The absence of wall effects during benzonitrile hydrolysis

The kinetics of benzonitrile hydrolysis were used to probe the effect of re actor walls on hydrothermal reaction chemistry. The three key issues of: (1 ) reactor use history; (2) material of construction; and (3) surface area t o volume ratio (S/V) were investigated with respect to reaction rate consta nt and hydrolysis product yield. A series of identical reactions revealed n o effect of repeated reactor use on either the rate constant or product sel ectivity.. Likewise, use of stainless steel and titanium reactors with the same volume and surface area produced no statistical difference in either r ate constant or product yield. Finally, the kinetics and product yields wer e not affected by variation of reactor S/V from 3.68 to 14.84 cm(-1). Analy sis of possible parallel homogeneous and heterogeneous (wall) reaction at 3 00 degrees C and 200 bar revealed rate constants of 1.02 x 10(-2) min(-1) a nd 1.22 x 10(-4) cm min(-1), respectively. The maximum heterogeneous contri bution to the overall rate (5.6 +/- 2.0%) was within the experimental uncer tainty for the homogeneous rate constant (6.1%). This suggests that the lab oratory-deduced rate constants will provide a faithful model for the true k inetics at commercial conditions. (C) 1999 Elsevier Science B.V. All rights reserved.