负载顺序对浸渍法制备Mn-Ce/TiO2催化剂性能的影响

为了探究负载顺序对Mn-Ce/TiO₂催化剂氨选择性催化还原NO的影响,文章采用浸渍法制备了Mn-Ce/TiO₂低温SCR催化剂,并通过BET、SEM、XRD、FT-IR、H₂-TPR和NH₃-TPD对不同负载顺序的催化剂样品进行了表征,分析影响SCR活性的原因。结果表明,同时负载锰铈的催化剂脱硝活性最高,在反应温度为150 ℃的条件下,Mn-Ce/TiO₂催化剂的脱硝效率达到100%。BET和SEM结果表明,Mn、Ce同时负载催化剂的比表面积最大,且催化剂表面更加平整光滑,有利于催化活性;XRD结果表明,与同时负载锰铈的催化剂相比,锰铈分步负载时,其锰氧化物不够分散,都会影响催化剂中活性组分的晶体结构,从而影响催化剂性能。从H₂-TPR、NH₃-TPD分析可知,与锰铈同时负载比较,锰铈分步负载时,催化剂还原峰向高温方向发生了偏移,且催化剂表面酸性位点变弱,抑制了对NH₃的吸附能力,不利于NO_x     

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NH_3...     

VPO/TiO2催化剂表面酸性位调控及低温NH3-SCR脱硝性能研究

采用HCl调控负载型钒磷氧(VPO/TiO₂)催化剂的表面酸性,用于研究VPO/TiO₂催化剂的NH₃-SCR脱硝性能.结果表明:在HCl/V物质的量比为3～5:1范围内,催化剂的脱硝活性最高,当反应温度达到200℃时脱硝效率接近100%.表征结果表明:HCl的添加能提高催化剂的结晶度,HCl的调控使得VPO/TiO₂催化剂的比表面积略有增加.同时,也使得VPO/TiO₂催化剂中活性组分V⁴⁺的量从38%逐渐升高至46%,提高了催化剂的氧化还原性能.此外,不同HCl/V物质的量比的催化剂中化学吸附氧的相对含量随着HCl加入量的增加而提高.吡啶红外测试结果显示:HCl能影响催化剂酸性位点,HCl/V物质的量比=5的催化剂Lewis酸含量最高,总酸量为0.84×10^-4mol/g.数据拟合进一步表明,所有VPO/TiO₂催化剂的低温脱硝活性均与弱Lewis酸量呈正相关(相关系数>0.9),与活性测试相吻合.     

Mn-Co/蜂窝陶瓷催化剂制备及催化臭氧化对苯二酚效能

为了提高金属催化剂的活性和使用寿命,以硝酸钴Co(NO3)2·6H2O和硝酸锰Mn(NO3)2作为前驱体,蜂窝陶瓷(ceramic honeycomb,CH)作为载体,采用涂覆法制备了4种不同质量比的Mn-Co/CH催化剂,通过XRD、N2-吸附/脱附、FESEM和XPS等方法分析了催化剂的结构,研究了催化剂的材料力学性能,建立了单独臭氧和催化臭氧化对苯二酚的反应动力学模型,考察了催化剂催化臭氧化的效能.结果表明,Mn1Co1/CH(Mn∶Co=1∶1)催化剂的晶相主要以Mn3O4和Co O为主,具有较大的比表面积、孔容和孔径,分别达到190 m~2·g~(-1)、0.25 cm3·g-1和4.8 nm;Mn1Co1/CH催化剂的催化活性最高,对苯二酚和COD的去除率分别达到78%和54%.Mn-Co/CH催化剂的抗压缩强度大(15.89~16.94 MPa).当添加叔丁醇时,对苯二酚去除率显著下降,·OH在Mn1Co1/CH催化臭氧化过程中起着重要的作用,催化臭氧化对苯二酚符合一级反应动力学模型.Mn-Co/CH催化剂用量少、催化效率高、使用寿命长,易于实现工业化.     

MnOx/TiO2-ZrO2催化剂的制备及低温催化还原NO的研究

采用共沉淀法制备了TiO2-ZrO2复合氧化物,以其为载体采用等体积浸渍法制备了不同负载量的MnOx/Ti02-Zr02催化剂.低温下以NH3为还原剂考察了催化剂选择性催化还原(SCR)NO的活性.借助N2吸附、XRD、热重-差示扫描量热法(TG-DSC)对催化剂进行微观表征和分析.结果表明,负载量为5%时,生成的MnO2高度分散,NO的转化率较高;负载量为10%和15%时,出现MnO2晶相,NO的转化率有所下降.120-240℃、体积空速为10000 h-1的条件下,3种负载量的催化剂上NO转化率均大于90%.     

V2O5-WO3/TiO2脱硝催化剂的制备及其性能

对选择性催化还原脱硝用催化剂V2O5-WO3/TiO2的制备工艺进行了实验研究.采用溶胶-凝胶法制得TiO2凝胶,对凝胶进行不同条件下的干燥和煅烧处理,然后通过浸渍法在TiO2上依次负载WO3和V2O5,最终得到V2O5-WO3/TiO2催化剂.结果表明,TiO2凝胶的处理温度对催化剂结构和脱除NO的性能有一定的影响,TiO2凝胶干燥温度为105 ℃时制得的催化剂活性较高,在实验条件下NO脱除率最高可达98.3%.     

超声波浸渍法制备V_2O_5-WO_3/TiO_2选择性催化还原脱硝催化剂

采用超声波浸渍法、传统浸渍法制备一系列V2O5-WO3/TiO2催化剂,对催化剂的反应活性进行考察。研究表明:与普通浸渍法相比,超声波浸渍法可以提高催化剂的脱硝效率,拓宽催化反应的温度窗口。超声波浸渍时间和超声波功率对催化剂的反应活性有较大影响。浸渍时间增加,催化剂脱硝效率也随之提高。超声波功率增加,催化剂的脱硝效率先提高后降低。在超声波频率28 kHz,超声波功率400 W,超声作用时间1.5 h,超声水粉比为100 mL H2O/10 g TiO2的条件下,制得的V2O5-WO3/TiO2脱硝催化剂脱硝效率接近100%。通过SEM对制备的催化剂进行表征,超声波浸渍法制备的催化剂的活性成分在载体上分散更加均匀。     

TiO2/活性炭负载光催化剂的制备与光催化性能

以粒状活性炭为载体,钛酸丁酯和乙醇为原料,用溶胶-凝胶法及浸渍法制备负载型TiO2光催化剂.通过加入不同分子量和质量的聚乙二醇降低催化剂表面TiO2的粒径,增大比表面积,提高TiO2/C光催化剂的吸附性和光催化活性.以XDA、SEM、TG-DTA、比表面积、亚甲蓝吸附值、钛的负载量及对亚甲蓝的光催化降解性能对催化剂样品进行了表征.结果表明加入1.0 g PEG2000所制备的TiO2/C前驱体经过450℃焙烧后,TiO2的平均晶粒尺寸为12.9 nm,其晶型为锐钛矿型,其比表面积为997.0m2·g-1,对亚甲蓝的吸附值比活性炭基体增加22.5%,100mg·L-1的亚甲蓝溶液用该催化剂在pH为1.0～9.25范围内,2.5 h的降解率达82.5%～96%.     

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。     

V-Mo/TiO2堇青石负载型脱硝催化剂的制备和性能

随着环境问题日益突出,锅炉烟气中氮氧化物(NO_x)的脱除成为亟待解决的问题。采用同步浸渍法制备了堇青石蜂窝负载型脱硝催化剂,研究了钒含量、温度、气时空速以及酸处理等对堇青石负载型脱硝催化剂脱硝效率的影响,同时采用BET、XRD等对催化剂进行物理化学表征。结果表明:负载型脱硝催化剂脱硝效率随着V₂O₅含量的增加逐渐变大,脱硝效率随着温度提高先增加后降低;在340℃时,负载型催化剂达到较好的脱硝效果,脱硝效率达到98%以上(气时空速为18000 h^-1);硫酸处理后的催化剂脱硝效率提高1～3百分点,而HCl处理后的催化剂脱硝效率降低4～8百分点;堇青石负载型催化剂负载率维持在25%左右,经过超声处理后的脱落率<10%。     

Fe2O3 particles as superior catalysts for low temperature selective catalytic reduction of NO with NH3

Fe203 particle catalysts were experimentally studied in the low temperature selective catalytic reduction （SCR） of NO with NH3. The effects of reaction temperature, oxygen concentration, [NH3]/[NO] molar ratio and residence time on SCR activity were studied. It was found that Fe203 catalysts had high activity for the SCR of NO with NH3 in a broad temperature range of 150-270℃, and more than 95% NO conversion was obtained at 180℃ when the molar ratio [NH3]/[NO] = 1, the residence time was 0.48 seconds and 02 volume fraction was 3%. In addition, the effect of SO2 on SCR catalytic activity was also investigated at the temperature of 180℃. The results showed that deactivation of the Fe2O3 particles occurred due to the presence of SO2 and the NO conversion decreased from 99.2% to 58% in 240 min, since SO2 gradually decreased the catalytic activity of the catalysts. In addition, X-ray diffraction, Thermogravimetric analysis and Fourier transform infrared spectroscopy were used to characterize the fresh and deactivated Fe2O3 catalysts. The results showed that the deactivation caused by SO2 was due to the formation of metal sulfates and ammonium sulfates on the catalyst surface during the de-NO reaction, which could cause pore plugging and result in suppression of the catalytic activity.     

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.     

Ultrasound-assistant preparation of Cu-SAPO-34 nanocatalyst for selective catalytic reduction of NO by NH3

The influence of the various preparation methods of Cu-SAPO-34 nanocatalysts on the selective catalytic reduction of NO with NH₃ under excess oxygen was studied. Cu-SAPO-34 nanocatalysts were prepared by using four techniques: conventional impregnation (IM), ultrasound-enhanced impregnation (UIM), conventional deposition precipitation (DP) using NaOH and homogeneous deposition precipitation (HDP) using urea. These catalysts were characterized in detail by various techniques such as N₂-sorption, XRD, TEM, H₂-TPR, NH₃-TPD and XPS to understand the catalyst structure, the nature and the dispersed state of the copper species, and the acid sites for NH₃ adsorption. All of the nanocatalysts showed high activities for NO removal. However, the activities were different and followed the sequence of Cu-SAPO-34 (UIM) > Cu-SAPO-34 (HDP) > Cu-SAPO-34 (IM) > Cu-SAPO-34 (DP). Based on the obtained results, it was concluded that the NO conversion on Cu-SAPO-34 nanocatalysts was mainly related to the high reducibility of the isolated Cu^2 + ions and CuO species, the number of the acid sites and the dispersion of CuO species on SAPO-34.     

Mn-CeOx/Ti-PILCs for selective catalytic reduction of NO with NH3 at low temperature

Titanium-pillared clays (Ti-PILCs) were obtained by different ways from TiCl₄, Ti(OC₃H₇)₄ and TiOSO₄, respectively. Mn-CeO_x/Ti-PILCs were then prepared and their activities of selective catalytic reduction (SCR) of NO with NH₃ at low-temperature were evaluated. Mn-CeO_x/Ti-PILCs were characterized by X-ray diffraction, N₂ adsorption, Fourier transform infrared spectroscopy, thermal analysis, temperature-programmed desorption of ammonia and H₂-temperature-programmed reduction. It was found that Ti-pillar tend to be helpful for the enlargement of surface area, pore volume, acidity and the enhancement of thermal stability for Mn-CeO_x/Ti-PILCs. Mn-CeO_x/Ti-PILCs catalysts were active for the SCR of NO. Among three resultant Mn-CeO_x/Ti-PILCs, the catalyst from TiOSO₄ showed the highest activity with 98% NO conversion at 220℃, it also exhibited good resistance to H₂O and SO₂ in flue gas. The catalyst from TiCl₄ exhibited the lowest activity due to the unsuccessful pillaring process.     

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.     

基于ZrO2/TiO2催化H2O2氧化低温脱硝的实验研究

以纳米TiO_2为载体,采用等体积浸渍法掺杂过渡金属氧化物ZrO_2进行改性,制备了一系列ZrO_2/TiO_2催化剂,以催化H_2O_2低温氧化NO脱硝,并采用X射线衍射(XRD)、H_2程序升温还原(H_2-TPR)、O_2程序升温氧化(O_2-TPO)、X射线光电子能谱(XPS)及电子顺磁共振(EPR)等表征分析探究了影响H_2O_2脱硝活性的因素.表征结果表明ZrO_2的负载量会影响催化剂中晶格氧的含量,晶格氧相对含量的增加有利于氧化还原反应中的电子传递,这是促进H_2O_2活化分解的关键.在微观表征的基础上,通过实验研究筛选获得了催化剂的最佳ZrO_2负载量,同时对比考察了非催化和纳米TiO_2催化作用下的H_2O_2氧化低温脱硝性能;针对获取的最优催化剂,进一步考察了不同烟气工况对催化剂活性的影响.实验结果表明,ZrO_2/TiO_2催化剂能有效促进H_2O_2的活化分解实现低温脱硝,且ZrO_2负载量为4%(质量分数)时,催化活性最高;在烟温为160℃、[H_2O_2]/[NO]物质的量比为2及空速为30000 h~(-1)时,NO转化率最高可达81%.     

Mn-Ce/TiO2低温SCR催化剂成型过程添加剂的影响

催化剂成型过程中添加剂的种类和添加量对成型后催化剂的机械强度、成型效果和催化性能有很大影响.本文研究了Mn-Ce/TiO₂催化剂制备过程中添加剂对催化剂的低温脱硝性能和机械性能的影响.结果表明,添加10%的拟薄水铝石作为黏结剂,可使催化剂具有较强的机械强度;添加2.5%的活性炭作为造孔剂,可以有效改善催化剂的孔结构.催化剂成型后脱硝性能下降,反应温度为90℃和120℃时,催化剂的NO_x转化率分别下降了15%和30%左右,当温度到达150℃及以上时,催化剂成型前后的脱硝性能基本一致.最后,通过BET、FT-IR、NH₃-TPD和H₂-TPR表征分析原因：成型后催化剂比表面积和孔容下降,催化剂的表面酸性位点和氧化还原能力下降都会影响催化剂的脱硝性能,所以催化剂成型后低温活性变差.     

高分散MnOx/SAPO-34催化剂的制备及其低温NH3选择性催化还原NO性能

采用改进的溶胶-凝胶法制备一系列MnO_x/SAPO-34催化剂,考察了各制备参数对催化剂的结构及其低温氨选择性催化还原(NH_3-SCR)脱硝性能的影响,并通过X射线衍射、N_2吸附-脱附、透射电镜、X射线光电子能谱、NH_3程序升温脱附等手段对催化剂进行表征.结果表明,当制备参数为n(乙醇)/n(Mn)=15,n(H_2O)/n(Mn)=20,n(柠檬酸)/n(Mn)=1,Mn负载量为15%(质量分数),催化剂焙烧温度为350℃时,制备的高分散15%-MnO_x/SAPO-34-350℃催化剂具有最佳的低温SCR活性,在空速为45000 h~(-1)的条件下,且反应温度在120～240℃范围时均保持90%以上的NO转化率和接近100%的N_2选择性.MnO_x纳米颗粒高度分散在SAPO-34载体表面,平均粒径约为5.46 nm,纳米颗粒的表面效应使得该催化剂具备较大的比表面积,暴露出大量的活性位点和高活性的MnO_2(110)晶面,同时,高Mn~(4+)比例和更多的化学吸附氧以及适宜的表面酸强度和酸量也是15%-MnO_x/SAPO-34-350℃催化剂呈现最佳低温SCR活性的重要原因.     

Effect of TiO2 calcination temperature on the photocatalytic oxidation of gaseous NH3

Carbon-modified titanium dioxide(TiO2) was prepared by a sol-gel method using tetrabutyl titanate as precursor, with calcination at various temperatures, and tested for the photocatalytic oxidation(PCO) of gaseous NH3 under visible and UV light. The test results showed that no samples had visible light activity, while the TiO2 calcined at 400℃ had the best UV light activity among the series of catalysts, and was even much better than the commercial catalyst P25. The catalysts were then characterized by X-ray diffractometry, Brunauer-Emmett-Teller adsorption analysis, Raman spectroscopy, thermogravimetry/differential scanning calorimetry coupled with mass spectrometry, ultraviolet-visible diffuse reflectance spectra, photoluminescence spectroscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy. It was shown that the carbon species residuals on the catalyst surfaces induced the visible light adsorption of the samples calcined in the low temperature range( 300℃). However, the surface acid sites played a determining role in the PCO of NH3 under visible and UV light over the series of catalysts. Although the samples calcined at low temperatures had very high SSA, good crystallinity, strong visible light absorption and also low PL emission intensity, they showed very low PCO activity due to their very low number of acid sites for NH3 adsorption and activation. The TiO2 sample calcined at 400℃ contained the highest number of acid sites among the series of catalysts, therefore showing the highest performance for the PCO of NH3 under UV light.