I have a process where 10 mol/s of H2 gas and 1 mol/s of benzene gas are fed into a reactor at 350ºC and 5 bar. The products are then fed to a second reactor at 240ºC and 5 bar to yield cyclohexane.

The conversion is dominated by the second reactor since the reaction is very exothermic (equilibrium constant for the first reactor is 3 orders of magnitude smaller than the second). My question is, why would you have the first reactor at such a high temperature if the conversion is going to be so small? Why would you even have 2 reactors in the first place if one isn't going to contribute to the yield? Could it have to do with burning any impurities in the reactants? Or maybe it has to do with what happens if you cool the gases at constant pressure?

Any help is appreciated, I've been thinking about this non stop for a while!