Silicotungstate-modified zirconia as an efficient catalyst for phenol tert-butylation

Abstract

The alkylation of phenol with tert-butanol was investigated using zirconia modified with silicotungstic acid (STA) as catalysts. The catalysts with different STA loading (5–25 wt.% calcined at 750 °C) and calcination temperature (15 wt.% calcined from 350 to 850 °C) were prepared and characterized by X-ray diffraction and NH 3-TPD measurements. The XRD results indicate that STA stabilizes the tetragonal phase of zirconia. The catalyst with 15% STA on ZrO 2 calcined at 750 °C shows the highest acidity and hence highest activity. Under the reaction conditions of 140 °C, tert-butanol/phenol molar ratio of 2 and LHSV of 4 h −1, phenol conversion was 95.4% with selectivity to 2- tert-butyl phenol 4.3%, 4- tert-butyl phenol 59.2% and 2,4-di- tert-butyl phenol 35.8%. The reaction was studied as a function of time for 50 h without appreciable change in phenol conversion and product selectivity. The deactivated catalyst could be regenerated by calcination with out appreciable lose in catalytic activity and product selectivity.