Catalytic wet peroxide oxidation of phenol over AlFe-pillared montmorillonite

Catalytic wet peroxide oxidation of phenol over AlFe-pillared montmorillonite was carried out at room temperature, in a glass batch reactor, under constant airflow at day and UV light, alternatively. At higher concentration of phenol in water solution the efficiency of heterogeneous pillared clay catalyst was significantly lower than the efficiency of homogeneous iron catalyst. This revised version was published online in June 2006 with corrections to the Cover Date.     

Catalytic characterization of pillared clays through toluene methylation reaction

Pillared clays (PILCs) with Al and Zr oxide pillars were studied in terms of their structure and texture. The catalytic properties of the samples were evaluated through toluene methylation reaction. As comparison material, a commercial zeolite HZSM-5 was used. The toluene conversion at short time-on-stream over PILCs, although smaller than the value obtained with HZSM-5, attains values of 37 (molar %). In all cases the reaction products are a mixture of xylene, ethyltoluene and trimethylbenzene isomers. All samples present higher selectivity to xylene isomers, which are the primary products. For Zr pillared clay, the percentage of these isomers is the highest.     

Facile one-pot synthesis of mesoporous heteropolyacids-silica hybrid for catalytic wet hydrogen peroxide oxidation of phenol

The fabrication of molybdovanadophosphoric acids incorporated into SBA-15 mesoporous silicas has been achieved via a one-pot procedure. The as-obtained composite materials were well characterized by XRD, TEM, and nitrogen adsorption–desorption which indicated that the composite materials possessed good mesoporous character. FT-IR, ICP showed molybdovanadophosphoric acids had been successfully incorporated into SBA-15 mesoporous silicas with intact structure of Keggin units. Due to well dispersion of the Keggin units, high structural stability, and low leaching level of active Keggin units, the obtained-catalysts systems showed significant catalytic efficiency and reusability for wet hydrogen peroxide oxidation of phenol.     

一价铜改性ZSM-5催化剂及其催化碳烟氧化反应性能研究

采用固态离子交换法制备了系列一价铜改性的ZSM-5催化剂,结合多种表征手段,研究了一价铜改性对碳烟氧化反应催化活性的影响。结果表明,采用固态离子交换法可以制备出高负载量的一价铜改性Cu/ZSM-5分子筛催化剂,而不会破坏ZSM-5分子筛原有微孔结构;随催化剂中一价铜比例的增加,低温还原峰和高温还原峰均向低温段移动,且低温还原峰面积增加。改性催化剂对碳烟氧化反应的催化活性随改性元素比例变化先增加后降低;当铜改性比例超过11%后,铜物种的分散性及催化剂对碳烟氧化反应的催化活性均恶化。同时研究还发现,反应气氛中通入NO可以改善催化剂对碳烟氧化反应的催化效果。     

Kinetics of wet air oxidation of sodium sulfide over heterogeneous iron catalyst

Wet air oxidation (WAO) is an established technique for reducing the chemical oxygen demand (COD) of refinery sulfidic spent caustic waste. In the present work, the heterogeneous form of the cheap and abundant catalyst ferrous sulfate (FeSO₄) was employed for WAO of sodium sulfide. The performance of this catalyst in the oxidative destruction of this model compound is thus far unfamiliar. Kinetic data for the non-catalytic and catalytic oxidation processes was collected in a batch reactor. For the catalytic process, temperature (T), oxygen partial pressure () and catalyst concentration (ω) were varied in the ranges 80-150°C, 0.69-2.06 MPa and 0.8-2.4 g/L respectively. Around 94% COD was destroyed within 1 h when feed containing 8 g/L of sulfide was oxidized at T = 100°C, = 0.69 MPa, and ω = 0.8 g/L. First, the data on disappearance of COD were fitted to a power law model and reaction rate constants were determined. The activation energy for the non-catalytic (91 kJ/mol) and catalytic (50 kJ/mol) oxidation process was found from the temperature dependence of the rate constants. Second, hyperbolic models based on Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-L) kinetics were used for fitting kinetic data. It was found that the L-H model suggesting dissociative adsorption of oxygen provided the best fit. In this way, a deep insight into oxidation kinetics of sodium sulfide was provided.     

Fe/Al-PILC催化C_3H_6选择性还原NO的实验研究

采用浸渍法制备了负载于铝柱撑黏土的铁基催化剂(Fe/Al-PILC),在固定床反应器上测试其催化C3H6选择性还原NO的性能。通过N2吸附-脱附、X射线衍射(XRD)、H2的程序升温还原(H2-TPR)、紫外可见光谱(Uv-vis)、吡啶吸附红外光谱(Py-FTIR)等手段对催化剂的物理化学性质进行表征。结果表明,9Fe/Al-PILC在400-550℃能够还原98%以上的NO,而且SO2和水蒸气对其催化性能的影响很小。XRD、N2吸附-脱附表征结果表明,Fe/Al-PILC催化剂中铁氧化物高度分散在载体表面,催化剂有较大的比表面积和孔容。H2-TPR结果表明,催化剂的活性主要由Fe_2O_3物相的还原性能决定。Uv-vis结果表明,催化剂的活性与铁氧低聚物种FexOy呈正相关性。Py-FTIR结果表明,催化剂表面同时存在Lewis酸和Brnsted酸,L酸性位是NO和C3H6反应的主要催化活性中心。     

Catalytic activity and acidity of Al pillared clays and zeolites in different hydrocarbon reactions

In comparison with zeolites, a variety of Al pillared clays did not prove as promising cracking catalysts, possibly because their Br?nsted sites are hidden. In the less demanding double bond shift isomerization, both catalyst types were comparable probably due to the presence of Lewis sites on both catalysts.     

Catalytic oxidation of alcohols to carbonyl compounds with hydrogen peroxide using dinuclear iron complexes

Oxidation of primary and secondary alcohols has been studied in the presence of [Fe(ind)Cl]₂O (1) and [Fe₂(OMe)₂(PAP)Cl₄] (2) (indH = 1,3-bis(2′-pyridylimino)isoindoline; PAP = 1,4-di(2′-pyridyl)aminophthalazine) as catalysts using hydrogen peroxide as primary oxidant. The complexes were found to be suitable catalysts for the oxidation of alcohols to the corresponding carbonyl compounds in acetone as solvent. The reactivity of the alcohols is in the order primary < secondary < cyclic secondary < aromatic. The reaction mechanism in the case of 1 probable involves an iron-based oxidant, while in the case of 2 a free-radical mechanism is suggested.     

Photo-oxidation of phenol over titania pillared zirconium phosphate and titanium phosphate

The photodegradation of phenol was studied in the aqueous solutions over titania pillared zirconium phosphate and titanium phosphate under solar radiation and compared with that of the UV-radiation (6 W low pressure Hg vapor lamp). This reaction was studied by varying different parameters such as catalyst dose, initial phenol concentration, pH of solution and irradiation time. The degradation rate of phenol was favourable under neutral pH condition. The degradation process approximately obeyed first-order kinetics with apparent rate of degradation constant increasing with decreasing the initial phenol concentration.     

改性二氧化钛负载贵金属Ru催化剂催化降解苯胺溶液

苯胺类废水污染物具有结构复杂、浓度高、不易生物降解、生物毒性大等特点,传统的苯胺降解措施存在着许多弊端,很难达到排放标准.催化湿法氧化技术(CWAO)主要针对降解高浓度难降解的有机废水,表现出降解效率高、反应时间短、对生物毒性物质的废水降解效果良好等优点,越来越受到人们的重视.但催化剂在使用过程中,需要在高温高压下进行,且有机物降解产生了有机酸,使得催化剂的活性组分流失和载体的物理化学性质发生变化,导致其催化活性下降.因此,需要开发出一种降解活性高,性能稳定的催化剂成为此技术在工业中广泛应用的关键.本文采用溶胶凝胶法对二氧化钛进行改性,制备了Ti0.9Zr0.1O2和Ti0.9Ce0.1O2载体,采用过量浸渍法将三氯化钌负载到载体表面制备了2%Ru/Ti0.9Zr0.1O2和2%Ru/Ti0.9Ce0.1O2催化剂.在高温高压反应条件下,以苯胺为催化湿法氧化污染物,对不同催化剂湿法降解苯胺进行比较研究,系统地探究了催化降解的反应温度和反应压力对苯胺降解的影响.此外,利用HPLC-MS鉴定出催化降解产生的中间产物,确定了催化降解的反应路径图.在改性的催化剂中,2%Ru/Ti0.9Zr0.1O2催化剂表现出最高的催化降解活性和稳定性.在初始苯胺浓度4 g/L,催化剂浓度4 g/L,反应温度180℃,O2压力1.5 MPa下,反应时间5 h后,苯胺完全转化,COD转化率达88.3%.并且催化剂进行三次循环试验后,苯胺转化率仍接近100%.X射线衍射和N2物理吸附结果表明,Ce,Zr掺杂到TiO2晶格中形成了共溶体,其晶格尺寸更小,比表面积和孔体积更大.负载贵金属后,并未出现其他晶相,说明贵金属均匀分散在载体表面.透射电镜结果表明,贵金属负载在改性TiO2上表现出较好的分散性和较小的颗粒尺寸,为催化降解苯胺提供更多的催化活性位点,而Ru/TiO2催化剂表面,贵金属发生团聚现象且颗粒尺寸大.X射线光电子能谱结果表明,Ce,Zr的掺杂使得TiO2表面活性氧和四价Ru的含量增加,更多的表面活性氧成为催化降解苯胺的直接原因.H2程序升温还原结果表明,在300?400oC处还原峰对应于催化剂载体晶格氧的还原,改性后,其还原峰增至2倍,即使在贫氧环境下,改性催化剂可以及时从载体中释放晶格氧,为催化降解苯胺提供更多的活性氧.     

Catalytic oxidation of monosubstituted phenols by hydrogen peroxide

Studies of kinetic peculiarities in hydroxylation of phenols by H₂O₂ in the presence of ferric sulfate have revealed general regularities of this process. A scheme of this process is suggested accounting for the stepwise conversion of Fe³⁺ into various complex forms. The reaction is suggested to take place in the coordination sphere of Fe³⁺.

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H₂O₂ . . , Fe³⁺ .

     

Catalytic properties of Fe-HMS materials in the phenol oxidation

Iron-incorporated mesoporous silica material Fe-HMS-50 (the Si/Fe molar ratio in the precursor gel is 50) was synthesized at ambient temperature by using hexadecylamine as a template and characterized by chemical analysis and N₂ adsorption measurements. The catalytic performance of Fe-HMS was studied in the phenol hydroxylation and wet phenol oxidation with H₂O₂ at 313 K. The effect of pH, H₂O₂: PhOH molar ratio and stability of the catalyst on the oxidation process was investigated. In the phenol oxidation, the activity of the catalyst increases by increasing the acidity of the reaction mixture to pH 3.4 and the amount of leached iron species was 1.95 ppm. A recycling test indicates that the catalyst recovered by drying in air at 423 K suffered, after the first run, a 12.4% drop in the catalytic activity. Fe-HMS has high catalytic activity and selectivity to dihydroxybenzene in the phenol hydroxylation. Hydroquinone was found as the predominant product under these experimental conditions with small amounts of benzoquinone appearing at the end of the reaction.     

SBA-15负载的Cu(Ⅱ)席夫碱配合物催化的苯乙烯氧化反应制备苯甲醛

采用一步法将原硅酸四乙酯与3-氨丙基三乙氧基硅烷在表面活性剂P123作用下,酸性共水解制备出氨基功能化的介孔分子筛SBA-15(NH2-SBA-15),再利用其中氨基与水杨醛的缩合反应制备SBA-15固载的席夫碱,该席夫碱与Cu(NO3)2溶液反应最终制成固定于SBA-15的Cu(II)席夫碱配合物多相催化剂Cu-SBA-15.采用X射线衍射、红外光谱仪、紫外可见分光光度计、场发射电镜、透射电镜、N2吸附-脱附、元素分析、原子发射光谱和热重分析对催化剂进行了表征,并将此催化剂用于无有机溶剂条件下催化氧化苯乙烯制备苯甲醛,考察了反应时间、反应温度、H2O2用量、水的用量、催化剂用量对反应的影响.当反应温度为100°C,反应时间8 h,H2O2与苯乙烯的摩尔比为2:1,不额外添加溶剂,且催化剂用量为3.8 wt%时,苯乙烯的转化率最高为84.4%,苯甲醛选择性为83.9%,催化剂的TOF值为261.1 h–1,并且重复使用3次后活性没有明显下降.规则的孔道、较大的比表面积以及分布均匀的活性中心可能是催化剂活性提高的原因.     

Catalytic alkylation of phenol with methanol over zinc aluminate

Two samples (A and B) of zinc aluminate spinel were prepared and used as catalysts of phenol methylation. Both catalysts were synthesised at hydrothermal conditions from zinc acetate and from various aluminium precursors: aluminium isopropoxide (catalyst A) or basic aluminium nitrate (catalyst B). Catalyst A was pure ZnAl₂O₄ and B - besides ZnAl₂O4 contained traces of -Al₂O₃. Reactions of phenol alkylation with methanol were carried out in the gas phase under atmospheric pressure in a standard flow reactor with fixed bed. Catalysts indicated different properties in dependence on the aluminium precursor used during preparation. In the presence of catalyst A higher selectivity of ortho-methylation of phenol was obtained. Catalyst B was active both in O-alkylation and C-alkylation.     

Catalytic wet air oxidation of 2-nitrotoluidine and 2,4-dinitrotoluene

The rates of wet air oxidation of 2-nitrotoluidine and 2,4-dinitrotoluene in the presence of excess oxygen and at different temperatures and oxygen pressures was investigated. Oxidation experiments were carried out at temperatures between 180 and 225^oC and oxygen partial pressures of 1,0-3,0 MPa, in a 280 mL glass vessel-inserted stainless steel reactor. Copper sulfate (CuSO₄ .5H₂O) was used as a catalyst, and the effect of catalyst loading was studied by varying the concentration: 0.75, 2.5 and 25 mg/L as Cu²⁺. Addition of Cu²⁺ ions in the reaction media accelerated 2-nitrotoluidine oxidation nearly ten times even if it exists in trace amount in the reaction medium (0.75 ppm Cu²⁺). Unfortunately copper did not show catalytic effect for the oxidation of 2,4-dinitrotoluene. This revised version was published online in August 2006 with corrections to the Cover Date.     

催化湿式共氧化法同时去除硝基苯和苯酚

在150–210 oC,1.0 MPa氧分压条件下,对催化湿式共氧化法同时去除硝基苯和苯酚进行了研究.与无催化剂共氧化降解苯酚和硝基苯相比,均相催化剂的加入极大提高了苯酚和硝基苯的去除.在所研究的过渡金属催化剂中, Cu2+, Co2+和Ni2+是有效的催化剂,其中Cu2+的催化活性最好.引发剂苯酚的连续加入模式对硝基苯的去除有很大的促进作用,分批加入苯酚的促进作用更明显.在200 oC,以Cu2+为催化剂,苯酚分两次加入,反应1 h,硝基苯去除率达到95%.这种催化共氧化体系以及分批进样引发剂的反应模式对有效去除环境中其它有机污染物提供了一种方法.     

Catalytic oxidation of hydrocarbons with hydrogen peroxide by vanadium-based polyoxometalates

Vanadium compounds have attracted much attention because they have widely been used for homogeneous, heterogeneous, industrial, and biological oxidation processes with alkyl hydroperoxides, H₂O₂, and O₂. The present review summarizes recent developments for homogeneous and heterogeneous liquid-phase oxidation of hydrocarbons with H₂O₂ catalyzed by vanadium complexes and vanadium-based polyoxometalates including our recent studies on selective oxidation of hydrocarbons with H₂O₂ catalyzed by divanadium-substituted polyoxotungstates, [γ-SiW₁₀O₃₆V₂(μ-OH)₂]^4? (I) and [γ-PW₁₀O₃₆V₂(μ-OH)₂]^3? (II).     

Photo-Fenton oxidation of phenol over a Cu-doped Fe-pillared clay

A Cu-doped Fe-pillared Tunisian clay (Cu/Fe–PILC) was synthesized and used as a catalyst in the heterogeneous photo-Fenton oxidation of phenol in aqueous solution. Textural, structural and chemical characterization pointed to successful pillaring and incorporation of the Cu active phase. Photo-Fenton experiments proved the high activity of the Cu/Fe–PILC catalyst, which was able to completely mineralize the phenol present in the treated solution after a reaction time of 40 min and in the presence of UV-C light. Moreover, the catalytic activity was not influenced by the pH of the initial phenol solution, over a wide range of pH from 3 to 7. An optimal dosage of H₂O₂ and of the catalyst was found. Phenol degradation was found to be slower in the presence of UV-A irradiation, needing longer reaction times. Negligible metal leaching and catalyst reutilization without noticeable loss of activity point to an excellent catalytic stability for this Cu/Fe–PILC catalyst.     

Cu-Ce/AC吸附-催化剂对所吸附苯酚的催化氧化行为的研究

对活性炭载氧化铜和氧化铈（Cu-Ce/AC）吸附 催化剂在连续吸附-催化氧化苯酚循环过程中的催化氧化活性和失活原因进行了研究。结果表明,Cu-Ce/AC的苯酚吸附性能和催化氧化活性随着吸附 催化氧化循环次数的增加而逐渐降低,经5次循环后,苯酚的初始氧化温度提高约25℃。通过对使用过的Cu Ce/ACs进行XPS、ICP分析, 发现Ce和Cu的流失较小,苯酚残留物覆盖表面Ce和Cu是苯酚催化氧化活性降低的主要原因,残留物主要含有C-O-C和C-OH等官能团。