Solubility and related equilibria in the KBO₂– H₂O and KBO₂– H₂O – KOH systems

Abstract

Potassium borohydride KBH4 is an attractive chemical hydride for H2 generation and storage in portable fuel cell applications. Nevertheless, the control of the by-products, in terms of stability and solubility in aqueous solutions, is one of the limiting steps of the hydrolysis reaction of H2 release. We report here some physicochemical properties of concentrated KBO2 aqueous solutions: solubility and gravimetric density are measured as function of temperature between 10 to 80°C. The stability of hydrated metaborates KBO2.xH2O solid phases (with x = 4/3 and 4) in alkaline aqueous solutions is also evaluated at 20°C.

Solubilities, Densities, and Refractive Indices of the Ternary System (NaBO2 + KBO2 + H2O) at T = (298.15 and 323.15) K and P = 0.1 MPa

“…The comparison of solubility results of the subsystems (NaBO 2 + H 2 O) and (KBO 2 + H 2 O) in this experiment and literature at (298.15 and 323.15) K was made and is presented in Table . − Although affected by temperature and other salts, sodium metaborate has a series of crystalline hydrates corresponding to NaBO 2 , NaBO 2 ·1/3H 2 O, NaBO 2 ·2/3H 2 O, NaBO 2 ·2H 2 O, and NaBO 2 ·4H 2 O. This conclusion is consistent with our experimental results.…”

Solid–Liquid Phase Equilibria of the Ternary System (KBO2 + K2SO4 + H2O) at 288.15, 308.15 K, and 0.1 MPa

“…In order to evaluate and test the reliability of the experimental method in this work, the results for the solubilities in the binary subsystems (KBO 2 + H 2 O) and (K 2 SO 4 + H 2 O) at 288.15 and 308.15 K were compared with those in the literature, − and the results are summarized in Table . The results show that the experimental results in this work agree well with previous reports, demonstrating that our testing procedure and results are rational and reliable.…”

Density Calculations for (Na, K)BH4 + (Na, K)BO2 + (Na, K)OH + H2O Solutions Used in Hydrogen Power Engineering

“…There are not enough reference data on the densities of alkaline solutions of borohydrides and borates. ,,,, We have summarized the available experimental data (both literature and own ones) in Tables , , and .…”

“…Reference reports the gravimetric density of unsaturated aqueous solutions containing (0.06 to 0.14) molar fraction x of KBO 2 in the temperature range (10 to 80) °C. The authors have described the set of their experimental data by the square-law equation normalρ = 1.0835 − 0.0038 ( t / ° C ) + ( 3.0044 + 0.047 false( t / ° normalC false) ) x − ( 0.476 + 0.1811 false( t / ° normalC false) ) x 2 …”