Synthesis of paracetamol by liquid phase Beckmann rearrangement of 4-hydroxyacetophenone oxime over H3PO4/Al-MCM-41

Paracetamol was synthesized via the environmentally benign liquid phase Beckmann rearrangement of 4-hydroxyacetophenone oxime over Al-MCM-41 modified with H3PO4. Al-MCM-41 materials were synthesized using different aluminium sources. Aprotic solvents with a high dielectric constant or high polar nature are preferred for this transformation, acetone being the optimal solvent. The conversion of 4-hydroxyacetophenone oxime to paracetamol increased with the H3PO4 content in the catalysts up to a maximum value for a H3PO4 loading of 30 wt% and decreased for higher loadings. Recovery of the catalysts was also investigated.