热处理天然褐铁矿制备γ-Fe_2O_3及其NH_3-SCR活性探究  

Preparation of γ-Fe_2O_3 Catalyst by Heat Treatment of Natural Limonite for Selective Catalytic Reduction of NO by NH_3

作　　者：徐彬[1] 陈天虎[1] 刘海波[1] 朱承驻[1] 陈冬[1] 邹雪华[1] 蒋阳[2] 

机构地区：[1]合肥工业大学资源与环境工程学院,合肥230009 [2]合肥工业大学材料科学与工程学院,合肥230009

出　　处：《环境科学》2016年第7期2807-2814,共8页Environmental Science

基　　金：国家自然科学基金项目(41402030;41372045);中国博士后科学基金项目(2014M551794);中央高校专项科研基金项目(2014HGCH0007)

摘　　要：以天然褐铁矿为前驱体,通过热处理制备γ-Fe_2O_3作为NH3-SCR催化剂.借助XRD、XRF、XPS、NH3-TPD、FR-IR等表征方法,考察反应温度、褐铁矿中的锰氧化物以及H_2O和SO_2对催化剂选择催化还原NO活性的影响并与α-Fe_2O_3作对比.结果表明,由于γ-Fe_2O_3表面比α-Fe_2O_3具有更强的酸性,使得γ-Fe_2O_3的脱硝温度窗口（200~350℃）宽于α-Fe_2O_3（200~300℃）,且在活性温度窗口下,催化剂脱硝效率达到99%以上;γ-Fe_2O_3催化剂中少量MnO_2的存在,提高了催化剂低温段（100~200℃）脱硝活性,降低了高温段（400~450℃）脱硝活性;SO_2的存在会使γ-Fe_2O_3的脱硝温度窗口向高温区偏移100℃、体积分数为5%的H_2O对脱硝反应的抑制作用很小,但当SO_2和5%H_2O同时存在,尤其是SO_2的体积分数达到0.12%时,硫酸铵盐类的迅速生成会大大降低γ-Fe_2O_3的脱硝活性;此外,γ-Fe_2O_3经过NH3-SCR反应后,其磁化率略有降低,催化剂仍然具有磁回收循环利用的潜力.Natural limonite was used as a precursor to prepare γ-Fe_2O_3 via thermal treatment. The influences of reaction temperature,manganese oxides existing in limonite and coexisting SO_2 and H_2O on the catalytic reduction activity of the preparedγ-Fe_2O_3 were evaluated,and the activity of SCR was compared with that of α-Fe_2O_3,by means of XRD,XRF,XPS,NH3-TPD,FT-IR and so on.The results showed that because the surface acidity of γ-Fe_2O_3 is stronger,the SCR temperature window of γ-Fe_2O_3 was 200-350℃being broader than that of α-Fe_2O_3（ 200-300℃）,and in the active temperature window,the NO removal reached over 99%. The existence of MnO_2 in the newly formed γ-Fe_2O_3 slightly decreased the SCR reactivity at lower temperature（ 100-200℃）,while it decreased the SCR reactivity at higher temperature（ 400-450℃）. The existence of SO_2 led to the shifting of temperature window by100℃ from 200-350℃ to 300-450℃,and the volume fraction of 5% H_2O only had a tiny negative effect on the SCR reactivity of γ-Fe_2O_3. However,the coexisting SO_2 and H_2O,especially when the volume fraction of SO_2 reached 0. 12%,significantly decreased the SCR reactivity due to the generation of ammonium sulfate. Besides,although the magnetic susceptibility of reacted γ-Fe_2O_3 experienced a slight decrease compared with the newly prepared γ-Fe_2O_3,the catalysts could still be used repeatedly by magnetic recycling.

关 键 词：褐铁矿 热处理 Γ-FE2O3 NH3-SCR H2O SO2 

分 类 号：X701[环境科学与工程—环境工程]