载铜树脂处理高含盐氨氮废水的性能

针对高含盐氨氮废水,选择具有不同功能基团的树脂为载体,进行负载Cu2+改性制得载铜树脂并对其处理高含盐氨氮废水的性能进行研究。在筛选出最佳载铜树脂的基础上,研究pH及Na+浓度、树脂投加量、反应时间对载铜树脂处理高含盐氨氮废水效果的影响,通过对吸附氨氮前后的载铜树脂进行SEM和EDS表征分析并构建吸附动力学模型以进一步探究配位吸附的过程。结果表明,Cu2+可与螯合树脂D751稳定结合且在宽pH值下均表现出耐盐性和良好的氨氮吸附效果;在室温(25℃)、pH=11及Na+浓度4 g/L、树脂投加量8 g/L、反应时间60 min的条件下,D751载铜树脂对氨氮的去除率为34.8%。D751载铜树脂吸附氨氮后其表面出现明显的晶状结构物质,该物质可能为铜氨络合物。D751载铜树脂对高含盐氨氮的吸附符合准二级动力学模型。     

Acid Sites in HZSM‐5 Upon Copper Exchange by FTIR and DSC Using Ammonia

The acidity of the parent HZSM‐5 zeolite and Cu‐HZSM‐5 catalyst has been examined by FTIR and DSC using ammonia desorption. Sites of different strength were found in HZSM‐5, desorbing ammonia at a relative temperature difference of about 100 °C. Upon copper exchange a fraction of Brønsted sites were transformed to Lewis sites, but the acid strength of the remaining Brønsted sites was increased. Aside from Lewis sites originating from copper exchange, there might be some additional sites formed from precipitated copper. This could explain the quantity of adsorbed NH₃ on Cu‐ZSM‐5 which is higher than theoretically expected. While changing their nature, acid sites of higher strength keep their location, which is manifested by some diffusion effect towards ammonia.     

Effect of heating profile on desorption curve in temperature programmed desorption analysis: case study of acid sites distribution of SAPO-34

Comparison of the traditional linear heating method of TPD with an original stepwise heating scheme was reported for the first time. Stepwise heating TPD was carried out by keeping the temperature constant as soon as ammonia desorption signal rises until the signal returns to the baseline. More ammonia desorption peaks on a SAPO-34 catalyst were identified using TPD with stepwise heating. The effect of temperature ramp on desorption peak broadening in TPD curve was also addressed. The more distinct ammonia desorption peaks in stepwise TPD indicates that ammonia adsorbs in about five or six different ways on SAPO-34, and attribution of different adsorptions may be explained considering some known features of SAPO’s acidity; including adsorption on the bridge hydroxyl groups Brønsted acid sites with different acid strength resulting from different silicon environment of SAPO molecular sieves, adsorption on terminal hydroxyl groups Brønsted acid sites, and by multiple adsorption of ammonia on acid sites.     

Characterisation of a Commercial Automotive NH3-SCR Copper–Zeolite Catalyst

A commercial copper exchanged zeolite was characterised and studied regarding the selective catalytic reduction of nitrogen oxides (NO_X) by ammonia using physicochemical analyses (XRF, XRD, NMR, BET, UV–Visible, IR) and synthetic gas bench test rig, respectively. As expected, two adsorption sites were identified for ammonia: Brönsted and Lewis acid sites, the latter retaining stronger ammonia. Furthermore, ammonia and water adsorb on the same sites, and competition phenomena decrease ammonia storage capacity. Concerning the NO_X conversion, in spite of a high efficiency, an important selectivity into N₂O is noticed, due to the formation of an ammonium nitrate by-product on the catalyst surface. The limited NO_X conversion efficiency at low temperature is due to the weak NO oxidation activity, whereas NH₃ oxidation activity at high temperature involves a decrease in NO_X reduction.     

Density functional study on the reaction of CO molecules with MgO surfaces

Adsorption of CO to the MgO surface modeled by Mg_nO_n (n = 4, 6, 9, 10) clusters was investigated employing the density functional method, and modes of bonding, adsorption energies, and CO exchange mechanisms were discussed. The atoms at the low coordination sites possess the small amount of charges consistent with the crystal field theory. The adsorption to such sites results in large stabilization though the magnitude is less remarkable than in the case of hydrogen adsorption. A possible mechanism for the CO exchange reaction, observed experimentally, is presented based on the energetics calculated. The CO's adsorbed and in the gas phase are exchangeable through the two-molecule adsorption state, which is realized at the edge site or the O-atom defect site. For the latter, the structure of the intermediate is more consistent with the IR measurement.     

Theoretical Insight into the Nature of Ammonia Adsorption on Vanadia-Based Catalysts for SCR Reaction

Density functional theory (DFT) calculations were carried out on monomeric and oligomeric vanadium oxide clusters to probe the factors leading to the formation of NH₄ species from the adsorption of ammonia. The interaction of ammonia with monomeric vanadium oxide clusters leads to the formation of hydrogen-bonded NH₃ species, with energy changes for ammonia adsorption near -50 kJ/mol. The interaction of ammonia with oligomeric vanadium oxide clusters leads to the formation of bidentate NH_4 species, where the ammonium cation is coordinated between two V=O groups on adjacent vanadium cations. The energy change for ammonia adsorption in this mode is near -100 kJ/mol. Adsorption of ammonia as NH₄ species was not observed when the oligomeric vanadium oxide clusters were reduced by addition of hydrogen atoms, i.e., in clusters where the formal oxidation state of the vanadium cations was 4+. Based on our findings, a model for the generation of Brönsted acidity through the interaction of vanadium oxide oligomers with the titanium oxide support is proposed.     

Adsorption of Copper Ion with Metal Hydroxide from Ammonia Solution

Abstract

The removal of copper(II) from ammonia solution by adsorption on iron (III), aluminum(III), and tin(IV) hydroxide is studied. The effects of experimental parameters such as solution pH and concentration of total ammonia on adsorption are examined both from the change of solution composition and electrical properties of the solid surface. In a moderately high electrolyte concentration, an optimum solution pH is found for the solution composition when the sum of the species fractions of Cu(NH₃)²⁺, Cu(NH₃)₂ ²⁺, and Cu(NH₃)₃ ²⁺ reaches its maximum. The ligand number of aminecopper(II) of the solution is near 2.0 under this optimum condition. The decrease in adsorption in the more basic tetraamminecopper(II) solution is attributed to the competing reaction for copper(II) by the free ammonia in the solution. Adsorption isotherms at various concentrations of total ammonia show decreasing adsorption with high electrolyte concentration as a result of a highly positively charged surface and a reduction of available surface sites. The relative extent of adsorption is discussed for various experimental conditions based on the data and the surface complexation concept.     

The electrochemistry of nitrate-amide melts: Reactions of nickel and copper in nitrate-amide melts

Copper and nickel may be electrodeposited from their ions in solution in nitrate-amide melts at room temperature. In the ammonium nitrate-acetamide-urea melt at 23°C, the reduction to the metal competes with the corrosion reaction at low rates and with the reduction of the ammonium and nitrate ions of the melt at high current densities. Two distinct types of nickel complexes are found in solution. The nickel complex formed by the corrosion reaction is bound by at least one ammonia ligand. Nickel complexes formed by dissolving the halide in the melt show evidence of coordination by less strongly bounding ligands, probably by amides. Similarly, the visible spectra of copper chloride in solution suggest that the cupric ions are coordinated primarily by amides. The copper corrosion reaction produces a complex with a spectra distinctly different from that of cupric chloride in solution. The shift in absorption maxima suggests that the copper complex formed by the corrosion reaction has at least one ammonia ligand in the coordination sphere.     

Comparison of Oxidized Polycrystalline Copper Foil with Small Deposited Copper Clusters in Their Behavior in Ammonia Oxidation: An Investigation by Means of In Situ NEXAFS Spectroscopy in the Soft X-Ray Range

The oxidation of ammonia to nitrogen or nitric oxide was investigated using on the one hand a polycrystalline copper foil and on the other hand deposited copper clusters prepared with the inert gas aggregation technique. The behavior in the oxidation of ammonia of both model catalysts was studied using in situ near-edge X-ray absorption fine structure (NEXAFS) spectroscopy in the soft X-ray range and mass spectrometry. It is shown that the copper foil reacts in a similar way to the copper clusters. Differences appear only with respect to the reaction temperature required, which is lower for the cluster sample. It can be concluded that the results obtained in experiments with polycrystalline copper foil are exemplary for and can be transferred to a supported copper catalyst consisting of small copper particles.     

CO分子和C、O和H原子在Ni_n(n=4～13)团簇表面吸附的密度泛函理论研究

采用密度泛函理论(DFT)对Nin(n=4~13)团簇吸附CO分子和C、O和H原子进行了系统研究。结果表明:Nin(n=4~13)团簇对它们的吸附强度的大小顺序始终是COHCO,择优吸附位点是谷位;吸附后,CO的键长与自由的C-O键长(1.140?)相比有所增加(0.016~0.071?),这表明C-O键被削弱,CO被活化;比结合能(稳定性)由大到小的顺序是NinCONinCNinONinH和Nin,吸附后,团簇的稳定性普遍增加。     

负载型钯团簇上氢分子吸附和解离吸附的密度泛函理论

基于密度泛函理论考察勃姆石（AlOOH）和氧化锆（ZrO₂）负载的钯团簇表面氢分子吸附和解离吸附过程，通过分析一系列不同尺寸的钯团簇上氢吸附能以及氢分子-钯团簇-载体三者之间的电荷转移系统地研究了粒径效应和载体效应。结果表明，顶点位和面位分别是分子吸附和解离吸附的最佳吸附位置。随着钯团簇粒径的上升，氢分子吸附能和解离吸附能都下降，载体-钯团簇-被吸附氢三者之间的电荷转移量和方向也改变。氧化锆载体负载的钯团簇上分子吸附能和解离吸附能均大于勃姆石载体负载的钯团簇，说明载体对氢分子吸附过程有重要影响。     

Distribution of acid sites and differential heat of NH3 chemisorption on some aluminas and zeolites

The distribution and the strength of acid sites in some aluminas and zeolites were obtained from microcalorimetry measurements of ammonia adsorption. They were compared to the results of FTIR of adsorbed CO and of¹H²⁷Al cross-polarization (CP) MAS NMR using chemisorbed ammonia as proton reservoir. FTIR of CO adsorption yields the numbers of Lewis sites and CP MAS NMR gives the coordination of surface aluminum. In spite of the variety of catalysts and of acidity encountered, interesting correlations were found with both the energy of adsorption and singularities in the microcalorimetric titration. In particular, in zeolites a clear difference exists in the distribution of the Lewis and Brønsted acid site strengths with respect to the amount of irreversibly adsorbed NH₃.     

Comparison of cupric ion location and adsorbate interactions in Cu(II)-exchanged H-SAPO-5 and H-SAPO-11 molecular sieves determined by electron spin resonance and electron spin echo modulation spectroscopies

The locations and interactions of cupric ion exchanged into H-SAPO-11 and H-SAPO-5 molecular sieves with water, methanol, ethanol, ammonia, ethylene and pyridine have been compared by electron spin resonance and electron spin echo modulation spectroscopies. After dehydration, equilibration with ethylene and pyridine adsorbates was slower compared with that for more polar adsorbates. One major difference between these two molecular sieves in cupric ion coordination to adsorbates is that two waters are coordinated in CuH-SAPO-11 while three waters are coordinated to cupric ion in CuH-SAPO-5. This indicates different coordination sites for the cupric ion in these two molecular sieves of rather similar structure. By considering a particular location of the cupric ion, these coordination numbers can be understood, however. Another major difference involves coordination to ammonia; four ammonias are coordinated to cupric ion in CuH-SAPO-11 consistent with the cupric ion being located in the center of a 10-ring channel, while only three ammonias are coordinated in cupric ion to CuH-SAPO-5. This indicates a different coordination site for cupric ion between these two molecular sieves also with ammonia adsorbate. The coordination site in the SAPO-5 material for cupric ion is suggested to be the same for ammonia coordination and water coordination and is different from the site for water coordination in the SAPO-11 material.     

Microcalorimetric Investigation of the Interaction of Carbon Monoxide with Coprecipitated Cupric Oxide—Zinc Oxide Catalysts in Well-Defined Oxidation States

Carbon monoxide is readily adsorbed onto copper—zinc systems of different copper content. The adsorptive capacity, the heat and the kinetics of the interaction depend upon the oxidation state of the sample. The prevailing interaction on fully reduced samples is adsorption of carbon monoxide on copper metal, whereas in the case of partially oxidized samples and in that of cupric oxide—zinc oxide obtained by calcination of the precursor, redox reactions occur involving reduction of the surface, in parallel with the coordination of carbon monoxide on copper centres in various oxidation states. The heat of coordination of carbon monoxide onto copper (O) and copper (I) centres is in the range 66–43 kJ/mol and 110–66 kJ/mol respectively. The assignments have been made on the basis of the correspondence between carbonyl IR frequencies and heat of adsorption. Quantitative data on adsorption are also discussed in terms of the effect of the dispersion of the active phase and the role of the zinc oxide matrix.     

Characterization and selective poisoning of acid sites on sulfated zirconia

Microcalorimetric measurements and infrared spectroscopy of ammonia adsorption were used to characterize the acidic properties of sulfated zirconia catalysts. Reaction kinetic measurements forn-butane isomerization were conducted over catalysts that were selectively poisoned with controlled amounts of ammonia. Initial heats of ammonia adsorption on the strong acid sites of sulfated zirconia were 150–165 kJ/mol, and these sites contain Brønsted acid and possibly Lewis acid centers. Sulfated zirconia samples that show high activity for the isomerization ofn-butane possess Bransted acid sites of intermediate strength, with differential heats of ammonia adsorption between 125 and 140 kJ/mol. The results of selective poisoning of sulfated zirconia with ammonia confirm that Bransted acid sites of intermediate strength are active forn-butane isomerization at 423 K while not discounting a possible role of the stronger acid sites.     

沸石-炭复相材料对氨氮吸附性能研究

研究以沸石粉为主要原料,添加木屑、淀粉等有机物为碳化结合剂,通过造粒、氮气气氛低温热处理制备得到了粒度为0.5~1 cm的沸石-炭复相材料水处理剂颗粒,研究了不同碳化结合剂含量和不同热处理温度等氨氮超标污水的吸附性能影响。采用场发射扫描电镜对沸石-炭复相材料进行了显微形貌观察。通过氨氮吸附实验得出,相同质量条件下沸石-炭复相材料水处理剂颗粒在吸附速率上弱与沸石粉体,在足够吸附时间下对氨氮的吸附量同沸石粉体吸附量接近。5%碳化结合剂添加量样品有最优氨氮吸附性能,起始浓度为15 mg/L氨氮溶液被吸附24 h后氨氮溶液浓度降为4.69 mg/L,氨氮吸附量为1.03 mg/g;吸附100 h后氨氮溶液浓度降为1.35 mg/L,氨氮吸附量为1.36 mg/g。     

Kinetics of the selective catalytic reduction of nitric oxide with ammonia on a platinum catalyst

The selective catalytic reduction of nitric oxide with ammonia on an alumina-supported platinum catalyst has been studied by the method of differential reactor analysis. In the temperature region of 400–600 K and concentrations of 0–1000 ppm of ammonia and nitric oxide and 0–1% oxygen three reactions are important: oxidation of ammonia by oxygen to nitrogen, reduction of nitric oxide by ammonia to nitrogen and reduction of nitric oxide by ammonia and oxygen to nitrous oxide. The differential reactor data were fitted to several Langmuir—Hinshelwood models using a non-linear least squares fitting computer program. The fitted models were tested by simulation of integral reactor data. The best fits were obtained from a dual site Langmuir—Hinshelwood model involving associative adsorption of ammonia and nitric oxide on the same sites and associative adsorption of oxygen on different sites.     

Investigation into adsorption equilibrium and thermodynamics for water vapor on montmorillonite clay

The isothermal adsorption curves for water vapor on montmorillonite were measured by a gravimetric adsorption system. Dent's model was employed to estimate the adsorption behaviors of water vapor on primary adsorption sites and secondary adsorption sites. The thermodynamics analysis of water vapor adsorption was performed. At low vapor pressure region, primary adsorption predominates, and with increasing vapor pressure, secondary adsorption becomes notable. Primary adsorption sites have an evidently stronger adsorption affinity than secondary adsorption sites. With increasing vapor pressure, Gibbs free energy variation rapidly increases and then reduces slowly. Although increasing vapor pressure raises adsorption spontaneity on primary adsorption sites, the enhancement in vapor pressure decreases the spontaneity of water vapor adsorption on secondary adsorption sites. As adsorbed loading increases, isosteric heat of adsorption and entropy loss decrease first and then increase quickly. The gradually growing water clusters are responsible for the increase of entropy loss at late stage.     

NH3-TPD and FTIR spectroscopy of pyridine adsorption studies for characterization of Ag- and Cu-exchanged X zeolites

Pure crystalline NaX zeolites with Si/Al = 1.2 is prepared by the hydrothermal method. The modification is achieved by following the conventional ion-exchange technique to obtain Ag- and Cu-exchanged forms of NaX zeolite with different metal loadings ranging from low to high exchange. Compositional and structural investigations of all samples are performed by atomic absorption spectrometry, elemental analysis, powder XRD, and nitrogen adsorption porosimetry. The acidity of all exchanged zeolites is investigated using both the ammonia temperature-programmed desorption (NH₃-TPD) carried out by microbalance, and the pyridine adsorption performed via Fourier transform infrared spectroscopy (FTIR). XRD analysis shows the global conservation of the zeolitic structure after ionic exchange. The crystallinity loss is more important for zeolites exchanged at high degree of copper. Porosity measurements indicate a decrease of the porous volumes and the specific surface areas when the Ag or Cu exchange degree is raised. Mesopores particularly appear at high exchange degree of copper. NH₃-TPD indicates that the increase of Ag and Cu-exchange degrees leads to an increase of the global acidity, which is more pronounced for Cu-exchanged zeolites. The strength of acid sites for Ag-exchanged zeolites is weaker than for Cu-exchanged zeolites. The FTIR spectroscopy analysis by pyridine adsorption confirms the formation of extra framework aluminum (EFAL) species, inducing an increase in the concentration and the strength of the Lewis acidity. The formation of EFAL is more important for Cu-exchanged zeolites.     

Enhanced synergy between Cu0 and Cu+ on nickel doped copper catalyst for gaseous acetic acid hydrogenation

As the substitution of common noble catalysts in the hydrogenation of carboxylic acid, a highly effective Cu-Ni/SiO₂ catalyst was prepared by a novel stepwise ammonia evaporation method. Its performance in the gas-phase hydrogenation of acetic acid was further examined. With the introduction of Ni dopant, more stable Cu^δ+ sites, which can adsorb more acetic acid, were formed due to the electron transfer from Cu to Ni. This makes more Cu⁰ sites available for hydrogen adsorption, which was suggested as the rate-determining step in acetic acid hydrogenation. A conversion of 99.6% was successfully achieved on this new Cu/SiO₂-0.5Ni catalyst, accompanied by the ethanol selectivity of 90%. The incorporation of nickel between copper nanoparticles enhances the synergistic effect between Cu⁰ and Cu⁺. It also helps mitigate the aggregation of copper nanoparticles due to the Ostwald ripening effect induced by acetic acid and enhance the stability of copper catalyst in the conversion of carboxylic acid.