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 level s and SiO2/Al2O3 ratios used in tert-butylation of DHB (1,2-dihydroxybenzen e) are interpreted through pyridine adsorbed FT-IR and XPS study. The DHB c onversion decreases as increment of degree of Na+ ion-exchange level and of Si content in HZSM-5. Catalytic proper-ties with respect to Na amount in Z SM-5 are more sensitive than those of HZSM-5s with different SiO2/Al2O3 rat ios. But selectivity for 4-TBC (4-t-butylcatechol) is not changed significa ntly. Acidic properties, i.e. acid strength and acid density are characteri zed by pyridine adsorbed FT-IR and XPS study. Based on FTIR and XPS analyse s. 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 th e result that strong Bronsted acid rather than weak Bronsted or Lewis acid sites are more closely related to the conversion. Furthermore, t-butyl alco hol is selectively adsorbed on the Bronsted acid site of FT-IR band at 3612 cm(-1), which signifies that the Bronsted acid site is the active site. Th e mechanism for t-butylation of DHB is suggested based on the FT-IR results of adsorption/desorption of reactants.