<p>It is crucial to enlarge the pore size of spherical alumina while maintaining its high mechanical strength. In this work, acrylamide, maleimide and phenol were introduced as cross-linker into Al sol to prepare spherical alumina supports by the oil-drop method. By conducting crosslinking polymerization reactions using these cross-linkers with formaldehyde, the consumption of formaldehyde reduces its evaporation and thereby minimizes the disruption to the pore structure of the spherical alumina prepared by the oil-drop method. As a result, the pore structure of the spherical alumina is optimized from wedge-shaped pores to interconnected pores, with the proportion of pores in the range of 25–40&#xa0;nm increasing by ~ 10% while maintaining strength exceed 60&#xa0;N/P. This pore structure optimization effectively alleviates the reduction in catalytic activity caused by mass transfer limitations, the H₂O₂ productivity of the Pd/Al₂O₃-PH-3% (3% phenol as cross-linker) catalyst increased by 9.3% compared to that of Pd/Al₂O₃ without cross-linker.</p> Graphical Abstract <p></p>