H2S Permeability Research Articles

Rational design of melamine-crosslinked poly(ethylene glycol) membranes for sour gas purification

Natural gas accounts for about a quarter of the world's energy consumption; however, most of the current natural gas reservoirs are sour. Sour natural gas containing significant amounts of hydrogen sulfide (H2S) along with carbon dioxide (CO2) must be purified to meet the strict requirements for transportation and storage in the industry. Sour natural gas purification involves two steps: acid gas removal (AGR) and acid gas enrichment (AGE), which currently use highly energy-intensive technologies. Membrane separation represents the most attractive technology to lower the operating cost and carbon footprint of these large processes. Guided by density functional theory (DFT) calculations, we rationally designed a crosslinked poly(ethylene glycol) (PEG) membrane for AGR and AGE applications. Specifically, PEG-bisazide monomers were crosslinked with a novel trialkyne-functionalized H2S-philic melamine via azide-alkyne cycloaddition click chemistry. The developed membranes were characterized and tested for (H2S + CO2)/CH4 and H2S/CO2 separations under realistic industrial conditions, targeting the AGR and AGE applications, respectively. These novel membranes achieved high H2S permeability while maintaining attractive H2S/CO2 selectivity.

Engineering highly reversible hydrogen bonding interaction in pebax/deep eutectic solvent blended membranes for efficient separation of H2S from CO2 and CH4

Removal of H2S and CO2 is a key step for natural gas upgrading. However, further separating H2S/CO2 remains challenging as they are both acid gas with similar kinetic diameters, incurring complex processes and high cost for recovering H2S as sulfur resource. Herein we reported for the first time the introduction of highly reversible hydrogen bonding into Pebax/deep eutectic solvent (DES) blended membranes comprising 1-ethyl-3-methylimidazolium chloride ([Emim]Cl)-based DESs for selectively separating H2S from CO2 and CH4. The successful fabrication of Pebax/DES membranes was confirmed by various characterizations. Benefitting from the highly reversible DES–H2S hydrogen bonding interaction, the H2S permeability, H2S/CO2 and H2S/CH4 selectivity for single gas tests are high up to 1829 Barrer, 14.35 and 242.0, respectively. Based on solution-diffusion data, the acidic [Emim]Cl/levulinic acid (Lev) DESs are found to be the most efficient owing to the moderate DES–H2S hydrogen bonding interaction and thus fast H2S diffusion, which was also confirmed by quantum chemical calculations coupled with visual study of weak interactions. Permeation test of mixed gas shows that Pebax/DES blended membranes can steadily and efficiently separate H2S/CO2/CH4 (3/3/94 vol%) ternary gas, with 1450 Barrer of H2S permeability, 34.5 of H2S/CO2 selectivity and 160 of H2S/CH4 selectivity obtained, which may indicates the applicability of these materials in desufuration of natural gas. To summarize, this work demonstrated the vital role of DES–H2S hydrogen bonding interaction in dominating H2S permeation, which may provide an easy but effective way for fabricating high-performance H2S sepration membranes.

Performance and stability of cellulose triacetate membranes in humid high H2S natural gas feed streams

The current study aims to provide a thorough understanding of the separation performance of the cellulose triacetate (CTA) membrane material in humid high H2S natural gas feed streams. A systematic study of the gas separation performances of CTA polymers has been carried out in self-standing symmetric films and asymmetric hollow fiber membranes. The separation performance in H2S-containing mixtures (CH4/CO2/H2S, 80/5/15 mol%) were evaluated at 30 and 50 °C at 20, 35 and 50 bar, including higher hydrocarbons (butane and toluene) in the presence of various levels of humidity, up to 4500 ppm or 80 % RH, depending on conditions of temperature and pressure. For the first time, the effect of these contaminants and humidity together under sour gas conditions has demonstrated the promising stability of CTA membrane separation performance, both in terms of H2S permeability and H2S/CH4 selectivity. The improvement in H2S permeability is due to a combination of H2S plasticization and competitive sorption making this phenomenon even more attractive and worth studying further.

Modified CARDO-Based Copolyimides with Improved Sour Mixed-Gas Permeation Properties

Chemical modification is an interesting tool to introduce functional groups into polymers’ backbones to tailor their properties in a desired fashion. Polymers used in membrane-based gas separation applications need to possess high gas permeability and selectivity during mixed-gas separation under harsh operational conditions of pressure and temperature. Herein, we report the modification of three copolyimides containing the moiety 9,9-bis(4-aminophenyl)fluorine (CARDO) through Friedel–Crafts alkylation to introduce bulky tert-butyl groups into their backbones. Membranes prepared from the modified polymers were evaluated using pure- and sweet mixed-gas under aggressive feed pressures. Based on the promising results obtained, a selected copolyimide was subjected to sour mixed-gas separation under feed pressures up to 500 psi. Mixed-gas separation studies, especially those containing hydrogen sulfide, are of great interest to develop membranes for use in sour natural gas reserve treatment. For example, the H2S and CO2 permeability coefficients of 6FDA-Durene/6FDA-CARDO(t-Bu) at 500 psi were recorded as 456 and 238 Barrer, respectively, where the H2S/CH4 and CO2/CH4 are 20.4 and 10.6, respectively. The obtained results are very promising and even superior to many glassy polymers reported previously. This work represents an example of the benefit of chemical modification on polymers to tailor their structure–property relationship. Future works will be focused on the fabrication and testing of asymmetric or composite hollow fibers to imitate the membrane modules used industrially.

Hydrogen sulfide mix gas permeation in Aquivion® perfluorosulfonic acid (PFSA) ionomer membranes for natural gas sweetening

Permeation tests of CO2/CH4 and H2S/CH4 mixtures in a commercial Perfluorosulfonic acid membrane, Aquivion® E87-12S, were carried out at different temperatures, namely 27, 35 and 50 °C, and at relative humidity (RH) ranging from 20 to 95%. A purposely modified experimental set up was used to allow mixture testing in a fixed volume variable pressure permeometer.The results confirmed the major influence of water content on the gas permeation behavior in PFSA as permeability strongly increased with RH. CO2 and CH4 results confirmed experimental data already available in the open literature, while, for H2S, permeability increased from a value of 17 Barrer measured at 27 °C and 20%RH up to 450 Barrer at the same temperature but at 95%RH. The selectivity with respect to methane also increased with RH, going from 7 to 36 at the same temperature and in the same RH range.The temperature's increase also improved H2S permeability, which reached 512 Barrer at 50 °C and 85%RH, but slightly decreased selectivity towards methane which in the same conditions was limited to 23.A simple model, already used to describe the permeation behavior of other different gases in PFSA, also proved to be able to fit experimental data of H2S with slight changes of the adjustable parameters.

Hydrogen sulphide sensitivity and tolerance in genetically distinct lineages of a selfing mangrove fish (Kryptolebias marmoratus).

Mangroves are critical marine habitats. High hydrogen sulphide (H2S) is a feature of these important ecosystems and its toxicity creates a challenge for mangrove inhabitants. The mangrove rivulus (Kryptolebias marmoratus) is a selfing, hermaphroditic, amphibious fish that can survive exposure to 1116μM H2S in the wild. These fish rely on cutaneous respiration for gas and ion exchange when emerged. We hypothesized that the skin surface is fundamentally important in H2S tolerance in these mangrove fish by limiting H2S permeability. To test our hypothesis, we first disrupted the skin surface in one isogenic lineage and measured H2S tolerance and sensitivity. We increased water H2S concentration until emersion as a measure of the ability to sense and react to H2S, which we refer to as sensitivity. We then determined H2S tolerance by preventing emersion and increasing H2S until loss of equilibrium (LOE). The H2S concentration at emersion and LOE were significantly affected by disrupting the skin surface, providing support that the skin is involved in limiting H2S permeability. Capitalizing on their unique reproductive strategy, we used three distinct isogenic lineages to test the hypothesis that there would be genetic differences in H2S sensitivity and tolerance. We found significant differences in emersion concentration only among lineages, suggesting a genetic component to H2S sensitivity but not tolerance. Our study also demonstrated that external skin modifications and avoidance behaviours are two distinct strategies used to tolerate ecologically relevant H2S concentrations and likely facilitate survival in challenging mangrove habitats.

Pore-Size-Tuned Graphene Oxide Membrane as a Selective Molecular Sieving Layer: Toward Ultraselective Chemiresistors.

Conventional graphene oxide (GO)-based gas membranes, having a narrow pore-size range of less than 0.3 nm, exhibit limited gas molecular permeability because of the kinetic diameters of most volatile organic and sulfur compound (VOCs/VSCs) molecules being larger than 0.3 nm. Here, we employ GO nanosheets (NSs) with a tunable pore-size distribution as a molecular sieving layer on two-dimensional (2D) metal oxide NSs-based gas sensors, i.e., PdO-sensitized WO3 NSs to boost selectivity toward specific gas species. The pore size, surface area, and pore density of GO NSs were simply manipulated by controlling H2O2 concentration. In addition, the pore size-tuned GO NSs were coated on cellulose filtering paper as a free-standing nanoporous membrane. Holey GO membrane showed a highly selective H2S permeability characteristic, exhibiting superior cross-selectivity to CH3COCH3 (0.46 nm), C2H5OH (0.45 nm), and C7H8 (0.59 nm) with larger kinetic diameters compared with H2S (0.36 nm). Such pore-size-tuned GO nanoporous layer is scalable and robust, highlighting a great promise for designing low cost and highly efficient gas-permeable membrane for outstanding selective gas sensing platform.

Surprising plasticization benefits in natural gas upgrading using polyimide membranes

Hydrogen sulfide (H2S) and carbon dioxide (CO2) are acid gases that must be removed from natural gas prior to transmission and use. Here, we report the H2S/CH4 and CO2/CH4 separation performance of two polyimide membranes, i.e. 6FDA-DAM and 6FDA-DAM/DABA (3:2) for various realistic gas compositions and conditions. So-called plasticization effects of the polyimides are generally viewed as negative features when using such membranes, but we report important applications where H2S is present in the feed and the polyimide membrane plasticization is actually a tool for performance optimization. In fact, we identify cases where polyimide plasticization can provide large performance benefits for H2S/CH4 separations. We further analyze the transport mechanisms in terms of sorption and diffusion factors to understand this surprising discovery for various important feeds and conditions. The 6FDA-DAM membrane showed H2S permeability of 495 barrer and H2S/CH4 selectivity of ~31 with CO2 permeability of 301 barrer and CO2/CH4 selectivity of ~19 for a 20% H2S, 20% CO2 and 60% CH4 feed at 35 °C and 46 bar. Such CO2/CH4 performance and higher H2S/CH4 separation performance for aggressive high pressure feeds exceeds that of rubbery polymers, making the glassy materials ideal for processing natural gas feeds containing H2S and CO2.

Fluorinated copolyimide membranes for sour mixed‐gas upgrading

ABSTRACTThree random and two block 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA)‐based copolyimides with different 6FpDA:Durene molar ratio varying from 25 to 80% were prepared and characterized. The pure‐gas permeation data of their membranes were investigated at 100 psi and 22 °C. The CO2/CH4 ideal selectivity coefficient increased to around 47 with the increase of the 6FpDA content to 80% in the copolymer backbone while the CO2 permeability coefficient found to be the highest (378 barrer) with highest Durene content copolymer. Based on its attractive pure‐gas permeation properties(CO2/CH4 = 47), 6FDA‐6FpDA/6FDA‐Durene (4:1) block copolyimide was selected for further analyses, where the effect of pressure and temperature on its gas transport properties was evaluated. Furthermore, the mixed‐gas permeation properties were investigated using multicomponent sweet and sour gas mixtures prepared from N2 (30% or 10%), CH4 (59%), C2H6 (1%), CO2 (10%), and H2S (0% or 20%)accordingly. The sweet mixed‐gas CO2/CH4 selectivity and CO2 permeability coefficients of 6FDA‐6FpDA/6FDA‐Durene (4:1) are around 39 and 45 barrer, respectively, at elevated pressure (800 psi). The polymer, however, showed nonideal behavior when subjected to high H2S‐content gas mixture (20 vol. % H2S), where the CO2/CH4 selectivity value dropped to around 21 and the H2S/CH4 selectivity coefficient is 13. The CO2 and H2S permeability coefficients are 42 and 26 barrer, respectively, at an upstream pressure up to 500 psi. When plotted on the combined acid gas permeability‐selectivity curve, the polymer separation efficiency was nearby the high‐performing polymers reported in the literature, and way superior to the industrial standard glassy polymer, cellulose acetate, used currently in gas separation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48336.

Molecular Simulations and Experimental Characterization of Fluorinated Nitrile Butadiene Elastomers with Low H2S Permeability

The elastomer seals that are used in the processing of sour gas in the oil and gas industry must be able to withstand chemical degradation by corrosive materials such as hydrogen sulfide present in the sour gas. Nitrile rubbers, including hydrogenated nitrile butadiene (HNBR), are commonly used because they have low glass transition temperatures, good low-temperature sealing ability, and excellent resistance to swelling by hydrocarbons. They are, however, prone to chemical modifications, including chain scission, cross-linking, and sulfur incorporation, that result in changes in mechanical properties after contact with H2S. Fluoroelastomers are promising alternatives but have higher glass transition temperatures than nitrile rubbers, which affect their low-temperature performance. The approach of free-radical grafting of a semifluorinated alkyl methacrylate, 1H,1H,2H,2H-perfluorooctyl methacrylate (F6H2MA), to HNBR, to improve its resistance to H2S was investigated. The effects of grafting density of F6H2MA on the solubilities and diffusion coefficients of H2S, and carbon dioxide, which is also present in sour gas, were studied using molecular dynamics and Monte Carlo simulations. The influence of acrylonitrile concentration in the copolymer was characterized. Simulated dilatometry and differential scanning calorimetry measurements showed that the grafting of F6H2MA to HNBR did not result in a significant increase in the glass transition temperature of the copolymer. H2S permeability through the fluorinated HNBR showed a significant decrease with an increase in F6H2MA concentration. The results of molecular simulations were corroborated by measurement of mechanical properties of elastomer samples aged in a sour-gas environment at 250 °F and 1000 psig for 24 h. Gravimetric and volumetric swelling, as well as mechanical properties of the aged samples, was measured for comparison with the original unaged samples. The degrees of swelling and mechanical property deterioration after aging were significantly suppressed by grafting HNBR with even low concentrations of the semifluorinated methacrylate.

Pure - and sour mixed-gas transport properties of 4,4′-methylenebis(2,6-diethylaniline)-based copolyimide membranes

Three aromatic 6FDA-Durene/MDEA random copolyimides with different Durene:MDEA molar ratios (3:1; 1:1 and 1:3) were synthesized, and pure gas permeation properties through their dense films were investigated. Compared to their corresponding homopolymers (6FDA-MDEA and 6FDA-Durene), the copolymers exhibit significant improvement in gas separation performance, as the membranes display improved gas transport properties. For example, for pure gas, the CO2 permeability for 6FDA-Durene/MDEA (3:1) is around 234 Barrer and CO2/CH4 selectivity equal to 17.8 obtained at 22 °C and feed pressure of 100 psi. In addition, for sweet gas mixture consisting of 10, 59, 30 and 1 vol% CO2, CH4, N2 and C2H6, respectively, the 6FDA-Durene/MDEA (1:3) copolyimide membrane shows CO2 permeability of 73 Barrer and CO2/CH4 selectivity of about 24 at an elevated pressure of 800 psi. For a sour gas mixture with high H2S content (20 vol % H2S in the feed gas), the membrane exhibits H2S/CH4 selectivity of 21; and H2S permeability of 112 Barrer. The transport properties of the herein reported membrane are similar to or even better than the performance exhibited by some polymeric membranes reported in the literature.

Acidic Gases Separation from Gas Mixtures on the Supported Ionic Liquid Membranes Providing the Facilitated and Solution-Diffusion Transport Mechanisms.

Nowadays, the imidazolium-based ionic liquids containing acetate counter-ions are attracting much attention as both highly selective absorbents of the acidic gases and CO2 carriers in the supported ionic liquid membranes. In this regard, the investigation of the gas transport properties of such membranes may be appropriate for better understanding of various factors affecting the separation performance and the selection of the optimal operating conditions. In this work, we have tested CH4, CO2 and H2S permeability across the supported ionic liquid membranes impregnated by 1-butyl-3-methylimidazolium acetate (bmim[OAc]) with the following determination of the ideal selectivity in order to compare the facilitated transport membrane performance with the supported ionic liquid membrane (SILM) that provides solution-diffusion mechanism, namely, containing 1-butyl-3-methylimidazolium tetrafluoroborate (bmim[BF4]). Both SILMs have showed modest individual gases permeability and ideal selectivity of CO2/CH4 and H2S/CH4 separation that achieves values up to 15 and 32, respectively. The effect of the feed gas mixture composition on the permeability of acidic gases and permeselectivity of the gas pair was investigated. It turned out that the permeation behavior for the bmim[OAc]-based SILM toward the binary CO2/CH4, H2S/CH4 and ternary CO2/H2S/CH4 mixtures was featured with high acidic gases selectivity due to the relatively low methane penetration through the liquid phase saturated by acidic gases.

Novel Application of a Polyurethane Membrane for Efficient Separation of Hydrogen Sulfide from Binary and Ternary Gas Mixtures

AbstractRecently we introduced a new polyurethane (PU) membrane synthesized from polypropylene glycol (PPG), hexamethylene diisocyanate (HDI), and 1, 4‐butane diol (BDO), and then studied the performance of the membrane for CO2 removal. This paper presents a novel application of the PPG‐HDI‐BDO membrane for separation of H2S in binary and ternary gas mixtures. The gas transport properties of the membrane in binary H2S/CH4 and ternary CH4/CO2/H2S gas mixtures at different temperatures, pressures, and gas compositions are investigated. Permeation tests show that the membrane has a high H2S/CH4 selectivity (27.2), an outstanding H2S permeability of 790 Barrer, and a remarkable CO2 permeability of 473 Barrer. The H2S permeability of 790 Barrer is the highest reported to this date for all PU membranes. The H2S permeability and H2S/CH4 selectivity of the membrane increases with temperature. As the operating pressure increases, the CO2/CH4 and H2S/CH4 selectivities of the membrane increases. H2S and CO2 permeabilities and H2S/CH4 and CO2/CH4 selectivities increase, as the H2S content of the feed increases. Solubility is most likely the dominant mechanism of gas permeation in this membrane. As the CO2 content of the feed stream increases, the H2S permeability and H2S/CH4 selectivity of the membrane decreases. The membrane has maximum H2S/CH4 selectivities of 27.4 in binary H2S/CH4 (with 0.075 mol% H2S) and 27.2 in ternary CH4/CO2/H2S (with 0.66 mol% H2S).

High pressure pure- and mixed sour gas transport properties of Cardo-type block co-polyimide membranes

Multi-block co-polyimides 6FDA-CARDO/6FDA-Durene with varying segmental lengths were synthesized and pure and mixed sour gas transport properties through dense membranes were investigated as function of feed pressure, temperature and gas composition. Pure gas measurement indicated that block co-polyimide 6FDA-CARDO/6FDA-Durene (2500/2500) membrane exhibits high permeation properties and separation characteristics with CO2 permeability and CO2/CH4 selectivity of up to 239 barrer and 28 respectively. The block co-polyimide also showed excellent performance under harsh sour gas environment (i.e. high H2S content of up to 36 vol% and feed pressure of up to 55 bar for a gas mixture consisting of CO2, CH4, N2, C2H6 and H2S). At 36 vol% H2S, the membrane exhibits H2S permeability and H2S/CH4 selectivity of up to 275 barrer and 24 respectively. These values and separation performance exhibited by the co-polyimide are comparable and very competitive even, as compared to the values obtained in some of the high performance polymeric membranes that have been reported in the literature. The stability of the block co-polyimide 6FDA-CARDO/6FDA-Durene membrane under these aggressive environments is quite impressive.

Synthesis and characterization of ionic liquid based mixed matrix membrane for acid gas separation

This work evaluates the potential of a mixed matrix membrane synthesized with 1-ethyl-3-methylimmidazolium-ethylsulphate [EMIM][EtSO4] a common ionic liquid (IL) blended with poly (ether-block-amide) (PEBA) elastomer to separate either hydrogen sulphide (H2S) or carbon dioxide (CO2) or both acid gasses (H2S and CO2) from its streams. Layer-by-layer deposition method was used to synthesize the defect-free blended membrane. The prepared membranes were characterized by field emission scanning electron microscopy (FESEM), fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) for physical and thermal properties. Several experiments were conducted by varying pressure and ionic liquid concentration at normal temperature for pure gases (H2S/CO2/CH4/Air). The presence of ionic liquid (5 wt%) shows higher H2S permeability of 540 barrer and a comparatively low CO2 permeability of 55 barrer at pressure of 7 kg/cm2 through the blended membrane due to higher H2S solubility (1.5 times more than CO2) in the same IL. The trend of permeability for different single gases was observed in the pattern following: H2S > CO2>Air > CH4. Ideal selectivity was 66.0 for H2S/CH4 and 24.0 for H2S/Air which is much higher than those for CO2 binary mixture such as CO2/CH4 (4.6) and CO2/Air (2.4). The addition of ionic liquid in the membrane matrix enhances the permeability of acid gases compared to pure PEBA membrane. Robeson’s diagram also shows the promising trends for the experimental points either crossing the upper bound line or getting nearer which highlight the pivotal role of IL in blended membrane.

Permeation and separation of SO2, H2S and CO2 through thermally rearranged (TR) polymeric membranes

Abstract The permeabilities of sulfur dioxide and hydrogen sulfide are reported here for two copolymer based TR membranes, as a function of feed partial pressure and temperature. The two TR membranes are formed from the precursor co-polyimide 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 3,3′-dihydroxyl-4,4′-diaminobiphenyl (HAB) and 2,4,6-trimethyl-m-phylenediamine (DAM) (6FDA-HAB-DAM), where one of the membranes undergoes crosslinking with 3,5-diaminobenzoic acid (DABA) during TR. It was observed that SO2 permeability decreased with increasing partial pressure and temperature in both TR membranes. This is indicative that SO2 permeability is dominated by SO2 solubility within the TR membranes, and is attributed to the high condensability of SO2. Both polymeric membranes displayed selectivity for SO2 against CO2, with separation performance similar to other classes of polymeric membranes. H2S permeability was observed to decrease with increasing partial pressure and temperature for the cross-linked TR (XTR) membrane. The non-cross-linked TR membrane displayed constant H2S permeability with pressure and permeability increased with increasing temperature. Hence, permeability within the XTR membrane was H2S solubility dominated, while in the non-crosslinked TR membrane permeability was H2S diffusivity dominated. This was attributed to the difference in free volume and cavity size distribution in the TR membrane as a result of crosslinking. It was observed that both membranes displayed H2S/CO2 selectivity of less than one, indicative that they favor CO2 over H2S.

Performance enhancement of vertically aligned carbon nanotube membranes for separation of binary mixtures of H2S/CH4 using different amine groups

Synthesis and performance evaluation of vertically aligned carbon nanotube membranes functionalized with different amine groups in order to separate H2S from binary mixtures of H2S/CH4 were experimentally studied. For increasing the performance of the membrane, it was functionalized with butylamine, sec-butylamine, dodecylamine and octadecylamine. The effect of using linear amine groups with different carbon chain length and branched amine on increase of H2S permeability and selectivity of membrane was studied. The results showed that using linear amine with shorter carbon chain length is preferred to other amine groups, and the membrane functionalized with butylamine has the maximum selectivity and permeation values for the H2S. These values are reported to be 2.98 and 2.3 times those of obtained for the membrane with no functional group. The results also reveal that diffusivity of a N2 single gas is 3.22 and 1.72 times of Knudsen’s diffusion before and after functionalization, respectively.

Amperometric cell for subcutaneous detection of hydrogen sulfide in anesthetized experimental animals

Hydrogen sulfide (H2S) is a toxic gas. It has been recognized that H2S evolving in biochemical reactions in living organisms has an important role in different physiologic processes. Nowadays, H2S is known as an endogenous messenger molecule. Natural sulfurous spring water has been proved beneficial in the therapy of diseases of the skin and other organs (Boros et al ). In vivo real-time detection of local H2S concentration is an important but challenging task.We developed a two-electrode amperometric cell for selective subcutaneous detection of H2S in anesthetized mice. The cell is a small size implantable gas sensor containing a platinum disc anode and a silver cathode. The selectivity is provided by a membrane permeable only by gases. There is a buffered reversible electrochemical mediator solution in an oxidized form inside the cell. As gaseous H2S penetrates into the cell the mediator is reduced, and +0.4 V versus the reference is employed on the platinum working electrode. The reduced mediator is oxidized on the anode surface. The current provides an analytical signal representing the concentration of H2S.Appropriate shape, size and membrane material were selected, and optimal working parameters—such as mediator concentration, pH and cell voltage—were determined in vitro. The lower limit of detection in the stirred sample solution at pH = 5.5 was as small as 9.4 × 10−7 M and a dynamic concentration range of 0–6 × 10–4 M could be achieved.The detecting surfaces of the cell were covered with freshly dissected mouse skin to test dermal H2S permeability. In other experiments, the cell was implanted subcutaneously in an anesthetized mouse and the animal was submerged in a buffer solution containing different concentrations of H2S so that the skin surface over the sensor was covered by the solution. Measurements of subcutaneous H2S concentration were taken. The experiments clearly proved that H2S diffuses through the skin of the live mouse.

Experimental and Modelling Study of Storage of CO2 and Impurities in a Depleted Gas Field in Northeast Netherlands

Abstract In order to investigate the effects of impurities on subsurface storage of CO2, experiments were carried out on Permian Rotliegend reservoir and Zechstein caprock core samples at subsurface conditions of 300 bar and 100°C. The experiments were performed in the presence of brine and the following gas compositions: CO2, CO2+5000 ppm H2S, CO2+100 ppm H2S and CO2+100 ppm SO2 for a 30 day duration. Following CO2 injection, permeability of the reservoir and caprock samples increased by 10-30% and by a factor of 3-10 respectively. After co-injection of 5000 ppm H2S permeability of both reservoir and caprock samples reduced significantly. When the concentration of H2S was reduced to 100 ppm, minimal variation of permeability took place because the dissolution of minerals was balanced with the precipitation of secondary phases. In the case of co-injection of 100 ppm SO2 permeability of reservoir samples increased by a factor of 1.18 to 2.2. In the caprock samples permeability changed by a factor of 0.8 to 23. In addition, in order to determine long term (>100 years) interaction between CO2 and the reservoir mineralogy we need to rely on modelling programs. This requires accurate and fit for purpose input parameters, associated with the lithological composition of reservoirs and seals at the storage site. For this purpose, we specifically focused on the reactive surface area of minerals, which we measured by scanning electron microscopy. Using the range of measured reactive surface area of minerals as an input in the modelling software, we could obtain the distribution of the sequestered CO2 as a mineral (3-9 kg of CO2/m3).

OP02 Amperometric microcell for subcutaneous detection of hydrogen sulfide in anesthetized experimental animals

It has been recognized that hydrogen sulfide evolving in biochemical reactions in living organisms has important roles in different physiologic processes. In these days, hydrogen sulfide is known as an endogenous messenger molecule. Several natural sulfurous spring waters have been proved beneficial for treating different skin and internal diseases. In vivo detection of local, instantaneous hydrogen sulfide concentration is an important, but challenging task in certain life science experiments. In our studies an amperometric two electrode micro cell has been developed for selective subcutaneous detection of hydrogen sulfide in anesthetized experimental mice. The cell is a small size implantable gas sensor containing a platinum micro disc anode and a silver cathode. The selectivity is provided by a membrane permeable only for gases. Inside the cell a buffered solution of oxidized form of an electrochemically reversible mediator material is confined. The hydrogen sulfide gas getting into the lumen cell reduces the oxidized form of the mediator. An appropriate constant potential is employed between the two electrodes. The reduced mediator is oxidized on the anode surface. The current is the analytical signal for reflecting the hydrogen sulfide concentration. Appropriate shape, size and membrane material were selected and optimal working parameters, like mediator concentration, pH and cell voltage were worked out in vitro. In stirred sample solution with pH = 5.5 lower limit of detection as small as 0.3 ppm could be achieved with dynamic concentration range of 0–20 ppm could be achieved. The cell surface was covered with freshly dissected mouse skin in order to test the H2S permeability of it. Furthermore, the cells were implanted subcutaneously in the anesthetized mice and bathing them in buffer solution (37 °C, pH = 5.5) containing different concentrations of H2S measurements were made. The experiments clearly proved that considerable amount of H2S absorbs through the skin of bathing living mice.