Adsorption Of Carbonyl Sulfide Research Articles

Oxygen vacancies-promoted removal of COS via catalytic hydrolysis over CuTiO2-δ nanoflowers

Catalytic hydrolysis was considered as an efficient technology to remove carbonyl sulfide (COS). The introduction of oxygen vacancy (Ov) is a promising strategy to improve the catalytic performance of COS hydrolysis by promoting the adsorption and activation of reactants. Herein, we reported a Cu-doped TiO2 nanoflower with abundant oxygen vacancies for COS hydrolysis. The Cu species successfully entered the crystal lattice of TiO2 and induced more oxygen vacancies than pure TiO2. The Ov sites can effectively reduce the adsorption and activation energy of COS and H2O. Benefiting from the ample Ov sites, the resulting CuTiO2-δ-F achieved nearly 100 % COS conversion at 70 °C and 93.5 % H2S yield at 130 °C, which is better than that of pure TiO2. Furthermore, in situ FT-IR measurements and density functional theory (DFT) calculations were performed to reveal the reaction pathway in COS hydrolysis.

CuY@NiAl-Layered double oxides bi-functional composites for “Catalytic–Adsorptive” removal of carbonyl sulfide

Carbonyl sulfide (COS) removal processes, typically containing catalytic hydrolysis and subsequent capture of hydrogen sulfide (H2S) generated, are energy-intensive and of high complexity. Bi-functional materials with the capability for synergistic catalytic conversion of COS and subsequent adsorption capture of H2S can enable effective removal of COS at low energy cost. Here, we report the development of a bi-functional CuY@NiAl-LDO composite material with integrated catalytic conversion of COS and adsorptive separation of H2S with high efficiency and stability. Fundamental material characterizations elucidate that the CuY@NiAl-LDO composite materials feature a core–shell structure. Coupled dynamic breakthrough experiments and DFT simulations highlight the unique synergistic “catalytic–adsorptive” effect between CuY and NiAl-LDO in the COS removal processes. Specifically, compared with the pure zeolite CuY and NiAl-LDO, the CuY@NiAl-LDO composites present significantly higher COS removal performance. The highest degree of desulfurization was observed on CuY@NiAl-LDO(46 %) at 80 °C with a breakthrough sulfur capacity of 20.57 mg-S/g and no detectable H2S in the outlet gas. In sum, this study highlights the synergistic “catalytic–adsorptive” mechanism of the bi-functional CuY@NiAl-LDO core–shell composite in desulfurization. The insights obtained may benefit chemical engineers by providing a new strategy for the development of multi-functional desulfurization materials.

Capture of carbonyl sulfide trace from natural gas by adsorption on zeolitic Nanostructure: Monte Carlo molecular simulation

The economic and environmental challenge for the oil and gas industries is to eliminate carbonyl sulfide (COS) from natural gas selectively. This compound can lead to corrosion and environmental damage, even when it is present in small amounts. The zeolites have been known as the appropriate adsorbent for COS. Grand Canonical Monte Carlo (GCMC) simulation has been used to explore the suitability of zeolite frameworks with different topologies on the adsorption and separation properties of mixtures containing industrial concentrations of COS in order to overcome the experimental tests that are difficult to handle. The adsorption isotherms for pure COS and COS/methane mixture on purely siliceous zeolites such as BEA, FAU, LTL, MFI, and MOR have been recorded at 298 K within a pressure range of 0–100 kPa. MFI zeolite, with its high adsorption capacity and isosteric heat, has been identified as the most suitable candidate for COS adsorption due to its ideal pore size and shape. Examining the density distribution snapshots reveals the preferred locations of zeolites for the COS adsorption. The findings could be systematically used in various case studies, thereby providing insights into selecting the best zeolitic nanostructure for the industrial removal processes of COS.

Enhancing catalytic hydrolysis activity of ZnNiAl hydrotalcite-like compounds-derived oxides using rare earth metals

Efficient catalysts are highly desirable for the simultaneous removal of hydrogen cyanide (HCN) and carbonyl sulfide (COS) to meet the increasingly stringent emission standards and achieve cleaner production. In this study, ZnNiAl hydrotalcite-like compounds (HTLCs)-derived oxides doped with a series of rare earth metals, such as cerium (Ce), gadolinium (Gd), and yttrium (Y), were synthesized and used for the simultaneous hydrolysis of HCN and COS. The results demonstrated that the chemical state and electronic structure of ZiNiAl were changed by Ce doping because of the incorporation of Ce into the nickel oxide (NiO) network. Thus, abundant active species for the adsorption and dissociation of HCN and COS, including chemically adsorbed oxygen and strong basic sites, were produced by Ce doping. Meanwhile, the well-developed mesoporous structure provided accessibility to the active sites. As a result, Ce doping significantly enhanced the catalytic performance of ZnNiAl. Furthermore, the mechanisms of HCN and COS hydrolysis over Ce-ZnNiAl and their deactivation were proposed. This study provides a novel route for efficiently eliminating HCN and COS in diverse industrial processes.

Lanthanum–bismuth mixed oxide catalyst with improved activity for carbonyl sulfide hydrolysis

The presence of carbonyl sulfide (COS) in industrial tail gas poses considerable risks to human health and ecosystems. Catalytic hydrolysis is efficient in COS removal, yet developing high-performance catalysts at low temperatures remains challenging. In this work, we designed novel nanorod-like lanthanum-bismuth (La-Bi) mixed oxides for the catalytic hydrolysis of COS. The COS hydrolysis activity of the Bi-doped catalyst was significantly improved as compared to the bare La oxide. The catalysts with various La/Bi ratios were thoroughly analyzed by microscopic and spectroscopic techniques to elucidate their structural and chemical properties. The results indicated that the Bi doping into the La oxide enhanced the basicity and electron transfer of the catalyst, leading to improved hydrolysis activity. A reaction pathway for the COS catalytic hydrolysis on La-Bi mixed oxide was proposed, in which COS adsorption was significantly strengthened due to enhanced basicity, and thereby the formation of intermediates such as HCO3− and HSCO2- was facilitated. In addition, the La-Bi mixed oxide catalyst demonstrated excellent sulfur tolerance and stability in long-term testing using simulated industrial gas.

Carbonyl sulfide and dimethyl sulfide adsorption studies on novel square-octagon antimonene sheets – A first-principles study

Using the first-principles study, we studied the structural and electronic attributes of square-octagon antimonene nanosheet (so-SbNS). Firstly, the structural and thermal stability of so-SbNS is ascertained. The energy band gap of so-SbNS is recorded as 0.814 eV. Furthermore, the so-SbNS is deployed as base material to adsorb carbonyl sulfide (COS), and dimethyl sulfide (DMS) molecules. The physical adsorption of COS and DMS molecules is noticed on so-SbNS. The so-SbNS behaves as the acceptor of electrons observed from charge transfer and electron density difference results. The band structure and projected density of states changes are noticed due to COS and DMS adsorption on so-SbNS. The results convey that so-SbNS is new material towards the detection of COS and DMS molecules emitted from solid waste.

Contribution of Na/K Doping to the Activity and Mechanism of Low-Temperature COS Hydrolysis over TiO2-Al2O3 Based Catalyst in Blast Furnace Gas

As an organic sulfur pollutant generated in blast furnace gas, carbonyl sulfide (COS) has attracted more attention due to its negative effects on the environment and economy. The TiO2-Al2O3 composite metal oxide (Ti0.5Al) with uniformly dispersed particles was prepared by the co-precipitation method. And on this basis, a series of Na/K-doped catalysts were prepared separately. The activity evaluation results showed that the introduction of Na/K significantly improved the low-temperature COS hydrolysis activity, which exhibited a COS conversion of 98% and H2S yield of 95% at 75 °C with 24,000 h–1. And K showed a better promoting effect than Na. Brunauer–Emmett–Teller (BET) results revealed the increased mesopore proportion of Na/K-modified catalysts. X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that Na and K formed prismatic and nanorod-like structures, respectively. More weakly basic sites with enhanced intensity and decreased Oads/Olat content contributed to the excellent catalytic activity, as certified by the results of CO2 temperature-programmed desorption (CO2-TPD) and X-ray photoelectron spectroscopy (XPS). It was also proposed that the decrease of weakly basic sites ultimately deactivated catalyst activity. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) showed that the introduction of Na/K enhanced the dissociation of H2O, and the generated abundant hydroxyl groups promoted the adsorption of COS and formed surface transition species, such as HSCO2– and HCO3–.

The catalytic mechanism of intercalated chlorine anions as active basic sites in MgAl-layered double hydroxide for carbonyl sulfide hydrolysis.

In order to make clear the role of intercalated anions in layered double hydroxides (LDHs) for catalytic hydrolysis of carbonyl sulfide (COS), the adsorption and reaction characteristics of COS over the simple Mg2Al-Cl-LDH model catalyst were studied by both theoretical and experimental methods. Density functional theory (DFT) calculations by CASTEP found that the chloride ions in LDH function as the key Brønsted base sites to activate the adsorbed H2O with enlarged bond length and angle, facilitate the dissociative adsorption of intermediates including mono-thiocarbonic acid (MTA) and hydrogen thiocarbonic acid (HTA), and participate in the formation of transient states and subsequent hydrogen transfer process with decreased energy barriers during COS hydrolysis. COS hydrolysis will preferentially go through the dissociated intermediates of mono-thiocarbonates (MT) and hydrogen thiocarbonates (HT) with dramatically decreased energy barriers, and the rate-determining step of COS hydrolysis over Mg2Al-Cl-LDH will be the nucleophilic addition of C=O in COS by H2O (Ea = 1.10 eV). The experimental results further revealed that the apparent activation energy (0.89 eV) of COS hydrolysis over Mg2Al-Cl-LDH is close to theoretical value (1.10 eV), and the accumulated intermediates of MT, HT, or carbonate were also observed by FT-IR around 1363 cm-1 on the used Mg2Al-Cl-LDH, which are well in accordance with the theoretical prediction. The demonstrated participation of intercalated chlorine anions in the evolution of intermediates and transient states as Brønsted base sites during COS hydrolysis will give new insight into the basic sites in LDH materials.

Boosting carbonyl sulfide catalytic hydrolysis performance over N-doped Mg-Al oxide derived from MgAl-layered double hydroxide

Carbonyl sulfide (COS), the organic sulfur generated in the chemical industry, has been receiving more attention due to its environmental and economic influence. In this study N-doped MgAl-LDO catalyst was successfully prepared and tested for the COS hydrolysis reaction at low temperature, it was observed that the N species can be formed both in surface and bulk. Moreover, the basicity property and the H2O adsorption–desorption property were remarkably improved due to the N-doping. Besides, the hydroxyl group can be formed more easily and more abundantly on N modified catalyst surface, which was beneficial to the COS adsorption and the remarkable improvement of catalytic performance. The catalytic hydrolysis performance can proceed for almost 1440 min without any deactivation at 70 °C. However, further increase of temperature was not beneficial to improve the catalytic performance due to the occurrence of H2S oxidation side reaction. Furthermore, it was revealed that the surface hydroxyl groups were responsible for the adsorption of COS and then the formed surface transitional species reacted with the H2O molecules. Hydrogen thiocarbonate and bicarbonate were the main reaction intermediate. The rate-determining step was IM6→IM7 i.e., a type transformation of bicarbonate.

Surface characterization of metal oxides-supported activated carbon fiber catalysts for simultaneous catalytic hydrolysis of carbonyl sulfide and carbon disulfide

The sol–gel method was used to synthesize a series of metal oxides-supported activated carbon fiber (ACF) and the simultaneous catalytic hydrolysis activity of carbonyl sulfide (COS) and carbon disulfide (CS2) at relatively low temperatures of 60°C was tested. The effects of preparation conditions on the catalyst properties were investigated, including the kinds and amount of metal oxides and calcination temperatures. The activity tests indicated that catalysts with 5 wt.% Ni after calcining at 400°C (Ni(5)/ACF(400)) had the best performance for the simultaneous catalytic hydrolysis of COS and CS2. The surface and structure properties of prepared ACF were characterized by scanning electron microscope-energy disperse spectroscopy (SEM-EDS), Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), carbon dioxide-temperature programmed desorption (CO2-TPD) and diffuse reflectance Fourier transform infrared reflection (DRFTIR). And the metal cation defects were researched by electron paramagnetic resonance (EPR) method. The characterization results showed that the supporting of Ni on the ACF made the ACF catalyst show alkaline and increased the specific surface area and the number of micropores, then improved catalytic hydrolysis activity. The DRFTIR results revealed that -OH species could facilitate the hydrolysis of COS and CS2; -COO and -C–O species could facilitate the oxidation of catalytic hydrolysate H2S. And the EPR results showed that high calcination temperature conditions provide more active reaction center for the COS and CS2 adsorption.

Adsorption of carbonyl sulfide on Pt-doped vacancy-defected SWCNT: A DFT study

Carbonyl sulfide (COS) is a dangerous gas produced from fossil fuel combustion and petrochemical procedures, so proper adsorbent and sensors are required for removal and detection. In this work, we study by Density Functional Theory methods the COS adsorption on a Pt-decorated vacancy-defected carbon nanotube, in order to evaluate the potential of this nanostructure as gas adsorbent or sensing material. First, we analyze the most stable configuration for Pt adsorption on the defective nanotube, obtaining a more favorable binding energy for a symmetric structure with equivalent CPt bonds. Next, several configurations are studied for COS adsorption on the Pt-doped nanotube. In the most stable systems, the adsorbate interacts with the Pt decoration through its C and S atoms, with adsorption energy values of about −2.7 eV. Overlap population and bonding order studies are also performed, showing a strong affinity between COS and the Pt-doped surface. Furthermore, an important electronic transfer from nanotube to the gas molecule was detected, which would indicate chemical adsorption. Density of states analysis also show a considerable stabilization of COS molecule after adsorption. Our study suggests that a Pt-doped carbon surface could act as a promising adsorbent and chemical sensor for COS gas removal or detection purposes.

Capturing ability for COS gas by a strong bridge bonding of a pair of potassium anchored on carbonate of activated carbon at low temperatures

To maximize the adsorption of COS (carbonyl sulfide) gas, activated carbon (AC) with a large surface area was modified with K as a low-cost adsorbent capable of bonding at low temperatures with the S in COS. The contents of AC and K were fixed at 80% and 20%, respectively. The COS gas was dynamically adsorbed by AC-K at an optimum temperature of 210 °C with a sulfur-adsorption capacity of 56.1 mg/g. The structure of the K adsorbent was confirmed as K2CO3 via X-ray diffraction and the K components were highly dispersed on the surface of the AC, as indicated by SEM and EDAX analyses. Furthermore, the correlation between the specific surface area of AC-K and COS adsorption was examined using FT-IR, XPS, and MASS analyses. The mechanisms by which the COS adsorbed/desorbed from the adsorbent were determined and an overall mechanism describing COS adsorption behavior was proposed.

Adsorption of Carbonyl Sulfide on Propylamine Tethered to Porous Silica.

Carbonyl sulfide (COS) reacts slowly with amines in the aqueous solutions used to absorb CO2 from natural gas and flue gas and can also deactivate certain aqueous amines. The effects of COS on amines tethered to porous silica, however, have not been investigated before. Hence, the adsorption of COS on aminopropyl groups tethered to porous silica was studied using in situ IR spectroscopy. COS chemisorbed mainly and reversibly as propylammonium propylthiocarbamate ion pairs [R-NH(C═O)S-+H3N-R] under dry conditions. In addition, a small amount of another chemisorbed species formed slowly and irreversibly. Nevertheless, the CO2 capacities of the adsorbents were fully retained after COS was desorbed.

Calcined ZnNiAl hydrotalcite-like compounds as bifunctional catalysts for carbonyl sulfide removal

The demand for a healthy environment and clean energy has been triggering the study on the preparation of excellent catalysts for the removal of sulfur-containing compounds. In this work, the removal of carbonyl sulfide (COS) from gas streams using Zn/Ni/Al hydrotalcite-derived oxide (HTO) was investigated. In particular, the structure, acid-base properties, and catalytic activity of catalysts prepared under different conditions were measured. A combination of experimental and theoretical methods, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), CO2 temperature programmed desorption (TPD), N2 adsorption–desorption techniques, and density functional theory calculations, were used to elucidate the removal of COS use Zn/Ni/Al HTO. Experimental results indicated that Zn/Ni/Al HTO had relatively high activity for the removal of COS. The density functional theory calculations revealed that “many defects” existed on the Ni3AlO4 (001) plane of crystal, which brought more active centers for the chemical adsorption and hydrolysis of COS. Elemental sulfur, metal sulfide, and sulfate were the final product of COS removal. The consumption of basic sites, as well as the blocking of pores, was considered as the main reason for catalyst deactivation.

Adsorptive removal of carbonyl sulfide by Fe-modified activated carbon: experiments and DFT calculations

Adsorptive removal of carbonyl sulfide (COS) by Fe-modified activated carbon was investigated in this study. A combination of experimental and theoretical method was used to elucidate the adsorption behavior and mechanism of COS. The sorbents were prepared by sol–gel method and the adsorptive performance for COS at 313, 323, 333 and 343 K was studied. Adsorption isotherms revealed that adsorption capacities increased with the increasing of temperature. Langmuir and Freundlich isotherm models were employed to analyze the equilibrium data. The Freundlich adsorption isotherm gave good fittings to the adsorption data. Also, free energy of adsorption, enthalpy, and entropy changes were determined to predict the nature of adsorption. The positive value (+ 68.394 kJ/mol) of the enthalpy change indicated that the adsorption is endothermic process and the adsorption process is a chemisorption. The mechanism of the chemisorption has been studied by using the density functional theory. The results showed that the adsorption of COS is dissociative adsorption. The cleavage of C–S bonds took place, and C–O bonds are adsorbed on the Fe top sites. Density of states analysis revealed that Fe–C–O interaction can be attributed to the bonding among Fe d orbitals, carbon s orbitals, and oxygen p orbitals. A novel type of metal oxide/active carbon was prepared by sol-gel method for the removal of carbonyl sulfide. Adsorption data for COS on the coal-based modified carbons were obtained at 313K, 323K, 333K and 343K. A combination of experimental and theoretical methods was used to elucidate the adsorption behavior and mechanism of COS

Adsorption of carbonyl sulfide on modified activated carbon under low-oxygen content conditions

Activated carbon sorbents impregnated with KOH, Fe(NO3)3, Cu(NO3)2, Zn(NO3)2 or Co(NO3)2 and their applications in catalytic oxidation reaction of COS were investigated. The results showed that the activated carbon modified with 10 % (mass percentage) KOH enhanced the adsorption ability significantly. And it was also found that the oxygen content and temperature were the two most important factors in the COS adsorption. Further investigation on the pore structures of the samples with X-ray photoelectron spectroscopy indicated that an adsorption/oxidation process happened in the KOH modified activated carbon in which the major existing forms of sulfur were SO42− and S species. The oxidation of COS suggested that KOH in the micropores may play a catalytic role during the adsorption. On the other hand, we found that the desorption activation energy from KOHW was higher than that from AC by the CO2-TPD spectra, which indicated the adsorption of CO2 on KOH impregnated activated carbon was stronger. The strong adsorption could be attributed to the basic groups on the activated carbon surface. In conclusion, the activated carbon impregnated with KOH promises a good candidate for COS adsorbent.

Low temperature hydrolysis of carbonyl sulfide using Zn–Al hydrotalcite-derived catalysts

A series of Zn–Al hydrotalcite-like compounds (HTLCs) were synthesized by co-precipitation method. The mixed oxides derived from HTLCs were tested for the catalytic hydrolysis of carbonyl sulfide (COS) at relatively low temperatures of 50°C. These catalysts were characterized by X-ray diffraction (XRD) and Thermogravimetry/Derivative Thermogravimetry Analysis (TG-DTA) and the results can help us to understand the effect of preparation conditions. The results showed that the Zn–Al hydrotalcite-like compounds were efficient precursor in preparing active and stable catalysts for hydrolysis of COS. The catalyst performance was strongly related to the synthesis pH and calcination temperature. The optimum condition was pH of 10, and calcination temperature of 400°C. Although water was indispensable for hydrolysis of COS, the excess water would hinder the adsorption of COS. In general, COS was hydrolyzed to H2S, which is depending on the chemistry of the derived oxides. The end-products of hydrolysis were simple substance S and sulfate. The presence of oxygen will accelerate the formation of the final product.

New sulfur adsorbents derived from layered double hydroxides: I: Synthesis and COS adsorption

Mixed oxides, prepared via the thermal decomposition of layered double hydroxides (LDHs), were screened gravimetrically for their ability to adsorb carbonyl sulfide (COS). Based on promising results obtained for Ni/Mg/Al, Ni/Mg/Fe and Co/Mg/Al mixed oxides, a study was undertaken to optimize the composition of these materials for COS adsorption. To investigate the effect of the M(II):M(III) ratio, LDHs of the type [MzMgyAlx(OH)2](CO3)x/2·0.5H2O (where M=Ni or Co, and x+y+z=1) were prepared at values of x corresponding to 0.33 and 0.20. Simultaneously, the elemental ratio of transition metal to magnesium (z/y) was varied. Mixed oxides obtained from the resulting LDHs were tested in fixed bed mode with a feed of 100ppm COS in N2 to determine breakthrough capacity. In general Ni/Mg/Al mixed oxides showed the best performance, a composition with Ni/Mg/Al=0.32/0.48/0.20 showing the best adsorption capacity. Treatment of the spent adsorbent under an atmosphere of 5% H2 in N2 at 450°C was found to provide an effective means of restoring the adsorption capacity over two cycles of adsorption and regeneration, although after three such cycles, adsorption capacity decreased.

Removal of Carbonyl Sulfide Using Activated Carbon Adsorption

Wastewater treatment plant odors are caused by compounds such as hydrogen sulfide (H2S), methyl mercaptans, and carbonyl sulfide (COS). One of the most efficient odor control processes is activated carbon adsorption; however, very few studies have been conducted on COS adsorption. COS is not only an odor causing compound but is also listed in the Clean Air Act as a hazardous air pollutant. Objectives of this study were to determine the following: (1) the adsorption capacity of 3 different carbons for COS removal; (2) the impact of relative humidity (RH) on COS adsorption; (3) the extent of competitive adsorption of COS in the presence of H2S; and (4) whether ammonia injection would increase COS adsorption capacity. Vapor phase react (VPR; reactivated), BPL (bituminous coal-based), and Centaur (physically modified to enhance H2S adsorption) carbons manufactured by Calgon Carbon Corp. were tested in three laboratory-scale columns, 6 in. in depth and 1 in. in diameter. Inlet COS concentrations varied from 35 to 49 ppmv (86–120 mg/m3). RHs of 17%, 30%, 50%, and 90% were tested. For competitive adsorption studies, H2S was tested at 60 ppmv, with COS at 30 ppmv. COS, RH, H2S, and ammonia concentrations were measured using an International Sensor Technology Model IQ-350 solid state sensor, Cole-Parmer humidity stick, Interscan Corp. 1000 series portable analyzer, and Drager Accuro ammonia sensor, respectively. It was found that the adsorption capacity of Centaur carbon for COS was higher than the other two carbons, regardless of RH. As humidity increased, the percentage of decrease in adsorption capacity of Centaur carbon, however, was greater than the other two carbons. The carbon adsorption capacity for COS decreased in proportion to the percentage of H2S in the gas stream. More adsorption sites appear to be available to H2S, a smaller molecule. Ammonia, which has been found to increase H2S adsorption capacity, did not increase the capacity for COS.

Adsorption of carbonyl sulfide on nickel and tungsten films

The interaction of carbonyl sulfide with evaporated nickel and tungsten films has been investigated in the temperature range 195-450 K using gas pressures ranging from 1 to 13 N m/sup -2/. Rapid but mainly associative chemisorption of COS occurred on both metals at 195 K. Further adsorption of COS on W at temperatures 293-450 K was extremely slow and accompanied by more CO desorption than COS adsorbed. Sulfidation of Ni film by COS occurred at temperatures greater than or equal to 293 K with the liberation of carbon monoxide. The rate of adsorption increased with temperature but was independent of COS pressure. The activation energy (E/sub x/) increased with extent (X) of sulfidation to a limiting value of 97 kJ mol/sup -1/. A linear relationship was obtained from the plot of E/sub x/ against 1/X, suggesting the applicability of Cabrera-Mott theory to the sulfidation of Ni film by COS. 20 references, 2 figures, 1 table.