乙二醇与二甘醇混合醇用杂多酸催化制取二氧六环

试验了用杂多酸为催化剂,以二甘醇与乙二醇的混合物为原料制取二氧六环,得到了适宜的催化剂和工艺条件。     

Additives assisted catalytic cyclo-dehydration of diethylene glycol in near-critical water

The additives assisted the cyclo-dehydration of diethylene glycol (DEG) reaction was studied in near-critical water (NCW). Zinc chloride (ZnCl₂) and sodium carbonate (Na₂CO₃) were selected to investigate their effects on the cyclo-dehydration of diol. The influences of reaction temperature, time, pressure, reactant/water ratio (r/w) and the concentration of additives on the product yield of the cyclo-dehydration of DEG were examined. The results showed that the final obtained product was primarily 1,4-dioxane, resulting from the cyclo-dehydration of DEG in NCW. The yield of 1,4-dioxane was only 9.84 wt.% in pure water by reacting at 340 °C for 240 min, but the maximum yield of 1,4-dioxane could reach as high as 50.89 wt.% in the solution of 0.50 wt.% ZnCl₂ at 340 °C for 120 min, and the conversion of DEG was 91.94 wt.%. The complete conversion of DEG was obtained in 1.00 wt.% ZnCl₂ at 340 °C for 120 min, but the yield of 1,4-dioxane was only 10.18 wt.%. In the case of Na₂CO₃, it did not have significant promotion effect on the cyclo-dehydration of DEG reaction. All these experimental results demonstrated that ZnCl₂ had the positive effects on the dehydration of DEG while Na₂CO₃ depressed the reaction. Based on these results, a possible reaction mechanism and pathway was proposed in NCW.     

Lithium-mediated ring opening of 1,4-dioxane and structural characterization of a Li12O12 truncated octahedron

The equimolar reaction of ^tBuLi with 4-Cl-2,6-Me₂-C₆H₂OH (ArOH) in 1,4-dioxane led to the unexpected formation of the mixed-anion, 1D polymer [(ArO)₂(RO)₄Li₆ · (diox)]_∞, 1 (where RO = H₂CC(H)OCH₂CH₂O⁻). Incorporation of the alkoxy vinyl ether is due to cleavage of 1,4-dioxane by ^tBuLi. Compound 1 can also be prepared rationally by the reaction of ⁿBuLi with ethylene glycol vinyl ether and ArOH in 1,4-dioxane solution. Direct lithiation of ethylene glycol vinyl ether results in the formation of the alkoxide [ROLi]₁₂, 2. The crystal structure of 2 reveals an unusual truncated octahedral arrangement in the solid state, where each metal is chelated by a vinyl ether subunit.     

Evaluation of O3/UV and O3/H2O2 as Practical Advanced Oxidation Processes for Degradation of 1,4-Dioxane

The degradation of 1,4-dioxane was investigated on a laboratory scale. The extents of degradation and/or removal of 1,4-dioxane by ozonation at pH 6–8, UV irradiation, aeration, and addition of H₂O₂ were very limited. On the other hand, the degradation of 1,4-dioxane by O₃/UV and O₃/H₂O₂ was accelerated compared with the above respective methods. The amounts of 1,4-dioxane degraded per amount of ozone consumed in O₃/UV and O₃/H₂O₂ were also higher than in ozonation. The amount of 1,4-dioxane degraded in O₃/UV was affected by the intensity of UV irradiation, and that in O₃/H₂O₂ was affected by the amount of H₂O₂ added only in the case of a high initial concentration of 1,4-dioxane.     

Direct electrochemical regeneration of enzymatic cofactor 1,4‐NADH on a cathode composed of multi‐walled carbon nanotubes decorated with nickel nanoparticles

Multi‐walled carbon nanotubes (MWCNTs) were grown on a stainless steel mesh and decorated with nickel nanoparticles (Ni NPs). The developed Ni NP‐MWCNT material was then used as a cathode in an electrochemical batch reactor to electrocatalytically convert NAD⁺ to enzymatically‐active 1,4‐NADH. The regeneration of 1,4‐NADH was studied at various electrode potentials. At electrode potential of ?1.6 V, a very high recovery (relative amount of 1,4‐NADH in the product mixture) was obtained, 98 ± 1 %. In comparison, to achieve the same recovery on a non‐decorated MWCNT cathode, a much higher cathodic potential was needed (?2.3 V), establishing the importance of Ni NPs on the electrocatalytic activity in reducing NAD⁺ to 1,4‐NADH. It was postulated that hydrogen adsorbs on Ni NPs immobilized on MWCNTs to form Ni‐H_ads, and this activated hydrogen rapidly reacts with neighbouring NAD‐radicals, preventing the dimerization of the latter species, ultimately yielding 1,4‐NADH.     

1,4—二氧六环制备工艺的研究

介绍了由二甘醇为原料制备１，４－二氧六环的工艺，二甘醇脱水反应沸石型催化剂，通过加入共沸剂的方法分离反应产物。１，４－二氧六环的产品质量达到了国外同类产品的质量指标。     

磷酸/活性炭催化剂的制备及其在乙二醇脱水制1,4-二氧六环中的应用

以处理过的活性炭为载体,采用浸渍法制备了不同负载量的磷酸/活性炭催化剂。采用XRD、XRF、SEM、EDS、TEM、NH_3-TPD和N_2吸附-脱附等对催化剂进行表征分析,并将制备的催化剂应用于乙二醇脱水制1,4-二氧六环的反应。表征分析表明,制备的催化剂具有良好的微观形貌、孔道结构和酸性质;反应结果表明,磷酸负载质量分数为8%的催化剂反应效果最好,在此条件下,乙二醇转化率100%,1,4-二氧六环选择性达到90.6%,具有良好的应用前景。     

Optimization of flocculation conditions for the separation of TiO2 particles in coagulation-photocatalysis hybrid water treatment

TiO₂ mediated photocatalysis can decompose organic micropollutants (e.g., 1,4-dioxane) in water, but the removal of used TiO₂ particles is challenging. Although retrofitting enhances the particle separation efficiency, optimizing a coagulation/flocculation process should be most suitable for existing treatment plants. Therefore, the present study investigated the separation characteristics of TiO₂ particles added to drinking water treatment processes along with a polyaluminum coagulant. TiO₂ photocatalysts were able to achieve significant degradation of 1,4-dioxane (∼100% within 50 min) as well as dissolved organic matter (∼75% within 150 min) at a TiO₂ dose of 1.0 g/L under UV irradiation. Although the TiO₂ particle separation efficiency was sensitive to G values, maximal removal occurred at a G value of <34 s⁻¹ with a coagulant concentration of >8 mg/L as Al₂O₃. Sand filters had the capability to remove residual turbid materials and thus, the turbidity of the final product water dropped to as low as 0.1 NTU when the coagulation/flocculation process was preceded. The final effluent quality was comparable to that of a 0.45-μm membrane filter. The post separation of the TiO₂ photocatalysts dispersed for emergency water treatment to degrade 1,4-dixoane was successfully achieved with an optimal coagulant dose, proper flocculation, and sand filtration.     

二甘醇的综合利用技术新进展

二甘醇（DEG）是环氧乙烷用水合法生产乙二酵（EG）的副产物,随着我国乙二醇工业的迅速发展二甘醇产量不断增加,充分利用二甘醇资源开发下游产品、拓展二甘醇的用途越来越受到重视。综述了国内二甘醇的综合利用进展,介绍了二甘醇的直接利用途径和二甘醇合成吗啉、二甘醇醚、二甘醇酯、1,4-二氧六环、二甘酸和二甘醇胺等精细化学品的利用情况。     

Fabrication of nanometer-to-micron sized Cu2O single crystals by electrodeposition

Nanometer-to-micron sized cuprous oxide (Cu₂O) single crystals were fabricated on Au/Pd sputter-coated silicon wafer and stainless steel cathode substrates by electrodeposition in CuSO₄ at pH 4.0 at room temperature (25 °C) with no additives. The Cu₂O crystals were generally of an octahedral shape with sizes ranging from 100 nm to 400 nm on Si wafer, and 1 μm to 3 μm on stainless steel substrates respectively. Very small crystals of a spherical shape were also observed under low applied voltage. Transient crystal shapes observed on the cathode near the electrolyte surface suggest that growth slows down once {1 1 1} free surfaces are formed, and this explains the robust observation of the octahedral crystal shape. The effect of electrodeposition parameters such as deposition voltage and deposition time on the size of the crystals and their coverage on the substrates was investigated. Apart from the cathode, similar octahedral Cu₂O nanocrystals were also found to deposit on the Cu anode used. This work provides a method to fabricate Cu₂O crystals on both electrodes in a single step.     

Advanced oxidation of catechol: A comparison among photocatalysis, Fenton and photo-Fenton processes

The aim of this work was to compare the behaviour of Fenton, photo-Fenton and photocatalysis processes to treat catechol solutions which are pollutants occurring in wastewaters from many industries. The effect of different process parameters, such as initial catechol concentration, H₂O₂/FeSO₄ ratio in Fenton and photo-Fenton oxidation, TiO₂ loadings in photocatalysis and irradiation times has been studied.Fenton and photo-Fenton (H₂O₂/FeSO₄ = 600/500 (w/w) and 30 min reaction time) processes allowed us to achieve a high efficiency in the mineralization of catechol (COD removals up to 83% and 96% respectively), and removal of aromaticity (UV₂₈₀) (up to 93% and 98% respectively), for an initial catechol concentration of 110 mg/l. On the opposite, photocatalysis was not effective in the removal of higher catechol concentrations (110 and 200 mg/l), whereas a significant removal of aromaticity versus time was observed for 50 mg/l. Gas chromatography-mass spectrometry analysis, performed under selected treatment conditions, showed that total removal of catechol can occur after Fenton (2000/500 w/w; 30 min), photo-Fenton (600/500 w/w; 30 min), and photocatalysis (3 g TiO₂/l; 240 min) treatments.     

Preparation and characterization of high initial bonding strength reactive hot melt polyurethane adhesive derived from phthalate polyester polyols

A series of phthalate polyester polyols (PEs) were synthesized via a polycondensation reaction with phthalic anhydride (PA) and different glycols, such as neopentyl glycol (NPG), ethylene glycol (EG), diethylene glycol (DEG), 2-methy-1,3-propanediol (MPO), 1,4-butylene glycol (1,4-BDO) and trimethylolpropane (TMP). Reactive hot melt polyurethane adhesive (HMPUR) with high initial bonding strength was then prepared by poly(propylene glycol) 2000 (PPG-2000), Dynacoll 7360 with these resultant PEs. Effects of different glycols on the glass transition temperature (T_g) and viscosity of the PEs were investigated. Besides, influences of these resultant PEs on the water resistance, bonding strength, thermal stability and surface morphology of the HMPUR were further discussed. The experimental results showed that T_g and viscosity of the PEs decreased with the increase of the chain flexibility of diols. The initial bonding strength of the HMPUR increased with the increase of T_g of the PEs. The hydrogen bonds and cross-linking structure of the HMPUR will also lead to the increase of the bonding strength. In addition, the water resistance of HMPUR was improved by the cross-linking structure and lateral methyl groups of the PEs, while the thermal stability changed little. The surface morphology of the HMPUR showed that all samples have two phase structures and the HMPUR based on DEG and 1,4-BDO exhibited weak phase separation.     

Ultrasonic studies of solutions of styrene-butadiene copolymers

Ultrasonic attenuation measurements on solutions of linear and star styrene-butadiene-styrene block copolymers over a frequency range from 10⁶ to 10⁸ Hz are reported. Activation parameters for the segmental relaxation process in 1,4-dioxane, cyclohexane and toluene were obtained from temperature variation studies. Both the amplitude and the temperature dependence of the relaxation varied with change in solvent.     

Electrochemically Assisted Photocatalysis of Hybrid WO3/TiO2 Films: Effect of the WO3 Structures on Charge Separation Behavior

In this study, the photocatalysis of hybrid WO₃/TiO₂ films with different loadings of WO₃ were investigated with and without potential bias. It was clearly indicated that hybrid WO₃/TiO₂ films show less photo-reactivity under only UV-irradiation, while more effective photocatalysis under potential bias than either TiO₂ or WO₃ by themselves, their photocatalytic performance depending on the loadings of WO₃. In particular, a hybrid WO₃/TiO₂ film involving an amorphous-like WO₃ phase plays a significant role in an enhancement of the electrochemically assisted photocatalysis.     

Passivity of OC404 steel modified electrochemically with CeO2-Ce2O3 layers in sulfuric acid media

The effect of cerium oxides film, formed electrochemically on OC404 stainless steel (SS), upon the corrosion behavior of steel in 0.1N H₂SO₄ was investigated. The modification of the steel surface by deposition of cerium oxides films was found to improve the steel corrosion resistance. A linear dependence between the stationary corrosion potential of the cerium oxides/SS system and the cerium concentration in the oxide film was established. The shift of the corrosion potential in the positive direction was found to depend on the proceeding of a depolarizing cathode reaction of CeO₂ reduction (instead of the hydrogen depolarizing reaction) occurring on the cathodic zones, formed by this oxide. On the basis of XPS analyses of the samples, subjected to real corrosion under the conditions of self-dissolution, a pronounced drop of the surface concentration of CeO₂ was established. This is a proof of the occurrence of an effective cathode process of CeO₂ reduction to Ce₂O₃, which was then dissolved in H₂SO₄. Data were obtained (XPS) on the composition and structure of the surface film (SEM) after electrodeposition of cerium oxides and after corrosion in the sulfuric acid medium under consideration for time intervals ranging from 50 up to 1000 h. The ICP-AES studies acquired data on the quantity of dissolved elements, forming the passive layer. After exposure to the corrosive medium, the deposited layer showed enrichment in oxides of chromium and aluminium. The passive film on stainless steel, modified in this way, proved to be more stable to the effect of aggressive sulfuric acid medium, compared to the case of natural passive film.     

Kinetic Analysis of Heterogeneous Photocatalysis: Role of Hydroxyl Radicals

This article provides the current research activities that concentrate on the role of hydroxyl radicals in heterogeneous photocatalysis by transition metal oxides for different nanostructures. We devote most attention to Al-based Fe₂O₃ nanostructures that have been synthesized using chemical methods. The visible light photocatalytic activity of nanocrystalline pure and Al-based Fe₂O₃ photocatalysts for degradation of Salicylic acid, 4-Cholorphenol, and Acid orange 7 (Azo dye) is reported. The catalytic activity and selectivity for organic species are remarkably influenced by the size of the different photocatalyst. Utilization of various structures, advanced oxidation processes, heterojunction between Al-based Fe₂O₃ and TiO₂, and application of solar energy for heterogeneous photocatalysis of water impurities were discussed. Extent of complete mineralization of such compounds by measuring COD and TOC was discussed. We conclude this review with personal perspectives on the directions towards which future research on this new class of nanostructured materials for photocatalysis might be directed.     

环境中1,4-二烷污染处理技术研究进展

新型污染物1,4-二烷广泛分布于地表水、地下水和饮用水环境中。常规水处理手段对1,4-二烷难以奏效,因而其污染处理技术成为了关注的热点。本文主要针对1,4-二烷污染的处理方法进行了综述。首先对1,4-二烷的性质及分布特征进行了总结,比较了国内外已有的污染调查状况和控制标准,然后重点从物理、化学和生物法三个方面介绍了近年来1,4-二烷污染处理技术的最新研究进展,且分析了不同技术的作用机制、优缺点及可行性,并对不同技术的处理效率进行了归纳总结。文中特别指出了生物修复的难题,即氯代烃、重金属对微生物降解1,4-二烷的抑制作用和机理及改进修复技术,最后对今后的研究方向进行了展望。     

Modification of highly brittle polystyrene sulfonic acid-co-maleic acid crosslinked sodium alginate membrane into flexible membranes by the incorporation of dibutyl phthalate as a plasticizer for pervaporation separation

To convert highly brittle into flexible membrane, the polystyrene sulfonic acid-co-maleic acid crosslinked sodium alginate (PSSAMA/NaAlg) membrane was modified by incorporating the different weight% of dibutyl phthalate (DBP) as a plasticizer. The effect of DBP content on the physico-chemical properties of the membranes was thoroughly examined. The membranes exhibited lower glass transition temperatures with increasing the plasticizer content in the matrix of PSSAMA/NaAlg. The separation performance of the membranes for water/isopropanol and water/1,4-dioxane was studied at different temperatures. Among the modified membranes, the membrane containing 6 wt% of DBP exhibited the highest separation factors of 24,129 with a flux of 13.57 × 10⁻² kg/m² hr and 23,353 with a flux of 12.99 × 10⁻² kg/m² hr for water/isopropanol and water/1,4-dioxane at 30°C, respectively. From the temperature-dependent diffusion and permeation values, the Arrhenius activation parameters were estimated. The estimated activation energy values for permeation of water (E_pw) and isopropanol (E_pIPA) were, respectively, ranged between 12.09 and 8.79, and 42.52 and 32.79 kJ/mol. A negative heat of sorption (ΔH_s) values was obtained for all the membranes, suggesting that Langmuir's mode of sorption was predominant. Based on the results, it is concluded that the modified membranes demonstrated excellent pervaporation performance for the separation of water/isopropanol and water/1,4-dioxane.     

Epoxidation of aromatic α,β-unsaturated ketones using PVP–H2O2 under mild and heterogeneous conditions

α,β-Unsaturated ketones (chalcones) react with PVP–H₂O₂ in aqueous sodium hydroxide and 1,4-dioxane as solvent at 40 °C to give the corresponding epoxides under mild and heterogeneous conditions in excellent yields.     

A novel photoelectrocatalytic system for organic contaminant degradation on a TiO2 nanotube (TNT)/Ti electrode

A novel degradation system, combined with photon-efficient thin-film photocatalysis, conventional bulk-phase photocatalysis and photocarrier-efficient electrocatalysis (TBPE), was developed on a vertically ordered one-dimensional (1D) TiO₂ nanotube (TNT)/Ti electrode for the purification of organics. The TBPE system possessed excellent optical, electrochemical, photoelectrochemical and photoelectrocatalytic properties as well as a high mass-transfer coefficient and interfacial activity. The combined degradation of methyl orange (MO) was optimized by varying the rotation angular velocity, applied bias and substrate concentration, and a photoelectrochemical synergetic effect of 62.2% was observed under the optimized conditions for TBPE compared to the individual electrocatalytic (EC) and photocatalytic (PC) systems. To explore the mechanisms, the combined thin-film degradation system of photon-efficient thin-film photocatalysis with photocarrier-efficient electrocatalysis (TPE), and the combined bulk-phase degradation system of conventional bulk-phase photocatalysis with photocarrier-efficient electrocatalysis (BPE), were comparatively estimated. A dramatic increase of 29.4-74.4% was observed in the MO removal efficiency via the thin-film TPE system compared to the bulk-phase BPE system. The results indicated that in the proposed TBPE system on the 1D TNT electrode, the predominant degradation occurred via the TPE system due to its excellent UV utilization efficiency and resultant interfacial photoactivity.