During acrylic acid (AA) storage, a quality loss occurs due to the formation of by-products such as diacrylic acid (DiAA), triacrylic acid (TriAA), and higher oligomers. This problem intensifies in the presence of water since the formation rate of oligomers increases and further by-products such as 3-hydroxypropionic acid (3-HPA) and 3-hydroxydiacrylic acid (3-HDiAA) are formed. However, water is often essential during storage and transport to raise the flash point or reduce the melting point. In this work, the formation kinetics are investigated for all mentioned components in pure and aqueous AA. The formation mechanisms of 3-HPA and 3-HDiAA are assumed as acid-catalyzed ester hydrolyses of DiAA or TriAA. The introduced reactions are modeled with the measured kinetic data in order to confirm the proposed reactions.
Interest in energy storage technologies is still increasing in times of excess of electricity generated by wind farms or solar plants. A key part of the energy storage technologies plays the efficient conversion of H2 and CO2 from renewable resources. Here, the process conditions for continuous catalytic hydrogenation of CO2 to CH3OH under supercritical conditions over lab‐synthesized Cu/ZnO/Al2O3 catalysts were investigated. A possible in situ phase separation of reaction products within the reactor due to the higher densities of the reaction mixture by the higher pressure could affect the kinetics and simplify downstream processing. The combination of thermodynamic studies and catalytic performance tests for CO2 hydrogenation under supercritical conditions is discussed and a process concept is presented.
The storage of excess electricity from renewable energy sources is nowadays a crucial topic. One promising technology is the methanol (CH3OH) synthesis from H2/CO2 mixtures. The achievable one‐pass conversion is limited within this exothermic equilibrium reaction. A possibility to overcome this limitation would be withdrawing CH3OH and H2O from the gas phase through in situ condensation under reaction conditions. In this work, the phase equilibrium for mixtures representative for different degrees of conversion was studied. A view cell was employed to determine systematically the single‐ and two‐phase regimes and obtain phase envelopes for mixtures of H2, CO2, CH3OH, and H2O from 66 to 305 °C and 61 to 233 bar. Furthermore, the densities in the single‐phase area were determined and quantified by an empirical model.
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