Hydrolysis Of COS Research Articles

Catalytic hydrolysis of COS over unsupported Al2O3: New insights into the influence of hydroxyl characteristics on hydrolysis efficiency

H2O molecules are challenging to dissociate at low temperatures to produce hydroxyl groups for heterogeneous carbonyl sulfide (COS) hydrolysis. Utilizing the inherent hydroxyl groups on Al2O3 surfaces for catalytic COS hydrolysis is effective; however, the relationship between the hydroxyl nature and hydrolysis efficiency remains unclear. In this study, we investigated the effects of crystal structure, surface morphology, specific surface area, and hydroxyl characteristics of Al2O3 on COS hydrolysis efficiency. Results showed that the content, stability, and activity of hydroxyl groups significantly impacted the efficiency. Catalysts prepared from commercial alumina (Al2O3-C) exhibited superior COS hydrolysis efficiencies under both dry and humid conditions compared to pseudo-boehmite derived Al2O3 (Al2O3-S) and boehmite derived Al2O3 (Al2O3-B) owing to the higher, more stable, and active hydroxyl content in Al2O3-C. Although Al2O3-S contained a sufficient amount of surface hydroxyl, its lower activity reduced the hydrolysis efficiency. The catalytic COS hydrolysis mechanism over hydroxyl-rich Al2O3 was elucidated through various characterization methods, providing new insights into the correlation between Al2O3 surface hydroxyl properties and COS hydrolysis efficiency.

Construction of La/Al2O3 nanorod-like catalyst with rich basic sites: Enabling efficient conversion of COS-superior selectivity and theoretical insights

The introduction of surface basic sites to COS hydrolysis catalysts can improve H2O activation and COS adsorption, leading to enhanced catalytic performance. However, maximizing the concentration of basic sites remains a challenge due to the limited exposed surface area of these catalysts. Herein, a La/Al2O3 catalyst with abundant alkaline sites to catalyze the hydrolysis of COS was prepared by a simple ammonia-assisted hydrothermal method. This synthesized La/Al2O3 catalyst exhibits a thin rod-like structure formed by the random accumulation of nanoparticles. Lanthanum, one of the most abundant rare earth metals, is an ideal doping aid to further promote the COS-catalyzed hydrolysis performance of Al2O3. Characterization studies show that the proper lanthanum loading effectively enhances the formation of basic sites, leading to improved lattice oxygen reactivity and –OH adsorption capacity. As a result, the prepared La-loaded Al2O3 nanorod sample with abundant basic sites exhibits nearly 100 % COS conversion and total H2S yield at 160 °C. In addition, the reaction pathways and deactivation mechanisms for selective catalytic hydrolysis of COS on the La-doped Al2O3 catalyst were revealed by using in situ DRIFTS to evaluate COS adsorption and hydrolysis. Density functional theory calculations showed that La loading enhances the electron transfer between the La and Al atoms, improves the formation of basic sites, and enhances the adsorption of –OH. This study provides new insights into the design of efficient alumina-based catalysts for the catalytic hydrolysis of COS.

Deep removal of COS by carbon aerogel in natural gas: A 3D network structure of nitrogen doped and Cu based adsorbent

For the purpose of overcoming the difficulty of low removal rate of COS at low temperatures, N-doped copper oxide-supported carbon aerogels were prepared with sodium alginate as a carbon source for deep removal of COS (about 20 ppm) from natural gas. By exploring the effects of different nitrogen sources (urea, melamine and p-phenylenediamine), carbon–nitrogen ratio and carbonization temperature, p-phenylenediamine-doped copper oxide-loaded carbon aerogels (PPD-Cu/CA) with both excellent catalytic hydrolysis of COS and adsorption were prepared. The COS adsorption capacity of optimized PPD-Cu/CA was 18.6 mg·g−1 with 0.94 %Vol of water content at 40 °C, meanwhile, the COS removal efficiency at 40,000 and 70,000 mL·g−1·h−1 could reach 100 % and 94.6 %, respectively, showing excellent high space velocity resistance. Combined with characterization and experimental results, the introduction of p-phenylenediamine enriched the pore structure of the carbon carrier, increased the neutral base site, and played a positive role in the adsorption and hydrolysis of COS. This study provides a new insight into the removal of carbonyl sulfur from natural gas.

Unraveling the sulfur poisoning mechanism of N-doping KAl2O3 catalyst in simultaneous hydrolysis of COS and CS2 via experimental and theoretical study

The short lifetime and poor resistance to poisoning of hydrolysis catalysts restricted their application in the desulfurization of blast furnace gas. N doping was applied to enhance the low-temperature hydrolytic activity and stability of the catalysts, and the poisoning mechanisms of COS and CS2 were explored by a series of characterizations and DFT theoretical calculations. The results revealed that the N-modified catalyst could maintain 100 % COS conversion and more than 40 % CS2 conversion after 120 h reaction. The characterization results certified that reduced surface area, weakened surface basicity, and weakened COS and CS2 adsorption capacity were the main causes of catalyst poisoning. The deposited sulfur species on the catalyst were mainly monomeric sulfur and sulfate (Al2(SO4)3). The incorporation of N significantly reduced the production of Al2(SO4)3 and enhanced the protection of the Al active site by K, which in turn enhanced the resistance to poisoning. DFT theoretical calculations exhibited that the oxidation products of COS were mainly COSO2- and CO2SO-, while CS2 was easily converted to COS first and then further be oxidized. The addition of N made the oxidation intermediate species more difficult to generate, while the oxidation product SO2 was easier to desorb, which explained the improved catalyst resistance to poisoning.

Preparation of NiGa2O4 nanoflower for boosting catalytic hydrolysis of carbonyl sulfide

A nanoflower-like NiGa2O4 spinel was designed for the catalytic hydrolysis of COS. The COS hydrolysis activity of the NiGa2O4 nanoflower was significantly improved as compared to the Fe5Ga3O12 and CoGa2O4, which was ascribed to the enhanced diffusion and surface alkalinity. In the reaction, COS adsorption was significantly strengthened on the basic sites, and thereby the formation of intermediates such as HCO3– and HSCO2- was facilitated. The NiGa2O4 catalyst also demonstrated excellent sulfur tolerance and stability in long-term testing for COS hydrolysis using simulated industrial gas at 100 °C, maintaining ∼100% of H2S selectivity in the first 70 h.

Alkali-induced metal-based coconut shell biochar for efficient catalytic removal of H2S at a medium–high temperature in blast furnace gas with significantly enhanced S selectivity

The low S selectivity of catalysts for H2S removal significantly hinders its application in blast furnace gas desulfurization. In this study, Cu-based coconut shell biochar was modified with different types and contents of alkali species. The results showed that the S selectivity close to 100% was prolonged from 0 to 750 min. At the same time, the sulfur capacity was increased from 242.1 mg/g (before the modification) to 373.4 mg/g by using K2CO3-induced Cu-based biochar at 120 °C. In CO, H2O, and O2 atmosphere, H2S was dissociated and oxidized to elemental S. Additionally, K2CO3 exhibited an elemental S anchoring effect, making the S more stable at medium–high temperatures and weakening the reactivity of S with CO and ·O2–. Thus, less COS and SO2 were generated. Moreover, the basic sites enhanced by K2CO3 promoted the hydrolysis of COS to generate H2S, which entered the desulfurization cycle. K2CO3 also showed a synergistic effect with the active components, generating more ·O2– to promote the oxygenation of H2S. The regeneration efficiency of the catalyst could be stabilized above 90%. These findings could provide guidance and reference for designing and applying desulfurization catalysts with high S selectivity and activity.

Synergistic effect of Fe2O3 and CuO on simultaneous catalytic hydrolysis of COS and CS2: Experimental and theoretical studies

In this work, experimental and theoretical methods were used to investigate the synergistic effect of Fe2O3 and CuO on simultaneous catalytic hydrolysis of COS and CS2. Experimental results indicated that Fe2O3 mainly focused on the removal of CS2, and CuO mainly focused on the removal of COS. Meanwhile, Fe2O3 and CuO had the synergistic effect on simultaneous removal of COS and CS2. Theoretical results indicated that the adsorption priority order over Fe2O3(0 0 1)/CuO(1 1 0) was H2O > CS2 > COS. Furthermore, H2O was easy to migrate onto the surface of CuO(1 1 0), and CS2 was easy to migrate onto the surface of Fe2O3(1 1 0). Meanwhile, COS was preferentially adsorbed on Fe2O3(0 0 1). Fe2O3(0 0 1) and CuO(1 1 0) surfaces were beneficial for the adsorption of –OH groups. Fe2O3(0 0 1) enhanced the first step hydrolysis of CS2. CuO(1 1 0) enhanced the COS hydrolysis. The synergistic effect of Fe2O3 and CuO was attributed to the different hydrolysis priority of COS and CS2. Firstly, CS2 was adsorbed on Fe2O3 surface and the first step hydrolysis of CS2 occurred. Then, the hydrolysis product COS migrated from Fe2O3 to CuO and the COS hydrolysis occurred. The theoretical results were consistent with the experimental results.

Efficient catalytic elimination of COS and H2S by developing ordered mesoporous carbons with versatile base N sites via a calcination induced self-assembly route

Catalytic elimination of highly toxic COS and H2S from industrial resources plays a crucial role in terms of production safety and environmental protection. We report here novel calcination induced self-assembly concept to the fast synthesis of ordered mesoporous carbons with structural base N sites (A-N-OMC-Ts, where T stands for carbonization temperature) without using any solvent and catalysts. The A-N-OMC-Ts show large BET surface areas (∼1538 m2/g), ordered mesoporosity, and the base N sites exhibit versatile structures (e.g. pyridine and pyrrole, 2.03–3.77 wt%). As a result, A-N-OMC-Ts show excellent activities in hydrolysis of COS to H2S, and the H2S can be efficiently captured (∼10.5 mmol/g, 0 °C, 1 bar, IAST selectivity H2S/N2 = 4963, 75 °C) and oxidized into elemental sulfur by A-N-OMC-Ts. The complete elimination of COS and H2S over A-N-OMC-Ts was performed at ambient conditions (50 °C for COS; 150 °C for H2S, and Ea = 32.29 kJ/mol), much better than that of g-C3N4 (150 °C, H2S conversion < 10%, Ea = 42.11 kJ/mol). These performances are outstanding among the metal-free catalysts reported previously. A plausible mechanistic scenario involves the synergistic effect of pyridinic and pyrrolic N as well as the intermediate H2O2 was proposed by us. Coupled the cleavage of H-S bond and S release that accelerate the desulfuration rate.

Hydrolysis of COS over MgAl Mixed Oxides Derived from Hydrotalcites

A series of MgAl hydrotalcite-derived composite oxides were prepared by co-precipitation methods. The effects of calcination temperature, reaction temperature, water vapor volume fraction, and alkali metal addition on the hydrolysis activity of the samples were investigated. The crystal structure, specific surface area, pore structure, and basic position distribution of the composite oxides were characterized using XRD, BET, TPD, and XPS. The results shown that the catalytic activity firstly increased and then decreased with the rise of calcination temperature. Furthermore, the sample that calcined at 650℃ can achieve the best catalytic activity (complete removal of COS lasted for 180 min). Increasing the reaction temperature improved the catalytic activity, which can present excellent catalytic activity and stability at temperatures above 70℃. In addition, the doping of the alkali metal Cs improved the catalytic activity, the complete removal time for COS can be maintained for 480 min.

Metalated carbon nitrides as base catalysts for efficient catalytic hydrolysis of carbonyl sulfide

A new type of base catalyst was designed and prepared by metalation of carbon nitrides with alkali metal ions. The as-prepared metalated carbon nitride composites showed enhanced basicity and efficient catalytic hydrolysis of carbonyl sulfide. The results of this study demonstrate that the metalation of carbon nitrides holds great promise for base catalysis applications.

Deactivation mechanism of the simultaneous removal of carbonyl sulphide and carbon disulphide over Fe–Cu–Ni/MCSAC catalysts

The deactivation mechanism of the simultaneous removal of COS and $$\hbox {CS}_{2}$$ over a Fe–Cu–Ni/MCSAC catalyst was investigated using SEM/EDS, XPS and in situ DRIFTS methods. The results show that the catalytic hydrolysis of COS and $$\hbox {CS}_{2}$$ over the Fe–Cu–Ni/MCSAC catalyst involves two steps: hydrolysis of $$\hbox {COS}/\hbox {CS}_{2}$$ and oxidation of $$\hbox {H}_{2}\hbox {S}$$ . The SEM/EDS and XPS results indicate that that catalytic hydrolysis of $$\hbox {CS}_{2}$$ can be achieved by the actions of alkaline groups and active components. When $$\hbox {O}_{2}$$ was introduced into the system, oxidation of $$\hbox {H}_{2}\hbox {S}$$ occurred $$\textit{via}\hbox {H}_{2}\hbox {S}\rightarrow \hbox {S}\rightarrow \hbox {SO}_{4}^{2-}/\hbox {sulphate}$$ . In situ DRIFTS experiments indicated that the formation of sulphate may occur as follows: (a) $$\hbox {H}_{2}\hbox {S}+\hbox {O}_{2}\rightarrow \hbox {S}+\hbox {H}_{2}\hbox {O}$$ , (b) S+ $$\hbox {O}_{2}\rightarrow \hbox {S}$$ –O, (c) –COO+ $$\hbox {H}_{2}\hbox {S}\rightarrow $$ –CH+S–O, (d) C–OH+ $$\hbox {H}_{2}\hbox {S}\rightarrow $$ –CH+S–O. The in situ DRIFTS experiments also indicated that the C–OH groups, –COO groups and $$\hbox {O}_{2}$$ played important roles in the deactivation of the catalyst, which was consistent with the XPS results. Meanwhile, the $$\hbox {SO}_{4}^{2-}/\hbox {sulphate}$$ content increased during the reaction, which led to its occupancy of the catalyst’s surface activity sites. Additionally, the alkaline groups and active components were removed, which could also result in the deactivation of the catalysts. SYNOPSIS The deactivation mechanism of the simultaneous removal of COS and $$\hbox {CS}_{2}$$ over a Fe–Cu–Ni/MCSAC catalyst was investigated using SEM/EDS, XPS and in situ DRIFTS methods. In situ DRIFTS experiments indicated that the formation of sulphate may occur as follows: (a) $$\hbox {H}_{2}\hbox {S}+\hbox {O}_{2}\rightarrow \hbox {S}+\hbox {H}_{2}\hbox {O}$$ , (b) S+ $$\hbox {O}_{2}\rightarrow \hbox {S}$$ –O, (c) –COO+ $$\hbox {H}_{2}\hbox {S}\rightarrow $$ –CH+S–O, (d) C–OH+ $$\hbox {H}_{2}\hbox {S}\rightarrow $$ –CH+S–O.

Regeneration performance and mechanism of modified walnut shell biochar catalyst for low temperature catalytic hydrolysis of organic sulfur

In this study, four different regeneration methods (WR, NR, AR and WNAR), regeneration conditions and regeneration mechanism of a Fe-Cu-KOH supported on WSB as a precursor catalyst (Fe-Cu-KOH/WSB) for low temperature hydrolysis of CS2 and COS were investigated. The results showed that the WNAR method (Water washing+Nitrogen sweeping+Alkali steeping regeneration) had the best regeneration performance. Under optimal regeneration conditions (500°C nitrogen sweeping temperature and 13% KOH steeping content), the regenerated Fe-Cu-KOH/WSB catalyst could achieve to 42.64mgS/g sulfur capacity, and it was close to fresh catalyst (48.58mgS/g). A small amount of sulfate and a large number of OH groups were washed away in water washing process. XPS, TG/DTA and DRIFTS results indicated that a large number of Fe2(SO4)3 were decomposed into Fe2O3 in nitrogen sweeping process, which could recover a large number of surface area and active component. CO2-TPD results indicated that the supplement of OH groups in KOH steeping process recovered the alkalinity site strength, which was conducive to desulfurization. After three times regeneration, the sulfur capacity of Fe-Cu-KOH/WSB could reach 33.94mgS/g, and it indicated that the WNAR method had good stability for the recovery of catalytic activity. From BET, CO2-TPD XPS and TG/DTA results, it could be seen that the decrease of adsorptive and catalytic ability was attributed to the oxidation of WSB, the block effect of KOH and decrease of CuO contents. This study provided a suitable regeneration method for industrial application of Fe-Cu-KOH/WSB on catalytic hydrolysis of organic sulfur.

Catalytic hydrolysis of COS over CeO2 (110) surface: A density functional theory study

Density functional theory (DFT) calculations were performed to investigate the reaction pathways for catalytic hydrolysis of COS over CeO2 (110) surface using Dmol3 model. The thermodynamic stability analysis for the suggested routes of COS hydrolysis to CO2 and H2S was evaluated. The absolute values of adsorption energy of H2O-CeO2 are higher than that of COS-CeO2. Meanwhile, the adsorption energy and geometries show that H2O is easier adsorbed on the surface of CeO2 (110) than COS. H2O plays a role as a bridge in the process of joint adsorption. H2O forms more CeOH groups on the CeO2 (110) surface. CeO2 decreases the maximum energy barrier by 76.15kcal/mol. The migration of H from H2O to COS is the key for the hydrolysis reaction. CO channel is easier to occur than CS channel. Experimental result shows that adding of CeO2 can increase COS removal rate and prolong the 100% COS removal rate from 180min to 210min. The difference between Fe2O3 and CeO2 for the hydrolysis of COS is characterized in the atomic charge transfer and the formation of HO bond and HS bond. The transfer effect of H in H2O to S in COS over CeO2 decreases the energy barriers of hydrolysis reaction, and enhances the reaction activity of COS hydrolysis.

Simultaneous removal of COS and H2S from hot syngas by rare earth metal-doped SnO2 sorbents

The pure SnO2 and rare earth metal (Y and La)-doped SnO2 were synthesized using a co-precipitation method for the simultaneous removal of COS and H2S from hot syngas at 350°C. The pure SnO2 sorbent exhibited a poor catalytic hydrolysis effect for COS conversion at moderate temperatures of 300–400°C due to the formation of SnS during the desulfurization. SnS caused a decrease in the COS conversion because the activity of SnS was considerably lower than that of reduced SnO2 for the hydrolysis of COS. The addition of Y and La resulted in the formation of numerous smaller pores and increased the total pore volume of the sorbents. The good dispersion of rare earth metal resulted in the improvement of COS conversion, which produced a higher breakthrough sulfur capacity. As the La content increased, the COS conversion reached nearly 100% and was no longer the restrictive procedure for the simultaneous removal of COS and H2S. The total breakthrough sulfur capacity was 148.4mg/g when 40M percent of La was doped into the SnO2 sorbent.

Catalytic hydrolysis of COS over calcined CoNiAl hydrotalcite-like compounds modified by cerium

The catalytic performance of COS hydrolysis over calcined CoNiAl hydrotalcite-like compounds (HTLCs) modified by cerium was investigated. All catalysts were prepared by thermal decomposition of hydrotalcite-like precursors synthesized by co-precipitation method and characterized by various technologies. Among all catalysts studied, catalyst CoNiAl-50 exhibited excellent COS conversion. The changes of structural properties, oxidative properties of catalysts and increase of surface defect sites mainly accounted for the enhancements of the catalytic activities with addition of cerium. Element sulfur and the sulfate species accumulated on the surface which might contribute to catalyst poisoning and Ce could affect the formation and content of element sulfur and sulfate.

Characterization of Zn–Ni–Fe hydrotalcite-derived oxides and their application in the hydrolysis of carbonyl sulfide

A series of Zn, Ni and Fe containing hydrotalcite-like compounds with various M 2+/M 3+ ratios were synthesized by co-precipitation method at pH = 10. The products were characterized by XRD, SEM, TG-DTA, FTIR, CO 2-TPD and N 2 adsorption/desorption techniques. The results showed that M 2+/M 3+ ratio affected the formation of hydrotalcite crystal seriously. The precursors with M 2+/M 3+ mole ratio of 2 and 3 showed pure hydrotalcite phase. After calcination at 250 °C, the derived oxides with larger surface area and more basic sites were obtained. Desulfurization tests showed that the Zn–Ni–Fe hydrotalcite-derived oxide exhibited an excellent activity in low temperature hydrolysis of COS. The optimum M 2+/M 3+ mole ratio was 3.

Methyl mercaptan and carbonyl sulfide traces removal through adsorption and catalysis on zeolites and layered double hydroxides

In this paper, the adsorption of methyl mercaptan and carbonyl sulfide by metal exchanged zeolites and layered double hydroxides (LDH) is studied. The affinity of CH 3SH for metal-exchanged zeolites was found to increase with the basicity and the valence of the cation. Yoon–Nelson modelling gave good predictions of half time of breakthrough for each zeolite tested. Thermogravimetry was used in the case of the system CH 3SH/NaX for elucidating the desorption process of CH 3SH from NaX. In contrast, the affinity of COS was found clearly lower for Me-zeolite in comparison with CH 3SH. Catalytic hydrolysis of COS was tested with the same metal exchanged zeolites and LDH materials and the basicity of the catalysts was found to strongly influence the hydrolysis.

Ambient Temperature Hydrolysis of Carbonyl Sulfide Using γ-Alumina Catalysts: Effect of Calcination Temperature and Alkali Doping

The hydrolysis of COS using γ-alumina as catalyst at 20 °C is described and discussed. In particular, the effect of calcination on the catalyst activity is investigated. Catalysts calcined at 100 and 500 °C are found to give the highest catalyst activities, in terms of both specific (mol COS converted/g catalyst/h) and intrinsic (mol COS converted/m2 catalyst/h) activity. Calcination at other temperatures leads to diminished catalyst activity. The effects are discussed in terms of the known surface chemistry of γ-alumina involving physisorbed water, surface dehydroxylation and defect formation. The addition of alkali additives (Li+, Na+, K+, Cs+, Mg2+, Ca2+, Ba2+, Si2+) is also reported. Only K+ and Cs+ give a sustained enhancement in catalyst activity, whereas all the other additives act as catalyst poisons for the steady-state performance measured following 5 h time-on-stream. Interestingly, addition of Na+ and Mg2+ leads to a very high initial activity (>95% COS conversion) but the effect is very short-lived and, after 5 h time-on-stream, a much lower steady-state activity (∼15-30% COS conversion) is observed.

Desulfurization of syngas in a transport reactor

AbstractDuring gasification, sulfur present in carbonaceous materials is converted into reduced sulfur species, such as H2S and COS. These sulfur species are conventionally removed from syngas by catalytic hydrolysis of COS into H2S, followed by scrubbing of H2S with liquid‐phase amine systems. Amine‐based processes are subject to equipment corrosion, foaming, amine‐solution degradation, and evaporation, and require extensive wastewater treatment. As a result, this sulfur removal technology is complex, capitalintensive, and expensive. Furthermore, this conventional technology requires the syngas be cooled to nearly ambient temperatures, thus wasting valuable energy.New emerging technologies for sulfur removal from syngas use regenerable sorbents, primarily based on ZnO. Recent advances in sorbent technology allow sulfur species to be removed from syngas over a wide temperature range (260° to 760° C), making it an attractive alternative for a wide variety of applications, including power generation, chemical production, and fuel cells. This sorbent technology has advanced to the point that syngas desulfurization can be carried out in both fixed‐and fluidized‐bed reactors, depending upon process design needs. Additional applications of this technology in desulfurization of natural gas and removal of sulfur species from a syngas generated from gasification of black liquor were investigated.

Ni- and Zn-promotion of γ-Al 2O 3 for the hydrolysis of COS under mild conditions

The hydrolysis of COS using γ-Al 2O 3 as catalyst at 30°C is described. The effect of additives (ca. 3% Na, Fe, Co, Ni, Cu, Zn) is described in detail. The additives reduce the surface area of the γ-Al 2O 3 markedly but have no effect on the powder X-ray diffraction pattern. All significantly enhance the initial intrinsic activity (mol COS hydrolysed/m 2/h) when compared with unpromoted γ-Al 2O 3. However, this initial performance rapidly decays for the Na-, Fe-, Co- and Cu-modified catalysts. During this initial reaction period, of up to 5 h, the catalyst retains sulphur. In terms of specific activity (mol COS hydrolysed/g/h) only Ni- and Zn-promoted catalysts give a significant increase that is stable throughout the time-scale of these experiments.