SO_(2)对La_(0.65)X_(0.35)FeO_(3)钙钛矿催化剂协同催化氧化NO和甲苯的影响

Effect of SO_(2) on the simultaneous oxidation of NO and toluene by La_(0.65)X_(0.35)FeO_(3)(X=Cu,Ce,Mn,Co)perovskite catalysts

采用KIT-6硬模板辅助溶胶凝胶法制备了不同过渡金属元素A位掺杂改性的La_(0.65)X_(0.35)FeO_(3)(X=Cu、Ce、Mn、Co)钙钛矿催化剂,并利用XRD、BET、SEM、H_(2)-TPR、热重(TGA)、SO_(2)-TPD及XPS表征了SO_(2)对La_(0.65)X_(0.35)FeO_(3)钙钛矿催化剂协同催化氧化NO和甲苯的活性影响机制。结果表明,过渡金属的引入可提高催化剂催化性能,La_(0.65)X_(0.35)FeO_(3)钙钛矿催化剂在温度为100~400℃时表现出比LaFeO_(3)催化剂更高的活性。其中,La_(0.65)Co_(0.35)FeO_(3)催化剂活性最佳,在300℃时其NO转化率为60%,甲苯的T90为330℃。另外,SO_(2)对La_(0.65)X_(0.35)FeO_(3)钙钛矿催化剂协同催化氧化NO和甲苯的活性均表现为抑制作用。这是由于SO_(2)容易和催化剂的金属位点发生反应生成表面硫酸盐沉积物,导致活性位点失效并堵塞孔道结构,从而会抑制NO和甲苯的氧化反应。然而,过渡金属的A位掺杂可增大表面积、增强氧化还原性,以引起结构畸变而产生更多的氧空位,提供更多活性位点,从而减弱SO_(2)的抑制作用。本研究可为开发高效协同催化氧化氮氧化物(NO_(x))和挥发性有机化合物(VOCs)的抗硫催化剂提供参考。

In this study,a series of A-site substituted La_(0.65)X_(0.35)FeO_(3)(X=Cu,Ce,Mn,Co)catalysts were synthesized via a sol-gel method using KIT-6 as the hard template.And the characterizations of XRD,BET,SEM,H_(2)-TPR,thermogravimetry(TGA),SO_(2)-TPD and XPS were used to investigate the effect mechanism of SO_(2) on the activity of simultaneous catalytic oxidation of NO and toluene.The results showed that the introduction of transition metals could improve the performance of the catalyst.The La_(0.65)X_(0.35)FeO_(3) perovskite catalyst exhibited higher activities than LaFeO_(3) catalyst in the temperature range of 100~400℃.The La_(0.65)X_(0.35)FeO_(3) catalyst performed the best activity.The NO conversion was 60%at 300℃,and the T90 of toluene was 330℃.Besides,SO_(2) had an inhibitory effect on the co-catalytic oxidation of NO and toluene by La_(0.65)X_(0.35)FeO_(3)(X=Cu,Ce,Mn,Co)catalysts,which was due to the fact that SO_(2) was easy to oxidize with the metal sites to form sulfates covering the surface of catalysts,resulting in the reduction of the active sites and blocking of the pore structure,thereby inhibiting the oxidation reaction of NO and toluene.However,the A-site doping of transition metals X(X=Cu,Ce,Mn,Co)could increase the surface area and enhance the redox property,thus causing structural distortion and generating more oxygen vacancies and providing more active sites,thereby weakening the inhibitory effect of SO_(2).This study can provide a reference for the development of sulfur-resistant catalysts for the efficient simultaneous catalytic oxidation of nitrogen oxides(NO_(x))and volatile organic compounds(VOCs).