不同稀土改性SO42-/ZrO2催化剂的结构与性能表征

Solid superacid catalyst SO₄^2-/ZrO₂ was modified by different rare earth compounds and applied to the esterification of acetic acid and n-butanol. The effects of rare earth elements loading on the catalytic properties were studied and the correlation between the structure and properties was investigated by means of XRD, IR, UV, DTA and TG. The results show that the (NH₄)₂Ce(NO₃)₆ modification can enhance catalytic activity more and exhibit better stability than the other two compounds La(NO₃)₃ and Ce(NO₃)₃. Meanwhile,(NH₄)₂Ce(NO₃)₆ modification can restrain the loss of SO₄^2- efficiently. The optimum calcination temperature and molar ratio of Ce(NH)∶Zr for SO₄^2-/ZrO₂ catalyst modified by (NH₄)₂Ce(NO₃)₆ are 450 ℃ and 2, respectively.     

两种具有二次谐波响应的紫外透过氨基磺酸盐A(NH2SO3)(A=Li、Na)

通过简便的蒸发方法得到了 2种碱金属磺酸盐非线性光学(NLO)晶体, 即 Li(NH₂SO₃)和 Na(NH₂SO₃)。Li(NH₂SO₃)以极性空间群Pca2₁(编号 29)结晶。Li(NH₂SO₃)的结构可以描述为由[LiO₄]7-多面体通过共角连接与 NH₂SO₃^-四面体相互连接而形成的三维网络。Na(NH₂SO₃)以极性空间群 P2₁2₁2₁(编号 19)结晶。Na(NH₂SO₃)的结构可以描述为由扭曲的[NaO₆]^11-八面体通过共角连接与 NH₂SO₃^-四面体相互连接而形成的三维网络。紫外可见近红外光谱表明, Li(NH₂SO₃)和 Na(NH₂SO₃)分别具有 5.25 和 4.81 eV 的大光学带隙。粉末二次谐波发生(SHG)测量显示, Li(NH₂SO₃)和 Na(NH₂SO₃)的 SHG 强度分别为 KH₂PO₄的 0.32 倍和 0.31倍。第一原理计算证实, 非线性光学性能主要来自氨基磺酸阴离子和碱金属氧阴离子多面体的协同作用。     

NH3-SCR脱硝催化剂抗硫性能的研究进展

氮氧化物(NO_x)是一种重要的大气污染物, 它造成严重的环境问题, 同时威胁人类健康. 以钢铁烧结烟气为代表的固定源和以柴油机尾气为代表的移动源是氮氧化物的主要来源. 氨气选择性催化还原法(NH₃-SCR)是目前最有效且应用最广泛的NO_x脱除技术. 然而, 无论是固定源还是移动源上NH₃-SCR催化剂, 都不可避免地会被SO₂毒化, 造成催化剂失活, 限制了NH₃-SCR技术的进一步应用. 因此, 研究NH₃-SCR催化剂的SO₂中毒机制以及提高催化剂的抗硫性能至关重要. 我们对固定源脱硝的金属氧化物和移动源上脱硝的Cu基分子筛这两类不同催化剂体系的SO₂中毒机制的研究进展进行了介绍, 并对这两种催化剂上提高抗硫性能改性方法的研究进展进行了评述, 为未来的研究提供了参考.     

纳米Mn-Zn铁氧体的制备和研究

Nanosize manganese zinc ferrites were fabricated by hydrothermal precipitation route using Fe₂(SO₄)₃, ZnSO₄·7H₂O, MnSO₄·H₂O as material, then some calcinated at 500 ℃ and studied by XRD, TEM, IR and VSM. The results showed that the products were spinel crystal structure and uniformly sized nanoparticles (15～25 nm) with little aggregation. The analysis of IR showed that the superficial water can be eliminated, but that was embedded in crystal lattice can not be removed by calcinating. The effect Zn content x on the lattice (a) of nanosize Mn_1-xZn_xFe₂O₄ was also discussed. The lattice of nanosize Mn_1-xZn_xFe₂O₄ decreases with x increasing; and its value deviated the standard lattice (a₀) of normal size manganese zinc ferrites. A lot of water was absorbed during the hydrothermal process owing to the large surface of nanosize particles. The change of magnetic properties of Mn_xZn_1-xFe₂O₄ with x increasing was studied: nanosize Mn_xZn_1-xFe₂O₄ particles synthesized by us exhibited peculiar magnetic properties curve with Zn content (x) increasing, Superparamagnetic behaviors of the synthesized ZnFe₂O₄ samples were confirmed by magnetic characterization, which can be explained by the difference between the distribution of the metal ions (Mn²⁺, Zn²⁺ and Fe³⁺) among the tetrahedral (A) and the octahedral (B) sites of nanosize ferrite and that of bulk ferrite.     

Zr的添加对提高NH3选择性催化还原NOx整体式催化剂热稳定性的影响

采用共沉淀的方法制备了CeTiO_x和CeZrTiO_x两种用于NH₃选择性催化还原NO_x的催化剂.两种催化剂在不同的高温条件下进行热老化以考察Zr的添加对CeTiO_x催化剂热稳定性的影响.NH₃-SCR活性数据显示,经过650、750和850 ℃的高温老化处理,Zr改性后的催化剂较CeTiO_x催化剂具有更好的催化活性和N₂选择性.XRD、Raman和H₂-TPR结果表明添加Zr可以阻止Ce物种的烧结并且抑制金红石相TiO₂的生成.催化剂的SEM图像显示Zr的添加可以抑制颗粒随着焙烧温度升高而产生的聚集长大.XPS的Ce3d光谱表明,随着老化温度的提升,CeTiO_x催化剂表面的Ce³⁺/Ce⁴⁺比相对于CeZrTiO_x催化剂下降更加明显.这意味着随着Zr的添加,更多的晶格缺陷和氧空缺出现在Zr改性催化剂的表面,这有利于催化性能的提升.另外,NH₃-TPD结果表明经过相同的高温老化,改性的催化剂保持了更多的Brönsted酸性位,提高了催化活性并抑制了氨的氧化.因此,Zr的添加提高了催化剂的热稳定性能.     

两个4-连接配位网络的锌(Ⅱ)配位聚合物的合成、结构和荧光性质

以5-氨基四氮唑(HATz), 异烟酸(HPyc)和ZnSO₄·7H₂O或Zn(NO₃)₂·6H₂O为反应物, 在DMF溶剂热条件下分别得到了2个锌(Ⅱ)配位聚合物{[(CH₃)₂NH₂]·[Zn(ATz)(SO₄)]}_n (1)和{[Zn(ATz)(Pyc)]·0.5DMF}_n (2), 并对它们的组成和结构进行了表征。配合物1是由4-连接(4, 4)网络拓扑的[Zn(ATz)(SO₄)]_n^n-二维阴离子层和[(CH₃)₂NH₂]⁺阳离子间通过氢键作用形成的二维波浪层结构。配合物2则是1个二重穿插的4-连接金刚烷拓扑的三维微孔金属-有机框架结构, 客体DMF分子填充在孔道内。室温下的固体荧光实验表明, 在350 nm的光激发下, 配合物1和2分别在为445 nm和458 nm处出现强烈的荧光发射。     

铈钛混合氧化物负载磷钨酸吸附-分解NOx性能

通过软化学途径合成了铈钛混合氧化物(CeO₂-TiO₂)载体材料, 并分别通过等体积浸渍法和机械研磨法负载磷钨酸(H₃PW₁₂O₄₀)。采用FTIR、XRD、SEM和BET比表面积测定对CeO₂-TiO₂及负载型多酸催化剂进行了表征;考察了负载量、负载方法、吸附温度等因素对催化剂吸附NO_x效率的影响;选取吸附性能最佳的催化剂进行了NO_x催化分解实验, 探讨了NO_x吸附-分解机理。结果表明:相对于等体积浸渍法, 机械研磨法更适合此类载体负载H₃PW₁₂O₄₀, 其NO_x吸附效率均高于H₃PW₁₂O₄₀及载体本身;在0~60%的负载量范围内, 随着H₃PW₁₂O₄₀负载量的增加, 负载型催化剂吸附NO_x的效率呈上升趋势, 负载量为40%时NO_x吸附效率最佳, 达90%;吸附过程中NO_x与催化剂活性组分H₃PW₁₂O₄₀发生作用, 生成NOH⁺, H₃PW₁₂O₄₀二级结构中结晶水对催化剂吸附NO_x有重要作用;当温度从150℃升至 450℃时, 被吸附的NO_x发生分解, 分解产物的组成与N₂的收率均受升温速率的影响, 升温速率越快, N₂收率越高。向吸附分解NO_x后的催化剂床层通入含有水蒸气的空气, 可有效补充NO_x分解过程中H₃PW₁₂O₄₀失去的结晶水, 从而恢复催化剂优良的NO_x吸附分解性能, 实现催化剂的有效再生利用。     

硫酸镉无机层和原位反应生成的吡啶基四氮唑有机配体构筑的两个层-柱状三维无机-有机杂化材料:合成和表征

以硫酸镉、叠氮化钠和4-氰基吡啶或3-氰基吡啶为反应物,在水热条件下,通过原位反应分别得到了2个基于硫酸根离子和5-(4-吡啶基)四氮唑(4-Hptz)或5-(3-吡啶基)四氮唑(3-Hptz)配体的,具有三维层-柱状框架结构的无机-有机杂化材料,即[Cd₂(H₂O)(OH)(SO₄)(4-ptz)]_n(1)和[Cd₂(OH)(SO₄)(3-ptz)]_n(2)。通过元素分析、红外光谱、热重分析以及单晶和粉末X-射线衍射分析对它们的组成和结构进行了表征。在配合物1和2的结构中,每个镉(Ⅱ)离子的配位数均为6,处于扭曲的八面体配位环境中,SO₄^2-和OH-阴离子连接镉(Ⅱ)离子扩展形成碱式硫酸镉的二维无机阳离子层结构[Cd₂(H₂O)(OH)(SO₄)]_nⁿ⁺(1)或[Cd₂(OH)(SO₄)]_nⁿ⁺(2),相邻的二维无机阳离子层间再通过4-ptz^-(1)或3-ptz^-(2)进一步柱连接,形成三维层-柱状结构的无机-有机杂化框架结构。室温下的固体荧光实验表明,在350nm的光激发下,配合物1和2分别在481和489nm处出现强烈的荧光发射。     

NH3-SCR反应过程中NH3和NOx在Cu/SAPO-34分子筛催化剂上的吸附特性和作用

通过离子交换法制得Cu/SAPO-34菱沸石分子筛催化剂, 同时研究了NH₃和NO_x (NO和NO₂)在该催化剂上的吸附位、吸附强度、吸附量和吸附速率, 得到了不同反应气氛在Cu/SAPO-34 上的吸附性能及其在NH₃选择性催化还原(NH₃-SCR)反应中的作用. 研究采用瞬态实验、程序升温脱附(TPD)和漫反射傅里叶变换红外光谱(DRIFTS)等方法进行表征实验. 瞬态实验结果表明NH₃是吸附性气体. 程序升温脱附实验和红外漫反射实验结果表明NH₃可以吸附在布朗斯特和路易斯酸性位上形成不同的NH₃物种, 它们显示不同的SCR活性. NH₃在Cu²⁺上的吸附速率最快, 且键强最强. NO_x可以氧化并以硝酸盐/亚硝酸盐的形式吸附在Cu物种上. 最后, 本文讨论了NH₃选择性催化还原反应过程中在Cu物种上的中间物种并推测反应机理.     

硫酸镉无机层和原位反应生成的吡啶基四氮唑有机配体构筑的两个层-柱状三维无机-有机杂化材料:合成和表征

以硫酸镉、叠氮化钠和4-氰基吡啶或3-氰基吡啶为反应物,在水热条件下,通过原位反应分别得到了2个基于硫酸根离子和5-(4-吡啶基)四氮唑(4-Hptz)或5-(3-吡啶基)四氮唑(3-Hptz)配体的,具有三维层-柱状框架结构的无机-有机杂化材料,即[Cd₂(H₂O)(OH)(SO₄)(4-ptz)]_n(1)和[Cd₂(OH)(SO₄)(3-ptz)]_n(2)。通过元素分析、红外光谱、热重分析以及单晶和粉末X-射线衍射分析对它们的组成和结构进行了表征。在配合物1和2的结构中,每个镉(Ⅱ)离子的配位数均为6,处于扭曲的八面体配位环境中,SO₄^2-和OH^-阴离子连接镉(Ⅱ)离子扩展形成碱式硫酸镉的二维无机阳离子层结构[Cd₂(H₂O)(OH)(SO₄)]_nⁿ+(1)或[Cd₂(OH)(SO₄)]_nⁿ+(2),相邻的二维无机阳离子层间再通过4-ptz^-(1)或3-ptz^-(2)进一步柱连接,形成三维层-柱状结构的无机-有机杂化框架结构。室温下的固体荧光实验表明,在350 nm的光激发下,配合物1和2分别在481和489 nm处出现强烈的荧光发射。     

Chemical Composition and Reaction Mechanisms for Aged p‐Xylene Secondary Organic Aerosol in the Presence of Ammonia

A laboratory study was carried out to investigate the chemical composition of aged aromatic secondary organic aerosol (SOA) formed from the photoxidation of p‐xylene in the presence of ammonia (NH₃). The experiments were conducted by irradiating p‐xylene/CH₃ONO/NH₃ air mixtures without and with NO in a home‐made smog chamber. The particulate products of aged p‐ xylene SOA in the presence of NH₃ were measured by UV–vis spectrophotometry, attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectroscopy, and aerosol laser time‐of‐flight mass spectrometry (ALTOFMS) coupled with the fuzzy C‐means (FCM) clustering algorithm. The experimental results show that NH₃ does not alter the gas–particle partitioning in the photoxidation of p‐xylene without NO and that 2,5‐dimethylphenol is the predominant NH₃‐aged p‐xylene SOA without NO. However, NH₃ has a significant promotional effect on the formation of organonitrogen compounds in the OH‐initiated oxidation of p‐xylene with NO. Organic ammonium salts such as ammonium glyoxylate and p‐methyl ammonium benzoate, which are formed from NH₃ reactions with gaseous organic acids, were detected as the major particulate organonitrogen products of NH₃‐aged p‐xylene SOA with NO. 1H‐Imidazole, 4‐methyl‐1H‐imidazole, and other imidazole products of the heterogeneous reactions between NH₃ and dialdehydes of p‐xylene SOA were newly measured. The possible reaction mechanisms leading to these organonitrogen products are also discussed and proposed. The formation of imidazole products suggests that some ambient particles containing organonitrogen compounds may be the result of this mechanism. The results of this study may provide valuable information for discussing anthropogenic SOA aging mechanisms.     

Formation of ring-retaining products from the OH radical-initated reactions of o-, m-, and p-xylene

The ring-retaining products formed from the OH radical-initiated reactions of o-, m-, and p-xylene in the presence of NO_x have been identified and their formation yields determined. Experiments were carried out at 298 ± 2 K and in the presence of 740 torr total pressure of air. The products observed, and their yields, were: from o-xylene, o-tolualdehyde, 0.0453; 2-methylbenzyl nitrate, (0.0135 + 5.5 × 10^?17 [NO₂]); 2,3-dimethylphenol, 0.097; 3,4-dimethyl-phenol, 0.064; 3-nitro-o-xylene, 0.0059; 4-nitro-o-xylene, (0.0111 + 9.9 × 10^?17 [NO₂]); from m-xylene, m-tolualdehyde, 0.0331; 3-methylbenzyl nitrate, 0.0061; 2,4-dimethylphenol, 0.099; 2,6-dimethylphenol, 0.111; 4-nitro-m-xylene, 0.0018; 5-nitro-m-xylene, (0.0032 + 1.6 × 10^?17 [NO₂]); from p-xylene, p-tolualdehyde, 0.0701; 4-methylbenzyl nitrate, 0.0082; 2,5-dimethylphenol, 0.188, 2-nitro-p-xylene, (0.0120 + 2.8 × 10^?17 [NO₂]), where the NO₂ concentration is in molecule cm^?3 units. The nitro-xylene data are consistent with our recent product study of the corresponding reactions of benzene and toluene and indicate that under the experimental conditions employed the dimethylhydroxycyclohexadienyl radicals reacted with NO₂ and not with O₂. When combined with literature ring-cleavage product yields, these data show that ca. 55–80% of the reaction pathways are accounted for.     

THERMAL REACTIONS IN SYNTHETIC APATITE–AMMONIUM SULFATE MIXTURE

The thermal reactions in the mixtures of hydroxylapatite or fluorapatite and (NH₄)₂SO₄up to 500°C were studied with the purpose of elaborating the conditions of obtaining calcium–ammonium cyclophosphate that could be used as fertilizer. Thermal analysis with a simultaneous FTIR analysis of the evolved gases as well as the analyses of chemical and phase composition of solid products were performed. The thermal changes in the mixtures could be divided into three steps: (1) decomposition of (NH₄)₂SO₄and reactions of apatite with these products at 250–420°C, (2) calcium ammonium polyphosphate formation at 290–450°C, and (3) reaction of CaSO₄with CaNH₄P₃O₉at 320–500°C. Higher concentrations of NH₃in the gas phase promote the formation of CaNH₄P₃O₉and increase its stability. Calcination at temperatures above 350°C causes decomposition of CaNH₄P₃O₉with a decrease in the content of water-soluble phosphorus and evolvement of SO₂.     

Identification of secondary organic aerosols based on aerosol mass spectrometry

Secondary organic aerosol (SOA) is one of the major components of aerosols in the atmosphere and has not been well understood so far. Due to the complex chemical composition of organic aerosols, the identification of SOA has been a hotspot and difficult issue in the field of aerosol study. This study attempts to quantitatively identify SOA in winter of Shenzhen based on positive matrix factorization (PMF) analysis. Major sources were resolved and SOA was identified subsequently according to the characteristic ion fragments measured by highly time-resolved aerosol mass spectrometer measurement. It showed that in the winter of Shenzhen the average SOA concentration was 9.41 ± 6.33 μg/m³, accounting for 39.9 ± 21.8% of the total organic mass. Compared with primary organic aerosol (POA), the SOA concentrations had no large variation, suggestive of characteristics of regional secondary pollutants. The ratio of SOA/BC had pronounced diurnal variation, similar to that of O _x (O₃+NO₂), indicating SOA formation was significantly controlled by activity of photochemistry in the atmosphere. The most effective period for SOA formation was from 9 am ～3 pm since the SOA/BC ratio increased by 122% during this period. This study provides a new technical method and a new idea for SOA investigation.     

Sulfation of Polysaccharides using Monomethyl Sulfate

ABSTRACT

The polysaccharides, curdlan, starch and dextran were sulfated when heated in DMSO with sodium methyl sulfate and a catalytic amount of H₂SO₄ or with pyridinium methyl sulfate. Use of diminished pressure and anhydrous CaSO₄ as a desiccant improved the degree of sulfation and recovery. Under conditions using sodium methyl sulfate, H₂SO₄ and CaSO₄ in vacuo, sulfation at O-6 was predominant in the cases of curdlan and starch, while sulfation at O-2 and O-3 was preferential in the case of dextran.     

Atmospheric corrosion of copper and silver influenced by particulate matter

The atmospheric corrosion of copper and silver influenced by graphite and alumina as particulate matter (PM) in an environment containing 200 μg m^?3 SO₂ + 150 μg m^?3 NO₂ at 85% RH and 25 °C was analyzed. Different proportions of PM mixture conditions were used, and the corrosion rate was followed using gravimetric analysis. Results of linear sweep voltammetry (LSV) and coulometric reduction (CR) indicated that larger corrosion rates were obtained in the presence of deposited PM. Under present exposure conditions, copper corrosion rate was larger than silver corrosion rate. X-ray diffraction (XRD) shows the presence of cuprite (Cu₂O) and brochantite (Cu₄SO₄(OH)₆) in the case of copper and achantite (Ag₂S) in the case of silver.     

Thermal decomposition behavior of the rare-earth ammonium sulfate R2(SO4)3·(NH4)2SO4

Rare-earth ammonium sulfate octahydrates of R₂(SO₄)₃·(NH₄)₂SO₄·8H₂O (R=Pr, Nd, Sm, and Eu) were synthesized by a wet process, and the stable temperature region for the anhydrous R₂(SO₄)₃·(NH₄)₂SO₄ form was clarified by thermogravimetry/differential thermal analysis, infrared, Raman, and electrical conductivity measurements. Detailed characterization of these double salts demonstrated that the thermal stability of anhydrous R₂(SO₄)₃·(NH₄)₂SO₄ is different between the Pr, Nd salts and the Sm, Eu salts, and the thermal decomposition behavior of these salts was quite different from the previous reports.     

Crystal structures and physicochemical properties of mixed salts of ammonium nitrate and sulfate

Mixed salts (NH₄)₂SO₄·2NH₄NO₃ (1) and (NH₄)₂SO₄·3NH₄NO₃ (2) were synthesized and studied by X-ray diffraction analysis. The unit cell parameters of these salts were determined and their crystal structures were solved. The thermal stability of the salts was studied by differential scanning calorimetry and thermogravimetric analysis. The temperatures and enthalpies of incongruent melting of compounds 1 and 2 were determined. The enthalpies of formation from the constituent salts were estimated.     

TLC Determination of Aliphatic Polyamines on Calcium Sulfate Layers

Biogenic polyamines are sensitive markers for various diseases including cancer. Polyamines are difficult to analyze by chromatography due to their high polarity and water-solubility so that derivatization is an essential step for their chromatographic analysis. Earlier studies have shown the efficacy of calcium sulfate (CaSO₄) as a TLC coating material for the separation of polar compounds. The aim of this study was to explore the potential of CaSO₄ for the analysis of aliphatic polyamines without derivatization. The TLC of six polyamines (ornithine, citrulline, putrescine, cadaverine, spermidine and spermine) was carried out on CaSO₄ and silica gel plates using 11 different mobile phases. The results showed that CaSO₄ is superior to silica for the separation of underivatized polyamines. The development time of the CaSO₄ plates was also about one-third shorter as compared to silica. Methanol was the only solvent to produce differential R _F values for the polyamines studied. Ornithine (R _F , 0–2) and citrulline (R _F , 1–3) were separated from cadaverine (R _F , 0.93), spermine (R _F , 0.85) and spermidine (R _F , 0.85). For quantitative analysis, the polyamines were eluted from the coating material scratched from the plate and the absorbance of the supernatant was measured at 550 nm. The limits of detection (LOD) and quantification (LOQ) were found to be 0.75 and 1.88 μg, respectively. The procedure was applied to the quantitative separation of polyamines in spiked human urine samples (12.5–50 μg). This is probably the first study reporting a TLC method for the separation of underivatized polyamines.     

Evaluation of airborne particles at the Alhambra monument in Granada, Spain

As a part of an ongoing investigation regarding the air quality at the Alhambra monument (UNESCO World Cultural Heritage), indoor and outdoor atmospheric aerosols (PM₁ and PM_10-1) and pollutant gases (O₃, NO₂, SO₂ and NH₃) were studied during summer and winter. Bulk elements, ionic compounds and black carbon (BC) in aerosols were analyzed with X-ray fluorescence spectrometry, ion chromatography and aethalometry/reflectometry, respectively. Natural PM_10-1 aerosols, such as carbonate-rich soil and sea salts, reacted with a typical urban atmosphere, producing a mixture of particulates with diverse chemical composition. The content/formation of secondary inorganic aerosols depended on the air temperature and absolute humidity. Ratios of typical mineral elements (i.e., Ti/Fe and Si/Fe) showed that Saharan dust events contribute to the composition of the observed mineral aerosol content. BC, V and Ni originated from diesel exhaust, while Cu, Cr, Pb and Zn came mainly from non-exhaust vehicular emissions. Weathering phenomena, such as blackening and pigment discoloration, which could arise from gradual aerosol deposition indoors, are discussed.