NiMoS加氢脱硫催化剂表面非化学计量硫物种动态平衡

加氢脱硫(HDS)催化剂NiMoS活性相表面非化学计量硫(S_x)物种的动态变化是HDS活性的决定因素。在HDS过程中，S_x物种处于动态平衡，且这一平衡与催化剂、H₂S分压及硫化温度相关。笔者采用程序升温的方法研究了催化剂载体、助剂Ni、硫化温度、H₂S分压对NiMoS催化剂表面S_x物种的影响。结果表明：催化剂载体对S_x物种的总量和还原性具有显著影响，Ni的引入显著促进S_x物种还原，提升HDS活性；硫化气相H₂S分压决定了催化剂表面S_x物种含量，气相中H₂S分压升高易使S_x物种增多，表面可利用NiMoS活性位减少，从而导致HDS活性降低。S_x物种含量与H₂S分压及硫化温度的关系符合热力学平衡及van′t Hoff等压方程，进一步将S_x物种含量与HDS反应速率系数进行关联，提出H₂S分压S_x物种含量HDS活性之间的定量关系。

Dynamic Equilibrium of Surface Non-Stoichiometric Sulfur Species on a NiMoS Hydrodesulfurization Catalyst

The dynamic equilibrium of surface non-stoichiometric sulfur species (S_x) between the NiMoS hydrodesulfurization (HDS) catalyst and the gas phase is a determinant of HDS activity. During HDS reaction, S_x is in a dynamic equilibrium state, which is related to catalyst, H₂S partial pressure and sulfidation temperature. The effects of catalyst carrier, Ni promoter, sulfidation temperature and H₂S partial pressure on S_x over the NiMoS catalysts were studied by temperature-programmed reduction. The results show that catalyst support has a significant impact on the total amount and reducibility of S_x, and the introduction of Ni can significantly promote the reduction of S_x species and enhance HDS activity; the content of S_x species also depends on H₂S partial pressure in the sulfidation process: the increasing H₂S partial pressure in gas phase tends to increase the S_x content and decrease the number of accessible NiMoS sites, thus resulting in a decrease in HDS activity. The relationship among S_x amount, H₂S partial pressure and sulfidation temperature reasonably follows thermodynamic equilibrium and van’t Hoff isobaric equation. On this basis, S_x content is further correlated with HDS reaction rate coefficient, and a quantitative relationship among H₂S partial pressure, S_x content and HDS activity is proposed herein.