用CuO/A12O3/堇青石催化剂选择性催化还原脱硝的实验和动力学研究

The CuO/γ-Al2O3/cordierite catalyst, after being sulfated by sulfur dioxide (SO2) at 673 K, exhibits high activities for selective catalytic reduction (SCR) of nitrogen oxide (NO) with ammonia (NH3) at 573-723 K. The intrinsic kinetics of SCR of NO with NH3 over CuO/γ-Al2O3/cordierite catalyst has been measured in a fixed-bed reactor in the absence of internal and external diffusions. The experimental results show that the reaction rate can be quantified by a first-order expression with activation energy of 94.01 kJ•mol1 and the corresponding pre-exponential factor of 3.39×108 cm3•g1•s1 when NH3 is excessive. However, when NH3 is not enough, an Eley-Rideal kinetic model based on experimental data is derived with Ea of 105.79 kJ•mol1, the corresponding A of 2.94×109 cm3•g1•s1, heat of adsorption ΔHads of 87.90 kJ•mol1 and the corresponding Aads of 9.24 cm3•mol1. The intrinsic kinetic model obtained was incorporated in a 3D mathematical model of monolithic reactor, and the agreement of the prediction with experimental data indicates that the present kinetic model is adequate for the reactor design and engineering scale-up.     

Mn-Fe-Ce/TiO2低温NH3选择性催化还原NO

采用浸渍法制备了MnO2-Fe2O3-CeO2/TiO2催化剂用于低温NH3选择性催化还原烟气中NO,考察了Mn, Fe, Ce含量及焙烧温度对NH3选择性催化还原NO的活性和抗水性能的影响. 在气体体积空速(GHSV)=24000 h-1, NH3/NO=0.8(j), 350℃煅烧和烟气含3%(j) O2的条件下,该系列催化剂的脱硝活性为MnO2-Fe2O3-CeO2/TiO2>MnO2- Fe2O3/TiO2>MnO2/TiO2,且在200℃时MnO2(10)-Fe2O3(5)-CeO2(5)/TiO2的脱硝率为95%. 对含10%(j)水蒸汽的烟气,MnO2(10)-Fe2O3(5)-CeO2(5)/TiO2的脱硝活性维持在87%;在10%(j)水蒸汽和100′10-6 SO2共存条件下,短时间内脱硝活性维持在55%.     

金属基分子筛型NH3选择性催化还原氮氧化物催化剂的研究进展

氨气选择性催化还原(NH3-SCR)消除氮氧化物(NOx)以其高效、低成本的优势成为目前最具潜力和最广泛应用的固定源脱硝技术.传统的NH3-SCR以V2O5/WOx-TiO2为催化剂,但该类催化剂水热稳定性差,易中毒且其本身就具有毒性,因此开发金属基分子筛催化剂是当前的研究热点之一.本文介绍了分子筛型NH3-SCR催化剂的研究进展,总结了不同金属负载分子筛对选择性催化还原的影响及其反应机理,探讨了催化剂失活的影响因素.     

Activity Enhancement of Bimetallic Rh-Ag/Al2O3 Catalysts for Selective Catalytic Reduction of NO by C3H6

The catalytic performance of bimetallic rhodium–silver clusters for the selective catalytic reduction of NO by propylene has been examined over 1%(Rh-Ag)/A₂O₃ catalysts of variable Ag content. It was found that substitution of small amounts of Rh by Ag results in a significant increase of the catalytic activity, which goes through a maximum for catalysts with metal compositions of ca. 95%Rh-5%Ag. This behaviour is tentatively attributed to the formation of rhodium-rich phase alloys, which may stabilize Rh in its reduced state at reaction conditions.     

Catalytic reduction of N2O with CH4 and C3H6 over Ag–Rh/Al2O3 bimetallic catalyst in the presence of oxygen

A study of nitrous oxide (N₂O) reduction with methane (CH₄) and propene (C₃H₆) in the presence of oxygen (5%) over Ag/Al₂O₃, Rh/Al₂O₃ and Ag–Rh/Al₂O₃ catalysts, with Ag and Rh loadings of 5 wt% and 0.05 wt% respectively, has been performed. From the results, it was observed that the Ag–Rh bimetallic catalyst was the most active for both nitrous oxide removal (more than 95%) and hydrocarbon oxidation. This high activity seems to be connected with a synergistic effect between Ag and Rh. The findings from X‐ray diffraction and X‐ray photoelectron spectroscopy studies showed also, that there were no strong interactions (eg alloying) between Ag and Rh. Copyright © 2005 Society of Chemical Industry     

Fe2O3/AC催化剂的低温选择性催化还原脱硝性能

以活性焦(AC)为载体、Fe2O3为活性组分,采用等体积浸渍法制备Fe2O3/AC催化剂,研究了Fe含量对Fe2O3/AC催化剂低温脱硝性能的影响. 结果表明,当Fe负载量为6wt%时能获得比其它负载量更佳的NOx转化率,尤其在240℃时NOx转化率达93.9%,当分别有120?10?6(vol) SO2和3.5vol H2O存在时,脱硝率分别稳定在约86%和74%;催化剂孔径≤4 nm,随Fe负载量增加,孔径呈增大趋势;催化剂较稳定;Fe主要以γ-Fe2O3分散在催化剂表面,负载适量Fe2O3使表面吸附氧Oβ和Fe3+增多,为催化剂提供更多活性位,提高了Fe2O3/AC催化剂的低温选择性催化还原脱硝活性.     

H-USY负载MnOx催化剂上CH4选择催化还原NOx性能的研究

采用高比表面积、抗硫、抗湿的新型USY分子筛为载体制备MnOx催化剂,考察了以CH4为还原剂,在不同Mn含量MnOx催化剂上,选择性催化还原NOx的性能和有关影响因素.研究表明:5%(wt.)的Mn/H-USY具有最高的NO选择性还原活性,在500℃时NOx达最大转化率20.8%;分段填装Mn/H-USY和Ni/H-USY催化剂可显著拓宽活性温度范围,促进NO转化率(最高转化率可达24.4%),降低N2O生成量.本实验中使用傅立叶红外分析仪进行在线检测反应物与产物浓度.     

Ce改性Fe2O3/AC催化剂低温SCR脱硝性能

以活性焦(AC)为载体、Fe和Ce为活性组分,采用等体积浸渍法制备了Fe2O3/AC和Ce?Fe2O3/AC催化剂,研究了Fe含量及Ce掺杂对Fe2O3/AC催化剂低温脱硝性能的影响,并对催化剂进行了表征. 结果表明,当Fe负载量为6wt%时,Fe2O3/AC催化剂的NOx转化率最高,240℃下达93.9%. 掺杂Ce后Ce?Fe2O3/AC催化剂的催化效率明显提高,当质量比Ce:Fe=0.5:6时,NOx转化率较高,120~200℃下NOx转化率比负载6wt% Fe的催化剂提高了5%?20%,且抗硫性能较好,240℃下通入100?10?6(vol) SO2,NOx转化率稳定在94.1%. 掺杂少量Ce可使γ-Fe2O3均匀分散在催化剂表面,且表面吸附氧Oα比例增大,催化剂的还原性增强,促进了选择性催化还原反应进行.     

V2O5/AC催化剂吸附NH3及其选择性还原脱硝活性

在不同活性焦(Activated Coke, AC)载体上以等体积浸渍法负载V2O5,制备出一系列V2O5/AC催化剂. 通过NH3暂态响应实验和NH3穿透时间实验考察了在200℃下V2O5/AC的表面积、灰分、表面官能团和V2O5对NH3的吸附量及NO的选择性催化还原活性的影响. 结果表明,对于载体未经硝酸处理的催化剂,NH3的吸附位主要是V2O5(参与脱硝反应的NH3的吸附量与催化剂上V2O5负载量的比值为1:5),活性焦及其中的灰分对NH3的吸附量很小;硝酸处理在活性焦表面引入的含氧和含氮酸性官能团对参与脱硝反应的NH3的吸附量是V2O5上吸附量的1.3倍,这些官能团不影响V2O5对NH3的吸附;活性焦上吸附的NH3的脱硝活性很低,但可迁移至V2O5上参与脱硝.     

Bi2O3电极的制备及其选择性氧化苯甲醇性能研究

采用滴凃法和电沉积法制备了Bi2O3薄膜电极,运用场发射扫描电子显微镜和X射线衍射仪对其进行了表征。在水相中以苯甲醇选择性氧化合成苯甲醛为模型反应,研究Bi2O3薄膜的催化性能。其中电沉积法制备的Bi2O3薄膜电极在水相溶液中表现出优异的电催化选择性氧化性能,苯甲醇的转化率最高,并且在外加偏压为2 V时达到了最高的苯甲醛选择性和苯甲醛收率。     

V2O5-MoO3/TiO2 催化剂的NOx选择性催化还原及SO2氧化活性

采用浸渍法以TiO₂为载体制备V₂O₅-MoO₃/TiO₂ 选择性催化还原催化剂,研究V₂O₅和MoO₃负载量对于催化剂选择性催化还原反应及SO₂氧化活性的影响,并考察氧含量、氨氮物质的量比和反应空速对3%V₂O₅-6%MoO₃/TiO₂催化剂选择性催化还原脱硝活性的影响。结果表明,随着催化剂中V₂O₅负载质量分数增加,V₂O₅-MoO₃/TiO₂ 催化剂的选择性催化还原活性和SO₂氧化活性均呈上升趋势。MoO₃的负载对催化剂的SO₂氧化活性有明显抑制作用。MoO₃负载质量分数超过9%,制备的催化剂既保持较高的低温选择性催化还原活性,又使选择性催化还原反应中的SO₂转化率小于1%。     

LaCoO3在含氧气氛下对CO还原SO2的催化性能

LaCoO3为CO还原SO2的催化剂,考察了催化剂用量、反应温度的影响以及混合催化剂对于CO还原SO2的催化作用。证实了催化活性相为La2O2S和CoS2相,并且通过XRD谱图的对比,初步探讨了催化剂的失活原因,以及O2对CO还原SO2反应和催化剂的影响。     

Monitoring Aging and Deactivation of Emission Abatement Catalysts for Selective Catalytic Reduction of NOx

Titania/vanadia, zeolite, and noble metal catalysts are utilized for selective catalytic reduction (SCR) of NO _x using ammonia as the reductant in different temperature ranges. Studies of aging have been carried out to probe deactivation rates and mechanisms. Periodic laboratory testing of samples of NO _x reduction catalysts from multi-layer reactors, such as those utilized at electric power plants, allows prediction of catalyst life-times. Testing has been carried out under protocol conditions with monolith, plate-type, and pelleted catalysts so that relative NO reduction rates can be compared, with or without the presence of SO₂. The catalysts were analyzed by surface analysis techniques, including electron microscopy and X-ray photoelectron spectroscopy, to probe surface morphology, loss of active components, presence of poisons, and blocking of pores and active sites by ammonium bisulfate to determine the dominant mode(s) of gradual deactivation.     

Catalytic Conversion of N2O to N2 over Metal-Based Catalysts in the Presence of Hydrocarbons and Oxygen

The catalytic conversion of N₂O to N₂ in the presence or the absence of propene and oxygen was studied. The catalysts examined in this work were synthesized impregnating metals (Rh, Ru, Pd, Co, Cu, Fe, In) on different supports (Al₂O₃, SiO₂, TiO₂, ZrO₂ and calcined hydrotalcite MgAl₂(OH)₈·H₂O). The experimental results varied both with the type of the active site and with the type of the support. Rh and Ru impregnated on -alumina exhibited the highest activity. The performance of the above most promising catalysts was studied using various hydrocarbons (CH₄, C₃H₆, C₃H₈) as reducing agents. These experimental results showed that the type of reducing agent does not affect the reaction yield. The temperature where complete conversion of N₂O to N₂ was measured was independent of the reductant type. The activity of the most active catalysts was also measured in the presence of SO₂ and H₂O in the feed. A shift of the N₂O conversion versus temperature curve to higher temperatures was observed when SO₂ and H₂O were added, separately or simultaneously, to the feed. The inhibition caused by SO₂ was attributed to the formation of sulfates and that caused by water to the competitive chemisorption of H₂O and N₂O on the same active sites.     

Experimental and Modeling Study on de-NOx Characteristics of Selective Non-catalytic Reduction in O2/CO2 Atmosphere

An experimental study of thermal de-NOx using NH3 as reductant in O2/CO2 atmosphere with the effect of SO2 and different additives was performed in a drop tube furnace. Results show that the optimum te...     

采用蜂窝状筛网催化剂进行NH_3选择性催化还原NO的反应

采用蜂窝状筛网催化剂用于以NH3为还原剂选择性催化还原 (SCR)NO的反应。考察了TiO2 负载量、催化剂组分、模件的齿高、催化剂长度以及筛网目数等因素对其催化行为的影响。结果表明 :8gTiO2 可将62 0cm2 的筛网模件表面完全覆盖 ,此时催化活性最佳。V( 1) W ( 3 ) /TiO2 的蜂窝状筛网催化剂表面存在聚合的钒基物种。催化剂长度大于 5cm时 ,不存在进口效应。筛网目数小于 2 4目时 ,NO转化率随筛网目数的增加而增加     

Structure Characteristics and NO Selective Catalytic Reduction Property of Sn x Zr1-x O2 Solid Solution Catalysts

Novel catalysts, Sn_xZr_1-xO₂ solid solutions, for NO selective catalytic reduction:NO SCR) are reported. They have much higher activity and selectivity than SnO₂ and ZrO₂. Sn⁴⁺ is the main reductive sites as proved by TPR. The dilution of Sn sites by the coexisting Zr causes a suppression of propene combustion and consequently promoted the selective reduction of NO. The rutile structure might be beneficial to NO SCR.     

Selective CO oxidation over monolithic Au?MgO/Al2O3 catalysts

BACKGROUND: Selective CO oxidation was studied in a hydrogen‐rich environment over monolithic Au/MgO/Al₂O₃ catalysts at 50–150 °C. The wash‐coating of cordierite monoliths with colloidal Al₂O₃ was followed by wet impregnation of MgO; the subsequent deposition of Au was achieved using various methods. All catalysts were characterized using ICP and ESEM. RESULTS: Homogenous deposition‐precipitation was found to be the best Au loading method among those tested for monoliths. The CO conversion over 1%(w/w) Au/1.25%(w/w) MgO/Al₂O₃ was ca 80% at 90 °C. Increasing the Au content of the catalyst from 0.16 to 1.0%(w/w) increased CO conversion and shifted the required temperature to lower values. A similar trend was also observed for maximum CO conversion at increasing W/F_CO ratios. The addition of MgO was beneficial for CO conversion. CONCLUSION: Although CO conversion of ca 80% was lower than that achieved with particulate catalysts, it is high enough as a starting point for further improvement considering the superiority of monolithic supports for practical applications. Copyright © 2011 Society of Chemical Industry     

金属氧化物催化剂上H_2S选择性催化氧化研究进展

选择性催化氧化法作为一种新型的脱除H_2S尾气技术,重点是开发具有高活性和多种性能特点的催化剂形成系列产品。总结了金属氧化物催化剂上H_2S选择性催化氧化反应的研究进展。重点介绍了不同载体、活性组分和助剂对催化剂活性的影响;阐述了H_2S选择性催化氧化的反应机理和失活机理,并对金属氧化物催化剂的未来发展方向上进行了展望。     

Fe-Al2O3金属陶瓷选择性还原制备工艺研究

本文以Fe₂O₃、l₂O₃粉体为原料,在室温进行高能球磨,然后热压烧结制备（Fe,Al）₂O₃单相固溶体。对单相固溶体在H₂气氛下进行热处理,使固溶的Fe选择性还原析出为分散于Al₂O_基体中的金属颗粒。利用XRD、TEM分析还原产物,研究还原产物的物相,并观察还原后铁在氧化铝基体中的分布情况。