Mercaptan Removal Research Articles

Removal of mercaptans from light oils using ionic liquid–NaOH aqueous solution as extractants

The application of ionic liquids as alternatives to conventional organic solvents in the extraction process has been investigated. In the present study, fourteen species of imidazolium-based ionic liquids were added into the NaOH (aq) to remove the mercaptans. The influences of anion species and cation alkyl chain length of the imidazolium-based ionic liquids on the performance of mercaptan removal from light oils have been discussed. The efficiency of extraction for mercaptans exhibited the order of [Ac]−>[OH]−≈[Br]−>[BF4]−. The longer alkyl chain imidazolium-based ionic liquids contributed to enhance desulfurization rate of 1-butyl mercaptan. 100% desulfurization rate of 1-butyl mercaptan was achieved by the anion of Ac− ionic liquids and NaOH (aq) at a volume ratio of 40:1 (V(oil):V(ionic liquid)) and a short equilibrium time within 10min.

Removal of methyl mercaptan with highly-mobile silver on graphitic carbon-nitride (g-C3N4) photocatalyst

Modification of graphitic carbon nitride (g-C3N4) with silver metal significantly improved the adsorption capacity and the photocatalytic degradation activity for methyl mercaptan, which is a typical sulfurous compound, under visible light. These improvements were easily obtained by the shear mixing method. The ultrafine crystallites of metallic silver were formed on surface of carbon nitride by shear mixing of HT-g-C3N4 (Hydrothermal treated g-C3N4) in aqueous solution of silver acetate. One atom of the silver captured ca. 0.6 molecule of methyl mercaptan on average, while a silver atom deposited on TiO2 captured only 0.03 molecule. The migration of silver crystallites over the g-C3N4 surface and the formation of silver thin-layer during the adsorption of methyl mercaptan were observed by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The silver crystallite on g-C3N4 seemed to have higher mobility than that on TiO2 to form the coordination suitable for the adsorption of methyl mercaptan. This coordination of Ag also enhanced the photocatalytic degradation of methyl mercaptan to dimethyl disulfide.

Hybrid Polymer/UiO-66(Zr) and Polymer/NaY Fiber Sorbents for Mercaptan Removal from Natural Gas.

Zeolite NaY and metal organic frameworks MIL-53(Al) and UiO-66(Zr) are spun with cellulose acetate (CA) polymer to create hybrid porous composite fibers for the selective adsorption of sulfur odorant compounds from pipeline natural gas. Odorant removal is desirable to limit corrosion associated with sulfur oxide production, thereby increasing lifetime in gas turbines used for electricity generation. In line with these goals, the performance of the hybrid fibers is evaluated on the basis of sulfur sorption capacity and selectivity, as well as fiber stability and regenerability, compared to their polymer-free sorbent counterparts. The capacities of the powder sorbents are also measured using various desorption temperatures to evaluate the potential for lower temperature, energy, and cost-efficient system operation. Both NaY/CA and UiO-66(Zr)/CA hybrid fibers are prepared with high sorbent loadings, and both have high capacities and selectivities for t-butyl mercaptan (TBM) odorant sorption from a model natural gas (NG), while being stable to multiple regeneration cycles. The different advantages and disadvantages of both types of fibers relative are discussed, with both offering the potential advantages of low pressure drop, rapid heat and mass transfer, and low energy requirements over traditional sulfur removal technologies such as hydrodesulfurization (HDS) or adsorption in a pellet packed beds.

A Comprehensive Set of High-Quality Point Charges for Simulations of Metal–Organic Frameworks

Most classical simulations of metal–organic frameworks model electrostatic interactions using point charges on each atom in the structure. We report atomic point charges derived from periodic density functional theory (DFT) electronic structure calculations for more than 2000 unique experimentally synthesized metal–organic frameworks (MOFs). These charges are publicly available as a supplement to the Computation-Ready Experimental MOF database. These DFT-derived atomic point charges are compared to semiempirical group contribution and charge equilibration methods for assigning charges. As an example of using these charges, we examined each MOF for usefulness in the adsorptive removal of tert-butyl mercaptan (TBM) from natural gas. Monte Carlo simulations revealed many candidate MOF structures with high selectivity for TBM over CH4 and high TBM capacity. We anticipate that this public data set of atomic point charges for MOFs will facilitate high-throughput screening for a wide variety of applications in w...

Adsorption/oxidation of sulfur-containing gases on nitrogen-doped activated carbon

Coconut shell-based activated carbon (CAC) was used for the removal of methyl mercaptan (MM). CAC was modified by urea impregnation and calcined at 450°C and 950°C. The desulfurization activity was determined in a fixed bed reactor under room temperature. The results showed that the methyl mercaptan adsorption/oxidation capacity of modified carbon caicined at 950°C is more than 3 times the capacity of original samples. On the other hand, the modified carbon caicined at 950°C also has a high capacity for the simultaneous adsorption/oxidation of methyl mercaptan and hydrogen sulfide.The introduce of basic nitrogen groups siginificantly increases the desulfurization since it can facilitate the electron transfer process between sulfur and oxygen. The structure and chemical properties are characterized using Boehm titration, N 2 adsorption-desorption method, thermal analysis and elemental analysis. The results showed that the major oxidation products were dimethyl disulfide and methanesulfonic acid which adsorbed in the activated carbon.

Identification of the coke deposited on 13X industrial zeolite molecular sieves during mercaptan removal process

AbstractIndustrial Z10‐13X zeolite was deactivated by coking during the sequenced pressure and temperature swing mercaptan removal unit at the conditions of 40 °C and 68 bar in adsorption mode and 300 °C and 8 bar in regeneration mode. In this study, detailed coke features inside industrial molecular sieves, in terms of molecular structure and also some other brief properties, have been obtained for the first time by combining numerous techniques including gas chromatography coupled with mass spectrometry, thermogravimetric analysis, Brunauer–Emmett–Teller analysis, energy‐dispersive X‐ray spectroscopy, X‐Ray diffraction pattern, and also CO2 and N2 adsorption/desorption isotherms of fresh and coked molecular sieves. The coke species were identified and classified into more than 40 different components following their alkylation and cyclization mechanisms. The coke includes polyaromatic hydrocarbons, and it was much alkylated especially with methyl and ethyl fragments. It is mainly compounded of derivatives of benzene located within the zeolite pore, which could grow into polyaromatic compounds constituted up to four aromatic rings with different guest polar elements. Copyright © 2015 Curtin University of Technology and John Wiley & Sons, Ltd.

Mercaptan removal from natural gas by the efficient cyclic adsorption process; a simulation study

A more efficient and economical cyclic adsorption process was proposed for mercaptan removal from natural gas (NG) to reduce mercaptan content to less than 10 ppm and meet the environmental rules. Continuous sulfur removal is studied for the NG feed stream, with pressure of 6.8 MPa, flow rate of 2850 Nm3/hr and molar composition of 95.98% methane, 0.00182% water vapor, 1% carbon dioxide, 0.0134% mercaptan and 3% heavier hydrocarbons (C3+). The proposed process of Pressure Vacuum Swing Adsorption (PVSA) was designed and simulated as a more efficient alternative process against the current Industrial Pressure-Temperature Swing Adsorption (PTSA). In this work, an improved PVSA process was simulated with sequences of bed pressurization, adsorption, equalization, blow down, bed regeneration by vacuum and purge by product, in each process cycle. Vacuum condition of 10 KPa with the molar purge/feed ratio of 0.06 and temperature of 350 K was required for appropriate bed regeneration from adsorbed mercaptan to approach to the continuous cyclic steady condition. Comparison between PVSA and PTSA, at the same feed characteristics, same packed columns and adsorption operating conditions, revealed that the PVSA process, with less cycle time than PTSA, could achieve the same product purity with 94.8% recovery and 3.90 [mol/kg day] productivity, whereas PTSA has the recovery of 74.04% and productivity of 2.79 [mol/kg day]. At the same time, operating with PVSA, instead of PTSA process, would reduce the operating cost from 88 to 70 [Thousand $/year].

Adsorption of odorous sulfur compounds onto activated carbons modified by gamma irradiation

A commercial activated carbon (AC) was modified by gamma irradiation and was tested as adsorbent for the removal of ethyl mercaptan, dimethyl disulfide and dimethyl disulfide in wet conditions. Modifications were carried out under five different conditions: irradiation in absence of water, in presence of ultrapure water, in ultrapure water at pH=1.0 and 1000mgL−1 Cl−, in ultrapure water at pH=7.5 and 1000mgL−1 Br−, and in ultrapure water at pH=12.5 and 1000mgL−1 NO3−. The chemical properties of each AC were characterized by elemental analysis, temperature programmed desorption and X-ray photoelectron spectroscopy. Outcomes show that a large number of oxygen functional groups were incorporated in the AC surface by gamma irradiation, especially in the AC irradiated in the presence of ultrapure water. The dynamic adsorption test results reveal that the incorporation of oxygen functional groups did not enhance the adsorption capacities for dimethyl sulfide and dimethyl disulfide. A significant improvement in the ethyl mercaptan adsorption capacity was correlated with the incorporation of phenolic groups in the AC surface. Moreover, diethyl disulfide was detected as by-product of ethyl mercaptan oxidation process under wet conditions and its formation depended on the chemical properties of ACs.

Synthesis of carbon nanotube-supported metallo carboxyporphyrin as a novel nanocatalyst for the mercaptan removal

A carbon nanotube-supported metallo carboxyporphyrin has been synthesized and characterized by X-ray diffraction (XRD), field-emission scanning electronic microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR). The prepared catalyst has been evaluated for the removal of mercaptan from gas stream in a fixed bed reactor. The effect of important operating parameters including temperature, gas hourly space velocity (GHSV), and loading (%) was investigated on the mercaptan removal. The results confirmed that the mercaptan concentration could be reduced from 16,800 ppm to less than 10 ppm under optimized conditions by (Fe)TCPP-MWCNTs-NH2 as nanocatalyst.

Odor fading in natural gas distribution systems

Since natural gas is odorless, to assure the customer safety, odorants are added to it to alarm the consumer in the case of a gas leak. Although the odorization is a common practice in natural gas distribution systems, odor fading has been reported in pipelines, which is a great safety risk. This paper summarizes results of experiments conducted to investigate possible chemical and physical mechanisms responsible for odor fading. In these experiments, X-ray photoelectron spectroscopy (XPS) and gas chromatography were used to check the possible interactions of tertiary butyl mercaptan (TBM) as odorant with the pipe material. Evidences of chemisorption, adsorption and desorption of TBM on the iron oxide inside the pipe were observed. It was found that by increasing pressure, rusted surface of the pipe, and temperature or by decreasing the gas flow rate and odorant concentration the mercaptan removal was increased.

Acylation desulfurization of heavy cracking oil as a supplementary oil upgrading pathway

Acylation reaction is used to enhance the basicity and polarity of the thiophenes and thus promote their adsorptive removability by Lewis acid, forming an acylation desulfurization (ADS) process for the refractory sulfurs. The ADS performance of six acylating reagents (ARs) was assessed for heavy cracking oil and light oil at 303K with AlCl3 as the catalyst, and the influence of ADS on the oil quality was also studied. The results show that ADS is efficient to remove the thiophenes, but less efficient for the removal of mercaptans and thioethers in light oil. S-removal rate of 90.9% was achieved for heavy cracking oil with acetyl bromide (AB)-AlCl3 (AB/S=2/1; AlCl3/S=5/1) in 0.5h. The coexistent olefins and aromatics can slightly deteriorate the ADS performance and influence the oil properties. ADS might be used as a promising sulfur separating strategy for the cracking oil.

Methyl mercaptan removal from gas streams using metal-modified activated carbon

Abstract In this paper, removal characteristics of methyl mercaptan (CH3SH) on virgin activated carbon and the metal-modified activated carbons (M–AC) prepared by sol–gel method were studied by using a dynamic method in a fixed bed. The detailed characterization of the catalyst has been done using Scanning electron microscope (SEM), Energy–dispersive X–ray spectrometry (EDS), X–ray photoelectron spectroscopy (XPS), and N2 adsorption/desorption techniques. The results showed that impregnation of metal oxides on the AC significantly enhanced the removal capacity of methyl mercaptan, despite a notable decrease in microporosity. The catalytic activity of different kinds of metal-containing catalysts decrease in the following sequence: Cu–AC ≈ Ni–AC > Al–AC > Fe–AC > Zn–AC. Moreover, calcinations temperature can influence the catalytic activity of the catalyst greatly. XPS results showed that the methyl mercaptan were oxidized by the catalyst. Sulfate species and methyl thiolate accumulated on the catalyst surface, which can block the pores and reduce the active sites.

Mercaptan's Removal from Aqueous Solution using Modified Graphite-Based Adsorbent through Batch-Wise Adsorption–Regeneration

The removal of mercaptans (ethane thiol and 1-methyl, 1-propane thiol) from aqueous solution through adsorption using proprietary, partially porous, and electrically conducting graphite-based adsorbent (called Nyex 2000) was investigated. Nyex 2000 adsorbent was prepared through successive chemical, thermal, and physical treatments of Nyex 1000 adsorbent (previously developed graphite intercalation compound [GIC]-based adsorbent material) with the aim of improved adsorption capacity. The characterization of Nyex 2000 was carried out including laser size analyzer, Boehm surface titration, X-ray (energy dispersive spectroscopy [EDS]) surface elemental analysis, X-ray diffraction (XRD) analysis, N2 adsorption, and zeta potential measurements. The adsorption of both thiols on Nyex 2000 was found to be a rapid process (more than 80% of equilibrium capacity achieved within 5 min). Nyex 2000 showed an adsorption capacity of 6 and 9 mg g−1 for the removal of ethane thiol and 1-methyl, 1-propane thiol, respectively. After adsorption, Nyex 2000 was successfully electrochemically regenerated in a batch electrochemical cell. The regeneration efficiency was found to be consistent at around 100% for five adsorption–regeneration cycles. The electrochemical parameters were as: treatment time of 40 min at a current density of 12 mA cm−2 for a total charge passed of 240 C g−1 at the average cell voltage of 3.5 V. The electrical energy of 120 J was found to be required for electrochemical oxidation of each mg of adsorbed mercaptan on the surface of Nyex 2000.

Wet Scrubbing Removal of Methyl Mercaptan by Peroxymonosulfate under Acidic Condition

Peroxymonosulfate (PMS) was used in wet scrubbing removal of odorous gas methyl mercaptan (CH3SH) under acidic condition (pH = 2) for the first time. Even though CH3SH can hardly dissociate as CH3S− under acidic solution (pKa = 10.3), quick oxidizing reaction may occur at the gas-liquid interface by PMS alone or Co2+ activated PMS oxidation. When the gas flow is 0.5 L min-1, PMS alone can remove 94% of 60 ppm/v CH3SH. The absorption of CH3SH is the rate controlling step of the removal process, however, quick oxidizing reaction with the dissolved CH3SH(aq) molecule could improve the mass transfer of CH3SH from the gas phase into the liquid phase.

Mercaptan removal from natural gas using carbon nanotube supported cobalt phthalocyanine nanocatalyst

The synthesis of carbon nanotubes with a cobalt phthalocyanine (CoPc) complex has been described. The removal of mercaptan from gas stream in the present MWCNT-COOH-CoPc nanocatalyst was tested in a fixed bed reactor. For synthesizing this catalyst, multi-walled carbon nanotubes (MWCNTs) were used as support and MWCNT-COOH-CoPc nanocatalyst with loadings of 10 wt% of cobalt phthalocyanine organometal were prepared using the incipient wetness impregnation method. Nanocatalysts were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis. The effect of important operating parameters including temperature and Gas Hour Space Velocity (GHSV) was investigated. The results confirmed that the best condition can be achieved by setting the temperature at 200 °C and GHSV at 2000 h−1 with maximum mercaptan conversion of 99.99%.

Fiber Adsorbents for Odorant Removal from Pipeline Grade Natural Gas

Sulfur odorant removal from pipeline natural gas can prevent or delay corrosion in gas turbines to increase their lifetime and efficiency. Removal of the odorant tert-butyl mercaptan (TBM) by selective adsorption with fiber sorbent modules and removal with pellet packed beds are compared in terms of capital and operating costs. Capital costs are estimated based on sizing the equipment items needed for each system, which varies depending on the regeneration gas used. Operating costs are estimated based on the utilities needed to run each system, again varying depending on the regeneration gas used, and also on whether heat integration is considered. Using a fraction of the product gas for regeneration is safer, simpler, and more economical than compressed air or nitrogen. Due to the need for more adsorber beds to process the same amount of TBM-containing pipeline natural gas, the capital cost associated with the pellet packed bed system is significantly higher than that of the fiber sorbent system. Heat integration with the sorption system by using the energy generated from waste gas combustion to produce steam dramatically decreases the operating cost by reducing the parasitic load. Overall, this process analysis shows that the fiber sorbent system with heat integration can be an attractive technology compared to packed bed systems for TBM removal.

Comparison of amine solutions performance for gas sweetening

ABSTRACTUsing different kinds of amines, in Fajr‐e‐Jam gas refinery, including mixed or activated amines, have provided the chance for better analysis of different kinds of amines performance. In the current work, the most important parameters in gas sweetening refineries such as amine circulation rate, steam consumption, CO2 and mercaptan removal were investigated for sweetening trains utilizing diethanolamine (DEA), methyldiethanolamine (MDEA), DEA/MDEA and activated methyldiethanolamine (aMDEA). In the case of steam consumption and circulation rates, MDEA and aMDEA, show the less required rates to meet lean amine loadings. For CO2 removal aMDEA has the best efficiency. In the case of mercaptan removal, DEA shows the best absorption rate compared with other three amines. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.

Deep Removal of Methyl Mercaptan in Biogas

For a distributed PEMFC power station utilizing biogas as a source to produce hydrogen, deep desulfurization of the biogas is important. ZnO/γ-Al2O3 and CuO/γ-Al2O3 were prepared by an impregnation method, and their performances on CH3SH removal in the biogas have been studied. Results showed that CuO/γ-Al2O3 is able to remove CH3SH to below 10 ppb at 250-400 °C and has a sulfur capacity of 0.056 mmol g-1 at 300 °C. Regarding to the desulfurization mechanism, it has been confirmed that the removal of CH3SH with CuO/γ-Al2O3 is based on chemical adsorption. In the desulfurization, CH4s dry reforming took place at above 250 °C, and the generated H2 and CO reduced CuO to Cu2O and Cu. Further, it was supposed that H2S generates through the hydrogenation of CH3SH at the presence of H2.

Operational Investigation of Multi Feed Amine Process Performance in Comparison with Conventional Process

The alkanolamines are the most generally accepted and widely used of the many available solvents for removal of acid gases from natural gas streams. Amongst different amine sweetening processes like conventional scheme, split flow, absorbers in series or parallel and multi feed, selecting the proper scheme has great impact on acid gas removal. Using multi feed scheme in Fajr-e-Jam gas refinery has provided the chance for better analysis of conventional and multi feed schemes. In current work, the most important parameters in gas sweetening refineries like CO2, H2S and mercaptan removal, caustic solution consumption and temperature distribution throughout the absorption column were investigated for sweetening trains utilizing DEA. For all the parameters mentioned above, multi feed scheme shows good acid gas removal capability and lower causted solution consumption compared to the conventional process with single feed.

매몰지 조기 안정화를 위한 유용 미생물의 효과에 관한 연구

본 연구를 통해 유용 미생물을 적용하여 악취 저감 효과 및 조기 안정화에 미치는 영향을 알아보고자 하였다. 유기물 분해능과 악취 제어능이 뛰어난 유용 미생물 KEM을 개발하고, 이미 현장에 사용 중인 EM과 바실러스를 각각 적용하였다. 랩 스케일의 매몰지 모형 반응기를 제작하여 유용 미생물을 각각 적용한 경우와 적용하지 않은 경우(미생물을 적용하지 않고 사체만 매몰한 경우, 배지만 적용한 경우, 사체만 적용한 경우)로 나누어 실험을 진행하였다. 주기적인 수분 공급을 해줌으로써 가축 사체의 분해속도가 빨라진 것을 확인하였고, 유용 미생물을 적용한 반응기의 사체분해속도가 대조군 보다 빠른 것을 확인하였다. 가스는 총 8개의 성분(암모니아, TMA, 황화수소, 메틸머캅탄, DMS, DMDS, <TEX>$CO_2$</TEX>, <TEX>$CH_4$</TEX>)을 중점적으로 분석하였으며, 그 결과 유용 미생물을 적용하였을 경우 암모니아와 메틸머캅탄에 대하여 악취 저감 효율을 보였다. 연구에 사용되었던 토양 내에 많은 토양 미생물과 가축 사체에도 많은 미생물들이 존재하고 있어, 유용 미생물을 투입하였을 때의 뚜렷한 차이는 볼 수 없었다. 그러나 일정 부분에 한하여 악취 저감 효과와 부패 속도를 증가시키는 효과를 확인 할 수 있었다. In this study, we have evaluated the effect of efficient microorganisms on odor-removal efficiency and early stabilization of the burial sites. We have developed an efficient microorganism designated as 'KEM' which have the ability to degrade organic compounds and remove odor effectively. Other efficient microorganisms already used on site, such as EM and Bacillus sp., were also compared. We preceded these experiment using lab-scale reactors under three conditions (control, only media and only body) and comparing the effect of with or without the application of tree efficient microorganisms separately. Analysis was focused on eight components (ammonia, TMA, <TEX>$H_2S$</TEX>, methyl mercaptan, dimethyl sulfide, dimethyl disulfide, <TEX>$CO_2$</TEX> and <TEX>$CH_4$</TEX>), and as a result, efficient microorganisms were shown efficiency in the removal of ammonia and methyl mercaptan. The applied KEM decayed up to 71.2% of the buried meat. We were unable to observe significant differences in microbial communities between efficient microorganisms-treated and non-treated reactors due to the large presence of microorganisms in both soil and carcasses. However, it was possible to observe the effect on odor control and decay rate through the application of efficient microorganisms.