Reactor design and fabrication

Fixed-bed reactors for distributed fuel processing applications are normally comprised of an insulated stainless steel vessel or tube containing a mesh at the reactor inlet and outlet. 

The fabrication of ceramic monoliths is performed mainly via extrusion techniques [9] resulting in usually elliptic or squareshaped monoliths. Cell densities as high as 1600 cells per square inch (cpsi) are achieved [9], which corresponds to a channel width of about 500 pm of the mostly rectangular or hexagonal channels. Typical key features are 75% porosity and a geometric surface area of 2.8 m /1 for 400 cpsi for ceramic monoliths [10]. The thermal shock resistance amounts to 800°C and higher. 

Owing to the low surface area of the monoliths, a catalyst carrier such as alumina or ceria is deposited onto them usually by wash coating [11]. The ceramic construction material is well compatible with these carriers, does not migrate into the catalyst coatings, and the precious active metal species of the catalysts do not migrate into the monoUth bodies [1]. The most widely used construction material for ceramic monolith carriers is cordierite [9] with alumina being an alternative. 

The catalyst coatings in ceramic and metalHc monoliths are not always evenly distributed, which affects the performance of the monoliths concerning flow equipartition and temperature profile, because the heat conduction is also affected [12]. 

Microstructured plate heat exchangers are stacked arrangements with a multitude of parallel minichannels and high sur-face-to-volume ratios in the range of 200 m /m . The preferred construction material is stainless steel. Wet chemical etching, initially developed for silicon micromachining, is suited for mass 

---