ETS-4 shows great potential to achieve effective separation of challenging mixtures due to its promising tunability of pores. However, the regulation of pore size is largely limited by its low thermal stability. Here, Na-ETS-4 was synthesized by the hydrothermal method and additionally modified via ion exchange coupled with thermal treatment. Structures of all synthesized samples were examined using a variety of characterization techniques. Both adsorption equilibrium and kinetics of CO2 and CH4 on these adsorbents were evaluated on custom-made adsorption units. In addition, the mechanism of CO2 adsorption on different structural models of ETS-4 was revealed via combining with the molecular dynamics (MD) simulations. Ion exchange largely improves the thermal stability of ETS-4 and its adsorption capacities for CO2 and CH4. Ba-ETS-4-350 exhibits the largest equilibrium selectivity of 12.42 and the greatest Henry’s selectivity of 2178.51. The radial distribution function (RDF) results reveal the main adsorption sites of CO2 in different ETS-4 structures.
The separation of methane and nitrogen is critical for upgrading low-grade natural gas. However, their similar physicochemical properties render efficient separation extremely challenging. This study explores the application of Engelhard titanosilicate-4 for N 2 /CH 4 separation. Framework thermal contractibility is tailored by regulating crystallization time. Thermal activation enables precise pore-size modulation, affording a superior separation selectivity of 15.1. Furthermore, the material properties are evaluated through structural characterization, adsorption isotherm measurements, and kinetic tests. Finally, in the simulation of a two-bed six-step vacuum pressure swing adsorption (VPSA) process, the obtained methane product has a purity exceeding 95%, validating the promising practical application potential of this adsorbent.
Octafluoropropane (C3F8) is widely used as etching agent in refrigeration, air conditioning and semiconductor industries. However, due to its long lifespan and strong infrared absorbing ability, once C3F8 is emitted, the atmospheric radiation absorbing ability will be permanently altered, which will result in a serious greenhouse effect. Therefore, the efficient removal technology of C3F8 is crucial in protecting the environment and alleviating the greenhouse effect. In this work, a series of X-ETS-4 (X: Mg, Ca, Sr, Ba) molecular sieves were synthesized by solvothermal and ion-exchange method. The morphology and structure of the prepared X-ETS-4 were characterized by FT-IR, XRD, and SEM, etc. The adsorption performance of the X-ETS-4 on C3F8 are determined by fixed-bed adsorption breakthrough experiments and single-component isothermal adsorption experiments. The adsorption mechanism was investigated using different adsorption theoretical models. The results show that Ba-ETS-4 exhibits high adsorption capacity and high adsorption selectivity for C3F8, achieving C3F8 adsorption separation at very low concentration (C3F8/N2 volume ratio = 1:400). The saturated adsorption capacity of Ba-ETS-4 on C3F8 reaches 155.17 mg/g (298 K, 170 kPa), which is 15.49 times more than that of Na-ETS-4. In addition, the ideal adsorption solution theory (IAST) separation selectivity of C3F8/N2 reaches 341–941 in the pressure range of 0–170 kPa.
危险品化学品经营许可证（带存储）