铁铝交联黏土催化剂的制备及其苯直接羟基化的催化性能

通过直接向稀释的黏土悬浮液中加入Fe-Al交联剂制备了不同物质的量比的铁铝交联黏土催化剂。研究了该催化剂在苯/H2O2直接羟基化制备苯酚反应中的催化性能。结果表明,铁铝交联黏土催化剂在苯直接羟基化反应中具有良好的催化活性,苯酚收率最高可达4.9%,选择性可高达73.5%。运用XRD、FT-IR、TG-DSC、SEM等手段对铁铝交联黏土催化剂进行了表征。     

Complete oxidation of benzene on Co---Cr and Co---Cr oxide catalysts

Supported mixture metal oxide systems, Cu---Cr and Co---Cr on γ-A1₂O₃ and γ-A1₂O₃+ SiO₂ were prepared and studied. They exhibited catalytic activity in the complete oxidation of benzene.     

杂原子介孔分子筛的制备及其对苯羟化反应的催化性能

以十六烷基三甲基溴化铵为模板剂,在碱性条件下合成了过渡金属取代的MCM-41和MCM-48,研究了所得产物对以过氧化氢氧化苯直接合成苯酚反应的催化活性。并详细考察了反应的时间、温度、溶剂等对催化反应的活性的影响。     

苯直接羟基化制苯酚的技术新进展

介绍了以N2O、O2以及H2O2为氧化荆苯直接羟基化制备苯酚的技术新进展,并提出了今后的发展前景。     

Kinetics analysis of phenol and benzene decomposition in supercritical water

Decomposition of phenol and benzene was studied in supercritical water (SCW) at 370–450 °C and 25 MPa over very short residence times (0.5–100 s). The study of simple model compounds such as phenol and benzene is an essential preliminary step to elucidate the primary mechanism of char and gas formation from lignin compounds. A quantitative detailed chemical kinetics model for the primary pathways of phenol and benzene decomposition in SCW was determined using the reaction pathways for its decomposition under supercritical conditions. The activation energy of benzene decomposition (91.16 kJ mol⁻¹) in SCW is much higher than that of phenol (54.17 kJ mol⁻¹) under similar experimental conditions. This emphasized the importance of the substituent group (hydroxyl group) in the benzene ring to enhance its decomposition rate. In addition, the reaction rate parameters, which are deduced for the overall reaction network of its decomposition under similar conditions, show good agreement with each another. Hence, the reaction rates of these reaction pathways are successfully described in this study.     

Oxidation of benzene to phenol on supported Pt-VOx and Pd-VOx catalysts

Gas-phase oxidation of benzene using a mixture of oxygen and hydrogen has been carried out on silica-supported vanadium oxide catalysts modified with platinum or palladium. Catalyst activity and phenol selectivity were studied as a function of the precious metal used, the vanadium oxide loading as well as of temperature. The binary catalysts have been characterized by TPR and TEM. Pt-VO_x/SiO₂ catalysts were more active than Pd-VO_x/SiO₂ catalysts. By using platinum catalysts benzene conversion amounted to 1.0% (S_phenol=97%) at 413 K, whereas palladium catalysts reached a conversion of only 0.2% (S_phenol=86%) for the same contact time and temperature. The most active catalyst for the oxidation of benzene to phenol was a low vanadium loaded 0.5 wt.% Pt–3 wt.% V on silica catalyst. At temperatures above 413 K phenol selectivity decreased strongly because of enhanced total oxidation. Active catalysts need both components: a dispersed transition metal oxide such as VO_x as well as small precious metal particles such as platinum. The activity of the catalysts arises from a close interaction between the redox-active compound VO_x and the electron mediator and hydrogen activator platinum as was confirmed by correlation of catalytic results and catalyst properties. Highly dispersed platinum particles are exclusively located on the vanadium oxide covered surface as demonstrated by TEM investigations. TPR studies showed and enhanced reducibility of a part of vanadium(V) oxide indication a close neighborhood of VO_x and platinum.     

过氧化氢氧化苯制苯酚的催化剂研究进展

综述了过氧化氢直接氧化苯制苯酚过程中相关催化剂的研究进展,重点介绍了含钛、钒、铁、铜的催化剂,同时给出了各种催化剂所达到的收率和选择性及其工业化前景。     

Oxidation of phenol in aqueous solution with copper catalysts

The oxidation of phenol in aqueous phase over four different catalysts based on copper has been studied in a basket stirred tank reactor. Runs have been carried out at 140°C and 16 bar of oxygen pressure, with a catalyst loading of 60 g/l and at an initial acidic pH. Phenol, total organic carbon and some intermediates have been measured with the reaction time. The improvement achieved with the catalyst is established by comparison with a blank (reaction without catalyst). The commercial catalyst Engelhard Cu-0203T (CuO, 67–77%, Cu chromite, 20–30%, graphite sint., 1–3%) was found to be the most active catalyst with an acceptable mechanical and chemical stability. Copper leaches from the catalyst are higher when the mineralization of the acid intermediates does not occur (lower values of pH are obtained).     

Characterization and activity of copper and nickel catalysts for the oxidation of phenol aqueous solutions

Catalysts based on CuO/γ-alumina, CuAl₂O₄/γ-alumina, NiO/γ-alumina, NiAl₂O₄/γ-alumina and bulk CuAl₂O₄ have been structurally characterized by BET, porosimetry, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Their catalytic behaviors have also been tested for the oxidation of 5 g/l phenol aqueous solutions using a triphasic tubular reactor working in a trickle-bed regime and air with an oxygen partial pressure of 0.9 MPa at a temperature of 413 K. The copper and nickel catalysts supported on γ-alumina have surface areas of the same order as the support γ-alumina of ca. 190 m²/g and high active phase dispersions which were also confirmed by SEM, whereas the bulk copper aluminate spinel has a surface area of ca. 30 m²/g. XRD detects the phases present and shows a continuous loss of CuO by elution and the formation of a copper oxalate phase on the surface of the copper catalysts which also elutes with time. The NiO was also eluted but less than the copper catalysts. Only the copper and nickel spinel catalysts were stable throughout the reaction. Phenol conversion vs. time shows a continuous overall decrease in activity for the CuO/γ-alumina and NiO/γ-alumina catalysts. In turn, the copper and nickel spinel catalysts reach steady activity plateaus of 40 and 10%, respectively, of phenol conversion. The bulk copper aluminate spinel shows an activity plateau of 20% of the conversion which is lower than that from the copper aluminate/γ-alumina catalyst due to its lower surface area. Nickel catalysts always have lower activities than the copper catalysts for the phenol oxidation reaction. The copper catalysts drive a mechanism of partial phenol oxidation to carboxylic acids and quinone-related products with very high specific rates, and the nickel catalysts mainly drive a mechanism of CO₂ formation with lower conversion but with a potential higher catalyst life. The triphasic tubular reactor using trickle-bed regime largely avoids the mechanism of polymer formation as a catalyst deactivation process.     

A comparative study of the sorption of benzene and phenol in silicalite, HAlZSM-5 and NaAlZSM-5 by computer simulation

The sorption of benzene and phenol in silicalite, HAlZSM-5 and NaAlZSM-5 has been studied comparatively with the Cerius² software from MSI using Monte Carlo simulations. As a test of the simulation method, the well-studied system of benzene–silicalite was simulated first. The results show that the Henry constant and the isosteric heat of adsorption of benzene in silicalite are in good agreement with experimental data from the literature obtained by different methods. The open force field “Burchart–Dreiding” is proved to be suitable for simulation of the adsorption of aromatics in ZSM-5 type zeolites. The Henry constants of the systems mentioned above between 273 and 673 K, the isotherms at temperatures of 473 and 673 K, the sorption sites as well as the interaction energies between the guest molecules and the host zeolite frameworks have been obtained. The differences in the adsorption behavior between benzene and phenol in silicalite, HAlZSM-5 and NaAlZSM-5 are attributed to the differences in Coulomb interactions.     

Selective hydroxylation of phenol employing Cu–MCM-41 catalysts

We studied the oxidation reaction of phenol in aqueous and acetonitrile media under mild conditions, employing Cu-modified MCM-41 mesoporous catalysts. The stability of the catalysts under reaction conditions was confirmed by XRD, UV–VIS and FTIR techniques. Results obtained indicate that the selective oxidation of phenol with H₂O₂ by a radical substitution mechanism produces three main reaction products: catechol, hydroqinone and benzoquinone.     

TS-1分子筛在过氧化氢氧化苯制苯酚反应中的催化性能研究

以TS-1分子筛为催化剂,在淤浆反应器中对过氧化氢氧化苯制苯酚反应的催化性能进行了研究,考察了不同溶剂、过氧化氢进料方式、原料配比和反应条件等对催化性能的影响,优化了反应工艺条件,苯的转化率约达12.5%,苯酚的选择性约达92%,为进一步开展研究奠定了基础。     

Direct synthesis of middle iso-paraffins from synthesis gas on hybrid catalysts

This paper focuses on the synthesis of iso-paraffin-rich hydrocarbons by Fischer–Tropsch synthesis (FTS) over silica gel supported Co catalyst (Co/SiO₂). The basic concept is to isomerize and/or hydrocrack the primary FTS hydrocarbon products. A physical mixture consisting of a small amount of zeolite or Pd/zeolite mixed with Co/SiO₂ enhanced the formation of C₄–C₁₀ iso-paraffins while suppressing the formation of higher molecular hydrocarbons, probably because of the selective cracking of these hydrocarbons on them. In separate experiments, a two-reactor system was used. The first reactor contained a physical mixture of Co/SiO₂ and zeolite, and the second reactor contained zeolites or Pd-supported zeolites. The two-reactor system gave sharp C-number distribution within C₃–C₆ and iso-paraffins-rich products. The hydrocracking of n-octane and n-decane (model compound simulating products of the FTS reaction) over mixed catalysts composed of various compositions of Pd/SiO₂ and ZSM-5 in the presence of gaseous hydrogen showed high and stable activity, and produced primarily iso-paraffin-rich hydrocarbons. The isomerization was favored for mixtures rich in Pd/SiO₂. The role of Pd was thought to be the inlet of hydrogen spillover to the zeolite surface.     

Iron species incorporated over different silica supports for the heterogeneous photo-Fenton oxidation of phenol

Iron-containing catalysts have been prepared following different synthesis routes and silica supports (amorphous, zeolitic and mesostructured materials). Activity and stability of these materials were assessed on the photo-Fenton degradation of phenolic aqueous solutions using near UV irradiation (higher than 313 nm) at room temperature and initial neutral pH. Their catalytic performance was monitored in terms of phenol and total organic carbon (TOC) conversions. Aromatic compounds and carboxylic acids as by-products coming from incomplete mineralization of phenol as well as the efficiency of each catalytic system in the use of the oxidant were also studied. Stability of the materials throughout the photo-Fenton reaction was evaluated in terms of metal leachibility. Activity and stability depend on the environment of iron species and features of silica support. The evolution of pH with the reaction time and their relationship with TOC degradation and leaching degree has been discussed. A nanocomposite material of crystalline iron oxides supported over mesostructured SBA-15 material is shown the most successful catalyst for degradation of phenolic aqueous solutions by photo-Fenton processes, achieving an outstanding overall catalytic performance accompanied with a noteworthy stability.     

Promotion effects of ceria in partial oxidation of methane over Ni-calcium hydroxyapatite

Effects of ceria added as a promoter to a nickel-calcium hydroxyapatite catalyst, which has recently been reported to exhibit high activity and selectivity in partial oxidation of methane, were investigated. The ceria-promoted catalyst exhibited higher activity and stability than the unpromoted one. This is considered due to the oxygen storage capacity of ceria, which promotes easier removal of the deposited carbon. The optimum content of ceria was determined to lie in the range of the Ce/Ni ratio from 0.1/2.5 to 0.2/2.5.     

Reactivity of generated oxygen species from nitrous oxide over [Fe,Al]MFI catalysts for the direct oxidation of benzene to phenol

The catalytic performance of various steam-activated [Fe,Al]MFI catalysts in the direct oxidation of benzene to phenol using N₂O as oxidant is described. All [Fe,Al]MFI catalysts contain ca. 90% of iron in the high-spin Fe²⁺ state, independent of the iron concentration (0.075–0.6 wt.% iron). In the presence of N₂O at 623 K, most Fe²⁺ ions (>90%) were oxidized to Fe³⁺ ions as deduced from Mössbauer spectroscopy. In the presence of benzene, subsequent reduction of Fe³⁺ to Fe²⁺ takes place. However, not all of the oxidized Fe²⁺ to Fe³⁺ ions were able to selectively oxidize benzene to phenol. This indicates that only a fraction of iron is catalytically active. For [Fe,Al]MFI catalysts with relatively high iron concentration, most of the extra-framework iron species formed are inactive in the direct oxidation of benzene to phenol. Finally, a more detailed in situ Mössbauer study for one sample, i.e. [Fe,Al]MFI (1:8) catalyst, was performed to illustrate the reduction/oxidation properties of the different iron species formed after steam-treatment.     

Fischer-Tropsch synthesis over iron catalysts

Because of the decreased profitability of making synthetic fuels, Sasol intends expanding its production of the higher valued chemicals, in particular waxes and olefins. The advantages and disadvantages of using Fe, Co and Ru catalysts are discussed from the point of view of costs, availability, product selectivity, activity and sensitivity to poisons.The loss of activity and selectivity of iron based catalysts in both fixed and fluidized bed reactors is discussed. The main contributing factors are sulfur poisoning, oxidation and coke fouling. In fixed bed reactors sulfur poisoning and coke laydown deactivates the front end of the bed while hydrothermal sintering/oxidation deactivates the back end. In fluidized beds the deposition of large amounts of Boudouard carbon doesnot markedly lower the activity. The smaller catalyst particles end up consisting of small iron carbide entities embedded in a matrix of carbon. The larger catalyst particles consist of cores of inert magnetite surrounded by the carbide/carbon matrix.FT reactor development at Sasol is briefly reviewed.     

一种苯氧化直接制备苯酚的方法

苯酚是一种广泛使用的基础工业原料,对其合成方法的研究具有重要意义。使用非均相催化剂（SAC-16）对苯直接氧化制备苯酚的工艺过程进行了研究,并得到最佳工艺条件：反应温度为400℃,H2/CH3OH=4,HLSV=1,系统压力为3.0 MPa。     

Methanol synthesis over Cu/SiO2 catalysts

The rates of CO and CO/CO₂ hydrogenation at 4.2 MPa and 523 K are reported for a series of Cu/SiO₂ catalysts containing 2 to 88 wt.% Cu. These catalysts were prepared on a variety of silica sources using several different Cu deposition techniques. In CO/CO₂ hydrogenation, the rate of methanol formation is proportional to the exposed Cu surface area of the reduced catalyst precursor, as determined by N₂O frontal chromatography. The observed rate, 4.2×10^–3 mole CH₃OH/Cu site-sec, is within a factor of three of the rates reported by others over Cu/ZnO and Cu/ZnO/Al₂O₃ catalysts under comparable conditions. These results suggest that the ZnO component is only a moderate promoter in methanol synthesis. Hydrogenation of CO over these catalysts also gives methanol with high selectivity, but the synthesis rate is not proportional to the Cu surface area. This implies that another type of site, either alone or in cooperation with Cu, is involved in the synthesis of methanol from CO.     

Catalytic combustion of benzene over supported metal oxides catalysts

Catalytic combustion of benzene over supported metal oxides has been investigated. The catalysts have been prepared by incipient wetness method and characterized by XRD, FT-Raman, ESR and TPR. Among supported metal oxides, CuO_x, supported on TiO₂ is found to have the highest activity for benzene oxidation. In addition, among the catalysts of copper oxide supported on TiO₂, A1₂O₃ and SiO₂, titania-supported catalyst (CuO_x/TiO₂) gives the highest catalytic activity. CuO_x/TiO₂ (Cu loading 5.5 wt%) shows the total oxidation of benzene at about 250 °C. From the ESR and FT-Raman results, the CuO dispersed on the TiO₂ surface acts as an active site of CuO_x/TiO₂ catalysts on the oxidative decomposition of benzene. The catalytic activity gradually increases with an increase of Cu loading on TiO₂. When Cu loading reaches 5.5 wt%, the total conversion temperature is lowered to 300 °C. However, the catalytic activity considerably decreases at 7 wt% Cu loading. The catalytic activity increased with an increase of oxygen concentration but the concentration of benzene showed no difference in the benzene conversion. This result suggests that the rate determining step is the adsorption of oxygen.