Mn/Ti-Zr复合氧化物催化苯甲酸甲酯选择性加氢

以硝酸锆和钛酸四丁酯为原料,采用共沉淀法制备Ti-Zr-O氧化物载体,采用浸渍法制备了Mn/Ti-Zr催化剂;采用XRD、N2物理吸附、H2-TPR、NH3-TPD和TG-DTA对Mn/Ti-Zr催化剂进行了表征,并考察了催化剂组成、结构和反应条件对苯甲酸甲酯（MB）加氢性能的影响,以及催化剂的长周期稳定性、失活和再生行为。结果表明：TiO2含量和Mn负载量分别为12% 和8% （二者均以Ti-Zr-O氧化物的质量为基准,下同）时制备的Mn/Ti-Zr催化剂性能最优,该催化剂在θ = 390 ℃, p = 1.0 MPa,n(H2)∶n(MB) = 9∶1和重时空速（WHSV）= 0.5 h-1的优化条件能够实现98.0% 的苯甲酸甲酯转化率和89.7%的苯甲醛和苯甲醇选择性;苯甲酸甲酯加氢反应的活性和选择性分别与Mn/Ti-Zr表面MnOx物种的氧化还原性和催化剂的酸性密切相关。此外,Mn/Ti-Zr催化剂具有良好的结构稳定性,在反应1000 h后仅因积碳而丧失11% 的活性,且轻微失活的催化剂可以通过焙烧恢复其初始活性和选择性。     

CeOx-MnOx/TiO2低温SCR催化剂的制备及脱硝性能

利用超声浸渍法分别制备了MnOx/TiO2和CeOx-MnOx/TiO2低温选择性催化还原（SCR）脱硝催化剂,并对其进行了SEM、EDS、BET及XPS等表征,在此基础上,研究了催化剂的低温SCR脱硝性能,重点考察了Mn负载量及Ce/Mn摩尔比对催化剂性能的影响,结果表明：当Mn负载量为15%时,催化剂具有较高的催化活性;Ce的掺杂有利于催化剂催化活性的提升,当Ce/Mn=0.8时,其催化活性最高,在180℃时达到了97.86%。另外,Ce的掺杂有利于提升催化剂的抗硫抗水特性,但仍有待进一步提升。     

Cu-Fe-Cr原位复合材料的纤维相结构

通过感应熔炼和冷拔变形制备了Cu 16Fe 2Cr原位复合材料 ,将铜基体选择腐蚀后提取出了纤维 ,采用SEM和TEM观察分析了纤维相结构。在较低的应变量 (η =1.6 7)时 ,纤维不均匀 ,随着变形量的增大 (η =5 .42 ) ,纤维外形变得均匀。在 η =5 .42时 ,一个显著的特点是单根Fe Cr纤维分为一些由晶界隔开的平行亚单元 (宽度约为 10 0nm) ,通过亚单元共同的 [110 ]衍射获得了晶粒之间的相对取向 ,相邻晶粒的取向角在 3°～ 15°之间。     

STUDY ON Ni-Cr SYSTEM SOLAR SELECTIVE THIN FILMS PREPARED BY MAGNETRON REACTIVE SPUTTERING PROCESS

1. IntroductionSolar selective thiIl solid fil1us are the key part for solar heat collect'ors. But ll1ostfactories still produced solar absorptive filn1s by traditional tecIl11ology sucl1 as pai1ltillga1ld electrocl1eluical process that nlust result in po…     

α黄铜选择性溶解的研究

采用恒电流E-t曲线与旋转盘环电极方法研究了α黄铜(Cu32Zn)在酸性Na2SO4和HNO3稀溶液中的阳极溶解行为,得到的典型E-t曲线上存在几个特征区,证明在较低电流密度条件下的初始阶段只存在Zn的选择性溶解。用恒电位法研究了Cu32Zn选择性溶解过程,得到了按抛物线衰减的暂态扩散曲线,由i-t-1/2直线关系求得了不同介质中Cu32Zn中Zn的固相扩散系数D在10-16～10-13cm2·s-1数量级,发现中性介质中测出的D值比酸性介质中要大两个数量级。     

稀燃车用催化剂的研究进展

稀燃车用催化剂是汽车尾气净化催化剂今后发展的方向，在稀燃条件下如何处理NOx是稀燃车用催化剂面临的巨大挑战。本文详细地评述了近年来国内外在这方面的研究工作，包括选择催化还原催化剂、存储还原催化剂和组合多功能催化剂的研究进展。     

34CrNiMo钢齿轮轴开裂原因分析

对34CrNiMo钢齿轮轴的化学成分、金相组织及断口分析表明，其淬火开裂的主要原因是由于锻造温度过高，导致过热缺陷所致。     

溶解和离子交换反应中K+的快速测定

离子溶液中快速传递及反应动力学过程的跟踪研究在实验上较为困难 ,为此基于离子选择性电极建立溶液中离子活度即时采集系统 ,并结合活度系数模型准确计算离子浓度 .该方法测定速度快 ,最小间隔为 1s,且所得离子浓度最大偏差小于 2 % .用此方法测定了硫酸钾溶解过程以及钛酸钾离子交换反应过程中钾离子浓度的变化 ,获得传统方法难以测定的数分钟内相关动态过程受溶剂、pH值的影响结果 .该方法可推广应用于研究其他各种动态过程 (如溶解、结晶、沉淀、离子交换、吸附和扩散等过程 )     

Preparation of solar selective absorbing CuO coating for medium temperature application

A new method of preparing CuO solar selective absorbing coating for medium temperature is presented. After pretreatment, brass was overlaid with CuO by chemical plating. The effects of reactant concentration, reaction temperature and reaction time on the absorptivity of CuO coating were investigated. The optimized condition of preparing CuO coating was obtained. The CuO coating was analyzed with X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). In order to prolong the period of use, the CuO coating was protected by TiO₂. The experiment shows that the TiO₂/CuO coating is more heat-resistant, acid-resistant, and wear resistant than CuO coating, without losing absorptivity markedly. The TiO₂ coating can reduce emissivity and protect the CuO coating. Translated from Journal of Tianjin University, 2006, 39(12): 1485–1489 [译自: 天津大学学报]     

Selective solvation of polystyrene in tetralin/cyclohexane mixtures

Refractive index increments and density increments have been measured at 307.6K for polystyrene in binary solvents of 1,2,3,4-tetrahydronaphthalene (tetralin, TET) and cyclohexane over the whole range of solvent composition. Comparison of these increments with the corresponding values obtained at dialysis equilibrium (i.e. at constant chemical potential of low molecular weight species) yielded the coefficients of selective adsorption (γ₁) of TET by the polymer. Positive values of γ₁ were exhibited at solvent compositions up to 78% (v/v) of the thermodynamically better solvent, TET. Theoretical curves of γ₁ vs. composition were calculated on the basis of, firstly, relevant interaction parameters and, secondly, interaction parameters in conjunction with solubility parameters. Both procedures afforded self-consistent results, which were, however, uniformly lower than the experimental values of γ₁.