Photooxidation in Water by New Hybrid Molecular Photocatalysts Integrating an Organic Sensitizer with a Polyoxometalate Core

Hybrid compounds consisting of an organic sensitizer and a polyoxometalate unit were synthesized following two strategies: a) the covalent functionalization of lacunary decatungstosilicate with organosilylfulleropyrrolidines; b) the charge interaction between cationic sensitizers and the polyoxoanions, yielding electrostatic aggregates. These hybrid complexes effect catalytic photooxygenation in water under heterogeneous conditions, 25 °C and O₂ (1 atm), using visible light irradiation (λ>375 nm). As representative target substrates, phenol (4 mM) is oxidized in 150 min with a COD loss up to 30% (TON up to 50), while L ‐methionine methyl ester (15 mM) undergoes selective photooxygenation to the corresponding sulfoxide in 90 min (TON up to 200). The photocatalyst stability has been evaluated on the basis of system recycling along three oxidation runs. The inhibition exerted by sodium azide, a typical ¹O₂ quencher, suggests the occurrence of a Type II photooxidation mechanism.     

A new reactor coupling heterogeneous Fenton‐like catalytic oxidation with membrane separation for degradation of organic pollutants

BACKGROUND: There is growing interest in employing heterogeneous Fenton‐like catalysts in slurry to obtain higher activity. However, fine size particles create problems associated with recovery from the treated water. Therefore, it is highly desirable to develop a novel Fenton‐like process that not only has high degradation efficiency of organic pollutants, but also allows for easily reusing the catalysts. RESULT: A new reactor was investigated by coupling the heterogeneous Fenton‐like oxidation with membrane separation. Results showed that the FeY catalyst could be almost filtrated by a submerged micro‐filtration membrane in the reactor to continuously activate H₂O₂. For a FeY dose of 1 g L^?1 and a residence time of 120 min, the degradation efficiency of AO II reached 97%. CONCLUSIONS: In the new reactor, degradation of AO II occurred continuously and efficiently without an additional FeY separation process. The treatment capacity of this FeY catalyst for wastewater containing 100 mg L^?1 AO II in the reactor was estimated to be 82 times that of a reactor in which the catalyst could not be reused. The distinguishing technical feature of this reactor was the reuse of the Fenton‐like catalyst. Copyright © 2011 Society of Chemical Industry     

光催化分离膜的制备及其在水处理中的应用

光催化分离膜将膜分离与光催化结合在同一处理单元中,可发挥膜分离作用,同时也可以利用光催化剂高效降解水中的有毒有害污染物,提高膜的抗污染性能和水处理效率。因此是水处理领域的研究热点,并显示出巨大的应用潜力。本文综述了基于二氧化钛（TiO₂）、氧化锌（ZnO）、石墨相氮化碳（g-C₃N₄）和氧化钨（WO₃）四种常用催化剂的光催化分离膜的研究概况,重点对光催化分离膜的制备方法和性能进行了总结,光催化分离膜具有良好的发展前景,制备高效、稳定的可见光响应光催化分离膜是未来的发展趋势。     

Kinetics of the gas-solid heterogeneous photocatalytic oxidation of trichloroethylene by near UV illuminated titanium dioxide

Kinetics of the gas/solid heterogeneous photocatalytic oxidation of dilute trichloroethylene (TCE) vapors by ultraviolet-illuminated titanium dioxide have been determined using a fixed-bed dynamic photoreactor. Reaction rate dependences on inlet TCE, oxygen and water vapor concentrations were found to consist of both reactant sensitive and insensitive regions. In the reactant sensitive regions, measured limiting apparent reaction rate orders for TCE, oxygen and water vapor are 0.8, 1.7 and — 3, respectively. Water vapor in the reactant stream lowersinitial reaction rates relative to corresponding water free conditions, but is required to sustain photocatalytic activity for extended periods of time.     

Hybrid organic-inorganic solids for heterogeneous asymmetric catalysis

This paper provides a short review of recent progress in the design and synthesis of chiral organic–inorganic hybrid solids and their applications in heterogeneous asymmetric catalysis. Homochiral hybrid solids containing catalytic sites can be readily prepared by linking appropriately designed chiral bridging ligands with metal ion or metal cluster nodes. Heterogeneous asymmetric catalysts with enantioselectivity as high as 99.2 and turnover number (TON) as high as 20,000 have been obtained based on these hybrid organic–inorganic solids. The modular nature of the present approach promises to lead to a variety of practically useful heterogeneous asymmetric catalysts for many organic transformations.     

多相催化氧化伯醇制备羧基化合物研究进展

伯醇催化氧化制羧基化合物是有机合成中一类极为重要的转化过程,具有广泛的应用场景。对于多相催化系统,高效催化剂的制备一直是研究的热点和难点。本文对近年来涉及多相催化氧化伯醇制备羧基化合物的文献进行了全面的梳理。从单金属和双金属活性组分,以及是否采用载体等角度,系统评估了伯醇氧化多相催化剂的发展现状和趋势,并展望了多相催化在工业应用中的发展前景和挑战。     

乙醇缩合制高碳醇(C6+醇)多相催化剂研究进展

以乙醇为原料制备其他高附加值化工产品近期得到了广泛关注,特别是乙醇基于Guerbet反应缩合制备高碳醇(C₆₊)的过程更成为这一领域的研究热点。本文着重报道了近年来乙醇转化为高碳醇过程的几种典型的多相催化剂,包括羟基磷灰石(HAP)、类水滑石(LDHs)以及各种负载型金属催化剂的研究开发现状,分析比较了各类催化剂的优势与不足,结合反应机理针对催化剂对高碳醇选择性不高的原因进行了讨论,对理想催化剂的设计和改进进行了展望,指出应该通过促进Guerbet反应中的羟醛缩合过程增加高碳醇的选择性。金属负载型催化剂对该反应控制步骤的加速作用显著,而金属位点和载体表面酸碱活性位点的精细调控以及特定催化剂形貌结构的控制合成则是该领域未来的研究重点。     

苯乙烯分子氧环氧化多相催化剂研究进展

针对近年来国内外苯乙烯分子氧环氧化多相催化剂的研究进展进行了综述,主要介绍了钴系、金系、铁系及其他催化体系等催化剂。其中,钴系催化剂活性高,工艺条件温和,绿色环保,但价格昂贵;金系催化剂在低温条件下对苯乙烯分子氧环氧化表现出良好的活性;铁系催化剂活性低,但经济性好。指出负载型钴系、金系催化剂在苯乙烯分子氧环氧化研究中有潜在的应用前景。     

Strategies for oxidation catalyzed by polyoxometalates at the interface of homogeneous and heterogeneous catalysis

A basic premise behind the use of polyoxometalates in oxidation chemistry is the fact that polyoxometalates are oxidatively stable. This, a priori, leads to the conclusion that for practical purposes polyoxometalates would have distinct advantages over widely investigated organometallic compounds that are vulnerable to decomposition due to oxidation of the ligand bound to the metal center. Since polyoxometalate synthesis is normally carried out in water by mixing the stoichiometrically required amounts of monomeric metal salts and adjusting the pH to a specific acidic value many structure types are accessible by variation of the reaction stoichiometry, replacement of one or more addenda atoms with other transition or main group metals, and pH control. The structural variety available has enabled the use of polyoxometalates as catalysts for oxidation of hydrocarbons and functionalized organic substrates (alcohols, amines, sulfides, etc.) with a wide range of oxygen donors ranging from molecular oxygen, hydrogen peroxide, nitrous oxide, ozone, alkyl hydroperoxides, periodate, sulfoxide and others. The wide purview of oxidation reactions is enabled because the structural variety leads to oxidation through a number of different mechanistic motifs.From a synthetic organic point of view, the most applicable uses of polyoxometalates as catalysts involve the green oxygen donors – hydrogen peroxide and molecular oxygen. Since practical applications are in hand in this area, practical considerations concerned with catalyst recycle and/or recovery and the elimination of environmentally problematic solvents are also coming to the forefront. In this paper, we will present some of our activities in the area of catalyst engineering for catalytic synthetic applications by polyoxometalates including: (a) catalytic mesoporous solids from organic-polyoxometalate hybrid materials, (b) fluorous phase polyoxometalates with and without fluorous solvents and (c) the use of aqueous biphasic media for oxidation with hydrogen peroxide.     

低温低压下非均相催化氧化处理焦化废水实验研究

研究了非均相催化剂在低温低压条件下处理焦化废水的效果,通过改变催化剂的载体、浸渍溶液的种类及浓度、pH值、反应时间、催化剂的投加量、H2O2(质量分数30%)的投加量等因素,得出在低温低压下非均相催化氧化处理焦化废水的最佳条件:采用经Cu(NO3)2溶液浸渍后的γ-Al2O3为催化剂、在pH值为3、催化剂体积分数为40%、H2O2投加体积分数为4%、反应时间在3 h以上时处理效果较好.原水CODCr由4 540 mg/L降至600mg/L以下,氨氮由552 mg/L降至160 mg/L以下.     

多相催化臭氧氧化法处理印染废水的研究

采用浸渍法制备了活性炭负载铁锰氧化物的催化剂用于对印染废水的多相催化臭氧氧化处理,当铁锰质量比为1∶2时,催化剂处理效果最佳。多相催化臭氧氧化工艺的最佳运行参数为:处理时间60 min、臭氧通气量0.2 L/min、催化剂投加质量20 g、废水pH=5。经多相催化臭氧氧化处理后,印染废水的COD、氨氮、TP、色度去除率分别为81.7%、90.2%、97.6%、99.1%,去除效果较好。     

甲烷选择性氧化制甲醛/甲醇多相催化剂研究进展

甲烷是天然气、页岩气等化石能源的主要成分,储量十分丰富.由于甲烷分子结构高度稳定,其高效活化与选择性转化具有很大的挑战性,被认为是催化反应领域的"圣杯",因此,如何在温和条件下实现甲烷选择性氧化为高附加值的含氧化合物(如甲醇、甲醛)成为研究热点.近几十年来,研究者在甲烷选择性氧化催化剂的设计与制备方面开展了大量卓有成效...     

Selection of oxygen permeation models for different mixed ionic‐electronic conducting membranes

Permeation data of several mixed ionic‐electronic conducting (MIEC) membranes were analyzed by two oxygen permeation models (i.e., Zhu's model and Xu–Thomson's model), respectively, to find a concise method to guide the choice of permeation models. We found that Zhu's model can well fit the permeation data of perovskite‐type membranes, like Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3‐δ (BSCF) and BaCe_0.05Fe_0.95O_3‐δ (BCF), and dual‐phase membranes, like 75 wt % Ce_0.85Sm_0.15O_1.925–25 wt % Sm_0.6Sr_0.4Al_0.3Fe_0.7O_3‐δ (SDC‐SSAF), whose oxygen vacancy concentrations are almost independent of the oxygen partial pressure at elevated temperatures. However, Zhu's model was not appropriate for membranes whose oxygen vacancy concentration changed obviously with oxygen partial pressure at elevated temperatures, such as La_0.6Sr_0.4Co_0.2Fe_0.8O_3‐δ (LSCF) and La_0.7Sr_0.3CoO_3‐δ (LSC). On the contrary, Xu–Thomson's model can fit the data of LSCF and LSC well, but it is inapplicable for BSCF, BCF, and SDC‐SSAF. Therefore, the dependence of oxygen vacancy concentration on oxygen partial pressure was suggested as an index for the selection of the permeation models. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4043–4053, 2017     

New aluminum mesh from recyclable material for immobilization of TiO2 in heterogeneous photocatalysis

This study presents a new aluminium mesh made out of soda can rings as a support for titanium dioxide (TiO₂) in the degradation of the synthetic dyes Bordeaux Red (BR) and Tartrazine (TT). Three pre-treatments including calcination and acidification steps were investigated in order to select the most efficient immobilization procedure for photocatalysis application. Raw and titania-aluminum meshes were characterized by scanning electron microscopy, x-ray diffraction, diffuse reflectance, and Fourier transform infrared spectroscopy. The material presented itself as a suitable alternative in the immobilization of titania for wastewater treatment. Preliminary tests selected H₂O₂/TiO_{2(suspension)} oxidation systems under natural sunlight and germicidal lamps (UVC) exhibiting 97.2% and 99.5% of degradation in 180 minutes, respectively. Immobilized TiO₂ systems reached high degradation rates (>99%) after 180 minutes in both UVC and solar light-based processes. An experimental planning study was carried out for the processes in order to find the best operational conditions and pseudo-first-order model fit well the removal data (discolouration rates of in the order of 0.0274 and 0.0145 min⁻¹ for UVC and solar light systems, respectively). Parameters such as TOC, COD, and turbidity, revealed a great improvement in the environmental quality of the water after the treatment and acute toxicity bioassays demonstrated a significant decrease in toxicity for both systems after the treatments. The TiO₂-meshes demonstrated high performance in the removal after five cycles of operation. Therefore, the new immobilization procedure demonstrated that the TiO₂-aluminum mesh is a feasible option for wastewater treatment and photocatalysis.     

环己烯分子氧氧化多相催化剂研究进展

根据催化剂主组分的不同,综述了国内外环己烯分子氧氧化多相催化剂的研究进展;主要介绍了钴系、锰系、铁系及镍系催化剂在环己烯分子氧氧化中的应用及其优缺点.指出负载型纳米金催化剂与传统的钴、锰催化剂相结合制备双活性中心催化剂在环己烯分子氧氧化中有较好的应用前景.     

TiO2-coated glass hollow fiber membranes: preparation and application for photocatalytic methylene blue removal

A glass hollow fiber membrane coated with TiO₂ was successfully synthesized by dip-coating and calcination. In addition, the effects of the calcination temperature, number of coating layers, and treatment method on the photocatalytic removal of methylene blue from wastewater by the membrane were investigated. The results showed that the TiO₂-coated membrane calcined at 550 °C was uniform. It showed good photocatalytic and anti-fouling properties. As compared to the basement membrane, the TiO₂-coated membrane showed significantly improved photocatalytic removal of methylene blue. It showed a methylene blue removal degree as high as 97.2% and could be recycled multiple times by a simple treatment. The methylene blue removal degree of the membrane remained 92.3-93.6% after five recycling operations. Therefore, the membrane prepared via the simple method proposed in this study could be used as an efficient photocatalyst to remove methylene blue from wastewater.     

稀土掺杂TiO2光催化还原CO2

采用溶胶-凝胶法制备了稀土掺杂TiO₂纳米光催化剂,并应用于光催化还原CO₂/H₂O体系中。通过XRD对光催化性能进行表征,研究稀土离子掺杂和焙烧温度对光催化性能的影响。结果表明,稀土La和Ce的加入可以抑制TiO2的晶相转变,提高光催化性能。催化剂800 ℃焙烧可达到最好的光催化活性,在反应时间7 h、CO₂流量200 mL·min^-1和反应液中NaOH与Na₂SO₃浓度均为0.10 mol·L^-1条件下,甲醇产率高达315.49 μmol·g^-1。并对稀土掺杂TiO₂催化剂光催化还原CO₂的机理进行了探究。     

Nanocrystalline Magnesium Oxide‐Stabilized Molybdenum: An Efficient Heterogeneous Catalyst for the Aerobic Oxidation of Alcohols to Carbonyl Compounds

A nanocrystalline magnesium oxide‐stabilized molybdenum(VI) complex catalyzed the oxidation of primary and secondary alcohols to carbonyl compounds in excellent yields using molecular oxygen as stoichiometric oxidant. The nanomaterials with their three‐dimensional structure and defined size and shape act as suitable supports for metal complexes. The catalyst can be reused for four runs without any significant loss of activity.     

Hybrid sol–gel membranes of polyacrylonitrile–tetraethoxysilane composites for gas permselectivity

Sol–gel reaction of tetraethoxysilane (TEOS) with fumed silica–polyacrylonitrile (PAN) membrane was carried out to prepare hybrid gas permeable membranes for oxygen and nitrogen separation. Various amounts of fumed silica microparticles with a few μm diameters were compounded in PAN–dimethylsulfoxide (DMSO) solution. After casting of the viscous compound solution on a flat sheet with 100 μm thickness, DMSO was evacuated under vacuum at 80°C. Then, the silica–PAN composite membranes were treated with TEOS for 1 day at 40°C in methanol. Air permeation was examined and compared in silica–PAN composite membranes with and without TEOS treatment. The latter hybrid membranes showed selective oxygen permeability, which depended on amounts of fumed silica in the membrane. The TEOS hybrid PAN membranes have a high ability of oxygen permselectivity for O₂/N₂ gas mixture with α(O₂/N₂) = 13–17, when the silica content was in the range of 13–20 wt %. This is attributed to siloxane network formation in hybrid silica–PAN composite membranes. Favorable siloxane network formation resulted in high oxygen permeability of the hybrid composite membranes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1752–1759, 2003     

分子氧氧化苯乙烯制备环氧苯乙烷的多相催化剂研究进展

综述了分子氧氧化苯乙烯制备环氧苯乙烷的多相催化剂研究进展,重点介绍了Co系催化剂在苯乙烯环氧化方面的应用。其中,负载在Beta型分子筛上的Co-Beta催化剂具有较高的催化活性、选择性及稳定性。