Browsing by Author "Ma, Yiming"

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    Catalytic Conversion of Enzymatic Hydrolysis Lignin into Cycloalkanes over a Gamma-Alumina Supported Nickel Molybdenum Alloy Catalyst
    (ELSEVIER SCI LTD, 2021-03) Liu, Qingfeng; Bai, Yunfei; Chen, Hong; Chen, Mengmeng; Sang, Yushuai; Wu, Kai; Ma, Zewei; Ma, Yiming; Li, Yongdan; Tianjin University; Industrial chemistry; Department of Chemical and Metallurgical Engineering
    The efficient depolymerization and hydrodeoxygenation of enzymatic hydrolysis lignin are achieved in cyclohexane solvents over a gamma-alumina supported nickel molybdenum alloy catalyst in a single step. Under initial 3 MPa hydrogen at 320 °C, the highest overall cycloalkane yield of 104.4 mg/g enzymatic hydrolysis lignin with 44.4 wt% selectivity of ethyl-cyclohexane was obtained. The reaction atmosphere and temperature have significant effects on enzymatic hydrolysis lignin conversion, product type and distribution. The conversion of enzymatic hydrolysis lignin was also investigated over different nickel and molybdenum-based catalysts, and the gamma-alumina supported nickel molybdenum alloy catalyst exhibited the highest activity among those catalysts. To reveal the reaction pathways of alkylphenol hydrodeoxygenation, 4-ethylphenol was tested as a model compound. Complete conversion of 4-ethylphenol into cycloalkanes was achieved. A two-step mechanism of 4-ethylphenol dihydroxylation - hydrogenation is proposed, in which the benzene ring saturation is deemed as the rate-determining step.
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    Catalytic conversion of Kraft lignin into platform chemicals in supercritical ethanol over a Mo(OCH2CH3)x/NaCl catalyst
    (ELSEVIER SCIENCE BV, 2023-01-15) Liu, Qingfeng; Sang, Yushuai; Bai, Yunfei; Wu, Kai; Ma, Zewei; Chen, Mengmeng; Ma, Yiming; Chen, Hong; Li, Yongdan; Department of Chemical and Metallurgical Engineering; Industrial chemistry; Tianjin University
    A Mo(OCH2CH3)x/NaCl catalyst showed high efficiency in supercritical ethanol without adding H2 in the conversion of Kraft lignin to chemicals, including C6 alcohols, C8-C10 esters, benzyl alcohols and arenes. Control experiments were done with MoCl5, NaOC2H5 and the physical mixture of them. The Mo(OCH2CH3)x/NaCl catalyst exhibited superior activity among the samples examined. The overall yield increased as the reaction temperature increased from 260 to 300 °C. The yield of aromatic compounds achieved 303mg/g lignin over the Mo(OCH2CH3)x/NaCl catalyst at 300oC for 6h. MoCl5 and NaOC2H5 forms Mo(OCH2CH3)x in the catalyst preparation, which behaves as the active species in Kraft lignin conversion. The primary aromatics formed from the catalytic lignin depolymerization steps may undergo secondary reactions to form the final products.
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    Catalytic roles of Mo-based sites on MoS2 for ethanolysis of enzymatic hydrolysis lignin into aromatic monomers
    (ELSEVIER SCIENCE BV, 2023-01-15) Wu, Kai; Sang, Yushuai; Kasipandi, Saravanan; Ma, Yiming; Jiao, Hairui; Liu, Qingfeng; Chen, Hong; Li, Yongdan; Department of Chemical and Metallurgical Engineering; Industrial chemistry; Tianjin University
    The depolymerization of enzymatic hydrolysis lignin (EHL) is examined over one-step hydrothermal-synthesized MoS2 in ethanol without hydrogen gas. Value-added aromatic molecules, mainly including alkyl-substituted phenols (A-Ps), are obtained without char or tar formation. The MoS2 samples prepared with different Mo and S precursors have been tested and the highest aromatic monomer yield of 226.4 mg/g EHL is achieved over the MoS2 prepared with thioacetamide and sodium molybdate as precursors (STA-MoS2) at 320 °C for 12 h. Proper ratios of Mo6+/Mo5+ (~0.46–0.65) and (Mo6++Mo5+)/Mo4+ (~0.47–0.62) on the surface of MoS2 catalysts are found to be significant for the achievement of high overall aromatic monomer yield. MoOxSy species with Mo5+ and S22- is proposed as the active site for the production of complex alkyl phenols via demethoxylation and alkylation. The carbon deposition and the exchanges of sulfur and oxygen atoms resulted from the oxidization are likely responsible for the deactivation of catalyst.
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    Selective production of 2-(tert-butyl)-3-methylphenol from depolymerization of enzymatic hydrolysis lignin with MoS2 catalyst
    (ELSEVIER SCIENCE BV, 2023-01-15) Ma, Yiming; Sang, Yushuai; Wu, Kai; Liu, Qingfeng; Chen, Hong; Li, Yongdan; Tianjin University; Department of Chemical and Metallurgical Engineering; Industrial chemistry
    Low selectivity and complex product distribution are the main challenges for the utilization of lignin. Herein, the selective production of 2-(tert-butyl)-3-methylphenol (TBC), an antioxidant in the polymer industry, from depolymerization of enzymatic hydrolysis lignin (EHL) on a hydrothermally synthesized MoS2 catalyst is studied. The total aromatic monomer yield is 124.1mg/g EHL and the selectivity of TBC is up to 40.3wt% in methanol at 280oC under 2MPa H2 for 6h. The FT-IR analysis of products reveals that MoS2 has a high activity for demethylation, dehydroxylation and alkylation, and the dimer conversions reveal that C-O and C-C bonds in EHL are broken with MoS2. The guaiacol and its derivants are identified as the intermediate for formation of TBC in EHL depolymerizaiton according to the effect of time on product distribution and monomer converison.