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We prepared all-silica ZSM-58 zeolite membranes on α-alumina tubular supports and optimized their synthesis conditions. High-purity ZSM-58 zeolite membranes were prepared using a concentrated precursor solution (methyltropinium iodide/SiO2 and NaOH/SiO2 molar ratios > 0.05) with a H2O/SiO2 molar ratio of 52 at 413 K for 24 h. A ZSM-58/DOH mixed layer or a pure DOH layer was generated with ZSM-58 when the synthesis temperature exceeded 413 K and the synthesis time was longer than 24 h. The membranes prepared with a H2O/SiO2 molar ratio higher than 52 were not covered ZSM-58 zeolite and/or generated DOH zeolite. Further, we investigated the separation performance of the ZSM-58 zeolite membrane for CO2/CH4 and CO2/N2 gas mixtures as a function of feed pressure. At a pressure drop of 0.2 MPa, the membrane exhibited a CO2 permeance and CO2/CH4 mixture selectivity of 17 × 10−8 mol s−1 m−2 Pa−1 and 290, respectively, for a CO2/CH4 system, and a CO2 permeance and CO2/N2 selectivity of 29 × 10−8 mol m−2 s−1 Pa−1 and 44, respectively, for a CO2/N2 system. The mixture selectivity was lower than the single gas selectivity in CO2/CH4 separation due to competitive adsorption since CH4 mainly passes through non-zeolite pores. In contrast, the mixture selectivity was higher than the single gas selectivity in CO2/N2 separation because N2 permeation was inhibited by CO2 adsorption in the zeolite pores since N2 mainly passes through the zeolite pores. Thus, high-purity ZSM-58 zeolite membranes with high CO2 separation performances were obtained by the optimized synthesis conditions.

高いCO2/CH4分離性能を有するDDR型ゼオライト膜を用いたバイオガスの膜分離プロセスの開発を行うとともに，DDR型ゼオライト膜を用いた下水処理施設から発生するバイオガスの分離・精製と膜の耐久性を評価した．まず，簡素な1段分離プロセスに必要な膜性能を数理モデルにより把握し，実験によってDDR型ゼオライト膜を用いる際の最適な処理流量を決定した．次いで，実バイオガス分離・精製を行うために下水処理施設内にパイロットプラントを設置し，精製実験を行った．結果，目標とする回収CH4濃度90%，排出CO2濃度97%で精製可能であった．また，約40時間以上通気しても膜性能は変化しなかった．そのため，本研究で開発した膜分離プロセスは十分にバイオガスの分離・精製に適用することが可能であることがわかった．さらに，バイオガスの前処理を一切行なわず1600時間供給することにより，バイオガス中の不純物が膜分離性能に与える影響の検討を行った結果，長時間の通気によりバイオガス中に不純物として含まれる高級炭化水素，シロキサンなどの高沸点化合物により膜性能が低下すると考えられた．

Using hydrothermal synthesis, a highly hydrophobic DDR-type zeolite membrane was prepared on the outer surface of a porous α-alumina tube. The results of this study show that it is useful for CO2/CH4 separation. Single-gas permeation for CO2, CH4, H2, He, N2, and O2, and CO2/CH4 binary gas permeation, were measured, respectively, at pressures up to 5 and 2 MPa. The respective single-gas permeances of CO2 and CH4 at 298 K at a feed pressure of 0.2 MPa and a permeate pressure of 0.1 MPa were 4.2 × 10-7 and 1.2 × 10-9 mol m-2 s-1 Pa-1; the ideal selectivity for CO2/CH4 was 340. The permeances were in the following order: CO2 > H2 > He > O2 > N2 > CH4. Single-gas permeance was dependent on the relative molecular size of the DDR pore diameter. However, CO2 permeance dominated the adsorption affinity to the pore wall of DDR zeolite. In mixed-gas permeation experiments using the sweep method, the DDR-type zeolite membrane showed high selectivity for CO2/CH4 mixtures of 200 and high CO2 permeance of 3.0 × 10-7 m...

Clathrasil Deca-dodecasil 3R (DD3R) zeolite was synthesized in this study. Then, adsorption properties of carbon dioxide and methane were examined on the all-silica DD3R zeolite. Pure component adsorption isotherms are reported at temperatures of 273–348 K and pressures as high as 3 MPa. The isotherms follow a typical Type-I shape according to the Brunauer classification. They are well described using Langmuir and multi-site Langmuir models. Isosteric heats of adsorption and Henry’s Law constants of all adsorbates were determined. High selectivity of adsorption for carbon dioxide over methane suggests that the all-silica DD3R is an effective adsorbent or zeolite membrane material that can separate carbon dioxide and methane gaseous mixtures.

本研究では，非理想吸着相溶液（Non-ideal Adsorbed Solution: NAS）理論を用いて，活性炭BPLに対する揮発性有機化合物類（VOCs）の二成分吸着平衡の相関を検討した．まず，ヘッドスペースガスクロマトグラフィー（HSGC）法を用いて，293，323，353 Kにおけるメタノール，アセトン，ベンゼン，ヘキサンの吸着等温線および293 Kにおけるトルエンの吸着等温線を相対圧2×10−7–1×10−2の範囲で測定した．また，トルエン／ベンゼン，ベンゼン／アセトン，ヘキサン／アセトンの二成分吸着平衡をHSGC法と流通法を用いて測定した．そして，二成分吸着について理想吸着相溶液（Ideal Adsorbed Solution: IAS）理論による解析を行った結果，極性が類似しているベンゼン／トルエンでは推算が可能であったが，極性の異なるVOCを組み合わせた二成分系（ベンゼン／アセトン系，ヘキサン–アセトン系）においては予測が困難であった．一方，NASではIASに比べて高精度での相関が可能であった．さらに，NASは共沸点を示す疎水性のY型ゼオライトに対するトルエン／1-プロパノール系においても二成分吸着平衡の相関が可能であった．

In this study, we report a new effective sludge-digestion gas (biogas) adsorption storage technology. The experimental data of the pure and binary adsorption equilibrium of methane and carbon dioxide, which are the main components of the biogas, on five types of activated carbons at a temperature range of 273–333 K and pressures up to 6 MPa, were measured. Pure isotherms were fitted with the Toth and extended Toth models. Binary equilibrium was predicted using the Ideal Adsorbed Solution Theory (IAST) based on the extended Toth model with the experimental data being predicted as well. The differential enthalpy of the pure and binary adsorption was calculated, and storage densities of the binary gases, methane and carbon dioxide, considering the increased activated carbon temperature, were estimated using the adiabat and isobar of mixed gases in the biogas composition.

High-pressure excess adsorption equilibria of methane and carbon dioxide on five microporous activated carbons were measured. Adsorption isotherms were obtained at temperatures ranging from (273 to 333) K and at pressures ranging from (0.5 to 6000) kPa using a static volumetric apparatus. The experimental data were analyzed using the Toth model and the Dubinin−Astakhov model. The isosteric enthalpies of adsorption and the limiting heat of adsorption for both adsorbates on all activated carbons were calculated using the Clausius−Clapeyron equations and the van't Hoff equations, respectively.