In continuous-flow photochemical synthesis, traditional batch reactors often face challenges such as randomly distributed bubbles, difficulty in quantifying gas–liquid contact area, and low reaction rates caused by light attenuation (limitations of the Beer–Lambert law). This “black box” condition hinders precise process development and linear scale-up. The Pofeilai gas–liquid segmented-flow micro photoreactor introduces an ordered “segmented flow (Slug Flow)” structure, converting macroscopic reactions into precisely controllable “micro-unit reactors”, achieving a leap from chaotic flow to precision chemical control.
In transparent photochemical reaction tubing, the ideal condition is to exhibit a clear and orderly flow structure: liquid slugs (liquid segments) and gas bubbles occupying the full tube diameter alternating periodically.
This is the core characteristic of gas–liquid segmented flow. This flow type is not only visually ordered but also represents a refined change in reaction mode: essentially, it converts traditional imprecise macroscopic reactions into precisely controllable “micro-unit reactions”.
This flow design solves challenges that traditional batch and all-liquid reactors cannot reconcile in chemical engineering, showing outstanding performance especially in mass-transfer kinetics and optical utilization:
Extremely narrow residence time distribution (RTD): Gas bubbles segment the liquid into independent slug units, approaching ideal plug flow behavior, ensuring that all molecules experience an identical “illumination history”, significantly improving product selectivity.
Excellent mass-transfer efficiency: Alternating gas–liquid arrangement creates a very large contact interface; combined with strong internal recirculating vortices within the liquid slugs, the mass-transfer coefficient (k_La) is increased by 1–2 orders of magnitude compared with traditional methods.
True “photon uniformity”: Each liquid-slug micro-unit receives uniform illumination due to rapid mixing; the micrometer-thin liquid film between the bubble and the tube wall effectively overcomes light-shielding effects in high-concentration or deeply colored systems.
Inherent safety and enhanced performance: The small-diameter tubing design is intrinsically pressure-resistant, reducing the inventory of hazardous gases while significantly increasing gas equilibrium solubility under high pressure (Henry's law), directly raising the upper limit of reaction rates.
Gas–liquid photosensitized oxidation reactions: For example, reactions involving singlet oxygen. Ensures continuous oxygen-saturated supply, solves mass-transfer bottlenecks, and avoids gas waste.
Reactions involving hazardous gases: Such as photochemical chlorination or photo-hydrogenation using chlorine, hydrogen, or carbon monoxide. Enables safe operation with extremely low liquid hold-up while ensuring continuous and stable radical-chain reactions.
High-concentration / deeply colored systems: For systems limited by light penetration depth, thin liquid films and strong internal turbulence are used to achieve efficient photoconversion.
Precision kinetics studies: Flexibly adjust the gas–liquid flow rate ratio and freely define liquid-slug length and bubble frequency, providing researchers with a highly tunable and highly reproducible experimental platform.
This device is not only a flow-pattern generator but also a flexible process-development platform that supports engineering breakthroughs:
Customized flow-field definition: Supports free adjustment of gas–liquid flow rate ratios; users can precisely change liquid-slug length and bubble frequency based on reaction kinetic constants to find optimal reaction conditions.
Precise control and high stability: Capable of finely tuning the microscopic flow field, effectively preventing flow-regime degradation (e.g., stratified flow or jetting), and ensuring data reproducibility during long-term operation.
Process scale-up support: Provides reliable kinetic data and fluid-model support for scaling from laboratory research to industrial production.
