High-temperature Water–Gas Shift catalysts for hydrogen enrichment of a gas produced by biomass steam gasification

To improve the hydrogen content of a biomass steam gasification syngas, Water–Gas Shift Fe/CeO₂ catalysts supported on ceramic foams were developed. The impregnation of ceria as washcoat led to an increase in the support surface area (BET) and to the formation of well-dispersed iron particles (XRD and TPR) by iron oxide impregnation. Catalytic tests were performed at atmospheric pressure with minor pressure drops, under a gas mixture similar to that produced at the gasifier outlet. A satisfactory CO conversion and a large increase in H₂ content were reached by adjusting the operating parameters of the WGS and the catalysts’ composition. After-test characterizations indicated in situ catalysts activation with no over-reduction and a positive action of ceria on iron dispersion and sintering prevention.     

Activity coefficients of hydrocarbon solutes at infinite dilution in the ionic liquid, 1-methyl-3-octyl-imidazolium chloride from gas–liquid chromatography

Activity coefficients for hydrocarbon solutes at infinite dilution in 1-methyl-3-octyl-imidazolium chloride have been measured using the medium pressure gas–liquid chromatography method. The hydrocarbon solutes used were n-pentane, n-hexane, n-heptane, n-octane, 1-hexene, 1-heptene, 1-octene, 1-hexyne, 1-heptyne, 1-octyne, cyclopentane, cyclohexane, cycloheptane, benzene, and toluene. Activity coefficients at infinite dilution were determined at the following three temperatures (298.15, 308.15, and 318.15) K. Selectivities for benzene and the hydrocarbons are presented and the results indicate that 1-methyl-3-octyl-imidazolium chloride is a reasonable solvent for the separation of an alkane or an alkene from benzene.     

Preparation of modified γ-alumina as stationary phase in gas–solid chromatography and its separation performance for hydrogen isotopes

On the basis of impregnation method, several stationary phases were prepared using γ-Al₂O₃ with the solution of transition metal salts and the breakthrough curves of gas chromatograph for H₂ isotopes were analyzed under the temperature of liquid nitrogen. The effects of carrier gas, flow rate and doping concentration on the separation performance for H₂ and D₂ were systematically investigated. The overall results showed that the surface areas and adsorptive capacities of modified γ-Al₂O₃ were slightly lower than unmodified one while the separation performance and symmetry of chromatographic peaks of the former were more excellent. In addition, the chromatographic peaks of ortho- and para-H₂ were no longer separated and the retention time shortened to half on columns of modified γ-Al₂O₃. All the magnetic transition metal ions modified γ-Al₂O₃ did very well for the separation of H₂/D₂ under the conditions of neon as carrier gas with a flow rate of 60 mL/min and column lengths of 1.0 m and injection amounts of 0.1 mL. Especially, the MnCl₂ modified γ-Al₂O₃ exhibited the best performance for separating H₂/D₂ with an optimum doping concentration of 20 wt%.     

Ternary phase equilibria for the sodium chloride–sodium sulfate–water system at 200 and 250 bar up to 400°C

Phase equilibria in the NaCl–Na₂SO₄–H₂O system were investigated at 200 and 250 bar for total salt concentrations ranging from 5 to 20 wt.% total salt over temperatures ranging from 320 to 400°C. In addition to providing data for this ternary system, the experiments also added information on the phase behavior of the two binary systems: NaCl–H₂O and Na₂SO₄–H₂O. For salt mixture compositions which were rich in sodium sulfate, a solid phase was observed to nucleate from the homogeneous liquid phase. Salt mixture compositions which had a high fraction of sodium chloride exhibited a vapor separation from a homogeneous liquid phase. By fitting curves to the solid–liquid and vapor–liquid separation temperatures, the temperature and composition of a constrained invariant point where liquid, solid salt and vapor are in equilibrium were estimated. These estimates were performed at discrete compositions of 5, 10, 15 and 20 wt.% total salt at pressures of 200 and 250 bar. The temperature and composition of the invariant point increased with increasing pressure following a simple thermodynamic model for boiling point elevation in a nearly ideal solution.     

Excess molar heat capacity for the binary system n-propyl alcohol + water in the temperature range 278.15–358.15 K: new data and application for excess enthalpy calculation

Journal of Thermal Analysis and Calorimetry - In this work, the new set of the data on the excess heat capacity (CPE ), density (ρ) and excess volumes (VE) for binary system...     

Surface structure–activity relationships of Cu/ZnGaOX catalysts in low temperature water–gas shift (WGS) reaction for production of hydrogen fuel

A new species’ class of Cu-, Ga- and Zn-based rate catalysts was prepared by a systematic co-precipitation technique at the different related pH values (6.5–8.0) along with calcination functional conditions, influencing components’ physical properties, these were characterized, and their application performance for water–gas shift (WGS) reaction was researched. Substances were analysed by various experimental methods, namely chemisorption, temperature-programmed reduction (TPR) characterisation, diffraction, physisorption and microscopy. A homogenous size dispersion of the compounds with smaller granular particles was obtained for catalysis, implemented with high pH-resulting outputs. H₂ TPR profiles revealed a tailored stronger effect of Cu–Zn on Ga for process, operated with low pH-conditioned forms. Over Cu/ZnGaO_X, WGS was sensitive to Cu, which was primarily active. Catalytic chemical reactivity, activity and selectivity were also found to be critically dependent on material lattice structure, copper surface area and metal–support interaction phenomena. The temperature-programmed surface reaction with mass spectrometry (TPSR–MS) measurements showed that formulations, synthesised at the pH of 8.0, enabled reaching >99% of the equilibrium yield CO conversion at 260 °C. An increase in the converted CO, oxidation and H₂ productivity with the integral steam content in gaseous feed flow was achieved. The heterogeneous phase processing at the correlated pH of 7.6 demonstrated the highest formed CO product at the temperature of 200 °C, compared with literature. This is particularly promising for reagent purity hydrogen-fed fuel cells. The kinetics for each co-precipitated solid was evaluated regarding the efficiency for the WGS in a fixed bed reactor.     

Supramolecular solvent-based liquid phase microextraction of malachite green at trace level from water samples for its UV–vis spectrophotometric detection

A simple and fast microextraction procedure based on supramolecular solvent extraction of malachite green from water samples has been established in the presented work. The effective analytical parameters including pH, solvent volume, sample volume etc. on the quantitative recoveries of the malachite green were optimised. Matrix effects were also investigated. The preconcentration factor was found as 50. The limit of detection and limit of quantification were 16.3 and 54.5 µg L^?1, respectively. The relative standard deviation percentage was below 7%. The presented procedure was applied to the determination of malachite green content of natural water samples from fish farm and tap water etc.     

Note on the effect of activity coefficients on the NMR association constants for the 2,4-dinitrotoluene—diphenylamine system. The Qureshi—Varshney—Kamoonpuri equation. Possible role of hydrogen bonding.

The NMR studies of the charge transfer complex between 2,4-dinitrotoluene and diphenylamine in CCl₄ are reinvestigated. The proposed Qureshi-Varshney-Kamoonpuri equation shows that activity coefficients have a profound effect on the NMR association constants. The possibility of hydrogen bonding in the system has also been considered.     

Modified layered bimetallic compound used as a novel adsorbent for the solid-phase extraction of monoaromatic hydrocarbons from water samples prior to gas chromatography–mass spectrometry

This study reports a promising method of solid-phase extraction for determining the toluene, ethylbenzene, p-xylene, m-xylene, o-xylene, 1,3,5-trimethylbenzene, and 1,2,4-trimethylbenzene in water samples by gas chromatography–mass spectrometry (GC–MS). Prior to this procedure, the magnesium–aluminum bimetallic hydroxides modified with sodium dodecylbenzenesulfonate (Mg/Al-SDBS-LDH) were prepared and served as the novel solid-phase extractant. The Mg/Al-SDBS-LDH has advantage of good hydrophobicity and larger spacing which facilitates the monoaromatic hydrocarbons (MAHCs) into the interlayer for adsorption. As a result, the seven MAHCs in 500 mL water samples were enriched greatly, and the theoretical enrichment factor reached to 125 times. Under the optimized conditions of solid-phase extraction (SPE) and GC–MS, the mass concentration of each MAHC (0.005–10, 0.01–10, or 0.05–10 ng/mL) had a fine linear relationship with peak area. The correlation coefficients were more than 0.995. The detection limits were between 0.001 and 0.01 ng/mL, and the RSD were between 3.1% and 6.6%. The method had been applied to determine the seven MAHCs in the Dongfengqu river water and laboratory wastewater of Chengdu University of Technology successfully.     

Dispersive liquid–liquid microextraction using an in situ metathesis reaction to form an ionic liquid extraction phase for the preconcentration of aromatic compounds from water

A novel microextraction method is introduced based on dispersive liquid–liquid microextraction (DLLME) in which an in situ metathesis reaction forms a water-immiscible ionic liquid (IL) that preconcentrates aromatic compounds from water followed by separation using high-performance liquid chromatography. The simultaneous extraction and metathesis reaction forming the IL-based extraction phase greatly decreases the extraction time as well as provides higher enrichment factors compared to traditional IL DLLME and direct immersion single-drop microextraction methods. The effects of various experimental parameters including type of extraction solvent, extraction and centrifugation times, volume of the sample solution, extraction IL and exchanging reagent, and addition of organic solvent and salt were investigated and optimized for the extraction of 13 aromatic compounds. The limits of detection for seven polycyclic aromatic hydrocarbons varied from 0.02 to 0.3 μg L⁻¹. The method reproducibility produced relative standard deviation values ranging from 3.7% to 6.9%. Four real water samples including tap water, well water, creek water, and river water were analyzed and yielded recoveries ranging from 84% to 115%.      

High-resolution gas chromatography retention data as a basis for estimation of the octanol–water distribution coefficients (<Emphasis Type="Italic">K</Emphasis>ow) of PCB: the effect of experimental conditions

The semi-experimental approach to approximating physicochemical data relevant to environmental distribution (vapor pressure and gas–octanol distribution) by correlation with gas chromatography (GC) retention data has been extended to the determination of Kow values. We estimated Kow values >10⁴ for polychlorinated biphenyls (PCB), which are often derived by liquid chromatography, by correlation with gas chromatographic retention data. Selecting a set of reference compounds with known Kow values for relative retention time (RRT) correlation enables easy and accurate semi-empirical calculation of further Kow values for a given group of congeners. The RRT/log Kow correlation is validated in this paper with regard to the following gas chromatographic conditions: (1) isothermal versus temperature-programmed elution, (2) the possible effect of the polarity of the stationary phase, and (3) the effect of the format of the standardized GC retention data. The advantages of our Kow(GC) method can be summarized as follows: complex mixtures can be analyzed, only amounts in the nanogram-range or less are required, Kow values of isomers can be determined and the exact structure of compounds need not be known. Normalized GC retention data of persistent organic pollutants are readily available. The quality of the Kow values obtained by the GC method compares well with that for other Kow estimation methods. It depends mainly on the accuracy of the Kow data of the structurally correlated compounds used as standards for the correlation cohort. The Kow(GC) data for all 209 PCB congeners are given.Dedicated to the memory of Wilhelm Fresenius     

Response-to-comments about: “Is it really the method for carbon dioxide determination in human postmortem cardiac gas samples using Headspace-Gas Chromatography–Mass Spectrometry valid?” from T. Saffaj and B. Ihssane

Saffaj et al. recently criticized our method of monitoring carbon dioxide in human postmortem cardiac gas samples using Headspace-Gas Chromatography–Mass Spectrometry.     

Comprehensive evolved gas analysis (EGA) of amorphous precursors for S-doped titania by in situ TG–FTIR and TG/DTA–MS in air: Part 2. Precursor from thiourea and titanium(IV)-n-butoxide

Thermal decomposition of an amorphous precursor for sulfur-doped titania (S:TiO₂) nanopowders, prepared by controlled sol–gel hydrolysis-condensation of titanium(IV) tetrabutoxide and thiourea in aqueous butanol, has been studied in situ up to 850 °C in flowing air by simultaneous thermogravimetric and differential thermal analysis coupled online with quadrupole mass spectrometer (TG/DTA–MS) and FTIR spectrometric gas cell (TG–FTIR) for analysis of gases and their evolution dynamics in order to explore and simulate thermal annealing processes of fabrication techniques aimed S:TiO₂ photocatalysts with photocatalytic activities under visible light.The studied S-doped precursor's decomposition course remembers to that of non-doped xerogel from Ti(IV)-n-butoxide, which seems to retard a considerable amount of organics in the solid phase even at high temperature, probably in polymeric forms, proven by evolution of CO₂ in several temperature regions of decomposition stages. The incorporation form of thiourea in the original xerogel seems to be chemically bounded, resulting lower decomposition temperature than that of pure thiourea, and producing evolution of carbonyl sulfide (COS) already between 120 and 190 °C. Nevertheless, evolution of SO₂, and that of CO₂ is also observed above 500 °C by both EGA detection methods. The latter observation implies that the blackish grey samples obtained even at 750 °C might be simultaneously S- and C-doped ones.