Facile synthesis of Ag-modified manganese oxide for effective catalytic ozone decomposition

O3 decomposition catalysts with excellent performance still need to be developed. In this study, Ag-modified manganese oxides(AgMnOx) were synthesized by a simple co-precipitation method. The effect of calcination temperature on the activity of MnOx and AgMnOxcatalysts was investigated. The effect of the amount of Ag addition on the activity and structure of the catalysts was further studied by activity testing and characterization by a variety of techniques. The activity of 8%AgMnOxfor ozone decomposition was significantly enhanced due to the formation of the Ag1.8 Mn8 O16 structure, indicating that this phase has excellent performance for ozone decomposition.The weight content of Ag1.8 Mn8 O16 in the 8%AgMnOxcatalyst was only about 33.76%, which further indicates the excellent performance of the Ag1.8 Mn8 O16 phase for ozone decomposition. The H2 temperature programmed reduction(H2-TPR) results indicated that the reducibility of the catalysts increased due to the formation of the Ag1.8 Mn8 O16 structure.This study provides guidance for a follow-up study on Ag-modified manganese oxide catalysts for ozone decomposition.

Ce-promoted Mn/ZSM-5 catalysts for highly efficient decomposition of ozone

Manganese oxides supported by ZSM-5 zeolite(Mn/ZSM-5) as well as their further modified by Ce promoter were achieved by simple impregnation method for ozone catalytic decomposition. The yCe20Mn/ZSM-5–81 catalyst with 8% Ce loading showed the highest catalytic activity at relative humidity of 50% and a space velocity of 360 L/(g × hr), giving 93% conversion of 600 ppm O_(3) after 5 hr. Moreover, this sample still maintained highly activity and stability in humid air with 50%–70% relative humidity. Series of physicochemical characterization including X-ray diffraction, temperature-programmed technology(NH_3-TPD and H_(2)-TPR), X-ray photoelectron spectroscopy and oxygen isotopic exchange were introduced to disclose the structure-performance relationship. The results indicated that moderate Si/Al ratio(81) of zeolite support was beneficial for ozone decomposition owing to the synergies of acidity and hydrophobicity. Furthermore, compared with 20 Mn/ZSM-5-81, Ce doping could enhance the amount of low valance manganese(such as Mn^(2+) and Mn^(3+)). Besides, the Ce^(3+)/Ce^(4+) ratio of 8Ce20Mn/ZSM-5-81 sample was higher than that of 4Ce_(2)0 Mn/ZSM-5-81. Additionally, the synergy between the MnO_x and CeO_(2) could easily transfer electron via the redox cycle, thus resulting in an increased reducibility at low temperatures and high concentration of surface oxygen. This study provides important insights to the utilization of porous zeolite with high surface area to disperse active component of manganese for ozone decomposition.

Highly efficient removal of ozone by amorphous manganese oxides synthesized with a simple hydrothermal method

Amorphous manganese oxides (MnO_(x)) were synthesized by facile hydrothermal reactions between potassium permanganate and manganese acetate.Synthesis parameters,including hydrothermal time and temperature and molar ratio of precursors,significantly affected the ozone removal performance and structure property of MnO_(x).Amorphous MnO_(x)-1.5,which was prepared at the Mn^(2+)/Mn^(7+)molar ratio of 1.5 under hydrothermal conditions of 120℃ and 2 hr,showed the highest ozone removal rate of 93% after 480 min at the room temperature,RH (relative humidity)=80%and WHSV (weight hourly space velocity)=600 L/(g·hr).The morphology,composition and structure of catalysts were investigated with X-ray diffractometer (XRD),Raman spectra,N_(2) physisorption,field emission scanning electron microscope (FESEM),X-ray photoelectron spectroscopy (XPS),H2temperature-programmed reduction (H_(2)-TPR),O_(2) temperature-programmed desorption (O_(2)-TPD) and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS).It was confirmed that high catalytic activity of amorphous MnOxfor ozone removal was mainly ascribed to its abundant oxygen vacancies,high oxygen mobility and large specific surface area.

Highly active OMS-2 for catalytic ozone decomposition under humid conditions

Four kinds of cryptomelane-type octahedral molecular sieve(OMS)-2-X(the X represents the molar ratio of KMnO4/MnAc2) were prepared as catalytic materials for ozone decomposition through a one-step hydrothermal reaction of KMnO4 and MnAc2, by changing their molar ratios. These samples were characterized by N2 adsorption–desorption, X-ray di raction(XRD), transmission electron microscopy(TEM), scanning electron microscopy(SEM), temperature programmed reduction by H2(H2-TPR) and X-ray photoelectron spectroscopy(XPS). Among them, the OMS-2-0.7 sample showed the best O3 conversion of 92% under high relative humidity(RH) of 90% and gas hourly space velocity of 585,000 h-1. This was accordingly thought as a possible way for purifying ozone-containing waste gases under high RH atmospheres. The e ciency of ozone decomposition of the prepared OMS-2-X sample was found to be related to specific surface area, particle size, surface oxygen vacancies, and Mn3+ cation amounts. The one-step hydrothermal synthesis was shown to be a simple method to prepare the considerably active OMS-2 solids for ozone decomposition.

A novel process of ozone catalytic oxidation for low concentration formaldehyde removal

To reduce energy costs,minimize secondary pollution from undecomposed ozone,and improve the efficiency of ozone use,a novel process of cycled storage‐ozone catalytic oxidation(OZCO)was employed to remove formaldehyde(HCHO)at low concentrations in air.We applied Al2O3‐supported manganese oxide(MnOx)catalysts to this process,and examined the HCHO adsorption capacity and OZCO performance over the MnOx catalysts.Owing to the high dispersion of MnOx and low oxidation state of manganese,the MnOx/Al2O3catalysts with a manganese acetate precursor and10%‐Mn loading showed good performance in both storage and OZCO stages.The presence of H2O led to a decrease of the HCHO adsorption capacity owing to competitive adsorption between moisture and HCHO at the storage stage;however,high relative humidity(RH)favored complete conversion of stored HCHO to CO2at the OZCO stage and contributed to an excellent carbonbalance.Four low concentration HCHO storage‐OZCO cycles with a long HCHO storage period and relatively short OZCO period were successfully performed over the selected MnOx/Al2O3catalyst at room temperature and a RH of50%,demonstrating that the proposed storage‐OZCO process is an economical,reliable,and promising technique for indoor air purification.

铈锰复合氧化物高效催化分解臭氧

将Ce掺入MnO_(2)八面体分子筛(OMS-2)中得到铈锰氧化物催化剂。通过XRD,SEM,H_(2)-TPR,XPS等方法表征了催化剂的物理化学性质,模拟了该催化剂在高湿度下对高浓度臭氧的去除效果。实验结果表明,在OMS-2中掺Ce可使OMS-2晶型发生改变。Mn/Ce原子比为4的CeMn4的比表面积最大、粒径较小、氧空位浓度最高,因此具有优异的氧化还原性能,在湿度90%、体积空速700000 h^(-1)、反应时间420 min的条件下能实现臭氧分解率稳定在95%以上,且抗水性能强。铈锰复合氧化物有望成为工业上使用的催化分解臭氧的理想材料。

采用催化臭氧氧化降解煤化工含盐废水中有机物效能研究

采用催化臭氧氧化技术对煤化工气化污水生物处理单元出水中有机物进行强化去除。中试试验结果表明,采用碳基载锰氧化物催化剂催化臭氧氧化,能够显著提高臭氧对水中有机污染物的去除效能,较高的水样pH值、催化剂填充比、臭氧投量均有助于提高催化臭氧氧化体系对水中有机物污染物的去除效能。当臭氧投加量为32 mg/min,催化剂填充比例为1/8,反应时间60 min时,投加碳基载锰氧化物催化剂后,臭氧对水中有机物(COD)去除率由14.0%提升至65.0%。

高湿度条件下O_3在MnO_X/γ-Al_2O_3催化剂上的分解

用共沉淀法制备了一系列ＭｎＯＸ ／γ－Ａｌ２Ｏ３催化剂，并考察了它们对Ｏ３分解的催化性能．结果表明，Ｍｎ／Ａｌ摩尔比为１∶３，煅烧温度为５００℃时制得的催化剂即使在高湿度条件下，对Ｏ３也有很好的催化分解效果．ＸＲＤ，ＩＲ，ＸＰＳ等分析表明，催化剂的活性中心锰在反应前后其形态发生改变，催化剂表面有新的氧物种出现．进一步依据催化剂表面羟基对Ｏ３分解的影响，解释了Ｏ３在高湿度条件下的催化分解过程．

整体式锰基催化剂催化分解地表臭氧

通过焙烧碳酸锰粉末制备了高活性含缺陷氧原子的氧化锰材料(MnOx,x=1.6～2.0),用胶溶法制备了高比表面积的SiO2-Al2O3载体,然后用等体积浸渍法制备了不同MnOx担载量的Pd-MnOx/SiO2-Al2O3系列催化剂.结果表明,催化剂活性随MnOx含量的增加而增加,但无载体的MnOx催化剂易脱落,活性降低.在空速(GHSV)为360000h-1的条件下,MnOx含量为80%的催化剂对O3的完全转化温度(T100)为30℃;在GHSV=660000h-1时,MnOx含量在80%～90%的催化剂活性最高,T100为45～50℃,能满足在汽车运行时空气与汽车水箱瞬时接触温度的要求.在45℃和510000h-1条件下对MnOx担载量为80%的催化剂进行95h寿命测试后,O3的转化率大于90%,说明催化剂具有很强的抗失活能力.

高湿度条件下分解臭氧的锰催化剂

分别以硝酸锰和乙酸锰为前体 ,用浸渍法制备了MnOx γ Al2 O3催化剂 ,考察了它们对高湿度高浓度臭氧的催化分解性能。分析了在不同的温度煅烧和用不同的前体制备的催化剂上的氧化锰的形态。实验表明 ,以乙酸锰为前体 ,在 4 0 0℃煅烧得到的催化剂的臭氧催化分解活性最高 ,保持 95 %的臭氧分解率 ,其使用寿命在 10 0h以上 ,该催化剂上锰的主要形态为Mn2 O3。

锰负载量对活性炭载锰氧化物的结构及催化分解臭氧性能的影响(英文)

将高锰酸钾与活性炭（AC）原位氧化还原制备的活性炭载锰氧化物（MnOx/AC）用作臭氧分解的催化剂.采用扫描电镜、X射线光电子能谱、X射线衍射、电子自旋共振波谱、拉曼光谱以及程序升温还原研究了设计Mn负载量对负载锰氧化物性质（形貌、氧化态和晶体结构）的影响.结果表明, Mn负载量由0.44%增至11%,负载锰氧化物在活性炭表面由疏松的地衣状变为堆叠的纳米球状体,负载层的厚度由-180 nm增加至-710 nm,结构由氧化态＋2.9到＋3.1的低结晶β-MnOOH生长为由氧化态＋3.7到＋3.8的δ-MnO2结晶. MnOx/AC室温催化分解低浓度臭氧的活性与负载锰氧化物的形貌及含量密切相关. Mn负载量为1.1%的MnOx/AC具有疏松的地衣状形貌,催化分解臭氧的性能最高, Mn负载量为11%的MnOx/AC具有紧密的堆积结构,因而表现出最低的催化臭氧分解活性.

用于臭氧分解的负载型双金属催化剂

研究了催化剂载体外形和活性成分对催化剂性能的影响和其他污染物的反应对室内空气造成的二次污染。通过 XPS分析说明了反应过程中催化剂表面发生的化学变化及反应机理。

Pd/MnO_x+Pd/γ-Al_2O_3整体式催化剂降解地表臭氧

用高锰酸钾与硝酸锰氧化还原反应制备了高活性的氧化锰(MnO x)催化组分,用胶溶法制备了高比表面积的γ-Al2O3载体,分别用等体积浸渍法制备了Pd/MnO x和Pd/γ-Al2O3催化剂,然后将两者机械混合涂覆于堇青石上制得Pd/MnO x+Pd/γ-Al2O3整体式催化剂。采用X射线衍射(XRD)、X射线光电子能谱(XPS)、程序升温还原(H2-TPR)和低温N2吸附-脱附对催化剂进行了表征。考察了在300至700℃焙烧MnO x对催化剂降解地表O3活性的影响。结果表明,Pd和MnO x之间存在协同作用;MnO x焙烧温度对催化剂活性有一定的影响,其中以600℃焙烧时催化剂的活性最高,O3的起始(12℃)转化率达到88%,完全转化温度为18℃。MnOx的物相和催化剂表面的吸附氧物种对催化活性影响较大,适当比例的MnO2和Mn2O3共存有利于O3分解,表面吸附氧为O3分解的活性氧物种。

浸渍法制备的Pd-MnO_x/γ-Al_2O_3催化剂及不同载体对地表O_3降解的影响(英文)

在γ-Al2O3载体上用等体积浸渍法浸渍Pd、MnOx活性组分,然后涂覆于堇青石基体上制备Pd-MnOx/γ-Al2O3整体式催化剂.分别用X射线衍射(XRD)、H2-程序升温还原(H2-TPR)、低温N2吸附-脱附及X射线光电子能谱(XPS)对制备的催化剂进行表征.研究了Pd、MnOx浸渍顺序对催化剂活性、氧化还原性能及织构性质的影响.实验结果表明,Pd、MnOx共浸渍较分别浸渍制备的催化剂活性好,Pd和MnOx之间存在一定的协同作用.考察了不同载体如La-Al2O3、SiO2、γ-Al2O3和Zr-Al2O3对催化剂活性、氧化还原性能、织构性质及表面电子性能的影响.研究表明,以La-Al2O3或SiO2为载体的催化剂活性最好,即,14°C时O3转化率为82%,完全转化温度为36°C.γ-Al2O3载体次之,Zr-Al2O3载体较差.不同载体制备的催化剂中MnOx的氧化还原性能顺序为:PdMnOx/SiO2>Pd-MnOx/La-Al2O3>Pd-MnOx/γ-Al2O3>Pd-MnOx/Zr-Al2O3.

臭氧催化分解的研究

研究了多种单组分和双组分金属氧化物对臭氧催化分解的活性,单组分时催化分解活性次序为:Co>Mn≈Ni>Cr>Fe>Zn>Mg>Cu>Ag>Sn>Pb>U>Cd>Al>Si≈Bi≈Ce≈CaCO3≈La>Na。实验结果表明,几种双组分金属氧化物的催化分解活性主要由较高活性的金属氧化物所决定,并与两组分的比例有关。实验还表明,催化剂的催化分解活性与制备催化剂时的灼烧温度和时间有关,催化剂前驱体采用硝酸盐时比较合理的灼烧条件为:500℃,4 h。

用于臭氧尾气处理的催化剂的制备与表征

本文采用浸渍法制备出若干种负载型用于臭氧尾气处理的催化剂 ,并采用X—射线衍射和光电子能谱分析方法对催化剂进行表征 .经过筛选 ,优化出三种催化剂并研究处理臭氧尾气的催化性能 .实验结果表明 ,活性炭浸渍醋酸盐的催化剂 (活性主分的组成为MnO2 ∶CuO =3∶2 ,负载量为1 5wt% ,焙烧温度为 2 0 0℃ )

臭氧分解催化剂的制备及性能研究

用浸渍法制备了活性炭负载的复合金属氧化物催化剂并研究了其对臭氧的分解活性。在比较了MnO2 、Co3O4 、NiO、Fe2 O3、CuO等氧化物的基础上进行了复合金属氧化物 /活性炭催化剂的臭氧分解活性试验 ,结果发现Mn Cu系催化剂的活性高和寿命长 ,并且成本较低 ,具有良好的工业应用前景。

制备方法对Pd-MnO_x/γ-Al_2O_3催化剂分解地表O_3性能的影响(英文)

分别用溶胶凝胶法和分步沉淀法制备了MnOx+γ-Al2O3和MnOx/γ-Al2O3,用等体积浸渍法将等量的Pd(NO3)2分别浸渍于其上,再将它们分别涂覆于堇青石上,得到不同物理化学性质的整体式催化剂,并采用X射线衍射、X射线光电子能谱、程序升温还原和低温N2吸附-脱附等技术对催化剂进行表征.结果表明,制备方法和MnOx焙烧温度明显影响催化剂中MnOx的物相、表面Mn物种和表面活性氧物种的分布及织构性质.活性测试结果表明,两种制备方法得到的催化剂于16–90 oC,380000–580000 h–1条件下均可将0.6μL·L–1 O3完全分解;尤其是溶胶凝胶法制备的Pd/γ-Al2O3+MnOx/γ-Al2O3催化剂分解O3活性较好,催化剂表面Mn2+:Mn3+:Mn4+=1.7:1:3(mol).

氟里昂_(12)(CCl_2F_2)燃烧分解催化剂性能的研究

本文对贵金属、氧化物和复合氧化物体系催化剂上氟里昂_(12)(F_(12))燃烧分解反应进行了活性评价和稳定性研究.结果表明:TiO_2,ZrO_2/TiO_2催化剂对氟里昂_(12)燃烧分解反应具有良好的低温催化活性和较好的稳定性。

MnO_(x)/Mn-N/C碳基催化剂高效分解酸性过氧化氢

利用廉价的尿素与MnCl_(2)均匀混合并高温(550℃)碳化,制备了兼具MnO_(x)与Mn-N活位点的碳基催化剂(MnO_(x)/Mn-N/C)。形貌和结构分析表明,MnO_(x)/Mn-N/C表面含有丰富的MnO_(x)与Mn-N活性位点,且具有优异的电子传输性能,可催化H_(2)O_(2)分解为H_(2)O和O_(2),抑制强氧化性·OH的生成。60℃时,经MnO_(x)/Mn-N/C催化反应1 h,H_(2)O_(2)溶液(p H=4.0,质量分数为1.2%)的分解效率接近100%。此工作设计制备的催化剂原料廉价易得、制备简便,实现了酸性条件下H_(2)O_(2)的高效定性分解,为酸性条件下H_(2)O_(2)的分解提供了新思路。