Theeranun Siritanon

Economical and green biodiesel production process using river snail shells-derived heterogeneous catalyst and co-solvent method.

River snail shells-derived CaO was used as a heterogeneous catalyst to synthesize biodiesel via transesterification of palm oil with methanol. The shell materials were calcined in air at 600-1000°C for 3h. Physicochemical properties of the resulting catalysts were characterized by TGA-DTG, XRD, SEM, BET, XRF, FT-IR and TPD. CaO catalyzed transesterification mechanism of palm oil into biodiesel was verified. The effects of adding a co-solvent on kinetic of the reaction and %FAME yield were investigated. %FAME yield of 98.5%±1.5 was achieved under the optimal conditions of catalyst/oil ratio of 5wt.%; methanol/oil molar ratio of 12:1; reaction temperature of 65°C; 10%v/v of THF in methanol and reaction time of 90min. The results ascertained that river snail shells is a novel raw material for preparation of CaO catalyst and the co-solvent method successfully decreases the reaction time and biodiesel production cost.

Structural studies and electrical properties of Cs/Al/Te/O phases with the pyrochlore structure.

A series of polycrystalline and single crystal cesium aluminum tellurates with the pyrochlore structure have been prepared and characterized. The variations in cell edge for the Cs/Al/Te/O phases range from 10.06 Å for the Al rich limit to 10.14 Å for the Te rich limit. Rietveld structural analyses based on both X-ray and neutron diffraction data were performed on 5 different compositions. Single crystals of 3 compositions were prepared and studied by X-ray diffraction. The anharmonic component of the thermal motion for Cs was small but became significant on replacing Cs with Rb. A maximum in the electrical conductivity of about 0.1 S/cm is found in the middle of this range close to the ideal composition of CsAl(1/3)Te(5/3)O(6). The conductivity is attributed to filled Te 5s states associated with Te(4+) lying just below the conduction band based on empty Te 5s states associated with Te(6+). The relatively large Te(4+) ion is compressed by the lattice, and as this compression increases the filled 5s states approach the conduction band and thereby increases conductivity.

CsTe2O6–x: Novel Mixed-Valence Tellurium Oxides with Framework-Deficient Pyrochlore-Related Structure

Structures of CsTe₂O(6-x) phases were investigated by single-crystal X-ray diffraction and neutron powder diffraction. Stoichiometric CsTe₂O₆ is a mixed-valence Cs₂Te⁴⁺Te₃⁶⁺O₁₂ compound with a rhombohedral pyrochlore-type structure where there is complete order of Te⁴⁺ and Te⁶⁺. On heating, this compound develops significant electrical conductivity. As CsTe₂O₆ becomes oxygen deficient above 600 °C, the rhombohedral pyrochlore-type structure is replaced by a cubic pyrochlore-type structure with disordered Te⁴⁺/Te⁶⁺ and oxygen vacancies. However, for CsTe₂O(6-x) phases prepared at 500 °C, the observed pyrochlore-type structure has symmetry. The Te⁴⁺ and O vacancies are all on chains running along the b axis, and the maximum value of x observed is about 0.3. At still higher values of x a new compound was discovered with a structure related to that reported for Rb₄Te₃⁴⁺Te₅⁶⁺O₂₃.

Multi step energy transfer between three Si_LTL and SiGe_LTL zeolite-loaded dyes

We report a novel potential light-harvesting antenna material constructed with three dyes loaded on two types of zeolite LTL (SiGe_LTL and Si_LTL). Fluorescence resonance energy transfer (FRET) occurs from acridine hydrochloride (Ac) to Thionine acetate (Th) via Acriflavine hydrochloride (AF), which acts as an antenna to receive and transfer energy from Ac to Th. We compared multistep FRET systems based on dye-loaded SiGe_LTL paired with an Si_LTL-based system. Our results show that in both cases, FRET efficiency increases with Th loading and decreases with increasing AF loading. Moreover, the zeolite LTL microenvironment causes a red shift in the fluorescence spectra of the three SiGe_LTL-loaded-dyes compared to those of the Si_LTL-based dyes.

Structure and electrochemical properties of acid-leached LiMn 2 − x Ti x O 4

To gain deeper understanding on the relationships between crystal structure and electrochemical properties of manganese oxide electrodes for supercapacitors, acid-leached LiMn2 − xTixO4 were investigated. Based on both Reitveld refinement on X-ray diffraction patterns and X-ray absorption near edge structure, it is proposed that replacing some Mn with Ti not only enlarges the unit cells but also alters the crystal structure, specifically the occupancy of each element in the lattice. While the tetrahedral 8a position and octahedral 16c position are both vacant in leached MnO2, those in leached LiMn2 − xTixO4 with x > 0 are occupied by Ti and Mn, respectively. The differences in the unit cell dimension and the crystal structure affect the electrochemical behaviors of the compounds. Although the total specific capacitance generally decreases with Mn active species, trend in %Cins is opposite in samples with x = 0.25–0.75. Despite having some cations in the positions which should hinder the ion diffusion, the enlarged cavity size resulting from Ti substitution promotes the diffusion process and enhances the insertion capacitance in these samples.

Photocatalytic and electrically conductive transparent Cl-doped ZnO thin films via aerosol-assisted chemical vapour deposition

A simple, economical and effective solution-based chemical vapour deposition (CVD) technique, aerosol-assisted CVD, has been successfully applied to produce inexpensive Cl-doped ZnO films using Zn acetate dihydrate and FeCl3. X-ray photoelectron spectroscopy and the increase in cell parameters from powder X-ray diffraction determined that Cl had been doped into the wurtzite ZnO lattice. The Cl-doping had a significant effect on the morphology of the thin films synthesised and resulted in an improvement in the visible light transmission and lower electrical resistance (typical resistivities of doped films ∼10−2 Ω cm). The highest transmittance (% T) of 85% was obtained when 7 mol% FeCl3 was used in the precursor solution and the lowest resistivity of 4.28 ± 0.41 × 10−2 Ω cm was obtained with 5 mol% FeCl3. The greatest photocatalytic activity of stearic acid degradation under UVA irradiation was obtained on using 10 mol% FeCl3, resulting in the highest formal quantum efficiency (FQE) of 3.0 ± 0.1 × 10−4 molecule per photon. These films, therefore, display transparent conducting oxide and photocatalytic properties, giving multifunctional characteristics and promising applications.

Unsaturated Mn(II)-Centered [Mn(BDC)]n Metal–Organic Framework with Strong Water Binding Ability and Its Potential for Dehydration of an Ethanol/Water Mixture

An unsaturated Mn(II)-centered metal-organic framework was synthesized. The presence of an unsaturated Mn(II) center, together with a guest-responsive structural changing feature, plays a crucial role for strong binding with water, leading to its potential application for water/ethanol separation. In addition, the present framework is thermally stable up to 400 °C, which is beneficial for the regeneration process after adsorption.

Single crystal growth and structure refinements of CsM{sub x}Te{sub 2-x}O{sub 6} (M = Al, Ga, Ge, In) pyrochlores

Graphical abstract: Single crystals of CsM{sub x}Te{sub 2-x}O{sub 6} pyrochlores with M = Al, Ga, Ge, and In have been grown and structure refinements indicate deviations from ideal stoichiometry presumably related to mixed valency of tellurium. Highlights: {yields} Single crystals of CsM{sub x}Te{sub 2-x}O{sub 6} pyrochlores with M = Al, Ga, Ge, and In have been grown. {yields} Structure refinements from single crystal X-ray diffraction data confirm e structure. {yields} Deviations from ideal stoichiometry suggest mixed valency of tellurium and hence conductivity. -- Abstract: Single crystals of CsM{sub x}Te{sub 2-x}O{sub 6} pyrochlores with M = Al, Ga, Ge, and In have been grown from a TeO{sub 2} flux. Structure refinements from single crystal X-ray diffraction data are reported. These results are used to discuss deviations from ideal stoichiometry that result in electronic conductivity presumably related to mixed valency of tellurium.