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ABSTRACT Selective reduction of one of the nitro group present in dinitro aromatic compounds by a novel Zinin reagent, H2S-laden N-methyldiethanolamine (MDEA) solution, has been explored in the presence of tetra- n-butyl phosphonium bromide as a phase transfer catalyst under the liquid-liquid mode of reaction. Under the room temperature reaction condition, reduction of 2,4-dinitrotoluene (2,4-DNT) with H2S-laden MDEA leads to the selective reduction of one nitro group present either at the fourth position to obtain 4-amino-2-nitrotoluene (4A2NT) or at the second position to get 2-amino-4-nitrotoluene (2A4NT). The reaction was very fast to achieve 100% conversion, and the selectivity of 4A2NT is much higher than the 2A4NT. A detailed parametric study was performed to analyze the effect of parameters on 2,4-DNT conversion and selectivity of both the isomers. The apparent activation energy was found to be as high as 46.25 kJ/mol, and the reaction was found to be kinetically controlled. An empirical kinetic model has been developed to correlate with the conversion version time data obtained experimentally. The present system dealt with an industrial problem in dealing with H2S, present in by-product gaseous streams of many petroleum and natural gas industries. Novelties in the selective monoreduction lie in that fact that the reaction was done at room temperature (303 K), with a novel reagent, H2S-laden MDEA solution. Therefore waste-minimization was effected to yield value-added fine chemicals, that is, amines. [ABSTRACT FROM AUTHOR]

Abstract: A new mechanistic model for reactions involving two liquid phases and a homogeneous phase transfer catalyst (PTC) has been developed based on extraction mechanism considering the equilibrium of catalyst and active catalysts at the interface. The proposed kinetic model considers thermodynamic framework based aqueous phase ionic equilibrium and the separate contributions of non-PTC and PTC-enhanced reactions towards the overall reactions. The developed model was then applied to an industrially important reaction of benzyl chloride with aqueous ammonium sulfide for synthesis of dibenzyl sulfide and benzyl mercaptan. The kinetic parameters of the developed model were estimated at different temperatures using an indigenously developed non-linear regression technique based on modified Levenberg–Marquardt algorithm. Sensitivity analysis was then performed under various experimental conditions using the estimated parameters and the results were compared with experimental observations. A good agreement was observed between experimental and calculated values with proper trends of the results. [Copyright &y& Elsevier]

Abstract A kinetic investigation was carried out on the utilization of H 2 S for the synthesis of bis-(2-phenylethyl) sulfide (PES) using ionic liquid catalyst trihexyltetradecylphosphonium chloride as a phase transfer catalyst. The method involved the absorption of H 2 S into aqueous N -methyldiethanolamine (MDEA) which is followed by reaction of this aqueous H 2 S-laden MDEA with organic reactant 2-bromoethylbenzene (2-BEB) to yield PES under liquid–liquid (L–L) phase transfer catalytic condition. The effect of various reaction parameters on the conversion of 2-BEB was studied and the product selectivity was found as 100%. A suitable reaction mechanism involving the possible paths of product formation was proposed. A novel mathematical model was developed to explain the experimental findings. This method will be helpful in overcoming the cost of disposal of organic solvents which have been used often in multiphase organic synthesis. Graphical abstract Unlabelled Image Highlights • An Ionic liquid catalyzes thioetherification of an aromatic halide utilizing H 2 S. • 100% selectivity of thioethers observed with high reaction rate and conversion. • Hydrosulfide found to be main species involved in reaction media. • Kinetic modeling successfully explained the mechanism and kinetics data. • The process can be used an alternative to Claus process. [ABSTRACT FROM AUTHOR]

The present investigation is based on the advancement in hydrogen sulfide (H 2 S) capture and utilization (HSCU). Commercially H 2 S is absorbed efficiently using alkanolamines such as methyldiethanolamine (MDEA). Aqueous H 2 S-rich MDEA is proposed to act as a sulfiding agent for aromatic halides such as p -chlorobenzyl chloride ( p -CBC) to synthesize value-added thioethers. The objective of the present investigation is to synthesize bis-( p -chlorobenzyl) sulfide (BPCBS), a value-added thioether, selectively using p -CBC and H 2 S-laden aqueous MDEA. For the immiscible bi-phasic system, reusable solid phase transfer catalyst, polymer-bound tributylmethylammonium chloride (PBTBMAC) was employed under liquid-liquid-solid (L-L-S) mode in the presence of solvent toluene to enhance the reaction rate and product selectivity. Full conversion of p -CBC was obtained with 100% selectivity towards the desired product BPCBS at optimized specific level of process parameters. The catalyst has shown substantial activity even after three times of reuse, which leads to waste minimization and economic benefits. A generalized empirical kinetic model was developed and successfully validated against the experimental results. The triphasic reaction thus leads to process intensification, waste minimization and selectivity enhancement. The process can be utilized as an alternative to many other HSCU processes to utilize the sour gas in synthesizing value-added chemicals. [ABSTRACT FROM AUTHOR]

An investigation has been done on the utilization of H 2 S for the synthesis of dibenzyl disulfide (DBDS) using Amberlite IR-400 as a phase transfer catalyst. This involves absorption of H 2 S in aqueous monoethanolamine (MEA) followed by reaction of this H 2 S-laden MEA with organic reactant benzyl chloride (BC) to yield DBDS under liquid–liquid–solid (L–L–S) phase transfer catalysis condition. The effect of various parameters on the conversion of BC was studied and the selectivity of desired product was 100% at some level of process parameters. A suitable reaction mechanism has been proposed and a mathematical model has been developed to explain the kinetics of the reaction. Waste minimization was therefore affected with the utilization of H 2 S -laden gas for production of a value-added fine chemical. [ABSTRACT FROM AUTHOR]