Residual Sulfur Content Research Articles

A Catalyst for Selective Hydrotreatment of Non-Prefractionated FCC Gasoline

A new CoMo catalyst was developed for selective hydrotreatment of FCC gasoline to provide no more than 10 ppm of sulfur in the hydrotreated gasoline and no more than 1,0 point RON decrease against the initial RON. The new catalyst allows the FCC gasoline not to be prefractionated into light and heavy fractions before its hydrotreatment. The hydrotreatment conditions are as follows: feed flow rate 2,2 h–1, 270 °C, 2,5 MPa, H 2 /feed = 150 m 3 /m 3 . The high degree of hydrodesulfurization at a minimal decrease in RON is achieved owing to the high catalyst activity to hydrodesulfurization of the sulfur-containing components and to conversion of reactive high-octane olefins of the FCC gasoline to their less reactive derivatives with the high octane numbers. The catalyst is a CoMoS phase on the support containing amorphous aluminosilicate and γ-Al 2 O 3 . The method for the catalyst preparation is adapted to the Russian industrial facilities and to the feedstock available in Russia. Application of the hydrotreatment process based on this catalyst does not need considerable reconstruction of the facilities available at Russian refineries but provide residual sulfur content less than 10 ppm in the hydrotreated FCC gasoline.

Dependence of visbroken residue viscosity and vacuum residue conversion in a commercial visbreaker unit on feedstock quality

Nine vacuum residual oils were characterized and eight blends of them were processed in the LUKOIL Neftohim Burgas commercial visbreaker unit. It was found that at constant content of about 8vol.% of the fraction boiling up to 360°C (diesel cut) in the visbroken residue the visbroken residue viscosity correlated with the vacuum residual oil visbreaker feed viscosity with a squared correlation coefficient R2>0.98. By application of correlation analysis and intercriteria analysis the vacuum residual oil feedstock parameters which have statistically meaningful impact on conversion to product boiling below 360°C were found to be vacuum residual oil sulfur and hydrogen content, and solubility power of maltenes. The results obtained in this work are consistent with those obtained from other groups, even for other types of vacuum residue processing like ebullated bed hydrocracking. The vacuum residual oils which contained more resinous-asphaltenic materials formed more asphaltenes in the process of thermal conversion. The vacuum residual oil viscosity increment with increasing of asphaltene content for the straight run vacuum residual oils can be described by a second order polynomial. The secondary vacuum residual oils — the visbroken vacuum residual oils exhibited a lower than straight run residual oil dependence of the residue viscosity increment on increasing of the asphaltene content.

Waste-Free SHS Technology of Hydrofining Catalyst Production

This work is dedicated to application of self-propagating high-temperature synthesis (SHS) technology for production of highly effective diesel-fuel hydrofining catalysts. Because of the peculiarities of the structure of the active components formed at high temperatures, these catalysts can be used both without supports and in a blend with conventionally formed catalysts on supports. The synthesized catalysts are several times more effective than conventional GO-70 catalysts, and maintain the residual sulfur content at the 30-35 ppm level. It is shown that a maximally optimal nanostructured system distinguished by a highly developed surface, and, consequently, maximum number of active catalysis centers is formed in the catalyst-synthesis process in a thermocentrifuge at an excess load of 80 g. This ensures maximum desulfurization of the feedstock.

Preparation of SO4 2−/ZrO2 solid superacid and oxidative desulfurization using K2FeO4

A catalyst comprising SO4 2–/ZrO2 (SZ) superacid was prepared by impregnation and characterized by FT-IR, FT IR-pyridine desorption, TG/DTA, XRD, SEM, and BET. A novel procedure for oxidative desulfurization (ODS) of simulated light fuel oil and straight-run gasoline using K2FeO4 over the SZ solid superacid was developed. The effects of the support, calcination temperature, impregnation liquid, concentration, and K2FeO4 and SZ amounts on catalyst activity for desulfurization were investigated. The presence of highly dispersed acidic sites over the support, a huge area of catalyst, and the formation of a tetragonal structure play an important role in ODS using K2FeO4. The catalyst subjected to impregnation with 0.8 mol/L H2SO4, supported on ZrO2, and calcined at 600 °C exhibited the best performance. At a temperature of 30 °C, SZ of 0.2 g, K2FeO4 of 0.2 g, and reaction time of 30 min, the straight-run gasoline desulfurization rate reached 89.2 %, and the residual sulfur content was 18.3 mg/L.

Oxidative desulfurization of diesel fuels in the presence of crown ethers and transition metal peroxo complexes

The catalytic activity of crown ethers and their complexes with transition metal cations in diesel fuel desulfurization has been investigated. With dibenzo-18-crown-6 in combination with NbCl5, the total sulfur content of the fuel can be reduced by a factor of 2 or larger. The effects of the reaction temperature, nature of metal and crown ether, and sorbent acidity on the residual sulfur content are reported. Methods of separation of oxidized compounds, namely adsorption chromatography and extraction are compared in terms of desulfurization efficiency. The latter method is demonstrated to be preferable.

Oxidative desulfurization of catalytically cracked gasolines produced from blended Baku oils

Oxidative desulfurization of catalytically cracked gasolines, produced from a blend of Baku crude oils, with hydrogen peroxide in a formic acid medium under phase-transfer catalysis conditions using pyridine and acetonitrile as ligands has been studied. It has been found that running the process under these conditions on heterogeneous catalysts containing Mo and Co ions makes it possible to decrease the residual sulfur content in the gasolines from 200 to 33–40 ppm.

Effect of the acid-base properties of additives for a cracking catalyst on the sulfur content in liquid products

The effect of the nature and methods for the production of additives for a cracking catalyst on the sulfur content in liquid cracking products was studied. The influence of the acidbase properties of the addi� tives for a cracking catalyst on the redistribution of sulfur raw material between gaseous and liquid products, including that in a gasoline fraction with T EP = 200°C, is analyzed. It is shown that, in contrast to the earlier concept of the approach to choosing such additives, we must consider not only the effect of the acidbase properties of additives but also the aromatization reactions facilitating the formation of hydrogenated thiophene derivatives, which are unstable under catalytic cracking conditions. It is shown that an increase in the additive acidity promotes the reduction of the residual sulfur content in liquid cracking products. The enhancement of both the strength and the concentration of basic sites does not reduce the sulfur content. The simultaneous presence of acidic and basic sites in the structure of a mixed Mg-Al oxide with a spinel structure affords deeper sulfurrefinement of gasoline than the presen ce of only acidic sites. Oxides of a series of metals (Zn, Zr, Cr, Ce, Cu, Ca, Mg, Al) with variable acidbas e properties were used as an additive for a LYUKS cracking catalyst (OAO Gazpromneft'-ONPZ). The data obtained allows us to develop new cracking cata� lysts (or additives for already existing catalysts) that facilitate the production of motor fuels (gasoline) answer� ing the more stringent requirements for sulfur content.

Naphtha hydrodesulfurization over micro and nanostructure MoO3 catalysts

Highly active unsupported MoO3 and Co−MoO3 catalysts were prepared by a simple solution reaction method in the presence of different organic additives. Catalysts were characterized by the XRD, BET surface area measurement, SEM and TEM techniques. Results suggested that utilizing different additives produced different morphologies of MoO3 microstructures. Optimizing reaction conditions was found to produce more active molybdenum oxide nanoparticles when urea and PEG200 additives were utilized. XRD and TEM results indicated crystal growth restriction after cobalt incorporation. Catalytic activities of prepared materials were evaluated in the hydrodesulfurization reaction of Naphtha. Products were analyzed by XRF to determine the residual sulfur content of the feed after the reaction occurred. It was concluded that nanostructures and promoted catalysts had higher activities than microstructure samples. Ultimately, the reaction over the urea-prepared promoted catalyst decreased the sulfur content of the feed of Naphtha from 2420 to 24 ppm, which is considerably lower than that of commercial catalysts.

Oxidative Regeneration of Sulfide-fouled Catalysts for Water Treatment

This study tested the stability, activity, and selectivity of an alumina-supported Pd–In bimetallic catalyst during repetitive sulfide fouling and oxidative regeneration conditions. Nitrate reduction with hydrogen was used as the probe reaction in a continuous-flow packed-bed reactor to assess changes in the catalyst structure as a result of the fouling and regeneration processes. Partial regeneration of a severely sulfide-fouled Pd–In catalyst was achieved with a NaOCl/NaHCO3 solution. However, the regenerated catalyst had a reduced activity for NO3− reduction and increased selectivity towards NH3. Analysis of the catalyst bed after regeneration experiments using XPS, ICP-MS, and BET surface area revealed that bulk structural transformations of the Pd–In bimetallic catalyst occurred, as a result of preferential Pd dissolution near the column influent. The dissolved Pd showed limited mobility in the column, and was re-deposited on the catalyst, resulting in Pd enrichment on the catalyst surface and redistribution of Pd towards the end of the column. These changes along with residual sulfur content on the catalyst surface were likely responsible for the increased selectivity towards NH3. These results indicate the importance of limiting the exposure of reduced sulfur species to Pd-based catalysts, especially when treating contaminants like NO3−, where product selectivity is a priority.

Comprehensive analysis of diesel hydrotreating feedstock

Comprehensive analysis of the physicochemical properties of petroleum fractions, components of hydrotreater feedstock for manufacturing diesel fuel, was performed. Twenty two fractions, of which 14 are straight-run oil distillates, six are products of thermal and thermocatalytic processes, and two fractions represent mixed hydrogen-treatment feedstock, were studied. The fractional composition, the density, the refractive index, the sulfur content, the total concentration of aromatic hydrocarbons, and the amounts of sulfonatable compounds and aromatic hydrocarbons of different classes were determined. The group composition of sulfur compounds in feedstock sources and in the mixed hydrotreater feedstock was determined. The influence of the quality of hydrotreating feedstock on the residual sulfur content in the hydrogenation product was shown for industrial conditions.

Desulfurization in roasting iron-ore pellets

Desulfurization of iron-ore pellets was considered in [1‐7]. On the basis of these results and the thermodynamic analysis of possible reactions, the main chemical reactions of sulfur compounds during the heat treatment of pellets may be established. All the reactions associated with pellet desulfurization may be divided into four groups: the dissociation of sulfides; their oxidation; the formation of sulfates; and their dissociation. Literature data on the kinetics of pellet desulfurization relate only to isothermal heating and are of limited application. In the present work, to address this lack of data, we study the desulfurization kinetics of unfluxed Sokolovsk‐Sarbaisk and Kostomuksha pellets, with different contents of the initial sulfur in the concentrate (summarized in the table), during nonisothermal heating (at variable ambient temperature). The experimental method involves heating weighed pellets at constant velocity (50‐70 ° C/min) to a specified temperature in an air flux (0.15 m/s) and subsequent cooling in water. The residual sulfur content in the pellets is determined by chemical analysis. Desulfurization is studied at different heating rates and with different pellet basicity.

Russian environmentally clean diesel fuels of European quality

The results of screening tests of foreign catalysts from Criterion, Haldor Topsoe, and Akzo Nobel for production of EN-590 (Euro-2, Euro-3) diesel fuels are examined. The effectiveness of revamping the LCh-24/2000 unit for processing these fuels using the Akzo Nobel catalyst package was demonstrated. The physicochemical characteristics of the diesel fuel with additives that satisfies the requirements of GOST R 52368-2005 for fuel with a residual sulfur content of less than 50 ppm are reported.

Diesel fuel desulfurization with hydrogen peroxide promoted by formic acid and catalyzed by activated carbon

Desulfurization of diesel fuels with hydrogen peroxide was studied using activated carbons as the catalysts. Adsorption and catalytic properties of activated carbons for dibenzothiophene (DBT) were investigated. The higher the adsorption capacity of the carbons is, the better the catalytic performance in the oxidation of DBT is. The effect of aqueous pH on the catalytic activities of the activated carbons was also investigated. Oxidation of DBT is enhanced when the aqueous pH is less than 2, and addition of formic acid can promote the oxidation. The effect of carbon surface chemistry on DBT adsorption and catalytic activity was also investigated. Adsorption of DBT shows a strong dependence on carboxylic group content. The oxidative removal of DBT increases as the surface carbonyl group content increases. Oxidative desulfurization of a commercial diesel fuel (sulfur content, 800 wt. ppm) with hydrogen peroxide was investigated in the presence of activated carbon and formic acid. Much lower residual sulfur content (142 wt. ppm) was found in the oxidized oil after the oxidation by using the hydrogen peroxide–activated carbon–formic acid system, compared with a hydrogen peroxide–formic acid system. The resulting oil contained 16 wt. ppm of sulfur after activated carbon adsorption without any negative effects in the fuel quality, and 98% of sulfur could be removed from the diesel oil with 96.5% of oil recovery. Activated carbon has high catalytic activity and can be repeatedly used following simple water washing, with little change in catalytic performance after three regeneration cycles.

Oxidative Desulfurization of Diesel Fuels with Hydrogen Peroxide in the Presence of Activated Carbon and Formic Acid

Oxidative desulfurization (ODS) of diesel fuels with hydrogen peroxide was studied, using activated carbon as the catalyst. The adsorption and catalytic properties of activated carbons for dibenzothiophene (DBT), and the correlation between them, were investigated. The higher the adsorption capacity of the activated carbons, the higher the catalytic performance in the oxidation of DBT. DBT is oxidized by active oxygen species on the carbon surfaces when DBT is adsorbed on the carbon surfaces. The effect of the aqueous pH on the catalytic activities of the activated carbons was also investigated. It is observed that the oxidation rate of DBT on the carbons is enhanced when the aqueous pH is <2. The addition of formic acid can promote the oxidation of DBT in the presence of the wood carbons. The ODS of a commercial diesel fuel (with a sulfur content of 800 ppm) with hydrogen peroxide was investigated in the presence of activated carbon and formic acid. A much lower residual sulfur content (142 ppm) in the oxidized oil is observed after the oxidation, using the hydrogen peroxide−activated carbon−formic acid system, compared to that for a hydrogen peroxide−formic acid system, and the resulting oil, which contained 16 ppm of sulfur, is obtained after activated carbon adsorption; 98% of the sulfur could be removed from the diesel oil, with 96.5% oil recovery. Activated carbon has a high catalytic activity for the oxidative treatment of diesel fuels and can be used repeatedly. The reaction and adsorption in the desulfurization process are coupled, which causes low residual sulfur content in the oxidized oil. These results may indicate that activated carbon has a potential application in ODS to meet future regulations of sulfur in diesel fuels.

New estimates of sulfur degassing and atmospheric mass-loading by the 934 AD Eldgjá eruption, Iceland

The 934 AD Eldgjá basaltic flood lava eruption in southern Iceland is the largest on Earth in the last millennium. The Eldgjá fissures produced 19.6km3 of transitional basalt in a prolonged eruption that featured at least eight distinct episodes and may have lasted for 3–8 years. The atmospheric SO2 mass loading by Eldgjá is determined by new measurements of pre-eruption and residual sulfur contents in the products from all phases of the eruption. A pre-eruption sulfur content of ∼2150ppm indicates that the magma carried 232Mt of SO2 to the surface, where vent and lava flow degassing released 219Mt into the atmosphere. This value corresponds to a potential H2SO4-aerosol yield of ∼450Mt, increasing previous H2SO4-aerosol mass estimates by a factor of 2.6–4.5. Approximately 79% of the original sulfur mass was released at the vents, indicating ∼185Mt SO2 were discharged into the atmosphere above the Eldgjá fissures and carried aloft by the eruption columns to upper tropospheric and lower stratospheric altitudes (∼15km). Consequently, only ∼35Mt SO2 escaped from the lava into the lower troposphere. These estimates of the SO2 mass loading from Eldgjá make it the greatest known volcanic pollutant of recent history, exceeding that of 1783 AD Laki and 1815 AD Tambora eruptions by factors of 1.8 and 2.0–2.8, respectively. However, the intensity of climatic effects deduced by the Eldgjá event are not thought to have surpassed that of Laki or Tambora because the eruption was prolonged and subsequently the sulfur emissions were drawn out over several years. The lack of detailed historic records for this period make estimates of the effects of long term but significant release of SO2 (30–70Mt/yr) on the atmosphere uncertain.

Dithionite bleaching of thermomechanical pulp: factors having effects on bleaching efficiency

The efficiency of dithionite bleaching of Norway spruce (Picea abies) thermomechanical pulp was studied by applying various multivariate data analysis techniques to analytical data (temperature, pH, ion chromatographic and energy-dispersive X-ray fluorescence data). In addition, modeling the residual sulfur content of bleached pulp by means of diffuse reflectance UV-vis spectral data from laboratory-scale bleaching experiments was attempted. The results indicated that this lignin-preserving bleaching process could be evaluated by means of the analytical data using either PCR or PLS models. These models also indicated that wavelengths below 400 nm should not be used in measuring the pulp brightness. The residual sulfur content of pulp could not be reliably determined by multivariate modeling of the diffuse reflectance UV-vis spectral data. Copyright © 2000 John Wiley & Sons, Ltd.

98/03352 Economic and environmental evaluations of waste treatment and disposal technologies for municipal solid waste: Daskalopoulos, E. et al. Applied Energy, 1997, 58, (4), 209–255

The NOXSO process uses a regenerable sorbent that removes SO2 and NOX simultaneously from flue gas. The sorbent is a γ-alumina bead impregnated with sodium carbonate. The process was successfully tested at three different scales, equivalent to 0.017, 0.06, and 0.75 MW of flue gas generated from a coal-fired power plant. These test results were used to develop a mathematical model for the NOXSO fluid-bed adsorber (NOXSO Corp., Library, PA). The model predicts SO2 and NOX removal efficiencies as a function of process conditions and sorbent properties. The spent sorbent was successfully regenerated with either hydrogen or natural gas. The presence of steam during regeneration helps to remove the residual sulfur, but the benefit of steam diminishes when its inlet concentration exceeds 25%. A design equation for a moving-bed regenerator using natural gas as the regenerant was developed from the 0.06 MW results. The adsorber model and the regenerator design equation were used together to determine the optimum residual sulfur content of the regenerated sorbent. It was concluded that the NOXSO LCTU (0.06 MW) would operate at the minimum cycle time of sorption and regeneration if the sulfur content of the regenerated sorbent was controlled at 0.8 wt%.

Porous graphite matrix for chemical heat pumps

Expanded graphite powders were prepared by rapid heating of expandable graphite powders intercalated with sulfuric acid at different heat treatment temperatures (HTT). Porous graphite matrices with 100–400 kg m −3 of bulk density were fabricated by pressing expanded graphite powders in order to use as heat conductive media. They were characterized using an C/S analyzer, inductively coupled plasma spectroscopy, X-ray diffraction, scanning electron microscopy, Fourier transform infrared (FTIR), nitrogen adsorption, optical microscopy and helium pycnometer before and after heat treatment. Gas permeability and thermal conductivity were measured for porous graphite matrices with different HTT and bulk densities. Chemical analysis and FTIR showed that as the HTT of expandable graphite powders increase, the residual sulfur content decreased remarkably. Nitrogen adsorption experiments for expanded graphite powders showed that specific surface area and total pore volume increased with HTT. Helium penetration results showed that porous graphite matrices with different HTT have noticeably different open porosities which were attributed to the different degrees of expansion of graphite layers. The gas permeability of porous graphite matrices was in the range of 10 −12–10 −15 m 2 and exhibited higher values with low HTT. Thermal conductivity values in the axial and the radial directions were in the range of 4.1–20.0 and 4.6–42.3 W mK −1, respectively. A semi-empirical model was developed that can be used to correlate with the thermal conductivity of graphite matrix on the basis of solid conductivity, bulk density and porosity.

Variability in biomarkers of different saline basins in China

42 samples (sediments and crude oils) from 5 different saline/hypersaline basins of China were examined using variety of geochemical techniques. A pronounced even over odd distribution ofn-alkanes is observed for the Ejinur, Jianghan samples. Abundance of isoprenoid alkanes, dominated by phytane (C20 up to 20 per cent in EOM), and C25 and C30 components is another outstanding feature of these studied lacustrine hypersaline settings, indicating important contributuions from archaebacteria. Gammacerane is a major component of some Eocene Jiangham samples and Cretaceous Taian sediments. Absolute concentration of phytane and gammacerane appears to be linearly related to chlorine and residual (reduced) sulfur contents of sediments from Jianghan basin, suggesting sulfur incoporation might have played an important role in the enhacement of these biomarkers in the anoxic hypersaline, alkaline settings. Wide range of organic sulfur compounds in immature samples of Jianghan Basin reflects a significant pathway for sulfur incorporation under hypersaline, extremely anoxic/reducing conditions, although for some structures a direct origin from some sulfur archaebacteria can not be excluded. Brackish salt marsh sediment and oil from Lenghu depression contain abundant lupane, strong OEP inn-alkane series, and predominance of C29 steranes, suggesting a markedly input from vascular higher plants. The marginal marine evaporate sediments from the hypersaline Triassic Yangtze Platform is unique for its predominant, complete series of isoprenoid alkanes up to C36 (abundant) and C40 (trace). These long-chain isoprenoids are probably derived from phytoplanktons in addition to archaebacteria. The marked difference in biomarker distributions from the various suites of samples support that application of these biomarkers to help effectively characterize different saline basins. The molecular variation is, however, not only due to their discrepancy in biological sources, but also the extension of sulfate reduction and the availability of metal ions during early diagenesis.

Thermodynamic simulations of lignite-fired IGCC with in situ desulfurization and CO 2 capture

IGCC cycles running on Greek lignite with in situ desulfurization and CO 2 capture were simulated using the ASPEN PLUS process simulator and compared with other power cycles. Dolomite was chosen as the material for in situ desulfurization. Considering the power produced and residual sulfur content of the off-gas, an oxygen-blown gasifier operated at 1.8 MPa and 950°C, having a thermal efficiency of 38.9%, gives the best performance. The efficiency loss due to CO 2 capture can be largely compensated using IGCC cycles.