID/QUI/50006/2019).The increasing awareness of the environmental impact of fluorinated gases (F-gases) used in refrigeration is instigating the development of technologies to recover and recycle them. With this goal in mind, single-component absorption equilibrium isotherms at 303.15 K of F-gases in different ionic liquids (ILs) were determined using a gravimetric method. The selected F-gases are the most used in domestic refrigeration (R-32: difluoromethane, R-125: pentafluoroethane, and R-134a: 1,1,1,2-tetrafluoroethane). The results show that ILs containing a fluorinated alkyl side chain with four carbon atoms, that is, fluorinated ILs (FILs), have higher gas absorption capacity than conventional fluoro-containing ILs. All studied ILs showed ideal selectivity toward R-134a. Conventional fluoro-containing ILs showed better selectivities for the separation of the binary mixtures R-134a/R-125 and R-32/R-125, and FILs showed better selectivities for the R-134a/R-32 mixture. These results provide fundamental knowledge of the behavior of these new alternative solvents and key information for their application in the separation of F-gas mixtures of commercial refrigerants.authorsversionpublishe

Exploring the potential of biomass-derived carbons for the separation of fluorinated gases with high global warming potential

Funding Information: The single-component adsorption isotherms of R-32, R-125, R-134a, SF6 and N2 on the four biomass-derived porous carbons were measured by gravimetry in an ISOSORP high-pressure magnetic-suspension balance (MSB, Rubotherm GmbH, Germany). Approximately 0.30\u20130.40 g of the solid porous materials were loaded into the adsorption cells and then degasified at 373.15 K for 9 h under vacuum. After degassing, the sample was put into contact with the gas at a given pressure and temperature until the recorded mass stabilized. An adsorption point is under thermodynamic equilibrium when there are no discernible changes in weight, pressure, and temperature. This process is repeated continuously until the maximum pressure is reached. Finally, depressurization is performed to measure desorption points and check that the desorption branch of the isotherm coincides with the adsorption branch. The process is completed when the difference between the initial weight and the weight of the material after degassing is equal to zero. The adsorption equilibrium data are reported as excess adsorption, qex [28,30]; the corresponding values of total adsorption, q, determined from the experimental are reported in Tables S1\u2013S3 in the Supporting Information, SI. Finally, the adsorption-desorption equilibrium data were fitted using the isothermal dual-site Langmuir (DSL) model [ 54\u201356]. The parameters of the DSL model are shown in Tables S4 and S5 of SI.The authors acknowledge the financial support from the European Union's Horizon Europe research and innovation programme under grant agreement No 101082048\u2013- the MAR2PROTECT project. This work was also financed by national funds from FCT/MCTES (Portugal) through CEECIND/004431/2022 (I.M.), and the Norma Transitória DL 57/2016 Program Contract (R.P.P.L.R. and M.B.). Publisher Copyright: © 2024 The AuthorsThe development of advanced and innovative biomaterials with porous structural characteristics for the capture of fluorinated gases (F-gases) is important to contribute to the reduction of emissions of these gases with very high global warming potential. In this work, four biocarbons (CC-1:3H3PO4, CC-1:1H3PO4, CC-K2CO3 and CC-CO2) were produced by chemical and physical activation of corn cob biomass (CC). The adsorption equilibria of difluoromethane (R-32), pentafluoroethane (R-125), 1,1,1-tetrafluoroethane (R-125), 1,1,2-tetrafluoroethane (R-134a), sulphur hexafluoride (SF6), and nitrogen (N2) on these biocarbons were determined at 303.15 K. The highest adsorption capacities were obtained for CC-K2CO3 and CC-CO2 and a full characterization was also performed for these biomaterials at 283.15 and 323.15 K. On the other hand, the selectivities of SF6/N2 and the commercial refrigerants R-410A, R-407C, and R-407F were estimated using the Ideal Adsorption Solution theory (IAST). The results obtained for SF6/N2 show that the biocarbon CC-K2CO3 stands out from the other materials. In addition, the CC-CO2 shows a preference for R-32 over R-125 for the separation of the R-410A. Finally, CC-K2CO3 has a greater preference for R-134a over R-32 and R-125 in the R-407C and R-407F blends. Overall, these novel biocarbons improve the separation and purification of the F-gases under study, facilitating their application on a pilot scale.publishersversionpublishe

Drought tolerance conferred to sugarcane by association with Gluconacetobacter diazotrophicus: a transcriptomic view of hormone pathways

Sugarcane interacts with particular types of beneficial nitrogen-fixing bacteria that provide fixed-nitrogen and plant growth hormones to host plants, promoting an increase in plant biomass. Other benefits, as enhanced tolerance to abiotic stresses have been reported to some diazotrophs. Here we aim to study the effects of the association between the diazotroph Gluconacetobacter diazotrophicus PAL5 and sugarcane cv. SP70-1143 during water depletion by characterizing differential transcriptome profiles of sugarcane. RNA-seq libraries were generated from roots and shoots of sugarcane plants free of endophytes that were inoculated with G. diazotrophicus and subjected to water depletion for 3 days. A sugarcane reference transcriptome was constructed and used for the identification of differentially expressed transcripts. The differential profile of non-inoculated SP70-1143 suggests that it responds to water deficit stress by the activation of drought-responsive markers and hormone pathways, as ABA and Ethylene. qRT-PCR revealed that root samples had higher levels of G. diazotrophicus 3 days after water deficit, compared to roots of inoculated plants watered normally. With prolonged drought only inoculated plants survived, indicating that SP70-1143 plants colonized with G. diazotrophicus become more tolerant to drought stress than non-inoculated plants. Strengthening this hypothesis, several gene expression responses to drought were inactivated or regulated in an opposite manner, especially in roots, when plants were colonized by the bacteria. The data suggests that colonized roots would not be suffering from stress in the same way as non-inoculated plants. On the other hand, shoots specifically activate ABA-dependent signaling genes, which could act as key elements in the drought resistance conferred by G. diazotrophicus to SP70-1143. This work reports for the first time the involvement of G. diazotrophicus in the promotion of drought-tolerance to sugarcane cv. SP70-1143, and it describes the initial molecular events that may trigger the increased drought tolerance in the host plant