MgO Enriched Coal Fly Ash as Highly Active Heterogeneous Base Catalyst for Claisen-Schmidt Condensation Reaction

A novel fly ash supported solid base catalyst (MgO/fly ash) has been synthesized by using F-type fly ash and Mg(NO3)2 as precursor. The synthesized solid base possessed stable Si-O-Mg phase with sufficient hydroxyl group to catalyze liquid phase, solvent free and single step condensation of 4-methoxybenzaldehyde with 2-hydroxyacetophenone giving higher conversion (86%) of desired product (4-methoxy-2-hydroxychalcone) with 93% yield. The physio-chemical properties of MgO/fly ash catalyst were evaluated by N2 adsorption-desorption, BET surface analysis, XRD, FT-IR, SEM-EDX and AAS etc. This excellent conversion and yield shows that the catalyst has sufficient basic sites, responsible for the catalytic activity. Moreover, the catalyst was regenerated and reused up to four reaction cycles with approximately equal efficiency as in the first run, conferring that basic sites are not lixiviated in the reaction system. Furthermore, this catalyst may replace conventional environmentally hazardous homogeneous liquid bases making an ecofriendly; solvent free, atom efficient, solid base catalytic process. The application of fly ash to synthesize a solid base catalyst finds a noble way to utilize this abundant waste material.