A green and efficient solid acid catalyst from coal fly ash for Fischer esterification reaction

•A green and efficient solid acid catalyst (SAC) has been synthesized from coal combustion by-product – fly ash.•SAC exhibited excellent catalytic activity and stability for methyl 4-aminobenzoate (MAB) synthesis.•MAB was synthesized by Fischer esterification reaction between 4-aminobenzoic acid and methanol over SAC.

A green and efficient solid acid catalyst (SAC) has been synthesized upon modification of F-type fly ash using ortho-phosphoric acid (35 wt. %). Catalyst characterization has been accomplished using different analytical techniques, such as FT-IR, XRD, SEM–EDS, and BET surface area analysis. SAC possessed excellent catalytic activity for Fischer esterification reaction between 4-aminobenzoic acid and methanol at 95 °C to produce methyl 4-aminobenzoate (MAB), an important precursor for the synthesis of pharmaceutical drugs, (±) martinelline, and (±) martinellic acid. This investigation suggests the utilization of fly ash to develop novel solid acid catalyst system for catalyzing industrially important esterification reaction.

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