Abstract The facile two-step preparation procedure of a novel magnetic nano-solid acid catalyst is described, which includes grafting an ionic liquid onto Fe 3 O 4 nanoparticles, followed by the sulfonation of phenyl groups in the ionic liquid. The catalytic performance of this novel material has been systematically studied in the acetal formation of benzaldehyde and ethylene glycol. The experimental results testify this catalyst possesses high catalytic ...