Abstract
Unlike most gases, acetylene storage is a challenge because of its inherent pressure sensitivity. Herein, a square lattice (sql) coordination network [Cu(4,4′-bipyridine)2(BF4)2]n (sql-1-Cu-BF4) is investigated with respect to its C2H2 sorption behavior from 189 to 298 K. The C2H2 sorption studies revealed that sql-1-Cu-BF4 exhibits multistep isotherms that are temperature-dependent and consistent with the transformation from “closed” (nonporous) to four “open” (porous) phases induced by the C2H2 uptake. The Clausius–Clapeyron equation was used to calculate the performance of sql-1-Cu-BF4 for C2H2 storage at pressures >1 bar, which revealed that its volumetric working capacity at 288 K is slightly superior to acetone (174 vs 170 cm3 cm–3) over a safer pressure range (1–3.5 vs 1–15 bar). Molecular simulations provided insights into the observed switching phenomena, revealing that the layer expansion of sql-1-Cu-BF4 occurs via intercalation and inclusion of C2H2. These results indicate that switching adsorbent layered materials offer promise for utility in the context of C2H2 storage and delivery.
Highlights
Acetylene (C2H2) is an important feedstock for a range of chemical products including vinyl chloride, 1,4-butanediol, and acetylene black.[1]
Its flammable and explosive nature means that ca. 80% of C2H2 is used in situ without further shipping or storage,[4] the balance being mainly used in oxyacetylene torches, for which C2H2 is stored in pressurized containers
Current C2H2 storage technology involves desensitization by dissolving C2H2 in acetone that is predispersed in a porous monolith that completely fills a gas cylinder.[2,3]
Summary
Acetylene (C2H2) is an important feedstock for a range of chemical products including vinyl chloride, 1,4-butanediol, and acetylene black.[1]. CO2 sorption studies on sql-1-Cu-BF4 revealed that there is an additional higher uptake step at around 30 kPa when measured at 195 K (Figure 1c).[45,57] We wondered if. We correlated the gate sorption pressure and temperature by applying the Clausius−Clapeyron equation d ln P/(d(1/T)) = −ΔH/R (Figures 2d−f, S4 and Table S4).[43−46] The formation/dissociation enthalpies ΔfH/ΔdH of the first three steps were determined to be 31.8/31.6, 31.9/31.8, and 24.0/ 24.5 kJ mol−1 for the first, second, and third adsorption/. The network density of sql-1-Cu-BF4·6C2H2 excluding C2H2 is 1.07 g cm−1 (Table S5), meaning that its volumetric working capacity is higher than its gravimetric value. Sql-1-Cu-BF4 slightly better volumetric working capacity (174 vs 170 has a cm−3 cm−3) than acetone but in a lower and safer working pressure range (Figure 4b, group B). Such intrinsic heat management is desirable in sorbents and could make the charging process both safer and faster.[57,60]
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