Abstract:

To improve efficiency of Ce-based desulfurization agent in deep desulfurization of flue gas in fluid catalytic cracking(FCC) petroleum processing, reaction mechanism of SO₂ and O₂ over CeO₂ surface were investigated in both experiments and calculations by density functional theory(DFT). SO₂ removal from simulated flue gas with O₂ presence was carried out over CeO₂ under 60℃ and 200℃. CeO₂ characterization before and after desulfurization by XRD, IR and XPS was used to study changes in valence and relative amount of S and Ce as well as to explore possible oxidative reaction path of SO₂. Models of monomolecular O₂ adsorption and bimolecular O₂ and SO₂ adsorption on O-deficient CeO₂(111) and MgAl₂O₄(111) were established from DFT simulation. SO₂ oxidation and energy barriers of each reaction step were calculated using LST/QST method. Results indicated that CeO₂(111) had better catalytic effect for SO₂ desulfurization than MgAl₂O₄(111) and CeO₂ could transport lattice oxygen in oxidation with SO₃ desorption as rate-control step.

Key words: petroleum, FCC flue gas deep desulfurization, XPS, molecular simulation, adsorption, lattice oxygen transport, rate-control step

摘要：

为提高Ce基脱硫助剂对石油加工过程中流化催化裂化（FCC）烟气深度脱硫效果，采用实验与密度泛函理论（DFT）探究了SO₂、O₂在CeO₂表面的反应过程。通过60℃、200℃反应温度下SO₂、O₂与CeO₂的反应，对反应前后CeO₂样品的XRD、IR、XPS谱图比较分析，探索S、Ce的价态变化和相对含量转变规律，从而推测SO₂可能的反应路径。基于密度泛函理论模拟构造了O₂单分子和SO₂、O₂双分子在CeO₂（111）和MgAl₂O₄（111）O空位表面可能产生的吸附构型；利用LST/QST方法搜索SO₂氧化反应过程，计算各步反应能垒。结果表明CeO₂（111）相比MgAl₂O₄（111）具有更好的SO₂催化效果，其中CeO₂在反应中起到了晶格O传递作用，并进一步推断SO₃的脱附过程是整个反应的速率控制步骤。

关键词: 石油, FCC烟气深度脱硫, XPS, 分子模拟, 吸附, 晶格O传递, 速控步骤