Synthesis, crystal structure and dehydration kinetics of NaB(OH)4·2H2O

Abstract

Sodium metaborate tetrahydrate (NaB(OH) 4 ·2H 2 O) was synthesized by reaction of anhydrous borax (Na 2 O· 2B 2 O 3 ) with sodium hydroxide (NaOH) under conditions at 90 o C for 150 min. The structure was characterized by Xray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscope (SEM) and Thermogravimetric (TG) analyses. Moreover, dehydration kinetics of NaB(OH) 4 ·2H 2 O was carried out under non-isothermal conditions and the Coats-Redfern method was applied to analyze the TG data for calculation of activation energies (E a ) and pre-exponential factors (k o ) for different heating rates. It was determined that dehydration of sodium metaborate tetrahydrate occurred in five steps. According to the Coats-Redfern non-isothermal model, E a and k o were calculated as 50.89 kJ/mol and 26×10 4 min −1 for region I, 18.51 kJ/mol and 0.87×10 3 min −1 for region II, 15.72 kJ/mol and 0.52× 10 3 min −1 for region III, 4.37 kJ/mol and 0.04×10 3 min −1 for region IV and 37.42 kJ/mol and 8.56×10 3 min −1 for region V, respectively.

Properties of carbon dioxide absorption and reduction by sodium borohydride under atmospheric pressure

“…Based on the analysis results of products, the comparison of electrode potentials and the relevant references, the reaction mechanism of CO 2 with NaBH 4 in alkalinity was proposed, as shown in Eqs. (6)- (15) [19][20][21]34,37,40,41], in which the production of HCOO À was deduced as four recycling reactions of BH i (OH) 4Ài À1 (i = 4, 3, 2, 1) and HCO 2 BH j (OH) 3Àj À1 (j = 3, 2, 1, 0). In liquid phase, soluble CO 2 primarily combined with OH À to form HCO 3 À that would participate in the following cycle reactions.…”

Thermal decomposition kinetics of sodium perborate tetrahydrate to sodium metaborate by using model-fitting and model-free methods

“…The thermal dehydration kinetics of sodium metaborate tetrahydrate was studied under non-isothermal condition by using CoatsRedfern method [6]. As a result, the thermal decomposition kinetics and mechanism of sodium perborate tetrahydrate to sodium metaborate are important in various industrial applications such as detergent and sodium borohydride production.…”

“…In case of nonisothermal conditions, dα/dt in Eq. (5) is substituted with β(dα/dT)(β=(T−T o /t)) giving, (6) where β is the heating rate.…”

“…Thus, Eqs. (6) and (8) cannot be used to determine the reaction model that does not represent multi-step kinetics. According to the above, almost any reaction model, f(α) can satisfactorily obey the data at the cost of drastic variation in the Arrhenius parameters compensation effects.…”

Polyelectrolyte Multilayered Nanofilms as a Novel Approach for the Protection of Hydrogen Storage Materials

“…The XRD patterns of untreated SBH before and after storage under outdoor conditions and SBH protected by the polyelectrolyte coating are shown in Figure 3. The peaks observed on the pattern of untreated SBH after storage correspond to the crystallinity of NaB(OH) 4 (circles), showing the hydrolysis of unprotected SBH upon reaction with environmental water (31). On the other hand, it is clearly seen that SBH coated with a PE multilayer has the same peaks as those of the crystalline structure of pristine SBH (Figure 3, triangles) (32).…”