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Author: search.filters.author.Kuncharam, Bhanu Vardhan ReddySubject: search.filters.subject.Biogas

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    Investigation of mixed matrix membranes of graphene and acid-treated graphene fillers in cellulose acetate and polyetherimide polymers for CO2 separation from biogas
    (Wiley, 2024-10) Kuncharam, Bhanu Vardhan Reddy
    Gas separation membranes are crucial for upgrading biogas by separating carbon dioxide (CO2) from biogas, thereby enhancing its calorific value and reducing greenhouse gas emissions. This study aims to improve CO2/CH4 separation using mixed-matrix membranes (MMMs) by incorporating graphene (Gr) and acid-treated graphene (AGr) fillers in a cellulose acetate (CA) polymer matrix. Similarly, polyetherimide (PEI) MMMs were also prepared with Gr and AGr fillers to draw a comparison. Various characterization techniques, including Fourier transform infrared spectroscopy, differential scanning calorimetry, field emission scanning electron microscopy, Raman spectroscopy, and X-ray diffraction, were employed to investigate the structural and morphological properties of the membranes and fillers. Gas permeation tests using a model biogas mixture (40% CO2 and 60% CH4) revealed that the 0.1%AGr/CA membrane achieved the highest CO2 permeability of 43 Barrers, which is approximately 307% more than that of the pure CA membrane, and showed a CO2/CH4 selectivity of 14.80. The 0.5%Gr/PEI membrane demonstrated the best performance among PEI-based MMMs, with a CO2 permeability of 17.48 Barrers and a CO2/CH4 selectivity of 8.96. These results indicate that the incorporation of Gr and AGr significantly enhances the gas separation performance over pure CA and PEI membranes.
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    Study of mixed matrix membranes with in situ synthesized zeolite imidazolate frameworks (ZIF-8, ZIF-67) in polyethersulfone polymer for CO2/CH4 separation
    (RSC, 2024-08) Kuncharam, Bhanu Vardhan Reddy
    Biogas, produced from anaerobic digestion, is a sustainable and renewable energy source. To upgrade biogas to Bio-CNG, CO2 must be removed from the raw mixture. Membrane separation is an economical process for the removal of CO2, and mixed matrix membranes (MMMs) are being explored for CO2/CH4 separation. MMMs are fabricated using techniques such as in situ techniques to overcome research gaps, such as in filler agglomeration and filler–polymer interfaces. In this work, MMMs were fabricated using the in situ growth of ZIF-8 and ZIF-67 in polyethersulfone (PES) and compared with traditional filler dispersion of ZIF-8 and ZIF-67. The fabricated MMMs were characterized and tested for gas permeation using a model biogas. Fourier-transform infrared (FTIR) spectroscopy and Field Emission Scanning Electron Microscopy (FESEM) analysis were conducted to confirm in situ synthesis of ZIF-8 and ZIF-67. CO2 permeability of in situ ZIF-8 and ZIF-67-based MMMs have enhanced to 84.5 Barrer and 78.8 Barrer, respectively, compared to pure PES membrane, which is around 25 Barrer. Similarly, ZIF-8 and ZIF-67-based traditional MMMs have shown an increase in the CO2 permeability of 75.6 Barrer and 68 Barrer, respectively. Additionally, the selectivity for CO2/CH4 separation increased for some of the prepared MMMs, demonstrating the effectiveness of the in situ fabrication method.
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    Synthesis and characterization of mixed-matrix material of Zirconium based metal organic framework (MOF: UiO-66-NH2) and poly(ether-urethane-urea)
    (Elsiever, 2020) Kuncharam, Bhanu Vardhan Reddy
    The sequestration of gases like CO2 and H2S from biogas is essential for its commercialization. Biogas being a carbon-neutral fuel has the potential to reduce our reliance on fossil-based fuels. However, the required technological advancements are yet to be achieved. Amongst the available technologies for biogas upgradation, membrane separations serves the best purpose owing to their less energy-intensive nature. Mixed matrix membranes are more appealing than commercial polymeric membranes for gas separation applications because of their enhanced performance. Also, incorporation of Metal-organic frameworks (MOFs) into a polymer suspension has been reported to improve the membrane performance. In this work, Amine functionalized Zirconium based metal-organic framework particles (UiO-66-NH2) bearing an average size of around 90–200 nm were synthesized by modulated hydrothermal technique. Characterization was done using XRD, FTIR, FESEM, and TGA. Poly (ether-urethane-urea) (PEUU) was considered based on its high H2S/CH4 respectively. PEUU was prepared using a two-step polycondensation technique. The synthesized polymers were analyzed for their chemical and thermal stability using techniques like 1H NMR, FTIR, TGA, and FESEM. After successful characterization, the MOF particles were incorporated into the polymer forming a mixed matrix membranes with particle loading in the 5–10 wt% range. The membranes were then coated on a porous support and preliminary gas permeability tests have to be carried out.