A porous ruthenium silica catalyst modified with amino benzoic acid for the oxidation of butanol with molecular oxygen

Silica was extracted from rice husk (RH) and modified with ruthenium and amino benzoic acid. The catalysts RH–Ru and RH–Ru–A (incorporated with 5% of 4-(methylamino)benzoic acid) were synthesized from rice husk via solvent extraction and sol–gel technique. XRD diffractogram showed both catalysts were amorphous. BET results showed that the surface area of RH–Ru–A (73.9 m² g⁻¹) was smaller compared with RH–Ru (138 m² g⁻¹). After calcinations at 700 °C, RH–Ru-700 and RH–Ru–A-700 showed a lower specific surface area, i.e. 21.8 and 19.0 m² g⁻¹, respectively. The SEM micrograph of RH–Ru-700 showed the presence of elongated nano fibers, while RH–Ru–A-700 showed the presence of large regular pore structures. RH–Ru and RH–Ru–A were used as catalyst for the oxidation of 1-butanol with molecular oxygen as the oxidant. The oxidation yielded only one product, i.e. 1-butanal. Although the yield of 1-butanal was less than 10% both catalyst showed great potential for the oxidation of primary alcohols into aldehydes at moderate reaction conditions. A plausible mechanism was suggested for the catalyzed oxidation.     

Oxidation of Carbon Monoxide Over SBA-15-Confined Copper,Palladium and Iridium Nanocatalysts

Abstract  

Copper, palladium and iridium nanoparticles were synthesised within the pore channels of selectively grafted mesoporous silica SBA-15. The support and catalysts were characterised by different techniques. The synthesized catalyst were able to catalyse oxidation of carbon monoxide with activity values as high as 7.0 × 10⁻³ mmol g⁻¹ cat s⁻¹ at 353 K. Carbon monoxide conversion was found to increase with decreasing nano particle size.     

Electroanalysis of urinary l-dopa using tyrosinase immobilized on gold nanoelectrode ensembles

The performance of an amperometric biosensor constructed by associating tyrosinase (Tyr) enzyme with the advantages of a 3D gold nanoelectrode ensemble (GNEE) is evaluated in a flow-injection analysis (FIA) system for the analysis of l-dopa. GNEEs were fabricated by electroless deposition of the metal within the pores of polycarbonate track-etched membranes. A simple solvent etching procedure based on the solubility of polycarbonate membranes is adopted for the fabrication of the 3D GNEE. Afterward, enzyme was immobilized onto preformed self-assembled monolayers of cysteamine on the 3D GNEEs (GNEE-Tyr) via cross-linking with glutaraldehyde. The experimental conditions of the FIA system, such as the detection potential (−0.200 V vs. Ag/AgCl) and flow rates (1.0 mL min⁻¹) were optimized. Analytical responses for l-dopa were obtained in a wide concentration range between 1 × 10⁻⁸ mol L⁻¹ and 1 × 10⁻² mol L⁻¹. The limit of quantification was found to be 1 × 10⁻⁸ mol L⁻¹ with a resultant % RSD of 7.23% (n = 5). The limit of detection was found to be 1 × 10⁻⁹ mol L⁻¹ (S/N = 3). The common interfering compounds, namely glucose (10 mmol L⁻¹), ascorbic acid (10 mmol L⁻¹), and urea (10 mmol L⁻¹), were studied. The recovery of l-dopa (1 × 10⁻⁷ mol L⁻¹) from spiked urine samples was found to be 96%. Therefore, the developed method is adequate to be applied in the clinical analysis.     

Synthesis of mesoporous silica templated by Pluronic F68 and its application in the immobilization of lipase

Mesoporous silica templated by Pluronic F68 was synthesized and characterized by TEM, N₂ adsorption–desorption isotherms and FT–IR spectra. The sample had a high specific surface area (761 m² g⁻¹) and the mean pore diameter was 4.7 nm, indicating that it can be used as porcine pancreatic lipase (PPL) support. The physical adsorption of PPL on this mesoporous material in phosphate buffer solution with different pH values has been studied. The maximum adsorbed amount was observed at pH 7.0 and amounted to 826 mg g⁻¹ and the maximum activity value of immobilized PPL was 227 μmol g⁻¹ min⁻¹. The optimal pH and temperature of the hydrolysis of triacetin for the immobilized PPL were at 8.0 and 45 °C, while they were at pH 7.0 and 35 °C for free PPL. The immobilized PPL showed excellent adaptability in higher pH and excellent heat resistance compared to free PPL. The retained activity of immobilized PPL was found to be ca. 50% of its original activity after the 5th reuse.     

Synthesis of high surface area γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> as an efficient catalyst support for dehydrogenation of n-dodecane

In this work mesoporous nanocrystalline γ-Al₂O₃ has been synthesized by a three step (hydrolysis, condensation and hydrothermal treatment) sol–gel procedure in nitric acid medium with cationic surfactant (hexadecyltrimethyl ammonium bromide) as template. The prepared sample was employed as a carrier for the n-dodecane dehydrogenation catalyst. The synthesized samples were characterized by X-ray diffraction (XRD), N₂ adsorption (BET), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric (TG) and temperature programmed reduction (TPR) techniques. The nitrogen adsorption analysis showed that the samples possessed mesoporous structure with high specific surface areas larger than 370 m² g⁻¹ and pore volumes larger than 1.5 cm³ g⁻¹. The prepared samples also showed a high thermal stability up to 750 °C which is important for carrier of heterogeneous catalysts. The results of catalyst testing in the dehydrogenation reaction of n-dodecane confirmed that the synthesized support has a good potential to function as a carrier for n-dodecane dehydrogenation catalysts.     

Effect of specific surface area on oxygen storage capacity (OSC) and methane steam reforming reactivity of CeO<Subscript>2</Subscript>

It was found from the work that the specific surface area of ceria presents an important role on the oxygen storage capacity (OSC), the reactivity toward methane steam reforming, and the resistance toward carbon formation of this material. After calcination at 900°C, ceria prepared by surfactant-assisted method (SF) was observed from the present work to have significantly higher surface area than those prepared by templating (TP) and precipitation (PP) methods; this material showed strong OSC with good reforming reactivity in terms of thermal stability and resistance toward carbon formation compared to others. In detail, the degree of OSC was measured by the number of hydrogen uptake from the temperature programmed reduction (TPR). It was found that the value of hydrogen uptake from the TPR-1 of ceria prepared by SF was 2084 mmol g⁻¹, whereas those of ceria prepared by TP and PP were 1724 and 781 mmol g⁻¹, respectively. In addition, it was also proven in the present work that the OSC of these materials are reversible, according to the temperature programmed oxidation (TPO) and the second time temperature programmed reduction (TPR-2) results. According to the reactivity toward methane steam reforming, after purging in 3 kPa methane and 9 kPa steam at 900°C for 8 h, the methane conversion at steady state of ceria prepared by SF was approximately 38% with very low amount of carbon formed on the surface (0.16 mmol g⁻¹), whereas those of ceria prepared by TP and PP were 22% (with the amount of carbon formation of 0.30 mmol g⁻¹) and 13% (with the amount of carbon formation of 0.33 mmol g⁻¹), respectively.     

Ring-opening polymerization of γ-glycidoxypropyltrimethoxysilane catalyzed by multi-metal cyanide catalyst

Ring-opening polymerizations of γ-glycidoxypropyltrimethoxysilane (GPTMS) were carried out by using multi-metal cyanide (MMC) catalyst and the synthesized homopolymer was a comb-shaped polymer with regular structure. The structure of the polymer obtained (P-GPTMS) was characterized by FTIR, ¹H-NMR, and ²⁹Si-NMR spectroscopy, and the molecular weight and its distribution were analyzed by size-exclusion chromatography with multi-angle laser light scattering (SEC-MALLS). The thermal behavior of P-GPTMS was investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). P-GPTMS with high molecular weight (M _n = 18,000–80,000) and narrow molecular weight distribution (1.10–1.35) were synthesized when the dosage of MMC catalyst was 0.1% and polymerization temperature was 130 °C. The molecular weight of the product could be adjusted by controlling the polymerization time. The T _g of P-GPTMS is in the range of −34 to −30 °C. On the basis of the TGA data, the decomposition rate of P-GPTMS reached its peak at 374.14 °C and the entire decomposition stopped at 600 °C.     

Polymeric ionic liquid membranes as electrolytes for lithium battery applications

A new kind of polymeric ionic liquid (PIL) membrane based on guanidinium ionic liquid (IL) with ester and alkyl groups was synthesized. On addition of guanidinium IL, lithium salt, and nano silica in the PIL, a gel PIL electrolyte was prepared. The chemical structure of the PIL and the properties of gel electrolytes were characterized. The ionic conductivity of the gel electrolyte was 5.07 × 10⁻⁶ and 1.92 × 10⁻⁴ S cm⁻¹ at 30 and 80 °C, respectively. The gel electrolyte had a low glass transition temperature (T _g ) under −60 °C and a high decomposition temperature of 310 °C. When the gel polymer electrolyte was used in the Li/LiFePO₄ cell, the cell delivered 142 mAh g⁻¹ after 40 cycles at the current rates of 0.1 C and 80 °C.     

Study on simultaneous measurements of trace gallium(III) and germanium(IV) by adsorptive stripping voltammetry using mercury film electrode

Simultaneous adsorptive stripping voltammetric method for the determination of trace gallium(III) and germanium(IV) based on the adsorption of gallium(III) and germanium(IV)-catechol complex on the cyclic renewable mercury film silver based electrode (Hg(Ag)FE) is presented. The calibration graph is linear from 1.25 nM (0.09 μg L⁻¹) to 90 nM (6.27 μg L⁻¹) with correlation coefficient of 0.999 for gallium and from 2.5 nM (0.18 μg L⁻¹) to 160 nM (12.3 μg L⁻¹) with correlation coefficient of 0.998 for germanium for a preconcentration time of 30 s. The detection limit for a preconcentration time of 60 s is as low as 25 ng L⁻¹ for gallium and 58 ng L⁻¹ for germanium. The proposed method was successfully applied by studying the natural samples and simultaneous recovery of Ga(III) and Ge(IV) from spiked water and sediment samples.     

Studies of some operating parameters and cyclic voltammetry for a direct ethanol fuel cell

A direct ethanol fuel cell (DEFC) of 5 cm² membrane-electrode area was studied systematically by varying the catalyst loading, ethanol concentration, temperature and different Pt based electro-catalysts (Pt–Ru/C, Pt-black High Surface Area (HSA) and Pt/C). A combination of 2 M ethanol at the anode, pure oxygen at the cathode, 1 mg cm⁻² of Pt–Ru/C (40%:20%) as the anode and 1 mg cm⁻² of Pt-black as the cathode gave a maximum open circuit voltage (OCV) of 0.815 V, a short circuit current density of 27.90 mA cm⁻² and a power density of 10.3 mW cm⁻². The optimum temperatures of the anode and cathode were determined as 90 °C and 60 °C, respectively. The power density increased with increase in ethanol concentration and catalyst loading at the anode and cathode. However, the power density decreased slightly beyond 2 M ethanol concentration and 1 mg cm⁻² catalyst loading at the anode and cathode. These results were validated using cyclic voltammetry at single electrodes under similar conditions to those of the DEFC.     

Horizontal nutrient fluxes and food safety in urban and peri-urban vegetable and millet cultivation of Niamey,Niger

Urban and peri-urban agriculture (UPA) has often been accused of being nutrient inefficient and producing negative externalities. To investigate these problems for the West African capital Niamey (Niger), nutrient inputs through fertilizer and manure to 10 vegetable gardens and 9 millet fields and nutrient offtakes through harvests were quantified during 24 months, and contamination of irrigation water and selected vegetables with faecal pathogens and heavy metals was determined. Annual partial horizontal balances for carbon (C), nitrogen (N), phosphorus (P) and potassium (K) amounted to 9,936 kg C ha⁻¹, 1,133 kg N ha⁻¹, 223 kg P ha⁻¹ and 312 kg K ha⁻¹ in high input vegetable gardens as opposed to 9,580 kg C ha⁻¹, 290 kg N ha⁻¹, 125 kg P ha⁻¹ and 351 kg K ha⁻¹ in low input gardens. In high input millet fields, annual surpluses of 259 kg C ha⁻¹, 126 kg N ha⁻¹, 20 kg P ha⁻¹ and 0.4 kg K ha⁻¹ were recorded, whereas surpluses of 12 kg C ha⁻¹, 17 kg N ha⁻¹, and deficits of −3 kg P ha⁻¹ and −3 kg K ha⁻¹ were determined for low input fields. Counts of Salmonella spp. and Escherichia coli yielded above threshold contamination levels of 7.2 × 10⁴ CFU 25 g⁻¹ and 3.9 × 10⁴ CFU g⁻¹ in lettuce irrigated with river water and fertilized with animal manure. Salmonella counts averaged 9.8 × 10⁴ CFU 25 g⁻¹ and E. coli 0.6 × 10⁴ CFU g⁻¹ for lettuce irrigated with wastewater, while these pathogens were not detected on vegetables irrigated with pond water. These results underline the need for urban gardeners to better adjust the nutrients applied to crop requirements which might also reduce nutrient accumulations in the soil and further in the edibles parts of the vegetables. Appropriate pre-treatment of irrigation water would help improve the quality of the latter and enhance the food safety of vegetables determined for the urban markets.     

A Novel Catalyst Type Containing Noble Metal Nanoparticles Supported on Mesoporous Carbon: Synthesis,Characterization and Catalytic Properties

We report on a method for the controlled synthesis of a new type of high specific surface area mesoporous carbons denoted as the CMH family. By using mixtures of colloidal silica particles as templates it was possible to synthesize samples exhibiting 1,630 m² g⁻¹ specific surface area and 4.37 cm³ g⁻¹ pore volume. CMH materials exhibit high thermal stability in oxygen and can be used as catalyst supports. This function was demonstrated by synthesizing Pt/CMH and Rh/CMH catalysts and testing them in the hydrogenation of cyclohexene. We have found Pt/CMH to be more stable and easier to regenerate than Rh/CMH.     

Zn<Superscript>2+</Superscript>-exchange kinetics and antimicrobial properties of synthetic zirconium umbite (K<Subscript>2</Subscript>ZrSi<Subscript>3</Subscript>O<Subscript>9</Subscript>·H<Subscript>2</Subscript>O)

Zirconium umbite, K₂ZrSi₃O₉·H₂O, is a microporous framework ion exchanger whose potential as a carrier for Zn²⁺ ions in antimicrobial formulations has not yet been investigated. Accordingly, batch Zn²⁺-exchange kinetics of synthetic zirconium umbite (K-UM) and the subsequent antimicrobial action of the zinc-bearing phase (Zn-UM) against Staphylococcus aureus and Escherichia coli are reported. Nonstoicheiometric over-exchange of Zn²⁺ for K⁺ was observed and attributed to hydrolysis and complexation reactions of Zn²⁺ within the umbite framework. The exchange process, which was described by a simple pseudo-first-order model (k ₁ = 2.69 × 10⁻⁴ min⁻¹, R ² = 0.992), did not achieve equilibrium within 120 h at 25 °C, by which time the uptake of zinc was found to be 1.04 mmol g⁻¹. The minimal bactericidal concentrations of Zn-UM for E. coli and S. aureus were found to be >10 g cm³ and <1.0 g cm³, respectively.     

Activity of Nitrogen Containing Carbon Nanotubes in Base Catalyzed Knoevenagel Condensation

The catalytic activity of Nitrogen containing Carbon Nanotubes (NCNT), grown from acetonitrile or pyridine over supported Fe-, Co or Ni catalysts at various conditions, were tested for the base catalyzed Knoevenagel condensation of benzaldehyde and ethylcyanoacetate. All NCNT displayed activity for the reaction with initial turn over frequencies between 9 × 10⁻³ and 5 × 10⁻² s⁻¹ which is comparable with to those of activated basic carbons and a rehydrated hydrotalcite. Furthermore, the initial activity per gram of catalyst of NCNT was related to the amount of pyridinic type nitrogen in the NCNT. However, the reaction rate decreased with time on stream which was explained by competitive adsorption of reactant and product. The reaction rate can be described using Langmuir–Hinshelwood type kinetics including product adsorption.     

Electrochemical detection of the neomycin phosphotransferase gene (NPT-II) in transgenic plants with a novel DNA biosensor

A novel DNA electrochemical biosensor is described for the detection of neomycin phosphotransferase gene (NPT-II), a selection marker for transgenic plants. A thiol-modified capture probe immobilized onto the surface of a gold electrode and a biotinylated signaling probe were designed to be complementary to target regions of NPT-II flanked by PCR primers to eliminate false-positive signals from non-specific PCR products. The electrochemical assay of hybrids on the electrode surface was evaluated by means of both cyclic voltammetry (CV) and square wave voltammetry (SWV) after the coupling of biotinylated catalase with streptavidin-modified hybrids based on dendritic signal magnification and subsequent formation of polymerized aniline (PAn). It has been revealed that the sensor showed a linear increase within the target concentration (1.0–100 × 10⁻⁶ mmol L⁻¹). The limit of detection was about 0.2 × 10⁻⁶ mmol L⁻¹ and the specificity was enhanced significantly.     

Lipase-Catalyzed Synthesis of Saccharide–Fatty Acid Esters Using Suspensions of Saccharide Crystals in Solvent-Free Media

Saccharide–fatty acid esters, important biobased and biodegradable emulsifiers in foods, cosmetics, and pharmaceuticals, were produced with high yields and productivity via immobilized Rhizomucor miehei lipase-catalyzed esterification in solvent-free systems at 65 °C. Preliminary experiments demonstrated high rates of reaction occurred in the presence of acetone near or above its boiling point, due to the formation of 10–200 μm suspensions of saccharide particles. Subsequently, a two-step process was developed to produce a solvent-free supersaturated solution of 1.5–2.0 wt% saccharide that remained stable for ≥10–12 h. The solvent-free suspensions were used in a bioreactor system at 65 °C, consisting of a reservoir open to the atmosphere that contained molecular sieves, a peristaltic pump, and a packed bed bioreactor, operated under continuous recirculation. At 10 h intervals, suspensions were re-formed by treating the substrate/product mixture with additional acyl acceptor and applying strong agitation. Using this system and approach, a product mixture containing 88% fructose oleate was formed, of which 92% was monoester, within 6 days. This equates to a productivity of 0.2 mmol h⁻¹ g⁻¹, which is similar to values reported for synthesis in the presence of solvent.     

Discharge characteristics of silver vanadium oxide cathodes

The discharge characteristics of silver vanadium oxide (SVO) as a cathode in lithium–silver vanadium oxide (Li–SVO) primary battery was studied under various operating conditions. The cathode yielded a capacity of 260 mAh g⁻¹ at a current density of 0.08 mA cm⁻², although the theoretical capacity of this material is 315 mAh g⁻¹. The pulse discharge characteristics were studied under conditions that simulate battery operation inside an implantable cardio-verter defibrillator (ICD). The variation of the ohmic resistance of the system was studied as a function of depth of discharge. Rate capability and impedance studies indicated high diffusion limitations for this system especially at high depth of discharge. Morphological changes during discharge were also discussed using scanning electron microscopic studies.     

A simple method for electroanalytical determination of ceftiofur in UHT milk samples using square-wave voltammetry technique

A simple electroanalytical method was developed to determine the antibiotic ceftiofur (CF) in milk. The method is based on the adsorptive accumulation of the drug on a hanging mercury-drop electrode (HMDE) and the accompanying initiation of a negative square wave, which yielded well-defined cathodic peaks at −0.60 V (1C) and −0.91 V (2C) vs. Ag/AgCl. Calibration graphs were constructed and statistical parameters were evaluated. At pH 2.5, the square-wave voltammetry method revealed linearity from 52.4 to 524 ng mL⁻¹ (r = 0.997), which is in accordance with the tolerance level of 100 ng mL⁻¹ for CF as a residue in bovine milk established by the Food and Drug Administration (FDA) and the European Union. The limits of detection and quantification were 1.86 and 6.20 ng mL⁻¹, respectively. The method was tested to determine CF in spiked milk samples using HPLC as reference method.     

PAHs,PCBs, PBDEs and Pesticides in Cold-Pressed Vegetable Oils

The aim of this study was to investigate levels of polychlorinated biphenyls (marker and dioxin-like congeners), polycyclic aromatic hydrocarbons (EPA 15 + 1), polybrominated diphenyl ethers (14 predominant congeners) and pesticides (74 compounds) in various cold-pressed vegetable oils. Poppy seed oil, rapeseed oil, sesame seed oil, pumpkinseed oil, hempseed oil, linaire oil, borage oil and evening star oil were investigated. Results of this study revealed that concentrations of PCBs, PBDEs and PAHs were low in majority of the investigated samples. However, high concentrations of organophosphorus insecticides were found. Chlorpyrifos methyl and pirimiphos methyl were the pesticide residues most commonly found in the studied oils. Concentration of 15 + 1 EPA PAHs was within the 17.85–37.16 μg kg⁻¹ range, concentration of (marker) PCBs varied from 127 to 24,882 pg g⁻¹, dioxin-like TEQ values were below 0.1 pg TEQ g⁻¹. Concentration of PBDEs was below LOQ in most cases.     

Potential of denitrification and nitrous oxide production from agricultural soil profiles (Seine Basin,France)

The denitrification process and the associated nitrous oxide (N₂O) production in soils have been poorly documented, especially in terms of soil profiles; most work on denitrification has concentrated on the upper layer (first 20 cm). The objectives of this study were to examine the origin of N₂O emission and the effects of in situ controlling factors on soil denitrification and N₂O production, also allowing the (N₂O production)/(NO₃ ⁻–N reduction) ratio to be determined through (1) the position on a slope reaching a river and (2) the depth (soil horizons: 10–30 and 90–110 cm). In 2009 and 2010, slurry batch experiments combined with molecular investigations of bacterial communities were conducted in a corn field and an adjacent riparian buffer strip. Denitrification rates, ranging from 0.30 μg NO₃ ⁻–N g⁻¹ dry soil h⁻¹ to 1.44 μg NO₃ ⁻–N g⁻¹ dry soil h⁻¹, showed no significant variation along the slope and depth. N₂O production assessed simultaneously differed considerably over the depth and ranged from 0.4 ng N₂O–N g⁻¹ dry soil h⁻¹ in subsoils (the 90–110-cm layer) to 155.1 ng N₂O–N g⁻¹ dry soil h⁻¹ in the topsoils (the 10–30-cm layer). In the topsoils, N₂O–N production accounted for 8.5–48.0% of the total denitrified NO₃ ⁻–N, but for less than 1% in the subsoils. Similarly, N₂O-consuming bacterial communities from the subsoils greatly differed from those of the topsoils, as revealed by their nosZ DGGE fingerprints. High N₂O-SPPR (nitrous oxide semi potential production rates) in comparison to NO₃-SPDR (nitrate semi potential reduction rates) for the topsoils indicated significant potential greenhouse N₂O gas production, whereas lower horizons could play a role in fully removing nitrate into inert atmospheric N₂. In terms of landscape management, these results call for caution in rehabilitating or constructing buffer zones for agricultural nitrate removal.