A commercial beta zeolite was modified with dilute oxalic acid solutions, and evaluated in the catalytic dehydration of 2-(4'-ethylbenzoyl) benzoic acid (BEA) to produce 2-ethylanthraquinone (2-EAQ). The modified zeolite samples were characterized by X-ray diffraction, Ar-phys-isorption, X-ray fluorescence spectroscopy, Fourier transform infrared spectroscopy, Al-27 MAS NMR and ammonia temperature-programmed desorption. The results show that the modified samples maintain the BEA topology and microporous textural properties. However, dealumination, caused by the modification, leads to dramatic variations in acid properties, including the amount of acid sites, ratio of strong to weak acid sites, and the ratio of Bronsted to Lewis acid sites. The variations in acidity enhance the catalytic performance of BEA dehydration to produce 2-EAQ. The catalytic selectivity was tripled, and the activity increased significantly.