A simple route utilizing surfactant-assisted templating sol-gel process for synthesis of mesoporous Dy2O3 nanocrystal

A simple route of combined sol-gel process with surfactant-assisted templating technique was successfully employed for the first time to synthesize nanocrystalline mesoporous Dy(2)O(3) with narrow monomodal pore size distribution under mild conditions. The nanocrystalline Dy(2)O(3) with monomodal mesoporous characteristic was ultimately achieved by controlling the hydrolysis and condensation steps of dysprosium n-butoxide modified with acetylacetone in the presence of laurylamine hydrochloride surfactant aqueous solution. The synthesized material was methodically characterized by thermogravimetry and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED), N(2) adsorption-desorption, Brunauer-Emmett-Teller (BET) surface area analysis, and Barrett-Joyner-Halenda (BJH) pore size distribution analysis. The particle size of the synthesized Dy(2)O(3) in nanosized range obtained from the SEM and HRTEM micrographs was in good accordance with the crystallite size estimated from the XRD result. The N(2) adsorption-desorption result exhibited hysteresis pattern with single loop, indicating the existence of monomodal mesopore. The extremely narrow pore size distribution with mean pore diameter in the mesopore region of the synthesized Dy(2)O(3) was also confirmed by the BJH result.     

Study of Ca-ATMP precipitation in the presence of magnesium ion

ATMP (aminotri(methylenephosphonic acid)), a phosphonate scale inhibitor used in the petroleum industry, was used as a model scale inhibitor in this study. One of the goals of this work was to determine the range of conditions under which Mg ions, which are formed in reservoir formations containing dolomite, modulate the formation of Ca-ATMP precipitate as a scale inhibitor. The results revealed that the amount of ATMP precipitated decreased with addition of Mg ions in solution at all values of the solution pH. Furthermore, an increase in both the solution pH and the concentration of the divalent cations in solution resulted in a change of the molar ratio of (Ca + Mg) to ATMP in the precipitates. At a low solution pH (pH 1.5), Mg ions had little effect on the composition of the Ca-ATMP precipitate. However, at higher values of the solution pH (pH 4 and 7), the Ca to ATMP molar ratio in the precipitates decreased with increasing concentration of the Mg. Here it was found that Mg ions replaced Ca ions on available reactive sites of ATMP molecules. These results determined the limits of the Mg ion concentration, which affects the precipitation of Ca-ATMP, Mg-ATMP, and (Ca + Mg)-ATMP. The dissolution of the scale inhibitors was studied using a rotating disk reactor. These experiments showed that the total divalent cation molar ratio (Ca + Mg) to ATMP in the precipitates is the primary factor that controls the rate of dissolution (release) of the phosphonate precipitates. The phosphonate precipitate dissolution rates decreased as the molar ratio of divalent cations to ATMP in the precipitates increased.     

Surface Characterization and Antimicrobial Activity of Chitosan-Deposited DBD Plasma-Modified Woven PET Surface

In this work, a woven PET with an antimicrobial activity was prepared by depositing chitosan on its surface. Firstly, the hydrophilic property of the PET surface was achieved by a plasma treatment using dielectric barrier discharge (DBD). The hydrophilic property of the PET surface was characterized by wickability and contact angle measurements. The XPS analysis revealed an increment of oxygen-containing polar groups, such as C–O and O–C=O, on the PET surface after the plasma treatment, resulting in an enhanced hydrophilic property. The plasma-treated PET specimen was further deposited with chitosan by immersing in a chitosan acetate aqueous solution. The effects of temperature, chitosan concentration, and number of rinses on the amount of deposited chitosan on the PET surface were investigated. The disappearance of the above-mentioned polar groups from the PET surface was clearly observed after the chitosan deposition, indicating the involvement of these functional groups in interacting with the chitosan. The chitosan-deposited plasma-treated woven PET possessed an exceptionally high antimicrobial activity against both E. coli (gram-negative bacteria) and S. aureus (gram-positive bacteria).     

Ethylene Epoxidation in an AC Dielectric Barrier Discharge Jet System

In this work, ethylene epoxidation was investigated in a dielectric barrier discharge jet (DBDJ) with a separate ethylene/oxygen feed under oxygen lean conditions. The ethylene (C₂H₄) stream was directly injected behind the plasma zone in order to reduce all undesired reactions, including C₂H₄ cracking and further reactions, while the oxygen (O₂) balanced with argon was fed through the plasma zone totally to maximize the formation of active oxygen species. The effects of various operating parameters, such as total feed flow rate, O₂/C₂H₄ feed molar ratio, applied voltage, input frequency, and C₂H₄ feed position on the ethylene epoxidation activity, were investigated to determine the optimum operating conditions for this new DBDJ system. The highest ethylene oxide (EO) selectivity (55.2 %) and yield (27.6 %), as well as the lowest power consumption (3.3 × 10^?21 and 6.0 × 10^?21 Ws/molecule C₂H₄ converted and EO produced, respectively) were obtained at a total feed flow rate of 1,625 cm³/min (corresponding to a residence time of 0.022 s), an O₂/C₂H₄ feed molar ratio of 0.25:1, an applied voltage of 9 kV, an input frequency of 300 Hz, and a C₂H₄ feed position of 3 mm behind the plasma zone. The superior activity of the ethylene epoxidation in the DBDJ system resulted from a small reaction volume as well as a separate ethylene/oxygen feed.     

Ethylene Epoxidation in Low-Temperature AC Dielectric Barrier Discharge: Effect of Electrode Geometry

In this work, the epoxidation of ethylene under a cylindrical dielectric barrier discharge (DBD) reactor and a parallel DBD reactor was comparatively studied. The effects of important operating parameters—feed O₂/C₂H₄ molar ratio, applied voltage, input frequency, and residence time—were investigated on the reaction performance in terms of reactant conversions, product selectivities, product yields, and power consumptions per molecule of ethylene converted and per molecule of ethylene oxide produced. The optimum conditions obtained from the operating parameter investigation were used for a comparative performance evaluation of both DBD reactor systems. It was found that under the optimum conditions of each system, the cylindrical DBD system exhibited superior epoxidation performance for ethylene oxide production compared to the parallel DBD system, indicating that the electrode geometry (electrode edge length-to-electrode surface area ratio) plays a significant role in the ethylene epoxidation.     

Methylaluminoxane‐free ethylene polymerization with in situ activated zirconocene triisobutylaluminum catalysts and silica‐supported stabilized borate cocatalysts

Heterogenization of tris(pentafluorophenyl)borane [B(C₆F₅)₃] on a silica support stabilized with chlorotriphenylmethane (CICPh₃) and N,N‐dimethylaniline (HNMe₂Ph) creates the following supported borane cocatalysts: [HNMe₂Ph]⁺[B(C₆F₅)₃‐SiO₂]^? and [CPh₃]⁺[B(C₆F₅)₃‐SiO₂]^?. These supported catalysts were reacted with Cp₂ZrCl₂ TIBA in situ to generate active metallocene species in the reactor. Triisobutylaluminum (TIBA) was a good coactivator for dichloro‐zirconocene, acting as the prealkylating agent to generate cationic zirconocene (Cp₂ZrC₄H₉⁺). The catalytic performances were determined from the kinetics of ethylene‐consumption profiles that were independent of the time dedicated to the activation of the catalysts. The scanning electron microscopy‐energy dispersive X‐ray measurements showed that B(C₆F₅)₃ dispersed uniformly on the silica support. Under our reaction conditions, the [CPh₃]⁺[B(C₆F₅)₃‐SiO₂]^? system had higher productivity and weight‐average molecular weight than the [HNMe₂Ph]⁺[B(C₆F₅)₃‐SiO₂]^? system. For the [CPh₃]⁺[B(C₆F₅)₃‐SiO₂]^? system, the productivity increased with the amount catalyst; however, the polydispersity index of polyethylene synthesized did not change. The final shape of polymer particles was a larger‐diameter version of the original support particle. The polymer particles synthesized with supported [CPh₃]⁺[B(C₆F₅)₃‐SiO₂]^? catalysts had larger diameters. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3240–3248, 2002     

Photooxidative mineralization of microorganisms-produced glycolipid biosurfactants by a titania-mediated advanced oxidation process

The photooxidative mineralizations of two microorganisms-produced glycolipid biosurfactants 4-O-(4′,6′-di-O-acetyl-2′,3′-di-O-alkanoyl-β-d-mannopyranosyl)-d-erythritol (MEL-A) and 1-O-(6′-O-acetyl-2′,3′-di-O-alkanoyl-β-d-mannopyranosyl)-d-erythritol (MEL-B) were examined by monitoring the temporal changes in UV absorption, the time profiles of CO₂ evolution and the changes in interfacial tension occurring by an advanced oxidation process in the presence of a metal-oxide (TiO₂). Features of their mineralization are compared to the photomineralization of the anionic dodecylbenzene sulfonate (DBS) surfactant carried out under otherwise identical conditions. The adsorption of surfactants on the TiO₂ surface and the positions of attack of the photogenerated OH radicals on the surfactants’ structure were assessed by molecular orbital (MO) calculations of partial charges and frontier orbital electron densities, respectively. The photodegradation of DBS was faster than the MELs as also evidenced by surface tension measurements, whereas the photomineralization of the anionic DBS surfactant was definitely slower than that of the MEL biosurfactants due to the hydrophobic alkyl chain in the DBS structure. Possible initial mechanistic stages of the photooxidation of MEL-A and MEL-B are proposed based on experimental data and comparison with MO calculations.     

The Influence of Nonionic Surfactant Adsorption on Enzymatic Hydrolysis of Oil Palm Fruit Bunch

Nonionic surfactants have been utilized to improve the enzymatic hydrolysis of lignocellulosic materials. However, the role of surfactant adsorption affecting enzymatic hydrolysis has not been elaborated well. In this work, nonionic surfactants differing in their molecular structures, namely the polyoxyethylene sorbitan monooleate (Tween 80), the secondary alcohol ethoxylate (Tergitol 15-S-9), and the branched alcohol ethoxylate (Tergitol TMN-6), were studied for their effects on the enzymatic hydrolysis of palm fruit bunch (PFB). The PFB was pretreated with a 10% w/v sodium hydroxide solution and then hydrolyzed using the cellulase enzyme from Trichoderma reesei (ATCC 26921) at 50 °C and pH 5. The optimal conditions providing similar yields of reducing sugar required Tween 80 and Tergitol TMN-6 at 0.25% w/v, while Tergitol 15-S-9 was required at 0.1% w/v. All the surfactants improved the enzymatic conversion efficiency and reduced unproductive binding of the enzyme to lignin. In addition, the adsorption isotherm of cellulase was fit well by the Freundlich isotherm, while adsorption of the three nonionic surfactants agreed well with the Langmuir isotherm. Adsorption capacities of the three nonionic surfactants were consistent with their enhancement efficiencies in hydrolysis. The critical micelle concentration was observed as a key property of nonionic surfactant for adsorption capacity.     

Improving the Performance of Heterogeneous Borane Cocatalysts by Pretreatment of the Silica Support with Alkylaluminum Compounds

The treatment of silica with alkylaluminum compounds, triisobutylaluminum (TIBA) and triethylaluminum (TEA), dramatically enhanced the cocatalytic performances of the [CPh₃]⁺[B(C₆F₅)₃—SiO₂]^–. We measured the productivity and ethylene‐consumption profiles for [CPh₃]⁺[B(C₆F₅)₃—SiO₂]^– cocatalysts and Cp₂ZrCl₂/TIBA. Both of the treated cocatalyst systems improved the average molecular weight of the product when compared with the untreated cocatalyst system. The TIBA‐treated cocatalyst provided a narrow molecular weight distribution while the TEA‐treated cocatalyst system gave a broad distribution.     

Scale inhibition study by turbidity measurement

The concept of a critical supersaturation ratio (CSSR) has been used to characterize the effectiveness of different types of scale inhibitors, inhibitor concentration, and precipitating solution pH in order to prevent the formation of barium sulfate scale. The scale inhibitors used in this work were aminotrimethylene phosphonic acid (ATMP), diethylenetriaminepentamethylene phosphonic acid (DTPMP), and phosphinopolycarboxylic acid polymer (PPCA). The CSSR at which barium sulfate precipitates was obtained as a function of time for different precipitation conditions and was used as an index to evaluate the effect of the precipitation conditions. The results showed that the CSSRs decrease with increasing elapsed time after mixing the precipitating solutions, but increases with increasing scale inhibitor concentration and solution pH. The CSSR varies linearly with the log of the scale inhibitor concentration and with the precipitating solution pH. A SEM analysis showed that the higher the scale inhibitor concentration and solution pH, the smaller and more spherical the BaSO4 precipitates. Analysis of the particle size distribution revealed that increasing the elapsed time, the scale inhibitor concentration, and precipitating solution pH, all produce a broader particle size distribution and a smaller mean diameter of the BaSO4 precipitates. DTPMP and PPCA were the most effective BaSO4 scale inhibitors per ionizable proton and the most effective on a concentration basis, respectively.