Deactivation, reactivation and memory effect on Co–B catalyst for sodium borohydride hydrolysis operating in high conversion conditions

A system with a continuous reactor to produce hydrogen by sodium borohydride hydrolysis was designed and built. The purpose was to test a supported Co–B catalyst durability upon cycling and long life experiments in high conversion conditions. A Stainless Steel monolith was built and calcined to improve adherence. For comparison a Ru–B catalyst was tested upon cycling. Both Co–B and Ru–B catalysts are durable during 6 cycles and then deactivate. A known reactivation procedure has proven to be more effective for the Co–B than for the Ru–B catalyst. This is related to stronger adsorption of B–O based compounds on the Co–B catalyst which is reversible upon acid washing. For the Ru–B catalyst deactivation may be more related to particle agglomeration than to the adsorption of B–O based species. The continuous system enlarges the catalysts durability because of the continuous borate elimination at elevated temperatures.

► Reactor based on sodium borohydride hydrolysis producing 1 L min−1 hydrogen. ► Stainless Steel supported Co–B and Ru–B catalysts were tested in cycling experiments. ► Both deactivate after 6 cycles but Co–B reactivates efficiently by acid washing. ► Ru–B deactivates mainly by particle growth and Co–B by B–O species' adsorption. ► System is efficient for long use because of high temperature and product elimination.