Complete catalytic oxidation of o-xylene over CeO2 nanocubes

The activities of CeO2 nanocubes calcined at di erent temperatures were tested for catalytic oxidation of o-xylene. Using CeO2 nanocubes as catalysts, complete catalytic oxidation of o-xylene was achieved below 210°C. The CeO2 nanomaterials were characterized by means of BET, X-ray di raction (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). From the TEM images, all CeO2 nanocubes displayed cubic morphology irrespective of calcination temperature. The HRTEM images revealed that these nanocubes were enclosed by reactive f001g planes, which may contribute to the intrinsically catalytic property of o-xylene oxidation. The higher activity of CeO2 nanocubes calcined at 550°C than those calcined at above 550°C was attributed to their smaller crystallite size and larger surface area. The influences of reaction conditions were also studied, which found that a higher reaction temperature was necessary for complete catalytic oxidation of o-xylene at higher weight hourly space velocity (WHSV) and o-xylene concentration.     

纳米CeO2催化氧化甲苯的形貌效应研究

采用水热法合成CeO2纳米棒、纳米颗粒和纳米立方体,利用XRD、BET-N2、TEM/HRTEM、Raman、O2-TPD和H2-TPR等表征手段进行表征,并利用连续流固定床反应法研究各催化剂对甲苯的催化氧化性能.结果表明,CeO2纳米棒因具有高比表面积和细颗粒尺寸,且表面主要暴露高活性的{100}/{110}晶面,拥有更多的氧空位和高活性氧物种,因此,催化活性最高,CeO2纳米颗粒次之,立方体最低.原位红外甲苯催化氧化机理分析进一步表明,CeO2纳米颗粒和纳米立方体上生成的羧酸盐物质难以进一步深度氧化,而纳米棒能在贫氧和低温条件下诱导甲苯的完全氧化和产物脱附,使甲苯得以快速降解.     

焙烧温度对CeO_2(ZrO_2)/TiO_2选择性催化脱硝性能的影响

采用溶胶-凝胶法并以不同温度焙烧制备一系列CeO_2(ZrO_2)/TiO_2(CZT)催化剂,考察了CZT催化剂固相结构、酸量、比表面积等性能与催化活性的关系。采用XRD、BET、NH3-TPD、H2-TPR以及XPS等表征技术对催化剂进行表征。结果表明:焙烧温度为450℃时CZT催化剂具有最高的催化活性,其在240~400℃的温度窗口内活性均高于90%,且具有较好的抗水和抗硫中毒能力。随着焙烧温度的提高,催化剂表面的Ce和Zr原子进入体相晶格且Ce0.5Zr0.5O2向Ce0.75Zr0.25O2转变,导致催化剂的储释氧能力和氧化还原性能降低。另外,锐钛矿和金红石型TiO_2晶粒尺寸的增加,催化剂的有效比表面积和总酸量降低,因此CZT催化活性随着焙烧温度的提高而有所降低。换言之,大的比表面积、良好的氧化还原性能、表面Ce4+的富集以及酸性位的增多均有利于NH3-SCR活性的提高。     

用于碳烟燃烧的Cu0.05Ce0.95O催化剂活性氧物种的研究 ——等离子体的强化效应

研究等离子体对柠檬酸络合法制备的Cu0.05Ce0.95-CA催化剂表面结构和物种的强化效应. TPO、H2-TPR、O2-TPD、XRD、BET和XPS等测试结果表明,催化剂处于等离子放电区时,其氧化碳烟燃烧的活性显著增强.在介质阻挡放电电压为9kV时,起燃温度为243.1℃,比无等离子的情况降低了65.1℃;燃烧峰值温度为302.8℃,降低92.7℃.在等离子体存在下,Cu0.05Ce0.95-CA催化剂有着更大的比表面积和更小的晶粒粒径;等离子体可以提高催化剂表面游离态的CuO的分散度,并使得更多的Cu2+进入CeO2晶格,形成更多的Cuy2+Ce1-y4+O2-y2-□y固熔体,催化剂储氧容量增大,在催化剂表面生成更多的活性氧物种,其流动、迁移和转化促进催化剂产生更多的氧空穴,如此循环,持续促进碳烟催化燃烧.     

纳米TiO2光催化氧化微量丙酮气的研究

采用溶胶-凝胶法制备了纳米TiO2膜。测试了TiO2光催化剂对微量丙酮气的催化氧化反应性能的测试。结合TG,XRD及TEM等对催化剂的表征,研究了纳米TiO2膜的制备条件对其结构和反应性能的影响,探索了纳米TiO2膜光催化氧化的机理。结果表明：制得的TiO2膜平均粒径为20nm,TiO2膜经550℃焙烧后呈现锐钛型和少量金红石型晶体的混晶。当金红石型的质量分数为13．6％时,TiO2光催化剂表现出较好的催化活性,丙酮的转化率最高达到45．26％。     

Mn基金属氧化物催化剂常温催化氧化甲醛

以硝酸铈和高锰酸钾为原料,采用络合法制备了一系列Mn-Ce-O混合氧化物催化剂,并通过正交实验设计方案,考察了Mn/Ce摩尔比、水化热温度、焙烧温度及焙烧时间对Mn-Ce-O混合氧化物催化剂常温催化氧化甲醛性能的影响,并采用X射线衍射仪（XRD）、扫描电镜（SEM）、透射电镜（TEM）和红外光谱（IR）等技术对催化剂进行微观表征与分析.结果表明：当Mn/Ce摩尔比1：1,水化热温度为180℃,焙烧温度为350℃时,催化剂表现出最佳的常温氧化活性,36h甲醛降解率可达94.2%,且稳定性良好.催化剂氧化活性的高低与材料比表面积并非正相关,而与材料结构形态存在密切关联,而材料结构主要取决于水化热温度,其次是Mn/Ce摩尔比.     

微波加热下苯的催化氧化性能研究

研究考察了微波加热与传统电炉加热两种不同加热方式下苯的催化氧化性能,同时考察了微波加热下铜锰质量比,铈掺杂量及焙烧温度变化对铜-锰-铈/分子筛催化剂催化氧化苯性能的影响,并对催化剂进行了SEM和XRD表征.结果表明,微波加热下苯的催化氧化性能优于电炉加热,微波的"局部热点"效应、偶极极化作用与稳定的床层反应温度保证了苯的高效催化氧化;铜∶锰∶铈质量比1∶1∶0.33和焙烧温度500℃下催化剂的活性最高,苯的起燃温度与完全燃烧温度分别为165℃和230℃.催化剂表征分析可知,铜、锰氧化物及铜锰尖晶石固溶物等活性相的存在保证了催化剂的高活性;稀土元素铈的掺杂促进了活性组分在催化剂表面的分散与规整化;高温焙烧可导致催化剂表面的烧结与活性组分的团聚,从而降低其催化氧化苯的活性.     

Preparation of birnessite-supported Pt nanoparticles and their application in catalytic oxidation of formaldehyde

Flaky and nanospherical birnessite and birnessite-supported Pt catalysts were successfully prepared and characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and N₂ adsorption-desorption. Effects of the birnessite morphology and Pt reduction method on the catalytic activity for the complete oxidation of formaldehyde (HCHO) were investigated. It was found that flaky birnessite exhibited higher catalytic activity than nanospherical birnessite. The promoting effect of Pt on the birnessite catalyst indicated that the reduction method of the Pt precursor greatly influenced the catalytic performance. Flaky birnessite-supported Pt nanoparticles reduced by KBH₄ showed the highest catalytic activity and could completely oxidize HCHO into CO₂ and H₂O at 50℃, whereas the sample reduced using H₂-plasma showed lower activity for HCHO oxidation. The differences in catalytic activity of these materials were jointly attributed to the effects of pore structure, surface active sites exposed to HCHO and the dispersion of Pt nanoparticles.     

In situ adsorption-catalysis system for the removal of o-xylene over an activated carbon supported Pd catalyst

An activated carbon (AC) supported Pd catalyst was used to develop a highly efficient in situ adsorption-catalysis system for the removal of low concentrations of o-xylene. In this study, three kinds of Pd/AC catalysts were prepared and tested to investigate the synergistic efficiency between adsorption and catalysis for o-xylene removal. The Pd/AC catalyst was first used as an adsorbent to concentrate dilute o-xylene at low temperature. After saturated adsorption, the adsorbed o-xylene was oxidized to CO2 and H2O by raising the temperature of the catalyst bed. The results showed that more than 99% of the adsorbed o-xylene was completely oxidized to CO2 over a 5% Pd/AC catalyst at 140℃. Brunauer-Emmett-Teller (BET) analysis, scanning electron microscopy (SEM), temperature-programmed desorption (TPD), and temperature-programmed oxidation (TPO) were applied to investigate the physical properties of o-xylene adsorption-desorption and the in situ adsorption-catalysis activity of the AC support and Pd/AC catalyst. A synergistic relationship between the AC support and the active Pd species for the removal of low concentrations of o-xylene was established.     

制备方法条件对Au/CeO2催化CO低温氧化性能研究

用共沉淀法和沉积沉淀法制备了负载型Au/CeO2催化剂,考察了不同制备方法和条件对Au/CeO2催化剂活性的影响。结果表明,制备方法和条件对Au/CeO2催化剂的活性有较大的影响,其中以Na2CO3为沉淀剂的共沉淀法制备的Au/CeO2催化剂活性最佳。最佳制备条件:343K洗涤、473K焙烧、空气预处理。金和部分氧化态的金是活性中心,而且氧化态的金催化活性更好。活性位在金与氧化物载体界面,金粒径越小,金与氧化物载体的接触面越大,活性位越多,催化活性越大。     

Au负载OMS-2催化剂的制备及其低温催化氧化性能

通过前掺杂法(QI),浸渍法(IM)和沉积-沉淀法(DP)3种方法制备了Au负载氧化锰八面体分子筛(OMS-2)Au/OMS-2催化剂,研究了制备方法和制备条件对其催化氧化CO活性的影响.采用X射线衍射(XRD)和BET比表面积测定等技术对所制样品进行表征.结果表明,沉积-沉淀法制备的Au/OMS-2-DP催化剂活性明显高于前掺杂法和浸渍法制备的催化剂,这与Au/OMS-2-DP催化剂比表面积较大和负载Au颗粒较小有关.制备条件(沉淀剂种类、制备溶液pH、Au负载量和催化剂焙烧温度)明显影响Au/OMS-2-DP催化剂的催化活性.对于各种不同的沉淀剂,以KOH为沉淀剂制备的催化剂活性最高,这可能与其无钝化作用,而且形成的Au颗粒较小有关;制备溶液的为最佳,当pH值过高或过低容易导致Au颗粒的聚集和Au沉淀量较少;XRD结果表明,当Au负载量为5wt%催化剂和催化剂焙烧为300℃时,所制备的催化剂颗粒最小,所得的催化剂活性最高.最佳条件制备的Au/OMS-2-DP催化剂活性较好,CO完全转化(100%)的温度为67℃.     

Morphology-dependent interfacial interactions of Fe2O3 with Ag nanoparticles for determining the catalytic reduction of p-nitrophenol

In this work,we fabricated three kinds of Ag/Fe_2O_3 model catalysts with different morphologies to study the interfacial interactions between Ag and Fe_2O_3,and how they affected the catalytic activity in hydrogenation of p-nitrophenol was explored.The hydrothermal method was used to synthesize the metal oxide supported silver catalyst,with various morphologies including nanoplates(NPs),nanospheres(NSs),and nanocubes(NCs).The crystal structure,morphology and surface elements of the composite were investigated by various measurements,such as X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM) and X-ray photoelectron spectroscopy(XPS).The catalytic activity was also evaluated by the reduction of p-nitrophenol to p-aminophenol.It was found that the activities of the above catalysts varied with the morphology of the support.Among them,Ag/Fe_2O_3 NPs promoted the highest performance,Ag/Fe_2O_3 NSs were slightly inferior,and Ag/Fe_2O_3 NCs were the worst.At last,we ascribed the remarkable activity of Ag/Fe_2O_3 NPs to the strong metal-support interactions between Ag and Fe_2O_3.     

Preparation of ceria-zirconia solid solution with enhanced oxygen storage capacity and redox performance

A new method called ultrasonic-assisted membrane reaction (UAMR) was reported for the fabrication of ceria-zirconia solid solution. A series of ceria-zirconia solid solutions with different Ce/Zr molar ratios were prepared by the UAMR method and characterized by X-ray diffraction (XRD), N₂ adsorption, hydrogen temperature-programmed reduction (H₂-TPR), scanning electron microscope (SEM), and transmission electron microscopy (TEM) techniques. The UAMR method proved to be superior, especially when the Ce/Zr molar ratio was lower than 1, in fabricating ceria-zirconia solid solutions with large BET surface area, high oxygen storage capacity (OSC), and low reduction temperature.     

Photocatalytic performance of TiO2 catalysts modified by H3PW12O40, ZrO2 and CeO2

The binary composite photo-catalysts CeO2/TiO2, ZrO2/TiO2 and the ternary composite photo-catalysts H3PW12O40-CeO2/TiO2,H2PW12O40-ZrO2/TiO2 were prepared by sol-gel method. The catalysts were characterized by thermogravimetric-differential thermal analysis (TG-DTA), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The photocatalyfic elimination of methanol was used as model reaction to evaluate the photocatalytic activity of the composite catalysts under ultraviolet light irradiation. The effects of doped content, activation temperature, time, initial concentration of methanol and gas flow rate on the catalytic activity were investigated. The results showed that after doping a certain amount of CeO2 and ZrO2, crystaniTation process of TiO2 was restrained, particles of catalysts are smaller and more uniform. Doping ZrO2 not only significantly improved the catalytic activity, but also increased thermal stability. Doping H3PW12O40 also enhanced the catalytic activity. The catalytic activities of binary and ternary composite photocatalysts were significantly higher than tin-doped TiO2. The dynamics law of photocatalytic reaction over the binary CeO2/TiO2 and ZrO2/TiO2 catalysts has been studied. The activation energy 15.627 and 15.631 kJ/mol and pre-exponential factors 0.5176 and 0.9899 s-1 over each corresponding catalyst were obtained. This reaction accords to the first order dynamics law.     

Mn-Co/MCM-41吸附剂表征及脱除烟气中单质汞研究

针对燃煤烟气中单质汞(Hg0)不溶于水而颇难去除的问题,采用浸渍法制备了不同Mn和Co物质的量比的Mn-Co/MCM-41介孔分子筛吸附剂,在固定床实验台架上考察了各吸附剂的脱汞效率.采用N2吸附/脱附、X射线衍射(XRD)、透射电子显微镜(TEM)、高分辨透射电子显微镜(HRTEM)、H2程序升温还原(H2-TPR)和X射线光电子能谱(XPS)等技术对吸附剂进行了物理化学性质表征.结果表明:Mn和Co复合后,吸附剂的脱汞效率显著提高.Mn/Co物质的量比为3/1时,吸附剂的脱汞效率最高,反应温度为150℃时,其脱汞效率高达90%.与单一组分Mn或Co负载MCM-41吸附剂相比,Co的掺杂不但使Mn和Co在MCM-41上的分散更均匀,还会促进Mn3+和Mn2+向Mn4+的转化和提高吸附剂的还原特性,增强吸附剂的脱汞性能.     

锰铈脱硝催化剂的制备及其再生性能研究

采用等体积浸渍法制备了一系列Mn-Ce-Ox复合氧化物脱硝催化剂用于NH3选择性催化还原(NH3-SCR)NO。考察了Mn/Ce摩尔比、焙烧温度、H2O和SO2对Mn-Ce-Ox复合氧化物脱硝催化剂活性的影响及催化剂中毒再生性能。结果表明:当NH3:NO=1:1,空速为5 000 h-1,550℃焙烧制得的Mn/Ce摩尔比为5∶1的Mn-Ce-Ox复合脱硝催化剂活性最佳,活性温度窗口为100~260℃,在此温度区间内催化剂活性大于90%。200℃时,Mn-Ce-Ox复合催化剂活性最高为97.84%;在10%(V/V)H2O蒸汽和300×10-6SO2共存条件下,200℃时,催化剂活性在开始反应2.5 h内迅速下降至53%左右,并在之后的6 h内没有明显变化;中毒催化剂经常温水洗再生处理、质量分数为3%的硝酸溶液再生处理和550℃焙烧2 h再生处理后200℃活性均能恢复到90%以上,其中中毒催化剂经质量分数为3%硝酸处理后活性恢复率最高。     

硼掺杂CeO2/TiO2光催化剂的制备及其活性研究

在三氯化钛和钛酸丁酯水解过程中引入硼酸、硝酸铈,制备了具有可见光活性的硼(B)掺杂CeO₂/TiO₂复合氧化物光催化剂,采用XRD、DRS、XPS等手段进行表征,以偶氮染料酸性红B为模型污染物评估了催化活性.结果表明,硝酸铈加入量影响催化剂的吸收带边,随用量增加,吸收带边红移至481nm(Ce/Ti=1.0,摩尔比),继续增加用量,吸收带边轻微蓝移.催化剂晶相组成与焙烧温度有关,500℃时焙烧样品主要由立方晶型CeO₂和锐钛矿TiO₂组成,焙烧温度高于700℃时,TiO₂转化为金红石型,CeO₂则无显著变化.随焙烧温度升高,催化剂吸收带边明显蓝移,综合考虑催化剂稳定性和太阳能利用,认为500℃焙烧较为合适.B1s XPS显示仅有少量B原子进入复合氧化物晶格取代了氧原子,主要以B₂O₃形式存在.酸性红B降解试验显示B掺杂CeO₂/TiO₂可以提高TiO₂的催化活性,紫外光辐射10min最高可使96.0%的酸性红B分解,且反应彻底,表现出较强的氧化能力,但Ce/Ti>0.5(摩尔比)时催化活性显著下降.     

Photocatalytic degradation of Acid Blue 62 over CuO-SnO2 nanocomposite photocatalyst under simulated sunlight

The novel CuO-SnO2 nanocomposite oxide photocatalysts were prepared by simple co-precipitation method, and characterized by X- ray diffraction, transmission electron microscopy, N2 adsorption-desorption measurement and UV-Vis diffuse reflectance spectroscopy. The photocatalytic activities of CuO-SnO2, evaluated using the photodegradation of Acid Blue 62 as a probe reaction under the irradiation of Xenon light, were also found to be related to the calcination temperature and the molar ratio of Cu to Sn. The maximum photocatalytic activity of the CuO-SnO2 photocatalyst was observed to be calcined at 500~C for 3 h （the molar ratio of Cu to Sn was 1：1） due to the sample with good crystallization and high surface area. It also showed much higher photocatalytic activity in treatment dye wastewater under simulated sunlight irradiation compared to Degussa P25 TiO2.     

Preparation and characterization of Fe2O3-CeO2-TiO2/γ-Al2O3 catalyst for degradation dye wastewater

In order to develop a catalyst with high activity for catalytic wet oxidation (CWO) process at room temperature and atmospheric pressure, Fe2O3-CeO2-TiO2/γ-Al2O3 catalyst was prepared by consecutive impregnation method and the prepared parameters were optimized. The structure of the catalyst was characterized by BET, XRF, SEM and XPS technologies, and the actual wastewater was used to investigate the catalytic activity of Fe2O3-CeO2-TiO2/γ-Al2O3 in CWO process. The experimental results showed that the prepared catalyst exhibited good catalytic activity when the doping amount of Ti was 1.0 wt% (the weight ratio of Ti to carriers), and the middle product, CeO2-TiO2/γ-Al2O3, was calcined in 450℃ for 2 h. The CWO experiment for treating actual dye wastewater indicated that the COD, color and TOC of actual wastewater were decreased by 62.23%, 50.12% and 41.26% in 3 h,respectively, and the ratio of BOD5/COD was increased from 0.19 to 0.30.     

催化湿式氧化法处理桉木CTMP模拟废水

通过浸渍法制备固载金属非均相型催化剂,用于催化湿式氧化处理桉木CTMP模拟废水。结果表明:在焙烧温度400℃,焙烧时间4h,浸渍液浓度为6%,浸渍时间为5h下制得的CuO/γ-Al2O3催化剂的催化活性最好;在反应时间为8h,鞣酸溶液pH为4.5,H2O2加入量为0.2mL,催化剂用量为4g的条件下处理鞣酸溶液的效果最好,鞣酸去除率>90%。