The RTD does not fully specify the fluid dynamics: different devices could have different internal flows and yet lead to the same RTD. Therefore you will have to make additional assumptions on how to leverage the RTD information to build a good reactor model. There are different ways it can be done.

Firstly, upper and lower boundaries for concentrations at the outlet can be estimated assuming either complete mixing or no mixing between volume elements (so-called "maximum mixedness" and "segregation" models), and that would specify the way to combine the measured RTD with the mass balance equation.

Secondly, you could model your real reactor as a combination of ideal reactors. You may want to specify the combination and its parameters to obtain good agreement with the measured RTD (and chemical production results). The book "Elements of Chemical Reaction Engineering" by Fogler has examples for these two approaches.

A third approach would be to use computational fluid dynamics (CFD): the RTD could help you specify some of the boundary conditions and assumptions in your CFD model. Then you could bring the kinetics information into your CFD model and validate it against real production data.

As a first go in a real problem, I would determine the chemical rate expressions using an "ideal" reactor, determine the real reactor RTD using inert tracer experiments, and then try to model the real reactor RTD and performance as a combination of a couple of ideal flow reactors.

Having a verified mass balance equation, based on the assumed reagent flow model and with a precise kinetic equation (rate law), you can determine the conversion and E(t). With only E(t) you cannot compute a conversion.

Hi Mirosław Grzesik , I have the kinetic equation for my system as well as E(t). I am unable to incorporate the E(t) into the standard mass balance equation

{D*d2 C/dt2 -dC/dz+ra =dc/dt }of a tubular reactor as the E(t) obtained does not follow the conventional dispersion model.

Prajakta Gajbhiye, In my opinion, you cannot "incorperate" E(t) into any mass balance equation. However, you can try to modify the mass balance taking into account, apart from longitudinal dispersion, e.g. radial dispersion. The model can also be extended with the dynamics of the catalyst grain. But that's just a guess.