MgAl2O4-supported Ni materials are highly active and cost-effective CO2 conversion catalysts, yet their oxidation by CO2 remains dubious. Herein, NiO/MgAl2O4, prepared via colloidal synthesis (10 wt % Ni) to limit size distribution, or wet impregnation (5, 10, 20, and 40 wt % Ni), and bare, i.e., unsupported, NiO are examined in H2 reduction and CO2 oxidation, using thermal conductivity detector-based measurements and in situ quick X-ray absorption spectroscopy, analyzed via multivariate curve resolution-alternating least-squares. Ni reoxidation does not occur for bare Ni but is observed solely on supported materials. Only samples with the smallest particle sizes get fully reoxidized. The Ni-MgAl2O4 interface, exhibiting metal–support interactions, activates CO2 and channels oxygen into the reduced lattice. Oxygen diffuses inward, away from the interface, oxidizing Ni entirely or partially, depending on the particle size in the applied oxidation time frame. This work provides evidence for Ni oxidation by CO2 and explores the conditions of its occurrence and the importance of metal–support effects.

zanardini macroalgae biomass composition and its potential for biofuel production, Bioresource Technology (2014), doi: http://dx.doi.org/10.1016/j.biortech. 2014.10.141 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. 1 Characterization of AbstractNizimuddinia zanardini macroalgae, harvested from Persian Gulf, was chemically characterized and employed for the production of ethanol, seaweed extract, alginic acid, and biogas. In order to improve the products yields, the biomass was pretreated with dilute sulfuric acid and hot water. The pretreated and untreated biomasses were subjected to enzymatic hydrolysis by cellulase (15 FPU/g) and β-glucosidase (30 IU/g). Hydrolysis yield of glucan was 29.8, 82.5, and 72.7 g/kg for the untreated, hot-water pretreated, and acid pretreated biomass, respectively. Anaerobic fermentation of hydrolysates by S. cerevisiae resulted in the maximum ethanol yield of 34.6 g per kg of the dried biomass. A seaweed extract containing mannitol and a solid residue containing alginic acid were recovered as the main byproducts of the ethanol production. On the other hand, the biogas yield from the biomass was increased from 170 to 200 m 3 per ton of dried algae biomass by hot water pretreatment.

Modulation excitation (ME) with phase-sensitive detection (PSD) is an emerging strategy to selectively characterize catalytic species that actively participate in a chemical reaction. The commonly applied square-wave (SW) modulations, however, contain a limited frequency content, impeding rigorous kinetic analysis of short-lived reaction intermediates through PSD analysis by considering higher-order harmonics. To overcome this bottleneck, a “modulation engineering” approach is designed, whereby stimulation shapes with a complementary frequency content are superposed onto a base modulation, thus subjecting the system to a more complex frequency pattern in a single experiment. Building on practical and mathematical considerations, this design scheme’s feasibility is demonstrated using a superposition of SW and rectangular wave stimulations, applied to H2/CO2 concentration modulation-excitation X-ray absorption spectroscopy of a Ni/MgFeAlO4 methane dry reforming (DRM) catalyst at the Fe and Ni K edge. Under redox conditions, PSD evidences Ni ↔ Ni2+ and Fe0 ↔ Fe2+ ↔ Fe3+ redox events, wherein Fe2+ ↔ Fe3+ transitions exhibit faster kinetics, adding insight into this material’s redox functionalities under DRM conditions. This approach is extendable to other ME-based characterization techniques and provides a general, time-efficient framework to expand the transient kinetic insights that can be obtained for catalytic systems through ME with PSD.

Abstract:The marine macro-alga Nizimuddinia zanardini was harvested from Persian Gulf to assess its biomass for fermentable sugar production. Hydrolysis of the macro-alga was investigated in two stages to evaluate the conversion of cellulose and hemicelluloses in biomass to corresponding monomeric sugars. The biomass was first subjected to dilute sulfuric acid pretreatments at 121 °C and then to enzymatic saccharification (45°C, pH 4.8) at different retention times. The results showed the ability of the first stage hydrolysis in depolymerization of xylan to xylose with a maximum yield of 64% (based on total xylose content) at 7% (w/w) acid concentration for 60 min. However, the yield of glucose from glucan was relatively low in the acid hydrolysis with a maximum of 14.4% (based on total glucan content) at 7% (w/w) acid concentration for 60 min. Under these conditions, no hydroxymethyl furfural (HMF) produced. Formation of furfural depended on the retention time and acid concentration, whereas the concentration of acetic acid was almost constant at retention times higher than 45 min and acid concentration of 7 %.The solid residuals were then subjected to enzymatic hydrolysis. The maximum yield of glucose from the macro-alga by enzymatic saccharification (45°C, pH 4.8, 24 h), using cellulase and β-glucosidase, was 70.2 g/kg (70.2% yield based on total glucan content).

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