Synthesis and characterization of novel aminopropylated fly ash catalyst and its beneficial application in base catalyzed Knoevenagel condensation reaction

A series of solid base catalysts were synthesized by functionalization of different weight fractions (5, 10, and 15 wt.%) of 3-aminopropyltrimethoxysilane (APTMS) on thermally activated F- type fly ash (SiO2 and Al2O3 > 70%). Catalyst characterization was undertaken using different analytical techniques such as FTIR, XRD, SEM–EDX, TEM, N2− adsorption desorption, BET surface area analysis, TGA and AAS. The results showed that appropriate amount (10 wt.%) of aminopropyl groups results in excellent catalytic performance tested for condensation of ethyl cyanoacetate and cyclohexanone at 120 °C to produce Ethyl (cyclohexylidene) cyanoacetate (92% yield), an important intermediate of gabapentin (Neurontin), widely used in the treatment of epilepsy to relieve neuropathic pain, under solvent free conditions and in low cost route. The catalyst NH2FA-10 was reusable up to three reaction cycles. The work reports an innovative use of solid waste fly ash as an effective solid base catalyst.