| 1. |
- 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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| 2. |
- 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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| 3. |
- Kulik, Tetiana, et al.
(författare)
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Catalytic Pyrolysis of Aliphatic Carboxylic Acids into Symmetric Ketones over Ceria-Based Catalysts : Kinetics, Isotope Effect and Mechanism
- 2020
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Ingår i: Catalysts. - : MDPI AG. - 2073-4344. ; 10:2
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Tidskriftsartikel (refereegranskat)abstract
- Ketonization is a promising way for upgrading bio-derived carboxylic acids from pyrolysis bio-oils, waste oils, and fats to produce high value-added chemicals and biofuels. Therefore, an understanding of its mechanism can help to carry out the catalytic pyrolysis of biomass more efficiently. Here we show that temperature-programmed desorption mass spectrometry (TPD-MS) together with linear free energy relationships (LFERs) can be used to identify catalytic pyrolysis mechanisms. We report the kinetics of the catalytic pyrolysis of deuterated acetic acid and a reaction series of linear and branched fatty acids into symmetric ketones on the surfaces of ceria-based oxides. A structure-reactivity correlation between Taft's steric substituent constants Es* and activation energies of ketonization indicates that this reaction is the sterically controlled reaction. Surface D3-n-acetates transform into deuterated acetone isotopomers with different yield, rate, E-not equal and deuterium kinetic isotope effect (DKIE). The obtained values of inverse DKIE together with the structure-reactivity correlation support a concerted mechanism over ceria-based catalysts. These results demonstrate that analysis of Taft's correlations and using simple equation for estimation of DKIE from TPD-MS data are promising approaches for the study of catalytic pyrolysis mechanisms on a semi-quantitative level.
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| 4. |
- Kulik, Tetiana, et al.
(författare)
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Catalytic Pyrolysis of Lignin Model Compound (Ferulic Acid) over Alumina : Surface Complexes, Kinetics, and Mechanisms
- 2021
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Ingår i: Catalysts. - : MDPI AG. - 2073-4344. ; 11:12
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Tidskriftsartikel (refereegranskat)abstract
- Studies of the thermochemical properties of the important model compound of lignin-ferulic acid (FA) and its surface complexes are substantial for developing technologies for catalytic pyrolysis of renewable biomass into biofuels and lignin-derived chemicals as well as for bio-oil upgrading. In this work, the catalytic pyrolysis of ferulic acid over alumina was studied by temperature-programmed desorption mass spectrometry (TPD MS), in situ FT-IR spectroscopy, thermogravimetric analysis, and DFT calculations. We established that both the carboxyl group and the active groups (HO and CH3O) of the aromatic ring interact with the alumina surface. We calculated the kinetic parameters of formation of the main products of catalytic pyrolysis: 4-vinylguaiacol, guaiacol, hydroxybenzene, benzene, toluene, cresol, naphthalene, and PACs. Possible methods of their forming from the related surface complexes of FA are suggested.
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| 5. |
- Kulyk, Kostiantyn, et al.
(författare)
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Chemisorption and thermally induced transformations of polydimethylsiloxane on the surface of nanoscale silica and ceria/silica
- 2015
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Ingår i: Polymer degradation and stability. - : Elsevier BV. - 0141-3910 .- 1873-2321. ; 120, s. 203-211
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Tidskriftsartikel (refereegranskat)abstract
- Compositions of polydimethylsiloxane (PDMS) polymer with nanosized silica and ceria/silica were prepared. The influence of these nano-fillers on the thermal stability and degradation mechanism of silicone polymer was investigated using Thermogravimetric Analysis (TGA) and Temperature Programmed Desorption Mass Spectrometry (TPD MS). The results showed that thermal decomposition of pure and adsorbed PDMS differs significantly. The three main stages of the PDMS thermal transformations in the adsorbed state were determined to be: 1) chemisorption of PDMS chains involving the terminal trimethylsilyl groups of the polymer and silanol groups of the silica surface; 2) formation and desorption of cyclic oligomers; 3) high temperature radical degradation of the polymer accompanied by the formation of methane and ethylene. The kinetic parameters of the corresponding reactions were calculated from the TPD MS data. It was found that nanoparticles of cerium dioxide strongly influence the degradation pattern, lower the decomposition temperature and catalyze the formation of methane.
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| 6. |
- Kulyk, Kostiantyn, et al.
(författare)
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Dimethylsilanone Generation from Pyrolysis of Polysiloxanes Filled with Nanosized Silica and Ceria/Silica
- 2016
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Ingår i: ChemPlusChem. - : Wiley. - 2192-6506. ; 81:9, s. 1003-1013
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Tidskriftsartikel (refereegranskat)abstract
- Temperature-programmed desorption mass spectrometry (TPDMS) was used to study the pyrolysis of PDMS and its composites with nanosized silica and ceria/silica. The results suggest that the elusive organosilicon compound, dimethylsilanone, is generated from PDMS over a broad temperature range (in some cases starting at 70 degrees C). The presence of nano-oxides catalyzes this process. Ions characteristic of the fragmentation of dimethylsilanone under electron ionization are assigned with the aid of DFT structure calculations. Possible reaction mechanisms for dimethylsilanone generation are discussed in the context of the calculated kinetic parameters. Observed accompanying products of PDMS pyrolysis, such as tetramethylcyclodisiloxane and hexamethylcyclotrisiloxane, indicate that multiple channels are involved in the dimethylsilanone release.
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| 7. |
- 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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| 8. |
- 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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| 9. |
- 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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