柱状V2O5/AC中V2O5的分布特征对烟气脱硫活性的影响

采用过量浸渍(XS)、等体积浸渍(PV)和半等体积浸渍(HPV)方法,分别制得3种柱状V₂O₅/AC催化剂,并对其脱硫能力进行评价.结果表明:尽管这3种方法制取的催化剂总w(V₂O₅)相同(均为0.5%),但V₂O₅在柱状颗粒中的分布差异却很大;其中半等体积浸渍法制备的催化剂外层w(V₂O₅)最高,等体积浸渍法的w(V₂O5)居中,过量浸渍法的w(V₂O₅)最低.脱硫前期,催化剂外层的w(V₂O₅)对脱硫活性的影响很大,外层w(V₂O₅)高的催化剂脱硫活性较高;脱硫后期,催化剂外层w(V₂O₅)对脱硫活性的影响变小,而内层w(V₂O₅)的影响变大,内层w(V₂O₅)高的催化剂脱硫活性较高.      

V2O5/TiO2与MoO3/TiO2催化剂表面结构形貌及其对催化氧化碳烟活性的影响

为研究纳米级V₂O₅与MoO₃催化剂表面结构对其催化氧化碳烟活性的影响,以TiO₂为载体,采用等体积浸渍法制备了不同负载率(5%、10%、20%、40%)的V₂O₅/TiO₂与MoO₃/TiO₂催化剂,通过扫描电镜(SEM)、X射线衍射仪(XRD)对比研究了2种催化剂在TiO₂载体上的分散状态及物相结构.以Printex-U碳黑为试验用碳烟,采用热重分析仪对V₂O₅与MoO₃催化剂催化碳烟氧化的活性进行了比较.结果表明:V₂O₅与MoO₃在TiO₂载体上均存在一个单层分散饱和阈值,分别为V20(负载率为20%,下同)、Mo10,在该阈值前后活性组分在载体上分别以单层分散状态和明显的晶态存在.对于V₂O₅催化剂,其最佳催化活性出现在负载率接近单层分散饱和阈值时,与无催化状态相比,T_i(起燃温度)、T_p(最大失重率温度)以及T_f(燃尽温度)分别下降了69.1、46.0、23.0 ℃,有明显的阈值效应.而对于MoO₃催化剂,因其自身低熔点性而表现出良好的表面迁移能力,再加上α-MoO₃晶体特有的层状结构,使其可释放出更多的晶格氧,随着负载率的增加,该催化剂催化氧化碳烟活性持续增加,并且未观察到明显的阈值效应.研究显示,在相同负载率下,MoO₃催化剂催化氧化碳烟活性均高于V₂O₅催化剂.      

ZrO2掺杂对V2O5-MoO3/TiO2催化剂脱硝性能的影响

采用浸渍法制备了一系列V₂O₅-MoO₃/TiO₂和V₂O₅-MoO₃/TiO₂-ZrO₂催化剂,考察了ω(V₂O₅/TiO₂)、ω(MoO₃/TiO₂)及ω(ZrO₂/TiO₂)对催化剂选择性催化还原NO性能的影响。结果表明:ω(V₂O₅/TiO₂)为3%,ω(MoO₃/TiO₂)为6%,ω(ZrO₂/TiO₂)为30%的催化剂具有最佳的脱硝活性、较低的SO₂氧化率及较好的抗硫抗水性能。采用XRD、TG、BET、SEM、H₂-TPR及NH₃-TPD等手段,对上述催化剂的理化性能及结构进行表征。结果表明:掺杂ZrO₂的催化剂具有更好的选择性催化还原NO活性,这与其较大的比表面积、较多的表面羟基、均匀的粒径、优良的氧化还原性能和较多的弱酸性位有关。     

CuO-WO3/TiO2催化剂制备方法对NH3-SCR脱硝性能的影响

分别采用溶胶-凝胶法和浸渍法制备xCuO-yWO₃/TiO₂催化剂(x,y分别代表样品中ω(CuO)和ω(WO₃)),并在微型固定床反应器中对制备的xCuO-yWO₃/TiO₂催化剂进行选择性催化还原脱硝(NH₃-SCR)性能评价。结果表明:采用溶胶-凝胶法制备的2CuO-6WO₃/TiO₂催化剂具有较好的脱硝性能,在250~350 ℃,NO_x转化率达到90%以上,相较于浸渍法制备的2CuO-6WO₃/TiO₂催化剂活性明显提高。并采用BET、XRD、H₂-TPR、NH₃-TPD和XPS等表征手段对制备的催化剂进一步表征分析,结果表明:通过溶胶-凝胶法制备2CuO-6WO₃/TiO₂催化剂的比表面积和表面化学吸附氧明显提高,且还原能力和酸性增强,对NH₃的吸附能力亦有所提高,因此溶胶-凝胶法制备的2CuO-6WO₃/TiO₂催化剂表现出较好的NH₃-SCR脱硝性能。     

制备参数对Mn-Ce/TiO2催化剂脱硝性能的影响

以锐钛矿型TiO₂为载体,采用分步共混法制备了Mn-Ce/TiO₂催化剂,通过考察不同活性组分前驱体、焙烧温度以及活性组分负载量对催化剂样品脱硝性能的影响,以确定最佳制备参数;结合XRD（X射线衍射）、XPS（X射线光电子能谱分析）、BET比表积等表征手段研究制备参数对催化剂性能的影响.结果表明:无定型态MnO₂含量越多,越有利于提高催化剂的脱硝活性;催化剂样品表面原子浓度比Mn/Ti[或（Mn+Ce）/Ti]越高,催化剂表面有效活性组分越多,催化剂脱硝活性越好.以自制Mn盐（MX）为前驱体,在Mn-Ce活性组分负载量为16%时,经500℃焙烧的催化剂样品脱硝活性最高;反应空速为10000 h-1,反应温度为80℃时,其脱硝效率可达80%,150℃时脱硝效效率可达99%.      

Z-scheme V2O5-Ag2O/g-C3N4异质结制备及其可见光催化性能

采用原位生长法制备V₂O₅,并将其与Ag₂O/g-C₃N₄水热复合制备V₂O₅-Ag₂O/g-C₃N₄复合光催化剂.利用XRD、FT-IR、SEM和UV-Vis DRS等方法对样品的形貌结构及光学性质进行表征.结果表明,V₂O₅成功掺杂在Ag₂O/g-C₃N₄上,与Ag₂O/g-C₃N₄相比,复合材料对可见光的吸收范围增大;在可见光照射180min后,V₂O₅掺杂量为15%的复合材料对亚甲基蓝(MB)的降解率达到99.10%.经过3次循环降解后,复合材料对MB的降解率保持85%以上,表明其具有良好的稳定性.通过掩蔽实验推测,空穴(h⁺)是光催化体系中主要的活性物质,其光催化性能增强的机理是Ag₂O与g-C₃N₄复合界面形成p-n异质结,并与V₂O₅之间的复合过程符合Z-scheme可见光驱动机制,有效阻碍了光生电子-空穴对的复合,促进活性物质的产生.     

γ-Al2O3酸性修饰稀土尾矿NH3-SCR脱硝性能

为增加脱硝催化剂的酸性位点和比表面积,以稀土尾矿为活性主体,通过物理球磨方式添加γ-Al₂O₃,制得NH₃-SCR催化剂,脱硝温度为100~400℃.结果表明：原尾矿脱硝活性为7.6%,γ-Al₂O₃的脱硝活性为9.4%,稀土尾矿添加50%γ-Al₂O₃脱硝活性达到了64.8%,即添50%γ-Al₂O₃后加极大程度地提高了尾矿的脱硝活性.XRD实验结果表明：Al₂O₃不会与尾矿成分发生反应生成新的物质.SEM实验结果表明：当添加γ-Al₂O₃低于50%时,γ-Al₂O₃均匀分散在尾矿表面,当添加65%γ-Al₂O₃和80%γ-Al₂O₃时,γ-Al₂O₃发生团聚,分散性较差.NH₃-TPD实验结果表明：添加γ-Al₂O₃为脱硝催化剂增加酸性位点,但是当添加γ-Al₂O₃过低时（15%、35%）,吸附NH₃量不足,催化反应进行不完全.BET实验结果表面：添加γ-Al₂O₃可以增加尾矿的比表面积.     

钒酸盐络合剂对V2O5/TiO2 SCR催化剂织构和催化性能的影响

以商业锐钛矿型TiO₂为载体,通过浸渍法制备了3种不同钒酸盐络合剂的V₂O₅/TiO₂催化剂,并考察不同钒酸盐络合剂对该3种催化剂SCR反应的影响。对前驱体溶液的钒配合物价态、pH值,以及对催化剂样品进行H₂-TPR、BET比表面积和孔结构特征、NH₃-TPD、XRD、拉曼光谱、紫外等表征。研究发现,不同络合剂会影响钒酸盐在前驱体溶液中的价态,同时影响前驱体溶液的pH值,但是在测试温度范围内,该3种催化剂的SCR反应在活性和N₂选择性均无明显区别。通过不同的表征方法可知:催化剂的比表面积、孔结构、表面钒氧化物的聚合程度、H₂反应活化能、催化剂表面酸量均没有明显区别,前驱体溶液中钒配合物的价态和pH值对催化剂样品的SCR反应催化性能没有明显影响。     

DFT模拟VPO/TiO2催化剂表面NO和NH3吸附的研究

氮氧化物(NO_x)作为主要大气污染物之一，严重影响环境安全和人类健康。选择性催化还原法(NH₃-SCR)是目前脱除NO_x最有效的治理方法，尤其是低温SCR脱硝技术具有非常重要的应用前景和研究意义。研究表明VPO/TiO₂催化剂具有优异的低温SCR脱硝活性，本文通过DFT模拟NH₃和NO在V₂O₅和(VO)₂P₂O₇表面的吸附，对VPO催化剂的反应机理进行了微观层面上的研究。研究表明NH₃在V₄P₄O₂₂H₁₄团簇表面的Br?nsted酸和Lewis酸都发生稳定的化学吸附，在Br?nsted酸位点吸附更稳定，并且NH₃在催化剂表面吸附效果佳是因为N的2p轨道和O的2p、V的3d电子轨道能发生了杂化。NO在V₄P_...     

不同制备方法对铝基催化剂臭氧催化氧化的效果研究

为改善混合法制备催化剂催化效率低以及浸渍法制备过程中能耗大、耗时长、成本高的问题,以混合法为基础,研究不同活性组分负载方案,并在最佳的负载方案下探究了过量浸渍法、等体积浸渍法和混合法制备的催化剂催化臭氧氧化处理石化二级出水的效果,并分析了这3种方法制备催化剂的晶型结构、比表面积、孔径和孔体积. 结果表明:①混合法负载单活性组分的催化剂在催化臭氧氧化处理石化二级出水时,Mn/Al₂O₃催化剂表现出较高的催化活性,但出水不能满足《石油化学工业污染物排放标准》(GB 31571—2015)标准中规定的排放限值;负载双活性组分的催化剂中,Mn-Cu/Al₂O₃催化剂对石化二级出水催化臭氧氧化的去除效果较好,TOC、COD和UV₂₅₄去除率分别达34.54%、49.53%和56.81%,荧光类物质中类腐殖质的去除率也达到72.34%,出水满足GB 31571—2015标准限值. ②X-射线粉末衍射仪(XRD)和比表面积分析仪(BET)的结果表明,混合法、过量浸渍法和等体积浸渍法3种方法制备的同组分催化剂均具有γ-Al₂O₃的晶型结构,吸附等温线均属于Ⅳ型等温线,吸附量最大的为过量浸渍法,达到326.37 cm3/g. ③在催化臭氧氧化石化二级出水试验中,催化活性较高的是浸渍法,混合法稍次之,但处理后出水均可满足GB 31571—2015标准限值;3种方法制备的催化剂金属离子溶出量范围均为8.74~10.15 μg/L,远低于《城镇污水处理厂污染物排放标准》(GB 18918—2002)标准中规定的排放限值. 研究显示,混合法制备催化剂在深度处理石化废水时,出水可达标排放,而混合法制备催化剂工艺简单,成本低于浸渍法. 因此,混合法在满足实际需求时,有望代替浸渍法制备臭氧催化剂.      

V2O5/TiO2催化剂中毒机理的试验研究

选择性催化还原(SCR)催化剂是SCR烟气脱硝技术的核心,是整个SCR系统脱硝效率和经济性的决定因素.本文工作的主要研究思路是以钒钛SCR催化剂为研究对象,研究了H2O和SO2,以及相同含量下K、Na、Ca、Pb的氧化物对钒钛催化剂NO转化率的影响.H2O的存在会抑制V2O5/TiO2催化剂脱硝活性,而SO2在一定程度上促进(V2O5/TiO2)催化剂的SCR脱硝反应,提高NO转化率;碱金属K对钒钛催化剂的钝化作用都是最强,K2O和Na2O的掺入会抑制钒钛催化剂上V2O5的还原能力,而CaO和PbO的掺入对钒钛催化剂上V2O5的还原能力影响较小.     

Promotional effect of Si-doped V2O5/TiO2 for selective catalytic reduction of NOx by NH3

TiO2 supports doped with different amounts of Si were prepared by a sol-gel method, and 1 wt% vanadia (V2O5) loaded on Si-doped TiO2 was obtained by an impregnation method. The mole ratio of Si/Ti was 0.2, NOx conversion exceeds 94% at 300℃ and GHSV of 41,324 hr-1 , which is about 20% higher than pure V2O5/TiO2 . The catalysts were characterized by XRD, BET, TEM, FT-IR, NH3-TPD, XPS, H2-TPR, Raman and in situ DRIFTS. The results of FT-IR and XPS indicated that Si was doped into the TiO2 lattice successfully and a solid solution was obtained. V2O5 active component could be dispersed well on the support with the increasing of surface area of the catalyst, which was confirmed by Raman and XRD results. Above all, the numbers of acid sites (especially the Br nsted-acid) and oxidation properties were enhanced for Si-doped V2O5/TiO2 catalysts, which improved the deNOx catalytic activity.     

Effect of Ce doping of TiO2 support on NH3-SCR activity over V2O5-WO3/CeO2-TiO2 catalyst

CeO2–TiO2composite supports with different Ce/Ti molar ratios were prepared by a homogeneous precipitation method, and V2O5–WO3/CeO2–TiO2catalysts for the selective catalytic reduction（SCR） of NOx with NH3 were prepared by an incipient-wetness impregnation method. These catalysts were characterized by means of BET, XRD, UV–Vis,Raman and XPS techniques. The results showed that the catalytic activity of V2O5–WO3/TiO2 was greatly enhanced by Ce doping（molar ratio of Ce/Ti = 1/10） in the TiO2 support.The catalysts that were predominantly anatase TiO2 showed better catalytic performance than the catalysts that were predominantly fluorite CeO2. The Ce additive could enhance the surface adsorbed oxygen and accelerate the SCR reaction. The effects of O2 concentration, ratio of NH3/NO, space velocity and SO2 on the catalytic activity were also investigated. The presence of oxygen played an important role in NO reduction. The optimal ratio of NH3/NO was 1/1 and the catalyst had good resistance to SO2 poisoning.     

富氧条件下SnO2/Al2O3催化剂上丙烯选择性还原NOx的研究

考察了分别用浸渍法、共沉淀法和溶胶-凝胶法制备的SnO₂/Al₂O₃催化剂上丙烯选择性还原NO_x的催化活性,发现制备方法与Sn的负载量对其活性有重要影响.溶胶-凝胶法制备的SnO₂/Al₂O₃催化剂活性最高,Sn的最佳负载量为5%.与浸渍法和共沉淀法制备的5%SnO₂/Al₂O₃催化剂相比,溶胶-凝胶法制备的5%SnO₂/Al₂O₃催化剂受水蒸汽的抑制作用较弱,并且在水和SO₂共存的条件下活性最高.此外,反应气中丙烯及氧气浓度的增加有利于NO_x转化率的提高.     

Mn/TiO2和Mn-Ce/TiO2低温脱硝催化剂的抗硫性研究

在低温选择性催化还原(SCR)反应条件下考察了烟气残余SO2对Mn/TiO2和Mn-Ce/TiO2催化剂选择性催化还原活性的影响,同时对SO2的影响机理进行了探讨.结果发现,Mn/TiO2催化剂在SO2反应气氛中失活很快,硫铵盐的沉积和活性组分的硫酸化是催化剂失活的重要原因;Ce的加入可以有效地抑制催化剂活性组分的硫酸化,同时还能降低硫酸盐在催化剂表面的稳定性,从而可以提高催化剂的抗硫性.     

Effect of MoO3 on vanadium based catalysts for the selective catalytic reduction of NOx with NH3 at low temperature

The selective catalytic reduction(SCR) activities of the MoO_3 doped V/WTi catalysts prepared by the incipient wetness impregnation method at low temperature were investigated.The results showed that the addition of MoO_3 could enhance the NO_ xconversion at low temperature and the best SCR activity was obtained when the dosage of MoO_3 reached5 wt.%. The NH3-TPD and DRIFTS experiments indicated that the addition of MoO_3 changed the type and number of acid sites on the surface of catalysts and reaction activities of acid sites were altered at the same time. The redox capacity and amount of active oxygen species got improved for V3Mo5/WTi catalyst, which could be confirmed by the H_2-TPR and transient response experiments. Water vapor inhibited the NO_xconversion at low temperature. Deposition of ammonium sulfate or bisulfate might be main reason for the loss of catalytic activity in the presence of SO_2 at low temperature. Choosing the suitable NH_3/NO ratio and elevation of reaction temperature both could weaken the influence of SO_2 on the SCR activity of the V3Mo5/WTi catalyst. Thermal treatment of the deactivated catalyst at350°C could get the low temperature activity recovered. The decrease of GHSV improved the de NO_x efficiency at low temperature and we speculated that the rational technological process and operation parameters could contribute to the application of this kind of catalysts in real industrial environment.     

以堇青石蜂窝陶瓷为载体的新型钒氧化物脱氮催化剂研究

以TiO₂/Al₂O₃/堇青石蜂窝陶瓷为载体,以V₂O₅-MoO₃-WO₃为活性组分,用于氨法选择性催化还原烟气中NO的新型催化剂,并对该催化剂的活性性能和微观结构进行了评价和表征.同时,将该催化剂的活性性能与其它几种活性组分相同但载体、制备方法、结构不同的催化剂进行了对比.对比结果表明,该新型催化剂能取得最好的选择性催化还原氮氧化物催化性能BET、FT IR、XPS表征实验结果表明,其高催化活性得益于大比表面积及大孔体积,而TiO₂/Al₂O₃/堇青石蜂窝陶瓷载体及其制备方法对获得好的催化剂构型起了至关重要的作用.     

Activity and hydrothermal stability of CeO2–ZrO2–WO3 for the selective catalytic reduction of NOx with NH3

A series of CeO_2–ZrO_2–WO_3(CZW)catalysts prepared by a hydrothermal synthesis method showed excellent catalytic activity for selective catalytic reduction(SCR)of NO with NH_3 over a wide temperature of 150–550°C.The effect of hydrothermal treatment of CZW catalysts on SCR activity was investigated in the presence of 10% H_2O.The fresh catalyst showed above 90% NO_x conversion at 201–459°C,which is applicable to diesel exhaust NO_x purification(200–440°C).The SCR activity results indicated that hydrothermal aging decreased the SCR activity of CZW at low temperatures(below 300°C),while the activity was notably enhanced at high temperature(above 450°C).The aged CZW catalyst(hydrothermal aging at 700°C for 8 hr)showed almost 80% NO_x conversion at 229–550°C,while the V_2O_5–WO_3/TiO_2 catalyst presented above 80% NO_x conversion at 308–370°C.The effect of structural changes,acidity,and redox properties of CZW on the SCR activity was investigated.The results indicated that the excellent hydrothermal stability of CZW was mainly due to the CeO_2–ZrO_2 solid solution,amorphous WO_3 phase and optimal acidity.In addition,the formation of WO_3 clusters increased in size as the hydrothermal aging temperature increased,resulting in the collapse of structure,which could further affect the acidity and redox properties.     

Effects of synthesis methods on catalytic activities of CoOx–TiO2 for low-temperature NH3-SCR of NO

A series of cobalt doped TiO_2(Co-TiO_2) and Co Oxloaded TiO_2(Co/TiO_2) catalysts prepared by sol–gel and impregnation methods respectively were investigated on selective catalytic reduction with NH_3(NH_3-SCR) of NO. It was found that Co-TiO_2 catalyst showed more preferable catalytic activity at low temperature range. From characterization results of XRD,TEM, Raman and FT-IR, Co species were proved to be doped into TiO_2 lattice by replaced Ti atoms. After being characterized and analyzed by NH_3-TPD, PL, XPS, EPR and DRIFTS, it was found that the better NH_3-SCR activities of Co-TiO_2 catalysts, compared with Co/TiO_2 catalyst, were ascribed to the formation of more oxygen vacancies which further promoted the production of more superoxide ions(O-2). The superoxide ions were crucial for the formation of low temperature SCR reaction intermediates(NO-3) by reacting with adsorbed NO molecule. Therefore, these aspects were responsible for the higher low temperature NH_3-SCR activity of Co-TiO_2 catalysts.     

SO2对Mn-Cu-Ce/TiO2低温选择催化还原NO的影响

研究了SO2对Mn-Cu-Ce/TiO2选择催化还原 NO 的影响,并采用傅立叶变换红外光谱、x射线衍射光谱及暂态响应技术对Mn-Cu-Ce/TiO2催化剂的SO2中毒机理进行了探讨.结果表明,SO2 可强吸附在Mn-Cu-Ce/TiO2表面的 CuO 活性位上.并生成 CuSO4,由于 CuSO4 在低温时对SCR 反应有抑制作用,因而,催化剂的活性下降;暂态响应实验结果表明,Mn-Cu-Ce/TiO2催化剂上的SCR反应主要遵循 Langmuir-Hinshelwood机理.通过对催化剂进行硫酸化或 NO 预吸附,可以消除SO2对 Mn-Cu-Ce/TiO2的毒害作用.