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Abstract: This paper proposes a concept of a process design for the separation and recovery of n-butanol from a five-component mixture, consisting of n-butanol, isobutanol, formaldehyde, water and methanol. The mixture is a common waste stream in the production of butylated amino resins; therefore, recovery of n-butanol is crucial to the efficiency of the process. The results show that up to 94% of the n-butanol present in the waste stream can be recovered. Under the studied conditions, 99.76% pure n-butanol can be obtained, while formaldehyde, water and methanol are present only in traces. The energy intensity of the process is estimated at 2.42 MJ/kg of purified n-butanol. The economic analysis of the process shows that the process is economically viable over a wide range of production capacities, as evidenced by high net present values and high return on investment values.
Keywords: recycling, n-butanol, azeotropic mixture, separation, process design, energy efficiency
Published in DKUM: 17.08.2023; Views: 325; Downloads: 41
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Abstract: Citrus flavonoids are very interesting for food and pharmaceutical industry since they possess many antioxidant properties and biological activities. Mandarin peels represent an important source of hesperidin and polymethoxy flavones nobiletin and tangeretin. Pommelo peels represent an important source of naringin that can be used as precursor for naringin dihdydro-2,3-chalcone artificial sweetener. Since pommelo peels possess good antioxidant and antimicrobial properties, their extracts are very interesting products for food industry. Therefore isolation of flavonoid from mandarin and pommelo peels is an important topic of investigations. The investigation of the doctoral dissertation is divided in four parts. The first part is focused on the determination of the optimal conditions for the isolation of hesperidin and naringin from mandarin and pommelo peels by conventional extraction. The optimal conditions and the influence of extraction parameters are determined by Taguchi methodology. Very good isolation efficiency of hesperidin, 61.3 mg HES from 1 g of mandarin peels, was obtained by 70 % acetone solution and extraction conditions: 60 °C, 90 min, material to solvent ratio 1/50 g/mL and 3 stages of extraction. The highest amount of naringin, 32.8 mg NAR were isolated from 1 g of material at conditions: conventional extraction, 120 min, albedo, 60 % ethanol, material to solvent ratio 1/50 g/mL and 60 °C. The simple procedure of conventional extraction shows results comparable to more sophisticated methods such as extraction with microwave and ultrasound. Taguchi experimental design was proved to be an efficient methodology to determine the optimal conditions and the parameters that significantly influence product properties. The second part of the investigation focuses on the characterization of mandarin and pommelo peel extracts and their antioxidant properties. Radical scavenging activity against DPPH and antioxidant capacity of lipid soluble and water soluble compounds were determined for mandarin and pommelo extracts. Taguchi experimental design was applied for determination of the influence of extraction parameters on antioxidant properties. The optimal conditions to prepare extracts with high antioxidant properties were also determined. In the third part the investigation focuses on the concentration and separation of citrus flavonoids by extraction with supercritical fluids. Supercritical CO2 was applied for the separation of polymethoxylated flavones (PMF) and flavanone glycoside from mandarin peels. The optimal conditions and the parameter influence on the separation were determined by using Taguchi experimental design. The influence of supercritical fluid extraction parameters on material pre-treatment and isolation of flavonoids was studied. These investigations show that supercritical CO2 is a potential solvent for isolation and separation of PMF from mandarin peels. The fourth and last part of the investigation focuses on the concentration of flavonoids in extract solutions. Since membrane separation processes are very interesting concentration methods in industry, microfiltration, ultrafiltration, nanofiltration and revese osmosis were used for concentration of mandarin and pommelo peel extract solutions. Microfiltration and ultrafiltration could be used in the separation steps after extraction, since they did not influence the amount of dry material and valuable compounds in tested solutions. Reverse osmosis and nanofiltration were shown as useful methods for separation of solvent from extract solutions.
Keywords: Flavonoids, hesperidin, naringin, citrus peels, mandarin (Citrus reticulata), pommelo (Citrus maxima), conventional extraction, supercritical fluid extraction, membrane separation processes, Taguchi experimental design
Published in DKUM: 22.04.2013; Views: 3928; Downloads: 477
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Abstract: Solubility of ▫$alpha$▫-tocopherol in CO2 and propane was determined at temperatures 303, 313, 333 and 353 K and over a pressure range from 79 to 286 bar for CO2 and 16 to 112 bar for propane. A static-analytic method was applied. The solubility of ▫$alpha$▫-tocopherol in dense CO2 under the conditions investigated was in the range of 0.2-17.0 mg/g CO2. The maximal solubilities of ▫$alpha$▫-tocopherol in propane were approximately up to ten times higher than in CO2 and were in the range from 38.9 to 171.9 mg/g propane. Phase equilibrium data for Milk Thistle seed oil in supercritical CO2 were determined at temperatures 313, 333 and 353 K and pressures ranging from 100 to 300 bar. The oil was previously additionally vitaminized and contained 1.9 wt.% of ▫$alpha$▫-tocopherol and 1.7 wt.% of free fatty acids (FFA). The solubility of oil in CO2 was in the range from 1.3 to 17.9 mg/g CO2. The distribution coefficients of ▫$alpha$▫-tocopherol and FFA between light and heavy phase were determined on a solvent free basis. The obtained separation factors increased with temperature and pressure to approximately 160-200 bar and decreased with a further increase of pressure.
Keywords: chemical processing, supercritical fluids, phase equilibria, separation factors, vitamin E, CO2, dense gases
Published in DKUM: 01.06.2012; Views: 2039; Downloads: 41
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Abstract: In the present work, membranes from commercially available Pebaxr MH 1657 and its blends with low molecular weight poly(ethylene glycol) PEG were prepared by using a simple binary solvent (ethanol/water). Dense film membranes show excellent compatibility with PEG system up to 50 wt.% of content. Gas transport properties have been determined for four gases (H2, N2, CH4, CO2) and the obtained permeabilities were correlated with polymer properties and morphology of the membranes. The permeability of CO2 in Pebaxr/PEG membrane (50 wt.% of PEG) was increased two fold regarding to the pristine Pebaxr. Although CO2/N2 and CO2/CH4 selectivity remained constant, an enhancement of CO2/H2 selectivity was observed. These results were attributed to the presence of EO units which increases CO2 permeability, and to a probable increase of fractional free-volume. Furthermore, for free-volume discussion and permeability of gases, additive and Maxwell models were used.
Keywords: chemical processing, membranes, membrane separation, CO2, Pebax, gas separation, blend membranes
Published in DKUM: 01.06.2012; Views: 2324; Downloads: 78
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Abstract: Asymmetric and porous polysulfone (PSf) membranes were prepared by wet phase separation. Binary (PSf)/N,N-dimethylacetamide (DMA) solutions with polymer concentrations of 12.5-30 wt % were cast in thicknesses of 80-700 m and immersed in a coagulation bath of pure water. The morphology of the formed membranesć cross sections consisted of a cellular structure and macrovoidsč the cellular structure density was highest when the cast solution contained about 21 wt % PSf, regardless of the cast thickness. The membranesć pure waterpermeability decreased as the cast thickness increased. The instantaneousonset of the turbidity, regardless of the PSf content and cast thickness, its steep growth, and relatively high end value were the main characteristics of the turbidity phenomena taking place during the formation of the protomembranes. Again, the membrane-forming system with a PSf/DMA solution with about 21 wt % polymer, regardless of the cast thickness, had thehighest turbidity end value. The shrinkage of the cast solutions into the corresponding protomembrane was also examined quantitatively. Inverse experiments showed that the direction of the gravitation field had no influence on the shrinkage of the membrane-forming ternary system or the membranesć morphology and its water permeability.
Keywords: polymeric membranes, polysulfone asymmetric porous membranes, wet-phase separation, membrane preparation, morphology
Published in DKUM: 01.06.2012; Views: 2067; Downloads: 90
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