For a flow reactor

Reactor Performance Measures. There are four common measures of reactor performance fraction unreacted, conversion, yield, and selectivity. The fraction unreacted is the simplest and is usually found directly when solving the component balance equations. It is a t)/oo for a batch reaction and aout/ciin for a flow reactor. The conversion is just 1 minus the fraction unreacted. The terms conversion and fraction unreacted refer to a specific reactant. It is usually the stoichiometrically limiting reactant. See Equation (1.26) for the first-order case. 

A reasonably general energy balance for a flow reactor can be written in English as... 

Second, for a flow reactor, such as a CSTR, the mean residence time and space time are equal, since q = q0 ... 

Specific conversion rates are calculated in the usual way for a flow reactor k = (F/S) ln[(Ceq - C0)/(Ce<, - Cx)], where F is the flow rate (mol s 1), S the total catalyst surface (m2), C, the ortho-para equilibrium ratio at the reactor temperature, C0 the ratio for hydrogen entering the reactor and Cx the ratio for hydrogen leaving the reactor. For different samples of the same catalyst the zero field conversion reproducibility is seldom better than by a factor of 5, but the fractional change AkH = (kH - k0)/ko may often be reproduced to 5%. In some cases a change of 0.5% is measurable. (kH is the specific rate in a field H, k0 that in zero or negligible field). 

It is useful to have a measure of time for a flow reactor even though the major design variable is reactor or fluid volume. A commonly used quantity in industrial reactor design is space time. Space time is defined as the time required to process one reactor volume of feed, measured at some set of specified conditions. The normal conditions chosen are the inlet concentration of a reactant and inlet molar or volumetric flow rate. 

The sum of inlet molecular flow rates per site for a flow reactor, (FT), is equal to the reciprocal of the site time, l/rp, which may be defined as the overall inlet site velocity, //. ... 

On the other hand, for a flow reactor where concentration varies throughout the reactor, it is usually more convenient to base the rate on a differential volume of the reactor, and a commonly used rate form is... 

Express Pi and C for ail species as funcdons of conversion for a flow reactor. 

In Section 6.1 we saw. that the undesired product could be minimized by adjusting the reaction conditions (e.g., concentration) and by choosing the proper reactor. For series of consecutive reactions, the most important variable is time space-time for a flow reactor and real-timE for a batch reactor. To illustrate the importance of the time factor, we consider the sequence... 

Hint Remember that the equilibriimi conversion will be different for a flow reactor and a constant-volumebatch reactor for a gas-phase reaction that has a change in the total number of moles.)... 

With two electrocatalytic steps in series, the concentration of the intermediate B (Eq. 70) goes through a maximum with time (or space-time for a flow reactor). Solution of the kinetic equations for each species (60) yields for the simple case of first-order reactions... 

To design a chemical reactor, the spatial-average concentrations a,b,c,. .. must be found for a batch reactor and the outlet concentrations are needed for a flow reactor. Finding these concentrations is relatively easy for the single, elementary reactions and ideal reactors that are considered here in Chapter 1. We begin by discussing elementary reactions, of which there are just a few basic types. 

The residence-time distribution is tabulated below for a flow reactor that has a feed rate of 16.2 ft /rnin. Under the feed conditions (ca/ = 0.02 Ibmol/ft and CBf = 2.34 Ibmol/ft ) the reaction... 

There are many opportunities for technicians who benefit from grounding in the sciences. An associate s degree in science or applied science, or in an engineering field, is a very good basis for a flow reactor technician s career path. 

Scheme 7.27 illustrates the substrate scope after optimisation of the reaction conditions. This is a particularly facile reaction to implement as it utilizes a cheap copper catalyst and a commercially available oxidant, TBHP. The authors compared continuous flow with batch protocols and found good correlations, thus allowing such reactions to be carried out without the specific need for a flow-reactor (Scheme 7.28). 

Write the combined rate law and mole balance solely in terms of conversion and rate law parameter for a batch reactor and for a flow reactor. 

In most systems, the entering microorganism concentration, is zero for a flow reactor. 

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