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- Carbon nitride (1)
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- Flammability (1)
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Most fluorinated hydrocarbons that shall replace refrigerants with high GWP, like R134a, are flammable. For evaluating inertization measures for explosion protection, flammability of low-GWP refrigerants R1234yf, R32 and R1132a blended with carbon dioxide, nitrogen and argon were studied experimentally in a closed autoclave at atmospheric conditions. Furthermore, a calculation method was adapted to reduce the experimental costs for flammability studies on these gas mixtures. For igniting R1234yf in the closed autoclave a newly developed ignition system was used that allows generating electric arcs with high ignition energy. Gas mixtures containing the mildly flammable R1234yf and R32 could be inerted by adding much less inert gas than mixtures containing R1132a, which is more similar to unfluorinated hydrocarbons regarding the explosion regions. By using the adapted model of constant adiabatic flame temperature profiles estimating the explosion limits of fluorinated hydrocarbons was possible with similar accuracy as for unfluorinated hydrocarbons.
Keywords: Explosion Protection, Inertization, Flammability, HFOs, HFC., R1234yf, R32, R1132a
A heptazine-based polymer network (HMP-3) with a donor–acceptor (D–A) structure was prepared and tested as catalyst for photocatalytic hydrogen evolution from water. Compared to other heptazine-based materials, which are typically prepared at high temperatures and have recently received much interest as metal-free photocatalysts, the low-temperature protocol applied here allows the defined introduction of organic functional groups within the polymer backbone. The structure of HMP-3 contains alternating heptazine and benzothiadiazole moieties as electron acceptors connected by aminobenzene bridges as electron donors. The resulting material leads to enhanced hydrogen evolution compared to graphitic carbon nitride materials prepared at high temperatures (>500 8C) most probably because of the stabilization of photogenerated charge carriers in the D–A structure.