Faculty Profiles - NORINAGA Koyo

Insights into structure-performance relationship in radial flow fixed bed reactor for CO2 methanation Reviewed

Zhang, W; Lin, YX; Norinaga, K

INTERNATIONAL JOURNAL OF HYDROGEN ENERGY Vol. 48 ( 64 ) page： 24594 - 24606 2023.7

Language：English Publishing type：Research paper (scientific journal) Publisher：International Journal of Hydrogen Energy

The extraction of petroleum and natural gas is often accompanied by a large number of associated gases, especially the high CO<inf>2</inf> content reservoirs facing the emission of a large amount of CO<inf>2</inf>. CO<inf>2</inf> methanation is recognized as one of the suitable candidates for CO<inf>2</inf> utilization to reduce the emission of CO<inf>2</inf>. Because of the highly exothermic nature of the reaction, however, it is very important to enhance the heat transfer process inside the reactor and inhibit the formation of hot spots. In the fixed bed reactor, the heat transfer in the radial direction is greatly limited compared with that in the axial direction. Thus, this work adopted the radial flow reactor to evaluate the CO<inf>2</inf> methanation process by the means of a numerical model based on OpenFOAM. Four types of radial flow reactor configurations, namely centrifugal Z-type, centrifugal Π-type, centripetal Z-type, and centripetal Π-type, were compared. The fluid flow, heat transfer, and reaction performances for these reactors were discussed under consistent operating conditions. Results show that the centrifugal Π-type structure has the most uniform flow field. In terms of heat transfer and reaction performance, the centripetal Z-type structure is the best among the four radial flow reactor configurations. These findings provide a theoretical basis and technical guidance for designing and developing radial flow reactors.

DOI： 10.1016/j.ijhydene.2023.03.343

Polycyclic aromatic hydrocarbons (PAHs) and soot formations under different gasifying agents: Detailed chemical kinetic analysis of a two-stage entrained flow coal gasifier Reviewed

Tailin Li, Cheolyong Choi, Kazui Fukomoto, Hiroshi Machida, Koyo Norinaga

Fuel Vol. 343 page： 127876 - 127876 2023.7

Facile pyridinization of bio-based furfural into 3-hydroxypyridines over Raney Fe catalyst Reviewed

Ren, DZ; Jiang, XL; Zhang, NH; Duo, J; Norinaga, K; Huo, ZB

BIOMASS CONVERSION AND BIOREFINERY Vol. 13 ( 9 ) page： 8115 - 8121 2023.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Biomass Conversion and Biorefinery

Production of pyridine derivatives from bio-based feedstocks instead of fossil fuels is a promising strategy. The development of effective heterogeneous catalysts and mild reaction systems for pyridinization of renewable biomass derivatives remains a huge challenge. In this article, a direct and environment-friendly method was reported to produce 3-hydroxypyridine from bio-based furfural in water over a Raney Fe catalyst. Raney Fe exhibited an efficient catalytic performance for activation of the aldehyde group of furfural and afforded an 18.2% yield of 3-hydroxypyridine at 120 °C with ammonia as N source. The polymerization of furfural on the catalyst in hot water was the main cause of deactivation, which was verified by the scanning electron microscope (SEM), X-ray diffraction (XRD), and N<inf>2</inf> adsorption and desorption analysis. A possible mechanism for this reaction was also proposed. This study provides a new way for academia and industry to realize the synthesis of nitrogen-containing chemicals from biomass and its derivatives.

DOI： 10.1007/s13399-021-01802-5

CFD simulation of CVD reactors in the CH3SiCl3(MTS)/H2 system using a two-step MTS decomposition and one-step SiC growth models Reviewed Open Access

Ogawa, T; Fukumoto, K; Machida, H; Norinaga, K

HELIYON Vol. 9 ( 4 ) page： e15061 2023.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Heliyon

In this study, we report on a computational fluid dynamics (CFD) simulation of the chemical vapor deposition reactor of silicon carbide (SiC) in the methyltrichlorosilane (MTS, CH<inf>3</inf>SiCl<inf>3</inf>)/H<inf>2</inf> system. The formation of SiC thin film is controlled by various process parameters, such as temperature and pressure. In this study, we propose a reaction mechanism of MTS decomposition to SiC growth on a substrate surface for CVD reactors in the CH<inf>3</inf>SiCl<inf>3</inf>(MTS)/H<inf>2</inf> system. The reaction mechanism has two gas-phase pyrolysis reactions and one SiC film formation reaction. However, we individually build and validate MTS decomposition and SiC growth models to reduce uncertainty. An in-house version of reactingFoam, a reactive flow solver within OpenFOAM v2006, was used as the simulation tool. Our model accurately reproduced MTS decomposition for T = 1100–1350 K and [H<inf>2</inf>]/[MTS] = 2.65–14 at p = 101,325 Pa. Then, the MTS decomposition model was coupled with the SiC growth model, and the coupled model was applied to the SiC deposition data. The model could reproduce multiple datasets through validation studies.

DOI： 10.1016/j.heliyon.2023.e15061

Lattice Boltzmann study on the effect of hierarchical pore structure on fluid flow and coke formation characteristics in open-cell foam for dry reforming of methane Reviewed Open Access

Lin, YX; Yang, C; Zhang, W; Machida, H; Norinaga, K

CHEMICAL ENGINEERING SCIENCE Vol. 268 2023.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Chemical Engineering Science

Dry reforming of methane (DRM) is one of the feasible strategies for carbon capture and utilization. However, the DRM process has a high tendency toward carbon deposition, which is restricted to industrial applications. In order to further improve coke formation resistance, open-cell foam with hierarchical pore structure was investigated. An artificial algorithm was adopted to construct a hierarchical pore structure in open-cell foam. Based on a 3-D lattice Boltzmann model, this work explored the effect of two hierarchical pore structure parameters on the fluid flow and coke formation characteristics in open-cell foam, which are hierarchical pore volume ratio (V<inf>2</inf>/V<inf>1</inf>) and hierarchical pore size ratio (d<inf>2</inf>/d<inf>1</inf>). The results indicated that increasing V<inf>2</inf>/V<inf>1</inf> and d<inf>2</inf>/d<inf>1</inf> can significantly promote permeability. Under the restriction ofV<inf>2</inf>/V<inf>1</inf> = 4, from d<inf>2</inf>/d<inf>1</inf> = 1 to 4, the coke formation rate decreases by approximately 57.49 %. These findings provide a theoretical basis and technical guidance for designing and developing open-cell foam reactors.

DOI： 10.1016/j.ces.2022.118380

Estimation of effective thermal conductivity in open-cell foam with hierarchical pore structure using lattice Boltzmann method Reviewed

Japanese Gasification Technology Reviewed

NODA Reiji, ENOMOTO Hiroshi, NAMIOKA Tomoaki, FUSHIMI Chihiro, HOSOKAI Sou, NORINAGA Koyo

Nihon Enerugii Gakkai Kikanshi Enermix Vol. 102 ( 1 ) page： 74 - 79 2023.1

Lin, YX; Yang, C; Zhang, W; Fukumoto, K; Saito, Y; Machida, H; Norinaga, K

APPLIED THERMAL ENGINEERING Vol. 218 2023.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Thermal Engineering

Effective thermal conductivity in open-cell foam with hierarchical pore structure was estimated using lattice Boltzmann method. A new structure algorithm was proposed to reconstruct hierarchical pore structure in open-cell foam. In order to elucidate the heat transfer characteristics in hierarchical pore structure, the effect of structure parameters, namely the hierarchical pore size ratio (d<inf>2</inf>/d<inf>1</inf>), the hierarchical pore volume ratio (V<inf>2</inf>/V<inf>1</inf>), and temperature on the effective thermal conductivity was investigated. These results indicated that hierarchical pore structure is unfavorable to the effective thermal conductivity in open-cell foam for the heat conduction process. At high temperatures (T<inf>ave</inf> = 450–1650 K), however, the effective thermal conductivity in hierarchical pore structure is higher than that in uniform pore structure considering heat radiation. Furthermore, for the heat conduction process, a correlation of the effective thermal conductivity related to open-cell foam with hierarchical pore structure was proposed and validated by available experimental data.

DOI： 10.1016/j.applthermaleng.2022.119314

Boosting in-situ hydrodeoxygenation of fatty acids over a fine and oxygen-vacancy-rich NiAl catalyst br Reviewed Open Access

Wang, JY; Ren, DZ; Zhang, NH; Lang, JY; Du, YY; He, WH; Norinaga, K; Huo, ZB

RENEWABLE ENERGY Vol. 202 page： 952 - 960 2023.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Renewable Energy

Hydrodeoxygenation (HDO) of fatty acids into long-chain alkanes for aviation fuels with alcohol hydrogen donor at mild condition over Ni-based catalyst is a practicable subject. However, highly active sites design for Ni-based catalyst remains significant challenges. Herein, a fine NiAl particle catalyst with numerous oxygen vacancy sites was fabricated via hydrothermal and reduction treatment. Introduction of small amount of Al species into Ni catalyst not only reduces the Ni particle size exposing plenty of active sites, but also generates oxygen vacancies in AlO<inf>x</inf> and sets up charge transfer in Ni-AlO<inf>x</inf> interfaces, thus guarantees the excellent in-situ HDO activity of fatty acids using isopropanol as hydrogen donor. Density functional theory calculation results further reveal that Ni (111) modified by AlO<inf>x</inf> with oxygen vacancy improves the charge density in Ni-AlO<inf>x</inf> interface and enhances the adsorption of fatty acid, facilitating the hydrodeoxygenation process. Benefiting from these attributes, Ni–Al<inf>0.33</inf>O<inf>x</inf> presented superior catalytic activity and stability, which achieved 93.2% yield of n-heptadecane at 250 °C and was able to reuse at least 4 times. Therefore, the as-prepared Ni–Al<inf>0.33</inf>O<inf>x</inf> is a promising Ni-based catalyst for alkanes production via in-situ HDO of fatty acids at mild conditions.

DOI： 10.1016/j.renene.2022.11.095

Modeling and estimating kinetic parameters for CO2 methanation from fixed bed reactor experiments Reviewed

Tsuboi T., Yasuda S., Choi C., Zhang W., Machida H., Norinaga K., Yajima T., Kawajiri Y.

Journal of Advanced Manufacturing and Processing Vol. 5 ( 1 ) 2023.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Advanced Manufacturing and Processing

CO<inf>2</inf> methanation, which converts CO<inf>2</inf> and hydrogen into methane as fuel, is one of the promising candidates for the development of CO<inf>2</inf> utilization technologies. Recently, a highly active catalyst made of Ni/ZrO<inf>2</inf> for methanation has been developed, and is currently investigated as a potential use in a high-performance reactor. However, design of reactor must be carried out carefully, since this reaction is highly exothermic, which may cause reactor runaway and deterioration of catalysts. For this problem, a mathematical model that can predict the behavior inside the reactor is necessary. In this work, we consider the methanation reaction of CO<inf>2</inf> in a reactor model and estimate the kinetic parameters in the reaction rate model from experimental data. In the parameter estimation using literature values and Tikhonov regularization, eight kinetic parameters in the rate equations were identified from 64 data points with a wide range of conditions. We confirm that molar fractions at the reactor exit predicted by this reactor model are in good agreement with the experimental results. Furthermore, the developed model was validated to predict the compositions and temperature that were not used in the estimation. We expect the developed model will be a powerful tool for the reactor design.

DOI： 10.1002/amp2.10145

Large-eddy simulation of the non-adiabatic reforming process of hot coke oven gas using a flamelet-based approach Open Access

New Data Processing Method for Heavy Oil Components Analyzed by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Reviewed Open Access

KATANO Keita, SUZUKI Teruo, MATSUMOTO Kotaro, KATO Hiroshi, NORINAGA Koyo

Journal of the Japan Petroleum Institute Vol. 66 ( 4 ) page： 101 - 108 2023

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Petroleum Institute

A data processing method to automatically assign molecular formulae and correct the abundances was developed and used to improve the reliability and quantitative accuracy of data obtained via Fourier transform ion cyclotron resonance mass spectrometry. The technique was utilized to analyze fractions of atmospheric residue, and assigned molecular formulae for each fraction. The algorithm automatically identified nearly 20,000 heavy oil components. The reliability of the data processing technique was demonstrated by absolute mean mass errors in the range of 0.15-0.23 ppm. Distillation simulation was used to correct the abundances of assigned molecular formulae. The distillation properties were estimated from the molecular formulae, and corrections made to match the simulated results within 1 wt%. The correction factor indicated that lower boiling point components tended to require higher correction factors, suggesting that the ion transport efficiency of the instrument becomes lower in the lower molecular weight region.

DOI： 10.1627/jpi.66.101

Changes in Intermolecular Interaction Forces Inducing Glass Transition Determined by Three-Dimensional Aggregated Structural Models of Coal Reviewed Open Access

Hata Yuki, Hayashizaki Hideyuki, Matsuzaki Yoichi, Morimoto Masato, Takanohashi Toshimasa, Takahashi Takafumi, Kanehashi Koji, Norinaga Koyo

ISIJ International Vol. 63 ( 9 ) page： 1433 - 1440 2023

Language：English Publishing type：Research paper (scientific journal) Publisher：The Iron and Steel Institute of Japan

The three-dimensional aggregated structural models of two types of coals, A and B, were constructed. It is found that the density and the Tg of the models were qualitatively consistent with values obtained experimentally. The Tg of coals A and B calculated using the model structures are 315°C and 328°C, respectively. The effect of temperature on the distribution of cohesive energy was quantitatively elucidated using the three-dimensional aggregated structural models. The cohesive energy density (CED) of coal B was greater than that of coal A at temperatures <Tg. However, at temperatures >Tg, the CED of coal A is comparable to that of coal B. This implies that the molecules are more strongly aggregated in coal B than in coal A at low temperatures due to hydrogen bonding, and the intermolecular interaction is considered to have gradually relaxed above the Tg. It is concluded that differences in the molecular and cohesive structures of the coals led to differences in the distribution of van der Waals energy and electric energy at different temperatures. The van der Waals energy changed from attraction to repulsion at about 450°C and 285°C in coal A and B, respectively. Electric energy remained an attractive force as the temperature increased. The mechanism of the 13°C difference in the calculated Tg of each coal can be explained by the temperature change in the intermolecular force distribution. Therefore, this three-dimensional aggregated structural model can be used to understand the thermal behavior of aggregated molecules, such as coal thermoplasticity.

DOI： 10.2355/isijinternational.ISIJINT-2022-547

Experimental Study on Quantitative Evaluation of Transferable Hydrogen in Possible Raw Materials for Metallurgical Cokes Including Bituminous, Sub-bituminous, Lignite Coals and Biomass Reviewed Open Access

Zhang Lijuan, Uehara Yusuke, Nakamura Maki, Choi Cheolyong, Liu Chong, Machida Hiroshi, Hayashizaki Hideyuki, Kawai Yuya, Hata Yuki, Norinaga Koyo

ISIJ International Vol. 63 ( 9 ) page： 1441 - 1450 2023

Language：English Publishing type：Research paper (scientific journal) Publisher：The Iron and Steel Institute of Japan

Researchers have thoroughly studied coal pyrolysis over a long period, while the analysis of volatile evolution and the chemical structural changes of solid char were carried out individually in most of the studies. In this work, we quantified the chemical reactions to explain the different physical phenomena, such as softening and caking properties, exhibited by different ranks of coals during pyrolysis. Four typical carbonaceous feedstocks (bituminous, sub-bituminous, lignite coals, and biomass) were selected as test samples. The authors analyzed the generated gas during pyrolysis by using a quadrupole mass spectrometer (Q-MS) and the chemical structure of the pyrolyzed char via spectroscopic methods (NMR, FT-IR, CHNS, and XPS) to gain new insights into the pyrolysis mechanism of the carbonaceous feedstocks. Transferable hydrogen was introduced to define the hydrogen used to stable the free radicals formed during pyrolysis, which can be obtained by quantifying the conversion routes of hydrogen. The hydrogen released for the growth of aromatic clusters has three pathways, namely, (1) consumption by the hydrodeoxygenation reaction to produce pyrolytic vapor, (2) release as gaseous H2, and (3) transferable hydrogen. The calculation shows that the amount of transferable hydrogen during pyrolysis decreases as the coal rank gets lower. For pyrolysis up to 500°C, the amount of transferable hydrogen is 3.96, 2.32, and 1.36 mol/kg-coal for bituminous, sub-bituminous, and lignite coals, respectively. On the other hand, the transferable hydrogen of biomass needs to be further considered in terms of the effect of cellulose and hemicellulose’s structure.

DOI： 10.2355/isijinternational.ISIJINT-2022-517

YU Panlong, YADAV Sujeet, HU Yong, KAI Reo, NORINAGA Koyo, KUROSE Ryoichi, WATANABE Hiroaki

Journal of Thermal Science and Technology Vol. 18 ( 2 ) page： 23-00279 - 23-00279 2023

Language：English Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Mechanical Engineers and The Heat Transfer Society of Japan

Large-eddy simulation (LES) coupling with a non-adiabatic flamelet progress variable (NA-FPV) approach with reconstructed flamelet chemistry states is employed to simulate the hot coke oven gas (HCOG) reforming process. In the NA-FPV model, the chemistry states are first computed based on the correction factor for enthalpy defects and then modified by substituting the species statistics in the maximum heat loss state with those of less heat release to compensate for the unphysical results. The numerical results of LES coupling this NA-FPV model have been compared with the experimental measurement data in terms of temperature and yields, and reasonable agreements have been achieved. According to the LES results, it is seen O2 only participates in the combustion process in the upper stream and the combustion process which mainly consumes H2 and CO is to provide the other reforming process with heat and steam. In the upper and middle streams, the main HCOG jet is wrapped by the swirling high-temperature combustion products, and the reforming process primarily takes place by consuming CH4, polycyclic aromatic hydrocarbons (PAHs), and steam, while considerable H2, CO, and CO2 are produced. It is observed that accompanying the reforming process C2H2 is generated and it peaks in the middle stream, thus it is considered soot is formed in the complex reactions.

DOI： 10.1299/jtst.23-00279

Development of a kinetic model for CO2 methanation over a commercial Ni/SiO2 catalyst in a differential reactor Reviewed Open Access

Khuenpetch, A; Choi, C; Reubroycharoen, P; Norinaga, K

ENERGY REPORTS Vol. 8 page： 224 - 233 2022.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Energy Reports

Development of a kinetic model for CO<inf>2</inf> methanation over a commercial nickel catalyst was performed to consider pathways of CO<inf>2</inf> conversion via Sabatier and RWGS reactions. H<inf>2</inf>/CO<inf>2</inf> ratio in the feed gas composition was varied at the stoichiometry of the Sabatier reaction assuming a fictitious CO<inf>2</inf> conversion of 0 to 0.7. Non-stochiometric gas feeding and the addition of product gases, i.e., methane and steam, were also considered to examine reaction orders and inhibition effects. The kinetic tests were carried out at 300–350 °C and 0.1–0.9 MPa. GHSV corresponded to 37,494 h−1. The stable activity was achieved by forcibly stressing the catalyst under the equilibria at 500 °C for 35 h. The kinetic measurements were conducted at an isothermal differential fixed bed reactor in the absence of heat and mass transport limitations. The methanation reaction was first fitted with the power law and LH approaches by considering the Sabatier reaction. Then, the RWGS reaction was added to consider CO formation using the power law models. The results showed a better fitting of experimental observations by using the LH expression with the formation of formyl as RDS and the power law model with inhibiting influence of water.

DOI： 10.1016/j.egyr.2022.10.194

1-07 Highly selective electrochemical reduction of CO2 into CO achieved via indium thin-layer on zinc nanosheet over Cu foam Reviewed

SIRISOMBOONCHAI Suchada, MACHIDA Hiroshi, NORINAGA Koyo

Proceedings of Conference on Coal Science Vol. 59 ( 0 ) page： 14 - 15 2022.10

Language：English Publishing type：Research paper (scientific journal) Publisher：The Japan Institute of Energy

Electrochemical reduction (ECR) of CO2 is one of the most promising technologies for electrification of the conversion process of CO2 to obtain valuable chemicals/fuels without extreme condition requirements. Here, the performance of an electrocatalyst with the three-dimensional structure of indium thin-layer dispersed completely over Zn nanosheet structure growing on Cu/Cu foam (CF) is presented. This electrocatalyst was fabricated by electrodeposition of In and Zn over CF and exhibited a superior reduction at a Faradaic efficiency of 93.7% and an excellently long duration of 100h. Furthermore, owing to the synergy of the In thin layer, the Zn nanosheets provided a high active surface area and strong mechanical robustness during the reaction. Moreover, the InZnCu/CF catalyst presented low input energy of 2.90MWh for converting one ton of CO2 into CO, that is an encouraging achievement toward a feasible large scale applications.

DOI： 10.20550/jiesekitanronbun.59.0_14

2-06 Numerical simulation of polycyclic aromatic hydrocarbons and soot formations from coal volatiles in a Two-stage Entrained Flow Gasifier with detailed chemistry Reviewed

LI Tailin, CHOI Cheolyong, FUKUMOTO Kazui, MACHIDA Hiroshi, NORINAGA Koyo

Proceedings of Conference on Coal Science Vol. 59 ( 0 ) page： 40 - 41 2022.10

Language：English Publishing type：Research paper (scientific journal) Publisher：The Japan Institute of Energy

CO2 recirculation in the oxy-fuel Integrated Coal Gasification Combined Cycle (IGCC) system is essential for continuous use of coal in the future. This study presents a detailed kinetic investigation into coal gasification under O2-N2 and oxy-fuel (O2-H2O, O2-CO2) gasifying agents. The effects on polycyclic aromatic hydrocarbons (PAHs) and soot formation in the reductor of a two-stage entrained flow gasifier were simulated using CHEMKIN. The detailed chemical kinetic model includes 202 species, 1,351 gas-phase reactions, and 101 surface reactions. The numerical results showed that the oxy-fuel blown modes promoted tar reforming to complete elimination at 1,200°C (<1.5mg/Nm3). Because of a different tar conversion behavior, the O2-H2O blown mode provided a more potent tar-yield inhibition. In the case of soot formation, the amount of soot decreased under oxy-fuel blown modes. This behavior resulted from hydrogen abstraction and C2H2 addition (HACA) surface growth, and nucleation rate reductions. Also, the PAHs condensation had a weak effect on the soot formation rate among different gasifying agents. This study promises a better gasification process design for a two-stage entrained flow gasifier in an oxy-IGCC system.

DOI： 10.20550/jiesekitanronbun.59.0_40

2-26 Evaluation of lignin conversion into valuable chemicals via hydrogenation combined with fast pyrolysis processes Reviewed

ZHANG Lijuan, SIRISOMBOONCHAI Suchada, MACHIDA Hiroshi, NORINAGA Koyo

Proceedings of Conference on Coal Science Vol. 59 ( 0 ) page： 80 - 81 2022.10

Language：English Publishing type：Research paper (scientific journal) Publisher：The Japan Institute of Energy

Lignin, as an important part of lignocellulosic biomass, should give more attention to promote the utilization of biomass. Being a polymer composed of phenylpropane units, lignin is regarded as a promising candidate for obtaining olefins and aromatic compounds. Herein, thermo-catalytic hydrogenation was used as a pretreatment process of lignin, after that more olefins and aromatics were obtained from the solid hydrogenated lignin via fast pyrolysis. This two-stage valorization process was techno-economically evaluated by Aspen plus and compared with the conventional fast pyrolysis process of lignin. Process simulation based on the experiment data suggested the significant economic benefit of this strategy to convert lignin into valuable chemicals, like olefins, aromatics, and phenolics.

DOI： 10.20550/jiesekitanronbun.59.0_80

Analysis of Low Temperature-oxidation Mechanism for Coal by Using High Resolution Solid State NMR and Gas Analysis Reviewed Open Access

Hata Yuki, Takahashi Takafumi, Sakuragi Kiyoshi, Yamaguchi Akimasa, Saito Koji, Norinaga Koyo

Tetsu-to-Hagane Vol. 108 ( 10 ) page： 693 - 702 2022.10

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Iron and Steel Institute of Japan

Spontaneous combustion property of low rank coal, an important issue in coal science, has been substantially studied. However, there are few studies discussing quantitative chemical structural changes of coal during its oxidization under 80°C.In the present study, low rank coals of X and Y were oxidized in an adiabatic vessel where their temperature was increased due to spontaneous heating. Generated gases of H2O, CO2, and CO were analyzed by gas chromatography during the oxidization. As a result, coal Y, which was more easily oxidized than coal X, showed higher generation rate of CO2 and CO gas than coal X. Some of H2O generated during the oxidation must have been remained in coal as adsorbed water since the amount of water in the oxidized coal was higher than that before oxidation.13C MAS NMR spectra of coal X and Y indicated that and chemical reaction producing carboxyl acid in coal Y is more activated than that in coal X. Furthermore, the number of aromatic carbon was reduced during the oxidization. It implied that the aromatic carbon might contribute to oxidization reaction. Coal Y before oxidation had smaller number of aromatic carbon per one cluster than coal X, while the structural parameters of aliphatic carbons in coal X and Y were almost the same. It is considered that smaller number of aromatic carbons more destabilize carbon radicals to generate “active” species. Such active carbon radicals are suggested to also react with oxygen in the atmosphere.

DOI： 10.2355/tetsutohagane.TETSU-2022-010

Pretreatment of lignin by electrochemical hydrogenation to enhance the olefins and aromatic products during rapid pyrolysis Reviewed Open Access

Zhang, LJ; Sirisomboonchai, S; Choi, C; Machida, H; Norinaga, K

JOURNAL OF ANALYTICAL AND APPLIED PYROLYSIS Vol. 166 2022.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Analytical and Applied Pyrolysis

Lignin is one of the most promising biopolymers for producing hydrocarbons and aromatic compounds in nature. Electrochemical conversion of lignin is regarded as an attractive technology for producing various aromatic chemicals which are generally derived from fossil fuels. The author reports an electrochemical approach for hydrogenating alkaline lignin (AL), which uses relatively low-cost Ni foam as a working electrode under alkali electrolyte. The primary factors (such as power input, reactor type, temperature, reaction time, catalysts, and electrode substrates) of electrochemical hydrogenation were used to control the products' yield and features. The redox characteristics of the reaction system were directly compared with the cyclic voltammetry measurement under different parameters. After electrochemical hydrogenation (ECH), rapid pyrolysis was conducted on HAL samples to investigate the influence of electrochemical reactions on lignin. The maximum olefins and aromatics yield from HAL was increased to more than three times AL, accounting for 2.22 wt% and 4.07 wt%, respectively. Then, thermogravimetric analysis (TGA), elemental analysis (EA), Fourier-transform infrared spectroscopy (FTIR), and heteronuclear single quantum coherence (HSQC) NMR were employed to characterize hydrogenated lignin samples (HAL), as well as gas chromatography–mass spectrometry (GC-MS) was conducted to investigate the oil-phase products. This work focused on this electrochemical hydrogenation coupled with rapid pyrolysis process to give a possibility that converting lignin into not only liquid oil products, but solid hydrogenated lignin can be used to produce more olefins and aromatics in rapid pyrolysis, and presented the advantages and disadvantages of this two-stage process finally.

DOI： 10.1016/j.jaap.2022.105625