Litcius/Paper detail

Thermodynamic and Transport Properties of H<sub>2</sub>/H<sub>2</sub>O/NaB(OH)<sub>4</sub> Mixtures Using the Delft Force Field (DFF/B(OH)<sub>4</sub><sup>–</sup>)

Parsa Habibi, Julien R. T. Postma, Johan T. Padding, Poulumi Dey, Thijs J. H. Vlugt, Othonas A. Moultos

2023Industrial & Engineering Chemistry Research16 citationsDOIOpen Access PDF

Abstract

&lt;p&gt;Sodium borohydride (NaBH&lt;sub&gt;4&lt;/sub&gt;) has a high hydrogen (H&lt;sub&gt;2&lt;/sub&gt; ) gravimetric capacity of 10.7 wt %. NaBH&lt;sub&gt;4&lt;/sub&gt; releases H&lt;sub&gt;2&lt;/sub&gt; through a hydrolysis reaction in which aqueous NaB(OH)&lt;sub&gt;4&lt;/sub&gt; is formed as a byproduct. NaB(OH)&lt;sub&gt;4&lt;/sub&gt; strongly influences the thermophysical properties of aqueous solutions (i.e., densities, viscosities, and electrical conductivities) and the hydrolysis reaction kinetics and conversion of NaBH&lt;sub&gt;4&lt;/sub&gt;. Here, molecular dynamics (MD) simulations are performed to compute viscosities, electrical conductivities, and self-diffusivities of H&lt;sub&gt;2&lt;/sub&gt; , Na&lt;sup&gt;+&lt;/sup&gt;, and B(OH)&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt; for a temperature and concentration range of 298-353 K and 0-5 mol NaB(OH)&lt;sub&gt;4&lt;/sub&gt;/kg water, respectively. Continuous fractional component Monte Carlo (CFCMC) simulations are used to compute the solubilities of H&lt;sub&gt;2&lt;/sub&gt; and activities of water in aqueous NaB(OH)&lt;sub&gt;4&lt;/sub&gt; solutions for the same temperature and concentration range. A new force field is developed (Delft force field of B(OH)&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;: DFF/B(OH)&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;) in which B(OH)&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt; is modeled as a tetrahedral structure with a scaled charge of −0.85. The OH group in B(OH)&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt; is modeled as a single interaction site. This force field is based on TIP4P/2005 water and the Madrid-2019 Na&lt;sup&gt;+&lt;/sup&gt; force field. The MD simulations can accurately capture the densities and viscosities within 2.5% deviation from available experimental data at 298 K up to a concentration of 5 mol NaB(OH)&lt;sub&gt;4&lt;/sub&gt;/kg water. The computed electrical conductivities deviate by ca. 10% from experimental data at 298 K for the same concentration range. Based on the molecular simulations results, engineering equations are developed for shear viscosities, self-diffusivities of H&lt;sub&gt;2&lt;/sub&gt;, Na&lt;sup&gt;+&lt;/sup&gt;, and B(OH)&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;, and solubilities of H&lt;sub&gt;2&lt;/sub&gt;, which can be used to design and model NaBH&lt;sub&gt;4&lt;/sub&gt; hydrolysis reactors.&lt;/p&gt;

Topics & Concepts

Aqueous solutionChemistryMolecular dynamicsForce field (fiction)Gravimetric analysisHydrogenAtmospheric temperature rangeHydrolysisAnalytical Chemistry (journal)Physical chemistryThermodynamicsComputational chemistryPhysicsOrganic chemistryQuantum mechanicsQuantum, superfluid, helium dynamicsHydrogen Storage and MaterialsNMR spectroscopy and applications