Mineralization of phenol by a heterogeneous ultrasound/Fe-SBA-15/H2O2 process: Multivariate study by factorial design of experiments

A novel heterogeneous catalyst has been used for the oxidation of aqueous solutions of phenol by catalytic wet peroxide oxidation assisted by ultrasound irradiation. This composite catalyst material that contains crystalline hematite particles embedded into a mesostructured SBA-15 matrix was used successfully in the oxidation of phenol by heterogeneous Fenton and photo-Fenton processes. Ultrasound is found to enhance the activity of the catalyst in the process, without prejudice to the stability of the iron supported species. The influence of different variables, such as hydrogen peroxide concentration or catalyst loadings in the reaction was studied by factorial design of experiments. Catalyst loadings of 0.6 g L⁻¹ and a concentration of hydrogen peroxide close to twice the stoichiometric amount yield a remarkable organic mineralization, accompanied by excellent catalyst stability. The coupled US/Fe-SBA-15/H₂O₂ process at room temperature is revealed as a promising technique for wastewater treatment.     

非均相Fenton催化降解酚类化合物的研究进展

非均相Fenton催化法是去除水中难降解有机污染物的一种重要高级氧化技术,近些年以其效率高、污染少、材料来源广泛而受到人们更多的重视。介绍了现今主要的非均相Fenton催化降解酚类化合物的催化剂研究进展,包括零价铁、Fe3O4、Fe2O3、以碳、黏土、柱撑黏土、沸石、介孔二氧化硅等为载体的催化剂。最后提出了三个非均相Fenton反应的研究方向。     

非均相微波协同类Fenton催化降解废水中的苯酚

通过等体积浸渍法制备了CuO/γ-Al_2O_3催化剂,并对非均相微波协同类Fenton催化降解苯酚溶液进行了实验研究。实验结果表明,在溶液初始pH为6,H_2O_2投加量为4 m L/L,催化剂投加量为4 g/L,微波功率为500 W,反应时间为13 min的条件下,苯酚降解率可达98%,TOC去除率为62%。催化剂重复使用9次后,苯酚降解率为90.88%。通过比较不同氧化体系处理效果及添加·OH捕获剂证实,微波-催化剂-H_2O_2产生了明显的协同作用。     

Copper/carbon composites from waste printed circuit boards as catalysts for Fenton-like degradation of Acid Orange 7 enhanced by ultrasound

A novel strategy of “waste treating waste” has been implemented in this work. Copper/carbon (Cu/C) composites prepared by the carbonization of waste printed circuit boards (PCBs) were used for the degradation of Acid Orange 7 (AO7). Catalytic degradation of AO7 was conducted by varying carbonization temperatures, catalyst dosage, H₂O₂ dosage, AO7 concentration, pH values, and anions. Ultrasound significantly improved AO7 degradation, obtaining 93.27% degradation within 90 min. We report that Cu/C composites show good catalytic activity in a broad pH range. Cu/C catalysts were characterized by multitechniques. Cu⁰ was the main active component for the generation of •OH that was the reactive oxidant for AO7 degradation. The plausible pathway and catalytic mechanism for AO7 degradation were proposed. The unique structure of Cu/C composites gave a combined mechanism of adsorption and catalysis. Cu/C composites showed superior durability for AO7 degradation. Using Cu/C composites as catalysts provides a green approach for wastewater treatment and waste management. © 2019 American Institute of Chemical Engineers AIChE J, 65: 1234–1244, 2019     

非均相类Fenton法降解硝基苯化工废水的效能及其机制

以实验室制备的3A-Fe型分子筛为催化剂,并利用扫描电镜、能谱分析和XRD技术对催化剂进行了表征。在3A-Fe型分子筛与H₂O₂构建的非均相类Fenton催化体系内对硝基苯的降解效能和机制进行了研究,讨论了体系pH值、H₂O₂的投加量、催化剂投加量、硝基苯废水浓度对硝基苯降解率和反应速率的影响,并初步揭示了硝基苯的降解机理。结果表明：3A-Fe分子筛作为催化剂的类Fenton反应,在pH值2～10之间都具有较好的处理效果;类Fenton体系氧化降解反应过程是一种非均相的界面微观反应;3A-Fe类Fenton催化剂性能优越,对硝基苯废水中硝基苯的去除率为94.1%,COD_Cr和TOC的去除率分别为78.6%和60.5%。     

非均相类Fenton催化剂脱汞的实验与机理

采用共沉淀法分别制备Ti、Co、Cu掺杂Fe₃O₄的非均相类Fenton催化剂,在小型实验台架上进行非均相类Fenton反应脱汞的实验研究。利用X射线衍射(XRD)、扫描电子显微镜(SEM)对催化剂的晶体结构和形貌进行了表征。实验考察了掺杂前Fe₃O₄和掺杂后Fe_2.59Ti_0.41O₄、Fe_2.52Co_0.48O₄、Fe_2.44Cu_0.56O₄催化剂的类Fenton脱汞性能,并通过电子顺磁共振技术(EPR)分析了非均相类Fenton脱汞的机理。结果表明:Ti、Cu掺杂后的催化剂具有较高的催化活性, 的强氧化作用是类Fenton脱汞的主要原因。     

乙醇羰化非均相催化剂的研究进展

介绍了乙醇羰化制丙酸及丙酸乙酯的非均相催化过程,综述了非均相催化反应过程中的活性组分、催化助剂、载体的选择及其对催化过程的影响。介绍了活性组分分类(络合物、金属氯化物、贵金属和非贵金属),同时介绍了助剂的使用情况和活性炭载体的应用。论述了以往研究的成果和不足,提出了今后的发展方向。     

Effect of magnesium ferrite doping with lanthanide ions on dark-, visible- and UV-driven methylene blue degradation on heterogeneous Fenton-like catalysts

The catalytic behavior of magnesium ferrites doped with lanthanide ions (La³⁺, Ce³⁺, Sm³⁺, Gd³⁺, and Dy³⁺) on Methylene Blue (MB) degradation using Fenton process was studied. A slow increase in cubic Fd3m crystalline structure parameters and increase in crystallite size of doped samples magnesium ferrites were observed. A dramatic decrease in catalytic activity of catalysts obtained at 600 °C as compared to catalysts obtained at 300 °C was explicitly observed and this was grossly attributed to the elimination of surface hydroxyl groups as ascertained by FT-IR analysis. The initial magnesium ferrite demonstrated the highest catalytic activity under dark- (kˈ 0.0555 min⁻¹) and visible-light (kˈ 0.1029 min⁻¹) conditions. Catalytic efficiency of the lanthanides doped catalysts under UV-irradiation in accordance with the maximum appearance rate constant kˈ decreased in the following order Ce³⁺ > Dy³⁺ > La³⁺ ≈ MgFe₂O₄ > Sm³⁺ > Gd³⁺. The most active ferrites provided up to 99% of MB degradation in 60 and 20 min for visible- and UV-driven Fenton processes. Findings obtained from this study were observed to be competitive with other heterogeneous Fenton catalysts.     

The beneficial effect of alkali metal salt on supported aqueous-phase catalysts for olefin hydroformylation

Alkali metal salt modified SAP (supported aqueous-phase) rhodium catalysts prepared by coimpregnation method using alkali metal chloride were found to be active and selective for olefin hydroformylation. The salt addition promoted the formation of aldehydes with high selectivity, the aldehyde yield being increased more than 2.5 times at a proper salt/Rh ratio. Changes in stretching frequency of the carbonyl species were detected during ethene hydroformylation, which appeared at ca. 1625 cm^–1 on the non-modified SAP catalyst sample, while at ca. 1586 cm^–1 on the KCl-modified one, as shown by in situ IR spectroscopy. The results of a deuterium isotope effect experiment showed that the hydroformylation rate for aldehyde formation on SAP rhodium catalyst under atmospheric pressure of CO/D₂ was about 1.3 times faster than that under CO/H₂, implying that the rate-determining step involved in aldehyde formation is most probably a step related with hydrogen. The role of the alkali metal salt is discussed in relation with the reaction mechanism.     

Novel mesoporous polyoxometalate hybrid catalysts for heterogeneous oxidation of thioethers

K₆P₂W₁₈O₆₂ and K₁₄[NaP₅W₃₀O₁₁₀] polyoxometalate salts are synthesized and immobilized within MCM-48, SBA-3, SBA-15 and NH₃⁺ functionalized mesoporous silicas. The newly designed hybrid materials are studied as catalysts for oxidation of thioethers. Preyssler complex is found to be a more active catalyst compared to its Dawson analog. Texture and chemical composition of the silica framework is shown to have indispensable effect on oxidation efficiency, stability, and reusability of catalysts. Catalysts with larger pores are proved to be more proper for the oxidation of relatively large thioethers and functionalization improves catalyst's properties.     

Hydrogenation of CO2 to formic acid on supported ruthenium catalysts

We report on the preparation and application of novel heterogeneous supported ruthenium catalysts. The catalysts are active in the synthesis of formic acid from the hydrogenation of carbon dioxide and are characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction analysis and transmission electron microscopy. Abundant hydroxyl groups, which interact with the ruthenium components, play an important role in the catalytic reactions. Highly dispersed ruthenium hydroxide species enhance the hydrogenation of CO₂, while crystalline RuO₂ species, which are formed from the relatively high ruthenium content or the pH of the solution during preparation of the catalyst, restrict the production of formic acid. Optimal activity of ruthenium hydroxide as a catalyst for the hydrogenation of CO₂ to formic acid is achieved over a γ-Al₂O₃ supported 2.0 wt% ruthenium catalyst, which is prepared in a solution of pH 12.8 with NH₃·H₂O as a titration solvent. A possible hydrogenation mechanism for the hydroxide ruthenium catalyst is proposed.     

Membrane enhanced COD degradation of pulp wastewater using Cu2O/H2O2 heterogeneous Fenton process

Both activity and stability of the catalyst can be improved in heterogeneous Fenton reaction, in particular, with no limitation for the working pH and no production of the sludge. In this work, a combination of catalyst Cu₂O and pore-channel-dispersed H₂O₂ is proposed to treat the pulp wastewater. Degradation degree of CODs in the wastewater was up to 77% in the ceramic membrane reactor using Cu₂O powder (2.0 g·L^-1) and membranefeeding H₂O₂ (0.8 ml·L^-1) within 60 min. Evolution of ·OH radical formation in the advanced oxidation process was analyzed with a fluorescent method. Utilization efficiency of H₂O₂ was successfully enhanced by 10% with the membrane distributor. Further on, the catalyst recyclability was evaluated in a five-cycle test. The concentration of copper ions being dissolved in the treated water was monitored with ICP. After Cu₂O/H₂O₂ (membrane) treatment the effluent is qualified to discharge with COD concentration lower than 15 mg·L^-1 with regard to the national standard GB25467-2010.     

Effect of copper species and the presence of reaction products on the activity of methane oxidation on supported CuO catalysts

The activity of the various CuO species found in supported copper catalysts and the effect of the presence of reaction products, CO₂ and H₂O, was studied during the complete oxidation of methane. Series of copper catalysts supported on ZrO₂, Al₂O₃ and SiO₂ with different metal concentrations were analyzed under identical experimental conditions of reactant concentration and temperature. The catalysts were characterized by TPR, UV–vis spectroscopy and XRD. The results show that the activity of supported CuO is closely related to the kind of Cu species formed on the different supports. It was found that the Cu species formed on ZrO₂ and Al₂O₃ are dependent on the metal loading/support's surface area ratio, and that the activity of highly dispersed Cu is substantially higher than that of bulk CuO. In the case of silica, only the formation of bulk CuO was detected, accounting for the low activity of CuO/SiO₂ catalysts. The activity of highly dispersed Cu species formed on ZrO₂ is higher than those formed over Al₂O₃, and it is not significantly affected by the formation of bulk CuO on the surface. On the contrary, the activity of copper species formed on alumina decreases continuously as the Cu loading is increased. Thus, for the range of copper loading studied in this work, the activity of the catalysts, per gram of loaded Cu, follows the sequence: CuO/ZrO₂ > CuO/Al₂O₃  CuO/SiO₂. It was also found that CO₂ does not inhibits the activity of the CuO/ZrO₂ catalysts, while water inhibits the combustion reaction of methane, with an estimated reaction order of about −0.2 for temperatures between 360 °C and 420 °C.     

中空多孔磁性Fe3O4/纤维素/海泡石微球异相Fenton催化降解亚甲基蓝

为开发一种高效可循环利用的磁性生物质基催化剂，以微晶纤维素和纳米Fe3O4为原料，采用包埋法制得Fe3O4/纤维素（Fe3O4/MCC）溶液，将海泡石（SEP）掺入至Fe3O4/MCC中，制得磁性纤维素/海泡石复合微球（Fe3O4/MCC/SEP）。通过SEM、FTIR、VSM等对磁性微球的形貌、化学结构及磁性能进行了表征，探讨了微球作为芬顿催化剂对亚甲基蓝（MB）染料的降解效果及机理。结果表明，Fe3O4/MCC/SEP微球呈现出优异的中空多孔结构和超顺磁性。当MB浓度为10 mg/L、pH为3、Fe3O4/MCC/SEP的投入量为0.02 g，H2O2用量为5 mL时，反应240 min对MB的Fenton催化降解率高达99%。此外，经过5次循环利用后，对MB的降解率仍达83%。     

The role of hydrogen in methanol synthesis over copper catalysts

The experimental observation that the activity of a series of zinc oxide supported copper catalysts is related to the surface area of the copper is examined in the light of recent evidence that hydrogen spillover from copper to zinc oxide is facile. A model is proposed which explains the effect of zinc oxide on copper in terms of a reversible transfer of hydrogen between copper and zinc oxide. It is suggested that therate determining step normally occurs on the surface of the copper but that therate of reaction can be dependent on the availability of spillover hydrogen from the zinc oxide.     

Friedel–Crafts benzoylation of p-xylene over clay supported catalysts: novelty of cesium substituted dodecatungstophosphoric acid on K-10 clay

2,5-Dimethylbenzophenone is used extensively as a UV light stabilizer in plastics, cosmetics and films and produced by the benzoylation of p-xylene using homogeneous catalysts which pose several problems. The benzoylation of p-xylene with benzoyl chloride was carried out in a batch reactor using clay supported catalysts such as 20% (w/w) dodecatungstophosphoric (DTP) acid/K-10, 20% (w/w) Cs_2.5H_0.5PW₁₂O₄₀/K-10, 20% (w/w) ZnCl₂/K-10 and K-10 itself and sulfated zirconia. Amongst these catalysts, 20% (w/w) Cs_2.5H_0.5PW₁₂O₄₀/K-10 was found to be a better catalyst which could be reused without any further chemical treatment eliminating the effluent disposal problem. This catalyst was fully characterized. The reaction obeys the Eley–Rideal type of mechanism with a weak adsorption of the benzoylating species.     

The generation of hydroxyl radicals by hydrogen peroxide decomposition on FeOCl/SBA‐15 catalysts for phenol degradation

Iron oxychloride (FeOCl) supported on mesoporous silica (SBA‐15), as a Fenton‐like solid catalyst for phenol degradation, showed supreme activity for production of hydroxyl radical (HO·) by H₂O₂ decomposition, and the generation capacity was comparable to the conventional Fenton reagent (Fe²⁺+H₂O₂). The structure of FeOCl was characterized with spectroscopies. The generation of HO· species during the reaction was detected using 5,5‐dimethyl‐1‐pyrroline N‐oxide trapped electron paramagnetic resonance. Furthermore, the kinetics in detail was driven for the creation and diffusion of HO· by H₂O₂ decomposition over FeOCl, which follows a first‐order rate through a two‐step reaction. With the combination of the catalyst structure and kinetic parameters, the plausible mechanism for H₂O₂ decomposition during the oxidative degradation of phenol was rationalized. As a Fenton‐like solid catalyst, FeOCl/SBA‐15 is a promising alternative for the removal of low‐level organic contaminates from water. © 2014 American Institute of Chemical Engineers AIChE J, 61: 166–176, 2015     

With different structure ligands heterogeneous Ziegler-Natta catalysts for the preparation of copolymer of ethylene and 1-octene with high comonomer incorporation

Comparison with the conventional Ziegler-Natta catalyst TiCl₄/MgCl₂ (I), the modified supported Ziegler-Natta catalysts (iso-PentylO)TiCl₃/MgCl₂ (II) and (BzO)TiCl₃/MgCl₂ (III) were prepared as efficient catalysts for copolymerization of ethylene with 1-octene. The complexes (II) and (III) were desirable for the production of random ethylene/1-octene copolymers coupled with higher molecular weight, higher comonomer incorporation within copolymer chain and good yield even at high temperature 80 ^°C and fairly low Al/Ti molar ratio of 100. The effects of catalysts ligands, Al/Ti molar ratio, polymerization temperature, as well as concentration of 1-octene on the catalytic activity, molecular weight and microstructure of the copolymer were investigated in detail. The structure and properties of the copolymers were characterized with ¹³C NMR, GPC, DSC and WAXD. The kinetic results also indicate that these catalysts (II) and (III) show higher catalytic activity and the produced polymers feature higher molecular weight, because of lower ratio of K_trm/K_p and K_tra/K_p, and higher ratio of K_tra/K_trm which indicates that chain transfer to cocatalyst is predominant.     

On the problem of the activity in methanol synthesis of supported,unpromoted copper catalysts

It is shown that a pure Cu catalyst is inactive in methanol synthesis. Activity can be invoked by small amounts of (alkali) promoters. Contaminations present in the current commercial supports are leached out during impregnation and promote Cu sufficiently to produce methanol. Contaminations-promoters slow down the reduction of Cu precursors.     

The heterogeneous catalyst system for the continuous conversion of free fatty acids in used vegetable oils for the production of biodiesel

Biodiesel produced by the transesterification of vegetable oils (VOs) has recently become more attractive on account of its environmental and economical benefits. In this work, a heterogeneous catalyst system was developed for the production of biodiesel from used VOs using a continuous process. The free fatty acids (FFA) contained in the used VOs, which cause several severe problems in transesterification catalysis, were converted to fatty acid methyl esters (FAME) before the main biodiesel production process. The activities of several heterogeneous catalysts on the conversion of FFA were tested, with a WO₃/ZrO₂ catalyst finally being selected. A method for preparing pellet-type catalysts was also developed. The pellet-type WO₃/ZrO₂ catalyst showed highly active and durable catalytic activities in the continuous flow process. The steady state conversion of ca. 70% was obtained in a 140 h durability test. The acidic property and catalytic activity of WO₃/ZrO₂ were attributed to the oxidation state of tungsten.