含铈钒基SCR催化剂脱硝性能及SO_2失活机理研究

掺杂Ce到V_2O_5-WO_3/TiO_2催化剂中,并研究其NH_3-SCR脱硝性能及SO_2失活机理。结果表明,V_1W_5Ce_6 Ti表现出更好的脱硝活性。采用XRD、BET、FT-IR、TG-DSC、XPS等手段表征分析Ce对催化剂性能的影响,并提出V_1W_5Ce_6Ti硫失活机理。结果表明,Ce、V、W都能在催化剂中很好的分散,当Ce的掺杂量达到8%时,有明显的CeO_2特征峰出现。在250℃时,V_1W_5Ti(U)表面会有NH4HSO4和(NH_4)_2SO_4生成。掺杂Ce后,V1W5Ce6Ti催化剂的Brnste酸位和表面化学吸附氧都增加。Ce与烟气中的SO_2和H_2O结合生成硫酸铈盐,从而抑制硫酸铵盐的生成。同时也阻断了Ce~(3+)与Ce~(4+)氧化还原循环,破坏V-O-Ce结构,造成催化剂活性下降。

Activity and SO2 deactivation mechanism of vanadium series catalyst containing cerium

The promotion effect of Ce modification on V₂O₅-WO₃/TiO₂ for the selective catalytic reduction (SCR) of NO_x with NH₃ and the SO_<i>2 deactivation mechanism were investigated. Compared with V₁W₅Ti catalyst, the advantage of V₁W₅Ce₆Ti catalyst shows a good catalytic activity. These catalysts were investigated by means of XRD, BET, FT-IR, TG-DSC and XPS. The results demonstrate that the active components of V and W are well-dispersed, while a small cluster of cubic CeO₂ appears over the V₁W₅Ce₈Ti catalyst. The sulfation of V₁W₅Ti under reactive conditions can generate NH₄HSO₄ and (NH₄)₂SO₄ at 250℃. The Ce additive to V₁W₅Ti could provide stronger Brønsted acid sites and more chemisorbed oxygen. The deposited ammonium sulfate on V₁W₅Ce₆Ti catalyst is much smaller than that on V₁W₅Ti because the cerium sulfates species on the surface of V₁W₅Ce₆Ti is formed and the deposition of ammonium sulfate is inhibited, which can disrupt the redox cycle between Ce³⁺ and Ce⁴⁺ and break the V-O-Ce structure, causing the deactivation of V₁W₅Ce₆Ti catalyst.