Hydrothermal oxidative desulfurization of thiophene to sulfate: the effect of MoOx, WOx and carbon supports

Catalytic hydrothermal gasification (cHTG) is a sustainable and promising route to convert wet biomass into renewable methane, but the catalyst is deactivated by small amounts of soluble sulfate stemming from the biomass feedstock. Under hydrothermal conditions, sulfate can be converted to the strong catalyst poisons thiols or sulfides by thermochemical sulfate reduction (TSR). In this work, we explored the extent to which TSR occurs under conditions relevant to cHTG operation, along with the impact of various materials on the reaction. Our results indicated that within 60 min, an aqueous solution of 20 wt% glycerol and 10 mM potassium sulfate at 25 MPa started to produce organosulfur compounds at ca. 420–440 °C, with yields for the volatile ones of 3% and 6% at 440 °C and 490 °C, respectively. The main products were non-volatile organosulfur compounds (NVOSC), which were tentatively identified as sulfate esters of glycerol or of glycerol decomposition products. A smaller fraction of products consisted of volatile organosulfur compounds (VOSC). The VOSC identified from the TSR with glycerol were mostly alkyl thiophenes, as well as methanethiol, disulfides and trisulfides with no evidence of H2S formed. Ni-, Mo-, or NiMox-based materials did not show any catalytic effect on sulfate reduction, independent of the sulfidation of the material. Glycerol was proven to be much more reactive towards TSR than acetone, as no TSR products could be observed when acetone was used as a reducing agent. A reaction pathway for the formation of thiophenes from H2S and glycerol is proposed that consists of the dehydration of glycerol, the formation of CO and H2 from glycerol decomposition, hydroformylation of acrolein, and the Paal-Knorr synthesis with succinaldehyde and H2S as intermediates.

Effect of gasoline composition on oxidative desulfurization using a phosphotungstic acid/activated carbon catalyst with hydrogen peroxide

ABSTRACTIn the present study, the production of various transient forms of sulfur during biological oxidation of sulfidic spent caustics under haloalkaline conditions in a stirred tank bioreactor is investigated. Also, the effects of abiotic aeration (chemical oxidation), dissolved oxygen (DO) concentration and sodium concentration on forms of sulfur during biological treatment are demonstrated. Thioalkalivibrio versutus strain was used for sulfide oxidation in spent caustic (SC). The aeration had an important effect on sulfide oxidation and its final products. At DO concentrations above 2 mg l−1, majority of sulfide was oxidized to sulfate. Maximum sulfide removal efficiency (%R) and yield of sulfate production was obtained in Na+ concentration ranging from 0.6 to 2 M. Abiotic aeration, which is the most important factor of production of thiosulfate, resulted in the formation of an undesired product-polysulfide. However, abiotic aeration can be used as a pretreatment to biological treatment. In the bioreactor the removal efficiency was obtained as 82.7% and various forms of sulfur such as polysulfide, biosulfur, thiosulfate and sulfate was observed during biological treatment of SC.

The study assessed the effect of various forms of sulphur (Na 2 S 2 O 3 , elemental S and Na 2 SO 4 ) and nitrogen (UAN-30, NH 4 NO 3 ) on calcium and magnesium content and uptake in spring wheat and cocksfoot. A two-year pot experiment was conducted on soil material of clayey silt granulometric composition. Before the experiment, the soil was characterized by slight acidity and low content of assimilable forms of phosphorus, potassium, magnesium and sulphur. The results show that the experimental factors caused noticeable variation in the content and uptake of calcium and magnesium in spring wheat and cocksfoot. Among the sulphur fertilizers, the greatest increase in calcium and magnesium content and uptake was produced by application of sodium sulphate. The increase in calcium and magnesium uptake was more marked in the case of plants fertilized with nitrogen in the form of ammonium nitrate. The effect of nitrogen fertilization on the analyzed parameters also depended on the species of plant. Wheat grown in the series with ammonium nitrate was characterized by higher Ca and Mg content and uptake than plants fertilized with nitrogen in the form of liquid UAN 30. Calcium uptake by wheat fertilized with NH4NO3 was on average 15% higher for grain and 9% higher for straw compared to wheat fertilized with UAN 30. As for magnesium, the increase was 24.5% and 18%, respectively. Concerning cocksfoot, fertilization with UAN 30 had a greater affect on content and uptake of the analyzed nutrients than ammonium nitrate.

The objective of our study was to assess the effect of soil application of sulfur in ammonium sulfate and gypsum and of either soil or foliar application of elemental sulfur on yield of grass forage and its qualitative parameters. The effect of various forms of sulfur on the yields of grass forage and its qualitative parameters was explored in the form of a small plot experiment in the Bohemian-Moravian Uplands in 2004–2006 involving the following variants: 1) sulfur unfertilised control; 2) ammonium sulfate; 3) elemental sulfur; 4) gypsum; 5) foliar elemental sulfur. Sulfurous fertilisers and foliar elemental sulfur were applied to the soil in doses of 40 kg and 8 kg S per ha, respectively. Nitrogen applied in ammonium sulfate was added to all the other variants in the form of ammonium nitrate. Application of the fertilisers was repeated at the beginning of each vegetation season. The stand was cut twice in the course of vegetation. In the harvested biomass we assessed the content of sulfur, nitrogenous substances, and net energy of lactation. The effect of various forms of sulfur on the grass biomass yields was not significant in either of the two cuts. Yields increased after sulfur fertilisation only in the 1st cut, especially after the application of sulfate sulfur and gypsum, and/or after foliar application of elemental sulfur. In the individual years the sulfur content in the biomass gradually increased significantly (0.17–0.23–0.29%). In the first year the sulfur content did not reach the critical deficiency limit (0.2%). Sulfur fertilisation increased the S concentration in grass forage in all the fertilised variants; the highest S content was detected in the variant where gypsum was applied (0.27%). No significant correlation was established between the values of water-soluble sulfur in the soil and the sulfur content in grass forage. Sulfur fertilisation had no significant effect on the N/S ratio, but was the highest in the variant not fertilised with sulfur and the lowest in the gypsum variant. The content of nitrogenous substances and net energy of lactation were significantly the highest after fertilisation with elemental sulfur and was related, among others, to the lowest yields of this variant. Sulfurous fertilisers did not significantly affect the exchangeable soil reaction and the highest content of water-soluble sulfur after the 2nd cut was seen in the gypsum-applied variant.

The objective of the three-year small-plot trial was to assess the effect of the weather of the year, forecrop, variety, form of sulphur (elementary and sulphate) and additional nitrogen fertilising on the yields and the content of N-substances of the malt barley varieties Jersey and Sebastian. The trial was carried out in 2006–2008 at the experimental site of the Mendel University of Agriculture and Forestry in Brno, the Žabčice locality. The Jersey and Sebastian varieties were grown after three different forecrops – winter wheat with ploughed down straw, sugar beet with ploughed down tops and maize for grain with ploughed down straw. The fertilising treatments differed in the form of sulphur (elementary and sulphate) and date of the additional nitrogen fertilising. As the sulphate form we chose ammonium sulphate (40 kg . ha−1 N and 45.6 kg . ha−1 S) and the same amount was supplied in the form of elementary sulphur; nitrogen was in the form of urea. A dose of 30 kg . ha−1 of ammonium nitrate with limestone (ANL) was applied as additional nitrogen fertilising. The results show that the weather conditions of the respective years had an almost 94 % effect on yields. The very strong effect of the weather overshadowed the effect of the forecrop (3.8 %); the effect of the variety was only half that of the forecrop (1.8 %). The form of additionally applied sulphur and nitrogen during cultivation had a relatively little effect on the yields (0.2 %). The forecrop affected the content of N‑substances most of all (47.3 %). The quality of barley grain is markedly dependent on the course of the weather of the year (40.1 %); the effect of the variety on the content of N‑substances was relatively low (1.6 %). Applications of various forms of sulphur had a small effect on the grain quality (0.01 %), while the effect on additional nitrogen fertilising on the content of N-substances was 8.5 %.

Enhancing the oxidative desulfurization efficiency of cobalt-loaded-porous carbon catalyst via nitrogen doping on carbon support

In this paper we intended to find the effect of the complexation of heavy metals with various forms of sulfur on the content of chlorophyll pigments in dwarf beans ( Phaseolus vulgaris var. Compressius ellipticus ). The effect of two heavy metals, cadmium and respectively lead, in different concentrations, on the content of chlorophyll pigments in the leaves of beans plantlets, by extracting the pigments by the hot process. These were the variants: V 1 Cd 1mg/l, V 2 Cd 1mg/l + 100mg Cys, V 3 Cd 1mg/l + 100mgK 2 SO 4 , V 4 Cd 50mg/l, V 5 Cd 50mg/l+100mg Cys, V 6 Cd 50mg/l+100mgK 2 SO 4 , V 7 Pb 1mg/l, V 8 Pb 1mg/l+100mg Cys, V 9 Pb 1mg/l+100mg K 2 SO 4 , V 10 Pb 50mg/l, V 11 Pb 50mg/l+100mg Cys, V 12 Pb 50mg/l+100mg K 2 SO 4 , V 13 – control sample. Following the experimental research, we can state that the contents of chlorophyll pigments in leaves is negatively influenced by organic sulfur (cysteine) and positively influenced by inorganic sulfur (K 2 SO 4 ), towards inhibition and, respectively, stimulation. Cysteine inhibits with 7% at high concentration of Cd (50mg/l), and K 2 SO 4 stimulates with 1.2% at the same concentration of Cd. In case of Pb (1 mg/l), cysteine inhibits it with 5%, and inorganic sulfur with 1% less as the control. Inorganic sulfur in combination with high concentration of Pb stimulates the pigments production in leaves with 3% more than the control, and concentrated Cd inhibits it with 15%.

Studies of the correlation between mercury content and the content of various forms of sulfur in Polish hard coals

Hydrotreating and oxidative desulfurization of heavy fuel oil into low sulfur marine fuel over dual function NiMo/γ–Al2O3 catalyst

For the insolubility of binary phase system of oxidative desulfurization (ODS) , coordinated ionic liquid [3(C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> NCl- (NH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> CO] as efficient phase-transfer catalyst (PTC) have been applied to enhance the reaction. A coordinated ionic liquid which has been synthesized from urea and tetraethyl ammonium chloride is employed as efficient PTC for ODS of model oil in the present of hydrogen peroxide and acetic acid. The experimental results show that the desulfurization rate of thiophene is up to 70.68%, under the optimal conditions of O/S=3 (molar ratios), reactive time 30 min at 40degC. The optimal amount of coordinated ionic liquid PTC is 0.20 g / 18 mL model oil. The main products of oxidatiive thiophene by hydrogen peroxide and acetic acid are sulfone and sulfoxide of thiophene and SO/".

In this work the hydrothermal synthesis of ZSM-12 zeolite was performed, varying the MTEACl/SiO2 ratio, where the synthesis temperature was 140 oC and the crystallization time was 144 hours. The catalysts were characterized by XRD, FTIR and TG. TiO2/ZSM-12 catalysts were used with titanium ions concentrations of 5, 10 and 15%. The oxidative desulfurization (ODS) reactions were performed using a model mixture containing n-heptane as solvent and thiophene as sulfur compound, H2O2 as an oxidizing agent, and acetonitrile as an extractor solvent at reaction temperatures of 30, 50 and 70 oC. The obtained results shows that TiO2/ZSM-12 with 15% of Ti catalyst has a better performance in the ODS reaction converting thiophene at about 60%.

Promoted visible-light-driven oxidative desulfurization of thiophene over mesoporous PdO-incorporated BaSnO3 nanocomposites

Catalytic growth of carbon fibers from methane and ethylene on carbon-supported Ni catalysts

The principle of a “catalytic nanosponge” that combines the catalysis of organosulfur oxidation and sequestration of the products from reaction mixtures is demonstrated. Group VI metal oxide nanoparticles (CrOx, MoOx, WOx) are embedded within hollow graphitized carbon nanofibers (GNFs), which act as nanoscale reaction vessels for oxidation reactions used in the decontamination of fuel. When immersed in a model liquid alkane fuel contaminated with organosulfur compounds (benzothiophene, dibenzothiophene, dimethyldibenzothiophene), it is found that MoO2@GNF nanoreactors, comprising 30 nm molybdenum dioxide nanoparticles grown within the channel of GNFs, show superior abilities toward oxidative desulfurization (ODS), affording over 98% sulfur removal at only 5.9 mol% catalyst loading. The role of the carbon nanoreactor in MoO2@GNF is to enhance the activity and stability of catalytic centers over at least 5 cycles. Surprisingly, the nanotube cavity can selectively absorb and remove the ODS products (sulfoxides and sulfones) from several model fuel systems. This effect is related to an adsorptive desulfurization (ADS) mechanism, which in combination with ODS within the same material, yields a “catalytic nanosponge” MoO2@GNF. This innovative ODS and ADS synergistic functionality negates the need for a solvent extraction step in fuel desulfurization and produces ultralow sulfur fuel.