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1.
This paper reports the effects of preillumination, prechlorination and prehydroxylation of TiO2 glass fiber cloth (TiO2-GFC) on the photocatalytic degradation (PCD) reaction of trichloroethylene (TCE) in gas–solid regime. The reaction was monitored in situ by FT-IR spectroscopy at room temperature (298 K). Product analysis by gas chromatography–mass spectrometry (GC–MS) revealed the formation of a new by-product, 1,1-dichloroethane (1,1-DCE) in significant amount along with other known by-products. The photocatalytic activities of TiO2-GFC and the mineralization of TCE were dependent on preillumination, prehydroxylation and prechlorination while the product yield was significantly influenced by prehydroxylation and prechlorination of TiO2-GFC. Prechlorination increased the yields of phosgene (COCl2) and pentachloroethane (C2HCl5) while prehydroxylation decreased the yield of COCl2 with corresponding increases in the yield of oxalyl chloride (COClCOCl) and the mineralization of TCE, suggesting a possible surface-mediated hydrolysis of phosgene to COClCOCl in the latter case. Reaction schemes have been proposed to account for the formation of 1,1-DCE and COClCOCl. The photocatalytic activity of TiO2-GFC and the mineralization of TCE have been found to correlate with the concentration of HCl employed for the prechlorination of TiO2-GFC.  相似文献   

2.
Photocatalytic degradation of trichloroethylene (TCE) was investigated using a tubular photoreactor packed with TiO2 powders prepared by sol–gel techniques. Powders of the following metals: Cr, Fe, Ni, Cu and Pt, or Ca(OH)2 were uniformly mixed with the TiO2 powders and then their effect on the formation of COCl2, CHCl3, and CHCl2COCl as by-products was examined. Concentrations of COCl2 and CHCl3 were determined in a product gas stream by GC/MS while CHCl2COCl accumulated on the catalyst surface. When the catalysts were immersed in water after TCE photodegradation, the formation of Cl- and CHCl2COO ions was confirmed by ion-chromatography. Of the chemicals tested, only Cu and Ca(OH)2 inhibited the formation of the chlorinated by-products. With increasing Cu and Ca(OH)2 content, TCE conversion decreased while the stoichiometric ratio ([CO2]formed/[TCE]degraded) increased. Concentrations of COCl2, CHCl3, and CHCl2COCl decreased with increasing Cu and Ca(OH)2 content. Especially, the formation of COCl2 was remarkably suppressed with Ca(OH)2.  相似文献   

3.
Fine powders of submicron-sized crystallites of BaTiO3 were prepared at 85–130°C by the hydrothermal method, starting from TiO2.ξH2O gel and Ba(OH)2 solution. The products obtained below 110°C incorporated considerable amounts of H2O and OH in the lattice. As-prepared BaTiO3 is cubic and converts to the tetragonal phase after heat treatment at 1200°C, accompanied by the loss of residual OH ions. Hydrothermal reaction of SnO2.ξH2O gel with Ba(OH)2 at 150–260°C gives rise to the hydrated phase, BaSn(OH)6.3H2O, due to the amphoteric nature of SnO2.ξH2O which stabilises Sn(OH)62− anions in basic media. On heating in air or releasing the pressure in situ at 260°C, BaSn(OH)6.3H2O converts to BaSnO3 through an intermediate, BaSnO(OH)4. Solid solutions of Ba(Ti,Sn)O3 are directly formed from (TiO2 + SnO2)..ξH2O gel up to 35 mol% SnO2. At higher Sn contents, the hydrothermal products are mixtures of BaSn(OH)6.3H2O and BaTiO3, which on annealing at 1000°C result in monophasic Ba(Ti,Sn)O3. The sintering characteristics and the dielectric properties of the ceramics prepared out of these fine powders are presented. The dielectric properties of fine-grained Ba(Ti,Sn)O3 ceramics are explained on the basis of the prevailing diffuse phase transition behaviour.  相似文献   

4.
The results of hydrothermal preparation of BaTiO3 fine powders are reported. The effects of the reaction temperature, the molar ratio of Ba/Ti in the precursors, the chemical form of the precursors on the phase composition, the size and the morphology of the products are presented. The higher the temperature, the higher the basicity and the greater the molar ratio of Ba/Ti in the precursor, the easier the formation of the perovskite type BaTiO3 crystallite will be. It was found that BaTiO3 microcrystals(150–300 nm) could be synthesized through the hydrothermal reaction of commercial TiO2 with Ba(OH)2 aqueous solution, while the hydrothermal reaction of the newly prepared Ti(OH)4 gel with the Ba(OH)2 solution produced highly crystallized, well dispersed perovskite type BaTiO3 crystallites with very fine (< 100 nm) particles. The newly prepared Ti(OH)4 gel proved to be suitable precursor for the hydrothermal preparation of BaTiO3 fine powders. X-ray diffraction (XRD) of the hydrothermal BaTiO3 powders reveals a simple cubic perovskite structure. Above that, the lattice constant decreased with the increase of the reaction temperature. These abnormal crystallographic features are assumed to result from lattice defects, due to OH incorporation in the perovskite lattice.  相似文献   

5.
Al2O3陶瓷膜在过滤染料废水过程中容易被染料大分子堵塞,导致Al2O3陶瓷膜水通量下降。以钛酸丁酯、异丙醇铝为前驱体,采用溶胶-凝胶法制备Ti(OH)4-AlOOH复合溶胶,经450 ℃烧成获得TiO2-Al2O3复合粉体。以SEM、纳米粒度/电位仪作为主要表征手段,研究了不同Ti(OH)4和AlOOH摩尔比对复合溶胶粒径分布的影响,进而探究TiO2-Al2O3复合粉体的光催化性能。结果表明,Ti(OH)4和AlOOH摩尔比为0~0.4时,随着Ti(OH)4和AlOOH摩尔比的增大,胶粒的平均粒径从67.5 nm减小到34.0 nm,Ti(OH)4-AlOOH复合溶胶的电位从43 mV升高至53 mV。当Ti(OH)4和AlOOH摩尔比为0.4时,复合粉体对结晶紫的去除率高达79.3%,反应速率常数增大到了0.018 min-1。TiO2-Al2O3复合粉体制备的陶瓷膜能有效降解表面沉积的大分子,解决了陶瓷膜堵塞的问题。  相似文献   

6.
We have investigated the catalytic behavior of Pt encapsulated TiO2 nanotubes for the water gas shift reaction as well as the hydrogenation of CO. Pt–TiO2 nanotube catalysts were prepared by employing fine fiber shaped crystals of [Pt(NH3)4](HCO3)2 complex as a structure determining template material. The turnover frequencies (TOF) of these nanotube catalysts were more than one order of magnitude larger than conventional impregnation Pt/TiO2 catalysts, and the selectivity for methanol in CO–H2 reaction was extraordinary high compared to the impregnation catalysts. The XPS and XRD analyses of the nanotubes revealed characteristic electronic state of reduced TiO2 (Ti3+ in rutile structure) with zerovalent Pt even after the calcination at 773 K. In WGS reaction, electron rich Ti3+ on the nanotube wall may play an important role to activate water molecules for the oxidation of CO. In CO–H2 reaction, similar promotion effect of Ti3+ species may be operating for selective methanol formation by supplying active OH(a).  相似文献   

7.
Heterogeneous photocatalytic degradation of the pesticide Diuron (Nortox, 3-(3,4-dichlorophenyl)-1,1-dimethylurea) was carried under laboratory conditions to evaluate the potential use of this technology for in situ remediation. Soil samples were spiked with three Diuron concentrations (10, 50 and 100 mg kg−1), loaded with catalyst TiO2 and exposed to solar light (22°S and 47°W, with an averaged intensity of 2 mW cm−2 measured at 365 nm). Different catalyst loads (0, 0.1, 0.5, 1 and 2% w/w) were tested in Diuron contaminated soil (100 mg kg−1) for up to 120 h of exposure. Both the catalyst and the Diuron concentration show no influence on the kinetics of the pesticide degradation. The effects of water (10% w/w) and Ca(OH)2 (0.1% w/w) were also evaluated. Water increases the degradation rates, whereas the rise in the pH due to Ca(OH)2 addition shows no measurable effect on the degradation. The photocatalytic treatment using TiO2 combined with solar light is shown to be very efficient in the destruction of Diuron in the top 4 cm of contaminated soil, with the degradation rate markedly dependent on the irradiation intensity.  相似文献   

8.
采用化学还原法制备了RuCu/TiO2双金属催化剂,并探究了Ru和Cu的协同作用对催化湿式氧化(CWAO)无害化处理氨氮废水催化性能的影响。研究结果表明,Cu的添加可有效改善Ru/TiO2催化剂的N2选择性,而Ru的存在可有效提高Cu/TiO2催化剂的催化活性。反应条件为0.5 MPa、150℃、[NH3]0=1000 mg·L-1、pH=12、模拟废水处理量为33 L·(kg cat)-1·h-1时,1Ru2Cu/TiO2能使废水的氨氮转化率和N2选择性分别高达87.7%和85.9%。表征结果表明:Ru和Cu的协同在催化氧化氨氮废水过程中起了关键作用,主要体现在:Ru和Cu的强相互作用导致1Ru2Cu/TiO2催化剂具有良好的抗流失性能,进而使得催化剂具有良好的稳定性;Ru和Cu的电子转移使得1Ru2Cu/TiO2具有适中的亲氧性能,有效提高了催化剂的催化活性。  相似文献   

9.
Poorly crystallized calcium hydroxide [Ca(OH)2] yielded from portland cement pastes incorporated in calcium-polyester complexed polymer concrete (Ca-UP PC) was slowly formed during 21 days' exposure in water at 24°C. Crystal growth continued as the hydration reactions proceeded. Ca(OH)2 formed within the amorphous organic polymer layers after up to 90 days' exposure had little if any effect on the ultimate strength of the PC composites. Ca2+ ions increased with exposure time, and they act as strongly nucleophilic agents to enhance the formation of complexed COO(Ca2+) groups. These contain an ionic bond between Ca2+ ion and carboxylate anion (COO) produced by the hydrolysis of esters in UP polymer.  相似文献   

10.
何川  宋玉宝  马云龙  王乐乐  卞子君 《化工进展》2020,39(11):4619-4624
在实验室中试台架上,开展了Ca(OH)2、CaO、Mg(OH)2和MgO四种碱基吸附剂粉体喷射脱除烟气SO3的实验,研究了碱基吸附剂脱除烟气SO3的影响因素,探究了碱基吸附剂脱除SO3技术对选择性催化还原(SCR)催化剂硫酸氢铵失活温度的影响。采用比表面积法(BET)、傅里叶红外光谱(FTIR)等手段对吸附剂进行表征,以判断吸附产物和吸附机理。结果显示:碱基氢氧化物吸附剂的SO3脱除效果优于碱基氧化物吸附剂;Mg基吸附剂优于Ca基吸附剂;当烟气中SO3浓度为35μL/L时,Mg(OH)2含量为600mg/m3时具有最高的SO3脱除效率,达到95%左右。对低温失活后的SCR催化剂进行FTIR表征证实了催化剂表面硫酸氢铵的生成。此外,通过碱基吸附剂降低烟气中SO3浓度后,SCR催化剂在低温时的失活得到了显著缓解,可明显降低SCR催化剂的硫酸氢铵失活温度约20℃,有助于挖掘机组调峰深度。  相似文献   

11.
本文提出了一类改性碱激发矿渣胶凝材料,通过在原材料中掺入额外的钙、铝质矿相(Ca(OH)2和γ-Al2O3),促进材料基体中的Friedel's盐(F盐)在氯离子存在条件下的形成,进而提升胶凝材料的氯离子固化能力。本研究探讨了钙、铝质矿物含量对碱矿渣反应产物组成、氯离子固化量以及力学性能的影响。结果表明,钙、铝质矿相的额外补充可显著提高胶凝材料的氯离子固化能力,同时体系的m(Ca)/m(Al)与该能力的相关性较高。物相分析结果表明,钙质矿相的补充使得反应产物中拥有富余的Ca(OH)2,在氯盐侵蚀作用下,富余的Ca(OH)2全部转化为F盐或其他物相,证实了体系氯离子固化能力的增强得益于F盐的形成,即得益于化学固氯能力的提升。抗压强度测试结果,表明钙质矿物的掺入对力学性能存在一定负面影响,而铝质矿相的掺入则能够在一定程度上弥补强度损失。  相似文献   

12.
An environmentally friendly solid acid catalyst, Ce(SO4)2/TiO2 was prepared simply by modifying TiO2 with Ce(SO4)2 for acid catalysis of volatile organic chemicals, 2-propanol and cumene. The characterization of prepared catalysts was performed using FTIR, XRD and DSC. The surface area of 7-Ce(SO4)2/TiO2 calcined at 300 °C was very high (206.0 m2/g) compared to that of unmodified TiO2 (115.2 m2/g) due to the interaction between Ce(SO4)2 and TiO2. 7-Ce(SO4)2/TiO2 containing 7 wt% Ce(SO4)2 and calcined at 300 °C exhibited maximum catalytic activities for both reactions, 2-propanol dehydration and cumene dealkylation. The catalytic activities for both reactions were correlated with the acid amounts of catalysts measured by an ammonia chemisorption method. The role of Ce results in an increase in the thermal stability of the surface sulfate species and consequently the acid amount of Ce(SO4)2/TiO2 is increased. The asymmetric stretching frequency of the SO bonds for Ce(SO4)2/TiO2 catalysts was related to the acidic properties and to the catalytic activity for acid catalysis to remove volatile organic chemicals, 2-propanol and cumene.  相似文献   

13.
Photodegradation catalyst screening by combinatorial methodology   总被引:1,自引:0,他引:1  
In this work, a combinatorial methodology was developed for photodegradation catalyst screening. A fluorescence imaging detection system was designed for high throughput analysis, 1,6-hexamethylenediamine was used as the probe molecule for catalyst testing. The photodegradation activity of catalysts was evaluated by 1,6-hexamethylenediamine consumption during the photodegradation reaction. The methodology could provide reliable results. We found that pure TiO2, ZrO2, Nb2O5, MoO3, and WO3 did not show much activity for 1,6-hexamethylenediamine photodegradation under visible light. TiO2 catalysts doped with different metal ions were tested. When TiO2 was doped with Ta2O5, Nb2O5, V2O5, MoO3, or WO3, higher activity for photodegradation was observed. The doping of La3+, Ba2+, and Br to TiO2 did not improve the catalytic activities. When doping TiO2 with Mn2+, Cl, Al3+, Cu2+, Fe3+, Na+, Mg2+, Li+, F, Co2+, or K+, catalytic activity was lower than that of pure TiO2. After elaborate catalysts screening, we discovered new catalysts, such as 50–70% TiO2/0–20% WO3/20–40% VO2.5 and 20–30% TiO2/30–50% MoO3/40–60% VO2.5 as well as 30% WO3/20% ZrO2/50% NbO2.5 (synthesized from ZrCl4, NbCl5, and (NH4)5H5[H2(WO4)6]·H2O in ethanol solution or suspension) and 60–70% WO3/Nb2O5 (synthesized from WCl6 and NbCl5 in ethanol solution). We observed that the catalytic activity is sensitive to preparation methods and catalyst specific surface areas. When P123 (HO(CH2CH2O)20(CH2CH(CH3)O)70(CH2CH2O)20H, designated EO20PO70EO20) was used as template to synthesize mesoporous materials, the mesoporous catalysts showed higher activity than regular catalytic materials.  相似文献   

14.
李静  张启俭  齐平  韩丽  邵超 《工业催化》2017,25(6):19-23
二甲醚是一种理想的氢载体,可用于解决氢的储存和运输。以Pt/TiO_2为部分氧化催化剂,结合Ni/Al_2O_3重整催化剂,考察钛前驱体和焙烧温度对二甲醚部分氧化重整制氢反应的影响。结果表明,以Ti(C4H9O)4为原料制备的TiO_2为金红石相,Ti(SO4)2或Ti O(OH)2为原料制备的TiO_2为锐钛矿相;以Ti(C4H9O)4为原料制备的Pt/TiO_2-E催化剂催化性能略好,转化率接近100%,H2收率约90%,表明金红石相TiO_2负载的Pt催化剂略佳;以Ti(SO4)2为原料制备的Pt/TiO_2-S催化剂500℃焙烧可获得金红石相TiO_2。与Pt/Al_2O_3催化剂相比,Pt/TiO_2催化剂具有更好的催化性能,H2收率超过90%,而Pt/Al_2O_3催化剂H2收率约80%。  相似文献   

15.
Cellulose, one of the important components of biomass, was gasified in supercritical water to produce hydrogen-rich gas in an autoclave which was operated batch-wise under high-pressure. K2CO3 and Ca(OH)2 were selected as the catalysts (or promoters). The temperature was kept between 450°C and 500°C while pressure was maintained at 24–26 MPa. The reaction time was 20 min. Experimental results showed that the two catalysts had good catalytic effect and optimum amounts were observed for each catalyst. When 0.2 g K2CO3 was added, the hydrogen yield could reach 9.456 molkg-1 which was two times of the H2 amount produced without catalyst. When 1.6 g Ca(OH)2 was added, the H2 yield was 8.265 molkg-1 which is lower than that obtained using K2CO3 as catalyst but is still 1.7 times that achieved without catalyst. Comparing with the results obtained using K2CO3 or Ca(OH)2 alone, the use of a combination of K2CO3 and Ca(OH)2 could increase the H2 yield by up to 2.5 times that without catalyst and 25% and 45% more than that obtained using K2CO3 and Ca(OH)2 alone, respectively. It was found that methane was the dominant product at relatively low temperature. When the temperature was increased, the methane reacts with water and is converted to hydrogen and carbon dioxide.  相似文献   

16.
The degradation of herbicide monuron (initial concentration 5×10−5 M) in plate photoreactor with laminar flow of the solution using heterogeneous (TiO2) and/or homogeneous photocatalyst (Fe(ClO4)3) was investigated. For the rate of photoinduced degradation with Fe(III) aquacomplexes, the initial concentration of monomer Fe(OH)2+, which is the most photocatalytically active form of Fe(III), is crucial. The degradation rate for combination of both photocatalysts is higher than the sum of the rates for separately taken single catalysts. This is caused not only by the addition of the two effects but also by the fact that Fe(III) acts as scavanger of electrons photogenerated in TiO2 particles thus let down hole–electron recombination. Fe(OH)2+ appears to be the most photoactive trap for electrons.  相似文献   

17.
赵清华  全学军  程治良  晏云鹏 《化工学报》2013,64(11):3993-4000
在一种新型高效的气液传质设备--水力喷射-空气旋流器(WSA)中,以Ca(OH)2料浆为吸收剂进行了模拟烟气湿法脱硫的实验研究。结果表明:脱硫率随进口气速增加而增加;随液体喷射速度增加先增加,增加到一定程度后几乎不变;随烟气中SO2的进口浓度增加而减小,存在一适宜的Ca(OH)2浓度和回流比。在气体流量24~72 m3·h-1、循环液体量0.4~0.8 m3·h-1、料浆中Ca(OH)2浓度7500 g·m-3时,对SO2浓度为1891~6373 mg·m-3的烟气进行湿法脱硫,脱硫率达88.9%~97.7%,且WSA的旋流气体和喷射液体在湿法脱硫中具有自清洁能力,未发现内部结垢和喷孔堵塞现象。总体积传质系数KGa、有效相界面积a均随进口气速uG增大而增大,而总传质系数KG随uG增加变化较小;当液体喷射速度 uL≤0.26 m·s-1时,KGa和KG随uL增加快速增大,之后增加缓慢,而a随uL几乎线性增加,KGa和KG随吸收剂中Ca(OH)2浓度cL增加有一最大值。结合实验数据拟合得到了相关的经验公式,这些关联式能较好地预测WSA的湿法脱硫传质性能。气体旋流场强度对总体积传质系数KGa和有效相界面积a起支配作用,脱硫传质过程同时受气膜和液膜阻力控制,但以液膜控制为主。  相似文献   

18.
Gold loaded on TiO2 (Au/TiO2) catalysts were prepared using Au(I)–thiosulfate complex (Au(S2O3)23−) as the gold precursor for the first time. The samples were characterized by UV–vis diffuse reflectance spectra, X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic absorption flame emission spectroscopy (AAS), and X-ray photoelectron spectroscopy (XPS) methods. Using Au(S2O3)23− as gold precursor, ultra-fine gold nanoparticles with a highly disperse state can be successfully formed on the surface of TiO2. The diameter of Au nanoparticles increases from 1.8 to 3.0 nm with increasing the nominal Au loading from 1% to 8%. The photocatalytic activity of Au/TiO2 catalysts was evaluated from the analysis of the photodegradation of methyl orange (MO). With the similar Au loading, the catalysts prepared with Au(S2O3)23− precursor exhibit higher photocatalytic activity for methyl orange degradation when compared with the Au/TiO2 catalysts prepared with the methods of deposition–precipitation (DP) and impregnation (IMP). The preparation method has decisive influences on the morphology, size and number of Au nanoparticles loaded on the surface of TiO2 and further affects the photocatalytic activity of the obtained catalysts.  相似文献   

19.
The relationships between morphology and Lewis acid and base character of surface sites of two types of titania powders (TiO2 P25 and TiO2 Merck) were studied by HRTEM and FTIR spectroscopy of adsorbed molecules. Electron micrographs revealed that TiO2 P25 microcrystals have a prismatic shape, mainly exposing (0 0 1) and (0 1 0) surface planes. TiO2 Merck powder, which exhibits a significantly lower specific surface area, appeared constituted by large roundish microcrystals. FTIR spectra of adsorbed CO indicated that Ti4+ ions exposed on (0 0 1) and (0 1 0) faces of TiO2 P25 particles are Lewis acid centres significantly stronger than those present on the surface of TiO2 Merck microcrystals. As in both cases the exposed cations are coordinated to five oxygen anions, the observed differences in Lewis acidity are ascribed to some difference in the geometric arrangement of the O2− ligands. Such difference in structure affects the basicity of these centres also. In fact, a fraction of O2− ions on the surface of TiO2 P25 behave as basic centres toward CO2 linearly adsorbed on neighbour Ti4+ centres, and then Lewis acid–base pairs can be recognised. By contrast, no basic activity towards CO2 was detected for the TiO2 Merck sample.

The two titania powders exhibited different chemical behaviour in condition of high surface hydration also. Hydroxyl groups on the surface of hydrated TiO2 P25 are able to transform benzaldehyde molecules in hemiacetalic-like species, whereas C6H5CHO molecules are only weakly perturbed by interaction with the OH groups on TiO2 Merck particles. This feature could be related to the different photocatalytic behaviour in the oxidation of toluene in gas phase, where benzaldehyde was found as a relevant intermediate species.  相似文献   


20.
污水厂污泥量日益增加,所含的有机物可用于厌氧发酵产甲烷,但目前多数污水处理厂多为低有机质污泥。本文围绕低有机质污泥投加不同药剂联合低温热水解对污泥溶解性物质变化及厌氧发酵规律的影响情况进行研究。结果表明,投加药剂联合低温热水解不仅有助于有机物[可溶糖、可溶蛋白和TVFA(挥发性有机酸(]的溶出与生成,而且有助于后续厌氧发酵产甲烷。在本实验所研究的低温热水解(污泥含固率为8%,热水解处理温度为90℃,处理时间为24 h)及药剂投加量[NaOH:0.018 g·(g DS(-1、Ca(OH(2:0.016 g·(g DS(-1、CaCl2:0.0375g·(g DS(-1]的条件下,有机物溶出与生成的效果为NaOH> Ca(OH(2> CaCl2,其中热水解联合NaOH中可溶糖、可溶蛋白和TVFA浓度分别达到3051 mg·L-1、10686 mg·L-1和5740 mg·L-1。对于产甲烷促进效果为NaOH> CaCl2> Ca(OH(2,其中投加NaOH后最大累积产甲烷量可达到101.9 ml·(g VS(-1。  相似文献   

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