Showing papers in "Green and Sustainable Chemistry in 2012"

Green Synthesis of Silver Nanoparticles Using Extracts of Ananas comosus

Abstract: The biosynthesis of nanoparticles has been proposed as a cost effective and environmental friendly alternative to chemical and physical methods. Plant mediated synthesis of nanoparticles is a green chemistry approach that intercom nects nanotechnology and plant biotechnology. In the present study, synthesis of silver nanoparticles (AgNPs) or (Green-Silver) has been demonstrated using extracts of Ananas comosus reducing aqueous silver nitrate. The AgNPs were characterized by Ultraviolet-Visible (UV-vis) Spectrometer, Energy Dispersive X-ray Analysis (EDAX), Selected Area Diffraction Pattern (SAED) and High Resolution Transmission Electron Microscopy (HRTEM). TEM micrographs showed spherical particles with an average size of 12 nm. The XRD pattern showed the characteristic Bragg peaks of (111), (200), (220) and (311) facets of the face center cubic (fcc) silver nanoparticles and confirmed that these nanoparticles are crystalline in nature. The different types of antioxidants presented in the pineapple juice synergistically reduce the Ag metal ions, as each antioxidant is unique in terms of its structure and antioxidant function. The re- action process was simple for formation of silver nanoparticles and AgNPs presented in the aqueous medium were quite stable, even up to 4 months of incubation. This work proved the capability of using biomaterial towards the synthesis of silver nanoparticle, by adopting the principles of green chemistry.

Clay Modification by the Use of Organic Cations

Abstract: To render layered silicates miscible with polymer matrices, one must convert the normally hydrophilic silicate surface to an organophilic one, making the intercalation of polymeric chain between silicate layers possible. This can be done by ion-exchange reactions with cationic surfactants. Sodium montmorillonite (Na-MMT) was modified with several organic cationic surfactants. Organoclays with water soluble surfactants were prepared by the traditional cation exchange reaction. An alternative procedure was used to prepare organoclays with water insoluble salts. The basal spacing and thermal behavior of organoclays were characterized by X-ray diffraction, XRD and Thermogravimetric analysis, TGA respectively.

Functionalization of Polypropylene with High Dielectric Properties: Applications in Electric Energy Storage

Abstract: Biaxial-oriented polypropylene (BOPP) thin films are currently used as dielectrics in state-of-the-art capacitors that show many advantages, such as low energy loss and high breakdown strength, but a limited energy density ( 600 MV/m. The PP-OH dielectric demonstrates a linear reversible charge storage behavior with high releasing energy density > 7 J/cm3 (2 - 3 times of BOPP) after an applied electric field at E = 600 MV/m, without showing any significant increase of energy loss and remnant polarization at zero electric field. On the other hand, a cross-linked polypropylene (x-PP) exhibits an e ~ 3, which is independent of a wide range of temperatures and frequencies, slim polarization loops, high breakdown strength (E = 650 MV/m), narrow breakdown distribution, and reliable energy storage capacity > 5 J/cm3 (double that of state-of-the-art BOPP capacitors), without showing any increase in energy loss.

Comparative Study on Methods for Preparation of Gold Nanoparticles

Abstract: The gold nanoparticles were prepared in many methods, differed in reducing and dispersion agents and stability. The first solution was prepared by using potassium bitartrate as reducing agent and Polyethylene glycol as a dispersion factor. We got a solution of colloid gold with wine-red color that has been measured the particle size; it was between 50 - 200 nanometers. The second gold colloidal solution was prepared by using sodium citrate as a reducing agent and without adding a dispersion agent, the color of the final solution is dark grey, but this solution did not remain stable, deposition happened quickly and crystals separated from the solution. The third one was prepared by using sodium citrate as a reducing agent and the solution was heated to a certain temperature, and the color of the solution became dark red after several minutes. Either the fourth method has been prepared gold colloid solution by using potassium bitartrate as a reductant for the gold ion. We have noted that no reaction under normal conditions, while the reaction by heating the solution to high temperature, and when added poly vinyl pyrrolidone will lead to a solution of colloild gold with dark purple-red color and stable under normal conditions for a long time. We measured the particles size in this experiment; it was less than 100 nanometers. We conclude from the above that all the reducing agent needs to appropriate conditions to complete the process of reduction of gold ion, and to get the nano gold particles, therefore; these particles in the colloid solution need to dispersion factor to the survival of the particles widespread so that the solutions with certain concentrations of poly vinyl pyrrolidone can be proven in the process of stability of the gold colloid solution.

Investigation of a Simple and Cheap Source of a Natural Indicator for Acid-Base Titration: Effects of System Conditions on Natural Indicators

Abstract: This study investigated a natural indicator for acid-base titration which is extracted from guinea corn leaves popularly called “waakye leaves” in Ghana. Four types of acid-base titration were studied: strong acid versus (v/s) strong base, strong acid versus weak base, weak acid versus strong base, and weak acid versus weak base. The indicator color change, pH range and the average titre values were determined for each type of acid-base titration. These values were comparable to those obtained from three standard indicators: methyl orange, methyl red and phenolphthalein. Total flavonoids (TF) and condensed tannin (CT) from the crude leaves extract were determined which might be the major reasons for the activity of the extract as an indicator for simple acid-base titration. The authors suggest that the natural indicator is cheap, available, simple to extract, user and environmentally friendly and could be an excellent replacement for standard indicators.

Styrene Epoxidation in Aqueous over Triazine-Based Microporous Polymeric Network as a Metal-Free Catalyst

Abstract: Tirazine based microporous polymeric (TMP) network was found to be an efficient metal-free catalyst for the epoxidation of styrene. The reactions were performed in water as an environmentally benign medium using H2O2 as a green oxidant at ambient temperature. The reaction afforded higher yield with 90% conversion of styrene and 98% selectivity to styrene oxide in 6 h. The triazine based microporous polymeric network can be readily recovered and reused up to 4 cycles without significant loss in catalytic activity and selectivity.

Synthesis of Novel Hexathiolated Squalene and Its Thiol-Ene Photopolymerization with Unsaturated Monomers

Abstract: In this work is described the synthesis of a multifunctional thiolated squalene. Thiol-ene coupling reactions were employed to functionalize the six double bonds of squalene, using thiolacetic acid. Hydrolysis of the resulting thioacetates, rendered the corresponding hexathiolated squalene SQ6SH. This compound was further photopolymerized separately with triallyl cyanurate, pentaerythritol triacrylate and diethyleneglycol divinyl ether. Real Time FTIR kinetics revealed that homopolymerization of the ene monomers took place in addition to the thiol-ene photopolymerization. Flexible films were obtained when SQ6SH was photopolymerized in bulk with the above mentioned unsaturated monomers.

Ultrasonically Assisted Regioselective Nitration of Aromatic Compounds in Presence of Certain Group V and VI Metal Salts

Abstract: Ultrasonically assisted nitration reactions (USANR) with anilides, moderately activated and non-activated aromatic compounds underwent smoothly and afforded good yields of products with high regio selectivity. Observed longer reaction times (6 - 8 hrs.) in metal catalyzed reactions reduced to (1 - 2 hrs.) under sonication. When ortho position is blocked para derivatives are obtained, and ortho nitro products are obtained when para position is blocked. In case of USANR of aromatic carbonyl and related compounds the effect of sonication is much more effective. The reactions could be completed only in few minutes.

Crystalline Manganese Carbonate a Green Catalyst for Biodiesel Production

Abstract: Crystalline manganese carbonate was found to be a versatile green, non corrosive and environmental friendly catalyst for transesterification of vegetable oils. Its use as catalyst in the transesterification process involving methanol and vegetable oils (palm, rapeseed, groundnut, coconut and caster oils) resulted in a conversion rate of 80% - 95% in the production of biodiesel. The chemical composition of the obtained biodiesel was studied by GC-MS analysis and showed the presence of linoleic, oleic, palmitic, and stearic acids methyl esters to be the major compounds. Manganese carbonate in comparison with other solid catalysts was found to decrease the reaction time and temperature concomitant with an increase of biodiesel yield. Finally, the effect of various parameters including methanol quantity, catalyst amount, reaction time and temperatures on the production of biodiesel was investigated.

Environmentally Benign Synthetic Protocol for O-Alkylation of β-Naphthols and Hydroxy Pyridines in Aqueous Micellar Media

Abstract: Ultrasonic and microwave-assisted practical methods have been developed for the O-alkylation of aryl (β-naphthols) and Heteroaryl (hydroxy pyridines) in aqueous surfactant media in good to excellent yields. The developed methods are simple, efficient, economical and environmentally safe. Our novel methods describe a set of green methods to Wil-liamson synthesis.

Synthesis, Characterization and Application of ZS/HMS Catalyst in the Esterification of Gossypol

Abstract: A solid acid catalyst of zirconium sulfate (ZS) on a pure hexagonal mesoporous silica (HMS) sieve was prepared and characterized by small angle X-ray diffraction, NH3-temperature programmed desorption, and thermogravimetric analysis. The obtained ZS/HMS catalyst displayed a typical mesoporous structure, ZS was well dispersed on the HMS support, and the acidity increased with the amount of ZS loading. Gossypol was extracted from cottonseed cake with acetone as solvent, and then the gossypol solution was esterified with ZS/HMS as catalyst to yield products of acetic acid gossypol. Under the optimal conditions, the conversion efficiency of gossypol was as high as 96.7%.

Material-Efficient Utilization of Waste Oils—Biodegradability and Other Chemical Properties of Vegetable Recycling Oils

Abstract: Material efficiency is nowadays an essential topic to promote the sustainable use of natural resources, waste materials and industrial by-products, in agreement with the principle of sustainable development and LCA (life cycle assessment). In this research it was determined the biodegradation of used vegetable oil based products and their important physico- chemical properties for their suitability in different applications such as chain oil in the forestry equipment and mold oil in concrete casting etc. Biodegradability is a measure of the ecological nature of products, and thus from an environ- mental point of view, is the most important evaluated property in this research. As a result, all measured properties of the studied recycled vegetable oils show that the products are environmentally friendly. Two types of vegetable oil were studied; three chain oils and two mold oils. The degree of biodegradation (BOD28) of the mold oils, was about 77 % and the biodegradation of chain oils was about 60% - 62%. In addition, this paper also presents a process outline for manu- facturing recycling vegetable oils.

Production of Carbon Nanotubes and Hydrogen Catalyzed with Ni/MCM-41 Catalysts

Abstract: Methane catalytic decomposition (MCD) over Ni/MCM-41 catalysts was tested in a microreactor to simultaneously produce hydrogen and carbon nanotubes (CNTs). The methane conversion reached 30% to 47% at a moderate temperature range from 400°C to 600°C and the catalytic activity of the catalysts remains stable during 500 min steam on time. CNTs were chiefly formed through tip-growth mode, due to the weak interaction between the metallic Ni and the support. Most of the Ni particles are located on the tip of the produced CNTs, which avoids rapid deactivation of the catalyst resulted from carbon encapsulation. Large Ni particles usually lead to the formation of CNTs with big diameter. During the reaction, the shape of Ni particles changed from pseudo-sphere to diamond-like. All the CNTs consist of multiple layer walls and are curved in certain degree.

Aspects on the Mechanism of the 1-Phenyl-1H-pyrazolo[3,4-b]quinoxaline Formation

Abstract: Condensation of D-glucose, o-phenylenediamine and N,N-benzylphenylhydrazine hydrochloride (NNBPHH) in a one-pot reaction, or condensation of 2-(D-arabino-tetritol-1-yl) quinoxaline and NNBPHH, gave 3-(D-erythro-glycerol-1- yl)-1-phenyl-1H-pyrazolo[3,4-b]quinoxaline. The structure of the latter was determined by 1H NMR spectroscopy and by synthesis using phenylhydrazine hydrochloride instead of NNBPHH. Condensation of D-glucose and 4,5-dichloro-o-phenylenediamine gave 6,7-dichloro-2-(D-arabino-tetritol-1-yl)quinoxaline, which upon condensation with NNBPHH gave the corresponding 6,7-dichloro-3-(D-erythro-glycerol-1-yl)-1-phenyl-1H-pyrazolo[3,4-b]quinoxaline. The structure and mechanism of formation of these compounds are discussed.

Composition of the Volatile Components Extracted from the Roots of Scorzonera undulata ssp deliciosa (Guiss) Maire: From Algeria

Abstract: The chemical composition of the volatile components of the dried roots of Scorzonera undulata ssp deliciosa collected from Algeria was determined by GC and GC/MS. The obtained results showed that the extracted oil contained nine fatty acids. The major compounds were hexadecanoic acid (42.2%), n-tetradecanoic acid (16.1%), 9-octadecenoic acid (7.7%) and 9-hexadecenoic acid (4.5%).

Effect of a High Silver Stress on the Element Transfers from a Smectite-Type Clay Substrate to Plants

Abstract: Two species of radishes, Raphanus sativus and Raphanus raphanistrum, were grown in the laboratory in the same substrate consisting of a smectite-type clay, which was watered at the beginning of the experience with 50 ml of a solution containing either none or 1000, 2000 or 4000 mg/L of AgNO3, respectively. Occurrence of the toxic metal in the substrate outlines higher element uptakes by the cultivated species Raphanus sativus than by the wild species Raphanus raphanistrum, except for the highest degree of Ag pollution. After a one-month growth in the Ag-polluted substrate, Raphanus sativus was depleted in most of the major, trace and rare-earth elements, except for Al, Fe, Th, Ag and U that increased in the radishes from substrate polluted by 2000 mg/L of AgNO3, and Sr, Co, Ni, U and Ag that increased in the radishes from substrate polluted by 4000 mg/L of AgNO3. Raphanus raphanistrum was enriched in all elements except Si, Na, Rb and K in the polluted substrate. The uptake was monitored by a cation-exchange process in the rhy-zosphere between mineral particles and the watering solution in the presence of various enzymes with specific activities that induced a variable uptake with the REEs being even fractionated. These activities most probably depend on combined factors, such as the plant species, and the chemical and physical properties of the substrate. The results obtained here reveal also that accumulation of nutrient elements and others in the plants is not uniform at a given Ag pollution of the substrate and therefore at a given Ag contamination in the same plant species.

Research and Optimization of Technological Process Based on Fermentation for Production of Seaweed Feed

Abstract: This paper for the purpose of utilization, conducted a study of technological process of producing animal feed by fermenting seaweed waste. Anaerobic fermentation, which can improve the contents of protein and polysaccharide in seaweed waste, proved to be an available method to improve the nutritional value of animal feed by using seaweed waste. Also effects of different additives and fermentation time on the fermentation products was compared, combined CCRD with neural network to optimize these factors, the predict model among all factors was established, also obtained the optimal fermentation process.

A Novel Immunological Technique for Detection of Gramicidin (S) Producing Bacteria

Abstract: A serological kit was prepared for the first time to detect bacteria that produce Gramicidin (S). Since, an immunocomplex of antibiotic Gramicidin (S) was prepared followed by immunonization of laboratory animales to obtain specific antibodies in their serum. Serial dilutions of the prepared antibodies were tested directly against samples of bacteria and compared with control samples, which include bacteria that produce Gramicidin (S) (as a positive control) and the bacteria that does not produce Gramicidin (S) (as a negative control) depending slide method after the incubation of bacteria in a suitable media for 3 - 4 hours at 37°C. The prepared kites were evaluated in reference Laboratories and they proved to be highly sensitive (100%), specific (100%), more economic and reliable procedure, in addition to its stability for more than one year. It was the first time to prepare a kit for detection of bacteria which produce Gramicidin (S) directly within few minutes.

Some New Questions about the Seasonal Decrease of the Ozone Layer

Abstract: The depletion-recovery cycle of the ozone layer is explained on the basis of the magnetic properties of oxygen, ozone, nitrogen oxides and chlorine combinations, which upon interaction with the Earth’s magnetic field, give rise to gaseous fluxes polar- and equatorial-wards.

Non Equilibrium Plasma Assisted Conversion of Fossil Fuels without CO 2 Release

Abstract: A new method of extracting the chemical energy from hydrocarbon fuels without the release of carbon dioxide is demonstrated. This novel approach has been made possible with non- equilibrium plasma. In addition to CO2 and CO, there is a lesser known carbon oxide called carbon suboxide which can be polymerized to form thermodynamically stable substances. A process of converting hydrocarbon fuels to hydrogen and carbon suboxide without the release of carbon dioxide using dielectric barrier discharge (DBD) plasma is described in detail. Thermodynamic calculations show energy of up to 78% for the production of hydrogen and carbon suboxide. Results from the analyses of the condensed by-products of the hydrocarbon conversion process are also discussed.