Investigation of catalytic property in the t-butylation of 1,2-dihydroxybenzene using FT-IR and XPS study

Catalytic properties of HZSM-5s with three different Na⁺ ion-exchange levels and SiO₂ /Al₂O₃ ratios used in tert-butylation of DHB (1,2-dihydroxybenzene) are interpreted through pyridine adsorbed FT-IR and XPS study. The DHB conversion decreases as increment of degree of Na⁺ ion-exchange level and of Si content in HZSM-5. Catalytic properties with respect to Na amount in ZSM-5 are more sensitive than those of HZSM-5s with different SiO₂/Al₂O₃ ratios. But selectivity for 4-TBC (4-t-butylcatechol) is not changed significantly. Acidic properties, i.e. acid strength and acid density are characterized by pyridine adsorbed FT-IR and XPS study. Based on FTIR and XPS analyses, DHB conversion and selectivities for DTBC (3,5-di-t-butylcatechol) and 3-TBC (3-t-butylcatechol) depend on type and strength of acid sites, with the result that strong Brønsted acid rather than weak Brønsted or Lewis acid sites are more closely related to the conversion. Furthermore, t-butyl alcohol is selectively adsorbed on the Brønsted acid site of FT-IR band at 3612 cm^-1, which signifies that the Brønsted acid site is the active site. The mechanism for t-butylation of DHB is suggested based on the FT-IR results of adsorption/desorption of reactants.