树脂移动床工艺在己二酸催化剂回收中的应用

阐述了硝酸氧化法生产己二酸的过程中两种不同的催化剂回收工艺的异同点。指出移动床离子交换工艺相对固定床离子交换工艺的优越性及推广价值。     

模拟酸雨对荔枝果园土壤磷素等温吸附与解吸特性的影响

采用等温吸附试验方法研究了模拟酸雨对荔枝果园土壤磷的吸附与解吸特性的影响。试验结果表明,不同处理间土壤对磷的最大吸附量(Xm)为pH2.5>pH4.5>CK=pH6.5,其中pH2.5的酸雨淋溶处理对磷的最大吸附量(Xm)与其它处理间差异显著;土壤吸附磷的解吸量(Xd)分别与相应的吸附量(X)和原平衡溶液浓度(C)呈显著的指数相关和线性相关,随着土壤对吸附量的增加,土壤磷的解吸量呈指数增长。     

Potential recoverable natural gas resources in China

Carbon nanosheet films were deposited on Al substrates by using plasma assisted chemical vapor deposition (PACVD) technique. And after being peeled off from Al substrates, carbon nanosheet powders (CNSPs) were obtained. In Raman spectrum of carbon film, there was a strong and broadened peak at about 1,580 cm-1, indicating a carbon diamond-like film. Atomic force microscope image showed that the carbon diamond-like film had a grain size less than 100 nm, and its surface roughness Ra was 17.95 nm in an area of 5×5 μm2. The CNSPs were irregular sheets with curly edges and a length of several micrometers to several hundreds of micrometers. The BET surface area of CNSPs was 6.66 m2/g with no micro-pore present, which was confirmed by N2 adsorption-desorption characterization. In the adsorption testing, when the relative pressure P/P0 was higher than 0.3, the adsorption behavior did not follow the Langmuir equation. The addition of CNSPs to carbon black (catalyst support) could improve hydrodesuifurization performance of carbon supported Ni-W catalysts for diesel oil.     

Adsorption and desorption behaviour of Pb(II) on a natural kaolin: equilibrium,kinetic and thermodynamic studies

BACKGROUND: Pb(II) is common in both waste‐waters and gas emissions. In developing countries, public health problems have been reported concerning Pb(II) pollution, so that stringent measures are required to deal with it. MAJOR RESULTS: The adsorption and desorption behaviour of Pb(II) has been investigated on a natural Chinese kaolin. Several factors, including initial concentration, pH, equilibration time, dosage and temperature correlated positively with Pb(II) adsorption. The Pb(II) adsorption capacity of natural kaolin was 165.117 mg g^?1. A kinetic study shows that Pb(II) adsorption on purified kaolin equilibrates within 35 min. The enthalpy changes of Pb(II) adsorption on purified kaolin were 63.683, 20.488 and 21.371 kJ mol^?1 with entropy changes 262.250, 112.210 and 105.120 J mol^?1 K^?1 for solutions containing 50, 100 and 200 mg L^?1 Pb(II) respectively, indicating an endothermic and spontaneous adsorption process. The desorption of Pb(II) from kaolin was difficult with more than 85% Pb(II) removal. Based on X‐ray diffraction (XRD) analysis, the Pb(II) adsorption on natural and purified kaolin was attributed mainly to the magnesite component and complexation with the mineral surface. CONCLUSIONS: Natural kaolin exhibits a satisfactory performance for adsorption of Pb(II) from aqueous solution. The optimum conditions for adsorption were: ionic strength = 0.01 mol L^?1; pH ≥ 7.2; dosage = 10 g L^?1; temperature = 25 °C; duration ≥ 16 h (C_i = 80 mg L^?1); and the optimum conditions for desorption were ionic strength = 0.1 mol L^?1 and pH ≤ 5.0. Copyright © 2009 Society of Chemical Industry     

Thermal characterisation of polymeric systems by mass spectrometry

The utility of mass spectrometry as a technique for the characterisation of polymeric formulations is discussed in general terms. The use of thermal techniques in which sufficient energy is given to the system to liberate volatile components of the formulation and, in some cases, to induce small amounts of polymer degradation, is described. Results obtained using this technique for a variety of polymer systems are discussed and the advantages of using this approach outlined. Recent developments in field desorption-mass spectrometry for the direct characterisation of modern polymer systems are discussed and some early results presented.     

Coke deposition mechanism on the pores of a commercial Pt-Re/γ-Al2O3 naphtha reforming catalyst

Coke deposition mechanism on a commercial Pt-Re/γ-Al₂O₃ naphtha reforming catalyst was studied. A used catalyst that was in industrial reforming operation for 28 months, as well as the fresh catalyst of the unit were characterized using XRD, XRF, and nitrogen adsorption/desorption analyses. Carbon and sulfur contents of the fresh and the used catalysts were determined using Leco combustion analyzer. The pore size distributions (PSD) of the fresh and the used reforming catalysts were determined using BJH and Comparison Plot methods. The Comparison Plot method produced the most reasonable PSDs for the catalysts. Through comparison of the PSDs of the fresh and the used catalysts, it was revealed that coke deposited on both micropores and mesopores of the catalyst at a constant thickness of 1.0 nm. The constant coke thickness on the catalyst pore walls in the naphtha reforming process (temp. ∼ 500 °C) implies that coke deposition reaction is the slow controlling step in comparison to the fast mass transfer rate of coke ingredients into the pores. The bulk density of the deposited coke on the used catalyst was calculated as 0.966 g/cm³.     

Electrochemical surface nanopatterning by selective reductive desorption from mixed metal surfaces

We report on a novel strategy to the functionalisation of electrode surfaces based on the preparation and patterning of mixed metal electrodes using metal selective electrodesorption of a sacrificial alkanethiol. Plain palladium (Pd) and plain polycrystalline gold (poly-Au) electrodes were used initially to determine metal specific potential windows within which electrodesorption of the short alkanethiol mercaptoethanol could be achieved. We found that stripping of mercaptoethanol from gold was achieved at potentials lower than −0.800 V, whilst stripping from palladium was achieved at more positive potentials i.e. around −0.650 V. Mixed metal electrodes were prepared by electroplating for short period of times palladium onto poly-Au electrodes. The resulting surfaces were characterised electrochemically in 1 M H₂SO₄ and clearly exhibited reduction peaks for both gold and palladium oxide formation. The mixed metal electrodes were coated with mercaptoethanol, which was further selectively removed from Pd by cyclic voltammetry in NaOH in the Pd-specific potential window. The presence of bare Pd domains revealed following electrodesorption was confirmed by subsequently adsorbing the electroactive alkanethiol 6-ferrocenylhexanethiol onto the freshly revealed Pd. Cyclic voltamogramms exhibited sharp redox peaks that could only be attributed to the successful immobilisation of 6-ferrocenylhexanethiol onto fresh Pd domains. Control surfaces, i.e. MCE fully coated Pd/Poly-Au electrode, exposed to 6-ferrocenylhexanethiol did not exhibit significant voltammetric features, attesting to the efficient patterning of the mixed metal electrode by employing metal specific reductive desorption of short alkanethiols. The possibility to pattern electrode surfaces in such way will find application in the field of diagnostics, and also in heterogeneous catalysis where Pd-Au alloys have received an increased interest in the recent years.     

MOISTURE SORPTION CHARACTERISTICS OF STARCH MATERIALS

ABSTRACT

An understanding of the sorptional equilibrium of food systems is an important objective in food engineering. In particular, a knowledge of the equilibrium characteristics of foodstuffs is an essential prerequisite for interpretation of the mass transport phenomena during drying. The equilibrium moisture content of a food system is developed as a result of the interaction between the material and the environment. A standard static gravimetric technique was adopted to evaluate the moisture sorption characteristics of the model food gels. The high-starch systems displayed Type II isotherm characteristics, while the high-sugar systems presented Type III behaviour. Adequate quantitative evaluation of the sorption characteristics was realized on the basis of the Guggenheim-Anderson-de Boer model.     

Formation of Nd2Fe14B hydride by milling of anhydride particles in toluene in a closed reactor

When milling micrometer thin Nd₂Fe₁₄B platelets, of an average 1–2 mm diameter, in toluene in a closed reactor, part of the toluene decomposes at the surface of the platelets and yields nascent hydrogen and carbon/low hydrocarbons. The hydrogen diffuses into the Nd₂Fe₁₄B platelets and the carbon forms a thin surface passivation layer of the platelets, forming the stable Nd₂Fe₁₄BH _x ,x ≤ 5, hydride at room temperature. On heating in a calorimeter, the hydrogen desorbs off the sample with a well-defined endotherm between 370 and 425 K. An N₂ gas atmosphere, if used during the heating, facilitates the H-desorption process with the modified kinetic parameters. For example, the enthalpy of the H-desorption ΔH and the related activation energyE _a have the measured values ΔH = 153 J/g andE _a = 58·2 kJ/mol in argon and ΔH = 256 J/g andE _a = 41·6 kJ/mol in N₂. It is argued that N₂ gas has a fast reaction with the H atoms desorbing off the thin sample platelets and forms NH₃ gas with an instantaneous decrease of the total external gas pressure at the sample. This supports the fast desorption of H atoms in the sample with the modified desorption kinetics in N₂ gas.