Ultrasonic enhancement of the acidity, surface area and free fatty acids esterification catalytic activity of sulphated ZrO2-TiO2 systems

► Sulphated ZrO2-TiO2 systems with enhanced acidity and surface area were obtained with ultrasound. ► Acoustic cavitation is responsible for the formation of catalytically active surface defects. ► The effect of different ultrasound on/off pulses ratios and powers was investigated. ► Tuning catalysts' properties is possible selecting appropriate on/off pulses ratios and powers.