Browsing by Author "Stateva R.P."

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    Analysis of hybrid separation schemes for levulinic acid separation by process intensification and assessment of thermophysical properties impact
    (2023-04-01) Tronci S.; Garau D.; Stateva R.P.; Cholakov G.; Wakeham W.A.; Errico M.
    From the time levulinic acid was listed as one of the top-12 building blocks for the sugars-high value compounds conversion, the interest in this compound increased. As part of its possible production route, the definition of viable separation schemes appears of paramount importance in the overall development of levulinic acid exploitation. Hybrid sequences where liquid-liquid extraction is followed by distillation were considered proving how the direct and direct -indirect separation schemes appeared to be the best alternatives in terms of total annual cost and environmental impact. These alternatives were further analyzed to improve their design by complementing the process simulator database with thermophysical experimental values. After obtaining a reliable design for the hybrid direct and direct-indirect configurations used as benchmarks, two intensified alternatives were generated. The first intensified configuration is classified as thermodynamically equivalent sequence, while the second one includes a divided wall column. For both, it was achieved a reduction of the total annual cost of 11% without any penalty for the environmental impact compared to the reference case.
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    Supercritical CO2 extraction of spent coffee grounds. Influence of co-solvents and characterization of the extracts
    (2020-07-01) Coelho J.P.; Filipe R.M.; Paula Robalo M.; Boyadzhieva S.; Cholakov G.S.; Stateva R.P.
    Spent coffee grounds (SCGs) were extracted with supercritical CO2 at temperatures of 313 K and 333 K, pressures up to 50.0 MPa and different scCO2 flow rates. The addition of co-solvents isopropanol, ethanol and ethyl lactate decreased the time to achieve the maximum oil yield, to half of that with pure CO2. Analysis of the extracted oils by NMR, showed that caffeine content was (0.56–3.96) % and DUFA and MUFA contents changed within (39.8–42.0) % and (12.9–15.8) %, respectively. The analyses of fatty acids performed by GC-FID revealed the composition of the oils being 76 % of the total constituted by palmitic and linoleic esters. The DPPH antioxidant capacity was improved up to 12.5 times with co-solvents. The kinetics of oil extraction from SCGs with pure scCO2 was modeled successfully by combining for the first time representation of the oil mixture by a single virtual molecule with group contribution methods.