Exploring Si/Mg composite supported Ziegler-Natta Ti-based catalysts for propylene polymerization

A series of(Si_O2/MgO/ID/MgCl_2)·TiClx Ziegler-Natta catalysts for propylene polymerization has been prepared with a new method. These catalysts were synthesized using soluble Mg-compounds as the Mg-source and the preparation progress was relatively simple. The catalyst could copy the spherical shape of the carrier very well. The propylene polymerization results showed that the catalyst revealed the best activity with 9,9-di(methoxymethyl)fluorene(BMMF) as internal donor at 50 °C with the optimal molar ratio Al/Ti = 5, which was much lower than what the industrial polypropylene catalyst used(at least molar ratio Al/Ti = 100), resulting in great cost saving. Additionally, the polymerization kinetics of the catalyst exhibited very stable property after achieving a relatively high value. These catalysts possessed rather high activity and good hydrogen response. The isotactic index(Ⅱ.) value of the PP products could be higher than 98% in the presence of both internal and external electron donors. Moreover, temperature rising elution fractionation method was used to understand the influence of donors and H2 on the properties of the PP products.     

Gold Surface Functionalization with S‐containing Organic Compounds and Gold Nanoparticles for Ethylene Glycol Electrooxidation

In this work a gold electrode modified with self‐assembled layers (SAMs) composed with organic S‐containing compound and gold nanoparticles was prepared. The electrode with SAMs endowed with gold nanoparticles gave the high catalytic effect for ethylene glycol (EG) electrooxidation in solution at pH 7. For this novel sensor a linear relationship between the current response of EG at the potential of peak maximum (j_p) and the concentration of this compound in solution (c_EG) was found over the range 0.1 µM to 0.7 M with the detection sensitivity j_p/c_EG equal to about 5 A cm^?2 mol^?1 dm³ (at v=0.1 V s^?1) and the detection limit of 0.046 µM.     

Electricity Production and Characterization of High-Strength Industrial Wastewaters in Microbial Fuel Cell

Microbial fuel cells (MFCs) convert electrochemical energy into electrical energy immediately and have a big potential usage for the same time wastewater treatment and energy recovery via electro-active microorganisms. However, MFCs must be efficiently optimized due to its limitations such as high cost and low power production. Finding new materials to increase the cell performance and reduce cost for MFC anodes is mandatory. In the first step of this study, different inoculation sludges such as anaerobic gum industry wastewater, anaerobic brewery wastewater and anaerobic phosphate were tested, and MFC that was set up with anaerobic gum industry wastewater inoculation sludge exhibited the highest performance. In the second step of this study, various wastewaters such as chocolate industry, gum industry and slaughterhouse industry were investigated for anode bacteria sources. Several electrochemical techniques have been employed to elucidate how wastewaters affect the MFCs’ performance. Among all the mentioned wastewaters, the best performance was achieved by the MFCs fed with slaughterhouse wastewater; this device produced a maximum power density of 267 mW·m^?2.     

Microplate-Based Evaluation of the Sugar Yield from Giant Reed,Giant Miscanthus and Switchgrass after Mild Chemical Pre-Treatments and Hydrolysis with Tailored <Emphasis Type="Italic">Trichoderma</Emphasis> Enzymatic Blends

Giant reed, miscanthus, and switchgrass are considered prominent lignocellulosic feedstocks to obtain fermentable sugars for biofuel production. The bioconversion into sugars requires a delignifying pre-treatment step followed by hydrolysis with cellulase and other accessory enzymes like xylanase, especially in the case of alkali pre-treatments, which retain the hemicellulose fraction. Blends richer in accessory enzymes than commercial mix can be obtained growing fungi on feedstock-based substrates, thus ten selected Trichoderma isolates, including the hypercellulolytic strain Trichoderma reesei Rut-C30, were grown on giant reed, miscanthus, or switchgrass-based substrates. The produced enzymes were used to saccharify the corresponding feedstocks, compared to a commercial enzymatic mix (6 FPU/g). Feedstocks were acid (H₂SO₄ 0.2–2%, w/v) or alkali (NaOH 0.02–0.2%, w/v) pre-treated. A microplate-based approach was chosen for most of the experimental steps due to the large number of samples. The highest bioconversion was generally obtained with Trichoderma harzianum Or4/99 enzymes (78, 89, and 94% final sugar yields at 48 h for giant reed, miscanthus, and switchgrass, respectively), with significant increases compared to the commercial mix, especially with alkaline pre-treatments. The differences in bioconversion yields were only partially caused by xylanases (maximum R ² = 0.5), indicating a role for other accessory enzymes.     

Effect of Light/Dark Regimens on Hydrogen Production by <Emphasis Type="Italic">Tetraselmis subcordiformis</Emphasis> Coupled with an Alkaline Fuel Cell System

To improve the photoproduction of hydrogen (H₂) by a green algae-based system, the effect of light/dark regimens on H₂ photoproduction regulated by carbonyl cyanide m-chlorophenylhydrazone (CCCP) was investigated. A fuel cell was integrated into a photobioreactor to allow online monitoring of the H₂ evolution rate and decrease potential H₂ feedback inhibition by consuming the generated H₂ in situ. During the first 15 h of H₂ evolution, the system was subjected to dark treatment after initial light illumination (L/D = 6/9 h, 9/6 h, and 12/3 h). After the dark period, all systems were again exposed to light illumination until H₂ evolution stopped. Two peaks were observed in the H₂ evolution rate under all three light/dark regimens. Additionally, a high H₂ yield of 126 ± 10 mL L^?1 was achieved using a light/dark regimen of L 9 h/D 6 h/L until H₂ production ceased, which was 1.6 times higher than that obtained under continuous illumination. H₂ production was accompanied by some physiological and morphological changes in the cells. The results indicated that light/dark regimens improved the duration and yield of H₂ photoproduction by the CCCP-regulated process of Tetraselmis subcordiformis.     

Measurement of mineral solubilities in the ternary systems NaCl−ZnCl<Subscript>2</Subscript>−H<Subscript>2</Subscript>O and MgCl<Subscript>2</Subscript>−ZnCl<Subscript>2</Subscript>−H<Subscript>2</Subscript>O at 373 K

In this work, the solubilities of the salt minerals and the densities of solution in two ternary systems sodium chloride–zinc chloride–water and magnesium chloride–zinc chloride–water were measured at 373 K using an isothermal solution saturation method. Based on the determined equilibrium solubility data and the corresponding equilibrium solid phase, the phase diagrams and density diagrams of the two systems were plotted. The results show that the two ternary systems are complex and the eutectic points, the univariant solubility curves and the solid crystalline phase regions are shown and discussed. The phase diagram of the ternary system NaCl?ZnCl₂?H₂O at 373 K is constituted of two eutectic points, three univariant solubility curves and three solid crystalline phase regions corresponding to NaCl, ZnCl₂ and 2NaCl · ZnCl₂. And the phase diagram of the ternary system MgCl₂?ZnCl₂?H₂O at 373 K includes two eutectic points, three univariant solubility curves and three solid crystalline phase regions corresponding to MgCl₂ · 6H₂O, MgCl₂ · ZnCl₂ · 5H₂O and ZnCl₂. The experimental results were simply discussed.     

Acid–base and coordination properties of <Emphasis Type="Italic">Meso</Emphasis>-substituted porphyrins in nonaqueous solutions

Acid–base and coordination properties of alkyl and aryl meso-substituted porphyrins are studied spectrophotometrically in nonaqueous solutions. It is found that the nature of the substituent greatly affects the basicity of ligands for porphyrins characterized by a flat structure of macrocycle. The electronic effects of substituents have a much weaker influence on the kinetics of complexing. These effects could be due to the opposite orientation of some factors: an increase in the basicity and stability of the N–H bonds of porphyrin reaction centers. Dissociation constants pK _b of the cationic forms of meso-substituted derivatives of porphyrin are measured. The values of pK _b are in good agreement with classic concepts of the nature of substituents, particularly those indirectly included in the macrocycle through phenyl buffer rings.     

A new PVC matrix membrane sensor for determination of praseodymium(III) ion based on bis(salicylaldehyde)thiocarbohydrazone as an ion carrier

The sufficient amounts of bis(salicylaldehyde) thiocarbohydrazone (STCH) as a lipophilic selective element (3%, w/w), sodium nitrobenzene (NB) as a plasticizer (64%, w/w), tetraphenyl borate (NaTPB) as an anionic additive (3%, w/w), and poly vinyl chloride (PVC) as a polymeric matrix (30%, w/w) was employed to form a PVC membrane of a new Pr³⁺ ions selective sensor to apply as an indicator electrode in analytical applications. The best electrode response was observed in the slope (19.5 ± 0.7 mV per decade) over a wide concentrations from lower (1.0 × 10^?6 mol L^–1) to higher (1.0 × 10^?2 mol L^–1) of Pr³⁺ ion solution with a detection limit of 8.5 × 10^–7 mol L^–1. This electrode showed the fast response time about 10 second for praseodymium ion concentration range of 1.0 × 10^–6 to 1.0 × 10^–2 mol L^–1, in the pH range of 2.3–7.9. The matched potential method was applied to study the selectivity of electrode toward Pr³⁺ ions in comparison with many common cations. The results showed the negligible disturbance of all other cations on the proposed praseodymium(III) electrode. The making sensor has been employed successfully as an indicator electrode in the potentiometric titration of praseodymium(III) solution with EDTA at pH 6.0. Moreover the applicability of the sensor was studied in determination of Pr³⁺ ion in mixtures of different ions.     

Synthesis of Au nanoparticles with Bi adlayers using glucose as dispersant

Well-dispersed Au/Bi nanoparticles with average size below 10 nm were prepared by using NaBH₄ to reduce HAuCl₄ with glucose as dispersant. The obtained Au/Bi NPs were well characterized by UV-Vis spectra, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and electrochemical measurements. The electrochemical study found that Bi adlayers on the surface of Au nanoparticles owns two kinds of surface structures, including a low coverage (2 × 2)-Bi adlayer and a close-packed (p × √3)-2 Bi adlayer due to the strong interaction between the two Bi layers and the below Au atoms, which is same with that bulk on Au surface.     

Application of the localized surface plasmon resonance of gold nanoparticles for the determination of 1,1-dimethylhydrazine in water: Toward green analytical chemistry

Localized surface plasmon resonance (LSPR) is an optical phenomena generated by light when it interacts with conductive nanoparticles that are smaller than the incident wavelength. In this work, we proposed a simple, fast, and green method for spectrophotometric determination of unsymmetrical 1,1-dimethylhydrazine (UDMH) based on LSPR property of gold nanoparticles (AuNPs). An LSPR band is produced via reduction of Au³⁺ ions in solution by UDMH as active reducing agent in the presence of cetyltrimethylammonium chloride as a capping agent. Some important parameters in the formation of LSPR including Au(III) concentration, pH, concentration of stabilizer, and reaction time were studied and optimized. Under optimum conditions, the LSPR intensity displays linear response with the increasing UDMH concentration in the range from 0.5–10 μg/mL at 550 nm with a detection limit of 0.2 μg/mL. Also, the relative standard deviation for ten replicate determination of 5.0 μg/mL of UDMH was 3%. Usage of AuNPs as new nontoxic reagent instead of hazardous reagents in the spectrophotometric determination of UDMH is a step toward green analytical chemistry. The proposed method was successfully applied for determination of UDMH in water and wastewater samples.