Adjustment of the ZSM-5 zeolite support towards the efficient hydrogen production by ethanol steam reforming on cobalt catalysts

Abstract

The world is on track for replacing fossil fuels with alternative energy carriers. In the face of the ongoing global energy transformation, the focus is on hydrogen. Its production in the ethanol steam reforming (ESR) process with the use of a substrate from bio-sources deserves special attention. The ESR process requires a catalyst, which should be selective and resistant to the deactivation processes. We have taken a challenge to develop the cobalt catalyst based on the ZSM-5 zeolite support. We synthesized a series of catalysts based on zeolite with increasing Si/Al ratios (32, 750, ∞ that is Al-free zeolite) and different zeolite morphology. The substantial difference in their performance we discussed based on the multifaceted physicochemical characterization and unique operando UV–Vis and FT-IR spectroscopy studies in the ESR conditions. We have checked the effect of potassium introduction to the Co|ZSM-5 catalyst. The increase in ethanol conversion and decrease in selectivity to undesired C2H4 product with the decrease of the Al content, and further competitive activity and stability of the Al-free catalyst we discussed in terms of the zeolite acidity and its impact on the cobalt phase oxidation state. The advantage of nanometric zeolite over the micrometric one, we attributed to much better dispersion of cobalt active phase over its surface. Thus, the adjustment of zeolite support properties allows us to get the extraordinary ESR catalyst. Our results overthrow the existing paradigm of low activity and stability of zeolite-based ESR catalysts, opening the way to the development of competitive catalysts that give real hope for implementation.