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Polysulfone membranes, used as contactors for CO 2 capture, are blended with two different hyperbranched polyethyleneimines modified with benzoyl chloride (Additive 1) and phenyl isocyanate (Additive 2) in different percentages. Fourier-transformed infrared spectra evidence the presence of urea and amide groups, whereas the field emission scanning electron microscopy images show differences in the microstructure of the blended membranes. Dielectric spectra determine the motions of the side and backbone chains, which can facilitate the diffusion of CO 2 . The spectra consist of six dielectric processes; three of them are due to the polysulfone (γ PSf , β PSf , and α PSf ), whereas the rest are characteristic of the additive (γ HPEI , β HPEI , and α HPEI ). The benzoyl chloride and phenyl isocyanate functional groups introduce variations in molecular mobility and modify the relaxations associated with the hyperbranched polyethyleneimine (HPEI). The additives also increase the conductivity of the blended membranes, which can compromise the performance of the membranes, specifically in the case of Additive 1. Ion hopping is found to be the prevailing charge transport mechanism while both relaxations, α HPEI and α PSf , are actives. These results, together with the final morphology of the membranes, may explain the greater absorption capacity of the membranes prepared with the hyperbranched polyethyleneimine modified with Additive 2., (© 2023 Wiley-VCH GmbH.)

This paper reports the preparation and characterization of asymmetric membranes for direct air capture (DAC) in polysulfone membrane contactors. In the previous studies it was found that blending the polysulfone with modified Lupasol G20 improved the polysulfone membrane performance; however, the hydrophobicity and stability of the additive require improvement for the application in gas/liquid system. In order to achieve this objective, in the current study, Lupasol G20 was grafted with phenyl isocyanate via urea linkages in a solvent-free and eco-friendly method. Membranes with different amount of the additive were prepared by phase inversion and characterized by several techniques in terms of morphology, porosity, wettability, and stability in aqueous KOH solution. Finally, CO 2 solubility and mass transfer coefficient were determined and correlated with membranes' performance in the direct air capture device. In general, it was found that the presence of the additive greatly improved the characteristics of the membranes in terms of CO 2 capture efficiency and robustness, outperforming the results obtained previously. The best results for were obtained with 5% additive content reaching 0.18 [mol/m2s]. [Display omitted] • Modified Hyperbranched Polyethyleneimine (UG20) was synthesized by grafting Lupasol G20 with phenyl isocyanate groups. • Polysulfone (PSF)/UG20 asymmetric blended membranes with different UG20 content, for CO 2 capture, were prepared by phase inversion. • CO 2 solubility, permeability and absorption values were improved in PSf/UG20 blended membranes. • CO 2 assimilation rate of blended membranes was higher than in natural stomata and in PSF-based modules previously reported. • PSf/UG20 5% displayed the highest CO 2 assimilation rate. [ABSTRACT FROM AUTHOR]

Highlights • Combined C 6 and CO 2 solvents coinjection with steam improved oil recovery. • Higher oil recovery is linked more to solvent properties than steam chamber shape. • Solubility of C 6 and C 7 , and CO 2 diffusion into the oil enhanced recovery. • The coinjection process resulted in a less fluctuated subcool temperature. Abstract Steam assisted gravity drainage (SAGD) is one of the most widely used processes of thermal recovery for heavy oil. Investigating the effectiveness of solvent coinjection with steam is an important aspect in the optimisation of SAGD process. So far, however, the effects of using CO 2 have not been closely examined. This study sheds light on the addition of hydrocarbon solvents with CO 2 which reached earlier maximum ultimate oil recovery (90%) than that for other solvents coinjection. This study shows that solubility of C 6 , heat loss reduction and CO 2 diffusion, are the main recovery mechanism in enhancing oil recovery. The present study highlights the steam propagation in the presence of C 6 and CO 2 and its relation to enhancing oil recovery. It is interesting to observe that physical properties of the injected fluid reduce the energy consumption. Another finding is that solvent coinjection leads to stable subcool, hence increase oil recovery. [ABSTRACT FROM AUTHOR]

We investigated the possibility of improving the performance of polysulfone (PSf) membranes to be used in carbon dioxide capture devices by blending PSf with a commercial polyethylene imine, Lupasol G20, previously modified with benzoyl chloride (mG20). Additive amount ranged between 2 and 20 wt %. Membranes based on these blends were prepared by phase inversion precipitation and exhibited different morphologies with respect to neat PSf. Surface roughness, water contact angles, and water uptake increased with mG20 content. Mass transfer coefficient was also increased for both N2 and CO2; however, this effect was more evident for carbon dioxide. Carbon dioxide absorption performance of composite membranes was evaluated for potassium hydroxide solution in a flat sheet membrane contactor (FSMC) in cross flow module at different liquid flow rates. We found that, at the lowest flow rate, membranes exhibit a very similar behaviour to neat PSf; nevertheless, significant differences can be found at higher flow rates. In particular, the membranes with 2 and 5 wt % additive behave more efficiently than neat PSf. In contrast, 10 and 20 wt % additive content has an adverse effect on CO2 capture when compared with neat PSf. In the former case, a combination of additive chemical affinity to CO2 and membrane porosity can be claimed; in the latter case, the remarkably higher wettability and water uptake could determine membrane clogging and consequent loss of efficiency in the capture device. [ABSTRACT FROM AUTHOR]