The compact chemical reactor with a central axis includes at least two unit reactors disposed adjacent to each other to form front and back sides of the compact chemical reactor; a front and back reactant plenum communicating with the front and back side respectively; at least one of the plenums comprises a reactant; and unit reactors comprising: a front cavity between front and back process layers; a back cavity between back and front process layers of adjacent unit reactors; the process layers facilitate transport processes between reactant plenums; each cavity communicates with one side of the compact chemical reactor; a front and back perimeter barrier on the back and front process layers respectfully, substantially surrounding respective cavities. At least one of the unit reactors comprise at least one frame formed from one of the process layers, at least one of the perimeter barriers, and at least one of the cavities.