Optimisation on pretreatment of rubber seed (Hevea brasiliensis) oil via esterification reaction in a hydrodynamic cavitation reactor

•HC reactor for pretreatment of RSO at pilot scale with 50L capacity.•New designed four orifice plates studied at inlet pressure (1–3.5bar).•Pre and post optimised conditions found for orifice plate and reaction parameters.•HC found to be 3-fold shorter time compared to MS.•HC have 4-fold higher esterified efficiency than MS. Pretreatment of the high free fatty acid rubber seed oil (RSO) via esterification reaction has been investigated by using a pilot scale hydrodynamic cavitation (HC) reactor. Four newly designed orifice plate geometries are studied. Cavities are induced by assisted double diaphragm pump in the range of 1–3.5bar inlet pressure. An optimised plate with 21 holes of 1mm diameter and inlet pressure of 3bar resulted in RSO acid value reduction from 72.36 to 2.64mgKOH/g within 30min of reaction time. Reaction parameters have been optimised by using response surface methodology and found as methanol to oil ratio of 6:1, catalyst concentration of 8wt%, reaction time of 30min and reaction temperature of 55°C. The reaction time and esterified efficiency of HC was three fold shorter and four fold higher than mechanical stirring. This makes the HC process more environmental friendly.