Development of practically available up-scaled high-silica CHA-type zeolite membranes for industrial purpose in dehydration of N-methyl pyrrolidone solution

作者：Sato Kiminori^*; Sugimoto Kazunori; Shimotsuma Naoto; Kikuchi Tomohisa; Kyotani Tomohiro; Kurata Tsunehiko

来源：Journal of Membrane Science, 2012, 409: 82-95.

DOI：10.1016/j.memsci.2012.03.032

• High-silica zeolite
• Membrane
• Calcination
• Pervaporation
• Dehydration
• Preferred orientation
• Evolutional selection

This is the report on the first practically available calcined high-silica zeolite membranes in an industrial scale synthesized using an organic structure directing agent for an application of dehydration of N-methyl pyrrolidone [NMP] solution by pervaporation (PV). A manufacturing method for high-silica CHA-type tubular membrane (Si/Al = 8) with 40 cm long was developed for industrial purpose. Furthermore, mass-production with high reproducibility came to be possible for commercialization. The potential membrane performance in PV was measured systematically at the wide range of conditions in temperatures of 90-130 degrees C and feed compositions of water concentration in the feed of 1-50 wt.%. The permeation flux of 36 kg m(-2) h(-1) and 2.5 x 10(-6) mol m(-2) s(-1) Pa-1 for water permeance with separation factor (alpha) of 1100 were observed at 130 degrees C in a feed mixture of water (50 wt.%)/NMP (50 wt.%).
A practical dehydration test was performed for a batch of 44 kg hydrous NMP (H2O 30 wt.%/NMP 70 wt.%) using a practical membrane module containing 31 pieces of tubular membranes with a membrane area of 0.4 m(2). The product of anhydrous NMP with 99.5 wt.% could be obtained at 110 degrees C by PV for 400 min. These results demonstrate that the synthesized high-silica CHA-type membranes can be applied to dehydration of hydrous NMP solution at wide range of water contents in the feed.
The water diffusivities were determined based on the Maxwell-Stefan equations with the PV experimental results in the water-NMP system. The reduction was observed in water diffusivity of 1 order of magnitude with decreasing of water contents from the pure water to water (1 wt.%)/NMP (99 wt.%) in the feed.
The synthesized high-silica CHA-type zeolite membranes exhibited the crystallographic orientation of [1 1 1](r) axis. Observations by scanning electron microscopy (SEM) and X-ray diffractometor (XRD) analysis on the synthesized samples as a function of time suggested that the growth mechanism of evolutional selection was operated in the membrane formation. This mechanism should contribute to the closed-packed polycrystalline membrane with sufficient permselective properties to practical PV applications.

• 出版日期2012-8-1