Miniature Hydrogen Generator From Ammonia Decomposition And Methanol Steam Reforming

Polymer electrolyte membrane fuel cells(PEMFCs) have received great attention as an attractive alternative of the primary and secondary batteries for vehicles and electrical devices especially in remote locations,due to their higher efficiencies and energy densities.One promising way to avoid hydrogen storage problems is to use a microreactor to liberate the hydrogen on demand from higher energy density H-containing compounds.A nontrivial challenge conflicting this effort is to render novel microreactor technology to satisfy the fundamental criteria needed for a miniature fuel cell power system.In this paper,design concept and fabrication of the miniature hydrogen generators from ammonia decomposition and methanol steam reforming(MSR) have been illustrated,according to the real-world forms of the catalysts for ammonia decomposition and methanol steam reforming.Lab-scale prototype generators have been demonstrated at a hydrogen yielding rate of more than 1000 standard cubic centimeter per minute(sccm).A miniature ammonia cracker was developed for portable fuel cell power supply. Novel microfibrous CeO₂-promoted Ni/Al₂O₃ catalyst monoliths was structured in it. This cracker showed pleasing operability for high efficiency H₂ production via ammonia cracking with low pressure drop.Roughly 158 W equivalents of H₂ could be produced with ammonia conversion of＞99.9%at 600℃and 1100 sccm ammonia feed gas rate within this cracker through entire 300 h test.Sulfuric acid as a carbon fiber sheet impregnated adsorbent,can effectively absorb the ammonia,so that the concentration of ammonia down to ppb level.In addition,a combinatorial approach by increasing the parallel operation of the micro-reactor unit can be used for easily extending into a small array of ammonia decomposition equipment.Cu-based catalysts,precious metal Pd-based catalysts as well as non-precious metals ZnCa-based catalysts were developed for methanol steam reforming reaction system(MSR).For CuZnAl derived from hydrotalcite precursor and Pd-ZnO/Al₂O₃ catalyst system,the type of catalyst particles is superior to the microfibrous catalyst. The flat multi-channel microreactor was appropriate used for catalyst particles by taking the beneficial properties in terms of small unit size,high heat transfer and low pressure drop.The tubular microreactor showed pleasing operability for MSR,which is made from Ni microfibrous entrapped particulates ZnCaAl catalyst.The reactivity of ZnCaAl catalyst through the chemical modifications with copper was not significantly improved.The microreactor stability of each reaction system was tested. It was found that at optimal reaction condition,more than 1000 sccm of hydrogen was produced with high methanol conversion(＞95%) through entire＞100 h.