The kinetics of the homogeneous benzylation of potato starch in aqueous solutions

The reaction rates in the base-catalysed benzylation of gelatinized aqueous starch (4 wt%), by benzylchloride (BzCl), were investigated in a semibatch reactor at temperatures ranging from 50 to 80 °C. The desired starch benzylation reaction is accompanied by an undesired parallel base-catalysed hydrolysis reaction of benzylchloride. The rate equations are:Starch benzylation: −RBzCl=k2cRO−cBzClBenzylchloride hydrolysis: −RBzCl=k3cOH−cBzClNeutral benzylcholoride hydrolysis: −RBzCl=k4cH2OcBzClwhere cBzCl is the benzylchloride concentration, cRO− is the concentration of the dissociated starch hydroxyl group and cOH− is the sodium hydroxide concentration; k is the reaction rate constant. The temperature dependency of the rate constants was measured as:k2=4.21×1011 e(−86.2×103/RT)k3=2.62×108 e(−85.5×103/RT)k4=9.72×109 e(−76.9×103/RT)where R=8.31441 J/(mol K).