Showing papers in "Green and Sustainable Chemistry in 2014"

A Review of Ionic Liquids, Their Limits and Applications

Abstract: Since environmental pollution caused by chemical and energy industries has increased for several decades, there is a social expectation that scientists and engineers try to design sustainable chemical processes, to generate less hazardous materials and more environmentally friendly sources of energy production. In this review the roles of Ionic Liquids (ILs) and IL based solvent systems as proposed alternative for conventional organic solvents are described. Since there are already many reviews on benefits of ILs, after a very brief review of ILs we focus mostly on aspects that are not covered in other reviews, in particular the known limits of these solvents. In addition, different methods to measure the physicochemical properties relevant to their use in energy storage applications such as fuel cells and batteries are introduced. The physicochemical properties that are reviewed are thermal properties, conductivity and chemical reactivity. The focus of the review is on the literature after 2008, with the exception of some important historic articles on ILs.

Efficient Extraction of Agarose from Red Algae Using Ionic Liquids

Abstract: We explored the possibility of using ionic liquids (ILs) as medium for efficient extraction of agarose via dissolution of red algae under varying conditions of heating or microwave irradiation. As compared to conventional methods, a very high extraction yield of good quality agarose (as high as 39 wt%) could be achieved depending upon the nature of used IL and applied experimental conditions. Purity of extracted agarose was confirmed from various spectral and analytical techniques, such as 1H and 13C NMR, FTIR, circular dichroism (CD), gel permeation chromatography (GPC) and thermogravimetric analysis (TGA). The physicochemical properties, such as gelling or melting temperature, viscosity and gel strength of extracted agarose hydrogels have been measured and compared with the agarose obtained from similar source reported in the literature. ILs were recovered after the extraction of agarose and were reused for further extraction experiments. % Recycling and extraction ability of recycled ILs in different cycles have been measured. The developed extraction process of utilizing ILs as medium is easy, simple and highly efficient as compared to the conventional methods of agarose extraction from algae.

High Performance Recycling of Polymers by Means of Their Fluorescence Lifetimes

Abstract: Technical polymers could be identified by means of their remarkably strong auto fluorescence. The time constants of this fluorescence proved to be characteristic for the individual polymers and can be economically determined by integrating procedures. The thus obtained unequivocal identification is presented for their sorting for recycling. Furthermore, polymeric materials were doped with fluorescent dyes allowing a fine-classification of special batches.

Facile and Efficient Method for Synthesis of Benzimidazole Derivatives Catalyzed by Zinc Triflate

Abstract: We report the synthesis of benzimidazole derivatives using zinc triflate as an efficient catalyst. One-pot synthesis of 2-substituted benzimidazole derivatives from o-phynelyenediamine and substituted aldehydes were developed under zinc triflate in ethanol solvent at reflux temperature.

Effect of TiO2 Crystallite Diameter on Photocatalytic Water Splitting Rate

Abstract: The effect of (Pt-loaded)TiO2 crystallite diameter (i.e. Scherrer size) on the photocatalytic water splitting rate was investigated. (Pt-loaded)TiO2 powders with a wide range of crystallite diameters from about 16 to 45 nm with a blank region between about 23 and 41 nm were prepared by various annealing processes from an identical TiO2 powder. Water splitting experiments with these powders were carried out with methanol as an oxidizing sacrificial agent. It was found that the photocatalytic water splitting rate was sensitively affected by the crystallite diameter of the (Pt-loaded)TiO2 powder. More concretely, similar steep improvements of photocatalytic water splitting rates from around 15 and a little over 2 to about 30 μmol·m-2hr-1 were obtained in the two (Pt-loaded)TiO2 crystallite diameters ranging from 16 to 23 and from 41 to 45 nm, respectively.

A Green Approach towards the Synthesis of Enantio Pure Diols Using Horse Radish Peroxidase Enzyme Immobilized on Magnetic Nanoparticles

Abstract: Enantiopure epoxides and their corresponding chiral vicinal diols serve as valuable intermediates in the synthesis of biologically active pharma and agro-compounds and also value added fine chemicals. Biocatalysts are well known for their selective hydrolysis of racemic epoxides to give optically pure chiral diols. This study highlights an efficient process of synthesis of chiral vicinal diols in good yields and enantioselectiviy using horse radish peroxidase enzyme immobilized on the amine functionalized magnetic nano particles (Fe3O4 nanoparticles) as enzyme carriers. It also facilitates separation of MNP-immobilized enzymes by applying external magnetic field. The immobilization of magnetic nano particles was confirmed by transmission electron microscope (TEM) and scanning electron microscope (SEM). The MNP-immobilized peroxidase enzyme improved stability of the enzyme and has shown broader substrate specificity in enantioselective hydrolysis of racemic epoxides, under mild and environmentally friendly conditions. The methodology MNP-immobilized enzyme developed in the synthesis of chiral diols has a potential for use in large-scale applications.

Modification on Synthesis of Mixed Ligand Chelates by Using Di- and Trivalent Transition Metal Ions with Schiff Base as Primary Ligand

Abstract: New mixed ligand chelates synthesized from di-and trivalent metal ions (Cr, Co, Ni, and Cu ions) and Schiff base (L1) resulted from the condensation of 4-dimethylaminobenzaldehyde with 2-aminophenol as primary ligand, whereas 2-nitroaniline (L2) represents the secondary ligand in a molar ratio of M:L1:L2 [1:1:1] The synthesized Schiff base and chelates have been characterized by using several tools, such as, elemental analysis, molar conductivity, magnetic moment measurements, infrared and electronic spectra The mass spectra of the ligands and Ni(II) chelate were used to justify the process of modification, as well as, the electron paramagnetic resonance spectrum which was carried out for Cu(II) chelate all in order to elucidate the chemical and geometrical structure of the chelates On the basis of the obtained data, the geometry of the products was proposed for all the chelates

Use of Ultrasound and Microwave Irradiation for Clean and Efficient Synthesis of 3,3'-(Arylmethylene)bis (2-hydroxynaphthalene-1,4-dione) Derivatives

Abstract: Nine 3,3’-(arylmethylene)bis(2-hydroxynaphthalene-1,4-dione) derivatives were synthesized through the reaction between 2-hydroxy-1,4-naphthalen-1,4-dione and different aromatic alde-hydes in water applying ultrasonic irradiation for 5 min at room temperature and microwave irradiation for 15 min at 70°;C. Two of the nine derivatives, compounds 3-e and 3-i, obtained from 3-bromo-hydroxybenzaldehyde and 5-methylfuran-2-carbaldehyde, respectively, are previously unpublished. The structures of all compounds were established on the basis of their spectral data and mass analysis. The attractive features of this synthesis protocol include mild conditions, high atom-economy and excellent yields with the elimination of water as the only by-product.

Oxone-Mediated Oxidative Esterification of Heterocyclic Aldehydes Using Indium(III) Triflate

Abstract: Recent investigations have shown the oxone-mediated oxidative methyl esterification of benzaldehyde derivatives using methanol. The reactions were accelerated in the presence of indium(III) triflate, a trivalent indium reagent, in many cases. Based on this method of methyl esterification of benzaldehyde derivatives, we further explored an application to heterocyclic aldehydes. The reactions were examined using methanol as well as other alcohols in order to establish a suitable range.

Thermochemical Assessment of Solid and Liquid Fuels Used for Domestic Space Heating in Jordan

Abstract: The gross calorific values of crude and exhausted olive pomace, oak, almond, olive wood, olive oil, kerosene, and diesel are reported in this article. Conversion of crude olive pomace into exhausted olive pomace resulted in 10% reduction in calorific value. The net calorific value of crude olive pomace amounts to 92% of its gross calorific value. The ultimate and proximate analyses of crude olive pomace representing the 2006-2008 olive harvest seasons were determined and compared with analyses pertaining to the 2009-2011 olive harvest seasons in Jordan. Controlled charring of crude olive pomace reduced its mass down to about 20%. Pyrolysis thermogravimetric (TG) and differential thermogravimetric (DTG) curves were recorded under nitrogen atmosphere for crude olive pomace and wood samples. Quantitative data on three DTG major peaks are reported for wood samples and crude olive pomace. A comparison based on market price and calorific value of a fuel showed that olive pomace is the most rewarding fuel for domestic space heating in Jordan.

Parametric Response Evaluation for Xanthosoma spp. Induced Coag-Flocculation of Brewery Effluent

Abstract: This paper presents the kinetic and functional parametric behavior of cocoyam coagulant (CYC) in respect of pH and time variation in brewery effluent at room temperature. The study employed standard nephelometric jar test while CYC production was based on method reported by Ndabigengesere. Coag-flocculation parameter such as order of reaction α, rate constant K, coagulation period, τ1/2 etc. were determined. Maximum parameter values are recorded at K of 6 × 10-1 L/mg·min; dosage of 200 mg/L, pH 8 and τ1/2 of 0.00146 min while the minimum values are recorded at 3 × 10-7 L/mg, dosage of 100 mg/L, pH 10 and τ1/2 of 20.4 min. The maximum coag-flocculation efficiency E (%) obtained was 92.28, thus establishing CYC as a potential effective coag-flocculaant.

An Efficient and Green Route to Synthesize Azo Compounds through Methyl Nitrite

Abstract: A clean preparation of aryl diazonium ions using methyl nitrite is described. Further reaction of the aryl diazonium ions with substituted benzenamine, substituted phenol and nathphol in deferent kinds of diazotization has been developed. In order to improve the water-solubility of the products, azo coupling reactions of sodium sulfanilate hydrochloride diazonium ions were also performed. The procedures are easy operations, environmentally benign conditions and high yields of the products with potential use as azo-dyes and pigments. Furthermore, no nitrous acid is produced during the diazotization which avoided the formation of dark decomposition products of the corresponding aromatic amine. Proposed mechanism is presented according to our procedure.

Stabilization of Silica Gel against Hydrolysis by Doping with Fˉ or Zr(IV)

Abstract: Silica gel (SG) was synthesized via acidification of sodium silicate solution then doped with Fˉ or Zr(IV) in molar ratios of F/Si 3/100, and Zr/Si 0.75/100 and 3.75/100 and sintered at 500°C, 800°C and 1000°C. The samples were investigated by X-ray diffractometry, infrared absorption and Raman spectra, surface area measurement, and inductively coupled plasma-optical emission spectrometry-monitored silica hydrolysis. All samples are mesoporous with BET surface areas 181.5 - 523.9 m2·gˉ1. The surface area of the silica samples decreases as the sintering temperature increases. The hydrolysis process of silica decreases as the sintering temperature increases and as the surface area decreases. The pH and the type of buffer solution affect the hydrolysis of silica samples due to a SN2 reaction mechanism favored in basic media using ammonia buffer. Zr(IV) increases the stability of silica samples against the hydrolysis as confirmed by the structural investigation, surface area and silica hydrolysis. Fˉ observably decreases the silica hydrolysis process when presenting on the surface of SG.

TiO2 Films Synthesis over Polypropylene by Sol-Gel Assisted with Hydrothermal Treatment for the Photocatalytic Propane Degradation

Abstract: The present investigation shows experimental results obtained with TiO2 thin films synthesized by the sol-gel method assisted with hydrothermal treatment over polypropylene, using the dip coating technique. Obtained coatings were characterized through SEM, XRD, UV-Vis and the photo- catalytic activity was monitored by GC. According to results, the hydrothermal treatment facilitates the crystallization of the TiO2 anatase phase, which is present in all synthesized films. Crystal size formed from precursor solutions (estimated by the Scherrer’s equation) depends on the time and temperature of the hydrothermal treatment, wherein solution exposed to a higher temperature treatment of 150。C for 1.5 h (H150/1.5) exhibited a larger crystal size compared to those synthesized at 80。C for 1.5 h and 3 h (H80/1.5 and H80/3). Sample H150/1.5 over polypropylene resulted in a uniform and crack free coating. This behavior was attributed to the precursor solution being denser than those synthesized at 80。C. Additionally, the photocatalytic activity of the coatings was evaluated through the degradation of propane. Coating H150/1.5 reached 100% conversion after 3 h of UV light irradiation.

New one-pot methods for preparation of cyclohexanecarbonitrile – Green Chemistry metrics evaluation for one-pot and similar multi-step syntheses

Abstract: Three new multi-step one-pot processes for high-yielding cyclohexanecarbonitrile synthesis starting from cyclohexanone were developed for industrial application. In contrast to the current synthetic process, all of the processes described were designed to proceed completely in methanol as a uniform solvent and the key oxidation step can be realized either as stoichiometric or catalytic. Atom efficiency of processes is relatively advanced with high regioselectivity, reaction by-products are either from environmental pool—carbon dioxide and nitrogen—or they can be reused—sodium chloride. Solvent—methanol—and other auxiliaries—cyclohexane, copper catalyst—can be reused after recycling as well. EcoScale for all three designed processes was evaluated and compared with current synthesis described in the past. Green chemistry metrics, including newly introduced evaluative tool—Sustainability Index of the Synthesis (SIS), were applied to evaluate design of described one-pot syntheses.

Heck Reactions with Ultralow Concentration of Transition Metals under Microwave Irradiation

Abstract: The Heck coupling reactions of aryl halides and olefins were performed under the microwave assistance. Interestingly, the ultralow concentration of transition metals (in ppb) coming from the reactants could catalyze the Heck coupling reactions under microwave irradiation, without addition of any catalysts, ligands and phase-transfer agents. The influences of bases, solvents and temperature were discussed, and the reaction rate was enhanced largely in the mixed solvents of NMP and water due to the solubility of base in water.

Enhancement of Photocatalytic Water Splitting Rate via Rayleigh Convection

Abstract: In order to enhance photocatalytic water splitting rates with Pt/TiO2 powder, sufficient agitation of the biphasic medium is required to switch surficial reactions to volumetric reactions. Additionally, agitation is conducive to higher diffusion rates of the generated hydrogen and co-produced oxygen, hindering their ability to re-couple to water on Pt loaded to TiO2 powder. In order to create agitation without consuming any electricity, a novel technique utilizing Rayleigh convection was applied, and its ability to enhance photocatalytic water splitting rates was evaluated. Higher Rayleigh convective flow rates resulted in higher photocatalytic water splitting rates. Utilization of Rayleigh convection approximately doubled the photocatalytic water splitting rates, despite relatively low convective flow velocities (obtained through simple thermo-hydrodynamic simulations). The rate enhancement achieved through Rayleigh convection is a result of its ability to disperse the ultrafine Pt/TiO2 particles throughout the whole medium, leading to volumetric reactions.

Coupling of Wind Energy and Biogas with a High Temperature Steam Electrolyser for Hydrogen and Methane Production

Abstract: The production of environment friendly green fuels is based on energy from renewable sources. Among the renewable sources, wind power is a very growing power technology. An example which has been discussed very widely is hydrogen which is an ideal fuel for a fuel cell. Hydrogen is the energy of the future. It will be used as energy carrier as well as reactant to produce green fuels, like methane which is easier to handle. Direct coupling of a High Temperature Steam Electrolyser (HTSE) with a wind turbine can be used to generate hydrogen. Indeed performing the electrolysis process at high temperatures offers the advantage of achieving higher efficiencies compared to the conventional water electrolysis. The hydrogen produced can be then reacted with the CO2 content of biogas to form methane as green fuel. Thus, the concept presented in this paper illustrates the potential of the HTSE technology coupled with a wind turbine, this system being combined with biogas in a methanation unit. Developing scenarios and flow sheets and using mass and energy balance, the technical performance of the concept is investigated. A plant capacity of 10 MWel is considered. An annual production of 1104 metric tons per year (Mt/a) hydrogen and thus of 5888 Mt/a methane is reached. The overall plant efficiency is calculated to be 38%. The combination of wind power and biogas offers thus many advantages which can facilitate the penetration of the wind resource and the progression to the hydrogen economy.

Process Temperature Profile and Rheological Properties of Greases from Vegetable Oils

Abstract: Greases are composed by lubricating oil dispersed in a thickener that can be a metal soap, polymers or clays. Grease production using vegetable oils is increasing due to biodegradability requirements. Since vegetable oils present a worse oxidation and hydrolysis stability than mineral oils, it is usually difficult to produce a neutral grease using them. Four greases were produced using soybean oil as lubricating oil and lithium 12-hydroxy- stearate as thickener. The maximum temperature of reaction ranged from 230°C to 120°C in a bench process and a reduction in the final product acidity was observed (from 8.2% acid to 0.05% alkaline). Traditional tests to evaluate thickener structure resistance like 10,000-time worked penetration, roll stability and dropping point were performed and results compared. In addition, rheological tests were performed and the results were also compared. Results indicate that it is possible to produce a quite neutral grease using vegetable oils with good thickener structure properties.

A Greener Approach for Synthesis of Functionalized Polyolefins by Introducing Reactive Functionality into Ethylene Copolymers

Abstract: Recent successful examples for synthesis of new polyolefins containing (polar) functionalities by adopting the approaches by controlled incorporation of reactive functionalities (and the subsequent introduction of polar functionalities under mild conditions) by coordination polymerization in the presence of transition metal complex catalysts have been described. Related methods (such as direct copolymerization of olefin with polar monomer using living radical or coordination insertion methods) have also been demonstrated for comparison. Our recent efforts for precise synthesis of polyolefins containing polar functionalities by efficient incorporation of reactive functionality by copolymerization of ethylene with nonconjugateddiene (1,7-octadiene, vinylcyclohexene etc.) or divinyl-biphenyl using nonbridged half-titanocene [ex. Cp’TiCl2(O-2,6-iPr2C6H3), Cp’ = C5Me5, tBuC5H4 etc.] catalysts have been introduced.

Nano-γ-Fe 2 O 3 : Efficient, Reusable and Green Catalyst for N - tert -Butoxycarbonylation of Amines in Water

Abstract: An efficient and versatile practical protocol for the chemoselective N-tert-butoxycarbonylation of amines using Nano-γ-Fe2O3 and (BOC)2O. Nano-γ-Fe2O3 was applied as an efficient, green, heterogeneous and reusable catalyst at ambient temperature; the method is general for the preparation of N-Boc derivatives of aliphatic, heterocyclic, aromatic as well as amino acid derivatives.

Microstructure-Property Relationship in Self-Crosslinked Non-Derivative Acetic Acid Lignin-Containing Polyurethane Membranes

Abstract: With the assistance of different solvents, self-crosslinked acetic acid lignin-containing polyurethane (LPU) membranes were synthesized. Compared with tetrahydrofuran and dioxane, N, N-dimethylacetamide with stronger polarity together with higher boiling point was demonstrated to be beneficial for preparing LPU particles of smaller size and enhanced binding force. It was also found that lignin domain can interpenetrate into polyurethane domain well with 43.3% lignin addition, resulting in enhanced phase mixing and better performance. In addition, relative homogeneous and smooth LPU membrane can be obtained with 2% TMP addition, while stress crack took place when TMP content was greater than 3%.

Photoelectrocatalytic Oxidation of Ethinylestradiol on a Ti/TiO2 Electrode: Degradation Efficiency and Search for By-Products

Abstract: The degradation of ethinylestradiol (EE, an orally bio-active estrogen) in an aqueous-methanolic solution using a Ti/TiO2 thin-film electrode and UV radiation (a photoelectrocatalytic system) was evaluated. Hence, HPLC/UV analysis shows that EE (at 0.34 mmol) is totally consumed after 30 minutes of exposure to the photoelectrocatalytic system in the presence of Na2SO4 (0.1 mol·L-1) and with an applied bias potential of +1.0 V versus the Ag/AgCl reference electrode. Moreover, monitoring by direct infusion electrospray ionization mass spectrometry (ESI-MS) and SPME-GC/ MS (solid phase microextraction coupled with gas chromatography-mass spectrometry) reveals that apparently no degradation products are formed under these conditions. Hence, this study demonstrates that the photoelectrocatalytic system can be efficiently used to promote the complete degradation (and likely mineralization) of this hormone under these conditions.

Book Review of Green Materials for Sustainable Water Remediation and Treatment

Abstract: Water is one of the most important substances on earth. Safe drinking water is essential to humans and other life forms. All plants and animals must have water to survive. If there was no water, there would be no life on earth. Apart from drinking it to survive, people have many other uses for water. This natural resource is becoming scarcer and its demand exceeds supply in some region rendering its availability a major social and economic concern. Apart of this scarcity is water pollution which is increasing day by day in many parts of the world. Sources of fresh water on land are getting more and more polluted than ever before. As a result, contaminated water became unsuitable for use. Poor water quality is deadly since contaminated water causes hazards to public health through poisoning or the spread of disease. In order to address these issues, the practice of water remediation has been developed.

Study on Hydrogen Production System by Coupling with DSSCs

Abstract: The consumption of dye-sensitized solar cells (DSSCs) used to produce hydrogen, compared with the traditional water-splitting energy, is much less. First of all it is because of DSSCs’ low cost, easy fabrication process, high conversion efficiency and good stability; secondly it also solves the problem of serious corrosion of the electrode, for the entire solar system is in the air. We use three tandem dye-sensitized photovoltaic cells as a source of power; the open circuit voltage of photoelectric unit shows the feasibility of using dye-sensitized photovoltaic cell decomposition of water to produce hydrogen.

Comparative Study of Hydrogen Electrooxidation on Gold and Platinum in Solutions Containing Perchlorate Ion

Abstract: The electrooxidation of hydrogen on platinum and gold electrodes is comparatively described in this paper. The reaction is faster on platinum than on the gold surface, because the reactive diffuses inside of the gold metal. This process is complicated with the lift of surface reconstruction of the (100) plane, which allows the fast penetration of the H atoms through the more open surface. The diffusion limiting current is then discontinued and the current falls. On platinum, the current fall occurs simultaneously with the metal oxide formation. It is assumed that the hydrogen helps the adsorbed OH group formation, which is the first step of metal oxidation, and it has been called “incipient hydrous oxide” (IHO). Current begins to fall slowly at the (IHO) potential. At higher potential the current falls abruptly.