The qualitative correlation between activation energy and acid strength: the influence of crystal structure regulation on the acidity of H 2 SO 4 /ZrO 2 -WO 3 in low-temperature dealkylation

ZrOCl ₂ ·8H ₂ O, (NH ₄ ) ₆ H ₂ W ₁₂ O ₄₀ ·XH ₂ O and aqueous ammonia were used as raw materials to prepare solid oxide supports with varying tungsten contents (ZrO ₂ -WO ₃ ) via the co-precipitation method. A series of solid acid catalysts were subsequently prepared by impregnating these supports with sulfuric acid solutions of different concentrations. The effects of crystal structure regulation on the acid properties of these catalysts on tunning the reaction performance of 2,6-di-tert-butyl-4-methylphenol (BHT) dealkylation to produce p -cresol were first investigated. The primary role of tungsten oxide may be to stabilize the monoclinic phase of ZrO ₂ and to facilitate the formation of more and stronger Brønsted acid sites. The sample with a WO ₃ mass fraction of 14% prepared using a 0.1 mol/L sulfuric acid solution (0.1-H ₂ SO ₄ /ZrO ₂ -WO ₃ -14) exhibits the highest specific surface area (57.27 m ² ·g ^− 1 ), a suitable pore size structure (average pore size of 13.69 nm), the highest content of strong Brønsted acid. As a result, it achieves the highest conversion of BHT (greater than 99.9%) and selectivity for p -cresol (95.0%) under mild reaction condition at 180°C, significantly lower than the catalytic reaction temperatures of zeolites such as H-ZSM-5 (250–350°C). This is attributed to its stronger Brønsted acidity compared to H-ZSM-5, decreasing the energy barrier of dealkylation to enable high catalytic performance at lower temperature, which needs higher temperature on weaker acid, according to the Arrhenius equation (\(\:\text{k}=\text{A}{e}^{\frac{{-E}_{a}}{RT}}\)). Furthermore, after five cycles of reaction, the catalytic performance of 0.1-H ₂ SO ₄ /ZrO ₂ -WO ₃ -14 decreased somewhat, but it was essentially restored after re-calcination. These studies will contribute to the understanding and guidance of the design of strong solid acid for low-temperature catalytic reactions and the further in-depth exploration of the laws of solid acid-catalyzed reactions under mild conditions.