1,2-二氯乙烷在CoxTi1-x氧化物上的催化降解性能

随着工业和经济的快速发展,含氯挥发性有机化合物（CVOCs）排放量日益增多,对人体健康以及环境造成严重危害。催化燃烧法是治理CVOCs最有效和经济的方法之一。本文采用溶胶-凝胶法制备出了不同Ti掺杂量的Co_xTi_1-x复合氧化物,并对其物理化学性质进行了表征。研究了Co_xTi_1-x催化剂对1,2-二氯乙烷（1,2-DCE）的催化氧化性能。结果表明,当Ti掺杂量低于0.6时,Co_xTi_1-x复合氧化物呈现非晶相结构,形成无定形结构的Co-O-Ti固溶体。Ti元素的掺杂增加了Co_xTi_1-x复合氧化物的表面酸位点及吸附态氧含量。其中,Co_0.8Ti_0.2催化剂具有较大的比表面积、良好的氧化还原性能、丰富的表面吸附态氧及中强酸位点,对1,2-DCE表现出较高的催化氧化能力;在气时空速为20000mL/(g·h)、1,2-DCE浓度为4060mg/m³的条件下,其对1,2-DCE的转化率达90%时所需温度为318℃。此外,在380℃长时间运行时,Co_0.8Ti_0.2也显示出较好的稳定性。     

[Bmim]PF6-TBP萃取剂微萃取富集水中苯酚

将常规离子液体1-丁基-3-甲基咪唑六氟磷酸盐([Bmim]PF6)与特定萃取剂磷酸三丁酯(TBP)结合,建立了超声辅助的微萃取富集目标物苯酚的方法,研究了萃取剂种类、用量、pH值、超声水浴温度及离子强度等因素对富集效果的影响,得到微萃取的最佳实验条件,对该方法的富集机理进行了探讨. 结果表明,在较少的萃取剂用量(30 mL [Bmim]PF6-30 mL TBP)、较低的水浴温度(273.15 K)及无盐效应和pH值影响的条件下,富集倍数最佳达128. 二元萃取剂对苯酚的高效富集,主要是由于TBP中P==O键与苯酚?OH中的?H缔合,形成配合物.     

半导体型Mo－Fe二元氧化物催化剂的研制

通过共沉淀法和进一步焙烧制得Ｍｏ－Ｆｅ二元氧化物。经ＸＲＤ定性分析表明，它们是由含量不同的Ｆｅ２（ＭｏＯ４）３和ＭｏＯ３所组成。利用固定床反应器研究了Ｍｏ－Ｆｅ氧化物／载体催化剂对甲醇氧化制甲醛的催化性能。对二元Ｍｏ－Ｆｅ氧化物进行了气体敏感性能测试，发现对甲醇具有较高的灵敏度，对氧气的灵敏度较低。其中，具有较高活性的催化剂对被测气体的灵敏度也较高     

Selective synthesis of alcohols from syngas and hydroformylation of ethylene over supported cluster-derived cobalt catalysts

Hydroformylation of ethylene and CO hydrogenation were studied over cobalt-based catalysts derived from reaction of Co₂(CO)₈ with ZnO, MgO and La₂O₃ supports. At 433 K a similar activity sequence was reached for both reactions: Co/ ZnO > Co/La₂O₃ > Co/MgO. This confirms the deep analogy between hydroformylation and CO hydrogenation into alcohols. In the CO hydrogenation the selectivity towards alcohol mixture (C₁-C₃) was found to be near 100% at 433 K for a conversion of 6% over the Co/ZnO catalyst; this catalyst showed oxo selectivity higher than 98% in the hydroformylation of ethylene. Magnetic experiments showed that no metallic cobalt particles were formed at 433 K. It is suggested that the active site for the step that is common to both reactions is related to the surface homonuclear Co²⁺/[Co(CO)₄]^– ion-pairing species.     

Pd/silica cluster catalysts: synthesis and reactivity with H2 and C2H4

Silica-supported Pd clusters were characterized by in situ EXAFS spectroscopy. Clusters with an average nuclearity of six atoms were derived from either an inorganic or an organometallic precursor by reduction at 100–150C. Despite the small size of the clusters, EXAFS contributions from the metal-support interface were not detected. These clusters and larger ones formed by reduction at 320C absorb hydrogen on cooling in H₂ to 30C; the resultant interstitial hydride species decompose in vacuo at 30C. Vacuum treatment at 300C removes chemisorbed H₂ yielding bare Pd clusters. In contrast to larger crystallites, the Pd clusters do not react with C₂H₄ at 150 to form interstitial carbide species.     

A Fourier-transform infrared study of CO2 and CO2/H2 interactions with caesium-doped copper catalysts

FTIR spectra are reported of CO₂ and CO₂/H₂ on a silica-supported caesium-doped copper catalyst. Adsorption of CO₂ on a “caesium”/silica surface resulted in the formation of CO₂ ⁻ and complexed CO species. Exposure of CO₂ to a caesium-doped reduced copper catalyst produced not only these species but also two forms of adsorbed carboxylate giving bands at 1550, 1510, 1365 and 1345 cm⁻¹. Reaction of carboxylate species with hydrogen at 388 K gave formate species on copper and caesium oxide in addition to methoxy groups associated with caesium oxide. Methoxy species were not detected on undoped copper catalyst suggesting that caesium may be a promoter for the methanol synthesis reaction. Methanol decomposition on a caesium-doped copper catalyst produced a small number of formate species on copper and caesium oxide. Methoxy groups on caesium oxide decomposed to CO and H₂, and subsequent reaction between CO and adsorbed oxygen resulted in carboxylate formation. Methoxy species located at interfacial sites appeared to exhibit unusual adsorption properties.     

Differences in the structure of copper active sites for decomposition and selective reduction of nitric oxide with hydrocarbons and ammonia

Cu ion co-ordination-location in zeolites of MFI, erionite, mordenite matrices has been determined and the activity of the individual Cu sites compared for NO decomposition and its selective reduction by hydrocarbons or ammonia. It appears that Cu ions in the vicinity of one framework Al (site II), able to form stable Cu⁺-dinitrosyl complexes, and abundant in MFI structure, are responsible for high activity in NO decomposition. The Cu ions neighbouring two framework Al atoms (site I), and forming mostly mononitrosyl complexes, which dominate in erionite structure, provide a high activity in selective reduction of NO.     

Role and importance of oxidized nitrogen oxide adspecies on the mechanism and dynamics of reaction over copper-based catalysts

The formation of nitrate and NO₂ adspecies over Cu/MFI and copper-on-alumina catalysts and their role in the mechanism of reaction is discussed on the basis of FT-IR results and catalytic tests in unsteady-state conditions. Three specific cases are discussed: (i) reduction of NO by propane/O₂ over Cu/MFI, (ii) conversion of NO by NH₃/O₂ over copper-on-alumina catalysts and (iii) oxygen-promoted reduction of NO in the absence of reductants over Cu/MFI. The formation of nitrate species leads to self-deactivation, but Cu²⁺-NO₂ like adspecies are suggested to be a key intermediate in the reduction of NO to N₂ in all three cases examined.     

Catalytic dehydrogenative coupling of methane on active carbon. Effect of metal supported on active carbon

Ethane, ethene, ethyne and hydrogen are obtained in good yields via dehydrogenative coupling of methane in the presence of active carbon as a catalyst. The product yield is increased by supporting metal on active carbon.     

Template‐Free Synthesis of Porous Fe3O4/SiOC(H) Nanocomposites with Enhanced Catalytic Activity

We present a template‐free synthesis of Fe₃O₄/SiOC(H) nanocomposites with in situ formed Fe₃O₄ nanoparticles with a size of about 50 nm embedded in a nanoporous SiOC(H) matrix obtained via a polymer‐derived ceramic route. Firstly, a single‐source precursor (SSP) was synthesized by the reaction of allylhydridopolycarbosilane (AHPCS) with Fe‐acetylacetonate [Fe(acac)₃] at 140°C. The SSP was heat‐treated at 170°C to generate Fe₃O₄ nanocrystals in the cross‐linked polymeric matrix. Subsequently, the SSP was pyrolyzed at 600°C–700°C in argon atmosphere to yield porous Fe₃O₄/SiOC(H) nanocomposites with the high BET surface area up to 390 m²/g, a high micropore surface area of 301 m²/g, and a high micropore volume of 0.142 cm³/g. The Fe‐free SiOC(H) ceramic matrix derived from original AHPCS is nonporous. The in situ formation of Fe₃O₄ nanoparticles embedded homogeneously within a nanoporous SiOC(H) matrix shows significantly enhanced catalytic degradation of xylene orange in aqueous solution with H₂O₂ as oxidant as compared with pure commercial Fe₃O₄ nanoparticles.