整体式Pt基催化剂上CH4选择性催化还原NO的研究

以La-Al2O3(La稳定的γ-Al2O3)、Ce0.63Zr0.37O2(OSM1)及Ce0.5Zr0.3Mn0.2O2(OSM2)为载体, Pt为活性组分, 制备了Pt质量分数为1%的整体式催化剂. 研究了不同载体负载的催化剂对CH4选择催化还原NO反应的性能, 并利用XRD、H2-TPR和XPS对催化剂进行了表征. 结果表明, Pt/OSM1和Pt/OSM2催化剂在氧含量为0.8%时对CH4催化还原NO具有优异的净化性能, Pt/OSM1催化剂上500 ℃时, CH4和NO均达到100%转化; Pt/OSM2催化剂上500 ℃时, CH4和NO的转化率分别达到73%和100%; 而 Pt/ La-Al2O3催化剂只在O2含量较低时(0.4%以下)具有较好活性, 500 ℃以上才可使CH4和NO完全转化. H2-TPR结果表明, Pt与OSM1和OSM2存在的相互作用导致低温还原物相生成. Pt与OSM的相互作用及OSM的储氧性能使催化剂在过量氧存在下对CH4催化还原NO具有优异性能.     

预处理条件对Pt/Al2O3催化还原NO的活性影响

用溶胶-凝胶法制备Al2O3载体,浸渍法制备质量分数为0.5%的Pt/Al2O3催化剂.研究焙烧气氛和温度对选择性催化还原NO反应活性和Pt价态的影响.结果表明,H2焙烧的活性温度区间最宽,随着焙烧温度的升高,温度区间变化很小,523K下O2焙烧的催化剂活性最好,且活性区间向高温方向移动.活性现象用程序升温脱附实验(NO-TPD,NO-O2-TPD)进行了解释.XPS研究表明,523K下O2用焙烧Pt的主要价态是Pt2+,而523K下H2和N2焙烧Pt的主要价态为Pt0.     

MnO2-CeO2/Ti0.25Zr0.25Al0.5O1.75整体式催化剂的低温NH3选择性催化还原NO性能研究

采用共沉淀法制备了TiO2、Ti0.5Zr0.5O2(TZ)和Ti0.25Zr0.25Al0.5O1.75载体材料,并以MnO2和CeO2为活性组分,以T、TZ和TZA为载体,制备了3种整体式催化剂.对催化剂进行了低温N2吸附脱附、储氧量(OSC)、NH3-TPD和XPS的表征,并研究了3种催化剂在过量O2存在下的低温NH3-选择催化还原(NH3-SCR)活性及其抗H2O和SO2性能.结果指出,MnO2-CeO2/Ti0.25Zr0.25Al0.5O1.75(TZAC)有最大的比表面积、孔容和储氧能力、最强的表面酸性和最大的表面酸量.而这对选择催化还原(SCR)反应至关重要.活性测试结果指出,TZAC有最好的低温SCR活性和最宽的活性温度窗口.NO在102℃起燃(转化率为50%),在175～325℃之间NO转化率接近100%,而且TZAC表现出了较强的抗H2O和SO2性能.     

前驱体对Ba/(Pt/γ-Al2O3)催化剂NOx存储性能的影响

分别以Ba(NO3)2和Ba(CH3COO)2为Ba的前驱体,利用浸渍法制备了两个系列不同Ba含量的NOx存储还原催化剂Ba/(Pt/γ-Al2O3).采用X射线衍射、X射线光电子能谱、程序升温反应脱附和差热-热重等分析技术对样品进行了表征,并考察了催化剂的NOx存储性能.结果表明,不同前驱体在Pt/γ-Al2O3载体表面的分散能力不同.前驱体为Ba(NO3)2时,Ba的分散阈值为0.047 g/g(Ba/(Pt/γ-Al2O3)质量比),而前驱体为Ba(CH3COO)2时,Ba的分散阈值为0.149 g/g(Ba/(Pt/γ-Al2O3)质量比).经高温焙烧后,前驱体的分散容量决定催化剂中Ba物种的分散容量.在NOx存储性能评价实验中,以Ba(CH3COO)2为前驱体时,催化剂的NOx等温吸附穿透时间最长为23 min,而以Ba(NO3)2为前驱体时,具有相同Ba含量的催化剂的穿透时间为13 min.因此,在制备NOx存储还原催化剂时,选择易分散的前驱体Ba(CH3COO)2可以获得较高的NOx存储活性的催化剂.     

高性能汽车尾气净化催化剂的制备

 采用浸渍法制备了Pt/γ-Al2O3和Rh/CeO2-ZrO2-Y2O3,然后将两者按一定的比例混合制江涂覆在蜂窝载体上制得整体式催化剂,用汽车尾气模拟气对催化剂的性能进行了评价. 结果表明,Pt/γ-Al2O3催化剂中引入Rh/CeO2-ZrO2-Y2O3组分后极大地提高了催化剂的低温活性和热稳定性,催化剂的起燃温度仅为240 ℃; 在900 ℃水热老化后,催化剂的起燃温度仅升高约20%. 这说明Pt/γ-Al2O3与Rh/CeO2-ZrO2-Y2O3之间存在一定的协同效应.     

高比表面积铝土矿载体的制备及在CO氧化反应中的应用

采用水热法,对天然铝土矿进行改性,获得高比表面积的铝土矿载体(Bauxite)。用等体积浸渍法制备了不同Pt含量的Pt/bauxite和1.0%Pt/Al2O3催化剂,以CO氧化为探针反应,考察了催化剂性能。采用XRF、XRD、低温N2-物理吸附、H2-TPR以及CO-TPD等对载体和催化剂样品进行表征。结果表明:Pt/bauxite催化剂具有优异的CO氧化性能,特别是当反应温度为200℃时,催化剂1.0%Pt/bauxite的CO转化率为93.4%,而1.0%Pt/Al2O3CO转化率仅为9.4%。其原因是铝土矿含有的Fe2O3是CO氧化反应的催化剂,且Fe2O3与负载的Pt之间发生了相互作用,降低了Pt和Fe2O3还原温度,提高了对CO的吸附能力且降低了CO的脱附温度,进而提高了催化剂的CO氧化反应性能。     

微乳液法制备Pt-S2O82-/ZrO2-Al2O3型固体超强酸催化剂及其异构化性能

采用微乳液法负载Pt制备了Pt-S2O82-/ZrO2-Al2O3(Pt-SZA-M)固体超强酸催化剂, 以正戊烷异构化反应为探针, 对比了微乳液法和浸渍法负载Pt制备的催化剂(Pt-SZA)的异构化性能, 并采用XRD, FTIR, BET, TG-DTA, TPR和TEM对催化剂进行了表征. 结果表明, 与Pt-SZA催化剂相比, Pt-SZA-M催化剂中Pt粒子的粒径更小(4.5 nm)且尺寸更均一; Pt-SZA-M催化剂的比表面积(109.6 m2/g)比Pt-SZA催化剂(95.0 m2/g)增加了15.4%. Pt-SZA-M催化剂的初始还原温度比Pt-SZA催化剂降低了10~20℃, 表明微乳液法负载Pt可以提高催化剂的氧化活性, 提高氢分子在催化剂上的吸附解离能力. 异构化活性实验结果表明, 与Pt-SZA催化剂相比, Pt-SZA-M催化剂的低温活性得到明显改善, 在反应压力为2.0 MPa、 氢烃摩尔比为4: 1、 质量空速为1.0 h-1的条件下, Pt-SZA-M催化剂在反应温度为230℃时活性达到60.8%, 在100 h内异戊烷的收率可稳定在58.0%左右, 选择性在95.0%以上.     

Pt/CeO_2催化剂上甲醛催化氧化

以CeO2为载体,采用浸渍法制备了负载型Pt催化剂用于低温甲醛氧化反应,考察了Pt前驱体及Pt负载量等因素对催化性能的影响。XRD,TEM和CO化学吸附表征结果表明Pt粒子在载体上高度分散。反应结果表明,以Pt(NO3)2为前驱体比H2PtC l6为前驱体制备的催化剂表现出更好的反应性能,C l-离子的存在降低了催化剂的氧化还原能力,从而抑制了催化活性。此外,催化剂的活性随着Pt负载量的增加而增强,其中Pt负载量为3%时催化剂在30℃时甲醛转化率仍在80%以上。     

二甲醚部分氧化重整制氢中的部分氧化催化剂的考察

采用浸渍法制备了一系列负载型贵金属催化剂,与Ni/Al2O3构成双床层催化剂,在连续流动固定床反应器中,进行了二甲醚(DME)部分氧化重整制氢的研究,系统地考察了贵金属类型及其负载量、载体以及还原温度与反应温度的影响.结果表明,Pd/Al2O3催化性能不及Pt/Al2O3和Rh/Al2O3,而Pt/Al2O3和Rh/Al2O3催化性能相当,考虑到价格因素,选择了Pt/Al2O3作为本反应催化剂.对Pt负载量的考察表明,0.5%Pt/Al2O3催化性能最佳,且Al2O3又比MgO和ZrO2更适合作载体.通过对工艺条件的考察,确定适当的还原温度与反应温度均为700℃.在上述最佳催化剂与反应条件下,DME转化率保持在100%,H2收率可达80%.     

Pt/Al2O3/WO3/ZrO2催化剂对正己烷异构化反应的催化性能

 通过浸渍法制备了系列Pt/Al2O3/WO3/ZrO2催化剂样品,采用X射线衍射、傅里叶变换红外光谱和程序升温还原等方法表征了催化剂的结构、表面酸性和氧化还原性能,考察了不同反应条件下催化剂对正己烷异构化反应的催化性能. 结果表明, Pt的加入显著改变了WO3/ZrO2载体的氧化还原性,并使催化剂由单一的酸中心催化变成由酸中心与金属中心共同催化; Al2O3的加入增强了WO3与ZrO2之间的相互作用,增加了催化剂的Lewis酸位. 在n(H2)/n(n-C6H14)=1.5, WHSV=0.7 h-1, m(cat)=2.0 g, p=1.0 MPa, θ=220 ℃和t=3 h的反应条件下, Pt/Al2O3/WO3/ZrO2催化剂上正己烷的转化率和2,2-二甲基丁烷的选择性分别达到84.9%和22.9%,裂解反应产物的收率低于1.5%. 经 1000 h的寿命试验,催化剂没有出现失活.     

Solvent extraction separation of In/III/-Tl/III/ and Hg/II/-Cd/II/-Co/II/ with sulphoxides

Solvent extraction studies have been made on some metals: In/III/-Tl/III/ and Hg/II/-Cd/II/-Co/II/, from ammonium thiocyanate solutions by dialkyl sulphoxides. Separation of these metals from one another can be achieved by suitable choice of the extracted conditions. The nature of the extractable metal species has been elucidated.     

Synthesis of chlorobis/β-diketonato/oxotechnetium/V/ and tris/β-diketonato/technetium/III/ complexes

Chlorobis/-diketonato/ oxotechnetium/V/ complexes [TcOCl/-dik/₂, -diketone=acetylacetone, benzoylacetone and dibenzoylmethane] were newly synthesized using macroamount of⁹⁹Tc. These complexes were further separated into geometrical isomers. Furthermore, an improvement of the yields for the syntheses of tris/-dike-tonato/technetium/III/ complexes [Tc/-dik/₃, -diketone=acetylacetone, benzoylacetone and 2-thenoyltrifluoroacetone] was examined using Tc/III/-thiourea complexes as a starting material.     

Simultaneous propane dehydrogenation andco2hydrogenation overCrOx/SiO2catalyst

Summary Single reverse water-gas shift (RWGS) and dehydrogenation of propane with CO₂(DH-CO₂) reactions in the presence and absence of the CrO_x/SiO₂ catalyst have been studied between 673 and 873 K. It was found that the CrO_x/SiO₂ catalyst is active both in the dehydrogenation of propane and in the RWGS reactions. The obtained results suggest that the dehydrogenation of propane to propene in the presence of CO₂on CrO_x/SiO₂can be facilitated by the RWGS reaction.</o:p>     

Direct synthesis of dimethyl carbonate ?from CH3OH AND CO2 by H3PW12O40/CexTi1-xO2 catalyst

Summary Ce_xTi_1-xO₂ and H₃PW₁₂O₄₀/Ce_xTi_1-xO₂ catalysts were prepared using a sol-gel method, and applied to the direct synthesis of dimethyl carbonate from methanol and carbon dioxide. H₃PW₁₂O₄₀/Ce_xTi_1-xO₂ showed a better catalytic performance than the corresponding Ce_xTi_1-xO₂, due to the bifunctional catalysis of Br?nsted acid sites (provided by H₃PW₁₂O₄₀) and base sites (provided by Ce_xTi_1-xO₂). H₃PW₁₂O₄₀/Ce_0.1Ti_0.9O₂ showed the highest catalytic performance among the H₃PW₁₂O₄₀/Ce_xTi_1-xO₂ catalysts.     

An investigation of the promotional effect of propylene or propane traces on the activity of sulfatedPt/g-Al2O3andPt-Sn/g-Al2O3inCH4combustion

Summary A strong promoting effect of the presence of C₃H₈or C₃H₆was determined for the combustion of CH₄in excess oxygen, over pre-sulfated 1%Pt/g-Al₂O₃and pre-sulfated 1%Pt-2%Sn/g-Al₂O₃catalysts.</o:p>     

Crystal structure of Na3PO4 · 12H2O

The crystal structure of trisodium monophosphate hemihydrate was determined. The space group is $\text{C2}\text{c}$ and a unit cell contains eight formula units. The unit cell dimensions of $\text{Na}{}_3\text{PO}{}_4\text{·}\text{1}\text{2}\text{H}{}_2\text{O}$ are a = 9.631(3), b = 5.416(2), c = 16.938(8) Å, β = 102.60(5)°. The final R value is 0.027 for a set of 1430 independent reflections. This atomic arrangement is mainly a three-dimensional network of distorted NaO₆ octahedra. The hydrogen bonding scheme is given.     

LixNi0.8-yCo0.2ZnyOp的合成及电化学性能研究

A series of single-phase Li_xNi_0.8-yCo_0.2Zn_yO_p(0.96 ≤x≤ 1.10， 0 ≤y≤ 0.05， 2 ≤p≤ 2(1+y) ) (different in the y values) were synthesized by a two-step solid state reaction method， in which LiOH·H₂O， Zn-doped spherical Ni(OH)₂ and Co₂O₃ were used as the precursors. The ICP-AES analyses proved that the Zn-doped compounds synthesized had the nonstoichiometric form. The results of the XRD， SEM identified that the uniform particles of the as-prepared materials having a good layered structure were fine， narrowly distributed and well crystallized. The electrochemical performance test was carried out and the results showed that the as-prepared Zn-doped materials had not only a high capacity， but also a better cycling stability characterization than the un-doped one. The Li_1.06Ni_0.75Co_0.22Zn_0.03O_2.03 material has an initial reversible capacity as high as 160.5mAh·g^-1; and a first discharge efficiency 89.2%， and exhibits satisfactory cyclic stability with 90% retainable capacity after 50 cycles.     

Visible light-sensitive yellow TiO2−xNx and Fe-N co-doped Ti1−yFeyO2−xNx anatase photocatalysts

Nitrogen substituted yellow colored anatase TiO_2−xN_x and Fe-N co-doped Ti_1−yFe_yO_2−xN_x have been easily synthesized by novel hydrazine method. White anatase TiO_2−δ and N/Fe-N-doped samples are semiconducting and the presence of ESR signals at g ∼1.994-2.0025 supports the oxygen vacancy and g∼4.3 indicates Fe³⁺ in the lattice. TiO_2−xN_x has higher conductivity than TiO_2−x and Fe/Fe-N-doped anatase and the UV absorption edge of white TiO_2−x extends in the visible region in N, Fe and Fe-N co-doped TiO₂, which show, respectively, two band gaps at ∼3.25/2.63, ∼3.31/2.44 and 2.8/2.44 eV. An activation energy of ∼1.8 eV is observed in Arrhenius log resistivity vs. 1/T plots for all samples. All TiO₂ and Fe-doped TiO₂ show low 2-propanol photodegradation activity but have significant NO photodestruction capability, both in UV and visible regions, while standard Degussa P-25 is incapable in destroying NO in the visible region The mid-gap levels that these N and Fe-N-doped TiO₂ consist may cause this discrepancy in their photocatalytic activities.     

Synthesis and characterization of Ti1−2xNbxNixO2−x/2 solid solutions

Doped-rutile has been traditionally used in ceramic pigments for its intense optical properties. In this paper, we compare the classical ceramic synthesis of Ti_1−2xNb_xNi_xO_2−x/2 system with the sol-gel methodology, which allows a reduction of the anatase-rutile transformation temperature. The composition was optimised in order to obtain a unique rutile phase with the minimum amount of pollutant Ni(II) and enhanced chromatic coordinates. Incorporation of the doping ions in the rutile structure was corroborated by XRD and Rietveld refinements. The species responsible for the colour mechanism were studied by different techniques. UV-VIS spectroscopy showed the characteristic features of Ni²⁺ ions, whose existence was corroborated by EPR and magnetic measurements. From these results, (Ni,Nb)doped-TiO₂ powder samples can be now shaped as thin films, monoliths, etc. by using sol-gel methodology without modifying their properties. This study introduces new possibilities of coloured TiO₂-based solid solutions in new combined advanced applications (colouring agent and photocatalyst, etc.).     

Carbon black and propylene oxidation over Ru/CoxMgyAl2Oz catalysts

The effects of Co_xMg_yAl₂O_z mixed oxides composition and ruthenium addition on the oxidation of propylene and carbon black (CB) were investigated. Different reactive cobalt and ruthenium oxide species were formed following calcination at 600 °C. The addition of ruthenium was beneficial for the CB oxidation under “loose contact” conditions and for propylene oxidation when the cobalt content was intermediate to low. The calculated activation energy for CB oxidation was decreased from 151 kJ mol⁻¹ for the uncatalyzed reaction to 111 kJ mol⁻¹ over the best catalyst.