Papers

1.	Lingcong Li, Shinta Miyazaki, Ziyang Wu, Takashi Toyao, Roman Selyanchyn, Zen Maeno, Shigenori Fujikawa, Ken-ichi Shimizu, Continuous direct air capture and methanation using combined system of membrane-based CO2 capture and Ni-Ca based dual functional materials, Applied Catalysis B: Environmental, 10.1016/j.apcatb.2023.123151, 123151, 123151, 2023.12, [URL], Direct CO2 capture from the air by membranes (membrane-based DAC, m-DAC) is a promising new technique to achieve CO2 net zero emissions. In addition, a continuous system for CO2 capture and its reduction by hydrogen using coupled reactors has scarcely been investigated. In this study, a new continuous system consisting of a m-DAC and a methanation process (m-DAC-M) was developed. For methanation, Ni nanoparticles supported on Ca-loaded Al2O3 (Ni-Ca/Al2O3; 10 wt% Ni and 6 wt% CaO) were utilized as a dual functional material (DFM). The Ni-Ca/Al2O3 exhibited high CH4 productivity and selectivity, good stability over 100 h, and high humidity resistance properties at a low reaction temperature of 350 °C. The catalytic properties of Ni-Ca/Al2O3 were elucidated using microscopic and spectroscopic techniques. The characterization results indicated that the CaO species not only served as CO2 adsorption sites to trap concentrated CO2 from the m-DAC system but also improved the reducibility of oxidized Ni species in the hydrogenation period, thereby promoting the reduction of surface carbonate species to CH4..
2.	Shigenori Fujikawa, Roman Selyanchyn, Toyoki Kunitake, A new strategy for membrane-based direct air capture., Polym. J. (Tokyo, Jpn.), 10.1038/s41428-020-00440-4, 53, 1, 219, 2021.01, [URL], ABSTRACT: Direct CO2 capture from the air, so-called direct air capture (DAC), has become inevitable to reduce the concentration of CO2 in the atmosphere. Current DAC technologies consider only sorbent-based systems. Recently, there have been reports that show ultrahigh CO2 permeances in gas separation membranes and thus membrane separation could be a potential new technology for DAC in addition to sorbent-based CO2 capture. The simulation of chemical processes has been well established and is commonly used for the development and performance assessment of industrial chemical processes. These simulations offer a credible assessment of the feasibility of membrane-based DAC (m-DAC). In this paper, we discuss the potential of m-DAC considering the state-of-the-art performance of organic polymer membranes. The multistage membrane separation process was employed in process simulation to estimate the energy requirements for m-DAC. Based on the analysis, we propose the target membrane separation performance required for m-DAC with competitive energy expenses. Finally, we discuss the direction of future membrane development for DAC..
3.	Olena Selyanchyn, Roman Selyanchyn, Shigenori Fujikawa, Critical role of the molecular interface in double-layered Pebax-1657/PDMS nanomembranes on highly efficient CO2/N2 gas separation, ACS Applied Materials and Interfaces, 10.1021/acsami.0c07344, 2020.07, [URL], ABSTRACT: In this work, we deposited a CO2-selective block copolymer, Pebax-1657, as a selective layer with a thickness of 2–20 nm on the oxygen plasma-activated surface of poly(dimethylsiloxane) (PDMS) used as a gutter layer (thickness ∼400 nm). This double-layered structure was subsequently transferred onto the polyacrylonitrile (PAN) microporous support and studied for CO2/N2 separation. The effect of interfacial molecular arrangements between the selective and gutter layers on CO2 permeance and selectivity has been investigated. We have revealed that the gas permeance and selectivity do not follow the conventional theoretical predictions for the multilayer membrane (resistance in series transport model); specifically, more selective CO2/N2 separation membranes were achieved with ultrathin selective layers. Detailed characterization of the chemical structure of the outermost membrane surface suggests that nanoscale blending of the ultrathin Pebax-1657 layer with O2 plasma-activated PDMS chains on the surface takes place. This nanoblending at the interface between the selective and gutter layers played a critical role in enhancing the CO2/N2 selectivity. CO2 permeances in the developed thin-film composite membranes (TFCM) were between 1200 and 3500 gas permeance units (GPU) and the respective CO2/N2 selectivities were between 72 and 23, providing the gas separation performance suitable for CO2 capture in postcombustion processes. This interpenetrating polymer interface enhanced the overall selectivity of the membrane significantly, exceeding the separation ability of the pristine Pebax-1657 polymer..

Presentations

1. Responsible instructor of the KIKAN Education course - 脱炭素エネルギー概論 (Spring Quarter, course code KED-GES1221J), 2023 ~ ongoing
2. Instructor in the (IUPE) Fundamental Organic Chemistry class (Autumn/Winter quarters), 2022 ~ ongoing
3. Co-instructor in the KIKAN Education Class - 脱炭素エネルギー技術と社会デザイン (Winter Quarter, course code KED-SSD5211J), 2022 ~ ongoing
4. Co-instructor in the Automotive Advanced Science class, Department of Automotive Science, Graduate School of Integrated Frontier Sciences (Spring Semester, class code 22692117 ) 2019 ~ ongoing
5. Co-instructor in the AMS International Communication seminar, Department of Automotive Science, Graduate School of Integrated Frontier Sciences (Summer/Winter Quarters) 2019 ~ ongoing
6. Co-instructor in the KIKAN Education Class - Introduction to Carbon Dioxide: Emissions, Capture, Storage and Utilization (Autumn Semester) 2020, course code 20892233