Y3+和La3+改性对CeO2(ZrO2)/TiO2催化剂脱硝性能的影响

摘要

采用溶胶-凝胶法制备Y3+和La3+掺杂CeO2(ZrO2)/TiO2(简称CZT)催化剂,研究y3+和La3+掺入对其脱硝性能的影响.采用X射线衍射、氮气吸附脱附、氨气程序升温吸附、氢气程序升温还原以及紫外光光致发光光谱等实验方法对CZT催化剂进行表征.结果表明:y3+和La3+的掺入抑制了TiO2从无定形向锐钛矿型转变,不仅增大了催化剂的弱酸酸量和比表面积,同时提高了CZT催化剂的缺陷浓度和储释氧性能;弱酸酸量和比表面积的增大有利于CZT催化剂表面反应气体的吸附;缺陷浓度和储释氧性能的提高加快了吸附在CZT催化剂表面的NO被氧化速率,有利于催化反应的进行.因此,适量掺入Y3+和La3+会明显提升CZT催化剂的低温脱硝活性,拓宽其活性温度窗口.空速71 400 h-1条件下,0.2La-CZT催化剂在200℃的脱硝率达到85.1％,300℃达到最高(96.5％).%A series CeO2(ZrO2)/TiO2 catalysts (CZT catalyst) were modified with y3+ and La3+ using the sol-gel method.The effect of y3+ and La3+ on catalytic performance of the CeO2(ZrO2)/TiO2 during selective catalytic reduction (SCR) of NOx using NH3 was investigated.Several tests were carried out the characterize the CZT catalysts,such as the X-ray diffraction,nitrogen adsorption and desorption,temperature programmed desorption of ammonia,temperature programmed reduction of hydrogen and photoluminescence spectra.The results show that,the addition of y3+ and La3+ inhibited the transformation of TiO2 from amorphous phase to anatase phase.In addition,both y3+ and La3+ ions increased the specific surface area and amount of weak acid sites in the catalysts,which was beneficial for the adsorption of reaction gas on the catalyst surface.The increase of the defects species concentration and the enhancement of oxygen storage capacity was good for catalytic activity.Therefore,the additions of Y3+ and La3+ improved the catalytic activity of the catalyst at low temperatures and broadened the active temperature window while the amount was appropriate.Under condition with GHSV of 71 400 hl,the catalytic activity (NOx conversion rate) of the 0.2La-CZT catalyst reached 85.1％ at 200 ℃ and 96.5 ％ at 300 ℃ (the highest).