Enhancement of hydrogen release kinetics from ethane 1,2 diamineborane (EDAB) by micronization using Supercritical Antisolvent (SAS) Precipitation

Ethane 1, 2 diamineborane (EDAB) was micronized from THF solutions using Supercritical Antisolvent (SAS) process. The influence of temperature, solute concentration and carbon dioxide fraction on the final properties of EDAB particles was studied. By SAS micronization, the original prismatic EDAB particles of about 400 µm with a crystallite size of 100 nm were converted into microspheres of less than 2 µm with a crystallite size of 50 nm. This reduction in the particle and grain sizes resulted in an improvement in thermal properties. The kinetics of release of hydrogen by thermolysis at 100ºC was also significantly enhanced due to the reduction in the diffusion length, reducing the time needed for the decomposition of the hydride by a factor of six. Moreover, a suppression of induction time was obtained by destabilization of the hydride after treatment. XRD and FTIR analyses showed that no chemical decomposition and no variation of the crystalline structure took place by SAS processing.2018-07-15Spanish Ministry of Economy and Competitiveness project ENE2014-53459-

Experimental determination of (p, ρ, T) data for binary mixtures of methane and helium

Innovación EducativaThe basis for the development and evaluation of equations of state for mixtures is experimental data for several thermodynamic properties. The quality and the availability of experimental data limit the achievable accuracy of the equation. Referring to the fundamentals of GERG-2008 wide-range equation of state, no suitable data were available for many mixtures containing secondary natural gas components. This work provides accurate experimental (p, ρ, T) data for two binary mixtures of methane with helium (0.95 (amount-of-substance fraction) CH4 + 0.05 He and 0.90 CH4 + 0.10 He). Density measurements were performed at temperatures between 250 K and 400 K and pressures up to 20 MPa by using a single-sinker densimeter with magnetic suspension coupling. Experimental data were compared with the corresponding densities calculated from the GERG-2008 and the AGA8-DC92 equations of state. Deviations from GERG-2008 were found within a 2 % band for the (0.95 CH4 + 0.05 He) mixture but exceeded the 3 % limit for the (0.95 CH4 + 0.05 He) mixture. The highest deviations were observed at 250 K and pressures between 17 and 19 MPa. Values calculated from AGA8-DC92, however, deviated from the experimental data by only 0.1 % at high pressures and exceeded the 0.2 % limit only at temperatures of 300 K and above, for the (0.90 CH4 + 0.10 He) mixture.MEC ENE2013-47812-RJunta de Castilla y León Regional VA391A12-1European Commission's ENG5

Improvement of the kinetics of hydrogen release from ammonia borane confined in silica aerogel

Ammonia borane is a promising hydrogen storage material due to its high gravimetric capacity (19.6 % wt), but it also presents limitations such as a slow hydrogen release with a long induction time, a difficult regeneration, or the formation of foams and gaseous by-products during thermolysis. Previous studies have shown that by nanoconfinement of ammonia borane within a porous support some of these limitations can be overcome due to the reduction and stabilization of ammonia borane particle size. However, this effect was only observed with moderate ammonia borane loadings, as with higher loadings the pores of the support became obstructed. In this work, silica aerogels produced by CO2 drying, with pore volumes up to 2 cm3/g, have been used to confine ammonia borane. The influence of the amount of ammonia borane loaded on the aerogel support on the thermal and structural properties of the material has been analyzed. It has been found that more than 60 wt% of ammonia borane can be effectively stored in the pores of the aerogel support. The resulting material shows faster hydrogen release kinetics by thermolysis at 80ºC, due to a significant reduction in the mea size of ammonia borane after confinement and the participation of SiOH and SiOSi groups of silica aerogel in the decomposition mechanism.2018-09-20Spanish Ministry of Economy and Competitiveness project ENE2011-2454

Determination of the force transmission error in a single-sinker magnetic suspension densimeter due to the fluid-specific effect and its correction for use with gas mixtures containing oxygen

Producción CientíficaDensity measurements from single-sinker magnetic suspension densimeters need to be corrected to compensate for the magnetic effects of the measuring cell materials and the fluid on the coupling transmission system. While the magnetic effect of the densimeter materials can be easily determined, the fluid effect requires the calculation of an apparatus-specific constant, ερ. In this work, the apparatus-specific constant of the single-sinker magnetic suspension densimeter at the University of Valladolid has been determined by using two alternative methods. The first method, which uses density data for the same fluid and conditions and different sinkers, yielded a value of ερ = 4.6·10-5. The second method, obtained from measurements with pure oxygen, yielded a value of ερ = 8.822·10-5. The second value is considered as more reliable, as the first method presents inherent limitations in this case.Ministerio de Economía, Industria y Competitividad project ENE2017-88474-RJunta de Castilla y León project VA280P1

Density and viscosity measurements of aqueous amines at high pressures: DEA-water, DMAE-water and TEA-water mixtures

Producción CientíficaIn this paper, density and viscosity measurements at pressures up to 140 MPa are presented in a temperatura range from (293.15 to 393.15) K for diethanolamine (DEA) + water, triethanolamine (TEA) + wáter and 2-dimethylaminoethanol (DMAE) + water in amine weight concentrations from 10% to 40%. Densities were measured using a vibrating tube densimeter (Anton Paar DMA HPM) with an expanded uncertainty (k = 2) less than ±0.7 kg m 3. Viscosity measurements were obtained using a falling body viscometer which was calibrated with water and dodecane. The viscosity expanded uncertainty (k = 2) ranges from ±2.5% for the highest viscosity to ±3.2% for the lowest.2019/05/05Regional Government of Castilla y León through the Project VA295U1

Heat capacities and acoustic virial coefficients for a synthetic coal mine methane mixture by speed of sound measurements at T = (273.16 and 250.00) K.

Measurements of speed of sound for a synthetic coal mine methane mixture of ten components are reported. Data were obtained using a spherical resonator for two isotherms T = (273.16 and 250.00) K and pressures up to 8 MPa. The uncertainty study is detailed and the total uncertainty of the speed of sound is no worse than 0.01%. Heat capacities and acoustic virial coefficients were obtained through said measurements. Results are compared with the GERG-2008 equation of state.MEC ENE2013-47812- RRegional Government of Castilla y León, project VA391A12-1European Metrology Research Programme ENG5

Speeds of sound for (CH4 + He) mixtures from p = (0.5 to 20) MPa at T = (273.16 to 375) K

Producción CientíficaThis work aims to provide accurate and wide-ranging experimental new speed of sound data w(p,T) of two binary (CH4 + He) mixtures at a nominal helium content of 5 % and 10 % at pressures p = (0.5 up to 20) MPa and temperatures T = (273.16, 300, 325, 350 and 375) K. For this purpose, the most accurate technique for determining speed of sound in gas phase has been used: the spherical acoustic resonator. Speed of sound is determined with an overall relative expanded (k = 2) uncertainty of 230 parts in 106 and compared to reference models for multicomponent natural gas-like mixtures: AGA8-DC92 and GERG-2008 equations of state. Relative deviations of experimental data from model estimations are outside the experimental uncertainty limit, although all points are mostly within the AGA uncertainty of 0.2 % and GERG uncertainty of 0.5 % and worsen as the helium content increases. Absolute average deviations are better than 0.45 % for GERG and below 0.14 % for AGA models in (0.95 CH4 + 0.05 He) mixture and below 0.83 % for GERG and within 0.22 % for AGA equations in (0.90 CH4 + 0.10 He) mixture.Junta de Castilla y León (project VA280P18)Ministerio de Economía, Industria y Competitividad (project ENE2017-88474-R

Phase Equilibrium Properties of Binary and Ternary Mixtures Containing Dibutyl Ether, Cyclohexane, and Heptane or 1-Hexene at T = 313.15 K

New experimental isothermal P, x, y data for the ternary systems dibutyl ether + cyclohexane + heptane and dibutyl ether + cyclohexane + 1-hexene and for the binary systems dibutyl ether + 1-hexene and dibutyl ether + heptane at 313.15 K are reported. Data reduction by Barker’s method provides correlations for GE, using the Margules equation for the binary systems and the Wohl expansion for the ternary systems. Wilson, NRTL, and UNIQUAC models have been applied successfully to both of the binary and ternary mixtures presented here.Ministerio de Ciencia y Tecnología, Dirección General de Investigación (PPQ-2002-04414-C02-01

Speed of sound for three binary (CH4 + H2) mixtures from p = (0.5 up to 20) MPa at T = (273.16 to 375) K

Producción CientíficaSpeed of sound is one of the thermodynamic properties that can be measured with least uncertainty and is of great interest in developing equations of state. Moreover, accurate models are needed by the H2 industry to design the transport and storage stages of hydrogen blends in the natural gas network. This research aims to provide accurate data for (CH4 + H2) mixtures of nominal (5, 10, and 50) mol-% of hydrogen, in the p = (0.5 up to 20) MPa pressure range and with temperatures T = (273.16, 300, 325, 350, and 375) K. Using an acoustic spherical resonator, speed of sound was determined with an overall relative expanded (k = 2) uncertainty of 220 parts in 106 (0.022 %). Data were compared to reference equations of state for natural gas-like mixtures, such as AGA8-DC92 and GERG-2008. Average absolute deviations below 0.095% and percentage deviations between 0.029% and up to 0.30%, respectively, were obtained. Additionally, results were fitted to the acoustic virial equation of state and adiabatic coefficients, molar isochoric heat capacities and molar isobaric heat capacities as perfect-gas, together with second and third acoustic virial coefficients, and were estimated. Density second virial coefficients were also obtained.Ministerio de Economía, Industria y Competitividad project ENE2017-88474-RJunta de Castilla y León VA280P1

Speed of sound data and acoustic virial coefficients of two binary (N2 + H2) mixtures at temperatures between (260 and 350) K and at pressures between (0.5 and 20) MPa

Producción CientíficaThis work aims to address the technical concerns related to the thermodynamic characterization of gas mixtures blended with hydrogen for the implementation of hydrogen as a new energy vector. For this purpose, new experimental speed of sound measurements have been done in gaseous and supercritical phases of two binary mixtures of nitrogen and hydrogen using the most accurate technique available, i.e., the spherical acoustic resonator, yielding an experimental expanded (k = 2) uncertainty of only 220 parts in 106 (0.022%). The measurements cover the pressure range between (0.5 and 20) MPa, the temperature range between (260 and 350) K, and the composition range with a nominal mole percentage of hydrogen of (5 and 10) mol%, respectively. From the speed of sound data sets, thermophysical properties that are relevant for the characterization of the mixture, namely the second βa and third γa acoustic virial coefficients, are derived. These results are thoroughly compared and discussed with the established reference mixture models valid for mixtures of nitrogen and hydrogen, such as the AGA8-DC92 EoS, the GERG-2008 EoS, and the recently developed adaptation of the GERG-2008 EoS, here denoted GERG-H2_improved EoS. Special attention has been given to the effect of hydrogen concentration on those properties, showing that only the GERG-H2_improved EoS is consistent with the data sets within the experimental uncertainty in most measuring conditions.Ministerio de Ciencia, Innovación y Universidades - Fondo Europeo de Desarrollo Regional (project ENE2017-88474-R)Ministerio de Ciencia, Innovación y Universidades (fellowship BEAGAL18/00259)Junta de Castilla y León - Fondo Europeo de Desarrollo Regional (project VA280P18