The preparation of carbon materials with molecular sieve function is very challenging due to their noncrystalline structure, but they have broad application prospects in petrochemical industries for the separation of...
Olefin/paraffin separation is an important but challenging and energy-intensive process in petrochemical industry. The realization of carbons with size-exclusion capability is highly desirable but rarely reported. Herein, we report polydopamine-derived carbons (PDA-Cx, where x refers to the pyrolysis temperature) with tailorable sub-5 Å micropore orifices together with larger microvoids by one-step pyrolysis. The sub-5 Å micropore orifices centered at 4.1–4.3 Å in PDA-C800 and 3.7–4.0 Å in PDA-C900 allow the entry of olefins while entirely excluding their paraffin counterparts, performing a precise cut-off to discriminate olefin/paraffin with sub-angstrom discrepancy. The larger voids enable high C2H4 and C3H6 capacities of 2.25 and 1.98 mmol g−1 under ambient conditions, respectively. Breakthrough experiments confirm that a one-step adsorption-desorption process can obtain high-purity olefins. Inelastic neutron scattering further reveals the host–guest interaction of adsorbed C2H4 and C3H6 molecules in PDA-Cx. This study opens an avenue to exploit the sub-5 Å micropores in carbon and their desirable size-exclusion effect.
Separations of both C3 alkene/alkane and C4 alkadiene/alkenes are of great commercial significance as propylene and butadiene represent important feedstock chemicals, but the full extraction of them using carbon‐based separating agents has yet to be fully realized. Herein, derived from low‐cost starch precursors, we report a series of ultramicroporous starch‐based carbon materials (SC‐M; M = Na, K, Rb), with sub‐Ångstrom tunable ultramicropore apertures to separate the targeted gases with high purity. Among these materials, potassium derivative SC‐K can deliver high uptake capacities of propylene and butadiene (up to 2.20 and 2.36 mmol/g, respectively, at 100 kPa and 298 K) and superior selectivities due to a molecular‐sieving effect, as evidenced through adsorption isotherms and breakthrough experiments. Low heats of adsorption enable regeneration of SC‐M under mild conditions. To our knowledge, SC‐K represents the sole example of a porous carbon material that demonstrates potential for highly selective sieving‐driven separation of both C3 alkene/alkane and C4 alkadiene/alkenes.
Atomic layer etching (ALE) using the environmentally friendly electronic gas fluoromethane (CH3F) is guided for fabricating nanoscale electronic components. The adsorptive purification of CH3F provide a viable direction to remove trace amounts of impurities to produce highly pure CH3F (>99.9999%) for the ALE process. Herein, to remove trace propane (~100 ppm) in CH3F, we report synergetic thermodynamic and kinetic separation of C3H8/CH3F over glucose‐derived carbon molecular sieve CMS‐T, (T as pyrolysis temperature). With pore size slightly larger than the kinetic diameter of C3H8, CMS‐600 allows both strong confined adsorption of C3H8 and a higher diffusion rate of C3H8 over CH3F, resulting in a remarkable separation factor of 51.1. Breakthrough experiment demonstrates a high dynamic production capacity of 457 L kg−1 of 7 N CH3F (<100 ppb of C3H8) over CMS‐600 with excellent cycling stability. Adsorption purification over carbon provides a feasible approach for industrial hyperpurification of electronic gas.
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