Tubular membrane-like catalyst for reactor with dielectric-barrier-discharge plasma and its performance in ammonia synthesis Original Research Article

A membrane-like alumina tube was designed as a new type of catalyst for a reactor with plasma produced by dielectric-barrier-discharge. Anodizing the inner wall of an aluminum tube at dc 100 V using an oxalic acid solution formed an alumina film with straight pores of uniform size, each of which was developed independently and perpendicularly to the macroscopic surface. The gas-permeable membrane was obtained after chemical removals of the unanodized aluminum and the barrier layer on the outside. It was also confirmed that fine ruthenium particles were deposited on the pore walls of the alumina by immersing the tube in a saturated n-hexane solution of dodecacarbonyltriruthenium, followed by calcination and reduction. When the pure alumina membrane was introduced into nitrogen–hydrogen plasma, the ammonia yield was enhanced at each reaction condition. A further improvement was observed for the Ru-loaded catalyst. These results clearly indicate a synergistic effect of plasma and catalysis of the alumina and ruthenium on the ammonia synthesis.