Reactive adsorption desulfurization of thiophene over NiMo/ZnO, a new adsorbent with high desulfurization performance and sulfur capacity at moderate temperature

Abstract

3Ni7Mo/ZnO adsorbent was synthesized by a two-step impregnation method for reactive adsorption desulfurization (RADS) experiments. XRD and Raman spectra revealed the formation of NiMoO₄ and ZnMoO₄ phases in fresh 3Ni7Mo/ZnO. Different from Ni/ZnO adsorbents, 3Ni7Mo/ZnO adsorbents showed activity recovery after a period of reaction time at 280 °C, 3 MPa H₂. This is due to the formation of the Ni–Mo–S phase, which is known as a highly effective hydrodesulfurization active site. The formation of H₂S on the Ni–Mo–S improved the sulfur transfer rate, leading to the recovery of RADS activity. The RADS performance of 3Ni7Mo/ZnO is closely dependent on the pre-reduction temperature. A high RADS performance and large sulfur capacity is achieved for reduction at 280 °C. The sulfur capacity of 3Ni7Mo/ZnO reduced at 280 °C is about 41% higher than that of 3Ni/ZnO, and 15% higher than that of 10Ni/ZnO. H₂-TPR, XPS, TEM and XRD characterizations demonstrated that at a higher reduction temperature Ni and ZnO can promote the reduction of Mo species, generating low valence species like Mo⁴⁺ oxide, which is difficult to be sulfided to the Ni–Mo–S phase under the reaction conditions and hinders sulfur transfer from NiS_x to ZnO.