FLOW CHEMISTRY
using technologies from DEC Continuous Processing, using a DN50 Inverted Pocket Filter * to screen parameters before scaling up via a DN110 Astro Filter *.
The technology enables fast filtration followed by washing steps and hot air or nitrogen drying. We managed to speed up the process by a factor of ten compared to the current batch processes.
Continuous hydrogenations
An additional area of interest for MEPI is related to gas / liquid( G / L) reactions. In addition to elementary fluorinations run in silicon carbide plate heat exchange flow reactors, which we pioneered in 2009, MEPI started to investigate flow hydrogenations in 2019.
The first idea was to use heat exchange reactors, but having free flowing traditional palladium-carbon catalysis led to clogging issues. So, when we discovered that our neighbours, the LHFA laboratory from Toulouse University, had patented some liquid catalysts using precious and non-precious metal nanoparticles in glycerol-based stabilised collodions, we ran new flow experiments. 4
We started using plate exchange reactors, but faced issues with a proper feeding of the hydrogen through the system, often creating flushing effects, which is detrimental to an efficient G / L quality and time contacts.
We then tested tube-in-tube technology, with hydrogen feeding through a membrane tube where the reaction media is flowing. That gave excellent results but there were still the challenges of recycling the catalyst and scaling up the technology.
Recently, we began a cooperation with the French flow reactor manufacturer Khimod. This tubular technology offers seamless scale-up. The tubes can be fed with catalytic static mixers or filled with catalysts in a packed-bed approach. The catalytic system stays in the reactor during production and can be recycled or regenerated when its efficiency starts to decline.
MEPI is currently investing in a new line, and associated safety devices, that will be able to supply hydrogen pressures up to 50 bar, rendering possible harsher hydrogenations.
A complementary approach is to use the membrane tower hydrogenator from Zaiput offering huge catalyst density per unit of reaction volume,. This enables the reaction to run in flow at lower pressures and lower temperatures, harsher conditions that are compulsory in a traditional batch strategy.
An initial Raney Nickel hydrogenation run in batch over 24 hours at 30 bar and 200 ° C was transposed to flow at 50 ° C and 5 bars in few minutes. These milder conditions offer improved safety and economic conditions. ●
*- DN50 Inverted Pocket Filter and DN110 Astro Filter are registered trademarks of DEC Continuous
Processing References: **- Khimod K1 is a registered trademark of Khimod 1: Org. Process Res. Dev., February 2017. 2: Chemistry Today, July 2012. 3: Specialty Chemicals Magazine, June 2014. 4: AIChE J., 2019, e16752.
J j
Laurent Pichon
CHAIR
MEPI l. pichon @ mepi. fr www. mepi. fr
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