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C3–6 diols can be isolated from ethylene glycol (EG) via acid-catalyzed dehydration reactions, but the cost of catalyst and undesirable EG conversion have been concerns. Sulfonated silica gel with mesopores (5–12 nm) was prepared by impregnation and oxidation at a low cost, and it was more active than commercial Hβ zeolite in the catalytic transformation of C3–6 diols. The heat resistance of this material was much higher than Nafion and Amberlyst resins. With the adding of water, the undesirable acetalization reaction of EG was inhibited. The tuning effect of water on the conversions of diols was studied from the perspective of chemical equilibrium. XPS confirmed the existence of SO3H and a small quantity of SO2H groups on the catalyst, and the latter are responsible for the formation of undesirable acetals. This catalyst could be reused thrice with high conversions of C4–6 diols. Glycerol and other non-diol components weakened the reusability of catalyst. After reuse, the deposition of coke and leaching of acidic groups were verified by titration, NH3-TPD, and elemental analysis results. The catalyst could be incompletely regenerated via the removal of coke with H2O2. The solute in leachate was determined by 1H NMR and FTIR, and the cleavage of Si–C bond occurred during the leaching process. This leaching phenomenon was negligible at ≤ 90 °C. This cheap, strong Brønsted solid acid may find its applications in the catalysis field. [ABSTRACT FROM AUTHOR]

For the controllable transformation of C3–6 diols in ethylene glycol (EG), a H-Beta zeolite catalyst was modified with NH3via incomplete desorption. 60.8% of acid sites on the zeolite were deactivated, but the ratio of strong acid sites was obviously increased. With 1,2-pentanediol (PDO) as a representative large-carbon-number diol, the undesirable acetalization and oligomerization reactions of EG were suppressed in the EG-PDO reaction system over the modified catalyst due to their dependency on total acid sites. NH3-TPD and FTIR results proved that Lewis acid sites on the modified zeolite were eliminated after modification, resulting in the suppression of acetalization and oligomerization reactions. In contrast, a portion of strong Brønsted acid sites still remained, ensuring the catalytic transformation of PDO. Only 8.2% of EG was consumed after 8 h reaction, and the conversion of PDO could reach 84.3%. The loading of NH3 on the surface of zeolite pores led to diffusion resistance, slightly decreasing the reaction rate of PDO without affecting the reaction selectivity. The catalytic reactions of other C3–6 diols in EG followed similar principles, and the selectivity to aldehydes or ketone was improved over this modified catalyst. Non-diol biomass hydrogenation products such as glycerol had a negative influence on the selectivity, so these components should be isolated before the reactions. This catalyst could be reused at least 5 times, and the conversion of PDO slightly decreased. This work sheds light on the relationships between the acid properties of the catalyst and different reactions of diols. [ABSTRACT FROM AUTHOR]