Jordanian natural kaolin and bentonite show good catalytic activity towards debutylating 2-tert-butylphenol, and varying debutylation vs. isomerization selectivity after acid activation. The resulting catalytic activity of these samples is dependent on the acid employed for activation; the samples treated with acetic acid showed relatively low conversions, whereas those treated with hydrochloric or phosphoric acid were found to be very active. Treatments with strong acids such as HCl have various effects on the activity of the samples depending on the concentration of the acid. For example, treatment with 1 M HCl gives the highest activity, whereas a treatment using 12 M HCl produced the lowest activity. The debutylation selectivity of the acid-activated samples is affected by the acid type and/or concentration. This selectivity ranges from 20 to 60%, whereas that of water-treated samples is between 46–82%.

De-tert-butylation of 2-tert-butylphenol was carried out over thermally-treated and acid-treated Jordanian bentonite clay samples. This reaction was found to follow first-order kinetics for all clay samples with different pretreatment procedures. The apparent rate constant, k, was also determined, and found to depend on the pretreatment. Thermal pretreatment at temperatures up to 250°C has an enhancing effect on surface acid sites. The total surface acidity (Ho <4.8) and the concentration of strong acid sites peaked at 250°C. Also, as a result, the maximum catalyst activity was obtained with samples treated at this temperature. Acid pretreatment with 0.10 M HCl, 1.0 M H2SO4 or 1.0 M H3PO4, followed by thermal treatment at 250°C produced the best enhancement effect on the surface acidity and catalytic activity.