1499
Ind. Eng. Chem. Res. 1996,34, 1499
CORRESPONDENCE Comments on “Kinetics and Reaction Pathways of Pyridine Oxidation in Supercritical Water” Neil Crain, Saadedine Tebbal, Lixiong Li,and Earnest F. Gloyna* Environmental Health Engineering and Separation Research Programs, Center for Energy Studies, The University of Texas at Austin, Austin, Texas 78758
Sir: During a recent review of our paper (Ind. Eng. C h m .Res. 1993,32,2259-2268), a numerical error was discovered in the reported rate equation for pyridine oxidation. The experimental data (a total of 54 points) for pyridine oxidation, as reported in the abovementioned paper (Table 111,have been reevaluated using a regression program provided by Professor J. W. Tester’s Group at MIT. The regression analysis produced a set of kinetic parameter estimates that are slightly different from those previously reported. This software package, based on a modified Marquardt method for parameter optimization, permitted the analysis of the plug flow design equation without fixing the pyridine reaction order. Also, estimates were obtained for a fmed first-order model with respect t o pyridine. These results are given in Table 1. Finally, it is our experience that the use various numerical algorithms
Table lo ~~
A
E.
a b (kJ/mol) 14.1 f 0.8 229 f 9 0.66f 0.088 0.28 f 0.069 17.2f 0.9 261 f 12 l.Ob 0.30 f 0.095
(M,s)
~
sum of squares of residual z(xpred
- xobs)2
0.285 0.365
a Symbols used in the table are defined as follows: -d[PyrYdt = A exp(-E$RT)[Pyrp[O2]*; Xob(experimentally observed conversion) = 1 - [Pyr],d[Pyr]i,~ Xpred (predicted conversion) = 1 exp{-A exp(-E,lRT)[Oz]o*s} (if a = l), = 1 - (1 - A exp(-E./ RT)(1 - a)[Pyrla-1[02]obt}1’(1-a) (if a f 1). This parameter was fured.
(statistically based software) results in slightly different estimates of these kinetic parameters.
0888-588519512634-1499$09.00/0 0 1995 American Chemical Society
IE9408066
