Small–angle neutron scattering (SANS) is a technique used for sub–micron scale structural analysis of soft matters and biomacromolecules, but it can also be used to evaluate dynamics by taking advantage of the large difference in scattering length between hydrogen and deuterium. The author’s group has successfully used time–resolved SANS to measure the rates of phospholipid transfer between vesicles and flip–flop in vesicle membranes for the first time and has elucidated the differences in these rates among different phospholipids. In addition, measurements with lipid–transfer proteins revealed their lipid–transfer mechanism and the importance of their ability to bind two different types of lipids in carrying out the exchange of these lipids across the membrane along a concentration gradient. This review will present the details and applications of this method.

View full abstract

This review focuses on silicon–based amorphous membranes, which offer excellent resistance to heat and solvents and are applicable in various separation systems. It explores the development of these membranes, emphasizing two key factors: the diffusivity of permeating molecules and the affinity between membrane functional groups and permeating molecules. The review introduces organosilica membranes made from different bridged and side–chain alkoxysilanes, metal–coordinated membranes, and silicon carbide–based membranes. It also discusses methods for evaluating nano– and subnanoporous membranes and explains the generalized solution–diffusion model, which provides a unified understanding of processes like reverse osmosis, pervaporation, and vapor permeation. Finally, the practical applications of these membranes are highlighted, including a technology that recovers water and heat from high–temperature steam using organosilica membranes.

View full abstract

In recent years, there have been increasing interests in zeolite membranes. The membranes have been successfully applied at the industrial scale for solvent dehydration by pervaporation or vapor permeation. This review gives an overview of the recent research trends of zeolite membranes, especially of our current challenges to membrane reactors of esterification reaction and methanol synthesis in the carbon neutral field.

View full abstract

PDMS–HSZ mixed matrix membrane was used as an alcohol permeable pervaporation membrane. The PDMS– HSZ interface was found to contribute to ethanol permeation by creating binarization analysis technique. The pervaporation system was verified with IPA wastewater using element modules. Based on the demonstration results, we clarified the target values of membrane performance. The alcohol permeable pervaporation membrane can make a significant contribution to the alcohol purification process.

View full abstract

A contactor–type membrane reactor was developed to convert carbon dioxide utilization. An MFI zeolite layer was synthesized by hydrothermal synthesis on a porous ceramic substrate. By supplying methanol vapor to the MFI membrane at 400 ℃, olefins such as propylene were selectively obtained on the other side of the membrane. Olefin yields were around 90% and were stable over a 5 h test. Compared to powder catalysts, high propylene selectivities (3 or 258) were obtained for ethylene or propane at the same level of yield. It was found to be important to suppress Al dissolution from the ceramic substrate during hydrothermal synthesis of the MFI layer in order to obtain high activity.

View full abstract

Membrane reactors have been a topic of interest for decades, with developments across a range of applications. Due to the time–consuming nature of experimental systems, accurate process modeling and simulation is a potentially economical and efficient method of optimizing these systems. However, the complexity of model development and the limitations of computational resources often result in simplifications of the model physics. These simplifications or assumptions introduce errors that result in deviation with experiments. Here, modeling studies on zeolite membrane reactors are reviewed, followed by a discussion on the effects of major modeling assumptions on model accuracy.

View full abstract

We showed a technical introduction to zeolite membrane separation system, covering the solvent dehydration, gas separation and membrane reactor process. Having the potential to contribute to improvements in the efficiency of conventional processes, zeolite membrane separation system is a promising technology for energy conservation and ultimately decarbonization. Optimal membrane structure selection according to target separation is a crucial point for enhancing the efficiency of the membrane separation system and zeolite membranes developed by us are meticulously designed in detail and demonstrate high–level separation performance.

View full abstract

Intergovernmental Panel on Climate Change (IPCC) is producing the Sixth Assessment Report, which states that it is important to limit the temperature increase to 1.5 ℃ or less and that a drastic reduction of greenhouse gases is necessary to achieve this goal, and specific reduction targets have been set. Also in Japan, the 2050 Carbon Neutral Declaration has been issued and various measures are being implemented. In order to realize a carbon–neutral society, the development and combination of many technologies will be important, and zeolite membranes may be able to contribute to the realization of such a society by taking advantage of their various functions. This article outlines the roadmap for the realization of a carbon–neutral society, explains the specific role that zeolite membranes should play in realizing a CO₂ recycling society, and briefly introduces examples of our RD to reduce CO₂ emissions. I would like to encourage researchers to become aware of the issues and take up challenges in this field.

View full abstract

ZSM–5 membranes with different Al distribution were synthesized. Two types of ZSM–5 membranes with different Al distributions were prepared via secondary growth methods using pentaerythritol (PET) or tetrapropylammonium cation (TPA+) as organic structure-directing agents. It successfully demonstrated that membrane performance can improved drastically by Al distribution control. For example, Al and cations located in channel of Na–ZSM–5 membrane contributed to the high separation performance for methanol/H₂ mixture possibly because methanol adsorbed on Na⁺ in the channels easily blocked H₂ permeation.

View full abstract

Among the artificial kidneys used for the treatment of dialysis patients, our company is the only one in the world that manufactures and sells the Polymethyl Methacrylate (PMMA) hollow fiber membrane artificial kidney (Filtryzer^®), which efficiently adsorbs pathogenic proteins. Recently, we have advanced this PMMA hollow fiber membrane technology, elucidated the mechanism of porous structure formation, and successfully created PMMA porous fibers with a cross–sectional shape. Based on these achievements, we also designed a column tailored to the cross–sectional porous fibers and successfully commercialized FILTOR^® as a small, high–performance PMMA porous fiber column that adsorbs β₂–microglobulin (β₂–MG), the main causative protein of dialysis–related amyloidosis.

View full abstract