Chantal Lorentz

NMR quantification in hydrothermal in situ syntheses

The considerable development of microporous materials by hydrothermal synthesis led us to develop appropriate devices to perform NMR in situ observation of the species during the synthesis. The ‘hydrothermal NMR tube’ is a 10 mm outer diameter tube acting as an autoclave, withstanding temperatures and pressures common to these classes of syntheses and also the corrosive conditions of hydrofluoric acid containing media. During synthesis NMR chemical shifts and signal areas are monitored. It is therefore important to achieve quantitative NMR measurements while synthesis proceeds. On increasing the temperature of samples, considerable NMR signal loss occurs as a consequence of Curies law. Dielectric constant and conductivity effects on signal loss are reflected in the evolution of the quality factor of the probe. As the effects of temperature, concentration of solutes and pH on NMR responses of aqueous samples are considerable, they were therefore carefully studied. The relations between acquisition conditions, transmission and reception and experimental NMR amplitudes were elucidated. A calibration method that does not make use of an internal reference and which is based on relative variations of the Q factor of the r.f. circuit leads to efficient spin counting. This method was successfully applied to quantifying the hydrolysis of aluminum at variable temperature, monitoring 27Al to follow hydrolysis and condensation processes. Copyright

Comprehensive 2D chromatography with mass spectrometry: a powerful tool for following the hydrotreatment of a Straight Run Gas Oil

Comprehensive two-dimensional gas chromatography (GC × GC) is a technique which is rapidly gaining importance for the analysis of complex samples, especially within petrochemical matrixes. Until recently GC × GC has been a technique used within analytical laboratories to characterize complex multi-component mixtures such as fuels, perfumes and organic aerosol extracts, which are difficult to analyze using conventional GC or GC-MS techniques. In the present study we will illustrate how GC × GC-qMS can be used as an effective tool to accurately monitor the conversion of a Straight Run Gas Oil (SRGO) on a Cobalt Molybdenum (CoMo) supported on an alumina sulfide catalyst. A SRGO was hydrotreated at various temperatures and liquid hourly space velocities (LHSV). The products were analyzed and attention was paid to the transformation of sulfur and aromatic compounds. Quantitative analyses using GC × GC-qMS were performed and compared to the “Simulated Distillation” and total sulfur analysis illustrating that this technique can provide a comprehensive view of the entire matrix, family of products and their distribution as well as single molecule evolution upon catalytic conversion.

The Chemical-Loop Reforming of Alcohols on Spinel-Type Mixed Oxides: Comparing Ni, Co, and Fe Ferrite vs Magnetite Performances

Ferrospinels with different metals—Fe, Ni, Co, and Cu—were investigated as oxygen ion and electron carrier materials for the chemical-loop reforming of ethanol, aimed at the production of H2 with intrinsic separation from CO and CO2. The materials used showed different behaviours both during the first step of the loop—the reduction of the annealed spinel with ethanol—and the second step—the re-oxidation with steam—as well as with the increasing cycle number. The differences shown were rationalised in terms of redox behaviour, carbon residue accumulation during the cycle, and ability to restore the starting spinel structure during cycling. Mixed ferrospinels showed enhanced reducibility when compared to magnetite; however, since coke accumulation was unavoidable, the best-performing material amongst the materials tested was Co ferrite, which underwent the greatest reduction and was able to maintain it throughout repeated cycles.

Hydrothermal synthesis and structure determination of the first three-dimensional oxyfluorinated gallium phosphate incorporating lithium

Abstract LiGa3F3(OH)(H2O)2(PO4)2 was synthesised hydrothermally (453xa0K, 36xa0h, autogeneous pressure) from the mixture with molar composition 0.5xa0Ga2O3 : 0.5xa0P2O5 : 3xa0HF : 0.2xa0Li2O : 80xa0H2O. Its three-dimensional structure was solved, at 298 K, by single-crystal X-ray diffraction in the monoclinic space group P21/c (No. 14) with lattice parameters a=8.6885(4)xa0A, b=8.2442(4)xa0A, c=7.1303(4)xa0A, β=104.351(2)xa0A, V=494.80(4)xa0A3, Z=2. Its structure consists of infinite double sheets, made from corner shared GaO3F{F2–x(OH)x} octahedra (x=0, 1 or 2) and PO4 tetrahedra of laueite-type chains, which are linked by GaO2F2(H2O)2 octahedra to generate the framework encapsulating lithium cations. The OH/F substitution is discussed from solid state NMR results.

Biosourced analogs of elastomer-containing bitumen through hydrothermal liquefaction of Spirulina sp. microalgae residues

The hydrothermal liquefaction of Spirulina sp. microalgae (i.e. cyanobacteria) byproducts was investigated for the production of road binders from renewable sources. In the 220–300 °C temperature range, a water-insoluble viscous material was obtained in a ca. 50% yield, which consisted of an oily fatty acid-based fraction mixed with organic and inorganic solid residues (ca. 20%). More interestingly, this material exhibited viscoelastic properties similar to elastomer-containing bitumen, when operating the hydrothermal liquefaction between 240 and 260 °C. This is the first example of a bio-sourced product showing such properties. At higher temperature, fragmentation of species of high molecular weight occurred, resulting in less viscous materials that were no more thermorheologically simple. The reactor filling ratio was also allowed to vary (i.e. 30% versus 60%), showing very little influence in terms of yield and viscoelastic properties of the resulting bio-binders.