Vilas G. Gaikar

AQUEOUS HYDROTROPE SOLUTION AS A SAFER MEDIUM FOR MICROWAVE ENHANCED HANTZSCH DIHYDROPYRIDINE ESTER SYNTHESIS

Abstract Hautzsch esters are prepared for the first time, by condensing alkyl β-aminoerotonate, aldehyde and alkyl acetoacetate in aqueous sodium butylmonoglycolsulphate (NaBMGS) as a safe reaction medium in an unmodified domestic microwave oven.

Adsorption of acetic acid on ion-exchange resins in non-aqueous conditions

Abstract Sorption of acetic acid from ethyl acetate and ethanol (95%) has been investigated using polymeric ion-exchange resins with a view for being possibly applied to the removal of acetic acid impurities from organic solvents. The resins have tertiary or quaternary amino functional groups on a styrene–divinyl benzene copolymer matrix. The equilibrium adsorption studies show very selective adsorption with a high loading capacity for acetic acid. The uptake of the acid from the organic solutions is by sorption reinforced by specific interaction with the functional groups on the polymer matrix. The specific interaction takes place by a hydrogen bonded complex formation between the acidic proton and the lone pair of electrons on the amino group. An efficient application of ion-exchange resins is indicated in purification of ethyl acetate by selective sorption of acetic acid.

Adsorptive recovery of naphthenic acids using ion-exchange resins

Adsorption of naphthenic acids has been studied on commercial weak and strong anion-exchange resins. The capacity and equilibrium constant of adsorption on these resins are compared with those obtained with zeolites, bentonite and polyvinyl pyridine. Macroporous weakly anionic ion-exchange resins with weak tertiary amine group have good adsorption capacity for the removal of naphthenic acids from petroleum oil as compared to strong anion-exchange resins with isoporous structure although the strong anion-exchange resin shows greater interaction with naphthenic acids. The rate of uptake of naphthenic acid is governed by the internal diffusional resistance which is also dependent on adsorbed phase concentration.

Membrane characteristics as determinant in fouling of UF membranes

Ultrafiltration of bovine serum albumin solutions using cellulose triacetate (CTA) and regenerated cellulose (RC) membranes showed that CTA membranes were more vulnerable to fouling than hydrophilic RC membranes. The flux decline for both membranes, which was more significant initially, could be attributed to concentration polarization near membrane surfaces and adsorption of the protein. Fouling of the membranes was characterized by the resistance of protein deposits to the permeation of pure water through fouled membranes. The CTA membranes gave more resistant protein deposits than the RC membranes and the resistance increased, two to three times, in the presence of salts but decreased substantially at higher temperatures.

Hydrotropic Extraction of Curcuminoids from Turmeric

A novel hydrotropy-based extraction method for selective extraction of curcuminoids from Curcuma longa (turmeric) was investigated. The degree of extraction was dependent upon the effect of a hydrotrope on the cellular structure and hydrotrope–curcuminoids interactions. Hydrotropes directly affect the cell structure, making curcuminoids more accessible either by dissolution of the cell membrane/wall constituents or by disorganizing cell wall. Sodium cumene sulfonate (Na-CuS) was found to be an efficient hydrotrope for the extraction of curcuminoids. A significantly strong interaction with sodium n-butyl benzene sulfonate (Na-NBBS) of curcuminoids was undesirable in the recovery of curcuminoids from the extract phase, although Na-NBBS was extremely efficient in extracting curcuminoids. The two-step process, hydrotropic solubilization followed by dilution using water with or without pH adjustment, gave good yields of curcuminoids with high purity.

Microwave assisted extraction of curcuminoids from Curcuma longa

A novel microwave assisted extraction (MAE) technique was investigated for selective and rapid extraction of curcuminoids from Curcuma longa (turmeric) into organic solvents. The degree of extraction and purity of curcuminoids were dependent upon the selected solvent and exposure time to microwaves. The extraction process was optimized using acetone at 20% power level (PL) giving 60% extraction of curcuminoids with 75% purity within 1 min. The dielectric heating of cellular matrix resulted in vaporization of volatile components, increasing internal pressure of the cell leading to remarkable swelling and finally rupturing of the cells. The degradation of cellulosic cell wall at higher temperature when subjected to microwave also increased permeability of solvents into the bio-matrix.

NOTE: EXTRACTIVE SEPARATIONS WITH HYDROTROPES

ABSTRACT Hydrotropic substances, such as, sodium P-toluene sulfonate, potassium P -toluene sulfonate, sodium P -xylene sulfonate, potassium P-xylene sulfonate, sodium benzoate, potassium benzoate, etc., in aqueous solutions, at relatively high concentrations, have been used successfully to separate mixtures of close boiling point substances like 2,6-xylenol/P-cresol, pheno1/o-chlorophenol, P -chlorophenol/2,4-dichlorophenol, and o-cresol76-chloro-o-cresol, dissolved in a suitable solvent. Very high values of separation factor in the range of 10 to 66 have been realised and this novel method appears to be promising for industrial utilization.

Extractive separations using hydrotropes

Abstract Hydrotropes, such as sodium toluate, sodium toluene sulfonate, sodium cymene sulfonate, sodium mesitylene sulfonate, and sodium pseudocumene sulfonate, have been investigated for their effectiveness in separations of close boiling point mixtures, such as p -cresol/2,6-xylenol and phenol/ o -chlorophenol. The effect of various parameters, such as the structure of the hydrotrope, concentration of the hydrotrope, nature of the solvent, and composition of the mixtures, on separation efficiency has been studied. The separation factor increases with the concentration and the hydrophobic parameters, such as the surface area and the molar volume of the hydrophobic parts of the hydrotropes. A polar solvent gives poor percentage extractions and in some cases lower separation factors than those obtained with inert solvents.

New Strategies in Extractive Distillation: Use of Aqueous Solutions off Hydrotropes and Organic Bases as Solvent for Organic Acids

Abstract Aqueous solutions of hydrotrope (p-toluene sulfonic acid) and organic bases (methyl diethanolamine, diethanolamine, etc.) have been successfully used as solvents in the extractive distillation of close boiling phenolic substances. This new class of solvents provides sufficiently high values of relative volatility (α ≈ 3) for such close boiling mixtures as 2,6-xylenol/p-cresol, o-chlorophenol/phenol, and 2,4-dichlorophenol/p-chlorophenol. Batch distillation experiments proved the efficacy of these solvents.

Selective Solubilization of Isomers in Hydrotrope Solutions: o-/p-Chlorobenzoic Acids and o-/p-Nitroanilines

Selective solubilization of o-/p-chlorobenzoic acids and o-/p-nitroanilines has been attempted using aqueous solutions of sodium butyl monoglycol sulfate as the hydrotrope. An association model is proposed to fit the solubility data of these isomers and to characterize the hydrotrope–hydrotrope and hydrotrope–solute interactions. The solubility of an o-isomer in the aqueous hydrotrope solutions is higher than the solubility of the corresponding p-isomer, and thus the o-isomer can be selectively solubilized. The solubility of nitroanilines remains unaffected in the presence of the other isomer while chlorobenzoic acids modify the solubility of each other. Thus the separation is affected by the composition of the mixture as well as by the concentration of the hydrotrope. The solubilized material can be recovered by dilution with water.