Process and apparatus for controlling reaction temperatures with heating arrangement in series flow

A process for contacting reactants with a particulate catalyst in a channel reactor while indirectly contacting the reactants with a heating fluid, said process comprising:

• retaining catalyst particles in a plurality of reaction stacks, each reaction stack having a plurality of vertically and horizontally extended reaction channels and a plurality of vertically and horizontally extending heating channels for providing indirect heat exchange;
• passing a reactant stream to at least two of the reaction stacks in parallel flow and contacting said catalyst with said reactant stream therein;
• passing a heating fluid through the heating channels of the at least two reaction stacks to create series flow of heating fluid through the reaction stacks;
• heating the heating fluid as it passes from one reaction stack to another reaction stack;
• recovering the heating fluid from the last reaction stack in the series of reaction stacks and returning at least a portion of the heating fluid to the first reaction stack in the series of reaction stacks;
• and,
• recovering a reacted stream from the plurality of reaction stacks.