Abstract:

Selective removal of heavy molecular mercaptan from FCC gasoline after hydrodesulfurization is an effective method for low-cost and efficient production of clean gasoline in China. CoMo/Al₂O₃ hydrodesulfurization catalysts with different pore sizes were prepared using pore saturation impregnation method. After crushing to different particle sizes, they were subjected to sulfurization treatment. Simulated and real FCC gasoline after hydrodesulfurization were evaluated in a fixed bed reactor, and the reaction effect of catalyst removal of heavy molecule mercaptans was investigated under different process conditions. The in-situ adsorption reaction process intensification method was used to enhance the selective removal of heavy molecule mercaptans. The results showed that mercaptans are heavy molecular mercaptans formed by the combination of olefins and hydrogen sulfide in gasoline, with various types and low content of each mercaptan. The removal reaction of regenerated mercaptan is limited by mass transfer at low temperature, and the chemical reaction of hydrogen sulfide and olefin to regenerate mercaptan reaches thermodynamic equilibrium, which cannot be effectively removed by current MoS₂ catalysts. By reducing the catalyst particle size and increasing the catalyst pore size, the diffusion limit of mercaptan removal reaction can be effectively reduced. At the same time, the in-situ adsorption reaction process intensification method is used to remove the hydrogen sulfide generated during the mercaptan removal reaction process, avoiding the recombination reaction between hydrogen sulfide and olefins. It can efficiently remove heavy molecule mercaptan under mild conditions and produce clean gasoline with low-cost.

Key words: heavy molecular mercaptan, FCC gasoline, olefin, process intensification

摘要：

选择性脱除加氢后催化裂化汽油中的大分子硫醇硫，是低成本高效生产国六清洁汽油的有效方法。采用孔饱和浸渍法制备孔径不同的CoMo/Al₂O₃加氢催化剂，破碎至不同粒径后，对其进行硫化处理；在固定床反应器中分别使用模拟催化裂化汽油和加氢后催化裂化真实汽油进行评价，并考察工艺条件对催化剂脱除大分子硫醇的反应效果，采用原位吸附反应过程强化方法，强化大分子硫醇的选择性脱除。结果表明：加氢后催化裂化汽油中的硫醇是汽油中烯烃与硫化氢化合生成的大分子硫醇，种类多，每一种硫醇的含量低；再生成硫醇的脱除反应在低温下受传质限制，硫化氢与烯烃再生成硫醇的化学反应达到热力学平衡，依靠目前MoS₂类催化剂无法高效脱除，通过减小催化剂粒径和增大催化剂孔径的手段可有效减弱硫醇脱除反应的扩散限制，提高催化剂硫醇脱除效果，同时通过原位吸附反应过程强化方法将硫醇脱除反应过程中生成的硫化氢移出反应区，避免硫化氢与烯烃再结合反应发生，可以在反应温度160℃、体积空速4h^-1、反应压力0.3MPa、氢油体积比10的缓和条件下高效脱除大分子硫醇，低成本生产清洁汽油。

关键词: 大分子硫醇, 催化裂化汽油, 烯烃, 过程强化