Fabrication and performance of monolithic continuous-flow silica microreactors

Monolith-in-monolith reactor (MiM) was obtained by embedding monolithic silica with the hierarchical pore structure into the channels of conventional honeycomb monolith made of cordierite. Surface treatment of the cordierite with alkaline and acidic solution was applied to increase its surface area and generate strong silanols, to ensure good adherence between the monoliths. Application of 10 wt% NaOH solution at room temperature for 0.5 h was found to offer the best contact between two materials. Both structure and flow characteristics of the embedded silica proved to be quite similar to those obtained for pure silica rods, considered as reference. Performance of MiM microreactor functionalised with sulphonic groups was shown to be similar to that of a single silica rod microreactor in the esterification of acetic acid with butanol. The elaboration of fabrication procedure for monolithic silica microreactors may open new venue in the engineering of cost-effective production of fine chemicals.