不同晶型MnO_x催化还原NO活性研究
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摘要
为研究低温烟气脱硝的高效选择性催化还原(SCR)催化剂的催化活性,采用湿式浸渍法制备了以γ-Al_2O_3为载体、以MnO_x为活性组分的系列MnO_x/γ-Al_2O_3催化剂。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、BET多分子层吸附模型等测试方法对催化剂进行表征,分析Mn负载量对MnO_x晶型、形貌及催化剂比表面积的影响,并进行催化还原NO实验,通过脱硝效率反映不同MnO_x晶型时催化剂的脱硝特性。结果表明,Mn负载量对MnO_x的晶型和形貌产生明显影响。Mn负载量低于0.4mmol/g时,无法形成明显晶核;Mn负载量为0.8mmol/g时,形成球状_β-MnO_2;Mn负载量为1.2mmol/g时,形成棒状α-MnO_2。球状_β-MnO_2提高了MnO_x/γ-Al_2O_3比表面积,含球状_β-MnO_2的MnO_x/γ-Al_2O_3催化剂具有最优的催化还原NO活性,175℃条件下达到84%左右的脱硝效率。H_2O(气态,下同)和SO~3 _2的存在对催化剂脱硝性能产生影响,分别持续通入600mg/mSO_2、6.000%(体积分数)H_2O 480min,脱硝效率分别下降约14百分点和10百分点。
In order to investigate the high efficiency of SCR catalyst for the removal of NO from flue gas at low temperature,a series of MnO_x/γ-Al_2O_(3 )catalysts withγ-Al_2O_(3 )as the support and MnO_(x )as the active component were prepared by wet impregnation method.XRD,SEM,BET and other test methods were used to characterize the catalysts.The influence of Mn loaded amount on the MnO_(x )crystal types,morphology and specific surface area of the catalysts were analysed,and experiments about the catalytic reduction of NO were carried out at low temperature.The denitration characteristics of MnO_(x )catalysts with different crystal types were reflected by denitration efficiency.Results showed that the Mn loaded amount had obvious influence on the crystal types and morphology of MnO_(x )in catalysts.When the Mn loaded amount was less than 0.4mmol/g,no obvious crystal nucleus was formed.When the Mn loaded amount was 0.8mmol/g,layers of sphericalβ-MnO_(2 )crystal were formed.When the Mn loaded amount was 1.2mmol/g,a kind of rod likeα-MnO_2crystal was formed.The sphericalβ-MnO_2crystal improved the specific surface area and had the best catalytic activity.The denitrification efficiency of MnO_x/γ-Al_2O_(3 )with sphericalβ-MnO_2crystal could be delivered to approximately 84%at 175℃.The presence of H_2O(g)and SO_2had an impact on the denitrification performance of the catalyst.With the continuous addition of 600 mg/m~(3 )SO_(2 )or 6.000%H_2O(g)for 480min resulted in a reduction of the denitrification efficiency of 14percentage points and 10percentage points,respectively.
In order to investigate the high efficiency of SCR catalyst for the removal of NO from flue gas at low temperature,a series of MnO_x/γ-Al_2O_(3 )catalysts withγ-Al_2O_(3 )as the support and MnO_(x )as the active component were prepared by wet impregnation method.XRD,SEM,BET and other test methods were used to characterize the catalysts.The influence of Mn loaded amount on the MnO_(x )crystal types,morphology and specific surface area of the catalysts were analysed,and experiments about the catalytic reduction of NO were carried out at low temperature.The denitration characteristics of MnO_(x )catalysts with different crystal types were reflected by denitration efficiency.Results showed that the Mn loaded amount had obvious influence on the crystal types and morphology of MnO_(x )in catalysts.When the Mn loaded amount was less than 0.4mmol/g,no obvious crystal nucleus was formed.When the Mn loaded amount was 0.8mmol/g,layers of sphericalβ-MnO_(2 )crystal were formed.When the Mn loaded amount was 1.2mmol/g,a kind of rod likeα-MnO_2crystal was formed.The sphericalβ-MnO_2crystal improved the specific surface area and had the best catalytic activity.The denitrification efficiency of MnO_x/γ-Al_2O_(3 )with sphericalβ-MnO_2crystal could be delivered to approximately 84%at 175℃.The presence of H_2O(g)and SO_2had an impact on the denitrification performance of the catalyst.With the continuous addition of 600 mg/m~(3 )SO_(2 )or 6.000%H_2O(g)for 480min resulted in a reduction of the denitrification efficiency of 14percentage points and 10percentage points,respectively.
引文
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[12]彭祖辉,仲蕾,李红玉,等.N掺杂MnOx/TiO2低温NH3选择性催化还原NO性能研究[J].中国电机工程学报,2013,33(35):58-66.
[13]郭玉玉,张申,刘鹏飞,等.制备方法对Fe-Mn/ZSM-5/CC催化还原NOx性能的影响[J].太原理工大学学报,2015,46(5):537-541.
[2]KIJLSTRA W S,BRANDS D S,SMIT H I,et al.Mechanism of the selective catalytic reduction of NO with NH3over MnOx/Al2O3[J].Journal of Catalysis,1997,171(1):219-230.
[3]AN Z Y,ZHUO Y Q,XU C,et al.Influence of the TiO2crystalline phase of MnOx/TiO2catalysts for NO oxidation[J].Chinese Journal of Catalysis,2014,35(1):120-126.
[4]RICHTER M,TRUNSCHKE A,BENTRUP U,et al.Selective catalytic reduction of nitric oxide by ammonia over egg-shell MnOx/NaY composite catalysts[J].Journal of Catalysis,2002,206(1):98-113.
[5]李伟曼,刘海弟,陈运法.低温非钒基NH3选择性催化还原催化剂的技术需求和研究进展[J].环境污染与防治,2013,35(7):74-79.
[6]YAO X J,KONG T T,YU S H,et al Influence of different supports on the physicochemical properties and denitration performance of the supported Mn-based catalysts for NH3-SCR at low temperature[J].Applied Surface Science,2017,402:208-217.
[7]戴韵,李俊华,彭悦,等.MnO2的晶相结构和表面性质对低温NH3-SCR反应的影响[J].物理化学学报,2012,28(7):1771-1776.
[8]LI J H,CHEN J J,KE R,et al.Effects of precursors on the surface Mn species and the activities for NO reduction over MnOx/TiO2catalysts[J].Catalysis Communications,2007,8(12):1896-1900.
[9]张恒建,张先龙,张连凤,等.前驱体对锰基SCR催化剂低温脱硝活性的影响[J].合肥工业大学学报(自然科学版),2014,37(7):860-864.
[10]XIA Y N,YANG P D,SUN Y G,et al.One-dimensional nanostructures:synthesis,charavterization,andapplications[J].Advanced Materials,2003,34(22):353-389.
[11]王鸣晓.活性炭载锰氧化物的制备及其催化分解臭氧性能研究[D].北京:清华大学,2014.
[12]彭祖辉,仲蕾,李红玉,等.N掺杂MnOx/TiO2低温NH3选择性催化还原NO性能研究[J].中国电机工程学报,2013,33(35):58-66.
[13]郭玉玉,张申,刘鹏飞,等.制备方法对Fe-Mn/ZSM-5/CC催化还原NOx性能的影响[J].太原理工大学学报,2015,46(5):537-541.
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