| 1. |
- Kulyk, Kostiantyn, et al.
(författare)
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Kinetics of Valeric Acid Ketonization and Ketenization in Catalytic Pyrolysis on Nanosized SiO2, gamma-Al2O3, CeO2/SiO2, Al2O3/SiO2 and TiO2/SiO2
- 2017
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Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 18:14, s. 1943-1955
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Tidskriftsartikel (refereegranskat)abstract
- Valeric acid is an important renewable platform chemical that can be produced efficiently from lignocellulosic biomass. Upgrading of valeric acid by catalytic pyrolysis has the potential to produce value added biofuels and chemicals on an industrial scale. Understanding the different mechanisms involved in the thermal transformations of valeric acid on the surface of nanometer-sized oxides is important for the development of efficient heterogeneously catalyzed pyrolytic conversion techniques. In this work, the thermal decomposition of valeric acid on the surface of nanoscale SiO2, gamma-Al2O3, CeO2/SiO2, Al2O3/SiO2 and TiO2/SiO2 has been investigated by temperature-programmed desorption mass spectrometry (TPD MS). Fourier transform infrared spectroscopy (FTIR) has also been used to investigate the structure of valeric acid complexes on the oxide surfaces. Two main products of pyrolytic conversion were observed to be formed depending on the nano-catalyst used-dibutylketone and propylketene. Mechanisms of ketene and ketone formation from chemisorbed fragments of valeric acid are proposed and the kinetic parameters of the corresponding reactions were calculated. It was found that the activation energy of ketenization decreases in the order SiO2 > gamma-Al2O3 > TiO2/SiO2 > Al2O3/SiO2, and the activation energy of ketonization decreases in the order gamma-Al2O3 > CeO2/SiO2. Nanooxide CeO2/SiO2 was found to selectively catalyze the ketonization reaction.
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| 2. |
- Halysh, Vita, et al.
(författare)
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Walnut shells as a potential low-cost lignocellulosic sorbent for dyes and metal ions
- 2018
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Ingår i: Cellulose. - : Springer. - 0969-0239 .- 1572-882X. ; 25:8, s. 4729-4742
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Tidskriftsartikel (refereegranskat)abstract
- Currently, it is necessary to develop new methods and materials for solving the problem of environmental pollution by various toxicants. For these purposes, vegetal materials can be used. In this study, efficient low-cost sorbents based on walnut shells, an agro-industrial by-product, were prepared by treatment with acetic acid or a mixture of acetic acid and hydrogen peroxide. It was shown that the treatments significantly affected the composition and structure of walnut shells and their sorption properties with respect to organic dyes (methylene blue, methyl violet, and murexide) and heavy metal ions. Methylene blue dye was used for additional studies on the effect of pH, contact time and kinetics of sorption. The maximum adsorption rate of the dye occurred within the first 30 min of contact, during which the concentration of methylene blue in the solution was reduced by more than half. Full sorption equilibrium was reached within 180-230 min for studied samples. The adsorption kinetics of methylene blue was found to best be described by pseudo-second-order kinetic model. It was shown that dyes adsorption processes were well described by Freundlich model, which takes into consideration the heterogeneity of the surface of the adsorbent. The obtained plant sorbents are characterized by a high sorption capacity for heavy metal ions (18-29 mg/g for Fe3+ and 33-44 mg/g for Cu-2). Due to their numerous advantages, such as the high sorption capacity, high availability and low cost of raw materials, simplicity of disposal and nontoxicity, the obtained natural sorbents may have a wide practical use in industrial wastewater treatment. [GRAPHICS] .
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| 3. |
- Nastasiienko, Nataliia, et al.
(författare)
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Catalytic Pyrolysis of Lignin Model Compounds (Pyrocatechol, Guaiacol, Vanillic and Ferulic Acids) over Nanoceria Catalyst for Biomass Conversion
- 2021
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Ingår i: Applied Sciences. - : MDPI AG. - 2076-3417. ; 11:16
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the mechanisms of thermal transformations of model lignin compounds (MLC) over nanoscale catalysts is important for improving the technologic processes occurring in the pyrolytic conversion of lignocellulose biomass into biofuels and value-added chemicals. Herein, we investigate catalytic pyrolysis of MLC (pyrocatechol (P), guaiacol (G), ferulic (FA), and vanillic acids (VA)) over nanoceria using FT-IR spectroscopy, temperature-programmed desorption mass spectrometry (TPD MS), and thermogravimetric analysis (DTG/DTA/TG). FT-IR spectroscopic studies indicate that the active groups of aromatic rings of P, G, VA, and FA as well as carboxylate groups of VA and FA are involved in the interaction with nanoceria surface. We explore the general transformation mechanisms of different surface complexes and identify their decomposition products. We demonstrate that decomposition of carboxylate acid complexes occurs by decarboxylation. When FA is used as a precursor, this reaction generates 4-vinylguaiacol. Complexes of VA and FA formed through both active groups of the aromatic ring and decompose on the CeO2 surface to generate hydroxybenzene. The formation of alkylated products accompanies catalytic pyrolysis of acids due to processes of transalkylation on the surface.
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| 4. |
- Nastasiienko, Nataliia, et al.
(författare)
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Decarboxylation of p-Coumaric Acid during Pyrolysis on the Nanoceria Surface
- 2021
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Ingår i: Colloids and Interfaces. - : MDPI AG. - 2504-5377. ; 5:4
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Tidskriftsartikel (refereegranskat)abstract
- Temperature-programmed desorption mass spectrometry (TPD MS) was used to study the pyrolysis of p-coumaric acid (pCmA) on the nanoceria surface. The interaction of pCmA with the CeO2 surface was investigated by FT-IR spectroscopy. The obtained data indicated the formation on the nanoceria surface of bidentate carboxylate complexes with chelate (Δν = 62 cm−1) and bridge structure (Δν = 146 cm−1). The thermal decomposition of pCmA over nanoceria occurred in several stages, mainly by decarboxylation. The main decomposition product is 4-vinylphenol (m/z 120). The obtained data can be useful for studying the mechanisms of catalytic thermal transformations of lignin-containing raw materials using catalysts containing cerium oxide and the development of effective technologies for the isolation of pCmA from lignin
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| 5. |
- Nastasiienko, Nataliia, et al.
(författare)
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Microwave-assisted catalytic pyrolysis of ferulic acid, as a lignin model compound
- 2023
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Ingår i: Journal of thermal analysis and calorimetry (Print). - 1388-6150 .- 1588-2926. ; 148:12, s. 5485-5492
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Tidskriftsartikel (refereegranskat)abstract
- Studies of the effect of microwave (MW) pretreatment on the pyrolysis of ferulic acid (FA), as a model compound of lignin, on the CeO2 surface are essential for understanding the prospects for the use of MW in catalytic pyrolytic technologies for the processing of lignocellulose. In this work, FT-IR spectroscopic studies of MW-pretreated samples of FA on the nanoceria surface were carried out. Their pyrolysis was studied by temperature-programmed desorption mass spectrometry (TPD MS). It was found that monodentate carboxylate complexes of FA are most susceptible to the influence of MW. MW-pretreatment for 300 s during pyrolysis of FA on the CeO2 surface leads to a decrease in the content of 4-vinylguaiacol in the final pyrolysis products. Phenolate complexes, as well as bidentate carboxylate complexes of FA on the CeO2 surface are less sensitive to MW. The use of MW-pretreatment promotes an insignificant decrease in the formation of polyaromatic compounds during the FA catalytic pyrolysis.
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| 6. |
- Nastasiienko, Nataliia, et al.
(författare)
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Thermal Transformation of Caffeic Acid on the Nanoceria Surface Studied by Temperature Programmed Desorption Mass-Spectrometry, Thermogravimetric Analysis and FT-IR Spectroscopy
- 2019
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Ingår i: Colloids and Interfaces. - : MDPI AG. - 2504-5377. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- The studies of pyrolysis of caffeic acid (CA) and its surface complexes is important for the development of technologies of heterogeneous catalytic pyrolysis of plant- and wood- based renewable biomass components. In this work, the structure and thermal transformations of the surface complexes of CA on the surface of nanoceria were investigated using Fourier transform-infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and temperature-programmed desorption mass spectrometry (TPD MS). It was found that CA on the surface of cerium dioxide forms several types of complexes: bidentate carboxylates, monodentate carboxylates and complexes formed as a result of interaction with phenolic hydroxyl groups. This is due to the ability of nanosized cerium dioxide to generate basic hydroxyl groups that can deprotonate phenolic groups to form phenolates on the surface. The main pyrolysis products were identified. The possible ways of forming 3,4-dihydroxyphenylethylene, acetylene carboxylic acid, pyrocatechol and phenol from surface complexes of CA were suggested. It was established that on the nanoceria surface effectively occur the decarboxylation, decarbonylation, and dehydration reactions of the CA, which are the desirable processes in biomass conversion technologies.
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