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In the present work, manganese cobaltite (MnCo2O4) spinel (MCO) was synthetized by Pechini and hydrothermal method, characterized and photocatalytically evaluated toward H2 production through water splitting under visible-light irradiation. Characterization consisted in Thermogravimetry analysis (TGA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy, scattering transmission electronic microscopy, BET surface area, UV-Vis spectroscopy, cyclic voltammetry, Hall effect, and photoluminescence. The MCO were evaluated as photocatalyst using an artificial visible light lamp and monitored by gas chromatography. XRD analysis found a pure spinel phase MCO. The surface area was ∼5 m2·g−1 for the MCO synthetized by Pechini and increased to 155 m2·g−1 with the hydrothermal method with acetates as precursors. The Pechini MCO showed higher carrier mobility but the fastest recombination. Photocatalytic evaluation of the MCOs showed that the highest photocatalytic activity generated was 12 μmol H2/gcat at 8 h with the MCO obtained by hydrothermal method with the acetates.

This paper presents results of thermodynamic analysis and experimental evaluation of hydrogen production by steam reforming of ethanol (SRE) combined with CO 2 absorption using a mixture of a solid absorbent (CaO, CaO*MgO and Na 2 ZrO 3 ) and a Ni/Al 2 O 3 catalyst. Thermodynamic analysis results indicate that a maximum of 69.5% H 2 (dry basis) is feasible at 1 atm, H 2 O/C 2 H 5 OH = 6 (molar ratio) and T = 600 °C. whereas, the addition of a CO 2 absorbent at 1 atm, T = 600 °C and H 2 O/C 2 H 5 OH/Absorbent = 6:1:2.5, produced a H 2 concentration of 96.6, 94.1, and 92.2% using CaO, CaO*MgO, and Na 2 ZrO 3 , respectively. SRE experimental evaluation achieved a maximum of 60% H 2 . While combining SRE and a CO 2 absorbent exhibited a concentration of 96, 94, and 90% employing CaO, CaO*MgO, and Na 2 ZrO 3 , respectively at 1 atm, T = 600 °C, SV = 414 h −1 and H 2 O/C 2 H 5 OH/absorbent = 6:1:2.5 (molar ratio). [ABSTRACT FROM AUTHOR]

Nowadays, research aims to produce H 2 efficiently through modifying conventional processes by removing CO 2 at high temperature ( T ≥ 500 °C). The sorption enhanced reforming (SER) is an example of such a process where CO 2 capture offers significant energy savings (≈23%). Besides, feedstock to this process may include different sources of biofuels. An essential part of this new reaction system is the use of a solid CO 2 absorbent. Among absorbents stands lithium orthosilicate (Li 4 SiO 4 ) for its high absorption capacity and thermal stability. Therefore, the present research aims to study and model the kinetics of CO 2 absorption by Li 4 SiO 4 in a temperature range of 550–650 °C. Results were consistent with a first order reaction dependence with respect to CO 2 concentration. Apparent activation energy of the gas–solid reaction (22.5 kcal/mol) is approximately equal the intrinsic activation energy (28.6 kcal/mol), suggesting that the surface reaction resistance determines the overall reaction rate. [ABSTRACT FROM AUTHOR]

Biomass pyrolysis offers a fast route to produce elevated yields towards highly valued liquid products. This research aims the determination of optimal experimental conditions for a slow and low temperature pyrolysis to produce the highest yield towards condensable (CVM) and non-condensable (NCVM) volatile matter from Mexican cane bagasse and to quantify and characterize the compounds that constitute CVM and NCVM obtained. Results indicate that yield towards volatiles is strongly dependent on temperature. The highest yield was achieved at temperatures greater than 500 °C at a heating rate of 10 °C/min, residence time of 60 min and a particle size between of 420 and 840 μm. Product quantification under isothermal conditions determined that at 550 °C the NCVM, CVM and solid residue was of 26, 57 and 16%, respectively. Preliminary thermodynamic analysis of steam reforming and CO2 absorption reactions using one of the main CVM products resulted in a potential high hydrogen production yield. [ABSTRACT FROM AUTHOR]

NiWO 4 with a volumetric storage density (VSD) of 496 g L -1 was studied to evaluate its H 2 storage potential as an oxygen carrier under a chemical looping (CL) process scheme. The material was synthesized by precipitation and calcined at 950 °C for 5 hours in air. Characterization consisted in XRD, BET surface area, SEM and EDS analysis. NiWO 4 hydrogen storage reduction-oxidation evaluation was performed by TGA using 5% v H 2 /Ar and 2.2% v H 2 O/Ar at 800 °C. Global kinetics for the reduction step was studied from 730 to 870 °C using 2 to 5% v of H 2 /Ar. While oxidation kinetics was examined from 730 to 870 °C using 0.8 to 2.2% v H 2 O/Ar. A hydrogen storage multicycle stability test was performed by exposing NiWO 4 to 17 consecutive redox cycles. XRD results of the synthesized material indicate NiWO 4 as the only crystalline phase. Fully reduced material found only W and Ni species, while reoxidation led back to NiWO 4 . BET surface area of synthesized material was 4.25 m 2 g -1 . SEM results showed fresh NiWO 4 composed of non-porous large particles (1-5 μm). After reduction, the material shown a porous coral-like morphology with particles between 50 to 100 nm. EDS analysis results confirmed the compositions of the reduced (Ni + W) and fully oxidized NiWO 4 species, respectively. Oxygen carrier reaction conversions for both reduction and regeneration steps were 100%. Global kinetic studies indicate a first order reaction for the two reduction steps and during oxidation, with activation energies of 22.1, 48.4 and 53.4 kJ mol -1 for the two reduction and oxidation steps, respectively. NiWO 4 multicycle stability test shown no loss of VSD and fast reduction and oxidation kinetics under the studied conditions after seventeen consecutive redox cycles, which confirms the potential of this material with respect to current oxygen carriers reported in the literature for hydrogen storage applications., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)