Industrial Distillation Aspects of Diketene

Large-scale distillation is a challenge in many respects. Particularly difficult is the purification by distillation of a compound with limited thermal stability. This article describes various aspects of these difficulties with some possible solutions. Special emphasis is placed on the collaboration of different disciplines to find pragmatic solutions to these challenges. The purification of diketene in quantities of several 1000 ta–1 is an excellent example to illustrate the different requirements. Although the distillation of diketene has been carried out by several companies for many years, there are still some aspects that deserve special attention

Quantitative mapping of chemical compositions with MRI using compressed sensing.

In this work, a magnetic resonance (MR) imaging method for accelerating the acquisition time of two dimensional concentration maps of different chemical species in mixtures by the use of compressed sensing (CS) is presented. Whilst 2D-concentration maps with a high spatial resolution are prohibitively time-consuming to acquire using full k-space sampling techniques, CS enables the reconstruction of quantitative concentration maps from sub-sampled k-space data. First, the method was tested by reconstructing simulated data. Then, the CS algorithm was used to reconstruct concentration maps of binary mixtures of 1,4-dioxane and cyclooctane in different samples with a field-of-view of 22mm and a spatial resolution of 344μm×344μm. Spiral based trajectories were used as sampling schemes. For the data acquisition, eight scans with slightly different trajectories were applied resulting in a total acquisition time of about 8min. In contrast, a conventional chemical shift imaging experiment at the same resolution would require about 17h. To get quantitative results, a careful weighting of the regularisation parameter (via the L-curve approach) or contrast-enhancing Bregman iterations are applied for the reconstruction of the concentration maps. Both approaches yield relative errors of the concentration map of less than 2mol-% without any calibration prior to the measurement. The accuracy of the reconstructed concentration maps deteriorates when the reconstruction model is biased by systematic errors such as large inhomogeneities in the static magnetic field. The presented method is a powerful tool for the fast acquisition of concentration maps that can provide valuable information for the investigation of many phenomena in chemical engineering applications.The authors thank for the financial support by the following grants: Microsoft Research Cambridge, and EPSRC (EP/K039318/1 and EP/K008218/1). Erik von Harbou was the recipient of a scholarship from the German Academic Exchange Service (DAAD).This is the final version of the article. It first appeared from Elsevier via http://dx.doi.org/10.1016/j.jmr.2015.09.01

Model-Based Investigation of the Interaction of Gas-Consuming Reactions and Internal Circulation Flow within Jet Loop Reactors

Jet loop reactors are standard multiphase reactors used in chemical, biological and environmental processes. The strong liquid jet provided by a nozzle enforces both internal circulation of liquid and gas as well as entrainment and dispersion of the gas phase. We present a one-dimensional compartment model based on a momentum balance that describes the internal circulation of gas and liquid phase in the jet loop reactor. This model considers the influence of local variations of the gas volume fraction on the internal circulation. These local variations can be caused by coalescence of gas bubbles, additional gas-feeding points and gas consumption or production. In this work, we applied the model to study the influence of a gas-consuming reaction on the internal circulation. In a comprehensive sensitivity analysis, the interaction of different parameters such as rate of reaction, power input through the nozzle, gas holdup, reactor geometry, and circulation rate were investigated. The results show that gas consumption can have a significant impact on internal circulation. Industrially relevant operating conditions have even been found where the internal circulation comes to a complete standstill

Physico-Chemical Properties of LiFSI Solutions I. LiFSI with Valeronitrile, Dichloromethane, 1,2-Dichloroethane, and 1,2-Dichlorobenzene

Lithium bis(fluorosulfonyl)imide (LiFSI) is a novel electrolyte for lithium-ion batteries. Valeronitrile (VN) is a good solvent for LiFSI, and dichloromethane (DCM), 1,2-dichloroethane (DCE), and 1,2-dichlorobenzene (DCB), are interesting antisolvents for crystallization. Physico-chemical data for the design of LiFSI production processes, in which these components are used, is lacking. Therefore, the solubility of LiFSI in VN, as well as in binary solvent mixtures VN + (DCM, DCE, DCB) was measured at temperatures between 278 and 343 K and concentrations of LiFSI up to 0.52 mol mol(-1). Furthermore, vapor-liquid equilibria of the systems VN-DCE (at 200 mbar) and VN-DCB (at 200, 300, and 450 mbar) were studied. Also, the density and shear viscosity of solutions of LiFSI in VN were measured at temperatures between 293 and 333 K and concentrations of LiFSI up to 0.5 mol mol(-1)

Physicochemical Properties of LiFSI Solutions II: LiFSI with Water, MTBE, and Anisole

This article is the second in a series in which the thermodynamic properties of solutions of lithium bis(fluorosulfonylimide (LiFSI) are investigated. The solvents that are considered here are methyl tert-butyl ether (MTBE) and water (H2O), which are good solvents for LiFSI, and anisole, which is an antisolvent for LiFSI. The solubility of LiFSI in MTBE, as well as in the binary solvent mixture MTBE-anisole, was measured at temperatures of between 283 and 303 K and concentrations of LiFSI of up to 0.47 mol mol(-1). Furthermore, the liquid-liquid equilibrium of the system LiFSI-MTBE-H2O was studied at 293 K and ambient pressure. Moreover, the density and shear viscosity of solutions of LiFSI in MTBE were studied at temperatures between 273 and 308 K and concentrations of LiFSI up to 0.4 mol mol(-1)

Physico-chemical Properties of Solutions of Lithium Bis(fluorosulfonyl)imide (LiFSI) in Dimethyl Carbonate, Ethylene Carbonate, and Propylene Carbonate

Battery performance strongly depends on the choice of the electrolyte-solvent system. Lithium bis(fluorosulfonyl)imide (LiFSI) is a highly interesting novel electrolyte. Information on physico-chemical properties of solutions of LiFSI, however, is scarce. Therefore, the density, shear viscosity, and electrical conductivity of solutions of LiFSI in three pure solvents that are interesting for battery applications: dimethyl carbonate (DMC), ethylene carbonate (EC), and propylene carbonate (PC), were studied experimentally at temperatures between 273 K and 333 K at 1 bar and concentrations of LiFSI up to 0.45 mol mol−1 in the present work. Empirical correlations of the experimental data are provided. The comparison of the data of this work with the corresponding LiPF6 data underpins the attractiveness of LiFSI as an electrolyte in lithium ion batteries

Electrical Conductivity of Solutions of Lithium Bis(fluorosulfonyl)imide in Mixed Organic Solvents and Multi-objective Solvent Optimization for Lithium-ion Batteries

Lithium bis(fluorosulfonyl)imide (LiFSI) is an interesting novel electrolyte for lithium-ion batteries. In the present work, the electrical conductivity of solutions of LiFSI in binary and ternary mixtures of the solvents dimethyl carbonate (DMC), ethylene carbonate (EC) and propylene carbonate (PC) was studied experimentally for concentrations of LiFSI up to 0.2 mol mol(-1) at ambient pressure and temperatures between 293 and 333 K. Information on the electrical conductivity of LiFSI in the pure solvents DMC, EC, and PC is available from previous work. An empirical correlation of the electrical conductivity a of the studied solutions of LiFSI is presented that describes the dependence of a on the LiFSI concentration, the solvent composition, and the temperature. Based on this correlation, a multi-objective optimization of the LiFSI concentration and the solvent composition was carried out with two conflicting objectives relevant to the performance and costs of batteries: maximizing electrical conductivity and minimizing the amount of the expensive electrolyte LiFSI. The solubility limits of the ternary solvent system DMC-EC-PC were included in the optimization as constraints. The multi objective optimization applied here, is shown to be useful for obtaining a rational basis for decision-making in the design of electrolyte solutions for batteries

Short-cut Method for Assessing Solvents for Gas Cleaning by Reactive Absorption

A new short-cut method (NoVa) for assessing solvents for gas cleaning by reactive absorption is presented. It considers the absorption / desorption cycle using the assumption of infinite number of stages in both columns. For a given feed and removal rate, the method yields an estimate for the specific regeneration energy q as a function of the solvent circulation rate L/G. The sole solvent-dependent input consists of two correlations describing the gas solubility at absorber and desorber conditions and estimates of caloric properties. Furthermore, a simple equation (SolSOFT) for correlating the gas solubility as a function of the gas loading of the solvent is presented. A theoretical analysis of the process reveals general properties of the dependency of q on L/G. The NoVa method is described and tested using amine-based solvents for post combustion carbon capture as examples

Reaction Monitoring by Benchtop NMR Spectroscopy Using a Novel Stationary Flow Reactor Setup

A flow reactor setup for noninvasive monitoring of reactions using a compact benchtop nuclear magnetic resonance (NMR) spectrometer is presented, in which a tubular flow reactor is inserted into the bore of the NMR spectrometer and operated at stationary conditions. To monitor the composition change of the reaction mixture in the flow reactor, the entire reactor is moved to different longitudinal positions in the bore. As the flow is stationary, the composition of the reaction mixture does not change with time at a fixed reactor position. Thus, also time-consuming 2D NMR techniques can be applied to elucidate unknown products. As quantitative information is obtained directly from the NMR spectrum without calibration, the method is also appropriate for quantifying substances that are unstable as pure components. As test cases, two esterification reactions, the formation of methyl formate and the formation of methyl acetate from the pure alcohols and acids, were investigated using this technique. In addition, three 2D NMR pulse sequences (H–H–COSY, HETCOR, and HMBC) were applied in flow. The comparison of the results of the present work to literature data shows that the new method gives reliable results

Reactive distillation in a dividing-wall column: Model development, simulation and error analysis

A process model of a reactive dividing wall column process is developed and tested by comparing simulation results to data from pilot-plant experiments. In general, the experimental data and the model prediction agree well in a simple comparison. By means of a sensitivity and error analysis both the influence of the choice of the model and the influence of uncertainties of the input parameters on the simulation results are studied. It is shown that the insight gained by such an enhanced analysis by far exceeds that from a simple comparison, and that such a simple comparison can easily lead to erroneous conclusions