Preparation of strontium-based fibers via electrospinning technique

The Sr-based fiber was prepared by electrospinning process. The effect of electric field, precursor viscosity, and calcination temperature (T_cal) was investigated at required conditions. Then the Sr-based fiber was characterized by TGA, nitrogen adsorption, SEM, TEM, and XRD to elucidate thermal transition, specific surface area, morphology, crystal structure, and crystalline phase of the samples, respectively. The result showed that the smooth fiber sample could be spun at electric field of 1.5 kV cm^?1 with the suitable viscosity of ca. 5 Pa s. Finally the crystalline phase could be controlled by properly adjusting T_cal, i.e. when the T_cal was risen from 400 to 1000 °C, the crystalline phase was transformed from SrCO₃ to Sr(OH)₂H₂O, and eventually to SrO.     

A study of various zeolites and CuFe2O4 spinel composite catalysts in steam reforming and hydrolysis of dimethyl ether

The catalytic performance of the composite catalysts of CuFe₂O₄ spinel and various zeolites for steam reforming and hydrolysis of dimethyl ether (DME SR and DME HYD) was investigated. The catalytic activity for DME SR and DME HYD was affected by the type of zeolites and the durability of the CuFe₂O₄ spinel catalysts composed of various zeolites was lower than those composed of alumina as solid acids. Based on several characterizations, the difference of types of zeolite led to the formation of various carbonaceous species on the catalysts during DME SR and DME HYD. The deactivation due to the coke formation was suppressed by the pre-heat treatments in air as a result of the decreasing acid strength. This high durability with heat treatment was obvious for the composite catalyst of CuFe₂O₄ and ZSM-5 (MFI) type zeolite in DME SR. In contrast, the heat treatment did not enhance the durability of the ferrierite (FER) type zeolite composite catalyst.     

Synthesis,structural characterization,and magnetic property of nanostructured ferrite spinel oxides (AFe2O4, A = Co,Ni and Zn)

Nanostructured ferrite spinels AFe₂O₄ (A = Co, Ni, Zn) were successfully synthesized via a co-precipitation method using oxalate salt as a precursor in an anionic surfactant system in combination with a simple calcination process. High crystallinity samples of nanoparticle spinels in a grain size range of 15–100 nm were obtained by varying the calcination temperature (300–700 °C) and time (1–5 h). Their pore sizes were controlled in a range of 3 nm up to a hundred nm by tailoring the calcination conditions. Raising the calcination temperature was found to decrease the Brunauer–Emmett–Teller (BET) surface area, and broaden the pore structure due to enhanced crystal growth and agglomeration of interparticles of spinels. Transmission electron microscopy (TEM) images of ferrite spinels calcined at 300 °C showed mesoporous structures with narrow pore size distribution, and the maximum BET surface area of CoFe₂O₄, NiFe₂O₄ and ZnFe₂O₄ were found at 201 (Co), 315 (Ni), and 273 (Zn) m² g⁻¹, respectively. The magnetic hysteresis loops of the ferrite spinels at room temperature demonstrated ferromagnetism in CoFe₂O₄, superparamagnetism–ferromagnetism in NiFe₂O₄, and paramagnetism in ZnFe₂O₄. The highest saturation magnetization (M_s), remanent magnetization (M_r), and coercivity (H_c) were obtained from high crystallinity spinels calcined at 700 °C. Nanostructured AFe₂O₄ with high surface area and mesoporosity promises potentials as novel magnetic catalysts.     

Improved hydrophilicity of zinc oxide-incorporated layer-by-layer polyelectrolyte film fabricated by dip coating method

ZnO nanoparticles suspended in poly(acrylic acid) (PAA) were deposited onto layer-by-layer (LBL) polyelectrolyte (PET) films fabricated from poly(allylamine hydrochloride) (PAH) and PAA by dip coating method. Effect of etching time and concentration of ZnO suspension on hydrophilicity of the LBL-PET films before and after UV irradiation was examined using water contact angle measurement. 2.0 M PAH/PAA solutions with a dipping speed of 3.0 cm/min provided stable LBL-PET films with thickness sufficient for HCl etching. Glass substrates with the etched LBL-PET film dipped into 0.2 wt.% ZnO suspension exhibited the contact angle of 10° after irradiated by UV for 60 min.     

Flame sprayed tri-metallic Pt–Sn–X/Al2O3 catalysts (X = Ce,Zn, and K) for propane dehydration

Trimetallic nanocrystalline Pt–Sn–X/Al₂O₃ catalysts (X = Ce, Zn, and K) consisting of 0.3 wt.% Pt, 1 wt.% Sn, and 0.5 wt.% X have been prepared by one-step flame spray pyrolysis (FSP). As shown by the X-ray diffraction (XRD) and the transmission electron microscopy (TEM) results, the as-synthesized FSP-made catalysts were consisted of single-crystalline γ-alumina particles with average primary particle sizes 8 to 9 nm. The N₂ physisorption results revealed that all the catalysts contained only the macropore structure. The catalytic properties of the FSP-made catalysts were investigated in the dehydration of propane. Addition of Ce during FSP synthesis resulted in higher Pt dispersion as well as improved catalytic activity and stability than the non-promoted Pt–Sn/Al₂O₃. An opposite trend was found with the ones doped with Zn and K in which high surface coverage of Zn and K resulted in a significant loss of Pt active sites. The mechanism for the formation of the trimetallic nanoparticles during one-step FSP synthesis appeared to depend strongly on the differences in the vapor pressure of the metals and the alumina support in flame.     

Crystal structure and surface species of CuFe2O4 spinel catalysts in steam reforming of dimethyl ether

The application of catalytic ozonation processes for the decolourisation and mineralisation of coloured aqueous solutions was studied. One acid azo dye, CI Acid Blue 113, and two reactive dyes, CI Reactive Yellow 3 and CI Reactive Blue 5, with azo and anthraquinone chromophores, respectively, were used as representative textile dyes. The catalytic activities of activated carbon, cerium oxide and a ceria-activated carbon composite were evaluated in the removal of the selected dyes. In all cases, with an initial dye concentration of 50 mg/L, a complete decolourisation was achieved by single ozonation in short reaction times (less than 10 min). The ceria-activated carbon composite allowed the highest removal of total organic carbon. For dye concentrations of 50 mg/L, mineralisation degrees of 100%, 98% and 97% were achieved with the composite after 2 h of reaction, respectively for CI Reactive Blue 5, CI Acid Blue 113 and CI Reactive Yellow 3. The activity of the catalyst containing cerium was affected by the presence of carbonate and bicarbonate ions due to their scavenging effect towards hydroxyl radicals; for example the mineralisation degree of CI Reactive Blue 5 (C₀ = 300 mg/L) after 120 min of reaction was only 63%, contrasting with the value of 85% obtained in the absence of carbonates. All the catalytic systems were evaluated in the treatment of textile effluents, collected before or after conventional biological treatment. Catalytic ozonation was proven to be effective when used as tertiary treatment for bio-treated effluents.     

Catalytic hydrogen production from dimethyl ether over CuFe2O4 spinel-based composites: Hydrogen reduction and metal dopant effects

Investigation of hydrogen reduction pretreatment and metal doping to Cu–Fe spinel catalyst coupled with γ-alumina was performed in dimethyl ether steam reforming for hydrogen production. The high activity and stability of the catalysts were achieved when the catalysts were reduced at or below 350 °C due to the stability of obtained Cu and Fe₃O₄ phases. Reduction at higher temperatures of 450 and 600 °C would bring about the decrease in activity and stability because the resultant Fe₃O₄ was further reduced to metallic Fe, and sintering of metallic Cu and Fe proceeded. Dopants (Mn, Cr, Co, and Al) could affect the reforming performance in terms of both activity and selectivity to products.     

Biodiesel production over Ca-based solid catalysts derived from industrial wastes

The solid oxide catalysts derived from the industrial waste shells of egg, golden apple snail, and meretrix venus were used as biodiesel production catalysts. Their catalytic activity in transesterification of palm olein oils and their physicochemical properties (by TG/DTA, EDX, SEM, N₂ sorption, CO₂-TPD, and XRD) were systematically investigated. The waste materials calcined in air with optimum conditions (temperature of 800 °C, time of 2–4 h) transformed calcium species in the shells into active CaO catalysts. The activity of the catalysts was in line with the basic amount of the strong base sites, surface area, and crystalline phase in the catalysts. All catalysts derived from egg and mollusk shells at 800 °C provided high activity (>90% fatty acid methyl ester (FAME) in 2 h). These abundant wastes showed good potential to be used as biodiesel production catalysts.     

Influence of Oxygen and Dissolved Inorganic Additives on the Removal of Gaseous Acetylaldehyde by Use of a Wetted‐Wall Corona Discharge Reactor

A cylindrical wetted‐wall corona discharge reactor was used for the removal of acetaldehyde in gas mixtures of N₂ and O₂. Gaseous acetaldehyde was removed from the gas stream by simultaneous absorption and gaseous corona reaction. The acetaldehyde absorbed in water, was decomposed by the aqueous radical, OH, produced by contact of the gas corona with the water film. There is an optimized oxygen concentration for the effective removal. When oxygen coexists in the gas mixture at 5 %, acetaldehyde was effectively removed, resulting in overall sustainable removal of acetaldehyde. However, an increase in oxygen concentration resulted in a decrease in the extent of removal, when the corona current was excessively high. This is due to corona‐induced turbulence broadening the residence time distribution of gas in the reaction zone. The decompositions of absorbed acetaldehyde and TOC in water were obviously affected by the varied oxygen concentrations. Acetaldehyde was not removed in the absence of oxygen. The dissolved inorganic additives, NaOH and HCl, strongly affected the acetaldehyde absorbability into water and subsequently, the decomposition rate of the absorbed acetaldehyde.