invention that the rates of heat up and quench be rapid direct or indirect quench can be used the quench material added directly into each reaction zone can be broadly any of a wide variety of gases or liquids that can be added quickly to the reactant mixture in order to cool the mixture below the effective reacting temperature while the mixture is in the reactor materials that are non reactive with the reactant mixture are preferred but many common materials can be used these can include a portion of the recycled gas stream from the process having components such as methane ethane propane a portion of the produced liquid hydrocarbons inert gases such as helium or argon and even such materials as water nitrogen and co 2 although these latter materials can react at the temperature found in the reactor it is understood that these material can be added to the reactant stream from the recycle gas stream at such a temperature and in such volume so that the result is a quenching of the reactant stream rather than additional reaction between the reactant stream and the quenched material hydrogen is thus the preferred quench material with a process recycle stream rich in hydrogen being a natural extension of the preferred embodiment depending upon the reaction temperature and the mass flow through the reactor a sufficient amount of quenching material at a suitable temperature is added to the reactant stream within each reaction zone so that the resultant mixture near the exit of the reactor has a temperature of about 200 u00b0 500 u00b0 c the temperature and the amount of quenched material added to each reaction zone are sufficient to quench the reaction mixture rapidly the pressure of the.