Effect of Lewis basicity on the continuous gas phase condensation of benzaldehyde with acetophenone over MgO

[Display omitted] •Chalcone production over MgO sensitive to surface Lewis basicity (from CO2-TPD).•MgO Lewis basicity tuned by changes in synthesis method/calcination temperature.•Direct correlation of surface area with Lewis basicity for MgO catalysts proved.•Increase in Lewis basicity of MgO via Li+- and Cs+-incorporation by impregnation.•Efficient gas phase continuous chalcone production over novel Cs-MgO catalyst. We have investigated the effect of Lewis basicity in the continuous gas phase condensation of acetophenone + benzaldehyde over MgO. The catalysts were prepared by ammonia precipitation, hydration and calcination to generate MgO with modified Lewis basicity (from CO2-TPD), dXRD (4−20 nm) and specific surface area (SSA = 58−246 m2 g−1); a direct correlation between SSA and Lewis basicity is presented. The introduction of Li+ and Cs+ served to decrease SSA and increase dXRD and Lewis basicity, linked to diffusion of the cations within the crystal structure (confirmed by XRD/STEM-EDX). All MgO systems delivered the exclusive and time invariant formation of target benzylideneacetophenone. Benzylideneacetophenone production rate is sensitive to the specific (per m2) Lewis basicity. The Cs10MgO_H(773) catalyst delivered the highest rate, attributed to high density of (Lewis basic) -O2− sites involved in the rate-determining step. Our results establish the feasibility of continuous chalcone synthesis using MgO catalysts with controlled Lewis basicity.