Characteristics of a Confined Impinging Jet Reactor: Energy Dissipation, Homogeneous and Heterogeneous Reaction Products, and Effect of Unequal Flow

Amidation Reaction System: Kinetic Studies and Improvement by Product Removal

The amidation reaction to produce fatty acid diethanolamide is an important unit process to produce surfactants from renewable sources rather than from petroleum sources. Amidation is a liquid-phase reaction between diethanolamine with a fatty acid methyl ester. Since the reaction is reversible, the conversion is limited by equilibrium, the side product being methanol, which is volatile. Hence, mass transfer effects need to be considered in the interpretation of kinetic data. Further, the elimination of methanol can help to shift the reaction forward. Thus, the process has the potential for process intensification. This paper provides a batch reactor model to interpret the simulation data and includes mass transfer effects analyzed using a dimensionless mass transfer parameter (α_lg). Using values of this parameter greater than 4 leads to an equilibrium model where the methanol partial pressure in the bulk gas approaches that at the interface. Using this model, the kinetic and equilibrium parameters for the amidation reaction were determined using experimental data in the first part of this study. The experimental data for fitting the parameters are obtained from a closed batch reactor operated with an initial pressure of 1 bar and a temperature range of 70-80 °C. The second part of the paper examines two process-intensification concepts-viz., inert gas and vacuum stripping of methanol from the reactor-and simulates the process in the form of mass-transfer-based models. Improvement in the final conversion was demonstrated in both approaches, and predictions of the vacuum stripping model are in good agreement with the experimental results. Thus, the developed vacuum stripping model is useful for accurate analysis and design of a reactor with vacuum stripping. The novelty of the work is obtaining rate and reaction equilibrium constants, enthalpy of reaction, and liquid activity coefficient for amidation, which have no prior reporting, and providing the viability of options for side product removal. The applied modeling approaches and the experimental facilities and methods are established.

Production of Oil-in-Water Emulsions with Varying Dispersed-Phase Content using Confined Impinging Jet Mixers

This work reports for the first time on the use of Confined Impinging Jet Mixers (CIJM) for the production of emulsions with dispersed-phase content up to 80 wt %, in both the surfactant-poor and -rich regimes, following the exposure to varying CIJM hydrodynamic conditions. It was observed computationally and experimentally that the CIJM capacity resulted strictly dependent on the mass jet flow rate (W _jet > 176 g/min) and the pre-emulsion droplet size (>10 μm). CIJM emulsification performance remained (almost) unaffected by the variation in the oil mass fraction. All systems showed the lowest droplet size (∼8 μm) and similar droplet size distributions under the highest W _jet. Conditionally onto the Tween20 availability, the emulsion d _3,2 was primarily determined by formulation characteristics in the surfactant poor-regime and by the CIJM energy dissipation rate in the surfactant-rich regime. In conclusion, this study offers further insights into the CIJM suitability as a realistic alternative to already-established emulsification methods.

Application of flash nanoprecipitation to fabricate poorly water-soluble drug nanoparticles

Nanoparticles are considered to be a powerful approach for the delivery of poorly water-soluble drugs. One of the main challenges is developing an appropriate method for preparation of drug nanoparticles. As a simple, rapid and scalable method, the flash nanoprecipitation (FNP) has been widely used to fabricate these drug nanoparticles, including pure drug nanocrystals, polymeric micelles, polymeric nanoparticles, solid lipid nanoparticles, and polyelectrolyte complexes. This review introduces the application of FNP to produce poorly water-soluble drug nanoparticles by controllable mixing devices, such as confined impinging jets mixer (CIJM), multi-inlet vortex mixer (MIVM) and many other microfluidic mixer systems. The formation mechanisms and processes of drug nanoparticles by FNP are described in detail. Then, the controlling of supersaturation level and mixing rate during the FNP process to tailor the ultrafine drug nanoparticles as well as the influence of drugs, solvent, anti-solvent, stabilizers and temperature on the fabrication are discussed. The ultrafine and uniform nanoparticles of poorly water-soluble drug nanoparticles prepared by CIJM, MIVM and microfluidic mixer systems are reviewed briefly. We believe that the application of microfluidic mixing devices in laboratory with continuous process control and good reproducibility will be benefit for industrial formulation scale-up.

Inflow boundary conditions determine T-mixer efficiency

We report on a comprehensive experimental–computational study of a simple T-shaped mixer for Reynolds numbers up to 4000.

Microfluidization of Graphite and Formulation of Graphene-Based Conductive Inks

We report the exfoliation of graphite in aqueous solutions under high shear rate [∼ 10⁸ s^-1] turbulent flow conditions, with a 100% exfoliation yield. The material is stabilized without centrifugation at concentrations up to 100 g/L using carboxymethylcellulose sodium salt to formulate conductive printable inks. The sheet resistance of blade coated films is below ∼2Ω/□. This is a simple and scalable production route for conductive inks for large-area printing in flexible electronics.

Formation of Organic Molecular Nanocrystals under Soft Confinement

Methods to produce nano-sized organic molecular crystals in thin films are of great interest in the pharmaceutical industry due to the potential benefit of increased solubility of poorly soluble drugs and the advantages of film-based dosage forms over traditional tablet/capsule-based dosage form. One method to directly form organic nanocrystals is by crystallization in confined environments where the overall crystallization volume is constrained. We report the use of a novel solution impregnation method to form nanocrystals in polymer matrices with various microstructures in order to study the structure of the confined nanocrystals and the role of soft confinement and polymer chemistry on the nucleation process of nano-sized crystals. The particle diameter correlates with the microstructure of the polymer matrices and the nucleation kinetics. In addition, by carefully choosing the experimental conditions and the polymer matrix, polymorph control of nanocrystals can be achieved. Solid-state nuclear magnetic resonance (ssNMR) was used to examine the local structure of nanocrystals inside the polymer matrices and crystal polymer interactions. This method may serve as a novel formulation method to obtain nanocrystals of poorly soluble active pharmaceutical ingredients (APIs) for pharmaceutical industry.

Test Reactions to Study Efficiency of

Effects of mixing on the course of fast chemical reactions are relatively well understood, especially in homogeneous systems. This enables to design and operate chemical reactors with the goal to achieve a high yield of a desired product and use systems of complex reactions as a chemical probe (chemical test reactions) to identify progress of mixing and quality of mixture. Recently, a number of studies have focused on the application of chemical test reactions to identify energy efficiency of mixing, being a convenient way of comparing mixers and reactors in terms of their mixing efficiency. This review offers a presentation of chemical test reactions available in the literature and methods of applications of test reactions to identify the energy efficiency of mixing. Also methods to assess the extent of micromixing by measuring product distribution or segregation index, and to determine the time constant for mixing are presented for single phase homogeneous systems and two-phase liquid-liquid systems.

Formation of Organic Molecular Nanocrystals under Rigid Confinement with Analysis by Solid State NMR

Crystallization in rigid confinement is a promising method to obtain organic molecular nanocrystals. However, the crystallization behavior and the related characterization methods are not well studied. Here we present a systematic study of the nucleation of organic molecular nanocrystals in rigid pores. Four different compounds were studied, ibuprofen, fenofibrate, griseofulvin, and indomethacin, which range from simple to complex molecules. Solid-state Nuclear Magnetic Resonance (NMR) was employed to analyse the structure of these compounds inside pores which are difficult to characterize by other analytical methods. We successfully demonstrated the production of nano-crystalline ibuprofen, fenofibrate and griseofulvin in porous silica particles with ~ 40 nm pores. These nanocrystals showed significant enhancement in dissolution rates. These results help advance the fundamental understanding of nucleation under rigid confinement and may lead to potential applications in developing new formulations in the pharmaceutical industry.