Treatment performance of volatile organic sulfide compounds by the immobilized microorganisms of B350 group in a biotrickling filter

BACKGROUND: In this work, the feasibility of biodegradation and the removal performance of sole and mixed odorous vapors, such as dimethyl disulfide (DMDS), methyl phenyl sulfide (MPS), and ethanethiol (EtSH) in an EtSH‐acclimated biotrickling filter seeded with commercially available B350 microorganisms, were investigated. RESULTS: Removal efficiencies (REs) for DMDS as a sole substrate were evaluated under different inlet concentrations and empty bed residence times (EBRT), 100% RE was achieved at concentration below 0.4 g m^?3 at EBRT 110 s. In addition, 100% RE was obtained for binary EtSH and DMDS (3:2) at the same EBRT. According to the Michaelis–Menten type kinetic equation, the maximum removal rates (V_max) were calculated as 28.7 and 13.9 g m^?3 h^?1 for DMDS and MPS as sole substrate, respectively, while V_max was 22.1 and 10.1 g m^?3 h^?1 for DMDS and MPS in the presence of EtSH and EtSH‐DMDS mixture, respectively. After 5 and 20 days starvation, the re‐acclimation times were only 2 and 8 days, respectively, for the binary system. An EtSH:DMDS:MPS (3:2:1) ternary mixture was removed efficiently by the rebooted system after starvation. CONCLUSION: The proposed system can be applied to cost‐effectively decompose a mixture of volatile organic sulfide compounds at pilot scale. Copyright © 2011 Society of Chemical Industry     

Study of a newly isolated thermophilic bacterium capable of Kuhemond heavy crude oil and dibenzothiophene biodesulfurization following 4S pathway at 60 °C

BACKGROUND: To meet stringent emission standards stipulated by regulatory agencies, the oil industry is required to bring down the sulfur content in fuels. As some compounds cannot be desulfurized by existing desulfurizing processes (such as hydrodesulfurization, HDS) biodesulfurization has become an interesting topic for researchers. Most of the isolated biodesulfurizing microorganisms are capable of desulfurization of refined products whose predominant sulfur species are dibenzothiophenes so biocatalyst development is still needed to desulfurize the spectrum of sulfur‐bearing compounds present in whole crude. RESULTS: The first desulfurizing bacterium active at 60 °C has been isolated, which reduces DBT concentration from 2 mmol L^?1 to 0.1 mmol L^?1 after 95 h, following the 4S pathway. Its DBT desulfurization pattern was represented by the Michaelis‐Menten equation. Various parameters such as V_max, K_m, µ_m, K_s and maximum specific DBT desulfurization rate were calculated which are 0.092 mmol L^?1 h^?1, 3.554 mmol L^?1, 0.157 h^?1, 3.722 mmol L^?1 and 0.192 mmol L^?1 DBT g^?1 DCW (dry cell weight) h^?1, respectively. It can desulfurize 50% of the sulfur content of Kuhemond heavy crude oil (KHC oil) with an initial sulfur content of 7.6%wt in 6 days. Its maximum specific desulfurization rate for KHC oil is equivalent to 0.005 g sulfur g^?1 DCW h^?1. The bacterium was isolated during a heavy crude oil biodesulfurization project initiated by PEDEC, a subsidiary of National Iranian Oil Company. CONCLUSION: The KHC oil sulfur removal efficiency of the bacterium is approximately five times that of BBRC‐9016 bacterium. It removes sulfur selectively without using sulfur‐containing compounds as its carbon source. By applying various media during its isolation, the probability of screening the correct microorganism is increased. Copyright © 2008 Society of Chemical Industry     

Investigation of sour gas desulfurization process by nano absorber and under magnetic field in a packed tower; experimentally and theoretically

ABSTRACT

Hydrogen sulfide is a major contaminant that is expelled into the atmosphere by chemical industry. So, the mechanism for absorption of sulfur from sour gas by carbon nano-tubes in a packed bed under a magnetic field is considered, in this paper. Therefore, empirical and theoretical studies have been done to obtain the sulfur content in the outlet gas stream. The independent variables studied in this paper include: the magnetic field (1.5 amperes), initial sulfur content (0, 0.003, 0.008, 0.013, 0.05 and 0.1?mole/m³) and gas temperature (33°C, 37°C and 40°C). The gas flow rate is (0.18, 0.2 and 0.22?m³/min). The minimum amount of hydrogen sulfide in the output stream is selected as the aim of the experiments and related conditions as optimal operating conditions. Results indicate that the sulfur oxidation curves contains an approximately linearly increasing segment when the applied field intensity increases from 90 to 160?Oe, and that the sulfur oxidation percentage is improved by nearly 5.8% when the magnetic field is increased from 90 to 400?Oe. Obtained results state the optimum flow rate and temperature for maximum desulfurization is 0.22?m³/min and 40°C, respectively. Results show, the increase in the initial concentration under the operating temperature and magnetic field increases the effective mass transfer coefficient from 2.2–8.3. In addition the effective mass flux of hydrogen sulfide removal can be extended to 5.9, in this state. Finally, the experimental results have a fairly good fit with theoretical results.     

Design and performance of biofilters for the removal of alkylbenzene vapors

Three identical biofilters, run under the same conditions but inoculated with different mixed cultures, were fed a mixture of toluene, ethylbenzene, and o-xylene (TEX) gases. Inert porous perlite was used as support material, in contrast to the more conventional biofiltration systems where natural supports are used. Biodegradation started in all three biofilters a few hours after inoculation, without previous adaptation of the inocula to the toxic mixture. Despite acidification of the systems to pH values below 4·5, the elimination capacities reached were fully satisfactory. The best performing biofilter, in which bacteria were dominant, showed an elimination capacity of 70 g TEX m⁻³ h⁻¹ with a near complete removal of the mixture up to an influent concentration of 1200 mg TEX m⁻³ at a gas residence time of 57 s. Most of the ingoing carbon was recovered as carbon dioxide in the outgoing gas. In the other biofilters fungi dominated and performance was slightly worse. With single substrates, the elimination capacity was higher for toluene and ethylbenzene than for the TEX mixture, whereas o-xylene removal was slowest in all cases. Also when feeding the mixture to the biofilters, o-xylene was removed most slowly.     

The phenomenology and the mathematical modeling of the silicone‐supported chemical oxidation of aqueous sulfide to elemental sulfur by ferric sulphate

When pumping a sulfide solution through a silicone cylinder immersed in a solution of ferric sulfate, a cloud of elemental sulfur is formed in the ferric sulfate if the pH of the sulfide solution is below about 8.5. The elemental sulfur subsequently sediments as orthorhombic α‐sulfur particles. H₂S(aq) diffuses through the pores of the hydrophobic silicone membrane and simultaneously reacts to become sulfur. This was confirmed by a mass balance between the amount of sulfide removed from the sulfide solution and the amount of solid product formed in the ferric solution. During the experiment, the pH of the non‐buffered sulfide solution rises up to a maximum of 8.5; this is explained by the continuous protonation of HS caused by the removal of H₂S(aq). The pH of the strongly acidic (pH 1.5) ferric sulfate solution hardly decreased. A mathematical model has been developed to quantify the phenomena related to the removal of H₂S(aq). The model has been succesfully validated with the data of batch experiments. An Arrhenius‐like relationship was found between the process temperature and the overall mass transfer coefficient K. A sulfide oxidation rate of 2.5 g S dm⁻³ day⁻¹ was predicted for a plug flow reactor. The integration of the novel process with biological sulfate reduction was studied. © 1999 Society of Chemical Industry     

Influence of nitrogen on the degradation of toluene in a compost‐based biofilter

Two identical laboratory‐scale bioreactors were operated simultaneously, each treating an input air flow rate of 1 m³ h^?1. The biofilters consisted of multi‐stage columns, each stage packed with a compost‐based filtering material, which was not previously inoculated. The toluene inlet concentration was fixed at 1.5 g m^?3 of air. Apart from the necessary carbon, the elements nitrogen, phosphorus, sulfur, potassium and other micro‐elements are also essential for microbial metabolism. These were distributed throughout the filter bed material by periodic ‘irrigations’ with various test nutrient solutions. The performance of each biofilter was quantified by determining its toluene removal efficiency, and elimination capacity. Nutrient solution nitrogen levels were varied from 0 to 6.0 g dm^?3, which led to elimination capacities of up to 50 g m^?3 h^?1 being obtained for a toluene inlet load of 80 g m^?3 h^?1. A theoretical analysis also confirmed that the optimum nitrogen solution concentration lays in the range 4.0–6.0 g dm^?3. Validation of the irrigation mode was achieved by watering each biofilter stage individually. Vertical stage‐by‐stage stratification of the biofilter performance was not detected, ie each filter bed section removed the same amount of pollutant, the elimination capacity per stage being about 16 g m^?3 h^?1 per section of column. © 2001 Society of Chemical Industry     

The sulfur chain in biogas production from sulfate‐rich liquid substrates: a review on dynamic modeling with vinasse as model substrate

Vinasse is a sulfate‐rich liquid substrate, from which high levels of hydrogen sulfide in biogas can be obtained due to the sulfate reduction process under anaerobic conditions. Hydrogen sulfide is corrosive and toxic and must be removed for any utilization of the biogas. Mathematical models have been developed to study separately sulfate reduction in anaerobic digestion and sulfide removal from biogas streams. However, the levels of hydrogen sulfide produced in the anaerobic digestion stage have an effect on the sulfide removal processes in the next stage. As a method to study both processes and their interaction, a new approach is introduced and reviewed in the present article: the sulfur chain in biogas production. The necessity of studying the sulfate reduction processes in vinasse as a typical sulfate‐rich substrate to predict hydrogen sulfide concentrations in the gas phase, as well as the best model approach to that aim are established here. In addition, the approaches to model sulfide removal based on direct conversion processes, the models' capability to predict the removal of hydrogen sulfide from the biogas (at levels between 20 000 and 30 000 ppm_v) as well as the concentration profile of the reactants in this removal processes are discussed. © 2013 Society of Chemical Industry     

Heterobimetallorganische 1,2‐(N,N‐Dimethylaminomethyl)ferrocenyl‐Derivate des vier‐ und zweiwertigen Zinns: Synthesen,Charakteristika und Kristallstrukturen

SnCl₄ reacts with [1,2‐(N,N‐dimethylaminomethyl) ferrocenyl]lithium (FcNLi) under formation of the organo tin compounds of the four valued tin (FcN)_n SnCl _4‐n [n = 1( 1 ), 2( 2 ), 3( 3 ), 4( 4 )]. The heterobimetallic chelate complex bis[1,2‐(N,N‐dimethylaminomethyl)ferrocenyl]tin(II) (FcN)₂ Sn ( 5 ) is formed at the reaction of SnCl₂ with two equivalents of FcNLi. The heterobimetallic tin compounds 1 — 5 were characterized by ¹H NMR‐, ¹³C‐NMR and mass spectroscopy, single crystal x‐ray analyses ( 1,3,4,5 ), ⁵⁷ Fe‐Moessbauer spectroscopy ( 1, 3, 4, 5 ), respectively cyclic voltammetry.     

Soda Pulping of Hardwoods Catalyzed by Anthraquinone and Methyl Substituted Anthraquinones

Abstract

Black liquor gasification (BLG) as well as the recovery of lignin and other organic compounds from pulping black liquor would be aided if an efficient sulfur‐free pulping process could be developed. This has provided new impetus for research on soda pulping with redox catalysts instead of sodium sulfide that is presently used in the kraft process. Soda/anthraquinone (AQ) pulping afforded white birch (Betula papyrifera) and sugar maple (Acer saccharum) pulps with equal if not superior strength to kraft pulps. However, the delignification rate was significantly lower for soda/AQ pulping. When AQ was replaced by 2‐methylanthraquinone (2‐MAQ) a delignification rate only slightly lower than that of kraft pulping was obtained at the same effective alkali (EA). At a kappa number of ～20, a soda/2‐MAQ pulp was produced from sugar maple at a higher yield (1.2% on chips) than for a kraft pulp. 2‐MAQ was synthesized, as a powder, at 75% yield using an AlCl₃–mediated Friedel‐Crafts reaction that is one of the methods used for commercial production of AQ.     

Development and simulation studies of an unsteady state biofilter model for the treatment of cyclic air emissions of an α‐pinene gas stream

This paper describes the development and simulation of an unsteady state biofilter model used to predict dynamic behaviour of cyclically‐operated biofilters and compares it with experimental results obtained from three, parallel, bench‐scale biofilters treating both periodically fluctuating concentrations and constant concentrations of an α‐pinene‐laden gas stream. The dynamic model, using kinetic parameters estimated from the constant concentration biofilter, was able to predict the performance of cyclic biofilters operating at short cycle periods (ie, in the order of minutes and hours). Steady state kinetic data from a constant concentration biofilter can be used to predict unsteady state biofilter operation. At a 24 h cycle period, the dynamic model compared well with experimental results. For long cycle periods (ie, hours and days), removal efficiency decreased after periods of non‐loading: the longer the period of non‐loading, the poorer the biofilter's performance at the re‐commencement of pollutant loading. At longer time scales the model did not effectively predict transient behaviour, as adsorption and changes in kinetic parameters were not accounted for. Modelling results showed that similar biofiltration performance for the cyclic and constant concentration biofiltration of α‐pinene is expected for biofilters operating solely in the first order kinetics regime. Poorer performance for cyclic biofilters following Monod kinetics spanning the entire kinetics range is expected as the cycle amplitude increases. The most important parameters affecting the performance of a cyclically‐operated biofilter with short cycle periods are: amplitude of cyclic fluctuations, C_{g, max}/C_g, relative value of the half‐saturation constant in the Monod expression, K_s, and effective diffusivity of α‐pinene in the biofilm, D_e. Copyright © 2005 Society of Chemical Industry     

Thermodynamics and Stoichiometry of Reactions between Hydrogen Sulfide and Concentrated Sulfuric Acid

A thermodynamic analysis of the possible reactions between hydrogen sulfide and concentrated sulfuric acid shows that four reactions are feasible. However, only two of these reactions apparently occur in experiments at 1 atm and 0°C to 150°C. Hydrogen sulfide is first oxidized by molecular sulfuric acid, forming SO₂, sulfur and water, and then the H₂S may react with the dissolved product, SO₂, to generate sulfur and water. The stoichiometry of the consecutive reactions and their dependence on acid concentration were determined experimentally using mass balance measurements. The results of this study suggest a possible alternative method for sulfur removal and recovery that has more advantages.     

Removal of Xylene from Waste Gases using Biotrickling Filters

Two identical laboratory‐scale biotrickling filters, filled with different ceramic materials, were operated in order to investigate the removal of xylene from a waste gas stream. The biotrickling filter columns were seeded with pure bacteria identified as Bacillus firmus, which can utilize xylene as the sole carbon and energy source. The purification performance of the biotrickling filters was examined for xylene inlet concentrations C_g ≤ 3000 mg/m³ at different gas flow rates of 0.2 m³/h, 0.6 m³/h, and 1 m³/h, which correspond to gas empty bed residence times (EBRTs) of 84.8 s, 28.3 s, and 17.0 s, respectively. Both biofilters displayed a removal efficiency of no less than 95 % with the inlet xylene less than 3000 mg/m³ at the EBRTs of 84.8 and 28.3 s. When EBRT decreased to 17.0 s, the biofilter filled with ceramic particle type 2 had a better performance. The flow rate of trickling liquid has little effect on the removal efficiencies of the two filters. In the case of uneven distribution of trickling liquid in the packing materials, the performance of the biofilter can be improved by increasing the nitrogen nutrient supplement. Biomass quantity decreases as the depth of packing material increases in both biofilters, but the biofilter filled with ceramic particle type 1 had more alive bacteria per unit mass of packing material than the other.     

Removal of H2S and volatile organic sulfur compounds by silicone membrane extraction

BACKGROUND: This study explores an alternative process for the abatement and/or desulfurization of H₂S and volatile organic sulfur compounds (VOSC) containing waste streams, which employs a silicone‐based membrane to simultaneously remove H₂S and VOSC. An extractive membrane reactor allows the selective withdrawal of VOSC and H₂S simultaneously from the waste stream, while preventing direct contact between the waste stream and the absorbing solution and/or the biological treatment system. The influence of the sulfur compounds, membrane characteristics, extractant and pH was studied. RESULTS: Sulfide and the VOCS studied, i.e. methanethiol (MT), ethanethiol (ET) and dimethylsulfide (DMS) were removed from the synthetic wastewater using a silicone rubber membrane. Methanethiol showed the highest (8.72 × 10^?6 m s^?1) overall mass transfer coefficient (k_ov) and sulfide the lowest k_ov value (1.23 × 10^?6 m s^?1). Adsorption of the VOCS into the silicone membrane reduced the overall mass transfer coefficient. The k_ov when using Fe(III)EDTA^? as extractant (5.81 × 10^?7 m s^?1) for sulfide extraction was one order of magnitude lower than with anaerobic water (2.54 × 10^?6 m s^?1). On the other hand, the sulfide removal efficiency with Fe(III)EDTA^? was higher (84%) compared with anaerobic water (60%) as extractant. An additional mass transfer resistance was formed by elemental sulfur which remained attached to the membrane surface. CONCLUSIONS: Extraction of sulfide and VOCS from a synthetic wastewater solution through a silicone rubber membrane is a feasible process as alternative to the techniques developed to treat VOSC emissions. Optimizing the aqueous absorption liquid can increase the efficiency of extraction based processes. Copyright © 2008 Society of Chemical Industry     

Synthesis and characterization of novel aromatic polyamides derived from 2,2′‐bis(p‐phenoxyphenyl)‐4, 4′‐diaminodiphenyl ether

BACKGROUND: Wholly aromatic polyamides (aramids) are high‐performance polymeric materials with outstanding heat resistance and excellent chemical stabilities due to chain stiffness and intermolecular hydrogen bonding of amide groups. Synthesis of structurally well‐designed monomers is an effective strategy to prepare modified forms of these aramids to overcome lack of organo‐solubility and processability limitations. RESULTS: A novel class of wholly aromatic polyamides was prepared from a new diamine, namely 2,2′‐bis(p‐phenoxyphenyl)‐4,4′‐diaminodiphenyl ether (PPAPE), and two simple aromatic dicarboxylic acids. Two reference polyamides were also prepared by reacting 4,4′‐diaminodiphenyl ether with the same comonomers under similar conditions. M?_w and M?_n of the resultant polymers were 8.0 × 10⁴ and 5.5 × 10⁴ g mol^?1, respectively. Polymers resulting from PPAPE exhibited a nearly amorphous nature. These polyamides exhibited excellent organo‐solubility in a variety of polar solvents and possessed glass transition temperatures up to 200 °C. The 10% weight loss temperatures of these polymers were found to be up to 500 °C under a nitrogen atmosphere. The polymers obtained from PPAPE could be cast into transparent and flexible films from N,N‐dimethylacetamide solution. CONCLUSION: The results obtained show that the new PPAPE diamine can be considered as a good monomer to enhance the processability of its resultant aromatic polyamides while maintaining their high thermal stability. The observed characteristics of the polyamides obtained make them promising high‐performance polymeric materials. Copyright © 2009 Society of Chemical Industry     

Removal of high concentrations of H2S from simulated natural gas by Acidithiobacillus ferrooxidans immobilized on polyurethane foam

A chemo‐biochemical process for desulfurization of simulated natural gas containing hydrogen sulfide (H₂S) was investigated. The results showed that using polyurethane foam as a support for immobilization of Acidithiobacillus ferrooxidans obtained good biological oxidation performance and the maximum oxidation rate of ferrous iron was 4.12 kg m^?3 h^?1. Moreover, a semi‐empirical formula was set up for calculating theoretical ferrous oxidation rate as a function of influent Fe²⁺ and Fe²⁺ concentration in the bioreactor. The integrated chemical and biological process achieved removal efficiencies of about 80% when treating high concentrations of H₂S (15 000 ± 100 ppmv). © 2012 Society of Chemical Industry     

Removal of dimethyl sulfide in a thermophilic membrane bioreactor

BACKGROUND: Several sources such as the paper and pulp industry and waste treatment plants emit waste gases containing volatile organic sulfur compounds at elevated temperature. Since cooling the hot gases increases the operational cost of biological reactors, application of thermophilic microorganisms could be a cost‐effective solution. The objectives of this study were to investigate the possibility of removal of dimethyl sulfide from waste gases under thermophilic conditions (52 °C) in a membrane bioreactor and to examine the long‐term stability of the reactor at elevated temperature. The effects of operating conditions such as gas residence time, nutrient supply, temperature decrease and short‐term shutdown on elimination capacity were investigated. RESULTS: A maximum elimination capacity of 54 g m^?3 h^?1 (0.108 g m^?2 h^?1) was obtained at a mass loading rate of 64 g m^?3 h^?1 (0.128 g m^?2 h^?1) with a removal efficiency of 84% at a gas residence time of 24 s. The long‐term operation of the thermophilic membrane bioreactor was followed for 9 months. Although the removal efficiency decreased to 50% after 3 months of continuous operation, it recovered (>96%) after the excess biomass was removed by applying high‐velocity liquid recirculation. CONCLUSION: This study demonstrated that the dimethyl sulfide removal is possible in a thermophilic membrane bioreactor with an elimination capacity of 54 g m^?3 h^?1 (0.108 g m^?2 h^?1) at a gas residence time of 24 s. Copyright © 2008 Society of Chemical Industry     

Highly Efficient Oxidative Desulfurization of Fuels by Lewis Acidic Ionic Liquids Based on Iron Chloride

Acidic ionic liquids (ILs) have been employed as extractant and catalyst in the oxidative desulfurization (ODS) process of fuels in recent years. Several Lewis acidic ionic liquids [C₆³MPy]Cl/nFeCl₃ (molar fraction n = 0.5, 1, 2, 3) and [C₆MIM]Cl/FeCl₃ were prepared and used to remove the aromatic sulfur compounds dibenzothiophene and benzothiophene from fuels. In the ODS process, the used ILs acted as both extractant and catalyst with 30 wt % hydrogen peroxide aqueous solution as oxidant. The effects of Lewis acidity of ILs, IL's cation structure, molar ratio of O/S, reaction temperature, and different sulfur compounds on the sulfur removal of model oil were investigated. The results indicated that the sulfur removal for dibenzothiophene was affected by Lewis acidity of ILs and nearly reached 100 % by [C₆³MPy]Cl/FeCl₃ at conditions of 298 K, IL/oil mass ratio of 1/3, O/S molar ratio of 4/1, in 20 min. The sulfur removal of real gasoline reached 99.7 % after seven ODS runs in the [C₆³MPy]Cl/FeCl₃‐H₂O₂ system.     

Poly(benzoxazine‐co‐sulfur): An efficient sorbent for mercury removal from aqueous solution

A novel sulfur‐rich adsorbent, poly(BA‐ala‐co ‐sulfur), was synthesized by reacting allyl functional benzoxazine (BA‐ala) and elemental sulfur. Simultaneous inverse vulcanization and ring‐opening reactions of benzoxazine generated copolymers in several feed ratios. The adsorption behavior of these copolymers was investigated in aqueous solutions containing Hg²⁺. A three level Box–Behnken design with four factors was applied in order to examine the interactive effect of Hg²⁺ concentration (ppm), S % in adsorbent, temperature, and pH. The optimum adsorption conditions were determined as: 10.33 ppm Hg²⁺, 68% S content, 329 K, and pH 6.3. Common isotherm and kinetic models were applied to the experimental data, where the Langmuir isotherm provided the better fit (q _max = 79.36 mg g^?1) and the pseudo‐second order fit indicated chemisorption as the process‐controlling step. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45306.     

A continuous process for recovery of sulfur from natural gas containing low concentrations of hydrogen sulfide

A continuous catalytic process was developed to remove hydrogen sulfide from a natural gas stream using activated carbon as catalyst. The concentration range of hydrogen sulfide in the gas stream studied was 300–3000 ppmv (0.0126–0.126 moles/m³). Virtually 100 percent conversion of hydrogen sulfide was achieved by the combination of various parameters. The “field gas” employed in this study exhibited cracking of some heavier hydrocarbons and made the product sulfur slightly brown. These hydrocarbons should therefore be separated from the gas stream prior to the oxidation reaction. No carbon monoxide or carbon dioxide was produced during the oxidation of hydrogen sulfide. It is concluded that the process described herein has the potential for the removal of hydrogen sulfide as sulfur from a sour natural gas stream on a continuous basis and could therefore eliminate an environmental problem which now exists.     

Removal of sulfur compounds from utility pipelined synthetic natural gas using modified activated carbons

Synthetic natural gas (SNG), which is produced from petroleum and distributed via pipeline in Honolulu by The Gas Company, was analyzed using a gas chromatograph equipped with a sulfur chemiluminescence detector (GC/SCD). Hydrogen sulfide (H₂S), methyl mercaptan (MM), ethyl mercaptan (EM), dimethylsulfide (DMS), dimethyl disulfide (DMDS), tetrahydrothiophene (THT), ethyl disulfide (EDS), and one unidentified compound (UN1) were detected. Among these sulfur compounds, THT is added as an odorant and was present in the highest concentration.A commercial activated carbon (Calgon OLC plus 12X30) was modified by oxidation and impregnation methods and the resulting materials were evaluated for their ability to adsorb sulfur compounds present in SNG. The evaluation results indicate that all of the modification methods can improve the retention of individual sulfur compounds or the total sulfur capacity compared with the untreated virgin carbon. It is also found that activated carbons impregnated with metal impurities have different selectivity for sulfur compounds. Cu and Zn loaded carbons had the highest capacity for H₂S removal, Fe loaded carbon was more efficient for DMS removal (the most difficult S compound to remove), and carbon oxidized by HNO₃ was the best for THT removal.Based on these findings, a composite sorbent consisting of Cu loaded and Fe loaded carbons was designed and tested. The test results indicate that the composite sorbent had improved performance in the removal of individual sulfur compound. A linear programming model was used to design a composite sorbent optimized to minimize the required sorbent mass based on a 1-kW scale fuel cell system service target. Validation tests showed that the optimized sorbent required less of the individual modified carbon components than when they were individually used for the same sulfur removal target.