Mechanisms of synthesis gas production via thermochemical cycles over La0·3Sr0·7Co0·7Fe0·3O3

La_0·3Sr_0·7Co_0·7Fe_0·3O₃ (LSCF3773) was chosen as an oxygen carrier material for synthesis gas production and synthesized using ethylene-diamine-tetra-acetic acid (EDTA) citrate-complexing method. LSCF exhibited a pure cubic structure where 110 and 100 plane diffractions were active for CO₂ splitting, while 111 was more favored by H₂O splitting. Overall oxygen storage capacity (OSC) of LSCF was 4072 μmol/g_cat. During the reduction process, regular cations (Co⁴⁺, Fe⁴⁺), polaron cations (Co³⁺, Fe³⁺) and localized cations (Co²⁺, Fe²⁺) were achieved when the LSCF was reduced at 500, 700 and 900 °C, respectively. The strength of the active sites depended on reduction temperatures. An increase in oxidation temperature enhanced H₂ production at temperature ranging from 500 °C to 700 °C while effected CO production at 900 °C. H₂O and CO₂ was competitively split during the oxidation step, especially at 700 °C. The activation energy of each reaction was ordered as; CO₂ splitting > H₂O splitting > CO₂ adsorption, supporting the above evidence where H₂ and CO production were found to increase when the operating temperature was increased.     

Porous cobalt spheres for high temperature gradient magnetically assisted fluidized beds

Porous metallic cobalt spheres have been prepared as high temperature capable media for employment in gradient magnetically assisted fluidization and filtration technologies. Cobalt impregnated alginate beads are first formed by extrusion of an aqueous suspension of Co3O4 into a Co(II) chloride solution. The organic polymer is thermally decomposed yielding cobalt oxide spheres, followed by reduction to the metallic state, and densification. Cobalt beads have been produced with porosities ranging between 10 and 50%, depending upon sintering conditions. The product media have been characterized by scanning electron microscopy (SEM), nitrogen adsorption porosimetry, and vibrating sample magnetometry.     

Application of a micro-channel reactor for process intensification in high purity syngas production via H2O/CO2 co-splitting

A stainless steel micro-channel reactor was tailor-made to an in house-design for process intensification propose. The reactor was used for a two-step thermochemical cycles of H₂O and CO₂ co-splitting reaction, in the presence of La_0.3Sr_0.7Co_0.7Fe_0.3O₃ (LSCF). LSCF was coated inside the reactor using wash-coat technique. Oxygen storage capacity of LSCF was determined at 4465 μmol/g, using H₂-TPR technique. H₂O-TPSR and CO₂-TPSR results suggested that a formation of surface hydroxyl group was the cause of H₂O splitting favorable behavior of LSCF. Optimal operating reduction/oxidation temperature was found at 700 °C, giving 2266 μmol/g of H₂, 705 μmol/g of CO, and 67% of solid conversion, when the H₂O and CO₂ ratio was 1 to 1, and WSHV was 186,000 mL/g.h. Activation energy of H₂O spitting and CO₂ splitting was estimated at 87.33 kJ/mol, and 102.85 kJ/mol The pre-exponential factor of H2O splitting and CO2 splitting was 595.24 s^?1 and 698.79 s^?1, respectively.     

Detailed microkinetic modelling of syngas to hydrocarbons via Fischer Tropsch synthesis over cobalt catalyst

Fuels production from syngas via Fischer Tropsch synthesis (FTs) is an alternative technology for clean energy production. The microkinetic model is a promising approach for gaining insight into FTs activity. In this study, a systematic microkinetic model was proposed to develop a process for cobalt-catalyzed FTs. All possible elementary reactions based on the carbide mechanism and characteristics of catalyst sites were considered in the kinetic model. The effects of the reaction rate constant, reaction pathways, and H₂ to CO ratio were represented by a kinetic parameter, reaction path, and operating parameter, respectively. The model could accurately predict product distribution trends, with an R² value and mean absolute relative residuals percentage of 0.91–0.93 and 5–43%, respectively, in comparison with experimental data. Hydrogen utilization was predicted and analyzed. High model accuracy was achieved, with a 10^?10–10^?3% error in the material balance.     

Fabrication using sequence wet-chemical coating and electrochemical performance of Ni–Fe-foam-supported solid oxide electrolysis cell for hydrogen production from steam

Ni–Fe-alloy-foam supported solid oxide electrolysis cell with an arrangement of nickle and Sc_0.1Ce_0.005Gd_0.005Zr_0.89O₂ (Ni-SCGZ) cathode, SCGZ electrolyte and Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF) anode is successfully fabricated by the sequence wet-chemical coating. The multi-layer cathode with a gradient of thermal expansion coefficient (TEC) is deposited on the alloy-foam support. Two-step firing processes are applied including cathode pre-firing (1373 K, 2 h) and electrolyte sintering (1623 K, 4 h) using slow heating rate enhanced with compressive loading. The fabricated cell shows current density of ?0.95 Acm^?2 at 1.1 V with H₂O:H₂ = 70:30 and 1073 K, providing hydrogen production rate at 4.95 × 10^?6 mol s^?1. However, performance degradation was observed with the rate of 0.08 V h^?1, which can be ascribed to the delamination of BSCF anode under operating at high current density.     

Characterization of tar content in the syngas produced in a downdraft type fixed bed gasification system from dried sewage sludge

Tar yields in the syngas produced in a pilot-scale downdraft type fixed bed gasification system from dried sewage sludge have been quantified and characterized to identify the effect of equivalence ratio (ER of 0.29-0.36). The increase of ER resulted in higher temperature of oxidation zone because air promoted the combustion reaction. High ER and high temperature also enhanced cracking and combustion of tar. Lower tar mass was observed while increasing ER. The change in tar composition with the change of ER was also observed by using the size exclusion chromatography (SEC). The SEC results showed that heavier molecular tar (in the molecular weight range of 300-500 u) formed whereas lighter molecular tar decreased under the higher ER conditions. Tar removal performances of the gas cleaning system (the venturi scrubbers and the sawdust adsorbers) were also investigated. The tar removal efficiency of the gas cleaning system depended on gasification conditions, tar components and the amount of tar. Tar content in the syngas was reduced to 26-53% and 14-36% (by weight) at the exit of the scrubbers and sawdust adsorbers, respectively. By the action of this gas cleaning system, about 44% of light aromatic hydrocarbon tar was removed while no light PAH tar was detected at the exit of the gas cleaning system.     

The use of an ultra-low viscosity medium (VCD/HXSA) in the rapid embedding of plant cells for electron microscopy

The VCD/HXSA ultra-low viscosity medium is characterized by a viscosity of only 20 cps at 298 K. This is extremely useful for rapid embedding schedules and facilitates cutting large sections even from difficult materials. The suitability of this medium for ultrastructural studies is tested with plant specimens ranging from soft, highly vacuolated parenchymatous tissue to hard thick-walled cells impregnated with a variety of substances or covered with mucilage. The results, when compared with those from similar materials infiltrated with Spurr's and Epon embedding media, show that the general preservation of the cellular structure is comparable for all the three media tested. In addition, embeddment in VCA/HXSA medium results in better preservation of some vacuolar features and in the reduction of plasmolysis.     

Synthesis and application of some new oxazole derivatives as antimicrobial agents

5-(p-Acetylphenyl)-2-phenyloxazole ( I ) was condensed with aromatic aldehydes to furnish chalcones 2a-e . Cyclocondensation of 2a-e with hydrazine hydrate and with phenyl hydrazine led to the formation of pyrazoline derivatives 3a-e and 4a-e respectively. Similarly, 2a was interacted with hydroxylamine to give isoxazoline ( 5 ). On the other hand, condensation of 1 with phenyl hydrazine yielded hydrazone 6 which on treatment with Vilsmeier reagent (DMF/POCl₃) gives 5-[p-(4-formyl-1-phenylpyrazol-3-yl)phenyl]-2-phenyloxazole ( 7 ). Also, a few derivatives of 7 have been prepared. Moreover, all compounds were screened for their antimicrobial activity against some strains of bacteria and fungi.