V-Ce/TiO_(2)脱硝催化剂的SO_(2)中毒机理研究

Study of SO_(2) Poisoning Mechanism of V-Ce/TiO_(2) Catalyst for NH3-SCR

通过表相、体相硫组分的表征分析,结合不同温度下含硫气氛下的活性演变及原位红外研究,获得了VCe(0.1)/TiO_(2)催化剂在180、240和300℃下含硫氛围的NH3-SCR反应中毒机理. 180℃下催化剂上沉积了大量的硫酸氢铵和少量的金属硫酸盐,共同导致在8 h内活性从77.8%降至51.2%,热再生后的活性测试结果表明硫酸氢铵的沉积导致了催化剂活性降低8.3%,金属硫酸盐的沉积导致了催化剂活性降低18.3%.原位红外结果表明中毒后催化剂在180℃下的NH3-SCR反应遵循L-H反应路径.随着温度升高至240、300℃,催化剂上沉积的硫酸氢铵逐渐减少,金属硫酸盐含量增加.不同温度下的抗硫活性结果表明,低温NH3-SCR反应需要较高的氧化还原性能,中高温NH3-SCR反应则需要较高的酸性,金属硫酸盐的生成导致了氧化还原性能降低、酸性增加,因此低温NH3-SCR活性大幅降低,中高温活性则能保持在100%.

The poisoning mechanism of V-Ce(0.1)/TiO_(2) catalysts in sulfur-containing NH3-SCR atmosphere at 180,240 and 300℃was obtained by comprehensive characterization of the sulfur components,combined with the activity evolution in sulfur-containing atmosphere at different temperatures and in-situ DRIFTS studies.A large amount of ammonium bisulfate and a small amount of metal sulfate were deposited on the catalyst at 180℃,which together led to a decrease in activity from 77.8%to 51.2%within 8 h.The activity test results after thermal regeneration showed that catalytic activity was decreased by 8.3%,18.3%owing to the deposition of ammonium bisulfate and metal sulfates,respectively.The in-situ DRIFTS results showed that the NH3-SCR reaction of the poisoned catalyst at 180℃followed the L-H reaction path.With the increase of reaction temperature to 240 and 300℃,the ammonium bisulfate deposited on the catalyst gradually decreased and the metal sulfate content increased.The results of the anti-sulfur activity at different temperatures show that the low-temperature NH3-SCR reaction requires high redox properties,and the medium-temperature NH3-SCR reaction requires high acidity.The formation of metal sulfates leads to a decrease in the redox properties and an increase in the acidity,so the lowtemperature NH3-SCR activity decreases dramatically,and the medium-temperature NH3-SCR activity is able to be maintained at 100%.