Search results for "SULFUR"
showing 10 items of 545 documents
Continuous SO2 flux measurements for Vulcano Island, Italy
2012
<p>The La Fossa cone of Vulcano Island (Aeolian Archipelago, Italy) is a closed conduit volcano. Today, Vulcano Island is characterized by sulfataric activity, with a large fumarolic field that is mainly located in the summit area. A scanning differential optical absorption spectroscopy instrument designed by the Optical Sensing Group of Chalmers University of Technology in Göteborg, Sweden, was installed in the framework of the European project "Network for Observation of Volcanic and Atmospheric Change", in March 2008. This study presents the first dataset of SO<sub>2</sub> plume fluxes recorded for a closed volcanic system. Between 2008 and 2010, the SO<sub>2</…
Combustion properties of spruce black liquor droplets : Sulfur-free pulping and influence of hot-water pretreatment
2016
Hot-water pretreatment of lignocellulosics prior to sulfur-free alkaline pulping is an interesting approach for recovering value-added carbohydrate- and lignin-derived materials. This paper investigated the chemical composition variations and combustion properties of the black liquors (BLs) from three different cooking processes: two sulfur-free soda-anthraquinone (soda-AQ) and oxygen-alkali (O2-NaOH) cooks and kraft cook, before and after hot-water pretreatment of the spruce sawdust. Relatively less aliphatic acids but more lignin were present in the BLs after hot-water pretreatment as cooking time prolonged. In general, the burning time decreased as follows: soda-AQ BL > O2-NaOH BL ≅ kraf…
Linking the Molecular Signature of Heteroatomic Dissolved Organic Matter to Watershed Characteristics in World Rivers
2015
Large world rivers are significant sources of dissolved organic matter (DOM) to the oceans. Watershed geomorphology and land use can drive the quality and reactivity of DOM. Determining the molecular composition of riverine DOM is essential for understanding its source, mobility and fate across landscapes. In this study, DOM from the main stem of 10 global rivers covering a wide climatic range and land use features was molecularly characterized via ultrahigh-resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). FT-ICR mass spectral data revealed an overall similarity in molecular components among the rivers. However, when focusing specifically on the contributi…
Determination of total and free sulphur dioxide in wine with a continuous-flow microdistillation system
1993
Abstract A continuous-flow microdistillation system for the determination of SO2 (free and total) in wine samples is described. The assembly permits the successive addition of discrete volumes of sample to the microdistillation module with the aid of a nitrogen carrier stream. The nitrogen carrier also transports the volatilized SO2, after the distillation step, to the absorption module, where the analyte reacts with a solution of 2,2′-dinitro-5,5′-dithiodibenzoic acid in phosphate buffer (pH 6) to give a yellow derivative, which is monitored spectrophotometrically at 410 nm. Free and total so2 signals are obtained by operating the microdistillation module at room temperature (ca. 20°C) and…
Direct NMR evidence for the dissociation of sulfur-dioxide-bound acetaldehyde under acidic conditions: Impact on wines oxidative stability
2021
Abstract SO2 reaction with electrophilic species present in wine, including in particular carbonyl compounds, is responsible for the reduction of its protective effect during wine aging. In the present study, direct 1H NMR profiling used to monitor the reactivity of SO2 with acetaldehyde under wine-like oxidation conditions. The dissociation of acetaldehyde bound SO2 was evidenced suggesting that released free SO2 can further act as an antioxidant. EPR and DPPH assays showed an increasing antioxidant capacity of wine with the increase in the concentration of acetaldehyde sulfonate. The presence of acetaldehyde sulfonate in wines was correlated with the overall antioxidant activity of wines.…
A Study Using Sulfur K-Edge XAS of Bitumens, Asphaltenes, Maltenes and their Oxidation Products by Comparison with Model Compounds
1997
High resolution Sulfur K-edge XANES spectra have been recorded at the ESRF on test samples of bitumen, asphaltene and maltene fractions and various model compounds. All these fractions were found to have a low content of sulfidic species as opposed to thiophenic species and it is therefore not surprising that thermally oxidized samples (RTFOT) had also a low content (1%) of sulfoxides. This is indeed consistent with the absence of any detectable S=O signature in the EXAFS spectra which were recorded over more than 1300 eV using the undulator gap scan technique.
Ancient wood of the Acqualadrone rostrum: Materials history through gas chromatography/mass spectrometry and sulfur X-ray absorption spectroscopy
2012
In 2008 the rostrum from an ancient warship was recovered from the Mediterranean near Acqualadrone, Sicily. To establish its provenance and condition, samples of black and brown rostrum wood were examined using sulfur K-edge X-ray absorption spectroscopy (XAS) and gas chromatography/mass spectrometry (GC/MS). GC/MS of pyrolytic volatiles yielded only guaiacyl derivatives, indicating construction from pinewood. A derivatized extract of black wood yielded forms of abietic acid and sandaracopimaric acid consistent with pine pitch waterproofing. Numerical fits to the sulfur K-edge XAS spectra showed that about 65% of the endogenous sulfur consisted of thiols and disulfides. Elemental sulfur was…
Synthesis of new asymmetric xanthene dyes via catalyst-free SNAr with sulfur nucleophiles
2014
Addition of a single functional handle to the tricyclic moiety of fluorescein results in asymmetric xanthene dyes. Our synthesis of a new class of asymmetric xanthenes proceeds via an unusual SNAr with sulfur nucleophiles on electron rich aromatic xanthenes scaffolds in the absence of a metal catalyst. The resulting 3'-thioethers exhibit high photostability and are conveniently converted into reactive dyes for macromolecule labelling.
ChemInform Abstract: Synthesis of New Asymmetric Xanthene Dyes via Catalyst-Free SNAr with Sulfur Nucleophiles.
2014
Addition of a single functional handle to the tricyclic moiety of fluorescein results in asymmetric xanthene dyes. Our synthesis of a new class of asymmetric xanthenes proceeds via an unusual SNAr with sulfur nucleophiles on electron rich aromatic xanthenes scaffolds in the absence of a metal catalyst. The resulting 3′-thioethers exhibit high photostability and are conveniently converted into reactive dyes for macromolecule labelling.
Sulfur Dioxide Oxidation Catalyzed by Photosensitized Ytterbium Diphthalocyanine
2008
Oxidation of SO2 into SO3 was found effectively catalyzed by photosensitized ytterbium diphthalocyanine, YbPc2 (Pc = phthalocyanine ligand, C32H16N8) when performed in air-saturated dimethylformamide (DMF) solution at 20 °C. The process follows according to a multi-step complex mechanism involving chemical induction as its driving force. Excitation energy of the sandwich molecular system in YbPc2 is used to promote the reaction by creating a reactive intermediate form of the ytterbium complex hosting up to eight SO2 molecules. The conversion of SO2 proved complete.