磷酸根表面修饰对钨锆复合氧化物载铂催化剂的影响

用浸渍法制备了磷酸根表面修饰的钨锆复合氧化物载铂催化剂(Pt/PO43--WO3-ZrO_2)。用NH3-程序升温脱附(NH3-TPD)、红外光谱(FT-IR)、X-射线衍射(XRD)、N2物理吸附-脱附(BET)、H2-程序升温还原(H2-TPR)、H2-脉冲吸附和X射线光电子能谱(XPS)分析等技术对催化剂进行表征。用水热釜考察了钨锆复合氧化物的水热稳定性,固定床反应器考察了催化剂催化甘油氢解制1,3-丙二醇的反应性能。结果表明:引入适量磷酸根可抑制水热处理过程中钨锆复合氧化物单斜相ZrO_2向四方相转变,0.72 PO43--WO3-ZrO_2样品水热处理前比表面积83 m2×g-1,水热处理后比表面积86 m2×g-1,比表面积基本不变,提高了钨锆复合氧化物的水热稳定性。增强了催化剂金属还原性,提高了催化剂H2吸附量,Pt/PO43--WO3-ZrO_2催化甘油氢解稳定性较Pt/WO3-ZrO_2催化剂显著提高。     

非临氢条件下甘油氢解制1,2-丙二醇的研究

综述了非临氢条件下甘油氢解制1,2-丙二醇的研究进展,介绍了目前甘油原位加氢的2种途径(甘油液相重整加氢和甘油催化转移氢化反应)及优缺点,并对可能的甘油氢解机理进行了阐述。目前采用贵金属催化剂Pt/HT和Pd/Fe_2O_3以及非贵金属Cu/ZrO_2、复合金属Cu-Ni/Al_2O_3均能获得较高的1,2-丙二醇选择性(80%)。最后对非临氢条件下甘油原位加氢的研究工作进行了总结,并对未来研究方向做出展望。     

PtAu/ZrO_2催化甘油选择性制备乳酸

采用溶胶-沉积法制备了Pt Au/ZrO_2系列催化剂,在惰性气体气氛下用于催化甘油选择性制备乳酸。研究不同反应温度下,不同单金属负载和不同比例Pt Au双金属负载催化剂的催化活性以及不同气氛下催化剂重复使用性能,对催化剂进行BET、AAS和TEM等表征。结果表明,在浓度1.1 mol·L-1甘油水溶液10 m L、(1∶1)Pt Au/ZrO_2催化剂用量0.132 g、反应温度160℃、氮气压力1.4 MPa和反应时间6 h条件下,甘油转化率90%,乳酸选择性93.7%。催化剂重复使用性能实验验证了氧气气氛下催化剂活性保持良好。     

Pt/WO3-TiO2/ZrO2-Al2O3甘油加氢体系中Al2O3的双功能催化作用研究

考察了WO3-TiO2/ZrO2-Al2O3四元氧化物中ZrO2:Al2O3质量比对Pt-WO3体系对质量分数30%甘油水溶液氢解制备1,3-丙二醇催化性能的影响，揭示了Al2O3组分在四元氧化物体系中的双功能作用。N2物理吸附脱附(BET)、X射线衍射(XRD)、傅里叶变换CO吸附及吡啶吸附红外光谱(FT-IR)、透射电镜(TEM)、程序升温还原(H2-TPR)等表征结果表明，氧化铝的掺入量直接影响到制备过程中WOx、ZrO2、TiO2等氧化物的晶相结构，进而影响到负载Pt纳米与载体的相互作用。在固定床反应器中，Pt-WO3-TiO2/ZrO2-Al2O3催化剂(Pt质量分数2%)上甘油转化率随着Al2O3质量比的升高逐渐降低，当ZrO2/Al2O3质量比为9:1时，催化活性最高，甘油转化率为38%，1,3-PDO选择性为49%，催化剂可稳定运行不低于100小时。     

Pt-WOx系催化剂上甘油氢解制1,3-丙二醇的研究进展

生物柴油的发展对实现碳减排、推进能源替补具有重要科学意义，将生物柴油副产粗甘油进行绿色处理及高值转化，有利于促进生物柴油产业链的延伸发展。甘油氢解制备1,3-丙二醇已成为目前粗甘油高值化利用的研究热点，设计开发高活性、高选择性的催化剂是该过程的关键。本文首先阐述了Pt-WO_x系催化剂上甘油氢解制备1,3-丙二醇的脱水加氢机理、直接氢解机理以及氧化还原机理，明确了Pt-WO_x系催化剂中Pt分散度、WO_x状态和Pt-WO_x界面接触等是影响催化性能的主要因素，并对其进行综述；进一步分析Pt分散度、WO_x状态和PtWO_x界面接触的影响机制。Pt分散度会影响H₂的活化及反应中间体的氢化；WO_x状态与催化剂Br?nsted酸性位点密不可分，还可促进活性金属的分散；Pt-WO_x界面则影响催化剂氢溢流以及原位Br?nsted酸的生成。最后，提出今后应从这三方面构筑新型Pt-WO_x系催化...     

介孔铌钨氧化物担载Pt催化甘油氢解制备正丙醇

采用溶胶-凝胶法制备一系列不同摩尔含量比的介孔铌钨氧化物(Nb_xW_(10-x))作为载体,利用等体积浸渍法负载Pt的质量分数为2%,氯铂酸为前驱体溶液,制得催化剂Pt/Nb_xW_(10-x)。通过N_2物理吸附(BET),X-射线粉末衍射(XRD),氨气程序升温脱附(NH_3-TPD)、H_2脉冲吸附等方法表征催化剂的物理化学性质。用间歇式反应器考察催化剂对甘油氢解制备正丙醇反应的催化性能。结果表明,钨的引入可以显著提高甘油的转化率以及目标产物的选择性。当Nb/W为3:7时在反应温度220℃,氢气压力5.5 MPa,反应时间12h,甘油4g,水16g,催化剂1g时,用催化活性较好的2%Pt/Nb_3W_7作为催化剂催化甘油氢解,甘油的转化率为90.9%,正丙醇的选择性可达60.6%。     

Pt/H-MCM-22上共进料异丁烷对二甲醚制烃产物选择性的影响

在H-MCM-22和Pt/H-MCM-22分子筛上研究了二甲醚制烃催化性能,及采用异丁烷共进料时整体催化性能的改变,利用双循环机理和同系化反应路径解释了包括催化剂寿命、反应选择性和单位时间产物生成总量等的变化,同时采用X射线衍射、扫描电镜、氮吸附、氨气程序升温脱附、吡啶吸附红外光谱和Al核磁等对催化剂进行了表征。结果表明,共进料异丁烷增强了烯烃循环和芳烃循环,能有效改变二甲醚制烃过程产物选择性并可以缩短反应诱导期,但代价是加快催化剂失活。负载的Pt提供了额外的Lewis酸位,增强了氢转移反应、氢解反应和烷烃脱氢反应,同时缩短了催化剂寿命。     

负载型Pt-Ni双金属催化剂上甘油氢解反应性能

甘油氢解转化是获得高附加值化学品的主要途径之一。通过浸渍法制备了γ-Al2O3负载Pt-Ni双金属的甘油氢解催化剂。采用X射线衍射(XRD)、氮气物理吸附、透射电子显微镜(TEM)、程序升温还原(TPR)以及X射线能谱分析(XPS)等手段对催化剂进行了表征。结果表明:在γ-Al2O3负载的Pt-Ni双金属催化剂中,Pt原子与Ni原子之间发生了相互作用并形成了Pt Ni合金簇,使得Pt-Ni双金属催化剂产生了协同作用,对乙二醇的选择性大大高于Pt/γ-Al2O3和Ni/γ-Al2O3等单金属组分催化剂。固定床反应器实验结果表明,在473 K和3.0 MPa氢气压力下,负载量为2%Pt-15%Ni/γ-Al2O3催化剂对乙二醇的选择性最高,达到28.4%,此时甘油的转化率为94.8%,1,2-丙二醇的选择性为58.2%。     

甘油氢解Cu/Cr催化剂制备方法对性能的影响

Cu/Cr催化剂由于Cu对C—C键氢解活性很低,对C—O键氢解活性很高而成为甘油氢解制1,2-丙二醇效果最好的固体催化剂。采用5种方法制备了Cu/Cr催化剂,并用于甘油的催化氢解反应,发现Cu/Cr催化剂的制备方式极大地影响着其对甘油的催化氢解性能。以5种方法制备的Cu/Cr催化剂中,对甘油的催化氢解性能依次是:铜氨络合沉淀法Adkins法碳酸钠沉淀法硅藻土浸渍法干混法。运用XRD、TG、BET、FTIR、TPR等表征手段对制备的催化剂结构进行了表征,详细分析了不同方式制备的催化剂的结构差异,将催化剂的结构表征结果与催化反应性能进行关联分析和讨论,并从理论上解释了催化剂结构差异和催化氢解性能的关系。     

甘油氢解制备1,2-丙二醇催化剂的研究进展

由于生物柴油产业的蓬勃发展而造成副产物甘油的大量过剩,迫使人们努力寻求甘油转化为高附加价值产物的有效途径。本文综述了国内外甘油氢解制1,2-丙二醇催化剂以及机理研究的新进展。指出催化剂是甘油氢解制1,2-丙二醇的关键因素,目前甘油氢解反应中以Cu、Ni、Ru、Pt、Rh基催化剂使用较多,其中Cu基催化剂的研究最为广泛,载体、助剂、制备方法、反应溶剂、甘油氢解条件等对Cu基催化剂的活性、选择性、寿命、产物分离难度等具有较大影响。为进一步改善催化剂的综合性能,需要加强对甘油氢解机理和催化剂制备技术的基础性研究。多金属催化剂、复合多功能催化剂和甘油原位氢解反应因其自身优势颇受关注,而催化剂的失活机理及再生性能考察是值得深入研究的新课题。     

Microstructural Analysis in Processing of the High-Tc Superconductor Ba2YCu3O7-x in Air

In the synthesis of the superconducting compound Ba₂YCu₃O_7-x from a stoichiometric mixture containing BaCO₃, Y₂O₃, and CuO In air, a low-melting liquid phase is formed at about 890°C. The liquid phase was identified as a ternary eutectic located within the compatibility triangle Ba₂YCu₃O_7-x–BaCuO₂–CuO. The implication of this finding for the processing of Ba₂YCu₃O_7-x is discussed.     

Tribocorrosion behaviour of TiCxOy thin films in bio-fluids

Decorative coatings require not only an attractive appearance for market applications, but also an ability to protect the surface underneath. Because of this, corrosion, wear and their combined effects (termed tribocorrosion) are particularly important for lifetime prediction. In this paper, the tribocorrosion behaviour of a range of single layered titanium oxycarbide, TiC_xO_y, coatings, produced by DC reactive magnetron sputtering, has been studied and reported as a function of electrode potential and applied load. The study was conducted in a reciprocating sliding tribo-system (Plint TE 67/E) in a bio-fluid (an artificial perspiration solution) at room temperature. During the wear tests, both the open-circuit potential and the corrosion current were monitored. The results showed that electrode potential and load have a significant influence on the total material loss. The variations in R_p (polarization resistance) and C_f (capacitance) before and after sliding, obtained by Electrochemical Impedance Spectroscopy (EIS) were evaluated in order to provide an understanding of the resistance of the film in such conditions. Tribocorrosion maps were generated, based on the results, indicating the change in mechanisms of the tribological and corrosion parameters for such coatings, as a function of load and applied potential.     

Reactivity of Mg-Ba catalyst in NOx storage/reduction

A new catalyst for NO_x storage/reduction was prepared to improve the activity of Ba-Pt/γ-Al₂O₃ by replacing Ba with a mixture of Ba and Mg. The catalyst was prepared by impregnating 1 wt.% Pt and then the alkaline-earth metals (Mg, Ba) on commercial γ-Al₂O₃. The tests have been carried out in a wide temperature range (ca. 200–400 °C) in order to understand the role of the mixture of alkaline-earth metals as a function of temperature. The behaviour of the two catalysts was different and indicated a synergetic effect between Mg and Ba.     

Localization of Potassium in Al2O3

The accommodation of small amounts of intentionally added potassium in sintered and hot–pressed polycrystalline α-alumina was studied. In sintered specimens, potassium was pushed out by, and accumulated along, the grain boundaries enclosing abnormally large α-alumina grains. Potassium was also localized in hot-pressed specimens and formed large (up to 1-mm diameter), randomly dispersed precipitates of polycrystalline potassium β-alumina. Each precipitate was enclosed within a thin shell (0.5– to 1.5-mm radius) of potassium–rich material. The experimental observations of this precipitation are compared to the formation of Liesegang rings.     

Solubility of KUO3 in BaUO3

The formation of a solid solution between cubic perovskne-type KUO₃ and pseudocubic BaUO₃ was investigated. The reaction begins at 550°C, and the solubility of KUO₃ reaches more than 30 mol% KUO₃ in BaUO₃ at 750°C. The region in which a single-phase solid solution exists was determined. The variation of the lattice parameter of the reacted samples was caused by solid solution formation and by oxygen absorption. The electrical conductivities of the samples varied with composition and showed a distinct maximum. The activation energy for electric conduction was very low compared to that for UO_z+x, or U₃O₈.     

Formation of ZnAl2O4 in the Presence of Cl2

The formation of ZnAl₂O₄ spinel in diffusion couples of Al₂O₃ and ZnO was investigated between 1000° and 1390°C in air and in air containing 4.8 vol% Cl₂ by X-ray diffraction, electron probe microanalysis, and scanning electron microscopy. The rate of formation of a spinel layer obeyed a parabolic rate law and was accelerated remarkably by the presence of Cl₂. The interdiffusion coefficient, , and the activation energy, E, were calculated to be 10⁻⁸ to 10⁻⁹ cm²/s and 123 kcal/mol (514 kJ/mol) in air and 10⁻⁷ cm²/s and 31 kcal/mol (130 kJ/mol) in air containing 4.8 vol% Cl₂, respectively.     

Formation of BaTiO3 from BaCO3 and TiO2 in Air and in CO2

The formation of BaTiO₃ from equimolar BaCO₃ and TiO₂ (rutile) mixtures was studied in air and in CO₂. A small amount of BaTiO₃ is formed first directly from BaCO₃ and TiO₂ at the surface of contact. From then on it is a diffusion-controlled reaction, and both BaTiO₃ and Ba₂TiO₄ are produced, with Ba₂TiO₄ being formed in much larger amounts. In 1 atmosphere of CO₂, the intermediate Ba₂TiO₄ was suppressed up to a temperature of about 1100°C. in agreement with thermodynamic calculations. Ba₂TiO₄ reacts fast with 1 atmosphere of CO₂ below about 1100°C. to produce BaTiO₃and BaCO₃     

Solubility of TiO2 in ZrO2

The solubility of TiO₂ in tetragonal ZrO₂ is 13.8±0.3 mol% ui 1300°C, 14.9±0.2 mol% at 1400°C, and 16.1±0.2 mol% at 1500°C. These solid solutions transform to metastable monoclinic solid solutions without compositional change on cooling to room temperature.     

Solubility of NiO in Al2O3

Solubility of NiO in Al₂O₃ was determined by electron probe microanalysisy A diffusion couple method was used by coupling an NiO-doped Al₂O₃ polycrystal to a pure single crystal of Al₂O₃. The solubility of NiO in Al₂O₃ in air was 230 wt ppm (157 at. ppm of cations) and 170 wt ppm (116 at. ppm) at 2073 and 1973 K, respectively. The solubility of NiO in Al₂O₃ obtained in this work was compared with our previous work of the solubility of MgO in Al₂o₃.