焙烧温度及掺杂改性对负载型Mn-Ce/TiO2催化剂性能的影响

采用机械共混法在TiO2载体中掺杂Al2O3、SiO2、沸石等物质进行改性。并通过比表面检测仪(BET)、X射线衍射仪(XRD)、程序升温脱附等手段对负载活性组分后的载体进行表征,考察了载体的焙烧温度及掺杂Al2O3、SiO2、沸石后对负载型Mn-Ce/TiO2催化剂性能的影响。     

Al~(3+)掺入对CeO_2(ZrO_2)/TiO_2催化剂脱硝性能的影响

采用溶胶-凝胶法制备Al ~(3+)掺杂CeO_2(ZrO_2)/TiO_2催化剂,研究了Al ~(3+)掺入对CeO_2(ZrO_2)/TiO_2催化剂脱硝性能的影响。采用X射线衍射、氮气吸附脱附、氨气程序升温吸附、氢气程序升温还原以及荧光光谱等表征技术对催化剂进行表征。结果表明:Al ~(3+)的掺入有利于抑制TiO2从无定型相向锐钛矿相转变,增强了催化剂的储释氧性能,提高了催化剂的强酸酸量和缺陷浓度。强酸酸量和缺陷浓度的提高有利于反应气体的吸附;储释氧性能的增强,吸附的NO物种被氧化的速率加快,有利于催化反应的进行。因此,适量Al ~(3+)的掺入会明显提升CeO_2(ZrO_2)/TiO_2催化剂的高温脱硝活性,拓宽活性温度窗口。71400h-1条件下0.8Al-CZT催化剂在330℃达到最高活性(98.9%)且在400℃脱硝活性依然能够维持90.8%。     

四元SCR催化剂V2O5-WO3-MoO3/TiO2脱硝性能

以锐钛型TiO2为载体,V2O5为主要活性成分,同时负载WO3和MoO3作为活性助剂,制备了四元催化剂V2O5-WO3-MoO3/TiO2,并对该催化剂的脱硝活性、催化选择性及微观表征进行了研究。结果表明,该四元催化剂脱硝性能优于相同负载量下单一负载W或Mo的三元催化剂,W可以提高催化剂高温(>400℃)活性,同时抑制Mo在高温区间导致的副反应发生,Mo可以提高低温(<300℃)活性,弥补W在低温区间的活性不足。该四元催化剂最大活性99%,温度窗口(脱硝活性>80%)为280～420℃,在180～380℃范围内SO2氧化率为零,在0～1000℃范围内存在3个失重峰,100～130℃结晶水蒸发,230～270℃有机添加剂分解,500～530℃无机盐分解,微观镜像表明该催化剂颗粒均匀致密,粒径大小一致,没有出现团聚现象,具有完整的微孔结构。     

Ce-MnO_x/TiO_2-ZrO_2低温选择催化还原NO活性和抗毒性研究

采用溶胶-凝胶法制备TiO_2-ZrO_2载体,以硝酸锰为前驱体采用柠檬酸溶液浸渍法制备Ce(n)-MnO_x/TiO_2-ZrO_2复合催化剂。通过XRD、SEM-EDS、XPS等测试方法对催化剂的物化性能进行表征分析,并进行NH_3选择性催化还原NO实验,考察其在低温下的活性及抗水抗硫性能。结果表明,Ce-Mn氧化物和TiO_2-ZrO_2载体间发生了相互作用,后者结晶度发生变化。与MnO_x/TiO_2-ZrO_2比较,Ce(n)-MnO_x/TiO_2-ZrO_2中Mn~(4+)的含量提高。Ce元素以Ce~(4+)、Ce~(3+)存在于Ce(n)-MnO_x/TiO_2-ZrO_2中,在催化反应中能起到传递电子、离子和储氧的作用,提高催化剂的氧化还原能力,同时Ce元素的电离能和电负性要远小于Mn元素,优先于Mn发生化学反应,保护Mn元素的活性。Ce(0.2)-MnO_x/TiO_2-ZrO_2的颗粒分散均匀、粒径达到20nm左右。制备的Ce(n)-MnO_x/TiO_2-ZrO_2催化剂的低温活性和抗毒性都优于MnO_x/TiO_2-ZrO_2,其中Ce(0.2)-MnO_x/TiO_2-ZrO_2在80℃时脱硝效率为94%;100℃时脱硝效率达到100%,在同时通入5%H2O和100mg/m3 SO_2后,脱硝效率缓慢下降,反应210min降到85%后趋于稳定。     

四方相氧化锆基MnO_x-CeO_2负载型催化剂在低温NH_3-SCR中的应用

以纳米t-Zr O2为载体,用浸渍法制备出Mn Ox-Ce O2/t-Zr O2催化剂,考察了活性组分负载量、反应温度对催化剂NH3-SCR脱硝活性的影响,脱硝活性测试结果显示,在低温脱硝温度范围,催化剂脱硝效率随反应温度和活性组分负载量的增加而增加。反应温度为100℃时,2.5%Mn Ox-Ce O2/t-Zr O2脱硝效率为68.1%,15%Mn Ox-Ce O2/t-Zr O2脱硝效率达97.4%。XRD、BET、TPR等表征测试结果表明,催化剂表面具有良好的氧化还原能力,表面织构对NH3-SCR脱硝反应有利;NH3-TPD测试显示,Mn Ox-Ce O2/t-Zr O2催化剂表面NH3主要吸附在Lewis酸性位成配位态NH3,与气态NO反应生产中间产物NH2NO,最后分解为N2和H2O。     

二氧化硅基多孔块材的制备及其热稳定性

以非离子型表面活性剂P123和三甲基苯的微乳液为模板剂合成介孔SiO2粉体.以此粉体为原料,经干压成型、烧结制备多孔SiO2块材.分别用AlOOH溶胶和TiO2溶胶包覆多孔SiO2粉体,制成多孔SiO2/Al2O3块材和SiO2/TiO2块材.采用XRD、SEM、TEM、N2吸附法和阿基米德排水法对所制粉体和块材进行了表征,并研究了块材的热稳定性.结果表明,600～700℃烧结的多孔SiO2基块材的孔隙率为74%～76%.与多孔SiO2块材相比,在800～1000℃范围内,SiO2/Al2O3块材的热稳定性显著提高,SiO2/TiO2块材的热稳定性在800～900℃范围内有一定改善.     

化学气相沉积制备V_2O_5-WO_3/TiO_2催化剂及表征

以蜂窝堇青石为基体,采用化学气相沉积技术结合浸渍工艺制备出V2O5-WO3/TiO2脱硝催化剂,通过SEM、BET、XRD和EDS完成载体以及催化剂微观结构和成分表征,并利用活性评价装置测试了催化剂NO脱出率。试验结果表明,化学气相沉积技术制备的载体表面为锐钛矿型TiO2,其颗粒聚集成团块状,BET为62.73m2/g,平均孔径为9.8nm。制备的V2O5-WO3/TiO2催化剂孔结构规律与TiO2载体相似,V2O5在TiO2载体上无定形态单层分散,微量V2O5在微区长大成针状,宽度100nm;在350℃、4000h-1、n(NH3)/n(NO)=1时,催化剂NO脱出率ηNO达到96.7%。     

V2O5/CNFs/蜂窝状堇青石催化剂的结构控制及其烟气脱硝性能

采用化学气相沉积法,在涂层Al2O3的蜂窝状堇青石表面生长纳米碳纤维(CNFs),通过负载V2O5催化剂,制成低温蜂窝状脱硝催化剂.采用SEM、TEM、XRD和XPS等分析方法,对所制催化剂的物化性质及其脱硝性能进行了分析.研究结果表明,当CNFs在堇青石表面的生长厚度为0.74μm时,所制CNFs/堇青石载体的压缩强度达34.46 MPa;在150~250℃范围内,V2O5/CNFs/蜂窝状堇青石催化剂表现出较高的低温脱除NO活性,其中当CNFs的生长量为12.5%、V2O5担载量为1%时,在250℃下NO的转化率达95%左右.     

TiO_2-Al_2O_3负载型催化剂的制备及其光催化性能

以钛酸四丁酯和氢氧化钠为反应物,采用两步水热法制备TiO2纳米线,并将其原位负载于Al2O3载体上,研究它们对甲基橙的光催化降解性能。结果表明,锐钛矿相TiO2主要呈纳米线和八面体状负载在Al2O3载体上,当TiO2负载质量分数为30%,焙烧温度为400℃,催化剂用量为1.332 0 g/L时,TiO2-Al2O3负载型催化剂光催化降解甲基橙的性能最佳,光照5 h后,甲基橙在紫外和太阳光下的降解率分别达到58.9%和55.6%。相同实验条件下,TiO2-Al2O3负载型催化剂对甲基橙的降解率比单纯TiO2提高了35.1%。     

Ti-Al-Si-Ox脱硝催化剂载体的组分优化及性能研究

采用挤出成型法制备系列Ti-Al-Si-O_x脱硝催化剂载体, 评价其NH₃选择性催化还原NO的活性。通过正交实验优化Ti-Al-Si-O_x配方, 采用液N₂-BET、ESEM及XRD分别表征载体的比表面积、孔容孔径分布、微观形貌和固相结构; 采用阿基米德法测试载体的吸水率、开气孔率和体积密度。结果表明, 当Ti/Al/Si摩尔比为1:0.2:0.1时, TiAl_0.2Si_0.1O_x载体NH₃-SCR脱除NO活性及轴向抗压碎强度匹配最好。当空速为7200 h^-1, 载体在450~550℃内NH₃-SCR脱除NO效率均＞80%, 494℃脱除NO效率达到最大值85.8%; 载体抗压碎强度为6.17 MPa, 比表面积为89.1 m²/g, 开气孔率达63.0%, 吸水率达48.3%, 介孔最可几分布为8.1 nm, 次可几分布为3.7 nm。TiAl_0.2Si_0.1O_x脱硝催化剂载体具备优异的性能。     

固体超强酸SO42-/TiO2-Al2O3的制备及其催化合成冰片

采用溶胶-凝胶法和浸渍法制备了系列SO_4~(2-)/TiO_2-Al_2O_3固体超强酸催化剂,运用XRD、NH_3-TPD、FT-IR、PyFTIR、XPS、SEM等技术手段,研究了复合催化剂材料的结构与性质,初步探讨了固体超强酸SO_4~(2-)/TiO_2-Al_2O_3催化剂的构效关系,得到适宜的催化剂制备条件为:n(TiO_2)/n(Al_2O_3)=1∶2、硫酸浸渍浓度1mol/L、催化剂焙烧温度500℃。考察了物料物质的量比、催化剂用量、反应时间等对催化合成冰片的影响。结果表明,在物料物质的量比为1∶0.4,催化剂用量为α-蒎烯质量的7%,采用程序升温方式(65℃-1h,75℃-4h,90℃-1h)加热的条件下,固体超强酸SO_4~(2-)/TiO_2-Al_2O_3催化剂的催化活性最高,α-蒎烯的转化率高达100%,龙脑的收率高达59.74%,SO_4~(2-)/TiO_2-Al_2O_3固体超强酸催化剂在重复使用6次的条件下,α-蒎烯的转化率均不变,龙脑的收率下降2.99%,催化剂的重复使用性良好。     

Fe~(3+)/Ti~(4+)赋存状态对钛酸铝/莫来石复合材料结构的影响

借助XRD、SEM和能谱分析仪等手段,研究了1 600℃煅烧中低品位矾土制备的钛酸铝/莫来石(Al_2TiO_5ss/3Al_2O_3·2SiO_2ss)复合材料经1 200℃保温12h后结构的稳定性。结果表明:高温煅烧中低品位矾土后,其合成材料的结晶物相组成为3Al_2O_3·2SiO_2ss、Al_2TiO_5ss和少量残存的方石英;Fe~(3+)或Ti~(4+)离子以不同形态赋存于结晶相(3Al_2O_3·2SiO_2ss和Al_2TiO_5ss)和非晶相。含Fe~(3+)/Ti~(4+)离子的3Al_2O_3·2SiO_2ss将Al_2TiO_5ss结晶相分割,使其蜷缩其间,并抑制Al_2TiO_5ss的分解;高温下,二者因组成元素相近而致使晶界融合,进而共同构建了体系牢固的致密骨架结构。由3Al_2O_3·2SiO_2ss和Al_2TiO_5ss等高温物相构成的致密结构将非晶相挤压于空隙结构的3Al_2O_3·2SiO_2ss晶间,避免了低熔点相富集带来的不利影响,进而赋予该Al_2TiO_5ss/3Al_2O_3·2SiO_2ss复合材料良好的结构稳定性。     

The catalytic oxidation of aromatic hydrocarbons over supported metal oxide

The catalytic activity of metals (Cu, Mn, Fe, V, Mo, Co, Ni, Zn)/gamma-Al2O3 was investigated to bring about the complete oxidation of benzene, toluene and xylene (BTX). Among them, Cu/gamma-Al2O3 was found to be the most promising catalyst based on activity. X-ray diffraction (XRD), Brunauer Emmett Teller method (BET), electron probe X-ray micro analysis (EPMA) and temperature programmed reduction (TPR) by H2 were used to characterize a series of supported copper catalysts. Increasing the calcination temperature resulted in decreasing the specific surface areas of catalysts and, subsequently, the catalytic activity. Copper loadings on gamma-Al2O3 had a great effect on catalytic activity, and 5 wt.% Cu/gamma-Al2O3 catalyst was observed to be the most active, which might be contributed to the well-dispersed copper surface phase. Using TiO2 (anatase), TiO2 (rutile), SiO2 (I) and SiO2 (II) as support instead of gamma-Al2O3, the activity sequence of 5 wt.% Cu with respect to the support was gamma-Al2O3 > TiO2 (rutile) > TiO2 (anatase)>SiO2 (I) > SiO2 (II), and this appeared to be correlated with the distribution of copper on support rather than with the specific surface area of the catalyst. The smaller particle size of copper, due to its high dispersion on support, had a positive effect on catalytic activity. The activity of 5 wt.% Cu/gamma-Al2O3 with respect to the VOC molecule was observed to follow this sequence: toluene > xylene > benzene. Increasing the reactant concentration exerted an inhibiting effect on the catalytic activity.     

超临界流体干燥法制备TiO2/ Fe2O3 和TiO2/ Fe2O3/ SiO2 复合纳米粒子及光催化性能

以TiCl₄ 、Fe (NO₃ )₃·9H₂O 和Na₂SiO₃19H₂O 为原料, 采用溶胶凝胶法结合超临界流体干燥法(SCFD)制备了纳米级TiO₂/ Fe₂O₃ 和TiO₂/ Fe₂O₃/ SiO₂ 复合光催化剂。以光催化降解苯酚对所得催化剂的催化活性进行了评价。结果表明, 纳米TiO₂/ Fe₂O₃ 复合粒子与单组分TiO₂ 比较, 复合粒子光催化活性高于单组分的TiO₂, 6h 苯酚降解率高达95.9 %。SiO₂ 的加入可以抑制纳米粒子粒径的长大和晶相的转变, 增强TiO₂ 纳米粒子的热稳定性。复合光催化剂中Fe₂O₃ 最佳掺入量为0.06 %, SiO₂ 最佳掺入量为10 %(摩尔分数) 。并用XRD、TEM 和FTIR 等手段进行了表征。TiO₂ 以锐钛矿型形式存在, SiO₂ 以无定性形式存在。比较了不同制备方法制得的TiO₂/ Fe₂O₃ 复合光催化剂, 得出超临界干燥法制备的光催化剂具有粒径小、比表面积大、分散性好、光催化活性高等特点。采用超临界流体干燥可直接得锐钛型纳米复合光催化剂。     

Corrosion Resistance of Plasma Sprayed Ceramic CompositeCoatings on Q235 Substrate

The corrosion resistance of SiO2/Al2O3, TiO2/Al2O3 and (SiO2+TiO2)/Al2O3 ceramic composite coatings on Q235 substrate fabricated by means of plasma spraying was investigated. The results show that Al2O3+13 wt pct TiO2 ceramic coating has the highest density, the lowest connected porosity and the best corrosion resistance. The corrosion mechanism of Q235 with ceramic coating has also been studied.     

Benzene oxidation with ozone over supported manganese oxide catalysts: effect of catalyst support and reaction conditions

Catalytic oxidation of gaseous benzene with ozone was carried out over supported manganese oxides to investigate the factors controlling the catalytic activities. The rate for benzene oxidation linearly increased with the surface area of catalyst, regardless of the kinds of catalyst support, whereas the ratio of ozone decomposition rate to benzene oxidation rate was larger for SiO(2)-supported catalyst than Al(2)O(3)-, TiO(2)-, and ZrO(2)-supported catalysts. The rate for benzene oxidation and CO(x) selectivity increased with the reaction temperature (22-100 degrees C) and were improved by the addition of water vapor to reaction gases. Benzene conversion and carbon balance increased with ozone concentration.     

Enhancing both selectivity and coking-resistance of a single-atom Pd<Subscript>1</Subscript>/C<Subscript>3</Subscript>N<Subscript>4</Subscript> catalyst for acetylene hydrogenation

Selective hydrogenation is an important industrial catalytic process in chemical upgrading,where Pd-based catalysts are widely used because of their high hydrogenation activities.However,poor selectivity and short catalyst lifetime because of heavy coke formation have been major concerns.In this work,atomically dispersed Pd atoms were successfully synthesized on graphitic carbon nitride (g-C3N4) using atomic layer deposition.Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) confirmed the dominant presence of isolated Pd atoms without Pd nanoparticle (NP) formation.During selective hydrogenation of acetylene in excess ethylene,the g-C3N4-supported Pd NP catalysts had strikingly higher ethylene selectivities than the conventional Pd/A12O3 and Pd/SiO2 catalysts.In-situ X-ray photoemission spectroscopy revealed that the considerable charge transfer from the Pd NPs to g-C3N4 likely plays an important role in the catalytic performance enhancement.More impressively,the single-atom Pd1/C3N4 catalyst exhibited both higher ethylene selectivity and higher coking resistance.Our work demonstrates that the single-atom Pd catalyst is a promising candidate for improving both selectivity and coking-resistance in hydrogenation reactions.     

TiO_2对挤压铸造Al_2O_(3p)/钢基复合材料组织与力学性能的影响

在预制坯中加入TiO_2粉末,利用挤压铸造法制备Al_2O_3颗粒增强1065钢基复合材料,研究TiO_2对复合材料组织与力学性能的影响。结果表明:TiO_2使基体与Al_2O_3的结合界面形成了TiO_2、Al_2TiO_5界面层;添加TiO_2的复合材料硬度和三点弯曲强度分别为39.0HRC,743.94MPa,比未添加TiO_2的复合材料分别提高了10.0%,26.4%;断口扫描表明,添加TiO_2的复合材料界面结合良好无裂纹,Al_2O_3颗粒表现为穿晶断裂。说明加入的TiO_2改善了Al_2O_(3p)/钢基复合材料界面结合强度,提高了复合材料力学性能。     

Removals of fly ash and NO in a fluidized-bed reactor with CuO/activated carbon catalysts

This study investigates the effects of fly ash compositions (SiO(2) and Al(2)O(3)), particle sizes (4-10 μm and 40 μm), and concentrations on the simultaneous removals of fly ash and NO using a fluidized-bed catalyst reactor. Experimental results show that the removal efficiencies of fly ash and NO at particle concentrations of 968-11,181 mg m(-3) are 71-97% and 42-57%, respectively. SiO(2) particles have more influences than Al(2)O(3) particles on the performances of fluidized-bed CuO/AC catalyst. As the concentration of fine particle increases, the pores and active sites on catalyst surface are obstructed and therefore the activities of catalysts are depressed.