稀土镧、钇对蓝色氧化钨氢还原的影响

借助于ＳＥＭ、Ｘ射线衍射技术及ＩＰＰ粉末粒度仪等系统地研究了稀土镧、钇对蓝色氧化钨（ＢＯ）氢还原的影响。结果表明：稀土元素镧、钇在蓝色氧化钨的还原钨粉中以氧化物及钨酸盐形式存在；还原后所得的钨粉颗粒大多为规则形状的多面体；稀土镧、钇和铝相似，强烈地抑制ＢＯ氢还原钨粉颗粒的长大，而且钇的作用更为显著。     

What do we mean by “catalytic activity”?

The relative reactivities of the lower alkanes in hydrogenolysis on a Pt/Al₂O₃ catalyst depend on the H₂ pressure used, as do those of a Ru/Al₂O₃ catalyst, pretreated in various ways, for propane hydrogenolysis. Apparent activation energies also vary with H₂ pressure. No single rate measurement adequately represents catalytic activity, which is properly defined as the rateconstant for the slow step.     

Selective hydrogenolysis of glycerol to propylene glycol on Cu–ZnO catalysts

Hydrogenolysis of biomass-derived glycerol is an alternative route to sustainable production of propylene glycol. Cu–ZnO catalysts were prepared by coprecipitation with a range of Cu/Zn atomic ratio (0.6–2.0) and examined in glycerol hydrogenolysis to propylene glycol at 453–513 K and 4.2 MPa H₂. These catalysts possess acid and hydrogenation sites required for bifunctional glycerol reaction pathways, most likely involving glycerol dehydration to acetol and glycidol intermediates on acidic ZnO surfaces, and their subsequent hydrogenation on Cu surfaces. Glycerol hydrogenolysis conversions and selectivities depend on Cu and ZnO particle sizes. Smaller ZnO and Cu domains led to higher conversions and propylene glycol selectivities, respectively. A high propylene glycol selectivity (83.6%), with a 94.3% combined selectivity to propylene glycol and ethylene glycol (also a valuable product) was achieved at 22.5% glycerol conversion at 473 K on Cu–ZnO (Cu/Zn = 1.0) with relatively small Cu particles. Reaction temperature effects showed that optimal temperatures (e.g. 493 K) are required for high propylene glycol selectivities, probably as a result of optimized adsorption and transformation of the reaction intermediates on the catalyst surfaces. These preliminary results provide guidance for the synthesis of more efficient Cu–ZnO catalysts and for the optimization of reaction parameters for selective glycerol hydrogenolysis to produce propylene glycol.     

Hydrogenolysis of alkanes and olefin polymerization on the silica-supported zirconium hydrides: A comparative DFT study

The model reactions of ethylene polymerization and hydrogenolysis of linear alkanes (propane, n-butane, and n-pentane) on the silica-supported zirconium hydrides (Si–O)₃Zr^IVH, (Si–O)₂Zr^IVH₂, and (Si–O)₂Zr^IIIH were studied using the DFT approach. Catalytic processes under study were shown to occur involving different surface hydrides. The ethylene polymerization was found to proceed at comparable rates on the zirconium monohydrides, (Si–O)₃ZrH, and dihydrides, (Si–O)₂ZrH₂. Cleavage of linear alkanes on the monohydrides (Si–O)₃ZrH is thermodynamically unfavorable; however, the dihydrides (Si–O)₂ZrH₂ can act as catalysts of the process under mild conditions. Hydrides of the trivalent zirconium, (Si–O)₂Zr^IIIH, can also contribute to the hydrogenolysis reaction. A feature of all the systems studied is low regioselectivity of the corresponding processes.     

Aniline hydrogenolysis on nickel: effects of surface hydrogen and surface structure

Fluorescence yield near-edge spectroscopy (FYNES) above the carbon K edge and temperature programmed reaction spectroscopy (TPRS) have been used as the methods for characterizing the reactivity and structure of adsorbed aniline and aniline derived species on the Ni(100) and Ni(111) surfaces over an extended range of temperatures and hydrogen pressures. The Ni(100) surface shows appreciably higher hydrogenolysis activity towards adsorbed aniline than the Ni(111) surface. Hydrogenolysis of aniline on the Ni(100) surface results in benzene formation at 470 K, both in reactive hydrogen atmospheres and in vacuum. External hydrogen significantly enhances the hydrogenolysis activity for aniline on the Ni(100) surface. Based on spectroscopic evidence, we believe that the dominant aniline hydrogenolysis reaction is preceded by partial hydrogenation of the aromatic ring of aniline in the presence of 0.001 Torr of external hydrogen on the (100) surface. In contrast, very little adsorbed aniline undergoes hydrogen induced C-N bond activation on the Ni(111) surface for hydrogen pressures as high as 10^–7 Torr below 500 K. Thermal dehydrogenation of aniline dominates with increasing temperature on the Ni(111) surface, resulting in the formation of a previously observed polymeric layer which is stable up to 820 K. Aniline is adsorbed at a smaller angle relative to the Ni(111) surface than the Ni(100) surface at temperatures below the hydrogenolysis temperature. We believe that the proximity and strong -interaction between the aromatic ring of the aniline and the surface is one major factor which controls the competition between dehydrogenation and hydrogen addition. In this case the result is a substantial enhancement of aniline dehydrogenation relative to hydrogenation on the Ni(111) surface.     

HBIW中主要杂质的鉴定及形成途径

采用常压制备色谱分离了六苄基六氮杂异伍兹烷( HBIW)中提取的杂质,重结晶得到其中一种主要的杂质晶体;应用FT-IR、1H-NMR、ESI-MS、元素分析鉴定了该杂质的结构,研究了它的形成途径及对氢解反应催化剂钯的影响。结果表明HBIW中的主要杂质是草酰二苄胺(Bn-NHCO-)一2,它主要由醛胺缩合中间体C6H5 CH2NHCH(OH) CH( OH) NHCH2 C6 H5在空气中氧化而生成,氢解反应中它会危害到催化剂钯的活性。     

甘油化学催化转化研究进展

如今随着生物柴油产业的蓬勃发展,其副产物甘油的再利用也越来越受到关注。文章从甘油酯化、氧化、氢解3个方面概述了甘油催化转化为其它化学品的国内外研究进展,由于篇幅所限,涉及的催化剂体系仅限于有利于工业化的多相催化剂体系。     

Efficient manganese decorated cobalt based catalysts for hydrogenation of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF) biofuel

2,5-dimethylfuran (DMF) is a promising compound in the production of biofuel with high-quality properties. In this study, it is aimed to develop new efficient catalysts to synthesize DMF from 5-hydroxymethylfurfural (HMF). Co, Mn/Co, and Ru/Co catalysts were prepared using the NaBH₄ reduction method. The catalysts were subjected to activity tests for the hydrogenation of HMF to DMF by changing the reaction parameters, such as temperature and time. Mn/Co catalysts prepared from metal precursors at various molar ratios of Mn/Co were found to be effective in hydrogenation reactions of HMF to DMF. A 91.8% DMF yield was achieved in the presence of a Mn/Co (50/50) catalyst without noble metal at 180°C for 4 hours. The Brunauer-Emmet-Teller (BET) method, x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and induction coupled plasma mass spectroscopy (ICP-MS) techniques were used to characterize the efficient Mn/Co catalyst.     

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。