Solvent-free Medium Research Articles

Clay-catalyzed ozonation of endocrine-disrupting compounds in solvent-free media – to better understand soil catalytic capacity

An original approach never tackled so far allowed correlating the basicity and hydrophilic character of clay catalysts to surface interaction with 17α-Ethinylestradiol (EE2) during ozonation in water. The clay catalysts were found to behave specifically according to their silica/alumina ratio like soils in natural oxidative processes. Acid-activated bentonites (HMt) and ion-exchanged montmorillonite (NaMt and Fe(ii)Mt) showed catalytic activity in the ozonation of 17α-ethinylestradiol (EE2) in aqueous media. In the absence of catalysts, the degradation of (EE2) reached 72% after one minute of ozonation and 99.5% after 60 minutes. In the presence of Fe(ii)Mt, EE2 degradation (96%) was achieved after only one minute of ozonation. Under similar conditions, almost total degradation to 99.99% was registered in 15 minutes of ozonation but without total mineralization of the intermediates. Moderately acid-activated bentonites exhibited higher activity affording total mineralization within a short period of ozonation. The catalytic activity of clay catalysts was found to correlate with their surface basicity and hydrophilic character. The results obtained herein allow understanding soil behavior in natural oxidative degradation of organic molecules and envisaging effective soil-based catalysts with surface properties judiciously tailored according to the nature of organic pollutants in solvent free media.

Semi-continuous Production of 2-Ethyl Hexyl Ester in a Packed Bed Reactor: Optimization and Economic Evaluation.

The aim of this work was to investigate the technical as well as the economic feasibility of producing 2-ethyl hexyl oleate (2-EHO), a non-phthalate plasticizer in a solvent free medium. The esterification reaction between oleic acid and 2-ethyl hexyl alcohol was carried out in a packed bed reactor (PBR) using Candida antarctica lipase B (Novozym 435; Novozymes; Copenhagen-Denmark) as biocatalyst. RSM was employed to optimize the esterification reaction conditions. The optimum reaction conditions were found to be flow rate of 1.5 mL/min, No. of cycles of 12 and molar ratio of 4:1 2-ethyl hexanol to oleic acid. The maximum experimental and predicated conversions were found to be 95.8% and 95.61% respectively. Formation of 2-EHO was approved by FTIR, 1HNMR and 13CNMR. From the economic prospective, PBR was capable of producing 2-EHO with a purity of more than 94% over 480 h without remarkable reduction of enzyme activity. This revealed an economic production of 2-EHO at a yield of 2 tons kg-1 lipase. The manufacturing cost was found to be $ 1.88 /kg 2-EHO, this contributed to a profit of about 30% compared to the commercial price of 2-EHO. Such results approve the technical and economic feasibility for this sustainable method in esters production.

Catalytic C-H aerobic and oxidant-induced oxidation of alkylbenzenes (including toluene derivatives) over VO2+ immobilized on core-shell Fe3O4@SiO2 at room temperature in water.

Direct C–H bond oxidation of organic materials, and producing the necessary oxygenated compounds under mild conditions, has attracted increasing interest. The selective oxidation of various alkylbenzenes was carried out by means of a new catalyst containing VO2+ species supported on silica-coated Fe3O4 nanoparticles using t-butyl hydroperoxide as an oxidant at room temperature in H2O or solvent-free media. The chemical and structural characterization of the catalyst using several methods such as FTIR spectroscopy, XRD, FETEM, FESEM, SAED, EDX and XPS showed that VO2+ is covalently bonded to the silica surface. High selectivity and excellent conversion of various toluene derivatives, with less reactive aliphatic (sp3) C–H bonds, to related benzoic acids were quite noticeable. The aerobic oxygenation reaction of these alkylbenzenes was studied under the same conditions. All the results accompanied by sustainability of the inexpensive and simple magnetically separable heterogeneous catalyst proved the important criteria for commercial applications.

Coupling Rhodium-Catalyzed Hydroformylation of 10-Undecenitrile with Organic Solvent Nanofiltration: Toluene Solution versus Solvent-Free Processes.

Intensification of the rhodium-catalyzed hydroformylation process to produce 12-oxo-dodecanenitrile from biosourced 10-undecenitrile was performed by coupling the reaction with organic solvent nanofiltration (OSN) for the recycling of the expensive Rh catalyst and the ligands. Four phosphorus-based ligands were compared with respect to their catalytic performance and rejection in OSN. Biphephos showed the best compromise and up to 3 reaction-OSN cycles were performed in toluene. A good recycling of the catalytic system was evidenced arising from the OSN (up to 88 % rejection). In order to develop a greener process, a similar approach was achieved in bulk (i. e. solvent-free medium), thus proving the catalyst recycling feasibility but also that the optimal OSN conditions are not the same as for toluene. Finally, integration of OSN in the overall production process is discussed, aiming at the proposal of a hybrid separation process involving a combination of OSN and distillation for an energy-efficient separation step.

Enzymatic synthesis of neopentyl glycol-bases biolubricants using biodiesel from soybean and castor bean as raw materials

Synthetic oleochemical esters represents a growing alternative for mineral oil-based lubricants. In this sense, the present study shows the results of enzymatic synthesis of neopentyl glycol-bases biolubricants using biodiesel from soybean and castor bean as raw materials. The potential of two commercial immobilized lipases, lipase B from Candida antarctica (Novozyme 435) and lipase from Rhizomucor miehei (Lipozyme RM IM), to produce NPG esters in a solvent-free medium was evaluated. High conversions (>95%) were obtained for both raw materials, with both enzymes, but in a shorter reaction time for soybean biodiesel (24 h) than castor biodiesel (48 h). Both enzymes could be successfully reused for six reactions, Novozyme 435 maintained ≥70% of the initial conversion using the two raw materials and Lipozyme RM IM maintained ≥90% of the first reaction conversion using castor biodiesel. The soybean NPG esters showed good viscosity index, higher than 198, and the castor NPG esters showed good pour point, lower than −20 °C, and good oxidative stability, higher than 30 min. The physico-chemical properties of the biolubricants were dependent on the biodiesel source which directly influence the final application of the products.

Hyaluronic acid/corn silk extract based injectable nanocomposite: A biomimetic antibacterial scaffold for bone tissue regeneration.

Injectable hydrogels have revealed the great potential for use as scaffolds in cartilage and bone tissue engineering. Here, thermosensitive and injectable hydrogels containing β-tricalcium phosphate, hyaluronic acid, and corn silk extract-nanosilver (CSE-Ag NPs) were synthesized for their potential use in bone tissue regeneration applications. Spherical nanoparticles of silver were biosynthesized through microwave-assisted green approach using CSE in organic solvent-free medium. Rheological experiments demonstrated that the thermosensitive hydrogels have gelification temperature (Tgel) close to body temperature. The samples containing Ag NPs showed antibacterial activity toward gram-positive (Bacillus Subtilis, Staphylococcus Aureus) and gram-negative (Pseudomonas Aeruginosa, Escherichia Coli) bacteria along without cytotoxicity after 24 h. Mesenchymal stem cells seeded in the nanocomposite exhibited high bone differentiation which indicate that thay could be a good candidate as a potential scaffold for bone tissue regeneration.

Synthesis of Quinazolines Catalyzed by Immobilized Spirulina on Cellulose/Dendritic Fibrous Nanosilica (DFNS)

In this study, eco-friendly Spirulina (DFNS/Cellulose/Spirulina NPs) having heterogeneous recoverability, reusability, high efficiency, renewability, and high thermal stability were fabricated on natural cellulose and their chemical structures were illuminated by FT-IR, BET, SEM, TEM, and TGA analysis. Extracted microcrystalline cellulose from Carthamus tinctorius plant. It was found that average size of the DFNS/Cellulose/Spirulina NPs changed in the range of 300–400 nm and Cellulose/Spirulina homogeneously dispersed on the DFNS. Then, catalytic performance of DFNS/Cellulose/Spirulina NPs was investigated for synthesis of various quinazolines under solvent-free media at room temperature. The catalytic tests showed that DFNS/Cellulose/Spirulina NPs are excellent catalyst for synthesis of quinazolines by giving high reaction yields in 20 min. More importantly, DFNS/Cellulose/Spirulina NPs displayed excellent reproducibility in the synthesis of quinazolines due to their heterogeneous separable nature. As a consequence, this study revealed that DFNS/Cellulose/Spirulina NPs accelerating the fabrication of quinazolines had excellent activity.

Enzymatic synthesis of cetyl oleate in a solvent-free medium using microwave irradiation and physicochemical evaluation

A cosmetic ester, cetyl oleate was synthesized using microwave irradiated system. The esterification reaction was carried using Candida antarctica lipase B in a solvent-free media. The influence of various reaction parameters was studied, and the efficiency of Fermase CALBTM10000 was compared with other enzymes. Equilibrium conversion of 97.5% was obtained within 20 min at 60 °C temperature, 1:2 oleic acid to cetyl alcohol molar ratio and 4% w/w dose of lipase. A comparative study showed that microwave irradiation is a much more efficient method than ultrasound irradiation and conventional heating. Fermase CALBTM10000 was reusable over 6 enzymatic cycles as its stability improved under microwave system. Physicochemical parameters of cetyl oleate were tested in order to analyze its suitability for further cosmetic use.

Preparation and characterization of novel hybrid bio-support material immobilized from Pseudomonas cepacia lipase and its application to enhance biodiesel production

In the present study, hybrid bio-support catalyst (BSC) has been prepared for the production of biodiesel from Castor oil. Lipase from Pseudomonas cepacia has been immobilized on a hybrid bio-support material (BSM) by entrapment method and characterized. The highest immobilized lipase activity and loading efficiency were 87.28 (U/g) and 55.2%, respectively. The composition of Castor oil expelled from Castor seeds evaluated through Gas Chromatograph-Mass Spectrometer (GC-MS) technique. GCMS spectra show the percentage composition of ricinoleic, linoleic, oleic, stearic, palmitic, and nonanoic acid, as 78.67, 9.62, 6.65, 1.53, 2.19, and 0.08, respectively. Optimized conditions for the transesterification of Castor oil with propan-2-ol as acyl acceptor in solvent free medium were, 10% immobilized lipase relying on oil-weight, molar ratio of alcohol to oil (6:1) at 50±1°C for the period of 24 h. The product yield was estimated as 75% while the calculated conversion of biodiesel was approximately 78%. The reusability of hybrid BSC for 12 runs was found to be 70% of its initial biodiesel yield after 6 cycles. The properties of oil and biodiesel were calculated using American Standards for Testing Material (ASTM) D6751; formation of biodiesel confirmed by Proton Nuclear Magnetic Resonance (1H NMR) and Fourier Transform Infrared (FTIR) analysis.

Reaction strategies for the enzymatic synthesis of neopentyl glycol diheptanoate

This work describes for the first time the green synthesis of neopentyl glycol diheptanoate in a solvent-free medium via an enzymatic pathway. The process has been carried out in an open-air reactor in order to ease water removal through evaporation and shift the chemical equilibrium towards product formation. The inhibiting effect of high concentrations of heptanoic acid has been put into evidence by a reduction of initial reaction rate when esterification was performed with stoichiometric amounts of substrates. Therefore, in this work different strategies for the stepwise addition of heptanoic acid are proposed, and best results were obtained when stoichiometric quantities of acid were divided in four equal amounts and added when previous batch was consumed. Biocatalyst Novozym® 435 concentration and temperature were optimised, giving yields of 90% in neopentyl glycol diheptanoate when 7.5% (w/w) and 70 °C were used. With a remaining 7% of heptanoic acid (probably caused by the alcohol evaporation) the addition of neopentyl glycol led to a conversion of 95%. Thus, product can be used in cosmetics without further purification and can be labelled as environmentally-friendly synthesized because of its enzymatic origin.

A convenient approach directly from triglycerides toward the producing of thia-wax esters as bio- and chemical raw materials

Practical and efficient method has been developed for the preparation of novel sulfur-containing esters from triglycerides as potential important industrial and biomaterials. The fact that these unusual compounds are not found in natural sources encourages both academic and industrial communities for their preparation with suitable chemical or enzymatic processes. In general, enzymatic processes requiring more laborious synthesis and product isolation stages. On the other hand, known chemical methods for the preparation of normal wax esters have several drawbacks cited in the present work. Therefore, the chemical method developed in the present study is environmentally benign and suitable for both small- and large-scale syntheses of normal and unusual wax esters. For this purpose, triglycerides were taken to the transesterification reaction in a solvent-free medium with synthetic thia-long-chain alcohols at a ratio of (1:3). In order to catalyze the reaction, newly synthesized bis-imidazole-based metal-free acidic ionic liquid was used and the thia-mono esters were obtained in a fairly short period of time (6 h) with good to excellent yields. The catalyst reuse and large-scale synthesis studies were also carried out.

Design of highly robust halloysite nanoclay supported palladium complex as a highly active heterogeneous catalyst for construction of biaryls

Metal leaching, contamination of final product, lack of recovery, and limited reusability are important problems in catalyst systems. The best way to overcome these drawbacks is to design highly stable heterogeneous catalysts. Therefore, we prepared in this study a heterogeneous palladium catalyst (Hal-Pd) from halloysite nanoclay which is a natural, non-toxic, cheap, biocompatible and environmentally friendly clay with high surface area. Then, Hal-Pd was evaluated as a heterogeneous catalyst for Suzuki-Miyaura coupling reactions under solvent-free media. Hal-Pd catalyst showed high tolerance against different substituted aryl halides. Furthermore, Hal-Pd catalyst was easily recovered for the next runs, and it was reused at least ten times with a slight loss in product yield from 99% to 82%. It also showed very minimal level of Pd leaching. Besides its high catalytic activity, Hal-Pd catalyst presented some advantages such as operation simplicity, short reaction time, and high stability. This study shows that halloysite nanoclay can be an alternative catalyst support compared to other known support materials, and the newly designed Hal-Pd is an efficient catalyst that facilitates the synthesis of various biaryl compounds.

Biosynthesis and characterization of antibacterial thermosensitive hydrogels based on corn silk extract, hyaluronic acid and nanosilver for potential wound healing

The wounds closure after physical injury or surgery is of significant clinical and research importance. In this study, thermosensitive and injectable hydrogels based on hyaluronic acid (HA), corn silk extract (CSE) and nanosilver were prepared and their potential use as a wound care material was investigated. Silver nanoparticles (Ag NPs) were biosynthesized by a microwave-assisted green technique using corn silk extract in an organic solvent-free medium. Rheological analysis demonstrated that the nanocomposites have good mechanical properties with gelation temperature close to the body temperature; hence, they can be easily administrated locally on wounded skins. The samples exhibited antibacterial activity toward gram-positive and gram-negative bacteria. Cytotoxicity assay showed that the hydrogels have good biocompatibility. Interestingly, an in-vitro model of wound healing revealed that the nanocomposites allow faster wound closure and repair, compared to the control. The obtained results highlight the potential application of these novel injectable hydrogels as wound dressing.

Sustainable process for the production of symmetrical dibasic acid ester-basedthermal energy storage materials from lipids

Oleochemical-based long-chain diesters are potential organic phase change materials convenient for thermal energy storage. The development of efficient and green methods is an important requirement for the preparation of these environmentally friendly compounds, which also are finding wide industrial application. Thus, in the present work, a series of dibasic acid esters were synthesized through ionic liquid catalyzed scalable chemical esterification or transesterification reactions in a solvent-free medium. The starting compounds, dicarboxylic acids or their methyl esters and fatty alcohols or cholesterol, were reacted in the ratio of 1:2 respectively and the synthesized esters were characterized by FT-IR, $^{1}$H NMR, and $^{13}$C NMR.

Highly active and recyclable heterogeneous palladium catalyst derived from guar gum for fabrication of biaryl compounds.

In this study, a novel highly efficient heterogeneous palladium catalyst (GG-Pd) was prepared using guar gum, which is an environmentally friendly, easily available, fairly cheap, and renewable natural bio-polymer. Detailed characterization of GG-Pd catalyst was successfully performed by FT-IR, TG/DTG, SEM, EDS, XRD, and ninhydrin test, and it was evaluated as a heterogeneous catalyst against Suzuki-Miyaura coupling reactions of a series of aryl halides with phenylboronic acid. Catalytic performance studies showed that GG-Pd efficiently catalyzed Suzuki cross coupling reactions under solvent-free media and for a very short reaction time (5 min). Moreover, reusability tests showed that GG-Pd catalyst could be reused at least ten times with a minor decrease of its catalytic performance. Additionally, it was found that palladium leaching from the designed support was very minimal. This study shows that GG-Pd catalyst is a very useful and highly stable heterogeneous catalyst for Suzuki-Miyaura coupling reactions in terms of high catalytic performance and recyclability.

Solid–Liquid Equilibria and Characterization of the Reaction Mixture To Produce Sucrose Palmitate in Solvent-Free Media

This work deals with the characterization of the reactive mixtures involved in the production of sucrose palmitate from methyl palmitate and sucrose, through a solvent-free process. The solid–liquid equilibrium in mixtures of sucrose–methyl palmitate–sucrose palmitate (SE) at temperatures between 363 and 403 K and sucrose ester concentrations between 0 and 15 g SE/100 g methyl palmitate was measured. Solid and liquid heat capacities of sucrose palmitate and thermal properties useful in the equilibrium modeling were measured through differential scanning calorimetry and thermogravimetric analysis. The viscosity and surface tension of the reaction product were also measured. According to results sucrose palmitate melts at 315.82 K and decomposes at 510.67 K. The average solid and liquid heat capacities of sucrose ester in the evaluated ranges were 2010 J/kg·K and 2475 J/kg·K, respectively. The predictive modified UNIFAC method for sugars (mS-UNIFAC) and the nonrandom two-liquid equation were used to model t...

Biosynthesis of Highly Retrievable Magnetic Palladium Nanoparticles Stabilized on Bio-composite for Production of Various Biaryl Compounds and Catalytic Reduction of 4-Nitrophenol

In this study, eco-friendly palladium nanoparticles (Pd NPs@Pct–CMC/Fe3O4) with magnetic recoverability, high efficiency, renewability, reusability, and high thermal stability were fabricated on pectin/carboxymethyl cellulose composite and their chemical structures were illuminated by FT-IR, XRD, SEM, EDS mapping, ICP–OES, and TG/DTG analyses. It was found that average size of the palladium nanoparticles changed in the range of 49–85 nm, and they homogeneously dispersed on the composite. Then, catalytic performance of Pd NPs@Pct–CMC/Fe3O4 was investigated against (i) synthesis of various biaryl compounds under solvent-free media and (ii) catalytic reduction of highly toxic 4-nitrophenol using NaBH4 in aqueous medium at room temperature. The catalytic tests showed that Pd NPs@Pct–CMC/Fe3O4 is excellent catalyst for synthesis of biaryl compounds by giving high reaction yields in 7 min. Pd NPs@Pct–CMC/Fe3O4 also indicated superior catalytic performance for catalytic reduction of 4-nitrophenol in only 100 s. More importantly, Pd NPs@Pct–CMC/Fe3O4 displayed excellent reproducibility in the synthesis of various biaryl compounds and catalytic reduction of 4-nitrophenol due to their magnetically separable nature. As a consequence, this study revealed that Pd NPs@Pct–CMC/Fe3O4 accelerated the fabrication of biaryls and the catalytic reduction of 4-nitrophenol.

Green oxidation of cyclohexane catalyzed by recyclable magnetic transition-metal silica coated nanoparticles

First-row-transition-metal silica coated magnetite nanoparticles (MNPs), Fe3O4@SiO2-M2+ [M = Mn2+ (1), Co2+ (2), Cu2+ (3) or Zn2+ (4)], were evaluated as catalysts for the selective oxidation of cyclohexane to cyclohexanone and cyclohexanol. The catalytic reaction occurred under mild conditions, using microwave-assisted heating in added solvent-free medium producing water as the only by-product. The manganese (1) and copper (3) surface enriched silica-coated MNPs leaded to the highest yield of oxygenated products (24% and 21%, respectively) after 2 h at 80 °C using hydrogen peroxide as oxidant. These surface modified MNPs can be readily isolated by using an external magnet and no significant loss of activity is observed when reused up to 5 consecutive runs.

Metal Free Acid‐Mediated Solid‐State Polymerization and Processability of Polymers Based on 3,4‐Alkylenedioxythiophenes

ABSTRACTThe present article reports metal free acid‐mediated polymerization of 3,4‐alkylenedioxythiophenes in a solvent free medium and processability of insoluble polymers. It also describes structural variants and functional aqueous dispersions based on 3,4‐alkylenedioxythiophenes. Polymers were processed by dispersing the insoluble polymer powders in aqueous media using polymeric aromatic surfactant (polystyrenesulfonate, PSS) and aliphatic surfactant (sodiumdodecylsulfonate, SDS), respectively. The effect of surfactant on particle size, stability, and conductivity of the dispersions was investigated in detail. Polymer particles in SDS‐based dispersions tend to agglomerate which resulted enhanced conductivity of the thin films. Electrochemical studies revealed that the polymers are electroactive in nature and are transparent in oxidized state. The electrochromic contrast between the oxidized and reduced states of the polymers was in the range of 40–46%. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 783–791

2-Substituted Benzimidazole Synthesis in Dry Medium Mediated by Pyridine N-oxide

Substituted benzimidazoles were obtained from o-phenylenediamine and organic halides in solvent-free medium. The procedure involves pyridine N-oxide as mild oxidizing agent. The benzimidazoles were prepared without the separation of the intermediates. The absence of catalysts and good yields are important benefits of the method.