Improving the robustness of a partial least squares (PLS) model based on pure component selectivity analysis and range optimization: case study for the analysis of an etching solution containing hydrogen peroxide

Pure component selectivity analysis (PCSA) was successfully utilized to enhance the robustness of a partial least squares (PLS) model by examining the selectivity of a given component to other components. The samples used in this study were composed of NH₄OH, H₂O₂ and H₂O, a popular etchant solution in the electronic industry. Corresponding near-infrared (NIR) spectra (9000-7500 cm⁻¹) were used to build PLS models. The selective determination of H₂O₂ without influences from NH₄OH and H₂O was a key issue since its molecular structure is similar to that of H₂O and NH₄OH also has a hydroxyl functional group. The best spectral ranges for the determination of NH₄OH and H₂O₂ were found with the use of moving window PLS (MW-PLS) and corresponding selectivity was examined by pure component selectivity analysis. The PLS calibration for NH₄OH was free from interferences from the other components due to the presence of its unique NH absorption bands. Since the spectral variation from H₂O₂ was broadly overlapping and much less distinct than that from NH₄OH, the selectivity and prediction performance for the H₂O₂ calibration were sensitively varied depending on the spectral ranges and number of factors used. PCSA, based on the comparison between regression vectors from PLS and the net analyte signal (NAS), was an effective method to prevent over-fitting of the H₂O₂ calibration. A robust H₂O₂ calibration model with minimal interferences from other components was developed. PCSA should be included as a standard method in PLS calibrations where prediction error only is the usual measure of performance.     

On the nature of oxygen particles in the low-temperature desorption from vanadium oxides

The nature of oxygen particles produced in low-temperature desorption from V₂O₅ and V₂O₅ · MoO₃ was studied. It was found that there was no low-temperature desorption from samples in the presence of a quartz trap cooled to −195°C, which was evidence of the absence of possible desorption of O₃ and the presence of ¹Δ_g O₂. Under these conditions, the latter was frozen completely, and ozone was not.     

Characterization of phase transition of Ba2-xSrxIn2O5 by thermal analysis and high temperature X-ray diffraction

The phase transitions of Ba_2-xSr_xIn₂O₅ were investigated with various thermal analyses and high-temperature X-ray diffraction. It was clarified that crystal structure of Ba_2-xSr_xIn₂O₅ with x=0.0~0.4 varies from brownmillerite through distorted perovskite to another distorted perovskite with increase of temperature. The phase transition from brownmillerite to distorted perovskite was revealed to be first order, whereas transition from distorted perovskite to another one was second order. The specimen with x≥0.5 showed only one first order phase transition from brownmillerite to distorted perovskite. The phase diagram of Ba_2-xSr_xIn₂O₅ was established and existence of tricritical point at ~1100°C with x=0.4~0.5 was suggested. This revised version was published online in August 2006 with corrections to the Cover Date.     

Cationic polymerization of α,β-disubstituted olefins. VI. Steric structure of poly(methyl propenyl ether) obtained by cationic catalysts

The steric structure of poly(methyl propenyl ether) obtained by cationic polymerization was studied by NMR spectra. From the analysis of β-methyl and α-methoxyal spectra, it was found that the tacticities of the α-carbon were different from those of the β-carbon in all polymers obtained. In the crystalline polymers obtained from the trans isomer by homogeneous catalysts, BF₃·O(C₂H₅)₂ or Al(C₂H₅)Cl₂, and from the cis isomer by a heterogeneous catalyst, Al₂(SO₄)₃–H₂SO₄ complex, the structure of polymers was threo-di-isotactic. Though the configurations of all α-carbons were isotactic, a small amount of syndiotactic structure was observed in the β-carbon. On the other hand, in the amorphous polymer obtained from cis isomer by the homogeneous catalyst, the configuration of the α-carbon was isotactic, but that of the β-carbon was atactic. These facts suggest that the type of opening of a monomeric double bond is complicated, or that carbon–carbon double bond in an incoming monomer rotates in the transition state. From these experimental results, a probability treatment was proposed from the diad tacticity of α,β-disubstituted polymers. It shows that the tacticity is decided by a polymerization mechanism different from that proposed by Bovey.     

Electrochemical study of butylate: application to the analysis of water

A biochemical gas-sensor (bio-sniffer) was constructed for convenient measurement of odourless hydrogen peroxide (H₂O₂) vapour, which is harmful to skin and mucous membranes. An enzyme-immobilized membrane was fabricated by spreading the mixture of catalase and photo-crosslinkable polymer on a dialysis membrane. An H₂O₂ biosensor was constructed by attaching this catalase-immobilized membrane to the sensitive top of a Clark-type oxygen electrode, and the oxygen generation from the decomposition of H₂O₂ catalysed by catalase was measured amperometrically. This biosensor was first applied to the measurement of H₂O₂ solution and was able to quantify the concentrations of H₂O₂ solution from 0.02 to 10.0?mmol?L^?1. Then, this biosensor was applied to gaseous phase as a bio-sniffer and was able to detect the odourless H₂O₂ vapour with the calibration range from 0.5 to 30?ppm, where the threshold limit value assigned by the American Conference of Governmental Industrial Hygienists (1?ppm) is covered.     

Enzymatic formation of unnatural novel polyketide scaffolds by plant-specific type III polyketide synthase

The catalytic potential of octaketide synthase (OKS), a plant-specific type III polyketide synthase (PKS) from Aloe arborescens, was investigated by phenylacetyl-CoA and benzoyl-CoA as starter substrates. As a result, a novel C₁₆ pentaketide coumarin was produced from phenylacetyl-CoA, whereas benzoyl-CoA was not a good substrate of OKS. Remarkably, a structure-guided OKS N222G mutant dramatically extended the product chain length to yield four novel polyketides including C₂₂ aromatic octaketides from the C₆-C₂ phenylacetyl starter, as well as a novel C₁₉ heptaketide benzophenone from the C₆-C₁ benzoyl starter.     

Study of the ethane oxidation reaction by the kinetic tracer method

The kinetics of ethane oxidation was studied at 320, 340, 353 and 380°C, mixture composition 2 C₂H₆ + 1 O₂, and total pressure 609 torr. It was found that at 320°C CH₂O and CH₃CHO were branching agents. A series of experiments was conducted on 2C₂H₆ + O₂ oxidation in the presence of 0.7% ¹⁴C-labeled ethylene. The ethylene oxide was found to form only from C₂H₄, formaldehyde formed from C₂H₄ and C₂H₆; and CH₃CHO, C₂H₅OH, and CH₃OH formed only from ethane. The formation rates of C₂H₄, C₂H₄O, and CH₂O were calculated by the kinetic tracer method. At 320°C the fraction of oxygen-containing products formed from C₂H₄ was 16–18%, and at 353 and 380°C it was 30–40%.     

Integration of Succinic Acid and Ethanol Production With Potential Application in a Corn or Barley Biorefinery

Production of succinic acid from glucose by Escherichia coli strain AFP184 was studied in a batch fermentor. The bases used for pH control included NaOH, KOH, NH₄OH, and Na₂CO₃. The yield of succinic acid without and with carbon dioxide supplied by an adjacent ethanol fermentor using either corn or barley as feedstock was examined. The carbon dioxide gas from the ethanol fermentor was sparged directly into the liquid media in the succinic acid fermentor without any pretreatment. Without the CO₂ supplement, the highest succinic acid yield was observed with Na₂CO₃, followed by NH₄OH, and lowest with the other two bases. When the CO₂ produced in the ethanol fermentation was sparged into the media in the succinic acid fermentor, no improvement of succinic acid yield was observed with Na₂CO₃. However, several-fold increases in succinic acid yield were observed with the other bases, with NH₄OH giving the highest yield increase. The yield of succinic acid with CO₂ supplement from the ethanol fermentor when NH₄OH was used for pH control was equal to that obtained when Na₂CO₃ was used, with or without CO₂ supplementation. The benefit of sparging CO₂ from ethanol fermentation on the yield of succinic acid demonstrated the feasibility of integration of succinic acid fermentation with ethanol fermentation in a biorefinery for production of fuels and industrial chemicals.     

BaFeO3-x与Cu-ZSM-5耦合催化剂的NOx储存还原性能

为替代传统的贵金属基NO_x储存还原（NSR）催化剂,本文设计并制备了不含贵金属的BaFeO_3-x+Cu-ZSM-5 耦合催化剂,用于催化消除稀燃发动机尾气中的NO_x. 在稀燃阶段,NO在BaFeO_3-x催化剂上发生了氧化和储存反应;在富燃阶段,从BaFeO_3-x催化剂中脱附出来未能消除的NO_x被置于其后的Cu-ZSM-5催化剂进一步催化消除. 实验结果表明,BaFeO_3-x+Cu-ZSM-5 耦合催化剂的工作温度窗口被拓宽到250-400 ℃,同时NO_x消除性能得到了显著提高：NO_x转化率最高可达98%,N₂选择性接近100%.     

Cation-exchange studies of yttrium(III) and its separation from various other elements

Summary Systematic studies are presented on the cation-exchange behaviour of yttrium on Dowex 50W-X8. HCl, HNO₃, H₂SO₄, NH₄Cl, NH₄NO₃, (NH₄)₂SO₄, CH₃COONH₄, NaCl, NaNO₃, malonic acid, tartaric acid and EDTA were used as eluting agents. Y was separated from a large variety of elements by selective elution or selective adsorption. Thus it was possible to separate it from many common ions such as alkalis, alkaline earths, Bi, Hg, V, Cd, U, In, Co, Ga, Zn, Sc, Fe, Al, Ni, and Ce by selective elution. It was separated from Ti, Zr, Hf, and Sb by selective sorption in citrate media and from Cr, Tl, Pb, and Th by gradient elution.     

Lignin-Derived Syringol and Acetosyringone from Palm Bunch Using Heterogeneous Oxidative Depolymerization over Mixed Metal Oxide Catalysts under Microwave Heating

Biomass valorization to building block chemicals in food and pharmaceutical industries has tremendously gained attention. To produce monophenolic compounds from palm empty fruit bunch (EFB), EFB was subjected to alkaline hydrothermal extraction using NaOH or K₂CO₃ as a promotor. Subsequently, EFB-derived lignin was subjected to an oxidative depolymerization using Cu(II) and Fe(III) mixed metal oxides catalyst supported on γ-Al₂O₃ or SiO₂ as the catalyst in the presence of hydrogen peroxide. The highest percentage of total phenolic compounds of 63.87 wt% was obtained from microwave-induced oxidative degradation of K₂CO₃ extracted lignin catalyzed by Cu-Fe/SiO₂ catalyst. Main products from the aforementioned condition included 27.29 wt% of 2,4-di-tert-butylphenol, 19.21 wt% of syringol, 9.36 wt% of acetosyringone, 3.69 wt% of acetovanillone, 2.16 wt% of syringaldehyde, and 2.16 wt% of vanillin. Although the total phenolic compound from Cu-Fe/Al₂O₃ catalyst was lower (49.52 wt%) compared with that from Cu-Fe/SiO₂ catalyst (63.87 wt%), Cu-Fe/Al₂O₃ catalyst provided the greater selectivity of main two value-added products, syringol and acetosyrigone, at 54.64% and 23.65%, respectively (78.29% total selectivity of two products) from the NaOH extracted lignin. The findings suggested a promising method for syringol and acetosyringone production from the oxidative heterogeneous lignin depolymerization under low power intensity microwave heating within a short reaction time of 30 min.     

Continuous thermoanalysis: the essence of the method and equipment

Phase transition of the water-sodium poly(styrenesulfonate)(NaPSS) system with various water contents (W_c) ranging from 0 to 2.00 (g/g) was evaluated by differential scanning calorimetry (DSC). In the temperatures from 120 to 320K, four kinds of transitions were observed for the water-NaPSS system quenching from 320K to 120K. They were glass transition, cold-crystallization, melting, and a new transition which was considered to be that from the meso-phase to the isotropic liquid phase. From the DSC data, the phase diagram of the water-NaPSS system was obtained. At the same time, W_c was related to the weight of water calculated from the enthalpy of melting (W_f). By the subtraction of W_f from W_c, the amount of non-freezing water was calculated to be 0.57–0.68 (g/g) depending on molecular weight of NaPSS.     

Investigation of Electron Behavior in Nano‐TiO2 Photocatalysis by Using In Situ Open‐Circuit Voltage and Photoconductivity Measurements

The in situ open‐circuit voltages (V_oc) and the in situ photoconductivities have been measured to study electron behavior in photocatalysis and its effect on the photocatalytic oxidation of methanol. It was observed that electron injection to the conduction band (CB) of TiO₂ under light illumination during photocatalysis includes two sources: from the valence band (VB) of TiO₂ and from the methanol molecule. The electron injection from methanol to TiO₂ is slower than that directly from the VB, which indicates that the adsorption mode of methanol on the TiO₂ surface can change between dark and illuminated states. The electron injection from methanol to the CB of TiO₂ leads to the upshift of the Fermi level of electrons in TiO₂, which is the thermodynamic driving force of photocatalytic oxidation. It was also found that the charge state of nano‐TiO₂ is continuously changing during photocatalysis as electrons are injected from methanol to TiO₂. Combined with the apparent Langmuir–Hinshelwood kinetic model, the relation between photocatalytic kinetics and electrons in the TiO₂ CB was developed and verified experimentally. The photocatalytic rate constant is the variation of the Fermi level with time, based on which a new method was developed to calculate the photocatalytic kinetic rate constant by monitoring the change of V_oc with time during photocatalysis.     

Preparation and catalytic activity for ammonia synthesis of several ruthenium supported catalysts

Ruthenium supported catalysts were prepared from RuCl₃ · 3H₂O and K₄[Ru(CN)₆] · 3 H₂O solutions, upon several acid/base pretreated γ-Al₂O₃ samples, using water and acetone as solvents. Metallic adsorption was found to be dependent on solvent and precursor used. An increasing final ruthenium content of the catalysts with increasing acid site content of the support is observed, when K₄[Ru(CN)₆] · 3 H₂ is used as a precursor. The catalytic activity was followed at atmospheric pressure and 593 K (N₂/H₂ = 1/3). Catalysts prepared from K₄[Ru(CN)₆] · 3 H₂O were about ten fold more active than those prepared from RuCl₃ · 3 H₂O. The catalytic activity of catalysts prepared from K₄[Ru(CN)₆] · 3 H₂O was found to be sensitive to the acid-pretreatment of γ-Al₂O₃, while the activity of those prepared from RuCl₃ · 3 H₂O was not sensitive to the pretreatment of the support.     

Insights into photoluminescence property and photocatalytic activity of cubic and rhombohedral ZnIn2S4

Cubic and rhombohedral ZnIn₂S₄ were synthesized by thermal sulfidation of Zn-In mixed oxide precursor in H₂S atmosphere at different temperatures. Cubic ZnIn₂S₄ was obtained when Zn-In mixed oxide precursor was sulfurized at 400 °C. With sulfidation temperature increasing from 400 to 800 °C, the crystal phase of ZnIn₂S₄ gradually turned from cubic to rhombohedral, which was demonstrated by different analysis techniques such as XRD, Raman, SEM, etc. UV-vis absorption spectra indicated that cubic ZnIn₂S₄ displayed better light absorption property than rhombohedral ZnIn₂S₄, with band gaps calculated to be 2.0 and 2.5 eV, respectively. However, under visible light irradiation, rhombohedral ZnIn₂S₄ photocatalyzed H₂ evolution from aqueous sodium sulfite/sulfide solution efficiently, whereas cubic ZnIn₂S₄ was not active for this reaction. The photoluminescence property revealed the different dynamics of photogenerated carriers, which made a predominant contribution to the increasing photocatalytic performances of ZnIn₂S₄ with crystal phase turning from cubic to rhombohedral.     

Quantitative trace analysis of fullerenes in river sediment from Spain and soils from Saudi Arabia

A quantitative method based on ultrasound-assisted toluene extraction followed by liquid chromatography–electrospray ionization–tandem mass spectrometry for the analysis of C₆₀ and C₇₀ fullerenes, N-methylfulleropyrrolidine, [6, 6]-phenyl C₆₁ butyric acid methyl ester and [6, 6]-thienyl C₆₁ butyric acid methyl ester has been developed. The method was validated using fortified blank river sediments according to the criteria of Commission Decision 2002/657/EC. The method limits of detection ranged from 14 to 290 pg/g, making it suitable for its application in environmental analysis. The method has been applied to investigate fullerene content in 58 soil samples collected from different urban and industrial areas in Saudi Arabia and in river sediment from six different sites in the Llobregat River Basin. In addition, in the case of the Llobregat River, superficial water samples from the same sites of the sediments were collected and analysed using a previous method. In soils from Saudi Arabia, C₆₀-fullerene was the only compound that was detected and quantified in 19 % of samples. In the sediments of the Llobregat River, C₆₀-fullerene was also the only one detected (33 % of the samples), while in river water, C₇₀-fullerene was the most frequent compound, and it was quantified in 67 % of the samples. However, C₆₀-fullerene was present in two of the six samples, but at higher concentrations than C₇₀-fullerene, ranging from 0.9 to 7.8 ng/L.     

Electrodeposition of Al,Zn, and Pt on silver-coated textile fibres from ionic liquids

In the present paper, we report on the electrodeposition of aluminium, zinc and platinum on silver-coated textile fibres from ionic liquids. For electrodeposition of Al, the 60:40 mol% mixture of AlCl₃/1-ethyl-3-methylimidazolium chloride ([EMIm]Cl) and 1.7 M AlCl₃ in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py_1,4]TFSA) were employed. It was observed that microcrystalline aluminium was electrodeposited on the textile fibres in 60:40 mol% AlCl₃/[EMIm]Cl. The deposited Al layers either on single fibres or on textile assemblies are well adherent and uniform. An adherent, homogeneous and nanocrystalline Al layer was obtained on the silver-coated textile samples from 1.7 M AlCl₃/[Py_1,4]TFSA at 75 °C. The obtained Al layers from 60:40 mol% AlCl₃/[EMIm]Cl on the textile fibres exhibit a good corrosion resistance in an aqueous iodide/iodine electrolyte. Furthermore, we obtain Al microtubes from the investigated ionic liquids after dissolving the textile fibres. In addition, zinc electrodeposition was carried out on the textile samples from 60:40 mol% ZnCl₂/[EMIm]Cl at 80 °C. The electrodeposition of platinum on the textiles was done from 50 mM PtCl₂ in 1-butyl-1-methylpyrrolidinium dicyanamide ([Py_1,4]DCA).     

Brominated Methanes as Photoresponsive Molecular Storage of Elemental Br2

The photochemical generation of elemental Br₂ from brominated methanes is reported. Br₂ was generated by the vaporization of carbon oxides and HBr through oxidative photodecomposition of brominated methanes under a 20 W low‐pressure mercury lamp, wherein the amount and situations of Br₂ generation were photochemically controllable. Liquid CH₂Br₂ can be used not only as an organic solvent but also for the photoresponsive molecular storage of Br₂, which is of great technical benefit in a variety of organic syntheses and in materials science. By taking advantage of the in situ generation of Br₂ from the organic solvent itself, many organobromine compounds were synthesized in high practical yields with or without the addition of a catalyst. Herein, Br₂ that was generated by the photodecomposition of CH₂Br₂ retained its reactivity in solution to undergo essentially the same reactions as those that were carried out with solutions of Br₂ dissolved in CH₂Br₂ that were prepared without photoirradiation. Furthermore, HBr, which was generated during the course of the photodecomposition of CH₂Br₂, was also available for the substitution of the OH group for the Br group and for the preparation of the HBr salts of amines. Furthermore, the photochemical generation of Br₂ from CH₂Br₂ was available for the area‐selective photochemical bleaching of natural colored plants, such as red rose petals, wherein Br₂ that was generated photochemically from CH₂Br₂ was painted onto the petal to cause radical oxidations of the chromophoric anthocyanin molecules.     

Microencapsulation technology for thiourea corrosion inhibitor

The microencapsulation technology was brought in to solidify corrosion inhibitor in order to prolong the releasing time of it. In this work, thiourea (H₂NCSNH₂) was used as a corrosion inhibitor and microcapsuled using glutin and polyvinyl alcohol (PVA), respectively, as protective agent. The re-sealing process was used as a way to prolong the releasing time of the H₂NCSNH₂ encapsulated in microcapsules. It was found that the H₂NCSNH₂ microcapsule corrosion inhibitor using PVA as a protective agent had a better releasing time. The releasing times of the H₂NCSNH₂ microcapsule corrosion inhibitors were prolonged from 18 to 48 h by re-sealing process and using PVA as a protective agent. Both the use of PVA as a protective agent and the application of the re-sealing process decreased the encapsulation efficiency of the H₂NCSNH₂. The performance parameters on protecting Q235 carbon steel from corrosion in 0.1-M H₂SO₄ solution were evaluated by polarization curve and electrochemical impedance spectra methods. The results showed that the H₂NCSNH₂ released into the solution from microcapsules could well protect Q235 carbon steel from corrosion and the corrosion-inhibiting mechanisms of it were the same as that of H₂NCSNH₂.     

Synthesis of dimethyl ether from methane mediated by HBr (Special column of methane transformation, Article)

Dimethyl ether (DME) was synthesized from methane through a two-step process, in which CH₃Br was prepared from the oxidative bromination reaction of methane in the presence of HBr and oxygen over a Rh-SiO₂ catalyst and then, in the second step, CH₃Br was hydrolyzed to DME over a silica supported metal chloride catalyst. 12 mol%ZnCl₂/SiO₂ catalyst was found to be the most active, but it deactivated because of Cl⁻ losing.