Kirkwood-Buff Analysis of Binary and Ternary Systems Consisting of Alcohols (Methanol, Ethanol, 1-Propanol, and 2-Propanol), Water, and n-Hexane to Understand the Formation of Surfactant-Free Microemulsions.

Surfactant-free microemulsion (SFME) represents a class of fluid mixtures that can form microheterogeneous structures without detergents, offering an environmentally benign alternative to traditional microemulsions. However, the formation mechanism is still elusive. This work applies the Kirkwood-Buff theory to mixtures of alcohols, water, and n-hexane to elucidate the SFME formation mechanism. To ensure robust calculation of the Kirkwood-Buff integrals (KBIs), we construct a data set of densities and excess free energies of binary and ternary systems. Multiple excess Gibbs free energy models are assessed against this data set to select the most suitable model reproducing the experimental results. In addition, we introduce statistical methods to determine the optimal polynomial order of the Redlich-Kister correlation for the excess volume data. We first validate our methodology in binary systems. Then, we extend the calculation method to ternary mixtures. The KBI calculation results reveal that the alcohol-hexane and water-hexane interactions do not significantly affect SFME formation. In contrast, the interplay among water-water, water-alcohol, and alcohol-alcohol interactions critically influences the ability of a liquid mixture to form SFME structures. SFME systems exhibit the facile formation of water aggregates enveloped by alcohols, whereas non-SFME systems demonstrate homogeneous alcohol/water droplets dispersed in an oil continuous medium.

Effect of supercritical carbon dioxide on the enzymatic production of biodiesel from waste animal fat using immobilized Candida antarctica lipase B variant.

BACKGROUND: Waste animal fat is a promising feedstock to replace vegetable oil that widely used in commercial biodiesel process, however the high content of free fatty acid in waste fat makes it unfeasible to be processed with commercial base-catalytic process. Enzymatic process is preferable to convert waste fat into biodiesel since enzyme can catalyze both esterification of free fatty acid and transesterification of triglyceride. However, enzymatic reaction still has some drawbacks such as lower reaction rates than base-catalyzed transesterification and the limitation of reactant concentration due to the enzyme inhibition of methanol. Supercritical CO2 is a promising reaction media for enzyme-catalyzed transesterification to overcome those drawbacks. RESULT: The transesterification of waste animal fat was carried out in supercritical CO2 with varied concentration of feedstock and methanol in CO2. The CO2 to feedstock mass ratio of 10:1 showed the highest yield compared to other ratios, and the highest FAME yield obtained from waste animal fat was 78%. The methanol concentration effect was also observed with variation 12%, 14%, and 16% of methanol to feedstock ratio. The best yield was 87% obtained at the CO2 to feedstock ratio of 10: 1 and at the methanol to feedstock ratio of 14% after 6 h of reaction. CONCLUSION: Enzymatic transesterification to produce biodiesel from waste animal fat in supercritical fluid media is a potential method for commercialization since it could enhance enzyme activity due to supercritical fluid properties to remove mass transfer limitation. The high yield of FAME when using high mass ratio of CO2 to oil showed that supercritical CO2 could increase the reaction and mass transfer rate while reducing methanol toxicity to enzyme activity. The increase of methanol concentration also increased the FAME yield because it might shift the reaction equilibrium to FAME production. This finding describes that the application of supercritical CO2 in the enzymatic reaction enables the application of simple process such as a packed-bed reactor.

Hydro- and solvothermolysis of kraft lignin for maximizing production of monomeric aromatic chemicals.

The hydro-/solvothermolysis of kraft lignin using water and ethanol as a solvent were investigated in this study. The effect of the water-to-ethanol ratio on the yields of monomeric aromatic chemicals (MACs) and the kinetic behavior of MACs was studied in a series of batch experiments. The yields of MACs other than catechol increased as the ratio of ethanol increased, and the content of the total MACs in bio-crude oil (BCO) reached 35% when the ratio of ethanol was 100% at a reaction temperature of 300 °C. The formation of phenol, guaiacol, and alkylguaiacols was enhanced in ethanol, while the formation of catechol was dominant in water. The formation of more substituted MACs such as vanillin, acetoguaiacone, and homovanillic acid was not affected by the solvent. The role of reaction parameters on the yields of MACs was elucidated, and the main reaction pathways in water and in ethanol were proposed.

Low-temperature, selective catalytic deoxygenation of vegetable oil in supercritical fluid media.

The effects of supercritical fluids on the production of renewable diesel-range hydrocarbons from natural triglycerides were investigated. Various supercritical fluids, which included CO2 (scCO2 ), propane (scC3 H8 ) and n-hexane (scC6 H14 ), were introduced with H2 and soybean oil into a fixed-bed reactor that contained pre-activated CoMo/γ-Al2 O3 . Among these supercritical fluids, scC3 H8 and scC6 H14 efficiently allowed the reduction of the reaction temperature by as much as 50 °C as a result of facilitated heat and mass transfer and afforded similar yields to reactions in the absence of supercritical fluids. The compositional analyses of the gas and liquid products indicated that the addition of scC3 H8 during the hydrotreatment of soybean oil promoted specific deoxygenation pathways, decarbonylation and decarboxylation, which consumed less H2 than the hydrodeoxygenation pathway. As a result, the quantity of H2 required to obtain a high yield of diesel-range hydrocarbons could be reduced to 57 % if scC3 H8 was used. As decarboxylation and decarbonylation are mildly endothermic reactions, the reduced heat transfer resistance in scC3 H8 may drive the deoxygenation reaction to thermodynamically favourable pathways.

Highly angle tolerant filter incorporating serially cascaded a-Si based etalons and its application to a compact receiver.

A highly angle tolerant spectral filter has been implemented taking advantage of three-stage serially concatenated resonators in dielectric films, each of which involves a high-index cavity in a-Si, sandwiched with a pair of SiO2 films. For the constituent etalons, the free spectral range is individually adjusted by differentiating the thickness of the cavity, so that a primary infrared pass-band could be attained to present enhanced roll-off characteristics in conjunction with an appropriate bandwidth. The a-Si cavities relating to the three etalons are selected to be 117, 234, and 468-nm thick, while the SiO2 layer is uniformly 150-nm thick. The filter is actually created on a silica glass substrate, by alternately depositing SiO2 and a-Si films. The observed center wavelength, bandwidth, and peak transmission efficiency are about 900 nm, 120 nm, and over 90%, respectively, for normal incidence. In response to an angle change amounting to 60°, the relative wavelength shift and the variation in peak transmission become barely 0.03 and 8%, respectively. Finally, a detecting cell is constructed by integrating the prepared filter with a photodiode, thus rendering a 3-dB angular bandwidth of 90°. By adequately arranging three detecting cells in a fixture, a compact, portable optical receiver could then be constructed. For incoming collimated light at λ = 905 nm, the infrared receiver exhibits an extended 3-dB angular acceptance as large as 160°.

Compact laser transmitter delivering a long-range infrared beam aligned with a monitoring visible beam.

A compact laser transmitter, which takes advantage of an optical subassembly module, was proposed and demonstrated, providing precisely aligned collinear IR and visible beams. The collimated IR beam acts as a long-range projectile for simulated combat, carrying an optical pulsed signal, whereas the visible beam plays the role of tracking the IR beam. The proposed laser transmitter utilizes IR (λ(1)=905 nm) and visible (λ(2)=660 nm) light sources, a fiber-optic collimator, and a beam combiner, which includes a wavelength division multiplexing (WDM) filter in conjunction with optical fiber. The device was built via the laser welding technique and then evaluated by investigating the characteristics of the generated light beams. The IR collimated beam produced had a Gaussian profile and a divergence angle of ~1.3 mrad, and the visible monitoring beam was appropriately collimated to be readily discernible in the vicinity of the transmitter. The two beams were highly aligned within an angle of 0.004 deg as anticipated. Finally, we performed a practical outdoor field test to assess the IR beam with the help of a receiver. An effective trajectory was observed ranging up to 660 m with an overall detectable beam width of ~60 cm.

Synthesis of biodiesel from rapeseed oil using supercritical methanol with metal oxide catalysts.

This study examined the synthesis of biodiesel using supercritical or subcritical methanol with metal oxide catalysts. The transesterification of rapeseed oil was carried out with the metal oxide catalysts (SrO, CaO, ZnO, TiO(2) and ZrO(2)) to determine the most effective heterogeneous catalyst having the highest catalytic activity with minimum weight loss caused by dissolution. SrO and CaO dissolved in the biodiesel during the reaction because they were transformed to strontium methoxide and calcium methoxide, respectively. ZnO was the optimum catalyst for the transesterification of rapeseed oil owing to its high activity and minimum weight loss in supercritical methanol. The optimal reaction conditions included a molar ratio of methanol to oil of 40 in the presence of 1.0wt.% ZnO and a reaction time of 10min. The supercritical process with ZnO as a catalyst appears economically viable.

Synergetic effect of copper-plating wastewater as a catalyst for the destruction of acrylonitrile wastewater in supercritical water oxidation.

A new supercritical water oxidation process for the simultaneous treatment of mixed wastewater containing wastewater from acrylonitrile manufacturing processes and copper-plating processes was investigated using a continuous tubular reactor system. Experiments were carried out at temperatures ranging from 400 to 600 degrees C and a pressure of 25 MPa. The residence time was fixed at 2s by changing the flow rates of feeds, depending on reaction temperature. The initial total organic carbon (TOC) concentration of the wastewaters and the O(2) concentration at the reactor inlet were kept constant at 0.49 and 0.74 mol/L. It was confirmed that the copper-plating wastewater accelerated the TOC conversion of acrylonitrile wastewater from 17.6% to 67.3% at a temperature of 450 degrees C. Moreover, copper and copper oxide nanoparticles were generated in the process of supercritical water oxidation (SCWO) of mixed wastewater. 99.8% of copper in mixed wastewater was recovered as solid copper and copper oxides at a temperature of 600 degrees C, with their average sizes ranging from 150 to 160 nm. Our study showed that SCWO provides a synergetic effect for simultaneous treatment of acrylonitrile and copper-plating wastewater. During the reaction, the oxidation rate of acrylonitrile wastewater was enhanced due to the in situ formation of nano-catalysts of copper and/or copper oxides, while the exothermic decomposition of acrylonitrile wastewater supplied enough heat for the recovery of solid copper and copper oxides from copper-plating wastewater. The synergetic effect of wastewater treatment by the newly proposed SCWO process leads to full TOC conversion, color removal, detoxification, and odor elimination, as well as full recovery of copper.

Color filter incorporating a subwavelength patterned grating in poly silicon.

A color filter based on a subwavelength patterned grating in poly silicon was proposed and realized on a quartz substrate. It was produced by utilizing the laser interference lithography technique to feature wide effective area compared to the costly e-beam lithography. An oxide layer was introduced on top of the silicon grating layer as a mask to facilitate the silicon-etching and to enhance the filtering selectivity as well. The structural parameters for the device include the grating pitch and height of 450 nm and 100 nm respectively, the silicon stripe width of 150 nm, and the oxide thickness of 200 nm. The fabricated device offered a spectral response suitable for a blue color filter, exhibiting the center wavelength of approximately 460 nm, the bandwidth approximately 90 nm and the peak transmission 40%. The positional dependence of its performance was examined to find the effective area of 3 x 3 mm(2), where the variation in the relative transmission efficiency and in the center wavelength was less than 10% and 2 nm respectively. Finally, the influence of the angle of the incident beam upon the transfer characteristics of the device was investigated to reveal that the rate of change in the relative transmission was equivalent to about 1.5%/degree.