Cu/SSZ-13催化剂脱硝活性中心与催化性能构效关系的研究

NH₃选择性催化还原NO_x（NH₃-SCR）是目前最有应用前景的柴油车尾气净化技术,该技术的核心是开发具备优异催化性能的催化剂。以具有菱沸石（chabazite,CHA）结构的小孔分子筛SSZ-13为载体制备的Cu/SSZ-13催化剂,因具有优异的催化性能和水热稳定性能而受到广泛关注。制备了系列Cu_x/SSZ-13催化剂,并通过CO原位漫反射红外光谱（DRIFT）和H₂-TPR等方法能够确定具有高催化活性的铜离子在SSZ-13分子筛上的落位和存在状态。CO红外吸附实验发现,采用Cu(NO₃)₂水溶液离子交换法制备的Cu/SSZ-13催化剂上存在多种落位的Cu⁺活性中心。在较低的Cu⁺交换度条件下,Cu⁺优先落位于SSZ-13分子筛的八元环位置,随着交换度的提高,Cu⁺开始落位于SSZ-13分子筛双六元环的位置。H₂-TPR结果表明Cu_x/SSZ-13催化剂上也存在大量落位在八元环位置不稳定的Cu²⁺,这些Cu²⁺很容易被还原为Cu⁺。Cu_x/SSZ-13催化剂经800℃水蒸气连续老化16 h,分子筛骨架崩塌程度随着Cu含量的增加而提高,骨架铝的脱除,导致Cu物种发生团聚,而第二金属Ce元素的引入能够在一定程度上提高Cu/SSZ-13的水热稳定性。催化剂构效关系研究表明,具有一定量稳定存在的Cu⁺,并且拥有大量不稳定存在Cu²⁺的催化剂具有较宽温度范围的脱硝性能。     

胶原多肽基表面活性剂对废水中Cu(Ⅱ)的沉淀浮选性能

以低浓度Cu²⁺水溶液模拟重金属离子废水,研究了胶原多肽基表面活性剂（阴离子型CBS和阳离子型C-CBS）对重金属离子废水的沉淀浮选性能。通过单因素实验考察了pH、气速、表面活性剂质量浓度、气浮时间、Cu²⁺初始浓度等因素对废水中Cu²⁺沉淀浮选效果的影响。结果表明,CBS和C-CBS均适用于在碱性条件下对金属离子废水进行沉淀浮选,Cu²⁺的去除率达到90%左右;且随着气速的升高,Cu²⁺的去除率增加而后趋于不变;随着表面活性剂用量的增加,对CBS,Cu²⁺的去除率增加,而对C-CBS,Cu²⁺的去除率反而下降;随气浮时间延长,Cu²⁺去除率逐渐增加而后趋于不变。研究表明,胶原多肽基表面活性剂可用于重金属离子废水的沉淀浮选。     

CuO改性商用选择性催化还原催化剂催化氧化单质汞性能

燃煤烟气中单质汞（Hg⁰）的高效氧化是提高燃煤电厂脱汞效率的关键,为提高传统选择性催化还原（SCR）催化剂氧化Hg⁰的性能,本文采用溶液浸渍法制备了CuO-SCR催化剂,在固定床反应装置上考察了其脱硝协同氧化单质汞性能,并借助BET、XRD和XPS等分析技术对催化剂进行表征。结果表明,CuO的掺杂显著提高了商用SCR催化剂的Hg⁰氧化性能和低温脱硝活性;在200~400℃内,随着反应温度升高和NO+NH₃浓度增大,NH₃对CuO-SCR催化剂的Hg⁰氧化性能抑制作用加强;在350℃、模拟燃煤烟气条件下,随着空速比的减小,催化剂的Hg⁰氧化性能显著提高,NH₃对Hg⁰氧化的抑制作用明显减弱。催化剂表征结果表明,CuO-SCR催化剂表面存在氧化还原反应V⁴⁺+Cu²⁺?V⁵⁺+Cu⁺,增强了催化剂的催化活性。Hg⁰在CuO-SCR催化剂表面的氧化过程遵循Mars-Maessen机制,能够有效增强催化剂的Hg⁰氧化性能。     

Na盐修饰的Cu/SiO2催化丙烯环氧化反应研究

通过浸渍法制备了6种Na盐修饰的Cu/SiO₂催化剂,利用XRD、TEM和XPS对其晶相结构、粒径大小和Cu物种价态进行了分析,考察了Na盐促进剂种类和摩尔分数对Cu/SiO₂催化剂上丙烯氧气环氧化反应性能的影响。结果表明,6种Na盐可以不同程度地还原Cu²⁺物种,生成不同含量的Cu⁰或Cu⁺物种。6种Na盐都可以提高Cu/SiO₂的丙烯环氧化活性,而且Na₂CO₃最有利于环氧丙烷的生成。适量的Na₂CO₃可以促进Cu⁺物种的形成,有利于丙烯环氧化反应的进行,但过量的Na₂CO₃会导致Cu⁰物种的产生以及Cu物种的聚集,反而不利于环氧丙烷的生成。Cu⁺物种摩尔分数越高,Cu/SiO₂的丙烯环氧化活性和环氧丙烷的形成速率也越大。小粒径的Cu<...     

Cu/Co掺杂多孔炭活化过硫酸盐降解水中硝基酚研究

以MOF-74为模板制备了Cu/Co双金属掺杂多孔炭催化剂。用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、N₂物理吸附/脱附等对催化剂结构进行了表征。研究并阐释了Cu/Co双金属掺杂多孔炭催化剂活化过一硫酸盐(PMS)氧化降解4-硝基酚性能及机理。结果表明，在投加100 mg·L^-1催化剂、2 g·L^-1 PMS、初始pH为6时，15 min内硝基酚(60 mg·L^-1)去除率达98%以上。降解反应符合伪一级反应动力学模型。催化剂循环反应4次，降解率均高于90%。猝灭实验及电子顺磁共振分析表明自由基(·SO₄^-、·OH、·O₂^-)和非自由基(¹O₂)均参与了降解反应。在反应过程中，Co²⁺/Co³⁺和Cu+/Cu²⁺的氧化还原循环有效活化了PMS并促进活性氧化物种的生成，从而提升了催化剂...     

生物炭基催化剂制备对其催化降解Ni-EDTA性能影响

以胶原蛋白、木质素和硝酸铜为原料,采用共混热解法制备新型生物炭基铜系催化剂,通过多种表征手段考察制备方法和参数对催化湿式过氧化氢氧化（CWPO）处理Ni-EDTA模拟废液效果的影响,并阐述氧化降解过程中生物炭基铜系催化剂的失活机制。结果表明,相比溶液浸渍法,共混热解法有利于提高催化剂的催化活性,控制活性组分的均质分布和溶出释放,表现为Ni和TOC去除率分别增加13.05%和16.63%,Cu²⁺溶出量降低93.54%;在焙烧温度为800℃,Cu掺量为10%,胶原蛋白与木质素质量比例为1：3条件下,1000 mg·L^-1 Ni-EDTA模拟废液经60 min催化氧化后Ni和TOC去除率分别达到65.41%和34.85%,Cu²⁺溶出量仅为1.7 mg·L^-1。氧化降解过程中羧酸类中间降解产物的形成、活性组分反应性溶出和价态转变是致使催化剂失活的主要原因。     

生物炭/过一硫酸盐体系同时去除Cu2+和对硝基苯胺

目前，重金属离子和有机污染物共存的废水处理是一个世界性的重大问题，对环境保护具有重要的意义。本研究以农业废弃物向日葵秸秆为原料，制备了一种生物炭（BC），用以活化过一硫酸盐（PMS）。BC/PMS体系实现了对水中重金属Cu²⁺和有机污染物对硝基苯胺（PNA）的同时去除。探究了pH、BC投加量和PMS浓度等反应条件对同时去除Cu²⁺和PNA的影响。研究表明，在BC=2.0g/L、PMS=1.0mmol/L、PNA=20.0mg/L、Cu²⁺=2.0mg/L和pH=3.0条件下，60min时Cu²⁺和PNA同时去除效率分别为90.00%和100.00%；Cu²⁺被BC/PMS体系吸附去除的同时也显著地促进了PNA的降解去除。自由基猝灭实验和电子顺磁共振光谱（EPR）实验表明，BC/PMS/Cu²⁺/PNA体系降解PNA为自由基反应和非自由基反应共存过程，且以非自由基反应为主导；自由基反应是基于Cu²⁺活化PMS产生SO{}_{\mathrm{4}}^{·-}和?OH，非自由基反应可归因于BC活化PMS产生活性物种¹O₂。     

CuCe氧化物催化剂的制备及CWPO降解双酚A废水研究

为解决Fenton法存在活性组分流失及通常在pH 2～3条件下运行的局限性，采用柠檬酸络合法制备了CuCe氧化物催化剂，建立了双酚A非均相催化湿式过氧化氢氧化（CWPO）反应体系。考察了焙烧温度、Cu/Ce摩尔比、H₂O₂用量、双酚A初始浓度和pH对催化剂物化结构和CWPO性能的影响。并分析了可能的降解路径。结果表明：催化剂具有良好的高温稳定性和pH适应性，在pH 1.6～7.9范围内对双酚A都具有较高的降解性能，不需要调节pH。在焙烧温度450℃、Cu/Ce摩尔比1.0、催化剂用量1 g·L^-1、H₂O₂用量196 mmol·L^-1、BPA浓度152 mg·L^-1、pH 6.6、反应温度75℃、反应95 min后，BPA和TOC去除率分别为91.8%和84.5%,Cu²⁺析出浓度为19.3 mg·L^-1。推测了双酚A可能的降解路径。     

Cu2+对生物膜及其胞外聚合物的影响

利用自行设计的生物膜培养装置进行挂膜,通过向生物膜反应器中投加不同浓度的Cu²⁺,探讨生物膜上的胞外聚合物（extracellular polymeric substance, EPS）与生物膜去除金属铜之间的关系。研究结果表明：生物膜法较活性污泥法对Cu²⁺具有更好的耐受性;当Cu²⁺ < 2 mg·L^-1,Cu²⁺会抑制生物膜分泌EPS,在2 mg·L^-1 < Cu²⁺ < 5 mg·L^-1时,生物膜分泌EPS的量增加,当Cu²⁺ > 5 mg·L^-1,生物膜系统表现为严重的不稳定性;比较蛋白质（proteins,PN）/多糖（polysaccharide,PS）值发现,Cu²⁺对生物膜的抑制主要是对生物膜上胞外多糖的抑制,而生物膜对Cu²⁺的抵抗表现为分泌更多的胞外蛋白;EPS与Cu²⁺的富集率关系呈线性正相关。     

均三嗪衍生物比色识别Cu2+及荧光识别Zn2+

以对氨基苯腈、邻叔丁基苯酚和3,5-二叔丁基水杨醛为原料合成了两种含有均三嗪对称结构的离子探针1和2，通过核磁共振氢谱、核磁共振碳谱、红外、质谱对合成产物进行表征，确认其结构。利用紫外吸收光谱和荧光光谱两种手段分别考察了探针1和探针2在N,N-二甲基甲酰胺（DMF）溶液中对金属离子（Cr³⁺、Mn²⁺、Fe³⁺、Co²⁺、Ni²⁺、Cu²⁺、Zn²⁺、Cd²⁺、Hg²⁺）的识别性能，通过核磁共振氢谱对探针1与Zn²⁺的识别机理进行研究。结果表明，两种探针热稳定性强，探针1溶液中加入Zn²⁺会引起荧光强度的显著增强，抗干扰性强，是一种高选择性识别Zn²⁺的荧光增强型探针；探针2中加入Cu²⁺后溶液由无色变成黄色，紫外光谱长波长处出现新吸收峰，是一种可裸眼识别的、高效的紫外Cu²⁺探针。     

Active sites of Cu-ZSM-5 for the decomposition of acrylonitrile

The catalytic decomposition of acrylonitrile (AN) over Cu-ZSM-5 prepared with various Cu loadings was investigated. AN conversion, during which the nitrogen atoms in AN were mainly converted to N₂, increased as Cu loading increased. N₂ selectivities as high as 90–95% were attained. X-ray diffraction measurements (XRD) and temperature-programmed reduction by H₂ (H₂-TPR) showed the existence of bulk CuO in Cu-ZSM-5 with a Cu loading of 6.4 wt% and the existence of highly dispersed CuO in Cu-ZSM-5 with a Cu loading of 3.3 wt%. Electron spin resonance measurements revealed that Cu-ZSM-5 contains three forms of isolated Cu²⁺ ions (square-planar, square-pyramidal, and distorted square-pyramidal). The H₂-TPR results suggested that in Cu-ZSM-5 with a Cu loading of 2.9 wt% and below, Cu⁺ existed even after oxidizing pretreatment. The activity of AN decomposition over Cu/SiO₂ suggested that CuO could form N₂, but, independent of the CuO dispersion, nitrogen oxides (NO_x) were formed above 350 °C. Cu⁺ and the square-pyramidal and distorted square-pyramidal forms of Cu²⁺ showed low activity for AN decomposition. Temperature-programmed desorption of NH₃ suggested that N₂ formation from NH₃ proceeded on Cu²⁺, resulting in the formation of Cu⁺. The Cu⁺ ions were oxidized to Cu²⁺ at around 300 °C. Thus, high N₂ selectivity over Cu-ZSM-5 with a wide range of temperature was probably attained by the reaction over the square-planar Cu²⁺, which can be reversibly reduced and oxidized.     

Insight into the promotional mechanism of Cu modification towards wide-temperature NH3-SCR performance of NbCe catalyst

A simple strategy of Cu modification was proposed to broaden the operation temperature window for NbCe catalyst. The best catalyst Cu_0.010/Nb₁Ce₃ presented over 90% NO conversion in a wide temperature range of 200-400 ℃ and exhibited an excellent H₂O or/and SO₂ resistance at 275 ℃. To understand the promotional mechanism of Cu modification, the correlation among the “activity-structure-property” were tried to establish systematically. Cu species highly dispersed on NbCe catalyst to serve as the active component. The strong interaction among Cu, Nb and Ce promoted the emergence of NbO₄ and induced more Brønsted acid sites. And Cu modification obviously enhanced the redox behavior of the NbCe catalyst. Besides, EPR probed the Cu species exited in the form of monomeric and dimeric Cu²⁺, the isolated Cu²⁺ acted as catalytic active sites to promote the reaction: Cu²⁺-NO₃^-+NO(g) → Cu²⁺-NO₂^-+NO₂(g). Then the generated NO₂ would accelerate the fast-SCR reaction process and thus facilitated the low-temperature deNO efficiency. Moreover, surface nitrates became unstable and easy to decompose after Cu modification, thus providing additional adsorption and activation sites for NH₃, and ensuring the improvement of catalytic activity at high temperature. Since the NH₃-SCR reaction followed by E-R reaction pathway efficaciously over Cu_0.010/Nb₁Ce₃ catalyst, the excellent H₂O and SO₂ resistance was as expected.     

Cr2O3 promoted skeletal Cu catalysts for the reactions of methanol steam reforming and water gas shift

Promotional effects of chromia on the structure and activity of skeletal copper catalysts for methanol steam reforming and water gas shift have been studied. Catalysts were prepared by leaching CuAl₂ alloy particles in aqueous NaOH solutions containing sodium chromate at various concentrations. XPS spectra showed that the surface of the resulting catalysts mainly consisted of Cr³⁺ compounds and Cu⁰. Cu⁺ and/or Cu²⁺ were not observed by XPS.

Increasing the concentration of chromate in the leach liquor resulted in decreases in pore diameter and copper crystallite size but significant enhancement of BET surface area was observed while the total pore volume was maintained. The addition of small amounts of chromate to the leach liquor significantly enhanced the Cu surface area. However, higher concentrations of chromate in the leach liquor decreased the Cu surface areas although the total surface areas increased.

The activities of Cr₂O₃ promoted skeletal copper catalysts for both methanol steam reforming and water gas shift reactions were determined separately. The results indicated that deposition of Cr₂O₃ on skeletal copper catalysts significantly improved the specific activities for these reactions. Chromia is found to act as a structural and catalytic promoter for these reactions.     

Identification of copper(II) and copper(I) and their interconversion in Cu/ZSM-5 De-NOx catalysts

A combined Fourier transform IR (FT-IR) and electron paramagnetic resonance (EPR) study shows that copper in ‘excessively exchanged’ Cu/ZSM-5 is initially present as OH bridged Cu²⁺ dimers, besides isolated Cu²⁺ ions. Upon heating, the dimers lose water and become oxygen bridged [Cu---O---Cu]²⁺ complexes. These are ‘EPR-silent’, presumably as a consequence of antiferromagnetic coupling of the unpaired electrons in each Cu²⁺; they are, however, detectable by their perturbation of the lattice vibrations, detected by a FT-IR band at 918–923 cm⁻¹. Reduction by hydrogen or carbon monoxide converts the [Cu---O---Cu]²⁺ complexes to pairs of Cu⁺ ions, while the color changes from green to grey. Reductive adsorption of nitrogen monoxide on Cu²⁺ results in the formation of Cu⁺---NO⁺. Destructive thermal desorption of nitrogen monoxide at 100°C not only restores the Cu²⁺ ions, but also appears to regenerate the [Cu---O---Cu]²⁺ complex. The results suggest that pairs of copper ions are instrumental in the catalytic decomposition of nitrogen monoxide.     

焙烧温度对MgO修饰Cu/ZnO催化剂结构及催化草酸二甲酯加氢反应研究

采用共沉淀法制备了系列掺杂Mg2+离子的Cu-Mg/ZnO[n(Cu)∶n(Zn)=5∶4]催化剂,并用N2吸附-脱附、XRD和H2-TPR等对催化剂进行表征,考察焙烧温度对催化剂结构及其催化草酸二甲酯加氢反应性能的影响。结果表明,经350℃焙烧所得Cu-Mg/ZnO-c350催化剂具有较大的比表面积,发达的介孔结构,较高的Cu物种分散性和较多的表面Cu0活性位;而较高的焙烧温度导致催化剂中纳米粒子聚集烧结,降低催化剂比表面积、孔径尺度和表面Cu0活性物种数量。适宜反应条件,Cu-Mg/ZnO-c350催化剂催化草酸二甲酯气相加氢反应转化率为100%,乙二醇收率为95%。此外,较强的金属-载体作用力抑制铜活性物种的抗烧结能力,赋予其优异的稳定性。     

Selective catalytic reduction of nitric oxide by ethylene in the presence of oxygen over Cu ion-exchanged pillared clays

Cu²⁺ ion-exchanged pillared clays are substantially more active than Cu²⁺-ZSM-5 for selective catalytic reduction (SCR) of NO by hydrocarbons. More importantly, H₂O (or SO₂) has only mild effects on their activities. First results on Cu²⁺-exchanged TiO₂-pillared montmorillonite were reported by this laboratory (Yang and Li, Ref. [1]), that showed overall activities two to four times higher than Cu²⁺-ZSM-5.

A delaminated pillared clay was subjected to Cu²⁺ ion-exchange and studied for SCR by C₂H₄ in this work. The Cu²⁺ ion-exchanged delaminated Al₂O₃-pillared clay yielded substantially higher SCR rates than both Cu²⁺-exchanged TiO₂-pillared clay and Cu²⁺-ZSM-5 at temperatures above 400°C. The peak NO conversion was 90% at 550°C and at a space velocity of 15,000 h⁻¹ (with O₂ = 2%). The peak temperature decreased as the concentration of O₂ was increased. The macroporosity in the delaminated pillared clay was partially responsible for its higher peak temperatures (than that for laminated pillared clays). At 1000 ppm each for NO and C₂H₄, the NO conversion peaked at 2% O₂ for all temperatures. H₂O and SO₂ caused only mild deactivation, likely due to competitive adsorption (of SO₂ on Cu²⁺ sites and H₂O on acid sites). The high activity of Cu²⁺-exchanged Al₂O₃-pillared clay was due to a unique combination of the redox property of the Cu²⁺ sites and the strong Lewis acidity of the pillared clay. The suggested mechanism involved NO chemisorption (in the presence of O₂) on Cu²⁺OAl³⁺-on the pillars, and C₂H₄ activation on the Lewis acid sites to form an oxygenated species.     

ZSM-5分子筛负载金属氧化物催化剂催化燃烧含丙烯腈废气的性能

采用等体积浸渍法将过渡金属Cu负载到ZSM-5分子筛上,并与其他金属(Fe、Co、Ag、Pd、Ce)共浸渍得到负载型催化剂,将其用于全组分丙烯腈废气的催化脱除过程。催化活性评价结果表明,丙烯腈在Cu/ZSM-5催化剂上320℃可以实现完全转化;掺杂质量分数2%Ce后,丙烯腈的完全转化温度降低到300℃,高选择生成N2的温度窗口也变宽,催化剂稳定性高。通过X射线衍射、氮气吸附-脱附、氢气-程序升温还原、氨气-程序升温脱附和X射线光电子能谱等对催化剂的物化性能进行表征,结果表明,催化剂催化氧化丙烯腈尾气的性能依赖于Cu^2+的还原能力、催化剂表面弱酸与中强酸含量以及表面Cu^2+丰度。     

Studies of Cu-ZSM-5 by X-ray absorption spectroscopy and its application for the oxidation of benzene to phenol by air

The oxidation of benzene to phenol has been successfully carried out in air over Cu-ZSM-5 at moderate temperatures. Several parameters such as Cu loading, calcination temperature and co-exchanged metal ions influence the nature of the catalyst. At low Cu loadings, the catalyst is more selective to phenol while at high Cu loadings CO₂ is the major product. In situ H₂-TPR XAFS studies reveal that at low Cu loadings, Cu exists as isolated pentacoordinated ions, with 4 equatorial oxygens at 1.94 Å and a more distant axial oxygen at 2.34 Å. At higher loadings, monomeric as well as dimeric Cu species exist, with a Cu–Cu distance of 2.92 Å. This suggests that the isolated Cu sites are the active sites responsible for phenol formation. When the catalyst was calcined at 450 °C, the activity peaked in the first hour and then slowly deactivated, but when the calcination temperature was increased to 850 °C, the activity slowly increased until it reached a plateau. Analysis of the XANES region during in situ H₂-TPR shows that at lower calcination temperatures two reduction peaks are present, corresponding to Cu²⁺ → Cu⁺ and Cu⁺ → Cu⁰. At high calcination temperatures, only a small fraction of the Cu undergoes the two-step reduction and most of the Cu remains in the +2 state. Slow deactivation of the catalyst calcined at 450 °C is due to migration of the Cu ions to inaccessible sites in the zeolite; at high calcination temperatures the Cu is tightly bound to the framework and is unable to migrate. EXAFS analysis of the sample calcined at 850 °C reveals two Cu–Si(Al) scattering paths at 2.83 Å. Doping the catalyst with other metals, in particular Ag and Pd, further improves the activity and selectivity of the reaction. The addition of water to the reaction increases the selectivity of the reaction by displacing the product from the active site.     

Silver modified Cu/SiO2 catalyst for the hydrogenation of methyl acetate to ethanol

A series of silver modified Cu/SiO_2 catalysts were synthesized with ammonia-evaporation method and applied in vapor-phase hydrogenation of methyl acetate to ethanol. The influence of additive ‘Ag' on the structural evolution of catalyst was systematically studied by several characterization techniques, such as N_2 adsorption–desorption, N_2O titration, PXRD, FTIR, in-situ FTIR, H_2-TPR, H_2-TPD, XPS and TEM. Results showed that incorporation of a small amount of Ag could enhance the structural stability, and the strong interaction between Cu and Ag species was conducive to increase the dispersion of copper species and create a suitable Cu~(+)/(Cu~0+ Cu~(+)) ratio, which was proposed to be responsible for the improved catalytic activity. The maximum conversion of MA(94.1%)and selectivity of ethanol(91.3%) over optimized Cu-0.5 Ag/SiO_2 and 120 h on stream without deactivation under optimal conditions demonstrates its excellent stability.