1

Abstract Nitration is one of the oldest and the most extensively studied reactions. Nitration reactions, conducted using mixed acid, are extremely exothermic, and tend to be explosive. Moreover, this process has been the most acceptable and favoured route for the manufacture of explosives and precursors for dyes and intermediates and industrial solvents. Aromatic nitrations are performed using “mixed acid” and involve two phases viz. the aromatic phase and the mixed acid phase. It is an accepted proposition that the reaction occurs exclusively in the acid phase in which aromatics are sparingly soluble. The rate controlling step involves electrophilic attack of nitronium ion on the aromatic ring. Reaction is known to be irreversible and first order in concentration of the aromatic species and nitric acid. A large amount of literature highlighting the mechanistic, kinetic, optimization and safety aspects exists. It is necessary to study the reaction kinetics in detail to identify the window of operating parameters which offers safe operation yet desired performance. During our studies on nitration of nitroaromatics, the data suggests that nitroaromatics exist in the form of microemulsion at ambient temperatures. The microemulsion is found to play a major role in the kinetics of polynitration. The reaction of nitro compound (nitrobenzene) and nitric acid occurs at the interface between the organic microphase and acid phase. Whenever nitration of nitroaromatics is conducted at high concentrations of sulfuric acid (> 80% w/w), the system begins to show anomalous behavior. Nitroaromatics have very high solubility in concentrated sulfuric acid. Moreover, the solubility rapidly increases with increase in the concentration of the acid. Winsor III- phase behavior is observed at certain temperature and composition of the system, indicating the existence of microemulsion. The existence of microemulsion of nitroaroamtic species in sulfuric acid is confirmed through the results of a variety of experiments, which include the phase equilibrium data, surface and interfacial tension, viscosity and electrical conductivity of the system and extensive kinetic data, both in batch and continuous (CSTR) modes. Kinetics has been modeled based on the hypothesis of microemulsion. Keywords: Nitration, Microemulsion, Winsor- III phases, Polynitration.

Aromatic Nitration Studies in Higher Strength of Sulfuric Acid Ameya Diwan, Sanjay Mahajani & Vinay Juvekar* Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, -400076, India ameyadiwan@iitb.ac.in, sanjaym@iitb.ac.in , vaj@iitb.ac.in*

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Abstract

Cell cycle is the central process that regulates growth and division. The series of phase specific events (G1->S->G2->M) and phase transitions are governed mainly by Cyclin dependent kinases and its positive and negative regulators. In most of the cancer types the cell cycle regulation is disturbed. Modeling studies can provide insights about the mis-regulation or loss of control at molecular level since the key cell cycle controllers and their interactions are conserved among eukaryotes. We have developed a purely mechanism based model for cell cycle regulation of fission yeast Schizosaccharomyces pombe. The model describes the dynamic evolution of fifteen crucial regulators, their active and inactive states. The molecular events that characterizes the cell division cycle are driven by the different stoichiometric and enzymatic modification that results from the complex network architecture. The distinguishing features of this model are, that this model does not use any condition based phase transitions unlike the existing models, it does not use any total protein concentration and Goldbeter switches to bring switch like response for phase specific activation or inactivation of regulators. For model simulation, parameters were chosen to represent the reported dynamics of the regulators. Cell division time of 150 minutes was observed for wild type cells which is consistent with the experimental studies. In order to validate the model, it was simulated and verified for various known mutants. An input output response based analysis was developed to understand the role of the individual regulators. Such a study would enhance our understanding of control strategies, and biological design principles evolved in cell division process.

Mechanism Based Model Development For Cell Cycle Regulation of Schizosaccharomyces pombe Anbumathi. P1, Sharad Bhartiya1, K.V. Venkatesh1,2

1Department of Chemical Engineering and 2School of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, -400076, India anbumathi_p@iitb.ac.in1

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Abstract

Heavy tracer particles sinking in a flowing medium of light particles of same size are studied by DEM simulations. Using an effective medium argument for buoyant force, we show the existence of an effective buoyancy volume Vbouyant that must be larger than volume of the trace particle Vp. We find that the drag force on the sphere sinking with velocity v in a granular medium of viscosity is given as F=6adragv, where adrag is hydrodynamic radius of the sinking sphere, establishing that Stokes’ law holds for powders as well. This hydrodynamic radius is different from the one obtained from effective buoyancy volume. Using the Stokes-Einstein relation, we define an effective temperature Teff =6adragD, where D is the diffusivity of the particle. Balancing the segregation and diffusion fluxes, we propose a theory for segregation due to density differences for a binary mixture of same size particles. It is shown that density segregation is determined by effective temperature profiles as predicted by the theory. By the means of DEM simulations of binary granular mixtures flowing over an inclined plane, we show that the theory accurately predicts segregation for mixtures of different overall compositions at various inclination angles of the plane. Trace particles of different size however behave differently and with bigger particles of density same as that of the base flow particles rising, questioning the granular buoyancy mechanism of segregation suggested earlier. By detailed analysis of different size and density trace particles, we show that the granular buoyancy can be an appropriate method of looking at the size segregation as well.

Granular Buoyancy, Stokes’ Law and Segregation of Powders Anurag Tripathi*, Devang V. Khakkar Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, -400076, India anurag.r.tripathi@gmail.com *

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Abstract

The process of drying colloidal dispersions, namely, evaporation of the solvent leading to the formation of continuous polymer/metal oxide films is common to a range of important technologies, e.g. forming polymer films from latex dispersions, casting magnetic tapes, encapsulating vitamins in beads, manufacturing photographic film etc. The thickness of the consolidated bed can vary from an order of a micron (i.e. thin films) to an order of meters (i.e. river beds). The particles often are polymer lattices or inorganic oxides, e.g. silica, alumina, or zirconia, and the solvent is normally water, but occasionally a low molecular weight organic solvent. In this work we provide a general framework for studying the consolidation of charged colloids and apply it to case of drying of latex dispersion which contains sub-micron sized particles dispersed in water. Since the final mechanical properties of a colloidal film depend on the nature of the particle packing, understanding the factors influencing consolidation becomes important. Our experiments and simulation show that at lower particle volume fraction surface charge of a particle does have an effect on consolidation. The results of this work are not only applicable to coatings and ceramic processes but also to diverse industrial processes such as waste water treatment where particulate matter is separated from the feed using gravity or centrifugal action. Once the particles consolidate, the liquid menisci results in large (negative) capillary pressures that deforms the packed array of the particles resulting in a stress field across the bed. Our experiments show that the consolidated bed could crack under certain conditions. Hence, we looked at the problem of stress distribution and nucleation of cracks of a thick bed of colloidal particles. We carried out experiments and simulation related to crack propagation and their dependence on evaporation rate. We also have identified critical parameters related to nucleation of crack.

Consolidation of Latex Dispersion Arijit Sarkar∗, Mahesh S. Tirumkudulu Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, -400076, India arijit@che.iitb.ac.in*

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Abstract

E.coli has survived for ages, which is credited to their ability to move away from repellents and move towards attractants. This strategy of movement is well known as chemotaxis. This is done with the help of flagella. E.coli has a sequence of smooth swimming ‘runs’ punctuated by intermittent ‘tumble’. ‘Run’ is for longer time, where the flagella moves counter clock wise (CCW). In ‘tumble’ flagella moves clockwise (CW) which is for fraction of seconds, this helps in effectively randomize the direction of next run. Duration of ‘run’ can last from few fractions of seconds to several minutes depending on the chemo stimulus (attractant or repellent). E.coli cannot measure the gradients and behave as point sensors which posses a kind of memory ( 3 second) that allow them to compare past chemical environment to the current. So the probability of a smooth ‘run’ depends on its immediate surrounding being compared to their chemistry of the previous surrounding which it encountered earlier. Frequency of ‘tumble’ increases as the attractant depletes or repellent concentration increases. But as soon as it detects the condition is improving ‘running’ increases and ‘tumbling is suppressed. This whole phenomenon is molecularly controlled by signal transduction. The movement of bacteria is measured by capillary assay or ring formation on semisolid agar plate. In our study we have investigated E.coli’s movement in presence of chemo attractant (Tryptone, Luria-Bertani broth (LB), Serine, Aspartate, and Glycerol) and chemo repellent (Cobalt Chloride (CoCl2), Nickel Chloride (NiCl2) & Sodium Acetate) in semisolid agar plate by observing the ring formation.

Chemotaxis of E.coli Rajesh Jesudasan*, Mahesh S. Tirumkudulu Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, -400076, India rajeshjesudasan@iitb.ac.in*

6

Abstract

In the vicinity of the surface of a charged body/electrode in contact with an aqueous solution, a thin region of counterions, called electric double layer, exists. The thickness of the electrical double layer is in the range of 1 nm to 1 m . Practically all of the electric field generated by the electrode is screened by the electrical double layer and field is practically zero outside the double layer. The electrical double layer, thus, acts as a barrier against penetration of the field to a longer distance from the electrode surface. The double layer can be completely eliminated by alternating the potential of the electrode at a sufficiently high frequency. The aim of the present work is to understand the dynamics of the double layer subjected to an AC field with variety of waveforms. Idea behind this exercise is not only to eliminate the double layer, but also to make the ions of the same charge to assemble, at high concentration, in the region far away from the electrode so that a very high electric field is generated at that point. With these objectives in mind, a setup has been developed consisting of a signal generator, followed by a high voltage amplifier and a cell with parallel plate electrodes. The potential and the current are measured using a picoscope. Here, we measure the current density and phase lead of the current with respect to potential as functions of the frequency and waveform of the electrode potential. When a sinusoidal potential is applied, the current density and phase lead profile show three distinct regions. In the low frequency region, the current density increases and phase lead decreases with increase in the frequency. It is due to the diminishing of the electrical double layer with frequency. The frequency at which phase lead becomes almost zero called as threshold frequency. At this frequency, the double layer is completely eliminated. Beyond this frequency, the current density and phase lead nearly remains constant with further increase in the frequency over a certain range of frequency. In this region, the system is purely resistive. Beyond this range, the current density and phase lead begins to increase with increase in the frequency. At sufficiently high frequency, the system again starts behaving as pure dielectric. The current density increases linearly with frequency. The phase lead value approaches to the 90 degree. In this region, the ions are in immobilized state, the current density is due to the rotation of the dipoles of water. The theoretical model is also developed to understand in detail about the dynamics of the electrical double layer. The results obtained by simulation are compared to experimental and they are in quite good agreement.

Dynamics of the Electrical Double Layer R. S. Patil*, V. A. Juvekar, Rochish T. and V. M. Naik

Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, -400076, India rspatil108@iitb.ac.in*

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Abstract Underground coal gasification (UCG) is a technique which permits access to coal which either lies too deep underground, or is otherwise too costly to exploit using conventional mining techniques. At the same time, it eliminates many of the health, safety and environmental problems of deep mining of coal. UCG product gas may be used as a chemical feedstock or as fuel for power generation. The UCG cavity is a result of the complete interaction of fluid flow, heat transfer, mass transfer, chemical reactions, water influx, thermo mechanical properties of coal, spalling phenomenon and other geological aspects. The shape and rate of growth of this cavity will strongly impact the important phenomena, such as reactant gas flow patterns, kinetics, temperature profiles, and ultimately determines the quality of the product gas. There is a need for experimental data to characterize the cavity evolution in the UCG process. The goal of our work is to establish a relationship between cavity evolution and various parameters. A systematic methodology is proposed for laboratory scale experiments to mimic the UCG process and empirical correlations are developed to relate cavity volume and three dimensional shapes to various design and operating parameters. In addition to the experimental studies, it is necessary to reduce the computational efforts to get the product gas composition through a complete process model. Computational Fluid Dynamics has been used as a tool to characterize the non-ideal flow patterns by performing residence time distribution (RTD) studies in actual size UCG cavities and the results validated against lab-scale experiments. The new approach of compartment modeling that reduces the computational burden on UCG process simulation has been explored here. The compartment model is developed based on the CFD simulation results and it is validated by comparing the homogeneous water gas shift reaction-enabled steady state CFD simulation results with that of obtained from the steady state flow simulator (i.e. Aspen Plus). Finally, a detailed parametric study on heat and mass transfer coefficients for actual size UCG cavities has been undertaken and the obtained trends validated against well-designed lab-scale experiments. Overall, this research is expected to contribute significantly to the comprehension, optimization and process modeling of the complex UCG process.

Studies on Underground Coal Gasification Daggupati Sateesh*, Preeti Aghalayam, Sanjay M Mahajani Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, -400076, India sateesh@che.iitb.ac.in*

8

Abstract

Metal nanoclusters (1 – 100 nm) are of significance because they exhibit unique physico-chemical properties, very different from those in the bulk. They are used as building blocks for hierarchical materials. These materials can be achieved if the properties of the nanoclusters can be manipulated on all scales (molecular, micro and meso) to incorporate desired characteristics for applications in varied fields ranging from opti-electronic devices, magnetic storage devices, catalysts to medical implants and drug delivery. Wet chemical synthesis is gaining popularity because it provides the flexibility to control nanocluster properties like size, shape and morphology by manipulating the stabilizer parameters like molecular weight, functional groups and concentration. We are interested in understanding the self-assembly process for bulk-synthesis of nanoclusters. In literature, considerable amount of work has been done on how these parameters influence nanocluster properties – however, the stabilization mechanism is not yet fully understood. The processes occurring simultaneously in the system are decomposition, nucleation, growth & aggregation, stabilization and breakage / fragmentation. To get a better understanding of this mechanism we have attempted for the first time, to the best of authors' knowledge, to capture the nucleation and growth pattern using extensive transmission electron microscopy and, more importantly, study how polymers and surfactants influence these. The model system chosen for this purpose was the thermal decomposition of an organo-metallic precursor, octa-carbonyl di-cobalt in an inert atmosphere in the presence of polystyrene/AOT as stabilizer, both dissolved in a common solvent, toluene. The octa-carbonyl di-cobalt decomposes to give highly active nascent cobalt atoms. FTIR was used to monitor the progress of the reaction. TEM images were taken at different stages of the decomposition reaction. These micrographs captured the size and shape of nanoclusters spanning over the growth period. Interesting observations were made which helped us conclude that polymers are definitely involved in the nucleation and growth process of nanoclusters in a complex manner. Chain length plays a critical role in the rate at which nanocluster size decreases. Concentration of both polymer and surfactant has an impact on the formation mechanism.

Capturing the Nucleation and Growth Patterns of Stabilizer-Induced Metal Nanocluster Formation by Thermal Decomposition of Organometallic Precursors Sonia Tikku*, Late Kartic C Khilar, Jayesh Bellare, and Rajdip Bandyopadhyaya Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, -400076, India. sonia.tikku@iitb.ac.in*

9

Abstract

The galactose uptake mechanism in yeast is a well studied regulatory network. The regulatory players in the galactose regulatory mechanism (GAL system) are conserved in Saccharomyces cerevisiae and Kluyveromyces lactis but the molecular mechanisms that occur due to the interactions between them are different. The key differences in the GAL system of K. lactis as compared with S. cerevisiae are, (i) autoregulation of transcriptional activator KlGal4p (ii) dual role of KlGal1p as a metabolizing enzyme as well as a galactose sensing protein (iii) shuttling of KlGal1p between nucleus and cytoplasm (iv) nuclear confinement of KlGal80p (v) KlGAL4 is the only gene in GAL system with one binding site, while remaining genes having two binding sites. A steady-state model was used to elucidate the roles of these molecular mechanisms in the transcriptional response of the GAL system. The steady state results were experimentally validated with measurements for β-galactosidase to represent the expression for genes having two binding sites. Subsequently, the steady state model was extended to determine the dynamic profile of fractional protein expression and was compared with experimental results. The results show that the autoregulation of the activator protein KlGal4p is responsible for the leaky expression of the GAL genes even at high glucose concentrations. Further, the GAL gene expression in K. lactis shows a maximum expression level of only about 35% at high galactose concentration. The low expression levels are due to the fact that the bifunctional protein KlGal1p is limiting in its function towards the induction process in order to cope with the need for metabolizing lactose/galactose. The steady-state model of the GAL system of K. lactis provided an opportunity to compare with the design prevailing in S. cerevisiae. The comparison indicates that existence of a protein, Gal3p, dedicated for sensing of galactose in S. cerevisiae due to genome duplication has resulted in a system which metabolizes galactose efficiently. While presence of glucose, the absence of Gal4p autoregulation help S. cerevisiae completely switch off the GAL system.

Systems Biology of GAL Regulon in Saccharomyces cerevisiae and Kluyveromyces lactis Venkatraman Prabhu, K.V. Venkatesh* Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, -400076, India venks@che.iitb.ac.in*

10

Abstract

Reactive Distillation (RD) combines reaction and distillation in a single unit to offer enhancement in the overall performance of the process. It leads to enhancement in conversion for reversible reactions and selectivity improvement in multiple reaction schemes. The main underlying principle in application of RD for selectivity engineering is to facilitate the separation of selected components and favorably manipulate the composition profiles in the reactive zone to expedite the desired reaction. In the present work, a geometric approach of attainable region (AR), which is already developed for conventional reactor network, is extended further to include representative RD configurations. AR is the set of all compositions that are achievable by a reactor network which may consists of ideal reactors and few representative RD units such as reactive rectification and reactive stripping. A model reaction with van de Vusse scheme (A B C and 2A D) was studied and an algorithm is developed to obtain AR for the given kinetics, feed composition and relative volatilities. AR should be convex with newly defined RD composition vectors on the boundaries should always point inward. The RD vectors emphasize on the need of RD model networking to enlarge the set of attainable compositions until no further enlargement is seen. As an illustration purpose, van de Vusse reaction scheme with unity rate constants and increasing relative volatilities order (αA>αB>αC>αD) is examined. The regions defined by basic RD models viz, reactive rectification and reactive stripping overlap only over a certain conversion range, which implies insufficiency of a single type of RD unit for maximum selectivity towards desired product ‘B’ over the entire conversion range. This invites the necessity of networking of RD models among themselves and possibly with conventional reactors. The AR for corresponding RD network thus obtained for representative case is shown in Fig.A. The dark line represents attainable region, whereas dotted lines correspond to the profiles of reactive stripping and rectification units with varying number of reactive stages.

A Geometric Approach to Reactive Distillation: the attainable region and optimization in concentration space Vinay Amte*, Sanjay M. Mahajani, Ranjan K. Malik Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, -400076, India vinayamte@che.iitb.ac.in*

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Fig. A: Attainable region for the van de Vusse reaction (A B C and 2A D). (relative volatilities: [5 3 1 1], rate constants: [1 1 1], Damkohler number: 0.005)

The results obtained through the algorithm developed above are verified with independent simulation that maximizes selectivity. In almost all different cases of kinetic regime and relative volatilities, RD models perform better than conventional reactors.

Keywords: reactive distillation, attainable region, van de Vusse reaction, composition vector

12

Abstract

First principles models offer better insight into evolution of the plant states and have better prediction capabilities over a wide operating range. Accurate estimation of the states is important for applications like predictive control, fault-diagnosis, etc. In presence of various unmeasured disturbances and noise, the model may not be able to accurately predict the states. The model, therefore, needs to be augmented with an unmeasured disturbance model to generate better estimates, and, in turn, better predictions of the states. In practice, the structure and the parameters of the unmeasured disturbance model are unknown. Moreover, the disturbances could be correlated in time. In this work, given a reliable mechanistic model, a systematic approach is proposed to construct an unmeasured disturbance model using operating input-output data. A chosen subset of unmeasured disturbances, which enter the system dynamics as inputs are modeled as state realizations of a time series model. The disturbance state space model is then combined with the mechanistic model to construct a grey-box state observer. The unknown parameters of the unmeasured disturbance model are identified using prediction error method. The application on a benchmark distillation column indicates the ability of the proposed gray box model to capture the effect of unknown disturbances and noise effectively.

Development of Gray Box Observer for a Distillation Column Vinay A. Bavdekar and Sachin C. Patwardhan* Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, -400076, India bavdekar@iitb.ac.in, sachinp@iitb.ac.in*

13

Abstract Flow cytometry employs hydrodynamic focusing of concentric streams to measure the scattering and fluorescence properties of cells and particles as they pass through laser beams. This work illustrates the applicability of flow cytometry in fields as diverse as cellular analysis and vesicle structure. The first part of the work focuses on cellular assays which include internalization of nanoparticles by NIH 3T3 cells and estimation of intracellular reactive species (2’,7’-dichlorodihydrofluorescein staining) and cell viability (propidium iodide staining) in HL-60 cells treated by retinoic acid-loaded copolymer nanoparticles. In the second part, flow cytometry is used to analyze surfactant micro-vesicle structures. Results indicate successful estimation of nanoparticle internalization by flow cytometry and quantitative assessment of the iROS and cell viability. Further, the technique has been used to distinguish several types of micro-veiscle structures like versosomes, multi-lamellar and uni-lamellar vesicles. Characteristic signatures associated with these structures have been identified and based on these the different populations have been sorted and confirmed by microscopy. The method can thus be used as a probe in a wide variety of areas. Keywords: Flow cytometry, nanoparticles, cell viability, micro-vesicles

Flow Cytometry: One Tool, Diverse Applications Manu Tiwari, Jayesh Bellare* & Sameer Jadhav Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai-400076, India jb@che.iitb.ac.in *