Scale-Up Investigation of the Continuous Phase-Transfer-Catalyzed Hypochlorite Oxidation of Alcohols and Aldehydes

The use of bleach to oxidize alcohols with the aid of a phase-transfer catalyst (PTC) offers several benefits over traditional oxidants: low material cost, mild reaction conditions, and no metallic waste. Mass transport limitations often dictate overall reaction rates of such PTC reactions, and continuous-flow reactors with superior mass and heat transport performance are consequently used to enhance their rates. Three PTC hypochlorite oxidation reactions are chosen to illustrate scaling of PTC reactions from microfluidic to mesoscale systems [Corning Low Flow Reactor (LFR) and Advanced Flow Reactor (AFR)]. The successful scaling from microliters per hour in microreactors to intermediate milliliters per minute without sacrificing mass transport performance leads to significant increases in production rate and constitutes an efficient flow reactor scaling approach. The production rate increases up to 700 times in the scaling process from a spiral microreactor to the LFR and then to the AFR

Design, Execution, and Analysis of Time-Varying Experiments for Model Discrimination and Parameter Estimation in Microreactors

Time-varying, or dynamic, experiments can produce richer data sets than sequences of steady-state experiments using less material and time. A case study demonstrating this concept for microreactor experiments is presented. Beginning with five kinetic model candidates for the reaction of phenylisocyanate with <i>t</i>-butanol, an initial dynamic experiment showed that two of the five models gave a similar quality of fit to the experimental data, whereas the remaining three gave significantly poorer fits. Next an optimal experiment was designed to discriminate between the remaining two models. This drove the two models to differ significantly in quality, leaving a single model and a set of kinetic parameter values that adequately described the data. This method can be applied to future kinetic studies to reduce material use and experimental time while validating a dynamic model of the physics and chemical kinetics

Development of a Multi-Step Synthesis and Workup Sequence for an Integrated, Continuous Manufacturing Process of a Pharmaceutical

The development and operation of the synthesis and workup steps of a fully integrated, continuous manufacturing plant for synthesizing aliskiren, a small molecule pharmaceutical, are presented. The plant started with advanced intermediates, two synthetic steps away from the final active pharmaceutical ingredient, and ended with finished tablets. The entire process was run on several occasions, with the data presented herein corresponding to a 240 h run at a nominal throughput of 41 g h^–1 of aliskiren. The first reaction was performed solvent-free in a molten condition at a high temperature, achieving high yields (90%) and avoiding solid handling and a long residence time (due to higher concentrations compared to dilute conditions when run at lower temperatures in a solvent). The resulting stream was worked-up inline using liquid–liquid extraction with membrane-based separators that were scaled-up from microfluidic designs. The second reaction involved a Boc deprotection, using aqueous HCl that was rapidly quenched with aqueous NaOH using an inline pH measurement to control NaOH addition. The reaction maintained high yields (90–95%) under closed-loop control despite process disturbances