Development of Ni/ZnO desulfurization adsorbent with high stability: formation of Zn2SiO4 and the impact from substrate

Abstract Ni/ZnO is used as a catalytic sorption material together with structural substrate for the S Zorb desulfurization process. At industrial scale, the use of Al2O3/SiO2 materials as such structural substrate results in long-term deactivation via the formation of Zn2SiO4 under hydrothermal conditions. This work aims for the investigation of the origin of such solid-state reaction by applying multiple characterization techniques, e.g. in-situ XRD, solid-state NMR and FT-IR. Two different common Al2O3/SiO2 materials, i.e. perlite and Al-montmorillonite, are studied comparatively in this work. As a result, Al-montmorillonite shows superior hydrothermal stability than perlite. It is observed that the density and reactivity of the Si-OH group is directly correlated to the formation rate of Zn2SiO4. Moreover, it has been further shown that the hydrogen-bonded Si-OH and bound molecular water are the major active species which lead to the formation of Zn2SiO4, as compared to the isolated silanol group. At last, both substrates are used for the preparation of the catalytic sorption materials in the S Zorb process. The desulfurization results show that the sorbent that has been prepared by using Al-MMT as structural substrate has maintained the sulfur-removal activity for much longer time than the one prepared from perlite.