Thermal fluids with high specific heat capacity through reversible Diels-Alder reactions

Abstract

Thermal fluids are used as heat transfer fluids and thermal energy storage media in many energy technologies ranging from solar thermal heating to battery thermal management. The heat capacity of state-of-the-art thermal fluids remains $50% of that of water (which suffers from a limited operation range between 0 C and 100 C), and their viscosities are typically more than one order of magnitude higher than that of water. Our results demonstrate that the heat capacity of the proposed thermochemical fluid is significantly higher than that of state-ofthe-art thermal fluids over a broad temperature range and is also higher than that of water between 60 C and 90 C. The viscosity of our liquid is only 3 times higher than that of water, and the operating temperature range is between À90 C and 135 C. Furthermore, a model was developed allowing for novel design of thermochemical thermal fluids in the future with even higher heat capacity.

Probing Complex Chemical Processes at the Molecular Level with Vibrational Spectroscopy and X-ray Tools

“…The first stage is usually smooth until a “turning point” appears at about 1–2 h in IR and 3–4 h in THz spectra. Lilley et al have also investigated the reaction kinetics using NMR . Our kinetic measurements of maleic anhydride via IR (Figure B v) follow the similar depletion kinetics of reactant measured by NMR.…”

“…The IR spectra of water at 25 °C and ice at −83 °C (extracted from ref ) are also shown with the peak positions marked by gray dashed lines. The kinetic traces on the right show the evolution of several feature peaks over time for (B iv) THz and (B v) FTIR, with the reactant concentration kinetics measured by Lilley et al using NMR …”

“…By their nature, cycloaddition reactions possess both a high ΔH (providing large heat capacity enhancement) and high ΔS (necessary to ensure reactions occur at practical temperatures), making them uniquely suited to the task and affording a large design space. 13 We chose to investigate the classic Diels−Alder reaction between furan and maleic anhydride (Figure 3B i) using our microreactors coupled with vibrational spectroscopies. Before measurements, 0.15 g of maleic anhydride (≥99.0%, Sigma-Aldrich) was first dissolved in 1.0 mL of furan (≥99.0%, Sigma-Aldrich).…”

“…In the cases described here, multiple spectroscopy techniques are used when investigating a system to acquire comprehensive insights into the chemical environment. We note that there are many other methods available to probe heterogeneous processes both in an in situ and multimodal manner, and we point the interested reader to these comprehensive reviews. , Methods such as neutron scattering and NMR spectroscopy have been deployed to probe heterogeneous processes, and in this Perspective we compare two examples of using such methods when describing phase changes in a plastic crystal and reactivity in a Diels–Alders reaction, respectively.…”

“…We note that there are many other methods available to probe heterogeneous processes both in an in situ and multimodal manner, and we point the interested reader to these comprehensive reviews. 9,10 Methods such as neutron scattering 11 and NMR spectroscopy 12 have been deployed to probe heterogeneous processes, and in this Perspective we compare two examples of using such methods when describing phase changes in a plastic crystal 7 and reactivity in a Diels− Alders reaction, 13 respectively. At Berkeley Lab, our team has successfully developed a series of microreactors integrated with both synchrotron-and nonsynchrotron-based spectroscopic techniques (Figure 1) to establish a molecular-level understanding of the dynamics in heterogeneous systems.…”