CeO2-MOx（M=La^3＋,Ca^2＋）改性Pd/γ-Al2O3催化甲烷燃烧性能

采用沉积-沉淀法制备了固溶体CeO2-MOx=(M=La3+,Ca2+)改性的Pd/γ-Al2O3催化剂,利用XRD、Raman和XPS对催化剂进行了表征.结果表明,金属(M)离子进入CeO2的晶格,形成CeO2-MOx固溶体,Raman谱上463cm-1处对应于Ce-O键的F2g对称伸缩振动强度降低.其中,样品Pd/γ-Al2O3CeO2-CaO在615 cm-1处出现一小峰,样品Pd/γ-Al2O3-CeO2-La2O3在320cm-1处出现的肩峰,都表明固溶体CeO2-MOx的形成使O2-亚晶格结构对称性降低.XPS分析表明,固溶体改性的Pd/γ-Al2O3催化剂中Pd的3d5/2结合能比正常价态的PdO的结合能高出0.5-0.6 eV,形成了一种高度离子化的.与载体具有强相互作用的Pd物种.催化甲烷燃烧实验证明,固溶体CeO2-MOx(M=La3+,Ca2+)改性的Pd/γ-Al2O3催化剂的低温活性和稳定性均高于未经改性的Pd/γ-Al2O3催化剂和仅用CeO2改性的Pd/γAl2O3催化剂,在空速为50000 h-1时,可使1%CH4-99%空气(体积分数)混合气中甲烷的10%转化温度降至254℃,转化率100%时的转化温度降至340℃.     

CeO2和Pd在Ni/γ-Al2O3催化剂中的助剂作用

采用脉冲微反技术研究了添加n型半导体氧化物CeO2及贵金属Pd对Ni/γ-Al2O3催化剂上CH4积炭/CO2消炭反应性能的影响,并运用BET、TPR、CO2-TPSR及氢吸附等技术对催化剂进行了表征.结果表明,n型半导体氧化物CeO2的添加可以降低Ni/γ-Al2O3催化剂上CH4裂解积炭活性,提高CO2消炭活性,添加少量贵金属Pd可以进一步改变载体Al2O3、助剂CeO2和活性组分Ni之间的相互作用,从而改善Ni/γ-Al2O3催化剂的抗积炭性能.通过Ni-Ce-Pd/γ-Al2O3催化剂上CH4积炭/CO2消炭模型对上述作用机制作出了新的解释.     

铈和镧改性γ-Al2O3担载Pd催化剂的结构效应

分别以镧-铈、铈-镧顺序浸渍和镧铈共浸渍的方式在γ-Al2O3载体上引入助剂La2O3和CeO2,然后担载Pd制备了一系列催化剂.以甲醇分解为探针反应,采用XRD、EXAFS和XPS对催化剂的体相和表面结构进行表征,用BET法测定比表面积,并进行了吸附态CO的FTIR研究.结果表明,La2O3容易进入CeO2的晶格中,促进了CeO2在γ-Al2O3上的分散.但不同的La2O3、CeO2加入方式对活性组分Pd在改性载体上的分散度、优势暴露面及其与CeO2之间的相互作用产生不同的影响.关联甲醇分解性能测试结果说明,Pd在载体上的高度分散以及Pd和CeO2之间通过界面产生的强相互作用是催化剂具有高活性的关键.     

铈和镧改性γ-Al2O3担载Pd催化剂的结构效应

分别以镧-铈、铈-镧顺序浸渍和镧铈共浸渍的方式在γ-Al2O3载体上引入助剂La2O3和CeO2，然后担载Pd制备了一系列催化剂.以甲醇分解为探针反应，采用XRD、EXAFS和XPS对催化剂的体相和表面结构进行表征，用BET法测定比表面积，并进行了吸附态CO的FTIR研究.结果表明,La2O3容易进入CeO2的晶格中，促进了CeO2在γ-Al2O3上的分散.但不同的La2O3、CeO2加入方式对活性组分Pd在改性载体上的分散度、优势暴露面及其与CeO2之间的相互作用产生不同的影响.关联甲醇分解性能测试结果说明,Pd在载体上的高度分散以及Pd和CeO2之间通过界面产生的强相互作用是催化剂具有高活性的关键.     

CeO2和La2O3改性Pd/γ-Al2O3甲醇低温分解催化剂的研究 Ⅰ. CeO2改性Pd/γ -Al2O3催化剂的结构和性能

 用XRD,BET,NH3－TPD,TPR及XPS等手段对CeO2改性Pd／γ－Al2O3催化剂的结构和性能进行了表征,并考察了催化剂上甲醇低温分解的性能．结果表明,CeO2在γ－Al2O3载体上容易聚集,不能完全掩蔽其表面酸性,并较大程度地降低了载体的比表面积;CeO2的加入促进了Pd在载体上的分散,并且产生一种协同还原作用．Pd的高度分散及其与CeO2在γ－Al2O3上的相互作用是催化剂具有高活性的关键．     

Pd/MnOx+Pd/γ-Al2O3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。     

稀土改性Pd/Al2O3催化剂的性能:甲醇分解的活性和选择性

用稀土金属氧化物CeO2和La2O3改性γ-Al2O3担载Pd制备了一系列甲醇分解催化剂，并考察了Pd盐前驱体（氯盐或硝酸盐），稀土种类（镧或／和铈），经的含量（0％－30％），浸渍方法（顺序浸渍或共浸渍）地催化剂性能的影响。结果表明：CeO2能提高Pd/Al2O3催化剂的甲醇分解活性，La2O3能提高催化剂的CO和H2选择性，而CeO2和La2O3在γ-Al2O3上对Pd的催化性能表现出一种协同作用。在10％的La2O3和22％的CeO2共同改性的催化剂上，250℃，甲醇液体空速1.8h^-1条件下反应甲醇转化率达到91．4％，CO（H2）的选择性几乎为100％。     

Mn修饰Al2O3载体负载Pd催化剂及其蒽醌加氢催化性能

以活性氧化铝(γ-Al2O3)为载体,分别以Mn(NO3)2溶液和酸性氯化钯(PdCl2)溶液为修饰组分和活性组分前体,采用分步浸渍法制备了Mn修饰Al2O3载体负载钯催化剂。将催化剂应用于蒽醌加氢反应,考察了催化剂制备方法、活性组分负载量和催化剂还原温度对反应效果的影响。用XRD、BET、XPS和TPR对催化剂进行了表征。结果表明,催化剂活性受到制备方法的影响,在对Mn修饰Al2O3载体进行焙烧,Pd负载量0.2(wt)%、还原温度300℃的条件下,催化剂蒽醌加氢活性较高,较未修饰的催化剂提高了约16%。催化剂中Mn以MnO的形式存在,影响了γ-Al2O3的组织结构,使载体与活性组分之间的作用力增强,活性组分Pd高度分散在催化剂表面,从而提高了催化剂的活性。     

焙烧温度对CuO/γ-Al2O3和CeO2-CuO/γ-Al2O3催化剂NO还原活性的影响

用浸渍法制备了CuO/γ-Al2O3催化剂和CeO2改性的CeO2-CuO/γ-Al2O3催化剂,考察了焙烧温度对CuO/γ-Al2O3和CeO2-CuO/γ-Al2O3催化剂C3H6还原NO反应活性的影响,以及CeO2的添加量对CeO2-CuO/γ-Al2O3催化剂C3H6还原NO反应活性的影响。结果表明,在200 ℃～500 ℃的焙烧温度范围内,焙烧温度对CuO/γ-Al2O3催化剂的活性影响很小；在500 ℃～800 ℃的焙烧温度范围内,随着焙烧温度的升高CuO/γ-Al2O3催化剂的活性急剧下降,由XRD物相测定结果可知,归因于对反应表现惰性的尖晶石CuAl2O4相的生成。当焙烧温度为500 ℃时,CeO2的添加对CuO/γ-Al2O3催化剂的活性影响很小；当焙烧温度为800 ℃时,CeO2的添加对CuO/γ-Al2O3催化剂有明显的助催化作用,当Ce和Cu的摩尔比为1∶10时,NO转化率较为理想。     

CeO2和La2O3改性Pd/γ-Al2O3甲醇低温分解催化剂的研究 Ⅱ. La2O3对Pd/CeO2/γ-Al2O3催化剂的结构和性能的影响

 在Pd／CeO2／γ－Al2O3中进一步添加La2O3,并考察了其催化甲醇分解性能．结果表明：La2O3的加入抑制了副产物二甲醚的生成;随着La2O3含量的增加,催化剂活性先降低后升高,w（La2O3）＝10％时甲醇转化率达到极大值（约91．4％）．XRD,BET,NH3－TPD,XPS,H2－TPR和FT－IR等表征结果表明：La2O3自身在γ－Al2O3载体上的分散性很好,并且促进了CeO2在γ－Al2O3载体上的分散及其体相氧的还原,使Pd的分散度进一步提高,并使Pd和CeO2之间的相互作用进一步增强,从而提高了催化剂催化甲醇分解的活性．     

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.     

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.     

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>     

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>     

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.     

Oxygen defect K2NiF4-type oxides: The compounds La2−xSrxCuO4−x2+δ

Oxygen defect K₂NiF₄-type oxides $\text{La}{}_{\mathrm{2?x}}\text{Sr}{}_{\mathrm{x}}\text{CuO}{}_{\mathrm{<mtext>4?</mtext><mtext>x</mtext><mtext>2</mtext><mtext>+\delta </mtext>}}$ have been synthesized for a wide composition range: 0 ≤ x ≤ 1.34. From the X-ray and electron diffraction study three domains have been characterized: orthorhombic compounds with La₂CuO₄ structure for 0 ≤ x < 0.10, tetragonal oxides similar to LaSrCuO₄ for 0.10 ≤ x < 1 and several superstructures derived from the tetragonal cell ( with n = 3, 4, 4.5, 5, 6) for 1 ≤ x ≤ 1.34. The compounds corresponding to 0 < x < 1 differ from the other oxides in that they are characterized by the presence of copper with two oxidation states: + 2 and + 3. A model structure for La_0.8Sr_1.2CuλO_3.4, in which copper has only the + 2 oxidation state, and for which the actual cell is tegragonal—a = 18.80₄ Å and c = 12.94 Å—has been established. The particular structural evolution of these compounds is discussed in terms of a competition between the capability of Cu(II) to be oxidized to Cu(III) and the ordering of oxygen vacancies.     

A study of the spinel materials LiTi2O4 and Li43Ti53O4 by photoelectron spectroscopy

HeI-excited valence-band ultraviolet photoelectron spectra and MgKα-excited Ti-2p X-ray photoelectron spectra are reported for the spinel materials LiTi₂O₄ and $\text{Li}{}_{\mathrm{<mtext>4</mtext><mtext>3</mtext>}}\text{Ti}{}_{\mathrm{<mtext>5</mtext><mtext>3</mtext>}}\text{O}{}_4$. The presence of a Fermi edge in the ultraviolet photoelectron spectrum of LiTi₂O₄ confirms the metallic nature of this material, although the measured density of states at the Fermi energy is much lower than that expected from an independent-electron interpretation of the magnetic susceptibility. This difference is attributed to a strong interaction of the conduction electrons with the lattice vibrations. The localization of conduction electrons that occurs in the final state in the Ti-2p X-ray photoelectron spectrum of LiTi₂O₄ is attributed to a Coulomb interaction with a core hole.     

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.