Highly effective continuous-flow monolithic silica microreactors for acid catalyzed processes

• Con-flow monolithic silica microreactor with active acidic centers was fabricated.
• Microreactor operates at low pressure drop due to presence of large macropores.
• Reactor shows high activity in esterification of acetic/lactic acid with n-butanol.
• The structural and catalytic stability of the microreactor is demonstrated.

This work reports the performance of a new monolithic silica microreactor, activated with sulphonic acid groups in the continuous-flow synthesis of n-butyl acetate and n-butyl lactate. A reactive core of the reactor was made of a single silica rod with bi-continuous structure, containing flow-through pores with diameter in the range of 20–50 μm and mesopores of ca. 20 nm localized in silica struts. This structure resulted in low pressure drop, even at flow rates large enough to eliminate external mass transfer effect on the reaction kinetics. The microreactor functionalized with 0.65 mmol/g of SO3H groups showed high activity and productivity in both esterification reactions carried out in temperatures up to 140 °C. Structural and catalytic stability of the microreactor was confirmed to demonstrate its process viability.

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