Browsing by Author "Hu, Tao"

Now showing 1 - 5 of 5
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    Carbocatalytic Oxidative Dehydrogenative Couplings of (Hetero)Aryls by Oxidized Multi-Walled Carbon Nanotubes in Liquid Phase
    (WILEY-V C H VERLAG GMBH, 2019-01-01) Wirtanen, Tom; Aikonen, Santeri; Muuronen, Mikko; Melchionna, Michele; Kemell, Marianna; Davodi, Fatemeh; Kallio, Tanja; Hu, Tao; Helaja, Juho; Department of Chemistry and Materials Science; Electrochemical Energy Conversion; University of Helsinki; Università degli studi di Trieste; University of Oulu
    HNO3-oxidized carbon nanotubes catalyze oxidative dehydrogenative (ODH) carbon–carbon bond formation between electron-rich (hetero)aryls with O2 as a terminal oxidant. The recyclable carbocatalytic method provides a convenient and an operationally easy synthetic protocol for accessing various benzofused homodimers, biaryls, triphenylenes, and related benzofused heteroaryls that are highly useful frameworks for material chemistry applications. Carbonyls/quinones are the catalytically active site of the carbocatalyst as indicated by model compounds and titration experiments. Further investigations of the reaction mechanism with a combination of experimental and DFT methods support the competing nature of acid-catalyzed and radical cationic ODHs, and indicate that both mechanisms operate with the current material.
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    Chemically Activated Spruce Organosolv Lignin as a Carbocatalyst for Heterogeneous Oxidative Dehydrogenations in the Liquid Phase
    (American Chemical Society, 2023-09-01) Lenarda, Anna; Melchionna, Michele; Aikonen, Santeri; Montini, Tiziano; Fornasiero, Paolo; Hu, Tao; Hummel, Michael; Helaja, Juho; Department of Bioproducts and Biosystems; Biopolymer Chemistry and Engineering; University of Helsinki; University of Trieste; University of Oulu
    Activated carbons obtained from organosolv lignin by chemical activation with KOH and oxidized with diluted HNO3 were studied as catalysts for aerobic oxidative dehydrogenation (ODH) reactions. The structure/activity relationship was investigated through multiple techniques revealing the crucial role of oxygen functionality distribution in promoting two mechanistically archetypical ODH probe reactions: (i) the tetrahydroquinoline (THQ) aromatization, which represents ODH triggered by hydride transfer, and (ii) the 2-phenyl indole homocoupling reaction, a model for single-electron transfer-promoted reactions. In particular, the catalytic activity, correlating with oxygen functionality distribution on the basis of X-ray photoelectron spectroscopy and temperature-programmed desorption analysis, was associated with the C═O surface functionalities, as confirmed by blocking experiments with 2,2,2-trifluoroethyl hydrazine. Kinetic profiling tools were employed to assess THQ ODH product inhibition effects on the overall yield of the process as well as the extent of stoichiometric activity of the carbocatalyst. The breadth of the developed catalysts’ applicability was explored through selected relevant ODH reactions.
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    Conversion of furfural to 2-methylfuran over CuNi catalysts supported on biobased carbon foams
    (ELSEVIER SCIENCE BV, 2021-05-01) Varila, Toni; Mäkelä, Eveliina; Kupila, Riikka; Romar, Henrik; Hu, Tao; Karinen, Reetta; Puurunen, Riikka; Lassi, Ulla; School services, CHEM; Department of Chemical and Metallurgical Engineering; Catalysis; University of Oulu
    In this study, carbon foams prepared from the by-products of the Finnish forest industry, such as tannic acid and pine bark extracts, were examined as supports for 5/5% Cu/Ni catalysts in the hydrotreatment of furfural to 2-methylfuran (MF). Experiments were conducted in a batch reactor at 503 K and 40 bar H2. Prior to metal impregnation, the carbon foam from tannic acid was activated with steam (S1), and the carbon foam from pine bark extracts was activated with ZnCl2 (S2) and washed with acids (HNO3 or H2SO4). For comparison, a spruce-based activated carbon (AC) catalyst and two commercial AC catalysts as references were investigated. Compressive strength of the foam S2 was 30 times greater than that of S1. The highest MF selectivity of the foam-supported catalysts was 48 % (S2, washed with HNO3) at a conversion of 91 %. According to the results, carbon foams prepared from pine bark extracts can be applied as catalyst supports.
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    Study of Ni, Pt, and Ru Catalysts on Wood-based Activated Carbon Supports and their Activity in Furfural Conversion to 2-Methylfuran
    (Wiley - VCH Verlag GmbH & CO. KGaA, 2018) Mäkelä, Eveliina; Lahti, Riikka; Jaatinen, Salla; Romar, Henrik; Hu, Tao; Puurunen, Riikka L.; Lassi, Ulla; Karinen, Reetta; Department of Chemical and Metallurgical Engineering; Industrial chemistry; Catalysis; University of Oulu; Kokkola University Consortium Chydenius
    Bio-based chemicals can be produced from furfural through hydrotreatment. In this study, 2-methylfuran (MF), a potential biofuel component, was produced with Pt, Ru, and Ni catalysts supported on wood-based activated carbons. The catalytic hydrotreatment experiments were conducted in a batch reactor at 210-240°C with 2-propanol as solvent and 40bar H2 pressure. Two types of activated carbon supports were prepared by carbonization and activation of lignocellulosic biomass (forest-residue-based birch and spruce from Finland). Both types of activated carbons were suitable as catalyst supports, giving up to 100% furfural conversions. The most important factors affecting the MF yield were the metal dispersion and particle size as well as reaction temperature. The highest observed MF yields were achieved with the noble metal catalysts with the highest dispersions at 240°C after 120min reaction time: 3wt% Pt on spruce (MF yield of 50%) and 3wt% Ru on birch (MF yield of 49%). Nickel catalysts were less active most likely owing to lower dispersions and incomplete metal reduction. Interesting results were obtained also with varying the metal loadings: the lower Pt loading (1.5wt%) achieved almost the same MF yield as the 3wt% catalysts, which can enable the production of MF with high yields and reduced catalyst costs. Based on this study, biomass-based renewable activated carbons can be used as catalyst supports in furfural hydrotreatment with high conversions.
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    Willow bark proanthocyanidins with potential for water treatment: Chemical characterization and zinc/bisphenol A removal
    (ELSEVIER SCIENCE B.V., 2023-08-01) Dou, Jinze; Varila, Toni; Salminen, Juha-Pekka; Tuomikoski, Sari; Hietala, Sami; Hemmi, Maria; Hu, Tao; Lassi, Ulla; Vuorinen, Tapani; Department of Bioproducts and Biosystems; University of Oulu; University of Turku; University of Helsinki; Wood Chemistry
    This study investigates the chemical structure of proanthocyanidin-rich crude extracts from willow bark and these materials were tested initially as adsorbents for artificial (waste)water treatment. The crude extracts were obtained through mild water extraction and the colorant fractions were further chromatographically fractionated to understand the chemical structure of the willow bark proanthocyanidins. The chemistry of crude extracts and purified fractions were investigated using nuclear magnetic resonance (NMR) and ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Both NMR (liquid and solid-state) and UPLC-MS/MS suggest that the crude extracts constitute of interflavan linked flavan-3-ols, i.e. proanthocyanidins with both procyanidin (PC)-type and prodelphinidin (PD)-type subunits, with the PC/PD ratio of approximately 2.3–2.5. PD-type proanthocyanidins were detected from the purified colorant fractions only with UPLC-MS/MS. Both the UPLC-MS/MS and size exclusion chromatography suggest that the crude extracts have an average oligomerization degree of roughly 5–6 flavan-3-ol units. Adsorption experiments showed that the activated foams made of crude extracts were effective in removing both zinc and Bisphenol A (BPA) with removal efficiencies of roughly 80–90% and thus these willow bark-derived proanthocyanidins are promising in water treatment. The significance of this study suggests the upgrading use of crude extracts for water treatment could significantly improve the value of willow bark.