Characteristics of Ti-MCM-41 and its Catalytic Properties in Oxidation of Benzene

A series of mesoporous titanosilicate Ti-MCM-41 molecular sieves with various Si/Ti ratios have been hydrothermally synthesized using hexadecyl-trimethylammonium bromide as the organic surfactant. These materials were characterized with powder X-ray diffraction (XRD), framework FTIR, diffuse reflectance UV-visible spectroscopy, nitrogen sorption measurements, differential thermal analysis (DTA), and transmission electron microscopy (TEM). The crystallinity of Ti-MCM-41 after calcination was almost two-fold higher than that of the as-synthesized one. The crystallinity and surface area of Ti-MCM-41 both decrease with an increase of titanium content. The results of XRD and FTIR show that the solid products have the MCM-41 structure and contained only atomically dispersed titanium, consistent with framework titanium in Ti-MCM-41. All of the materials had a uniform pore size distribution with pore size of around 3.0 nm. The hexagonal array structure of uniform pore size was observed by TEM. It proved that the pores were highly aligned. The catalytic activities of Ti-MCM-41 were tested in the partial oxidation of benzene by diluted hydrogen peroxide in a batch reactor. Ti-MCM-41 had a higher activity than TiO₂ and Ti/NaY. The activity of Ti-MCM-41 increased with titanium content. The activity of Ti-MCM-41 prepared with hydrothermal synthesis was higher than that of the sample prepared with impregnation. The high activity in Ti-MCM-41 can be attributed to its hydrohobicity and large pore size. Phenol was the only liquid phase product on all of the samples.     

富氢中CO选择氧化CuO-CeO_2催化剂性能的研究

用质量分数为20%的草酸溶液沸煮处理80～100目的堇青石载体,考察了酸处理时间对载体失重率、机械强度和比表面积的影响。采用等体积浸渍法在处理后的载体上负载CuO-CeO2活性组分制得催化剂,利用色谱流动反应法进行了活性测试,测试结果表明,用草酸处理2h的堇青石载体上负载质量分数为15%CuO-CeO2制得的催化剂对CO氧化保持较高的活性和选择性。     

烃类选择性氧化研究新进展

本文按（1）O₂分子的活比,（2）烃分子的活化,（3）氧的插入反应,（4）燃烧反应,（5）选择性氧化剂的结构特征，（6）选择性氧化催化剂中不同物相的功能与控制和（7）选择性催化氧化中的新工艺等七个方面综述了八十年代以来选择性催化氧化的进展,概述了该领域当前在理论研究和工艺开友等方面所取得的主要成就。     

Advances in Oxidation Catalysis; Oxidation of Benzene to Phenol by Nutrous Oxide

Recent decades show impressive progress in oxidation catalysis, resulting in many novel industrial technologies. However, there is a difficult and challenging field, that of oxidation reactions which cannot be selectively implemented via traditional approaches. In the present paper, we discuss recent progress achieved in this particular field through the discovery of unique oxidation chemistry involving nitrous oxide.     

2,3,9,10,16,17,23,24-八全氟己基钴酞菁的制备及其催化氧化乙苯

以4,5-二碘邻苯二甲腈和全氟碘己烷为原料,合成了前驱体4,5-二全氟己基邻苯二甲腈,再合成2,3,9,10,16,17,23,24-八全氟己基钴酞菁[Co Pc(C6F13)8]。前驱体结构经1HNMR、19FNMR、IR及MS表征确认,目标产物经HRMS、IR及紫外-可见吸收光谱分析确认。将其应用于氟两相体系催化乙苯氧化反应,考察其催化氧化性能,结果显示:以全氟辛烷为溶剂,催化剂用量为0.03 mmol,反应温度120℃,分子氧为氧源,反应6 h,在该条件下乙苯的转化率为41.8%,苯乙酮的选择性为85.3%。氟碳相可以回收使用5次,催化活性基本保持不变。     

ZrO_2负载Cu催化剂对CO低温催化氧化研究

用溶胶-凝胶-超临界干燥法制备了纳米氧化锆。采用沉淀法制备氧化锆负载铜催化剂。制备的催化剂用X-ray射线衍射(XRD),透射电镜(TEM),比表面积(BET)和H2-TPR等进行了表征。研究了催化剂的焙烧温度和负载比例对CO转化效率的影响,其最佳焙烧温度为650℃,Zr与Cu的最佳物质的量比是10:8。获得催化剂在温度为68℃具有催化活性,176℃时CO的转化率达到50%,较好地实现了ZrO2负载Cu在较低温度下对CO的催化。     

Direct preparation of silver nanoparticles and thin films in CO2-expanded hexane

Small, uniform and suspended silver nanoparticles were directly prepared in CO₂-expanded hexane by reducing a synthesized metal precursor, silver isostearate, with hydrogen but without introducing additional capping agents. By increasing CO₂ pressure, the suspended silver nanoparticles could be further deposited on a solid substrate to form silver thin film via gas antisolvent and the subsequent supercritical drying processes. The silver thin films prepared by the aforementioned method possessed a uniform thickness of about 150 nm without surface cracking and low electrical resistivity (5.64 × 10⁻⁶ Ω cm) after applying an annealing process. Due to the deposition of nano-sized silver particles, the annealing temperature could be as low as 175 °C that is lower than the softening points of many transparent polymeric substrates used for fabrication of flexible conductive films.     

ZrO2负载铜镍双金属对CO低温催化活化研究

用两种方法合成载体ZrO2,分别负载镍单金属和铜镍双金属制备催化剂,对其做CO催化,确定载体最佳制备方法。用最佳方法制备的载体负载铜镍金属做催化剂,考察催化剂焙烧温度和负载比例不同对CO催化影响。实验结果表明,用溶胶凝胶超临界干燥法制备的ZrO2为载体负载铜镍制备的催化剂其最佳焙烧温度为250℃,Zr与Cu和Ni的最佳物质的量比是10：8：4时,获得催化剂起始催化活性温度为22℃,169℃时C0的转化率达到50％,较好地实现了ZrO2负载铜镍在较低温度下对CO的催化。     

二氧化铈载金催化剂催化CO氧化的研究进展

将金纳米颗粒负载在二氧化铈上,形成负载型催化剂,能应用于多种反应体系,表现出良好的催化活性,有着广阔的发展前景。综述了二氧化铈载金催化剂在一氧化碳催化氧化中的应用研究进展,介绍了二氧化铈载金催化剂中金的结构、价态和纳米尺寸,载体二氧化铈的形貌、结构、尺寸和氧空位以及金和载体二氧化铈两者之间的相互作用对一氧化碳催化氧化性能的影响。     

Surface-modified Improvement in Catalytic Performance of Cr(salen) Complexes Immobilized on MCM-41 in Solvent-Free Selective Oxidation of Benzyl Alcohol

A series of typical methyl regulators were used to finely modify the Cr(salen) complex immobilized on MCM-41. Such immobilized complexes were effective catalysts for solvent-free selective oxidation of benzyl alcohol (BzOH) with 30% hydrogen peroxide (H₂O₂), and they all exhibited much higher catalytic performance than their homogeneous analogue. Simultaneously, the introduction of methyl regulators was found to significantly improve the catalytic performance of immobilized complexes by modifying their surface properties. The optimal BzOH conversion reached 65.0% with 100% selectivity to benzaldehyde (BzH).     

用于控制CO2氨法捕获过程中NH3逸出的选择性催化氧化（SCO）催化剂

利用NH3选择性催化氧化(NH3-SCO)方法控制电站CO2氨法捕获过程中的NH3逸出具有良好的应用前景,但用于该方法的催化剂应该具有高低温活性、高N2选择性高、长耐久性和低成本等特性。为推进NH3-SCO技术的实用化进程,本文在文献研究的基础上,总结了几种NH3-SCO催化剂的组成、不同催化剂和不同运行条件下NH3-SCO的特性和机理以及能提升催化效果的助剂,以期为探索合适的新型催化剂和新型反应器结构提供参考。文献研究表明,Ag/Al2O3是一种具有良好低温活性的NH3-SCO催化剂,但需具备Fe-ZSM-5所具有的高N2选择性,同时,还可以考虑利用一些物质如Ce可以用来进一步提升Ag/Al2O3的低温活性。     

The Mechanism for the Selective Oxidation of CO Enhanced by H2O on a Novel PROC Catalyst

Preferential oxidation (PROX) reaction of CO in H₂ catalyzed by a new catalyst of FeO _x /Pt/TiO₂ (Fe: Pt: TiO₂ = 100: 1: 100) was studied by dynamic in-situ DRIFT-IR spectroscopy. The oxidation of CO is markedly enhanced by H₂ and H₂O, and the enhancement by H₂/D₂ and H₂O/D₂O takes a common hydrogen isotope. Dynamics of DRIFT-IR spectroscopy suggests that the oxidation of CO with O₂ in the absence of H₂ proceeds via bicarbonate intermediate. In contrast, rapid oxidation of CO in the presence of H₂ proceeds via HCOO intermediate and the subsequent oxidation of HCOO by the reaction with OH, that is, CO + OH→ HCOO and HCOO + OH → CO₂ + H₂O. The latter reaction is a rate determining step being responsible for a common hydrogen isotope effect by H₂/D₂ and H₂O/D₂O.     

含铜三元类水滑石的合成及其催化苯甲醛H2O2氧化的应用研究

采用共沉淀法中的变化pH值法和过饱和恒定pH值法制备了含铜三元类水滑石化合物CuMAl-HTLcs、通过XRD和IR表征其结构.并将此类水滑石应用于苯甲醛H2O2的氧化中,结果表明CuZnAl-HTLcs、CuNiAl-HTLcs两种类水滑石对苯甲醛H2O2氧化的催化活性远高于其它金属离子搭配的CuMAl-HTLcs,经老化的与未经老化的CuMAl-HTLcs对苯甲醛H2O2氧化的的催化活性相比,前者弱于后者.     

Selective oxidation of CO in the presence of H2, CO2 and H2O, on different zeolite-supported Pt catalysts

The selective oxidation of CO in the presence of H₂O and CO₂ has been studied on Pt supported on different zeolitic materials (MOR, ZSM-5, FAU and ETS-10) using a range of operating conditions and a variety of characterization techniques. The behavior of the Pt–ETS-10 and Pt–FAU catalysts has been investigated in more depth and the results obtained have been compared and related to the different characteristics of the supports. The best results in the presence of H₂O and CO₂ were obtained with Pt–FAU catalysts, showing stable catalytic activity and complete conversion of CO (λ = 2) at 439 K.     

Catalytic Performance of the Sb–V Mixed Oxide on Sb–V–O/SiO2 Catalysts in Methane Selective Oxidation to Formaldehyde

Sb–V–O/SiO₂ catalysts were prepared and investigated in methane selective oxidation with O₂ as oxidant. Sb–V–O/SiO₂ catalysts are active and selective in methane selective oxidation. The formaldehyde yield obtained on Sb–V–O/SiO₂ catalysts is clearly higher than that for VO_X/SiO₂ and SbO_X/SiO₂ catalysts. A one-pass formaldehyde yield up to 3% was obtained on Sb–V–O/SiO₂ catalysts at 650 °C. XRD and UV Raman studies showed that the phase of Sb–V mixed oxide on Sb–V–O/SiO₂ catalysts transformed with decreasing Sb/V ratio from Sb₂VO₅ to SbVO₄/VSb_1-XO_4-1.5X phase. The Sb–V mixed oxide in Sb₂VO₅ phase is more active and selective than that in SbVO₄/VSb_1-XO_4-1.5X phase.     

Noble Metal (Pt, Rh, Pd) Promoted Fe-ZSM-5 for Selective Catalytic Oxidation of Ammonia to N2 at Low Temperatures

We have reported previously the excellent performance of Fe-exchanged ZSM-5 for selective catalytic oxidation (SCO) of ammonia to nitrogen at high temperatures (e.g., 400-500 °C). The present work indicates that the reaction temperature can be decreased to 250-350 °C when a small amount of noble metal (Pt, Rh or Pd) is added (by both doping and ion exchange) to the Fe-ZSM-5. The SCO activity follows the order: Pt/Fe-ZSM-5 > Rh/Fe-ZSM-5 > Pd/Fe-ZSM-5. The noble metal promoted Fe-ZSM-5 catalysts also show higher activity for NH₃ oxidation than Ce-exchanged Fe-ZSM-5 at low temperatures. On the Pt promoted Fe-ZSM-5, near 100% of NH₃ conversion is obtained at 250 °C at a high space velocity (GHSV = 2.3 × 10⁵ h^-1) and nitrogen is the main product. The presence of H₂O and SO₂ decreases the SCO performance only slightly. This catalyst is a good candidate for solving the ammonia slip problem that plagues the selective catalytic reduction (SCR) of NO with ammonia in power plants.     

Activation of VOHPO4 · 0.5H2O in Propane/Air Mixture: Effect on Structural, Morphological, Oxidant’s Behaviour and Catalytic Property of (VO)2P2O7 Catalysts for Propane Oxidation

VOHPO₄ · 0.5H₂O synthesized by VOPO₄ · 2H₂O and isobutanol was activated in a flow of propane/air mixture (1% propane in air) at 673 K for 36, 75 and 132 h. Three vanadyl pyrophosphate catalysts obtained were denoted as VPD36P, VPD75P and VPD132P. The crystallinity of all propane/air pretreated catalysts as shown in XRD increased with the duration of calcination. SEM micrographs showed the formation of more isolated platelets and more prominent rosebud-shape agglomerate as the pre-treatment was longer. Four reduction peaks maxima at 752, 920, 1026 and 1140 were observed in the rate of hydrogen consumption for VPD36P. As the calcination duration increased to 75 h, the H₂ reduction peaks were shifted to lower temperatures at 750, 882, 1004 and 1140 K. When the calcination duration was further increased to 132 h, only three reduction peaks were observed at 752, 952 and 1142 K. Despite the progressively shifted of the major reduction peak maximum as the duration of calcination increased from 36 to 132 h, the lattice oxygen from VPD36P was found to be the most reactive. The catalytic performance for propane oxidation to acrylic acid (AA) showed that VPD36P gave the highest activity (9.6%) with 83.0% of selectivity to AA.     

催化裂化再生器中铂助燃剂催化活性的测定(Ⅰ)——在新助燃剂上CO氧化的反应动力学

研究了催化裂化再生条件下铂助燃剂上ＣＯ氧化反应动力学。在排除了反应管及稀释剂的催化氧化作用后，测定了铂含量为１０－６ｇ／ｇ的国产新助燃剂上的反应动力学数据，得出了在氧过量时一氧化碳和氧的反应级数分别为１和０．５。给出了６６０℃下的反应速度常数值及其置信区间。     

Amplification of Periodic Temperature Disturbances in a Packed‐Bed Reactor: CO Oxidation over a CuO/Al2O3 Catalyst

Amplification of periodic variations of input temperature in a product‐inhibited reaction — CO oxidation over CuO‐γ‐Al₂O₃ — was investigated experimentally in an insulated packed‐bed reactor. At steady state the temperature profile was elongated compared with that of a reactant‐inhibited CO oxidation over Pt/Al₂O₃, studied elsewhere. Under periodic operation, amplitudes of the resulting travelling temperature waves, monitored downstream from the reaction front, were amplified to a greater extent than those in the reactant‐inhibited CO oxidation over Pt/Al₂O₃. The magnitude of the amplification depended on the perturbation frequency and showed resonance behaviour. The magnitude decreased monotonically with increasing perturbation amplitude.     

Activity, Selectivity, and Long-Term Stability of Different Metal Oxide Supported Gold Catalysts for the Preferential CO Oxidation in H2-Rich Gas

A comparative study of the catalytic performance and long-term stability of various metal oxide supported gold catalysts during preferential CO oxidation at 80°C in a H₂-containing atmosphere (PROX) reveals significant support effects. Compared to Au/-Al₂O₃, where the support is believed to behave neutrally in the reaction process, catalysts supported on reducible transition metal oxides, such as Fe₂O₃, CeO₂, or TiO₂, exhibit a CO oxidation activity of up to one magnitude higher at comparable gold particle sizes. The selectivity is also found to strongly depend on the employed metal oxide, amounting, e.g., up to 75% for Au/Co₃O₄ and down to 35% over Au/SnO₂. The deactivation, which is observed for all samples with increasing time on stream, except for Au/-Al₂O₃, is related to the build-up of surface carbonate species. The long-term stability of the investigated catalysts in simulated methanol reformate depends crucially on the ability to form such by-products, with magnesia and Co₃O₄ supported catalysts being most negatively affected. Overall, Au/CeO₂ and, in particular, Au/-Fe₂O₃ represent the best compromise under the applied reaction conditions, especially due to the superior activity and the easily reversible deactivation of the latter catalyst.