Flow Chemistry FAQs

Flow chemistry (or continuous manufacturing) carries out reactions continuously in small tubular reactors (or small stirred tanks) until the desired production volume is achieved, rather than in the large, fixed-volume vessels used in traditional batch processing. By enabling reactions to occur on a micro-scale in a continuous manner, flow technology gives chemists far tighter control over temperature, mixing, and residence time. This makes it possible to run reactions that are difficult, hazardous, or simply inefficient in batch, a key reason the industry has been adopting the technology at an exponential rate.

The two approaches differ in how reactions are run and controlled. Batch processing carries out unit operations in discrete steps, each in a single large batch, while flow runs the reaction continuously. Compared with batch, continuous flow addresses several inherent limitations:

• Heat & mass transfer: flow offers efficient heat exchange and mixing, versus the inefficient transfer common in large batch vessels.
• Process safety: small reactor volumes and continuous removal of high-energy intermediates increase safety for many chemical processes.
• Productivity: no downtime for harvesting, cleaning, and refilling between batches.
• Quality: continuous monitoring reduces batch-to-batch variability and improves product quality and yield.
• Flexibility: continuous, on-demand production enables fast scale-up with control over volumes.

Published reviews on continuous-flow pharmaceutical manufacturing and synthetic organic flow chemistry highlight broad applicability across many reaction classes, particularly where enhanced heat and mass transfer, precise residence-time control, improved safety, and real-time monitoring are beneficial. Chemistries particularly well suited to continuous processing include:

• Thermal reactions (cyclization, rearrangements) and high-temperature reactions
• Cryogenic reactions
• Photo halogenation (using Blue LED and UV light) and photo oxidation
• Nitration and diazotization
• Hydrogenation (fixed-bed)
• Preparation of high-energy intermediates and azides (e.g., for triazole synthesis)
• Handling of hazardous gaseous reagents such as Cl₂, Br₂, F₂, and CNBr
• Preparation of organometallic reagents, like Grignard reagents and organo-zincates
• SP² – SP³ and other C–C bond-forming reactions, like Fürstner and Negishi couplings

Flow chemistry delivers value across safety, quality, cost, and sustainability:

• Increased process safety: hazardous chemistry is contained in small reactor volumes with tight control.
• Improved product quality: continuous monitoring ensures consistent, high-quality output and increased yield.
• Process reliability: steady-state operation reduces variability and downtime.
• Cost reduction: custom reactors improve residence time versus commercial alternatives at a fraction of the cost.
• Increased sustainability: greater energy efficiency, less waste, and a lower carbon footprint.
• Flexible production: control over volumes with on-demand, continuous supply.

With better heat exchange and the continuous removal of high-energy intermediates, flow chemistry allows complex, exothermic, or hazardous chemistries to happen in a safe and controlled manner and at a larger scale than batch manufacturing permits. Because only a small quantity of material is reacting at any moment, the risk profile of chemistries such as nitrations, diazotizations, hydrogenations, and reactions using toxic gaseous reagents is significantly reduced.

Flow chemistry reduces environmental impact by increasing energy efficiency, reducing waste, and lowering the carbon footprint. Tighter control over reaction conditions minimizes side reactions and off-spec material, while continuous operation avoids the energy and solvent penalties associated with repeated batch heat-up, cool-down, and cleaning cycles.

In many cases, yes but conversion depends on the specific chemistry, reaction kinetics, solids handling, heat-transfer needs, safety profile, and target production scale. Some batch processes can be adapted with relatively limited development work, while others may require route redesign, specialized reactor engineering, or a hybrid flow-plus-batch approach. Curia’s team evaluates each route individually and designs a custom reactor around the chemistry, rather than forcing the chemistry to fit an off-the-shelf reactor.

Curia can design the right reactor for your chemistry and carry it from proof-of-concept through to commercial supply thanks the combination of chemistry and engineering expertise, custom reactor capability, and an integrated network.

Curia designs and builds its own flow reactors to suit each customer’s chemistry. At laboratory scale, the Hyderabad, India site (non-GMP) operates photo reactors, high temperature thermal reactors, jacketed microreactors and a fixed bed hydrogenation reactor. At pilot scale, photo reactors and fixed bed hydrogenation reactors run at Hyderabad (non-GMP) and at Bon-Encontre, France (GMP), where flow processes are scaled to commercial ton quantities.

As examples of scale, Curia’s prototype photo reactors (50 mL to 200 mL, 420 to 480 nm LEDs) and high temperature reactors (60 mL to 500 mL, 120 to 360 °C) have delivered batches from 500 g to 10 kg for customers. Curia’s commercial-scale continuous photo reactor, with a 2 L reactor volume, achieves a throughput of approximately 40 kg per day, around one ton per month, and has been transferred to the Bon-Encontre manufacturing site.

Yes. Continuous flow keeps the reacting volume small and heat and mass transfer efficient, which allows reactions that are hazardous or impractical at batch scale to be run safely and scaled by extending run time rather than vessel size. Curia has demonstrated flow expertise in thermal and cryogenic reactions, photo halogenation, photo oxidation, diazotization, nitration, hydrogenation, preparation of azides, cyanogen bromide-mediated reactions, preparation of organometallic reagents such as Grignard and organozincate reagents, and sp2-sp3 coupling reactions such as Fürstner and Negishi couplings, as well as annular centrifugal reactor processing.

High temperature chemistry is one example: Curia’s custom reactors operate from 120 to 360 °C, and a flow process at 320 °C has delivered 10 kg of product to a customer. Curia’s team continues to validate new reactions in flow and can assess a specific reaction on request.

Flow chemistry at Curia is part of the API development and manufacturing network rather than a standalone service. Reactor design and process development take place at Hyderabad, and the process is transferred to Bon-Encontre, a GMP site within Curia’s European API and fine chemicals operations, for development manufacturing and scale-up to commercial ton quantities.

Curia is also converting existing batch steps to flow within its own routes: a custom fixed bed hydrogenation reactor developed at Hyderabad is being transferred to pilot scale to move batch hydrogenation processes at the French sites to continuous flow.