Facile hydrothermal synthesis of ZnO nanoparticles on silicalite-1: Effect of ultra ZnO Nano size on desulfurization activities

Abstract

Reactive adsorption desulphurization (RADS) is an excellent technique for producing ultra-clean sulphur-free fuel in mild operating conditions. The sulphur adsorption capacities of the catalysts strongly relate to the stable nano size of ZnO nanoparticles, dispersion of active phases, and the acidity of the catalysts. In this work, a series of ultra nano-sized ZnO nanoparticles with a nano-size of 2–8 nm supported on silicalite-1 were synthesized via a homogeneous hydrothermal technique and utilized as a support for the dispersion of Ni nanoparticles. The RADS activity of the NiZnS-1 catalyst for thiophenic compound substantially increased from 163 mg S/g to 205 mg S/g with the decrease of the ZnO particle size from 8 nm to 2 nm. The NiZnS-1 adsorbents were characterized through N2 adsorption-desorption, Raman spectroscopy, X-ray diffraction, High-resolution transmission electron microscopy, and Temperature-programmed desorption of ammonia. Catalytic activity tests show that NiZnS-1(6) adsorbent with ZnO particle size of 2–3 nm achieved an excellent breakthrough sulphur adsorption capacity of 57.5mgS/g and accumulative sulphur adsorption capacities of 205 mg S/g while dealing with model gasoline (1500 mg/L). Which is four folds higher than NiZnS-1(20) adsorbent with a compromised RADS capacity of 163 mg S/g. This superior desulphurization activity and sulphur adsorption capacity for NiZnS-1 adsorbent strongly depend on to the size of ZnO nanoparticles, the diffusion rate of the reactant’ and product molecules, the adsorbent total acidity and ZnO/Ni nanoparticles dispersion on the support. Upon five desulfurization regeneration cycles, NiZnS-1 showed high stability without apparent activity loss, revealing that the ZnO particle size is intact after multiple cycles. A mechanism is proposed based on the desulphurization results.