Alumina-grafted macro-/mesoporous silica monoliths as continuous flow microreactors for the Diels–Alder reaction

Bimodal macro-/mesoporous silica monoliths (6 mm diameter, 1–4 cm length) were functionalized with aluminum oxide allowing the preparation of a new solid Lewis acid catalyst named Al-MonoSil. Al-MonoSil was used as catalytic microreactor for the in-flow implementation of the Diels–Alder reaction. Due to the interconnected and homogeneous system of macropores of 5 μm within the monolith, the Al-MonoSil shows high conversion and productivity in continuous flow without pressure drop. The external mass transfer limitations and the productivity were controlled by adjusting monolith length and flow rate. Al-MonoSil is a stable microreactor for long time productivity for Lewis acid–catalyzed reactions.

Aluminum oxide–grafted silica monoliths were proved as highly productive catalytic microreactors for the in-flow implementation of the Diels–Alder reaction. Control of contact time and monolithic length has allowed to overcome external diffusion limitations.Figure optionsDownload high-quality image (121 K)Download as PowerPoint slideHighlights
► Design of new macro-/mesoporous monolith (Al-MonoSil) by Al2O3 grafting on silica monolith.
► Al-MonoSil microreactor shows high productivity for Diels–Alder reaction in flow.
► External diffusion limitations were overcome by adjusting flow rate and monolith length.
► Al-MonoSil is a stable microreactor for long-term production (>7 days).
► Al-MonoSil is a suitable catalyst for reactions requiring moderate Lewis acidity.