Optimization of biological-hydroxyapatite supported iron catalyzed methyl oleate synthesis using response surface methodology

• Novel iron acid catalyst supported on biological-hydroxyapatite derived from fish (Catla catla) bone.
• Catalyst preparation using infrared (IR) irradiation-assisted freeze-drying.
• Parametric effects on oleic acid conversion in esterification with methanol.
• Optimization of methyl oleate synthesis using response surface method (RSM).
• Augmented oleic acid conversion through water abstraction by recyclable desiccant.

Innovative biological-hydroxyapatite (BHAp) derived from Catla catla (abundantly aqua-cultured freshwater species in South Asia) bone was employed to prepare cost-effective, reusable supported iron solid acid catalyst using Fe2 (SO4)3·H2O through wet impregnation method employing infrared (IR) irradiation assisted freeze-drying protocol. The catalytic effectiveness was assessed and optimized through response surface methodology (RSM) in synthesis of methyl oleate through esterification of oleic acid with methanol. Catalyst characterization involved TGA, FESEM, EDX, XRD, BET–BJH and FTIR analyses. The catalyst that rendered optimal performance possessed 14.9 m2/g specific surface area, 0.0335 cm3/g pore volume and 33.13 nm modal pore size with an acidity of 10.336 mmol KOH/g catalyst. Esterification attained a maximum 93.0% conversion at 70 °C freeze-drying temperature, 1.85 weight ratio of ferric sulphate to BHAp and 2.0 wt.% catalyst concentration within 60 min batch time. Application of recyclable solid desiccant during esterification could further significantly augment methyl oleate yield at the derived optimal conditions. The novel catalyst exhibited appreciable reusability and rejuvenation attributes. The present research demonstrates successful application of C. catla bone as a potential support for economical preparation of solid iron acid catalyst, creating an innovative avenue for recycling of this municipal solid waste.