Looking back on my Research on Membrane Technology–Creating Membranes

Last time, the author described the study of membrane fouling and the transport equation for membrane permeation. This time, the author would like to introduce his research on creating membranes. Polymer membranes and inorganic membranes have been developed. The polymer membranes are negatively and positively charged ultrafiltration membranes, which are polysulfone membranes with sulfonic acid groups and quaternary ammonium groups. The charged membranes have a complex separation mechanism, that is combination of separation by membrane pores and by charge repulsion between the membrane and solute. It was possible to separate not only salts but also various substances such as amino acids, peptides, and proteins. The transport equations of charged membranes were also studied. Inorganic membranes are mainly silica membranes produced by chemical vapor deposition, and zeolite membranes have also been produced, but they will not be introduced here. The author started with low–temperature deposition using ozone, and finally deposited membranes at high temperature (600 ℃) using various silica sources, and was able to obtain high–performance membranes. Since the advantages of inorganic membranes can be applied to membrane reactors, membrane reactors have been applied to steam reforming of methane, dehydrogenation of cyclohexane and methylcyclohexane, and thermal decomposition of hydrogen sulfide. In particular, the cyclohexane dehydrogenation membrane reactor operated continuously for 1,054 hours, and a small membrane reactor equipped with six 50 cm membranes was also developed.