Dry raw RH was sieved to eliminate residual rice and clay particles.
After thorough washing with deionized water, the RH was filtered and air-dried at 105 °C until constant weight.
And then, the RH was calcined at different temperatures (400 °C, 600 °C and 800 °C) for 4 h to prepare RHA.
These ashes were used as support for the active catalyst and referred to as RHA400, RHA600 and RHA800 herein after.