@article { ISI:000321965700043, title = {Direct contact heat transfer via injecting volatile liquid in a hot liquid pool: generation and motion of bubbles}, journal = {Chemical Engineering Science}, volume = {100}, year = {2013}, note = {11th International Conference on Gas-Liquid and Gas-Liquid-Solid Reactor Engineering (GLS) Held in Conjunction with 9th World Congress on Chemical Engineering (WCCE) / Asian Pacific Conference on Chemical Engineering (APCChE), Seoul, SOUTH KOREA, AUG 19-22, 2013}, month = {AUG}, pages = {421-432}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

Direct contact heat transfer via injection of volatile liquid is an effective strategy for removing heat from a viscous liquid pool. The rapid evaporation effectively removes heat and the generated bubbles move quickly to the top surface. In this paper, we present an experimental and phenomenological analysis of the evaporation of a drop in a slightly miscible liquid. The phenomenon was visualized using a two-dimensional transparent experimental set-up with a single inlet at the bottom. The videos were used to estimate bubble dimensions, its rise velocity, distance from the detachment point, and fraction of vapor and the liquid phases in the evaporating drop. The initial drop size, temperature difference between the hot fluid and the low boiling solvent and the nucleation rate governed the rate of change of the drobble (combined entity of drop and bubble) diameter and its rise velocity. A phenomenological model describing transient behavior of drobble (motion and heat transfer) is developed. The transient variation in the interfacial areas for heat transfer and the projected area were found to have effect on the predictions. The model and results will also provide useful basis for extending the work towards better understanding of direct contact heat transfer in viscous systems like polymerization reactors. (C) 2013 Elsevier Ltd. All rights reserved.

}, keywords = {Bubble, Direct contact HT, Drobble, Drop, Evaporation, Slightly miscible liquids}, issn = {0009-2509}, doi = {10.1016/j.ces.2013.02.057}, author = {Kulkarni, Amol A. and Ranade, Vivek V.} } @article { ISI:000342087400004, title = {Discontinuous two step flow synthesis of m-aminoacetophenone}, journal = {Green Processing and Synthesis}, volume = {3}, number = {4}, year = {2014}, month = {AUG}, pages = {279-285}, publisher = {WALTER DE GRUYTER GMBH}, type = {Article}, address = {GENTHINER STRASSE 13, D-10785 BERLIN, GERMANY}, abstract = {

The continuous flow nitration of acetophenone followed by reduction of the meta isomer has been demonstrated using simple tubular reactors. Because of ease of separation of the desired isomer from the first step, both steps are made continuous, but separately. The continuous flow nitration was carried out in a safe manner in a shorter reaction time than the conventional approach. The choice of micromixer was seen to affect the performance of the nitration reaction. The effect of different parameters on the yield of the desired product was studied. The reduction step with sodium sulfide was found to be economical and could be carried out efficiently at 70 degrees C using sodium sulfide in ethanol, using a silicone tube. Both steps were demonstrated for several hours, yielding a sufficiently large quantity (similar to 100 g) of m-aminoacetophenone at lab scale in a single day using simple tubular reactors.

}, keywords = {acetophenone, continuous flow synthesis, microreactor, nitration, reduction}, issn = {2191-9542}, doi = {10.1515/gps-2014-0043}, author = {Tibhe, Jagdish and Sharma, Yachita and Joshi, Ramesh A. and Joshi, Rohini R. and Kulkarni, Amol A.} } @article {47591, title = {Design and scale-up of continuous di-nitration reaction using pinched tube flow reactor}, journal = {Journal of Flow Chemistry}, volume = {11}, year = {2021}, month = {SEP}, pages = {611-624}, type = {Article}, abstract = {Scale-up of the di-nitration reaction for synthesis of selective herbicide pendimethalin using only nitric acid in continuous flow is presented in this work. This work showcases an approach for smooth scale-up for an herbicide for a production capacity of 50 kg/day using a pinched tube reactor. The approach begins with the batch experiments followed by flow synthesis using a 1/8-inchSS316 helical coil tube where kinetics of the di-nitration was determined, and process optimization was done. Systematic approach was followed for quantification of heat transfer, mass transfer and residence time distribution and scale-up. Detailed scale-up methodology is presented with effect of relevant parameters for successful scale-up. Modular pilot plant with inline quenching, extraction and separation are some of the salient features presented in this work.}, keywords = {continuous flow, nitration, Pinched tube, RTD, scale-up}, issn = {2062-249X}, doi = {10.1007/s41981-021-00182-1}, author = {Hussain, Arshad and Sharma, Mrityunjay and Patil, Suneha and Acharya, Roopashree B. and Kute, Mahesh and Waghchaure, Aishwarya and Kulkarni, Amol A.} } @article {48679, title = {Direct amidation of acids in a screw reactor for the continuous flow synthesis of amides}, journal = {Chemical Communications}, volume = {59}, year = {2023}, month = {JUL }, pages = {9231-9234}, type = {Article}, abstract = {

A simple and efficient solvent-free protocol for continuous flow synthesis of amides at room temperature is developed using easily available starting materials. N-(3-Dimethylaminopropyl)-N \& PRIME;-ethylcarbodiimide hydrochloride (EDC.HCl) was used as the reagent for the formation of an amide bond without using any metal catalyst or additives. A jacketed screw reactor when operated over a residence time of 30 300 s helped achieve almost complete conversion. This approach is extended for the synthesis of 36 derivatives and 2 bioactive molecules using different substrates having different aliphatic mono and di-acids as well as aromatic acids, including aromatic hetero-acid compounds and phenyl hydrazine. The target amide was scaled up to 100 g with an average 90\% yield.

}, issn = {1359-7345}, doi = {10.1039/d3cc02402d}, author = {Atapalkar, Ranjit S. and Kulkarni, Amol A.} } @article {48916, title = {Dynamics of drop formation in the presence of interfacial mass transfer}, journal = {Langmuir}, volume = {39}, year = {2023}, month = {AUG}, pages = {12627-12639}, type = {Article}, abstract = {

The dynamics of drop formation have been investigated in the presence of interfacial mass transfer through controlled flow visualization experiments. The mixtures of n-hexane (solvent) and acetone (solute) were used as a dispersed phase, having different initial compositions varying over a broad range. Drops were formed at the submerged position in the continuous phase (water) at the same operating flow conditions. The unsteady force balance model is developed to analyze the implications of the simultaneously occurring interfacial transfer of the solute on the formation dynamics in real time, and predictions are validated with experimental results. Based on initial compositions, the analysis of the transient drop shape shows a sharp transition in the drop formation regime. At lower initial solute concentrations, i.e., phi(0) \< 0.2, axisymmetric drop formation occurs and the interfacial solute transfer has negligible effects on the formation dynamics. Over an intermediate range of solute concentrations, i.e., 0.2 \< phi(0) \< 0.5, Marangoni instability is triggered along the evolving interface, and therefore, the interface deformations and contractions occur during the drop formation. At phi(0) = 0.5, the drop takes highly nonaxisymmetric shapes and remains away from equilibrium until its detachment from an orifice. For phi(0) \> 0.5, the spontaneous ejection of plumes of the solute results in the rapid generation of multiple droplets of smaller size. This work shows that higher solute concentration gradients not only lead to faster solute transport but also induce strong interfacial instability simultaneously. Thus, the coupled effects of transient change in composition and fluid properties govern the drop size and its formation time in such systems under non-equilibrium.

}, issn = {0743-7463}, doi = {10.1021/acs.langmuir.3c01309}, author = {Khan, Muzammilanwar S. and Kulkarni, Amol A.} }