Accommodation of impurities in α-Al2O3, α-Cr2O3 and α-Fe2O3

Atomic scale computer simulation was used to predict the mechanisms and energies associated with the accommodation of aliovalent and isovalent dopants in three host oxides with the corundum structure. Here we consider a much more extensive range of dopant ions than has previously been the case. This enables a rigorous comparison of calculated mechanism energetics. From this we predict that divalent ions are charge compensated by oxygen vacancies and tetravalent ions by cation vacancies over the full range of dopant radii. When defect associations are included in the model these conclusions remain valid. At equilibrium, defects resulting from extrinsic dopant solution dominate intrinsic processes, except for the largest dopant cations. Solution reaction energies increase markedly with increasing dopant radius. The behaviour of cluster binding energies is more complex.     

Electrochemical storage of polypyrrole-Fe2O3 nanocomposites in ionic liquids

Electroactive polypyrrole-Fe₂O₃ nanocomposite materials were prepared by chemical polymerization of pyrrole in aqueous Fe₂O₃ colloidal solution, using FeCl₃ as oxidant and tosylate anions (TS) as doping agent. The nanocomposite material named (PPyTSNC) was studied by X-ray diffraction analysis, Fourier Transform Infra-Red spectroscopy and thermogravimetric analysis. Their electrochemical storage properties were investigated on composite electrodes using 80% in weight of active materials in different immidazolium and pyrrolidinium based room temperature ionic liquids (RTILs) as electrolytes. Cyclic voltammetry and constant current charge discharge cycling showed high charge storage properties of the nanocomposite based electrodes in 1-ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide (EMITFSI) and N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR₁₄TFSI) (respectively 72 mAh/g and 62 mAh/g at 1 mA/cm² discharge current) which are more than twice higher than the values obtained with pure PPy. These improvements in capacities have been attributed to the PPyTSNC morphology modification which ensures a large incorporation of the electrolyte inside the nanostructure. The specific capacitances of the nanocomposite electrodes reached 210 F/g and 190 F/g in EMITFSI and PYR₁₄TFSI and their cyclability has shown only 3-5% capacitance loss after one thousand cycles for both ionic liquids.     

碱性离子液体-NaOH/MEA混合体系的CO2吸收性能

为了改善有机醇胺与无机碱液对生物质燃气中CO2的吸收性能,制备了具有代表性的4种功能化离子液体:[TMG]+ [C3H4N2]-、[TMG]+[TFEA]-、[MEA]+[BF4]-、[MEA]+[CHOO]-,并按一定的比例分别与NaOH溶液和乙醇胺(MEA)溶液复配组成新型CO2吸收剂,以研究其对CO2的吸收特性.实验结果显示,MEA-[TMG]+[C3H4N2]-、MEA-[MEA]+[CHOO]-和NaOH-[MEA]+[CHOO]-对CO2的吸收去除率高于单纯的MEA和NaOH溶液,而MEA-[TMG]+[TFEA]-、MEA-[MEA]+[BF4]-和NaOH-[MEA]+[BF4]-对CO2的去除率则低于单纯碱液吸收剂.同时发现,当离子液体[MEA]+[CHOO]-与MEA的混合比例为2∶3时,混合溶剂对CO2的吸收效果比MEA溶液的显著提高,生物质燃气中CO2去除率从91.3％增加至95.7％.     

胺功能化MIL-101(Cr)@SiO_2@Fe_3O_4催化剂及其Knoevenagel反应性能

采用溶剂热法在纳米SiO_2@Fe_3O_4磁性颗粒表面原位合成MIL-101(Cr),制备磁性MIL-101(Cr)@SiO_2@Fe_3O_4催化剂。采用甲胺、乙二胺和丁二胺对制备的磁性催化剂进行功能化,得到胺功能化NH2-MIL-101(Cr)@SiO_2@Fe_3O_4催化剂。利用XRD、FT-IR、BET、SEM、TEM和VSM等对催化剂结构进行表征,评价胺功能化NH2-MIL-101(Cr)@SiO_2@Fe_3O_4催化剂对糠醛和氰乙酸乙酯Knoevenagel缩合反应性能和重复使用性能,考察反应条件与催化性能的关系。结果表明,制备的新型胺功能化NH2-MIL-101(Cr)@SiO_2@Fe_3O_4催化剂具有MIL-101(Cr)的结构特征和良好的超顺磁性能,对糠醛和氰乙酸乙酯Knoevenagel缩合反应表现出很好的催化性能,其中,乙二胺功能化30%MIL-101(Cr)@SiO_2@Fe_3O_4催化剂对Knoevenagel缩合反应的性能最佳,在反应温度40℃和反应时间1 h条件下,氰乙酸乙酯转化率为97. 0%,产物选择性接近100%。反应后磁性催化剂可以通过外磁场容易进行分离,重复使用5次,氰乙酸乙酯转化率仍大于93%。     

High pressure CO2 solubility in N-methyl-2-hydroxyethylammonium protic ionic liquids

The use of ionic liquids for CO₂ capture and natural gas sweetening is being object of intense research. Within the enormous group of existing ionic liquids, those based on conjugate bases of carboxylic acids seem to be particularly promising. This work addresses the study of the high pressure CO₂ solubility (up to 80 MPa) in two protic ionic liquids, N-methyl-2-hydroxyethylammonium formate and N-methyl-2-hydroxyethylammonium acetate, in a wide range of temperatures (293-353 K). A thermodynamic model based on the Peng-Robinson equation of state with the Wong-Sandler mixing rule, using the NRTL model for the activity coefficients, was here adopted to describe and evaluate the thermodynamic consistency of the experimental data. Furthermore, the study of a ternary mixture of CO₂ + CH₄ + N-methyl-2-hydroxyethylammonium acetate was investigated showing a high selectivity from the IL towards these solutes.     

MDEA-二元羧酸离子液体溶液吸收/解吸SO2性能

设计合成了三类N-甲基二乙醇胺（MDEA）-二元羧酸离子液体水溶液,研究了它们的物理性质和SO₂吸收容量。结果表明：MDEA/有机酸的摩尔比及阴离子种类是影响吸收容量的主要原因。碱酸摩尔比越高,离子液体吸收能力越强,解吸能力越差且解吸时间也越长。此外,不同阴离子的离子液体溶液吸收SO₂的容量有如下关系：MDEA-丁二酸>MDEA-戊二酸>MDEA-苹果酸。对于MDEA-戊二酸和MDEA-苹果酸离子液体溶液,最具工业化应用前景的碱酸摩尔比分别为1.2：1和1.4：1。     

Surface modification of γ-Fe2O3 nanoparticles with aminopropylsilyl groups and interparticle linkage with α,ω-dicarboxylic acids

An investigation was carried out on the surface modification of γ-Fe₂O₃ nanoparticles with aminopropylsilyl (APS) groups in 3-aminopropyltriethoxysilane and the interparticle linkage with α,ω-dicarboxylic acids (succinic acid and suberic acid) through the terminal amino groups of APS moiety at the surface of γ-Fe₂O₃ nanoparticles. It was demonstrated that the change in interparticle distance caused by these surface modifications influences the magnetic property of the composites. When γ-Fe₂O₃ nanoparticles were modified with APS groups, coercivity increased and when they were further modified with α,ω-dicarboxylic acids, the larger decrease in coercivity was observed with the longer dicarboxylic acid.     

离子液体/低共熔溶剂用于NH3分离过程的热力学分析

氨气（NH₃）作为一种有害气体,其传统吸收技术存在诸多缺陷,亟需开发性能优越的NH₃吸收剂,以开发新型NH₃分离技术。离子液体和低共熔溶剂作为气体分离过程的潜在吸收剂,因低挥发性、良好的热稳定性以及灵活的可调控性等特点受到越来越多的关注。但离子液体和低共熔溶剂数量众多,筛选困难。采用热力学分析方法分析离子液体和低共熔溶剂用于NH₃分离过程,基于Gibbs自由能变,拟合出分离过程的最佳操作条件,将总能耗和离子液体用量作为筛选标准,筛选出性能良好的[Omim][BF₄]。将[Omim][BF₄]与传统NH₃吸收剂水对比,发现[Omim][BF₄]具有更低的能耗。最后,拟合出筛选标准与离子液体/低共熔溶剂的临界性质间的规律,为开发新的NH₃吸收剂和新的分离技术提供依据。     

One-step synthesis of γ-Fe2O3 nanoparticles by laser ablation

A Nd:YAG pulsed laser was used to ablate a 0.5-mm-diameter iron wire in a sealed chamber in a mixed gas flux of N₂ and O₂ to generate pure γ-Fe₂O₃ nanoparticles at atmospheric pressure. Structural characteristics and sizes of the prepared nanoparticles were determined by X-ray diffraction and TEM. The effects of laser power density, total mixed gas pressure and the oxygen ratio on the mean particle size were investigated, respectively. The results showed that the mean particle size decreased with the increase of the laser power density, total gas pressure and the oxygen ratio, respectively. Besides, the nanoparticle formation mechanism by laser ablation of iron wires was also discussed.     

Designing of anion‐functionalized ionic liquids for efficient capture of SO2 from flue gas

Five kinds of anion‐functionalized ionic liquids (ILs) with different basicity and substituent were selected, prepared and applied in the capture of SO₂ from flue gas, where the concentration of SO₂ is only 2000 ppm. The effect of the anion on SO₂ absorption capacity, desorption residue, and available absorption capacity under 2000 ppm was investigated. The relationship between available absorption capacity and absorption enthalpy was also studied. Through a combination of thermodynamic analysis and quantum calculation, the results indicated that the effect of the cation in the IL on absorption enthalpy was significant. However, the effect of chain length in the cation was weak. Hence, a new IL with low molecular weight, [P₄₄₄₂][Tetz], was further designed and applied for the capture of SO₂, which shows the high absorption capacity of 0.18 g SO₂ per g IL and excellent reversibility for 2000 ppm SO₂. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2028–2034, 2015     

η-Al2O3与γ-Al2O3在CS2催化水解反应中的性能比较

通过制备高纯度的前驱体湃铝石获得了η-Al₂O₃材料,采用XRD验证了η-Al₂O₃与γ-Al₂O₃在晶相结构上的差异,比较了两者的表面形貌、织构及酸碱性能,结果显示,η-Al₂O₃与γ-Al₂O₃的比表面积相当,但η-Al₂O₃具有更弱的弱碱位和较少的强碱位,并拥有丰富的中等强度酸性位。将η-Al₂O₃与γ-Al₂O₃作为催化剂应用于CS₂水解反应,结果表明,在(200~450) ℃测试温度范围内,η-Al₂O₃催化剂对CS₂的水解活性始终优于γ-Al₂O₃,两种催化剂上CS₂反应的浓度效应也明显不同,推测与它们的酸碱性质影响了对CS₂的吸附能力有关,导致两者催化CS₂水解反应遵循了不同的机制。     

Effect of the hydrogen spillover on the selectivity of dibenzothiophene hydrodesulfurization over CoSx/γ-Al2O3, NiSx/γ-Al2O3 and MoS2/γ-Al2O3 catalysts

Dibenzothiophene (DBT) hydrodesulphurization (HDS) reaction at 3 MPa and 325–375 °C on Mo/γ-Al₂O₃ single-bed and Me/γ-Al₂O₃//SiO₂//Mo/γ-Al₂O₃ (Me = Co or Ni) double-bed catalysts were investigated. Results indicate that ratio cyclohexylbenzene (CHB)/biphenyl (BP) or selectivity is higher when using double-beds rather than a single-bed. Synergy in dibenzothiophene hydrodesulphurization on Co//Mo and Ni//Mo double-beds is also detected. Changes in selectivity and conversion are attributed to the action of spillover hydrogen (Hso) formed in the first bed that reaches the second bed.     

Hydrodeoxygenation of methyl esters on sulphided NiMo/γ-Al2O3 and CoMo/γ-Al2O3 catalysts

Wood-derived bio-oil contains high amounts of compounds with different oxygen-containing functional groups that must be removed to improve the fuel characteristics. Elimination of oxygen from carboxylic groups was studied with model compounds, methyl heptanoate and methyl hexanoate, on sulphided NiMo/γ-Al₂O₃ and CoMo/γ-Al₂O₃ catalysts in a flow reactor. Catalyst performances and reaction schemes were addressed. Aliphatic methyl esters produced hydrocarbons via three main paths: The first path gave alcohols followed by dehydration to hydrocarbons. Deesterification yielded an alcohol and a carboxylic acid in the second path. Carboxylic acid was further converted to hydrocarbons either directly or with an alcohol intermediate. Decarboxylation of the esters led to hydrocarbons in the third path. No oxygen-containing compounds were detected at complete conversions. However, the product distributions changed with time, even at complete conversions, indicating that both catalysts deactivated under the studied conditions.     

Mass‐transfer rate enhancement for CO2 separation by ionic liquids: Theoretical study on the mechanism

To promote the development of ionic liquid (IL) immobilized sorbents and supported IL membranes (SILMs) for CO₂ separation, the kinetics of CO₂ absorption/desorption in IL immobilized sorbents was studied using a novel method based on nonequilibrium thermodynamics. It shows that the apparent chemical‐potential‐based mass‐transfer coefficients of CO₂ were in three regions with three‐order difference in magnitude for the IL‐film thicknesses in microscale, 100 nm‐scale, and 10 nm‐scale. Using a diffusion‐reaction theory, it is found that by tailoring the IL‐film thickness from microscale to nanoscale, the process was altered from diffusion‐control to reaction‐control, revealing the inherent mechanism for the dramatic rate enhancement. The extension to SILMs shows that the significant improvement of CO₂ flux can be obtained theoretically for the membranes with nanoscale IL‐films, which makes it feasible to implement CO₂ separation by ILs with low investment cost. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4437–4444, 2015     

Sintering of α-Al2O3/quartz, and α-Al2O3/cristobalite related to mullite formation

Cristobalite and quartz react differently in mixtures with α-Al₂O₃ at 1415°C. With cristobalite, an eutectic liquid forms in accordance with the metastable phase equilibrium diagram for α-Al₂O₃-SiO₂ (cristobalite) in the absence of mullite. With quartz, a liquid first forms on the surfaces of quartz because of the occurence of an intermediate liquid phase on transformation of quartz to cristobalite. These liquids act as precursors to the formation of mullite by reacting with α-Al₂O₃. Mullite was detected earlier in the cristobalite-containing mixtures under similar firing conditions because the growth of mullite becomes significant with the formation of the eutectic liquid at the α-Al₂O₃-cristobalite interface since it is already saturated with Al₂O₃. The kinetics of sintering are affected by the rates of the step reactions.     

A comparison of sodium-modified Rh/γ-Al2O3 and Pd/γ-Al2O3 catalysts operated under simulated TWC conditions

Addition of Na to Rh/γ-Al₂O₃ and Pd/γ-Al₂O₃ catalysts operated under identical simulated TWC conditions has dramatically different effects in the two cases (although the two metals respond similarly to Na promotion of NO_x reduction in the absence of gaseous oxygen). Na addition to rhodium has a detrimental effect as manifested by severe poisoning and decreased nitrogen selectivity over the greater part of the temperature range studied. In contrast, Na promotion significantly improves the overall performance of Pd/γ-Al₂O₃ catalysts under simulated TWC conditions. This is manifested by a considerable widening of the gas composition window over which palladium delivers high NO_x conversion, whilst at the same time exhibiting markedly improved selectivity towards N₂ formation. The very different behaviour of the two metals may be understood in terms of a single underlying effect, namely, the electronic influence of sodium ions on the adsorption strength (and hence relative coverages) of the various reactants on the metal surface.     

Antimicrobial properties and thermal stability of polycarbonate modified with 1‐alkyl‐3‐methylimidazolium tetrafluoroborate ionic liquids

Four water immiscible ionic liquids (ILs): 1‐hexyl‐3‐methylimidazolium tetrafluoroborate, 1‐heptyl‐3‐methylimidazolium tetrafluoroborate, 1‐octyl‐3‐methylimidazolium tetrafluoroborate and 1‐dodecyl‐3‐methylimidazolium tetrafluoroborate have been synthesized. Polycarbonate (PC) films containing ILs were prepared by solvent casting from methylene chloride solutions. Scanning electron microscopy measurements showed the high homogeneity of PC/IL films with the IL content up to 4 wt %. The tendency to IL aggregation was observed for polymeric films with higher IL content (5%). PC/IL composites were found to have the reduced thermal decomposition temperature under both an air and a nitrogen atmosphere in comparison with the neat PC. The effect of IL content on the antimicrobial activity of PC films against Escherichia coli bacteria was studied. Pronounced antimicrobial efficacy was revealed for PC/IL films for all studied ILs starting from 3 wt % of IL. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40050.     

1‐Allyl‐3‐methylimidazolium halometallate ionic liquids as efficient catalysts for the glycolysis of poly(ethylene terephthalate)

Series of 1‐allyl‐3‐methylimidazolium halometallate ionic liquids (ILs) were synthesized and used to degrade poly(ethylene terephthalate) (PET) as catalysts in the solvent of ethylene glycol. One important feature of these new IL catalysts is that most of them, especially [amim][CoCl₃] and [amim][ZnCl₃], exhibit higher catalytic activity under mild reaction condition, compared to the traditional catalysts [e.g., Zn(Ac)₂], the conventional IL catalysts (e.g., [bmim]Cl), Fe‐containing magnetic IL catalysts (e.g., [bmim][FeCl₄]), and metallic acetate IL catalysts (e.g., [Deim][Zn(OAc)₃]). For example, using [amim][ZnCl₃] as catalyst, the conversion of PET and the selectivity of bis(hydroxyethyl) terephthalate (BHET) reach up to 100% and 80.1%, respectively, under atmospheric pressure at 175°C for only 1.25 h. Another important feature is that BHET can be easily separated from the catalyst and has a high purity. Finally, based on the experimental phenomena, in ‐situ infrared spectra, and experimental results, the possible mechanism of degradation with synthesized IL is proposed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Nanosized γ-Al2O3 protective film for fluorescent lamps

Nanosized γ-Al₂O₃ particles were prepared by the sol–gel method with aluminum ion hydrolysis control performed by nitric acid. The as-prepared particles were mixed with deionized-water and stabilizer, and cycled in a high speed sand mill to form a stable γ-Al₂O₃ suspended slurry, which was then coated on the surface of the glass substrate to form a γ-Al₂O₃ protective film. Observations of SEM and visible transmission spectra show that a well-dispersed γ-Al₂O₃ slurry could be obtained after three-cycle grinding suitable to coat fluorescent lamp glass with a dense and uniform film of visible light transmission up to 95%.