Method of carrying out heterogeneous catalytic chemical processes

In a method of carrying out a heterogeneous catalytic chemical process at non-adiabatic conditions by passing a stream of a process fluid in one overall flow direction through a catalyst contained in a catalyst chamber defined by walls two of which are substantially uniformly spaced, and transmitting heat through at least one of the two substantially uniformly spaced walls between the process fluid inside the catalyst chamber and a fluid outside the catalyst chamber, said catalyst having a structure of channels arranged in groups of substantially parallel channels causing the process fluid to be subdivided into a plurality of sub-streams having actual flow directions angled to the two uniformly spaced walls and the overall flow direction, and changing direction whenever reaching one of the walls, the improvement which comprises that the mass flow towards one of the two substantially uniformly spaced walls, at any cross section orthogonal to the overall flow direction, is approximately equal to the mass flow towards the other of said two walls, the flow direction of the sub-streams in one group of channels being different from that in the neighboring group or groups of channels, and that the actual flow direction of any sub-stream is changed whenever it reaches one of the two substantially uniformly spaced walls in leaving a channel and entering neighboring channels, so as to direct the sub-stream towards the other of said substantially uniformly spaced walls.