Novel core-shell-like Ni-supported hierarchical beta zeolite catalysts on bioethanol steam reforming

Hierarchical-Beta zeolites have been hydrothermally synthesized by adding a new gemini organic surfactant. The used gemini surfactant play the role of a “pore-forming agents” on the mesoscale, on the same time, providing alkaline environment for the system. With this hierarchical Beta zeolite as the core support, we successfully prepared a shell layer of Ni-containing (22 wt%) petal-like core-shell-like catalyst and applied it to bioethanol steam reforming. At the reaction temperature of 350 °C–550 °C, the conversion rate of ethanol and the selectivity of hydrogen were always above 85% and 70%. After reaction of 100 h on stream at 400 °C, there were not obvious inactivation could be observed on NiNPs/OH-MBeta catalyst.     

Alkali catalyzed liquefaction of corncob in supercritical ethanol–water

Corncob liquefaction in supercritical ethanol–water was performed with and without the addition of an alkali catalyst by direct addition or biomass impregnation in a 250-cm³ batch reactor. The effects of temperature, solvent and alkali addition on the biomass conversion level and oil yield were investigated to find the optimum condition. For non-catalytic liquefaction using a 1:1 (v/v) ethanol: water ratio, a maximum oil yield and conversion level of 49.0% and 93.4%, respectively, were obtained at 340 °C. For alkali catalytic liquefaction, the oil yield with KOH addition (57.5%) was higher than that from KOH-impregnated corncob liquefaction (43.3%). The oil from liquefaction with KOH addition had higher heating value (26.7–35.3 MJ kg⁻¹) than the corncob (19.1 MJ kg⁻¹). The dominant components of the obtained oil were found by GC/MS analysis to be aldehyde, ester, phenol derivatives and aromatic compounds.     

Redox flow cells for energy conversion

Energy storage technologies provide an alternative solution to the problem of balancing power generation and power consumption. Redox flow cells are designed to convert and store electrical energy into chemical energy and release it in a controlled fashion when required. Many redox couples and cell designs have being evaluated. In this paper, redox flow systems are compared in the light of characteristics such as open circuit potential, power density, energy efficiency and charge-discharge behaviour. The key advantages and disadvantages of redox flow cells are considered while areas for further research are highlighted.     

Submerged membrane adsorption hybrid system (SMAHS): process control and optimization of operating parameters

This study is to investigate the effect of operating parameters of submerged membrane adsorption hybrid system (SMAHS) such as preadsorption and powdered activated carbon requirement, aeration, filtration flux; There is an optimum value for each of the operating parameters and they are specific to the wastewater used. The duration and frequency of backwashing are vital parameters for successful long-term operation of a membrane system. The backwash duration and frequency required to remove the reversible component of the foulant layer increased with time during the operation of membrane and is not fixed. A new methodology introduced in this study to decide the appropriate duration and frequency of backwash based transmembrane pressure during the membrane operation. This method led to significant saving on the amount of backwash water and energy requirement.     

Hydrogen storage in destabilized chemical systems

We describe approaches for modifying the thermodynamics and kinetics of hydrogen sorption reactions in light-metal hydrides. Thermodynamic destabilization is achieved using additives that form new compounds during dehydrogenation. This lowers the enthalpy and increases the equilibrium pressure. We review current research in this area, emphasizing destabilization reactions involving LiBH₄. We also describe the use of nano-engineering approaches for reducing diffusion distances and increasing surface area, thereby increasing the hydrogen exchange rate. We focus on improving reaction rates by incorporating metal hydrides into nanoporous scaffolds.     

Monodisperse rutheniumcopper alloy nanoparticles decorated on reduced graphene oxide for dehydrogenation of DMAB

In this study, we report a superior dehydrogenation catalyst for dimethylamine borane, which exhibited one of the best catalytic activities. The newly formed catalyst system contains well dispersed ruthenium-copper nanomaterials on reduced graphene oxide (3.86 ± 0.47 nm), which was prepared by using the ultrasonic double reduction technique. The characterization of monodisperse ruthenium-copper alloy nanoparticles was performed using some advanced analytical methods such as TEM, HRTEM, XPS, Raman spectroscopic analysis. The experiments results revealed that the monodisperse ruthenium-copper alloy catalyst (RuCu@rGO) has one of the highest catalytic activity compared to previous studies, having a high turnover frequency value (256.70 h⁻¹). The detailed kinetic parameters such as activation energy, enthalpy, and entropy values were also calculated for the dehydrogenation of dimethylamine borane at room temperature. Also, the results showed that the monodisperse RuCu@rGO catalyst has high durability and reusability as retained its 81% initial catalytic activity even after 4th runs for the dehydrogenation of dimethylamine borane.     

Coal char gasification for co-production of fuel gas and methane decomposition catalysts

Partial gasification of coal char was conducted with addition of metal oxides for co-production of fuel gas and methane decomposition catalysts. Effect of the metal composition (Ni, Co and Fe based mono- or bi-metals) was investigated on the fuel gas production and the resultant catalyst surface and textural properties, morphology and performance in catalytic methane decomposition (CMD). Besides H₂-rich fuel gas production (the combustion energy up to 11.03–23.42 MJ/kg_char) from the gasification, the gasification residue can directly serve as the effective and efficient catalyst for CMD. The Fe and Fe–Co composite oxides were found to be better among the mono- and bi-metallic oxides for the fuel gas production during the gasification, respectively. The Ni-based mono-/bi-metallic catalysts could display high and stable methane conversion (up to 80%) during the 600-min CMD test at 850 °C. Promotional role of the second metal in CMD was discussed on the carbon diffusion, metal mobility and reducibility, formation and growth of the deposited carbons. The formed carbon morphology after CMD was analyzed based on the Kirkendall effect and Tammann temperature and further correlated to the potential catalyst deactivation.     

Synthesis based structural and optical behavior of anatase TiO2 nanoparticles

The effect of synthesis method on optical and photoconducting properties of titanium dioxide (TiO₂) nanoparticles has been investigated. Sol–gel and co-precipitation methods have been employed to prepare pure anatase phased TiO₂ nanoparticles calcinated at different temperatures below 500 °C. The optimized value of average crystallite size is within the range of 19−21 nm for a common calcination temperature of 400 °C for both the methods. The redshift in optical band gap of 0.9 eV has been observed for the sample synthesized by co-precipitation method with respect to the sol–gel method. The photoluminescence spectrum exhibits broad visible emission in both routes of synthesis while photoconductivity shows fast growth and decay of photocurrent in TiO₂ prepared by co-precipitation method as compared to TiO₂ prepared by the sol–gel method under visible illumination. Crystal structure based Rietveld refinement of X-ray diffraction data, scanning electron microscopy as well as photoluminescence and photoconductivity measurements were performed to characterize nanocrystalline anatase TiO₂.     

F−-Eu3+ charge transfer energy and local crystal environment in Eu3+ doped calcium fluoride

A series of CaF₂:xEu³⁺ (x = 0.01–0.05) phosphors were synthesized by coprecipitation and high temperature solid-state method. Three different F^--Eu³⁺ charge transfer (CT) bands in CaF₂:xEu³⁺ (x = 0.01–0.05) were detected through the PL spectra. Three local crystal environments (deformed O_h octahedron, C_3V, C_4V) were proposed in Eu³⁺ doped CaF₂. The broad peak at 277 nm is F^- → Eu³⁺ CT peak, in which Eu³⁺ ions located deformed O_h octahedron sites, the broad peak at 312 nm is due to Eu³⁺ ions situating at C_4v sites, also, Eu³⁺ ions with C_3v sites can make the F^- → Eu³⁺ CT produce a 38-nm redshift to 315 nm. Density functional theory (DFT) was performed to calculate the energy band gap(Eg) according to the three models. The calculation results consist with the experiment. The excitation peaks can be tuned in the same host through changing the local structure of Eu³⁺.     

Co2 +-exchanged MOR and 5A zeolites as efficient solid catalysts for the epoxidation of styrene with air

Selective oxidation of alkenes with air to corresponding epoxides was performed over simple ion-exchanged Co-MOR and Co-5A. Among all transition metal ions-exchanged M-zeolites, both Co-MOR and Co-5A exhibited the highest activity at 363 K. Notably, for the epoxidation of styrene, α-pinene, α-methyl styrene and cyclooctene, Co-MOR obtained higher conversions than Co-5A, in agreement with the difference of pore sizes of both zeolitic materials. Recycling and control tests showed high durability of Co-MOR as a heterogeneous catalyst in our catalytic system.