It is well known that, in the high temperature region, the diffusional resistances within the boundary film and that within the pores of catalyst pellet have an important effect on the overall effective reaction rate. In reactor design, it is essential to analyze the experimental data and to distinguish the effect of diffusion from the chemical reaction rate so as to predict the over-all effective reaction rate for the given industrial conditions.
Previously, Kubota and Shindo⁵⁾ presented a method for calculating effectiveness factor of the porous catalyst, which is applicable to any reaction but which involves considerable complicated computations.
In this paper, the authors present a new method for calculating effectiveness factor, based on the approximation of reaction rate to a kind of first-order reaction as expressed by Eq. (6) or (7). When this method was applied to ammonia synthesis, whose rate was expressed by Eq. (13) and which was far from the first-order reaction, the value of Ef' obtained was found to be a very good approximation to the value of Ef obtained by the previous method (Fig. 2).
Other proposals the authors make in this paper are (i) a general analytical procedure for predicting the effective reaction rate by taking into account the diffusional resistances within the boundary film and that within pores of catalyst pellet, and (ii) two other methods for estimating the chemical reaction rate from the experimental data, by taking into account the above-mentioned diffusional resistances. Of these two methods, the first one is applicable when v_eA (pAG) can be obtained from the reaction, viz. when the reaction is carried on in a differential reactor, and the second one is applicable when v_eA (pAG) cannot be obtained directly from the experiment, viz., when the reaction is carried on in an integral reactor. When the latter was applied to the ammonia synthesis data, obtained by one of the authors⁴⁾, great difference was found in the range of above 475°C or so, between the apparent values of reaction rate constant and their corrected values given according to this procedure.

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Experimental rate equations for reactor design have been studied. Rates of the reactions were measured over a range of concentration of cyclopentadiene, 0.2-0.4 mole%, reaction temperature, 380-435°C, flow rate of gas, 1-2m³/hr, and volume of V₂O₅MoO₃ catalyst, 10-30cc, by means of the reactor shown in Fig. 1.
Experimental results can be expressed by the equations (2), (3) and (4).
From the experimental results, it is concluded that cyclopentadiene is oxidized by two simultaneous reactions taking place at the temperatures between 380 and 435°C, the first one giving maleic anhydride and the second one causing complete combustion, the ratio k₁/k₂ depending only on the reaction temperatures.
Calculated and observed mole fractions of the cyclopentadiene used as against 2/N are plotted in Figs. 9 and 10.
The longitudinal temperature profile of the catalyst bed in the tubular reactor as calculated by means of the rate equations and the heat balance equation agrees well with the observed one as shown in Fig. 11.
A three-stage adiabatic converter with intercooler between catalyst beds is designed by applying the rate equations. The influence of the catalyst-bed length on the calculated reaction temperature and yield of maleic anhydride is shown in Fig. 12.

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Catalytic synthesis of acetonitrile was carried out successfully with fluidized-bed reactors of 1.5-, 3-and 8-inch diameters, respectively.
The main results obtained were as follows:
I) Results with 1.5-inch reactor:
1) The reaction rate was expressed as the first order for acetylene and zero order for hydrogen and ammonia.
2) The experimental data were in good agreement with those on a model of piston flow as in the case of the fixed bed.
3) The rate of the reaction was much smaller than that in the case of the fixed bed, and varied with the height of catalyst bed.
4) The experimental formula of rate constant was given by:
k_p=2.19×10⁵(L)^-0.54exp.(-E/RT)
II) The results with 3-and 8-inch reactors were as follows:
1) The results with 3-inch reactor as well as with 8-inch reactor proved to be almost similar to those with 1.5-inch reactor, when the rate of gas flow was kept low.
2) As the size of the reactor became larger and the rate of gas flow higher, the conversion of acetylene increased.

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