C1化学工业中的贵金属催化剂

叙述了贵金属催化剂在C     

Surface Properties and Catalytic Performance of La0.8K0.2CuxMn1–xO3 for Simultaneous Removal of NOx and Soot

The influence of copper substitution in La_0.8K_0.2Cu_xMn_1–xO₃ on its catalytic performance for simultaneous removal of NO_x and soot under oxygen rich conditions was investigated. A series of catalysts was prepared and then characterized by XRD, SEM, BET, and XPS. The temperature programmed reaction (TPR) method was used to evaluate the catalytic performance of the catalysts. XRD results show that the partial substitution of Cu for Mn promotes the formation of perfect perovskites. SEM and BET results demonstrate that appropriate copper substitution enhances the porosity and increases the specific surface area, leading to conditions which are favorable for heterogeneous catalysis. XPS results indicate that a fraction of the Mn³⁺ is converted to Mn⁴⁺ on the addition of low levels of Cu. By correlation of the physicochemical properties and the catalytic performance, a large specific surface area, high porosity, high content of Mn³⁺ and synergistic effects of Mn³⁺ and Cu²⁺ are seen to favor the simultaneous catalytic removal of NO_x and soot.     

Quantitative determination of the number of surface active sites and the turnover frequency for methanol oxidation over bulk metal vanadates

The present work investigates the number and nature of the surface active sites, selectivity and turnover frequency towards methanol selective oxidation of a series of bulk metal vanadates. The catalysts were synthesized through an organic route and characterized by laser Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and specific surface area analysis (BET). The number of surface active sites (N_s) was determined by measuring the concentration of surface methoxy species adsorbed on the catalysts exposed to an atmosphere of 2000 ppm of methanol in helium at 100 °C. The specific activity values (TOFs) were calculated by normalizing the methanol oxidation reaction rate by the number of surface active sites probed by methanol chemisorption. The comparison of the methanol oxidation products distribution from bulk metal vanadates, pure V₂O₅ and corresponding metal oxides (NiO, MnO, etc.) strongly suggests that the metal vanadate catalysts consist of only surface vanadium oxide sites. The comparison of the TOF values demonstrated that bulk metal vanadates possess similar activity to monolayer vanadium oxide supported catalysts and are more active than bulk metal molybdates for methanol selective oxidation. Moreover, bulk metal vanadates are as active and selective as the commercial MoO₃/Fe₂(MoO₄)₃ catalysts at high methanol conversion.     

Influence of preparation method on the catalytic properties of acid-activated tetramethylammonium-exchanged clays

Two montmorillonites STx-1 (Texas) and SWy-2 (Wyoming) were first activated with different amounts of 12 M HCl and then exchanged with a fixed amount of 1 M tetramethylammonium (TMA⁺) chloride solution (H/TMA samples) at room temperature. TMA⁺-exchanged samples and then acid activated (TMA/H samples) were also prepared to evaluate the resistance to displacement of TMA⁺ by protons. The surface area and the acidity were determined by BET and cyclohexylamine adsorption methods, respectively. The catalytic activity of these acid activated organoclays was directly measured using the isomerization of 1-butene at 300 °C to yield cis- and trans-2-butene. The total conversion for the isomerization of 1-butene was higher for the TMA/H-samples (70 and 47% for SWy-2 and STx-1, respectively) than for the H/TMA-samples (51 and 25% for SWy-2 and STx-1, respectively). TMA⁺ cations adsorbed on the clays were extremely resistant to exchange by protons, but protons were easily displaced by TMA⁺ cations.     

差示光度法测定钼铁中钼量的研究与应用

提出在生产实践中采用差示光度法快速测定钼铁中含钼量。方法利用稀硝酸及过氧化氢分解试样,在硫酸介质中,铜盐、亚铁等催化剂存在下,使用还原剂抗坏血酸把钼（VI）还原到钼（V）,使钼（V）与硫氰酸根离子形成稳定的橙红色络合物[MoO（SCN）5]2-,借此进行差示光度测定。     

新型Mo—Fe（自身载体型复合钼酸铁）催化剂及其生产工艺

阐述了主要应用于甲醇空气氧化法、天然气直接氧化法生产重要有机化工原料甲醛等场合的新型ＭｏＦｅ（自身载体型复合钼酸铁）催化剂的应用要点、特性及其相应的技术经济效果等。主要详述了该新型催化剂的氧化反应催化机理、生产工艺及各步操作方法，进一步的改进措施等。