Description
Loop reactors are the preferred continuous reactor format for gas–liquid reactions requiring high gas–liquid mass transfer — particularly hydrogenation, oxidation with air or pure oxygen, carbonylation, and chlorination reactions. The gas is introduced at the loop inlet and dispersed into fine bubbles by the high-velocity liquid stream, achieving volumetric gas–liquid mass transfer coefficients (kLa values) of 0.1–1.0 s⁻¹ — substantially higher than conventional stirred tanks (0.01–0.1 s⁻¹). For three-phase (gas–liquid–solid catalyst) systems, the catalyst particles are maintained in suspension by the high recirculation velocity, eliminating the need for mechanical agitation.
Jet loop reactors use a high-velocity liquid jet nozzle to entrain and disperse the gas phase directly into the liquid stream — without any mechanical moving parts — making them particularly suitable for highly exothermic gas–liquid reactions where seal integrity and mechanical reliability are critical. Temperature control in loop reactors is achieved through an external heat exchanger incorporated into the recirculation loop, allowing precise temperature regulation independent of the reaction vessel geometry. For slurry handling, the loop design ensures particles remain suspended continuously, and slurry discharge is achieved through a controlled overflow or withdrawal point without stopping the recirculation.
Key Features
- Extremely high gas–liquid mass transfer — 10× conventional stirred tank
- External heat exchanger enables precise temperature control
- Well-mixed CSTR behaviour with tubular-flow heat and mass transfer rates
- High recirculation ratio moderates concentration spikes from fresh feed
- Jet loop variants have no moving parts in the reactor loop itself
- Scalable from bench (5 L) to full production (>10,000 L) without design change
- Slurry catalyst suspension without mechanical agitation
- Suitable for continuous hydrogenation, oxidation, and chlorination at scale
Technical Specifications
| Reactor Volume | 5 L to 50,000 L (production scale) |
| Recirculation Ratio | 20:1 to 100:1 (recirculate to fresh feed) |
| Gas–Liquid kLa | 0.1–1.0 s⁻¹ (jet loop and high-velocity designs) |
| Materials of Construction | SS 316L, Hastelloy C-276, Glass-lined, Ti Gr.2 |
| Reaction Types | Gas–liquid, liquid–liquid, gas–liquid–solid (slurry catalyst) |
| Recirculation Drive | Centrifugal pump, axial pump, or jet ejector (no moving parts) |
| Heat Exchange | External shell-and-tube or plate HX in recirculation loop |
| Pressure Rating | Up to 100 bar (hydrogen service designs) |
| Temperature Range | −20°C to +300°C |
| Residence Time Control | Withdrawal rate controls product RTD independently of recirculation |
Industrial Applications
- Continuous catalytic hydrogenation with H₂ under pressure
- Aerobic oxidation with air or enriched O₂ (e.g., toluene oxidation)
- Chlorination reactions with Cl₂ gas in organic media
- Fermentation and enzymatic bioprocesses in continuous mode
- HCl absorption into organic solvents for hydrochlorination
- Carbonylation and CO-gas reactions under moderate pressure
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