La_(1-x)Ce_xCu_yMn_(1-y)O_3/HZSM-5催化剂低温去除柴油机碳烟和NO_x

为实现对柴油机碳烟和NOx的低温同步去除,采用柠檬酸络合法制备分子筛负载钙钛矿型金属复合氧化物催化剂,应用X衍射分析仪(XRD)和电镜扫描仪(SEM)对催化剂性能进行表征,并在微型固定床反应器中对催化剂低温去除碳烟和NOx进行活性评价。利用程序升温反应(TPR)技术,进行催化剂活性评价、柴油机负荷和排放等特性实验。结果表明,A位用适量Ce部分取代La,B位用适量Cu部分取代Mn,可使碳颗粒燃烧温度降低,CO2选择性好,NOx转化率升高。La0.4Ce0.6Cu0.2Mn0.8O3/HZSM-5催化剂的最大NOx转化率为81.0%,Ti、Tm和Tf分别为250、350和475℃,表明该催化剂具有较好的催化活性,能在低温条件下去除碳烟和NOx。     

La—K—Co—Mn-O钙钛矿型复合氧化物同时去除碳颗粒和NOx的性能

采用柠檬酸络合燃烧法合成制备了La1-xKxCo0.5Mn0.5O3(x为K+取代量,x=0、0.1、0.2、0.3、0.4、0.5)系列钙钛矿型复合金属氧化物催化剂,以X射线衍射、红外光谱和比表面积等手段对该催化剂进行表征,以常压固定床微型反应器程序升温氧化还原反应技术评价该催化剂同时去除模拟柴油机尾气中炭黑颗粒(表征柴油机尾气中的碳颗粒)和NOX的催化性能.结果表明,K+部分取代LaCo0.5Mn0.5O3中的La3+后,催化剂催化性能得到明显改善,炭黑颗粒的起燃温度(Tig)、峰值温度(Tm)和燃尽温度(Tf)均降低,NOX的转化率提高,最高为16.6%;La0.6K0.4Co0.5Mn0.5O3具有最佳的催化性能,炭黑颗粒的Tig、Tm和Tf分别为305、350、379 ℃,炭黑颗粒燃烧产物中CO2的体积分数为98.8%,NOX转化率为15.5%.     

负载型Mn-Ce／TiO2催化剂的制备及其低温脱硝活性

以成型TiO2作为载体，通过浸渍法制备了Mn-Ce／TiO2低温SCR催化剂，并系统研究了制备方法、煅烧条件、活性组分担载量、Mn含量等参数对催化剂催化还原NO性能的影响。结果表明，煅烧温度的升高会促使活性组分结晶度的提高，从而引起催化活性的降低，在500℃和600℃下所得Mn-Ce／TiO2催化剂活性组分为无定型态，表现出较高的脱硝活性。活性组分担载量的增加有利于催化活性的提高。Mn含量对Mn-Ce／TiO2催化剂的活性有较大影响，当Mn／（Mn＋Ce）摩尔比为40％和85％时，催化剂活性最高。     

MnxCe1-xO2／γ-Al2O3催化剂的制备及其催化甲苯的燃烧性能

以γ-Al2O3为载体，以MnxCe1-xO2为催化活性组分，采用浸渍法制备了一系列负载型MnxCe1-xO2／γ-Al2O3催化剂（x=0、0．2、0．4、0．6、0．8、0．9、1），在固定床反应器中评价了催化剂对甲苯的催化燃烧性能。结果表明，MnxCe1-xO2／γ-Al2O3催化剂的催化活性与催化剂的焙烧温度、活性组分MnxCe1-xO2的负载量以及Mn、Ce摩尔比有显著关系，其中焙烧温度550℃、负载量为20％、Mn、Ce摩尔比为4：1时，即MnxCe1-xO2／γ-Al2O3催化剂对甲苯的催化性能最佳，反应温度为180℃时，甲苯的转化率达到95％。并在连续100h的稳定性操作后，催化剂的活性基本无变化。采用XRD、BET以及SEM等分析测试手段对催化剂的结构以及表面进行了表征。     

负载型催化剂联合低温等离子体去除甲苯

为了解负载型催化剂联合低温等离子体对甲苯去除效率的影响,考察了5A分子筛、γ-Al_2O_3和混合载体负载Mn、Mn/Cu和Mn/Cu/Ce金属氧化物对甲苯去除率及碳平衡和CO_2选择性的影响效果,并对催化剂进行了BET、SEM、XRD和FT-IR表征研究。结果表明,相同载体条件下,对甲苯的去除效率依次为MnO_x/CuO_xMnO_x/CuO_x/CeO_xMnO_x无负载,其中负载型催化剂MnO_x/CuO_x/γ-Al_2O_3稳定后对甲苯的去除效率高达80%。无负载条件下,3种载体对碳平衡和CO_2选择性大小依次为γ-Al_2O_3混合载体分子筛。催化剂表征可知,MnO_x/CuO_x活性组分在催化剂表面高度分散,保证了催化剂的高活性;FT-IR红外光谱发现,无负载的γ-Al_2O_3载体反应后其表面活性基团—OH明显减少,而负载型催化剂反应前后其表面的—OH基团变化不大。     

基于碳烟颗粒催化氧化的三维有序大孔催化剂制备及性能

三维有序大孔钴锰尖晶石催化剂(3DOMCoMn_2O_4)以及三维有序大孔镧、铈掺杂的钴锰尖晶石催化剂(3DOMR_xCo_(1-x)Mn_2O_4(R=Ce, La))由胶晶模板法成功合成。通过对所得的催化剂在NO_x协助下的碳烟催化氧化活性评价,优化了Ce/Co和La/Co的配比。此外,还对目标催化剂进行了XRD、N2吸脱附、Raman、H_2-TPR、SEM、XPS等表征。结果表明:3DOM结构增强了催化剂与碳烟颗粒之间的接触,对碳烟氧化等"固-固-气"非均相催化反应具有明显的提升作用。此外,铈和镧的掺杂增大了活性氧物种的浓度,从而增强了钴锰尖晶石催化剂的催化氧化能力。在松散接触工况下,3DOM Ce_(0.9)Co_(0.1)Mn_2O_4的Tig(起燃温度)和T_m(CO_2出口浓度最大时的温度)分别为285℃和377℃,3DOM La_(0.3)Co_(0.7)Mn_2O_4的T_(ig)和T_m分别为287℃和376℃。     

负载型Mn-Ce/TiO2催化剂的制备及其低温脱硝活性简

以成型TiO₂作为载体，通过浸渍法制备了Mn-Ce/TiO₂低温SCR催化剂，并系统研究了制备方法、煅烧条件、活性组分担载量、Mn含量等参数对催化剂催化还原NO性能的影响。结果表明，煅烧温度的升高会促使活性组分结晶度的提高，从而引起催化活性的降低，在500℃和600℃下所得Mn-Ce/TiO₂催化剂活性组分为无定型态，表现出较高的脱硝活性。活性组分担载量的增加有利于催化活性的提高。Mn含量对Mn-Ce/TiO₂催化剂的活性有较大影响，当Mn/（Mn+Ce）摩尔比为40%和85%时，催化剂活性最高。     

Ce掺杂改性对MnFe2O4低温选择性催化还原脱硝性能的影响研究

采用水热合成法制备了Ce掺杂MnFe2O4催化剂,用于低温选择性催化还原(SCR)脱硝.对催化剂晶型、脱硝性能和表面结构等进行分析,结果表明,Ce/(Fe+Mn)为0.5％(摩尔分数,下同)时催化剂表现出最优的SCR活性,80℃NO去除率可达100％;Ce/(Fe+Mn)分别为5.0％ 和10.0％ 时,催化剂80℃N...     

Mn、Ce掺杂改性γ-Al_2O_3催化剂对燃煤烟气Hg~0去除性能研究

以γ-Al_2O_3为掺杂,通过掺杂Mn、Ce活性物质制备复合催化剂去除模拟烟气中的Hg0,考察了Mn和Ce负载量、催化剂制备煅烧温度、反应温度以及模拟烟气中O_2和SO_2体积分数对于Hg0去除率的影响。结果表明,负载Mn、Ce活性组分后,复合催化剂对燃煤烟气Hg~0的去除率明显高于γ-Al_2O_3。当Mn、Ce负载量分别为0.10、0.02时(以Mn、Ce与Al的摩尔比计)时,制得的催化剂Mn0.10-Ce0.02/γ-Al_2O_3活性最好,催化剂最佳煅烧温度为400℃,最佳反应温度为150℃。常规燃煤烟气条件下的O_2体积分数能够满足Hg~0的有效氧化,烟气中的SO_2会严重抑制Hg~0的氧化。     

γ-Al_2O_3负载Mn基催化剂低温催化臭氧氧化NO

利用等体积浸渍法制备γ-Al_2O_3负载Mn基催化剂,考察了掺杂元素种类,掺杂元素与Mn元素摩尔比以及煅烧温度对NO低温(100℃)催化氧化活性的影响,并对催化剂在有SO_2或H_2O的烟气中的稳定性进行了探究。结果表明,掺杂元素为Ce,Ce/Mn=0.4,煅烧温度为500℃条件下制备的催化剂NO催化活性最佳,在NO体积浓度为500×10~(-6),臭氧浓度为20.9 mg·L~(-1),n(O_3)/n(NO)=0.2,反应温度为100℃,模拟烟气总流量为1.0 L·min~(-1),模拟烟气相对湿度为4%的条件下,NO的转化率最高可达70%。此外,还对催化剂在不同条件下的稳定性和活性恢复情况进行了探究。实验最终实现了在低O_3浓度条件下达到较高NO转化率的目的,为烟气脱硝提供了一种具有应用潜力的新技术。     

Catalytic performance of Ag/Al2O3-C2H5OH-Cu/Al2O3 system for the removal of NOx from diesel engine exhaust

The selective catalytic reduction (SCR) of NOx by C(2)H(5)OH was studied in excess oxygen over Ag/Al(2)O(3) catalysts with different Ag loadings at lab conditions. The 4% Ag/Al(2)O(3) has the highest activity for the C(2)H(5)OH-SCR of NOx with a drawback of simultaneously producing CO and unburned THC in effluent gases. An oxidation catalyst 10% Cu/Al(2)O(3) was directly placed after the Ag/Al(2)O(3) to remove CO and unburned THC. Washcoated honeycomb catalysts were prepared based on the 4% Ag/Al(2)O(3) and 10% Cu/Al(2)O(3) powders and tested for the C(2)H(5)OH-SCR of NOx on a diesel engine at the practical operating conditions. Compared with the Ag/Al(2)O(3) powder, the Ag/Al(2)O(3) washcoated honeycomb catalyst (SCR catalyst) has a similar activity for NOx reduction by C(2)H(5)OH and the drawback of increasing the CO and unburned THC emissions. Using the SCR+Oxi composite catalyst with the optimization of C(2)H(5)OH addition, the diesel engine completely meets EURO III emission standards.     

铈锆固溶体负载LaCoO3催化碳烟的性能和表征

用柠檬酸法制备了铈锆固溶体负载不同量LaCoO3的催化剂。用热重法测试了催化剂样品对碳烟的催化活性。采用程序升温还原法（H2-TPR）、BET、X-射线衍射仪（XRD）和X-射线光电子能谱仪（XPS）对催化剂进行了测试。结果表明,铈锆固溶体表面形成了稳定的LaCoO3钙钛矿相结构;负载量为30%LaCoO3的催化剂具有最高的催化活性,起燃温度降到530℃;催化剂的催化活性与催化剂还原峰强度以及催化剂表面氧物种OII的含量紧密相关。     

Mn的氧化价态对Mn／γ-Al2O3催化剂催化臭氧氧化气相低浓度甲苯的影响

采用共沉淀法，以Al2O3为载体制备Mn／γ-Al2O3和Mn—Ce／Mn／γ-Al2O3催化剂，并分别在N2气氛和O2气氛下焙烧。采用固定床连续流动反应器，研究所制备催化剂在室温条件下催化臭氧氧化甲苯的性能。通过XRD、XPS和FTIR等手段对催化剂的结构和组成进行表征。结果表明，Mn／Mn／γ-Al2O3催化剂具有良好的催化臭氧氧化甲苯和催化臭氧自身分解的性能，共沉淀法制备催化剂的最佳Mn负载量为20％。O2气氛焙烧和Ce的加入，可以有效提高催化剂的活性和寿命。原因是O2气氛焙烧和Ce的加入可以提高Mn的氧化价态。催化剂失活的主要原因是有机副产物在催化剂表面吸附堆积，失活催化剂在550℃、空气气氛下焙烧可恢复催化性能。     

Removal of ammonia solutions used in catalytic wet oxidation processes

Ammonia (NH(3)) is an important product used in the chemical industry, and is common place in industrial wastewater. Industrial wastewater containing ammonia is generally either toxic or has concentrations or temperatures such that direct biological treatment is unfeasible. This investigation used aqueous solutions containing more of ammonia for catalytic liquid-phase oxidation in a trickle-bed reactor (TBR) based on Cu/La/Ce composite catalysts, prepared by co-precipitation of Cu(NO(3))(2), La(NO(3))(2), and Ce(NO(3))(3) at 7:2:1 molar concentrations. The experimental results indicated that the ammonia conversion of the wet oxidation in the presence of the Cu/La/Ce composite catalysts was determined by the Cu/La/Ce catalyst. Minimal ammonia was removed from the solution by the wet oxidation in the absence of any catalyst, while approximately 91% ammonia removal was achieved by wet oxidation over the Cu/La/Ce catalyst at 230 degrees C with oxygen partial pressure of 2.0 MPa. Furthermore, the effluent streams were conducted at a liquid hourly space velocity of under 9 h(-1) in the wet catalytic processes, and a reaction pathway was found linking the oxidizing ammonia to nitric oxide, nitrogen and water. The solution contained by-products, including nitrates and nitrites. Nitrite selectivity was minimized and ammonia removal maximized when the feed ammonia solution had a pH of around 12.0.     

钾掺杂对铈锆固溶体催化性能的影响

为研究钾掺杂对铈锆固溶体催化性能的影响,以Ce0.7Zr0.3O2为基体制备了一系列钾掺杂的铈锆固溶体xK-Ce0.7Zr0.3O2(x=0.05、0.10、0.15、0.20、0.25、0.30)催化剂样品,通过程序升温氧化(TPO)过程进行活性评价,并通过XRD、BET、H2-TPR和O2-TPD进行分析表征。结果表明,采用溶胶凝胶法制备的催化剂的催化性能比络合燃烧法所制备的稍好;当钾的掺杂量为0.10≤x≤0.30时,xK-Ce0.7Zr0.3O2催化碳烟颗粒燃烧的活性得到提高,起燃温度和最大燃烧速率温度分别在315℃和375℃附近,明显优于Ce0.7Zr0.3O2;掺杂钾后的催化剂样品均能形成萤石结构,并且随钾掺杂量的增大比表面积减小。     

各类VOCs在蜂窝陶瓷型La0.8Sr0.2MnO3催化剂上的催化燃烧性能

以涂有CeO2-ZrO2固溶体的堇青石蜂窝状陶瓷为载体,用浸渍法制备堇青石蜂窝陶瓷型整体La0.8Sr0.2MnO3催化剂,测试了该催化剂催化燃烧各类VOCs的特性。研究表明,VOCs催化燃烧的难易程度为：含氯烃〉烷烃〉酸〉芳烃〉酮〉酯〉醇〉醛。La0.8Sr0.2MnO3催化剂对含氧有机化合物具有较好的催化活性,完全燃烧温度均在280℃之内。通过关联VOCs的理化性质,发现VOCs在La0.8Sr0.2MnO3催化剂上的反应活性与VOCs分子中最弱C—H键键能和VOCs分子极性密切联系。     

Diesel reformulation using bio-derived propanol to control toxic emissions from a light-duty agricultural diesel engine

In the Indian agricultural sector, millions of diesel-driven pump-sets were used for irrigation purposes. These engines produce carcinogenic diesel particulates, toxic nitrogen oxides (NOx), and carbon monoxide (CO) emissions which threaten the livelihood of large population of farmers in India. The present study investigates the use of n-propanol, a less-explored high carbon bio-alcohol that can be produced by sustainable pathways from industrial and crop wastes that has an attractive opportunity for powering stationary diesel engines meant for irrigation and rural electrification. This study evaluates the use of n-propanol addition in fossil diesel by up to 30% by vol. and concurrently reports the effects of exhaust gas recirculation (EGR) on emissions of an agricultural DI diesel engine. Three blends PR10, PR20, and PR30 were prepared by mixing 10, 20, and 30% by vol. of n-propanol with fossil diesel. Results when compared to baseline diesel case indicated that smoke density reduced with increasing n-propanol fraction in the blends. PR10, PR20, and PR30 reduced smoke density by 13.33, 33.33, and 60%, respectively. NOx emissions increased with increasing n-propanol fraction in the blends. Later, three EGR rates (10, 20, and 30%) were employed. At any particular EGR rate, smoke density remained lower with increasing n-propanol content in the blends under increasing EGR rates. NOx reduced gradually with EGR. At 30% EGR, the blends PR10, PR20, and PR30 reduced NOx emissions by 43.04, 37.98, and 34.86%, respectively when compared to baseline diesel. CO emissions remained low but hydrocarbon (HC) emissions were high for n-propanol/diesel blends under EGR. Study confirmed that n-propanol could be used by up to 30% by vol. with diesel and the blends delivered lower soot density, NOx, and CO emissions under EGR.     

CWAO of phenol using CeO2/gamma-Al2O3 with promoter--effectiveness of promoter addition and catalyst regeneration

The effect of promoter addition on activity of CeO(2)/gamma-Al(2)O(3) was assessed via the CWAO of phenol. Adding Cu as the promoter rendered the most effective performance, followed by Mn, although the performance of Mn-promoted catalyst was inferior to CeO(2)/gamma-Al(2)O(3). Mineralization of phenol was effectively implemented at 160 degrees C using Cu-promoted catalyst (Ce15Cu5). Furthermore, at 180 degrees C this catalyst produced about 100% conversion of phenol (1h) and 95% removal of chemical oxygen demand (4h), higher than that of CeO(2)/gamma-Al(2)O(3). In contrast, Mn-promoted catalyst (Ce15Mn5) required a temperature above 220 degrees C for acceptable performance. Activity of re-used catalyst declined noticeably, due to deposits of carbonaceous compounds and leaching of metal ions. Regeneration with acetone rinsing after the first run was effective in recovering activity of Ce15Cu5, although after a second run further regeneration with acetone rinsing had only a moderate effect, due to residual carbonaceous deposits and the additive effect of leached metal species in each run. As an alternative to acetone, HCl or HNO(3) solution (0.01 M) was less effective at regenerating activity. In promoted catalysts, leached metal ions accounted for the majority of mineralization of phenol, while the solid catalyst played a dual role of initiator and terminator of free radicals. Despite a superior catalytic performance, leaching of Cu(2+) from the promoted catalyst caused a severe decline in activity and poses the problem of secondary pollution of treated wastewater. Therefore, addition of Cu, as well as other metal species, is unfavorable in promoting the CeO(2)/gamma-Al(2)O(3) catalyst.     

Catalyst Deterioration over the Lifetime of Small Utility Engines

Abstract

In this paper, the deterioration of catalysts in small, four-stroke, spark-ignition engines is described. The laboratory testing performed followed a proven test method that mimics the lifetime of a small air-cooled utility engine operating under normal field conditions. The engines used were single-cylinder, 6.5-hp, side-valve engines. These engines have a nominal 125-hr lifetime. The effectiveness of the catalysts was determined by testing exhaust emissions before and after the catalyst to determine the catalyst’s efficiency. This was done several times during the lifetime of the engines to determine the deterioration in the performance of the catalysts at lowering pollutant emissions. Additional testing was performed on the catalysts to determine wear patterns, contamination, and recoverable activity. The results indicate that considerable catalyst deterioration is occurring over the lifetime of the engine. The results reveal that soot buildup, poisons, and active surface loss appear to be the contributing factors to the deterioration. These results were determined after analyzing the exhaust emissions data, scanning electron microscope results analysis, and the impact of regeneration attempts. An ANOVA statistical analysis was performed, and it was determined that the emissions are also impacted, to some degree, by time and the engine itself.