Evidence for the instability of surface oxygen at the Zn(0001)-O-Cu interface from core-level and X-ray induced Auger spectroscopies

By monitoring the O(1s) and Zn(LMM) Auger spectra it has been shown that the deposition of copper atoms at a Zn(0001)-O overlayer results in the desorption of oxygen with simultaneous reduction of Zn²⁺ to Zn⁰ at 300 K. The surface concentrations of oxygen and copper adatoms are calculated from the O(1s) and Cu(2p) intensities while the X-ray induced Auger Zn(LMM) transition provides evidence for Zn²⁺ and its reduction to Zn⁰. The driving force for oxygen desorption is suggested to arise from the formation of a copper-zinc intermetallic brass-like overlayer which has little affinity for oxygen.     

ZnMgAl复合氧化物五催化合成丙二醇苯醚

以不同类水滑石化合物为前驱体制得的复合氧化物作为合成丙二醇苯醚反应的固体碱催化剂，考察了催化剂组成、结构及反应条件对催化合成丙二醇苯醚反应的影响。结果发现，在所制备的固体碱催化剂中ZnMgAl复合氧化物显示出高效的催化活性和选择性，在催化剂用量为1. 1%，C₆H₅OH/PO摩尔比为1∶1，反应温度为413 K和反应时间为5 h的条件下，环氧丙烷的转化率达到97. 2%，丙二醇苯醚的选择性达93. 4%。     

氢化物原子吸收光谱法测定磷复肥中的砷含量

介绍一种磷复肥中微量砷的测定方法。将混酸消解处理后的试样,在盐酸介质中,采用氢化物原子吸收光谱法测定砷含量。本方法相关系数r=0.9978,加标回收率范围在99.12%～107.10%。     

On the nature of surface acid sites of chlorinated activated carbons

Two activated carbons containing different amounts of chlorine were obtained by chlorination of an activated carbon prepared from olive stones. Variations in surface physics and chemistry of the samples were studied by N₂ and CO₂ adsorption, mercury porosimetry, TPD, XPS, pH_PZC measurements, and by testing their behaviour as catalysts in the decomposition reaction of isopropanol. Our results indicate that chlorination of activated carbon increases its Lewis acidity but decreases its Brönsted acidity, which can be explained by the resonance effect introduced into the aromatic rings of graphene layers by the chlorine atoms covalently bound to their edges. This resonance effect could also explain the changes observed in the thermal stability of C-Cl and C-O bonds.     

Re-investigation of titanium silicalite by X-ray absorption spectroscopy: Are the novel titanium sites real?

EXAFS studies have been carried out on titanium silicalite-1 (TS-1). The titanium atom is coordinated to four oxygen atoms at the distance of 1.80(1) Å. There is no evidence for the presence of 5- and 6-coordinated titanium species or the novel 4-coordinated titanium species involving [TiO _x ] units sharing edges with [SiO₄] units. The EXAFS spectrum of TS-1 appears to be consistent with the model that titanium resides at the tetrahedral sites of the framework.     

原子吸收分光光谱法测定复混肥料中的镁

建立了测定复混肥料中镁的原子吸收分光光谱法,样品的相对标准偏差为3．68％,回收率在96．8％-103．0％之间、镁的检出限为2．6μg/L;与国家标准检测结果相对误差最高为1．49％,本法相对复混肥料国家标准中镁的测定方法而言操作简便、快速、准确度高。     

Characterization of Pd-based FCC CO/NOx control additives by in situ FTIR and extended X-ray absorption fine structure spectroscopies

Pdⁿ⁺/Ceⁿ⁺/Na⁺/γ-Al₂O₃-type materials used as FCC additives for CO/NO_x control were characterized by extended X-ray absorption fine structure (EXAFS) spectroscopy and in situ FTIR. The EXAFS data indicate that in freshly prepared samples palladium is present in the form of highly dispersed PdO species. Reduction with H₂ at 500 °C leads to the formation of small Pd clusters incorporating on average approximately six to eight metal atoms at a Pd−Pd bond distance of 2.76 Å. All components of these materials can interact with NO and promote the formation of nitrate/nitrite species, essentially “trapping” NO_x species on the catalyst surface. However, the Na⁺ species dominate the surface chemistry and readily form sodium nitrates with a characteristic IR band at 1370–1385 cm⁻¹. Finally, hydroxyls from the support are also actively participating in the formation of HNO_x type compounds with characteristic stretching vibrations in the 3500–3572 cm⁻¹ region.     

Generation of electron accepting surface sites in carbon blacks by peracetic acid oxidation

Surface oxidation of three different carbon blacks was carried out using peracetic acid. An electron spin resonance investigation of these oxidized blacks revealed that a significant number of surface sites were generated. These surface sites were in equilibrium with the bulk conduction electrons as evidenced by the large deviation from the Curie Law. Electrochemical reduction of these blacks also resulted in electron transfer to these surface sites as evidenced by ESR. The ESR results on the reduced and oxidized carbon blacks correlated with the measured contact potentials. This is consistent with a mechanism of electron acceptance by surface sites during contact electrification in a xerographic developer system.     

Effect of surface sites of TiO2 support on the formation of cobalt-support compound in Co/TiO2 catalysts

This study has addressed the effect of surface sites (as Ti⁴⁺ and Ti³⁺) of TiO₂ support on the formation of the cobalt-support compound on Co/TiO₂ catalyst. A 20% cobalt was prepared on each TiO₂ support having the different Ti⁴⁺/Ti³⁺ ratios covering on the surface (1.2, 1.3, 1.4, and 1.6). It can be concluded that the non-reducible compound as a Co-SCF preferred to form on the Co/TiO₂ catalyst when the most proportional site of surface TiO₂ became Ti⁴⁺. This is because the migration of cobalt cluster, which plays the significant role for creating Co-SCF, can be promoted by the increasing of Ti⁴⁺ sites resulting in the decrease of cobalt dispersion. The hyperfine patterns of ESR spectra demonstrated that the Co⁰(H_xTiO_y) was the simple chemical form of Co-SCF formed after standard reduction. Moreover, the structure of Co-SCF changed to be a higher non-uniform structure when the number of Ti⁴⁺ site on TiO₂ surface increased. The possible mechanism to form this compound has also been discussed.     

Effect of hydrotalcite on the swelling and mechanical behaviors for the hybrid nanocomposite hydrogels based on gelatin and hydrotalcite

A series of hybrid nanocomposite hydrogels, based on gelatin and intercalated hydrotalcite (IHT), crosslinked with glutaraldehyde, was prepared in this study. The microstructures of the IHT and sample gels were identified by X‐ray diffraction (XRD). Swelling behaviors and physical properties of these hybrid gels were investigated. XRD results indicated that exfoliation of IHT was achieved in the hybrid nanocomposite gels. The results indicated that adding a small amount of IHT could effectively decrease the swelling ratio of the hybrid gels, but adding excess IHT could increase the swelling ratio of the nanocomposite hybrid gels. The crosslinking densities (ρ_x) of the present gels varied with IHT content and swelling ratio of the gels. The drug release behaviors of these gels were also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 500–507, 2006     

硝酸生产酸吸收率计算集锦

本文介绍酸吸收率计算式的多种不同方法，并作了酸吸收率不等于酸吸收塔吸收率的证明．     

Synthesis and characterisation by X-ray absorption spectroscopy of a suite of seven mesoporous catalysts containing metal ions in framework sites

MCM-41 type mesoporous silicas have been prepared in which one or more of the following elements are accommodated in framework sites: titanium, iron, chromium, vanadium, manganese, boron and aluminium. XRD and FTIR are used as aids to characterisation, which is achieved chiefly — and to a degree that arrives at valence states, bond lengths and coordination numbers of the metal ion — by X-ray absorption spectroscopy (XAS). Ti-containing MCM-41, as well as the Fe-, V- and Cr-containing variants, yield self-consistent, XAS-based, structural data of the respective metal-ion sites. Some of these (especially those containing Ti) are exceptionally good catalysts for the selective oxidation of large organic molecules such as limonene and norbornene.     

X-ray absorption studies of the electronic structure of nickel-copper catalysts

X-ray absorption threshold resonances associated with L_III and L_II absorption edges, which are attributed to excitation of electrons from 2p core levels to unoccupied d-states in the valence band, were investigated for a series of nickel-copper alloys of widely differing compositions. The catalysts were alloys in the form of metal powders with surface areas of the order of 1 m²/g. When the resonances for such samples are determined from measurements of the intensity of emission of electrons from the samples (i.e. by the so-called electron yield detection method), one can avoid experimental artifacts arising from the sample thickness effect encountered in X-ray transmission or fluorescence measurements. Edge resonances can then be determined reliably for metal powders. It was observed that copper had only a small attenuating effect on the resonances of nickel in the catalysts. The effect was smaller by an order of magnitude than that predicted by the rigid-band model of the electronic structure of nickel-copper alloys. The results provide strong support for earlier conclusions of others about the limitations of the rigid-band model.     

复肥生产过程中缩二脲的生成研究

采用国家化工行业标准(HG 2095-91) - 涂层尿素中缩二脲含量的测定方法系统研究了复混肥生产过程中缩二脲的生成,通过实验研究分析发现,在影响缩二脲生成率的4个因素:物料加热温度、加热时间、物料中水份含量、物料中尿素的质量分数中,影响最显著的是尿素的质量分数.     

X-ray absorption spectroscopy studies of nickel oxide thin film electrodes for supercapacitors

Nickel oxide films were synthesized by electrochemical precipitation of Ni(OH)₂ followed by heat-treatment in air at various temperatures (200-600 °C). Their structure and electrochemical properties were studied by cyclic voltammetry, X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). XRD results showed that the nickel oxide obtained at 250 °C or above has a crystalline NiO structure. The specific capacitance of the oxide depends on the heat-treatment temperature, showing a maximum value at 300 °C. XAS results revealed that the non-stoichiometric nickel oxide (Ni_1−xO) approached the stoichiometric NiO structure with increasing heat-treatment temperature due to the defect healing effect. The defective nature of the nickel oxide could be utilized to improve its specific capacitance for supercapacitor application.     

In situ hypochlorous acid generation for the treatment of textile wastewater

An electrolytic process based on chlorine generation was adopted to treat wastewater containing textile dyes. In situ production of hypochlorous acid was achieved in an undivided electrolytic cell. The cell contained a graphite rod as the anode and a stainless steel sheet as the cathode. The generated chlorine reacts with water leading to the formation of hypochlorous acid and hydrochloric acid. The resultant hypochlorous acid, being an oxidising agent, oxidises the organic components present in the textile wastewater. In this study, the colour in wastewater containing Procion Navy and Procion Red dyes, respectively, was completely removed after 40 min of electrolysis at a constant current density of 39 mA/cm² (where the initial dye concentrations were 3700 and 3200 mg/l, respectively). In the case of the Procion Yellow and composite dyes, complete colour removal occurred after 50 min of electrolysis (with initial dye concentrations of 3500 mg/l). Even though colour removal occurred during the electrolysis process, it required up to 180 min of electrolysis to reduce the COD values for the four dyes (Procion Navy, Red, Yellow and the composite) from the initial levels of 4520, 4200, 4170 and 4283 mg/l to 70, 45, 39 and 52 mg/l, respectively. This clearly indicates that the process removes both colour and organic components present in textile wastewater.     

Basic sites on the surface of oxide catalysts responsible for oxidative methane coupling

The basic sites of various oxide catalysts for the oxidative dimerisation of methane were studied by FTIR spectroscopy of adsorbed molecular probes (chloroform and CO₂). The methods used are compared and the advantage of CO₂ as probe for specifying the basic sites is demonstrated. The strengths of the basic sites were seen to correlate with the spectral parameters of the surface carbonates. Differences in spectral responses of carbonates are attributed to the different states of oxygen participating in their formation. The concentration of the strongest sites was estimated. A study of the catalytic activity of this system indicates that the system's activity in oxidative methane coupling depends on the presence and concentration of strong basic sites on the catalyst surface.     

Near edge X-ray absorption fine structure spectroscopic and infrared reflection absorption spectroscopic studies of surface modification of poly(butylene terephthalate) induced by UV irradiation

Surface modification of poly(butylene terephthalate) (PBT) induced by ultraviolet (UV) irradiation was investigated using near edge X-ray absorption fine structure spectroscopy (NEXAFS) and infrared reflection absorption spectroscopy (IRAS). UV irradiation drastically altered carbon and oxygen K-edge NEXAFS spectra of PBT. NEXAFS spectra obtained after UV irradiation were compared with those of various molecules containing carbonyl, carboxylic, ester, and anhydride groups. UV-irradiated PBT surfaces had similar spectral features to pyromellitic dianhydride, which contains anhydride groups. IRAS spectra of PBT surfaces were also changed by UV irradiation. The changes indicate that UV irradiation destroyed alkyl chains and changed the ester bond structure. These results indicate that UV irradiation removes alkyl chains and ester bonds in PBT and forms anhydride groups on PBT surfaces. It was also suggested that anhydrides might be formed near PBT surfaces by UV irradiation.     

干吸塔分酸装置的改造

介绍阳极保护分酸装置的结构和使用效果．分配装置由304L和316L不锈钢制作,分酸点密度为41个／m^2.将分酸装置的全部金属表面作为阳极,在进酸管和分酸槽中设置阴极,对分酸装置实行阳极保护,使用效果优于原铸铁槽式分酸器.