Process development using oscillatory baffled mesoreactors

Process development often involves the optimisation of a process or the study of reaction kinetics in order to improve product yields and selectivities whilst increasing process robustness. By conducting screening experiments in continuous flow, superior heat/mass transfer rates, better controllability and reduced processing volumes compared to conventional batch processing can be realised. Additionally, flow chemistry can help minimise the challenge of scale-up. This project involves the application of the mesoscale oscillatory baffled reactor as a flow chemistry screening platform. The “meso-OBR” is a ~5 mm i.d. tubular reactor that can exploit the benefits of flow chemistry at µL/min to mL/min throughputs. The project is divided into a number of different research areas outlined below.

1. Investigation of the fluid mechanics of helically baffled oscillatory flow

OBRs operate through the superposition of oscillatory motion on to a net flow of liquid in a baffled tube. The oscillation of liquid induces vortex formation behind the baffles, giving many well-mixed tanks-in-series. Thus, a good approximation of plug flow can be realised. The use of a helical coil in the place of more conventional baffles (such as orifice baffles and smooth-constrictions) enables a wide range of oscillation intensities to be used to achieve plug flow. This is believed to be because of an additional swirling element to the flow. This study aims to investigate these flows numerically (via CFD simulation) and experimentally (via PIV).

2. Development of a hybrid heat pipe-OBR for the purpose of temperature screening and passive thermal management of exothermic reactions

Heat pipes are heat transfer devices that rely on the latent heat of evaporation and condensation of a working fluid to generate very high thermal conductivities with minimal temperature differences. In this work, a stainless steel heat pipe meso-OBR hybrid (“HPOBR”) has been developed for screening the effects of reaction temperature in flow, and passively controlling the temperature of exothermic reactions. A central composite design of experiments method was used to examine the effects of Ren, Reo and methanol fill ratio for the solventless imination reaction between benzaldehyde and n-butylamine. It has been shown that 13-fold improvements in reaction rate and 20-fold reductions in processing volume (compared to conventional solvent operation) can be realised.

3. Screening reaction kinetics information of an imination reaction from in-situ FTIR data

“Multi-steady state” reactor operation involves maintaining a particular set of operating conditions whilst measuring the output, before changing the operating conditions and repeating the measurements. This allows the effects of many different parameters such as residence time, reaction molar ratio, temperature, etc to be quickly observed in order to construct a robust model of the reaction. In this study, this screening methodology has been applied in flow using the HPOBR and similar jacketed meso-OBR in order to obtain the kinetics of the solventless imination reaction between benzaldehyde and n-butylamine.

4. Application of 3D printing to new reactor development

Fluidic oscillators are devices that contain no moving parts, but are able to provide oscillatory/pulsating flows using internal feedback interactions. This part of the PhD project has investigated the impact of different geometrical parameters on the flow-switching frequencies that can be obtained. One of the ultimate goals is to develop a no-moving-parts OBR. The development of these devices is bolstered by 3D printing.

Publications

1. McDonough J.R., Phan A.N., Harvey A.P. Rapid process development using oscillatory baffled mesoreactors – A state-of-the-art review. Chemical Engineering Journal 265 (2015) 110-121

2. McDonough J.R., Phan A.N., Reay D.A., Harvey A.P. Passive isothermalisation of an exothermic reaction in flow using a novel “Heat Pipe Oscillatory Baffled Reactor (HPOBR)”. Chemical Engineering and Processing 110 (2016) 201-213 (http://authors.elsevier.com/a/1Tyr9w2gqcfu7)

3. McDonough J.R., Law R., Kraemer J., Harvey A.P. Effect of geometrical parameters on flow-switching frequencies in 3D printed fluidic oscillators containing different liquids. Chemical Engineering Research and Design 117 (2017) 228-239 (https://authors.elsevier.com/a/1T-Wkx-vu8p1e)

4. McDonough J.R., Ahmed S.M.R., Phan A.N., Harvey A.P. A study of the flow structures generated by oscillating flows in a helical baffled tube. Currently under review in Chemical Engineering Science

Conferences

1. McDonough J.R., Phan, A.N., Harvey A.P. Solvent free synthesis of an exothermic imination reaction passively cooled in flow using a heat pipe oscillatory baffled reactor (HPOBR). [Oral Presentation]. In International Symposium on Green Chemistry, La Rochelle, France, 2017

2. McDonough J.R., Ahmed S.M.R., Phan A.N., Harvey A.P. A study of the flow structures generated by oscillating flows in a helically baffled tube. [3-Minute Research Highlight Talk]. In ChemEngDayUK 2017, University of Birmingham, UK, 2017

3. McDonough J.R., Ahmed S.M.R., Phan A.N., Harvey A.P. A study of the flow structures generated by oscillating flows in a helically baffled tube. [Poster]. In ChemEngDayUK 2017, University of Birmingham, UK, 2017

4. McDonough J.R., Law R., Short L., Kraemer J., Harvey A.P. Applications of 3D printed fluidic oscillators to process intensification. [Poster]. In ChemEngDayUK 2017, University of Birmingham, UK, 2017

5. McDonough J.R., Phan A.N., Harvey A.P. Isothermalisation: passive temperature flattening of an exothermic reaction using a heat pipe oscillatory baffled reactor (HPOBR). [Oral Presentation]. In 33rd HEXAG Meeting, Newcastle, UK, 2016

6. McDonough J.R., Phan A.N., Harvey A.P. Development of a hybrid heat pipe reactor or continuous temperature screening and passive reaction exotherm isothermalisation. [Poster]. In 5th European Process Intensification Conference, Nice, France, 2015