Page 257 - Elements of Chemical Reaction Engineering 3rd Edition

Sec. 5.1 Batch Reactor Data 229
Example 5-1 Differential Method of Analysis of Pressure-Time Data

Determine the reaction order for the gas-phase decomposition of di-tert-butyl perioxide,

0
II
(CH,),COOC(CH,), 3 CZH, + 2CH3 C CH3

This reaction was carried out in the laboratory in an isothermal batch system
in which the total pressure was recorded at various times during the reaction? The
data given in Table E5-1.1 apply to this reaction. Only pure di-ten-butyl peroxide
wars initially present in the reaction vessel.

--
TABLE E5-1.1 mcEssm-Tm? DATA
Time (min) Torul Pressure (dg)

0.0 7.5
2.5 10.5
5.0 12.5
10.0 15.8
15.0 17.9
20.0 19.4

While the proper SI units of pressure are pascal (Pa) or kilopascal (Ha), a
significant Fount of kinetic data in past literature are reported in units of mmHg _,
(tom), atmospheres, or psi. Consequently, we must be able to analyze pressure-time
rate data in any one of these units.

1 atm = 14.7 psi 5 1.013 bar E 101.3 kPa = 760 mmHg

Solution

Let .A represent di-tert-butyl peroxide.
1. Postulate a rate law.

A Combination of the mole balance on a constant-volum batch reactor and the rate
law gives

(E5-1.1)

where CL and k are to be determined from the data listed in Table E5-1.1.

* A. E hxman-Dickenson, J. Chem Educ., 46, 396 (1969).