Page 251 - Elements of Chemical Reaction Engineering 3rd Edition

Collection and Analysis 5

of Rate Data

You can observe a lot just by watching.
Yogi Berra, New York Yankees

In Chapter 4 we showed that once the rate law is known, it can be substituted
into the appropriate design equation, and through the use of the appropriate
stoichiometric relationships we can size any isothermal reaction system. In this
chapter we focus on ways of obtaining and analyzing reaction rate data to
obtain the rate law for a specific reaction. In particular, we discuss two com-
mon types of reactors for obtaining rate data: the batch reactor, which is used
primarily for homogeneous reactions, and the differential reactor, which is
used for solid-fluid reactions. In batch reactor experiments, concentration,
pressuire, andor volume are usually measured and recorded at different times
during the course of the reaction. Data are collected from the batch reactor
during unsteady-state operation, whereas measurements on the differentid
reactor are made during steady-state operation. In experiments with a differen-
tial reactor, the product concentration is usually monitored for different feed
conditions.
Two techniques of data acquisition are presented: concentration-time
measurements in a batch reactor and concentration measurements in a differen-
tial reactor. Six different methods of analyzing the data collected are used the
differential method, the integral method, the method of half-lives, method of
initial rates, and linear and nonlinear regression (least-squares analysis). The
differential and integral methods are used primarily in analyzing batch reactor
data. Blecause a number of software packages (e.g., POLYMATH, MATLAB)
are now available to analyze data, a rather extensive discussion of linear and
nonlinear regression is included. We close the chapter with a discussion of.
experimental planning and of laboratory reactors (CD-ROM).