No abstract

Chemical looping steam reforming (CL-SMR) thermodynamic analysis and process simulation using Fe2MnO4 as an oxygen carrier.

In the present work, zinc titanates (ZTO) as photocatalysts were synthesized, characterized, and evaluated aiming to study their photocatalytic properties for hydrogen production under visible-light irradiation and employing MeOH (methanol) and TEOA (Triethanolamine) as sacrificial agents. ZTO were synthesized by modified Pechini method. Characterization of materials consisted in TGA, XRD, TEM, EELS, BET, and UV–Vis. Surface interaction studies consisted of FT-IR spectroscopy and determination of MeOH and TEOA adsorption–desorption capacities on the ZTO by TGA. Zinc titanates were evaluated as photocatalyst for H2 production using an artificial visible light and monitored by GC. TGA results led to establish calcination temperatures of 550 °C (Zn2Ti3O8) and 700 °C (ZnTiO3) to reach their crystalline phases. XRD analysis of sample cds-ZTO found cubic Zn2Ti3O8 and traces of the ZnO crystalline phase, while p-ZTO exhibited a mixture of cubic and hexagonal ZnTiO3 crystalline phases. Surface area for cds-ZTO was 88 m2/g, while ZnTiO3 had 13 m2/g. Photocatalytic H2 production for cds-ZTO and p-ZTO using TEOA as sacrificial agent showed the highest photocatalytic activities generating 548 and 441 µmolH2/h.gcat. TEOA adsorption–desorption capacity was found superior on cds-ZTO and p-ZTO than that for MeOH on both samples.

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.

Partial oxidation (POX) by chemical looping (CL) using mixed iron oxides can be an option to current POX process. In the present research the use of FeMoO 4 , Fe 2 ZnO 4 , Fe 2 MnO 4 employed as oxygen carriers under a CL reaction scheme is proposed to overcome the current disadvantages of methane POX process. The objective of the present work is to identify potential iron-based metal oxides for the production of syngas capable regenerate at favorable conditions, while producing H 2 . A thermodynamic evaluation and process simulation of a CL-POX reaction scheme using mixed iron-oxides Reduction was carried out in a first reactor:4 + Fe 2 MO 4 = H 2 + CO + Fe + M, while a second one was devoted to oxidation of the reduced metals: Fe + M + H 2 O = Fe 2 MO 4 + H 2 , where M = Mo, Zn or Mn. Results indicate that FeMoO 4 , Fe 2 ZnO 4 and Fe 2 MnO 4 generated syngas gas at 750 °C, 730 °C and 600 °C, respectively. However, FeMoO 4 was not fully regenerated at favorable conditions. Likewise, Fe 2 ZnO 4 and Fe 2 MnO 4 were completely regenerated at 440 °C and 640 °C. Finally, Fe 2 MnO 4 shown the more favorable operating conditions among the studied oxygen carriers towards the production of Syngas.