Potassium modified La-Mg mixed oxide as active and selective catalyst for mono-methylation of phenylacetonitrile with dimethyl carbonate

Abstract

Mono-methylated products of phenyl acetonitrile (PAN) are in demand for the preparation of non-steroidal anti-inflammatory drugs (NSAID) such as Ketoprofen, Ibuprofen and Naproxen. 2-Phenylpropionitrile is prepared from PAN and finds uses in pharmaceutical industry. Herein, we report a novel catalyst potassium promoted lanthanum-magnesium oxide as well as a novel reaction using it. It is used for the first time for the selective mono-methylation of phenylacetonitrile to 2-phenylpropionitrile with dimethyl carbonate as a methylating agent. A variety of catalysts were synthesized, characterized such as MgO, La₂O₃, La₂O₃-MgO and potassium (1–4 wt%) on La₂O₃-MgO and used in mono-methylation of phenylacetonitrile with dimethyl carbonate (DMC). Two wt% K/La₂O₃-MgO catalyst was the best and showed 100% conversion of phenylacetonitrile and 100% selectivity of 2-phenyl propionitrile at mole ratio of PAN: DMC of 1:30 at 150 °C in 2 h. The characterization of fresh and used 2 wt% K/La₂O₃-MgO was done using different techniques such as FTIR, SEM, TGA-DSC, CO₂-TPD, XRD, and BET surface area analysis. Two wt% K/La₂O₃-MgO catalyst was used to study the reaction mechanism and a kinetic model developed using LHHW type of mechanism with all species being weakly adsorbed. The apparent activation for mono-methylation of phenylacetonitrile to 2-phenylpropionitrile was found to be 13.77 kcal/mol.