With the rapid development of the economy, the sulfur dioxide (SO2) emission from China since 2000 is of increasing concern. In this study, we estimate the annual SO2 emission in China after 2000 using a technology-based methodology specifically for China. From 2000 to 2006, total SO2 emission in China increased by 53%, from 21.7 Tg to 33.2 Tg, at an annual growth rate of 7.3%. Emissions from power plants are the main sources of SO2 in China and they increased from 10.6 Tg to 18.6 Tg in the same period. Geographically, emission from north China increased by 85%, whereas that from the south increased by only 28%. The emission growth rate slowed around 2005, and emissions began to decrease after 2006 mainly due to the wide application of flue-gas desulfurization (FGD) devices in power plants in response to a new policy of China's government. This paper shows that the trend of estimated SO2 emission in China is consistent with the trends of SO2 concentration and acid rain pH and frequency in China, as well as with the increasing trends of background SO2 and sulfate concentration in East Asia. A longitudinal gradient in the percentage change of urban SO2 concentration in Japan is found during 2000-2007, indicating that the decrease of urban SO2 is lower in areas close to the Asian continent. This implies that the transport of increasing SO2 from the Asian continent partially counteracts the local reduction of SO2 emission downwind. The aerosol optical depth (AOD) products of Moderate Resolution Imaging Spectroradiometer (MODIS) are found to be highly correlated with the surface solar radiation (SSR) measurements in East Asia. Using MODIS AOD data as a surrogate of SSR, we found that China and East Asia excluding Japan underwent a continuous dimming after 2000, which is in line with the dramatic increase in SO2 emission in East Asia. The trends of AOD from both satellite retrievals and model over East Asia are also consistent with the trend of SO2 emission in China, especially during the second half of the year, when sulfur contributes the largest fraction of AOD. The arrested growth in SO2 emissions since 2006 is also reflected in the decreasing trends of SO2 and SO42- concentrations, acid rain pH values and frequencies, and AOD over East Asia.
Several materials in the class of metal‐organic frameworks (MOF) were investigated to determine their sorption characteristics for sulfur compounds from fuels. The materials were tested using different model oils and common fuels such as low‐sulfur gasoline or diesel fuel at room temperature and ambient pressure. Thiophene and tetrahydrothiophene (THT) were chosen as model substances. Total‐sulfur concentrations in the model oils ranged from 30 mg/kg (S from thiophene) to 9 mg/kg (S from tetrahydrothiophene) as determined by elementary analysis. Initial sulfur contents of 8 mg/kg and 10 mg/kg were identified for low‐sulfur gasoline and for diesel fuel, respectively, by analysis of the common liquid fuels. Most of the MOF materials examined were not suitable for use as sulfur adsorbers. However, a high efficiency for sulfur removal from fuels and model oils was noticed for a special copper‐containing MOF (copper benzene‐1,3,5‐tricarboxylate, Cu‐BTC‐MOF). By use of this material, 78 wt % of the sulfur content was removed from thiophene containing model oils and an even higher decrease of up to 86 wt % was obtained for THT‐based model oils. Moreover, the sulfur content of low‐sulfur gasoline was reduced to 6.5 mg/kg, which represented a decrease of more than 22 %. The sulfur level in diesel fuel was reduced by an extent of 13 wt %. Time‐resolved measurements demonstrated that the sulfur‐sorption mainly occurs in the first 60 min after contact with the adsorbent, so that the total time span of the desulfurization process can be limited to 1 h. Therefore, this material seems to be highly suitable for sulfur reduction in commercial fuels in order to meet regulatory requirements and demands for automotive exhaust catalysis‐systems or exhaust gas sensors. The reduction of the content of sulfur compounds in commercial gasoline and diesel fuels is a major concern of the petroleum, automotive and power generation industries. This is required to meet regulatory requirements and also to enhance the life‐time of exhaust gas aftertreatment systems and sensors or fuel cell components. A series of metal‐organic frameworks is investigated to determine their desulfurization capacity for commercial gasoline and diesel fuel.
Display omitted] •Incorporation of AC less than 2% in MOF-199 can increase micropores and BET surface area, as evidenced by N2 adsorption.•Lewis acid (unsaturated copper) sites could also be increased in the modified MOF-199, as revealed by Py-IR characterization.•Composite with 2% AC showed highest sulfur capacity with 8.46 and 8.53% for H2S and CH3SCH3, respectively.•The adsorption of CH3SCH3 on composite is reversible, physic-adsorption and weak chemisorption were involved. MOF-199 was modified by incorporating activated carbon (AC) during its synthesis under hydrothermal conditions to improve its performance in the removal of hydrogen sulfide (H2S) and dimethyl sulfide (CH3SCH3). A variety of different characterization techniques including X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, nitrogen adsorption/desorption isotherms, scanning electron microscopy (SEM), pyridine adsorption infrared spectroscopy (Py-IR), thermogravimetric- mass spectroscopy (TG-MS) and X-ray photoelectron spectroscopy (XPS) were used to analyze the fresh and exhausted composites. It was found that the composites, which have an amount of AC of less than 2%, had the same morphology as those of pristine MOF-199, but exhibited a more ordered crystallinity structure as well as higher surface area. The composite with 2% AC incorporation showed highest sulfur capacity of 8.46 and 8.53% for H2S and CH3SCH3, respectively, which increased by 51 and 41% compared to that of MOF-199. This improvement was attributed to the formation of more micropores and especially the increased number of unsaturated copper metal sites, as revealed by Py-IR. It is suggested the chemical reaction was apparent during adsorption of H2S, which resulted in the formation of CuS and the collapse of the MOF structure. Whereas reversible chemisorption was found for CH3SCH3 adsorption, as testified by TG-MS and fixed-bed regeneration. Exhausted MAC-2 can be almost totally regenerated by high temperature 180°C nitrogen purge, indicating a promising adsorbent for CH3SCH3 removal.
•High organic-sulfur fat coal and high volatile coal were added into coking coal blend for pyrolysis.•Sulfur transformation and regulation behaviors were investigated by S-XANES.•The volatile matters from high volatile coal can regulate the sulfur transformation.•A selection criteria for using high volatile coal can be achieved. Sulfur transformation and distribution during pyrolysis of an industrial coking coal blend with a high organic-sulfur fat coal was studied in a fixed-bed reactor. Sulfur K-edge X-ray absorption spectroscopy was used to study the sulfur speciation in cokes. Two coals with high volatiles were selected to regulate the sulfur transformation behavior during pyrolysis and the interactions between volatile matters and nascent cokes were investigated. The addition of high organic-sulfur fat coal to coal blend resulted in the increase of sulfur content in coke, but the desulfurization rate also increased during coal blend pyrolysis. Higher amount of sulfur-containing radicals in volatile matters from high organic-sulfur fat coal promoted the interactions with nascent coke and resulted in the higher sulfur retention on the coke surface. Adding high volatile coal into coal blend affected the interactions between different coals and the sulfur transformation. The interactions between sulfur-containing radicals and nascent coke could be inhibited by volatile matters from high volatile coals. Further characterizations confirmed that the volatile matters from high volatile coal, which had a more overlapping temperature range to sulfur release in coal blend, leading to the lower sulfur content in coke, higher desulfurization and weaker S K-edge spectral intensity. The interactions between external volatile matters and nascent coke primarily occurred on the coke outer surface.
•Basic aromatics in coal macromolecular structure changed little after removing 60% organic sulfur.•Low molecular weight fragments produced by branched chain breakage changed coal thermal characteristics.•Contents of carbon-containing groups were changed by reduction effect of assistants.•Side reactions of reducing desulfurization led to the increase of oxygen-containing groups. The present work investigated the effect of efficient reduction desulfurization method (potassium tertbutoxide and hydrosilane system) on coal properties. Characteristic changes of high organic sulfur coal were studied utilizing TGA, FTIR and XPS after desulfurization. Results showed that more than 60% organic sulfur was removed, while the calorific value of coal samples decreased slightly and the aromatics in coal macromolecular structure were destroyed little. After treatment, formation of low molecular fragments from aliphatic carbons leaded to the increase of mass loss in TGA. XPS results revealed that some oxygen-containing groups were deoxidized after reduction treatment. The changes of coal properties were mainly attributed to the fracture of branch chain, the reduction of oxidized carbon atoms and side reactions during reduction desulfurization.
Coking coal is geologically scarce resource and most of them cannot be directly used in steel making due to their higher sulfur content. One desulfurization method that has great potential for massive application is microwave desulfurization, which removes the relatively stubborn organic sulfur under mild conditions. The dielectric properties of coals determine the efficiency of the microwave energy absorption. The key to describing the mechanism of microwave desulfurization and further improvement of the desulfurization efficiency is the dielectric response of organic sulfur compounds in coal to microwave. This study focuses on existing formand microwave response of organic sulfur components of three typical coking coal in China. Resultsshowed that the major organic sulfur in selected coals is thiophene which has a stable structure and is the most difficult to be removed. Several dielectric peaks (dielectric loss) andsignificant differencesofeach selected coal samples are observed. The microwave absorption peaks of the model sulfur compounds are identified to be within 9-11GHz. The real parts of the relative dielectric constants (hereinafter referred to as epsilon') shows a decreasing trend as: diphenyl sulfoxide > diphenyl sulfone > diphenyl sulfide > dibenzothiophene > Octadecane thiol. Response to microwaveare observed to be distinctively different between sulfur-containing and sulfur-free model compounds. The dielectric polarization of mixture (coal mixed with model sulfur compounds) is greater than pure coal. Meanwhile the higher the sulfur content of the coal, the greater the epsilon' is. Sulfur component-sin coal can significantly influence its polarization.
Sulfur content of diesel fuel has been cut down to ultra low levels by environmental regulation in many countries with the aim of reducing diesel engine's harmful emissions and improving air quality. As a result, research on the production of ultra low sulfur diesel (ULSD) has gained enormous interest in the scientific community worldwide. The renewed interest in ULSD research is driven by the need, to have a comprehensive understanding of the various factors influencing deep desulfurization of diesel to the ultra low level as well as to find cost-effective ways for ULSD production. This review discusses the recent advancement on ULSD production from both scientific and applied point of view. The key fundamentals and the factors influencing the removal of the least reactive sterically hindered sulfur species from diesel feedstocks are reviewed and discussed in detail. Latest development in deep HDS catalyst and the scientific basis for the improvements in the activity of the new generation HDS catalyst are presented. Advancement in the deep HDS process technologies is reviewed and various options available for revamping and modifying the existing low sulfur diesel HDS units for ULSD production are described highlighting the importance of catalyst selection and hydrogen consumption issues. Special attention has been paid to the progress in the alternative (non-hydrogenation) process concepts and technologies that are being developed for ULSD production.
Sulfur release behavior of selected sulfur-containing compounds, tetradecyl mercaptan, dibutyl sulfide, phenyl sulfide, 2-methyl thiophene, benzo-thiophene and dibenzo-thiophene, were investigated by pyrolysis coupled with mass spectrometer (Py-MS) and pyrolysis connected with gas chromatogram (Py-GC) under CO2 atmosphere. It was found that the order of sulfur stability is tetradecyl mercaptan
This paper proposes a novel approach to sulfur removal by adding zinc during the digestion process. The effects of zinc dosage on the concentrations of different valence sulfur in sodium aluminate solution were investigated at length to find that high-valence sulfur (S2O3 (2-), SO3 (2-), SO42) concentration in sodium aluminate solution decreases, but the concentration of the S2-in the sodium aluminate solution increases as zinc dosage increases. This suggests that zinc can react with high-valence sulfur to generate S-2-at digestion temperature, which is consistent with our thermodynamic calculation results. In this study, as zinc dosage increases, sulfur digestion rate decreases while sulfur content in red mud markedly increases when zinc dosage was below 4%; the digestion rates of sulfur and sulfur content in red mud remains stable when zinc dosage was above 4%; the alumina digestion rate, conversely, increased slightly throughout the experiment. This suggests that high-valence sulfur in sodium aluminate solution can be converted to S2-and then enter red mud to be removed completely by adding zinc during the digestion process.
The reactions of monoanionic tridentate alkylthiophenylazonaphthols featuring both C(sp3)–S and aryl C(sp2)–S bonds with low-valent group 9 metal compounds afforded monomeric metal complexes via either C(sp2)–S or C(sp3)–S cleavage. Rhodium(I) and iridium(I) selectively cleave C(sp2)–S bond of 2-hydroxy-1-(2′-alkylthiophenylazo) naphthalenes (HL1-HL5) and 1-hydroxy-2-(2′-alkylthiophenylazo) naphthalenes (HL6-HL10) with concomitant two-electron metal based oxidation resulting in the formation of novel M(III) cyclometallates. The molecular structures of the resulting complexes have been determined by single crystal X-ray crystallography. Rhodium(III) or iridium(III) binds desulfurized modified HL1-HL10 ligands via O, N, C(aryl) donor set. Cobalt(I), the remaining member of the group 9, regiospecifically cleaves the C(sp3)–S bond of the diazene ligands with concomitant two-electron oxidation leading to the formation of novel cobalt(III) complexes. The molecular structures of one of the resulting cobalt(III) complex has been determined by single crystal X-ray crystallography. The cobalt(III) center binds one monoanionic ligand (HL) via O, N,S donor set along with a dianionic modified HL through O, N, S(thiolato) donor set. [Display omitted] •Selective cleavage of C(aryl)-S bond in alkylthiophenylazonaphthols by Rh(I)/Ir(I).•Selective C(alkyl)-S rupture promoted by cobalt(II).•Elucidation of the structure of the complexes by X-ray crystallography.•Rationalization of C-S cleavage by group 9 metal ions.