COS Hydrolysis Research Articles

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.

Influence of Surface Basic Sites and Oxygen Vacancies on the Performance of Metal-Modified Rod-Like Ceria Catalysts for Low-Temperature Hydrolysis of Carbonyl Sulfide.

This study utilized a hydrothermal method to synthesize various metal-modified rod-like ceria catalysts (Fe, Co, Cu, Ni, La), achieving efficient COS removal at low temperatures. The research identified surface oxygen vacancies and basic sites as critical factors that influence the catalytic performance of COS hydrolysis. The addition of different metals to pristine ceria rods increased the specific surface area, oxygen vacancy content (Ov), and basicity, which enhanced the catalysts' sulfur resistance and stability. Among all the catalysts tested, 10La-CeO2 demonstrated the highest COS removal rate. This is because La doping significantly augmented Ov, providing more H2O adsorption and activation sites. Furthermore, 10La-CeO2 showed enhanced Lewis basicity, making it easier for COS to adsorb and promote hydrolysis. The in situ DRIFTS results confirmed that appropriate oxygen vacancies and basic sites favored the formation of intermediates such as HCO3 - and HSCO2 -, promoting the decomposition of COS into H2S and CO2.

Nanorod Al2O3 catalysts for simultaneous hydrolytic removal of COS and CS2 via crystal surface modulation: Experimental and theoretical studies

The undesirable stability and vulnerability to poisoning of catalysts have posed a great obstacle to the development of organosulfur hydrolysis technology. In this paper, H-K0.1Al2O3 nanorod catalysts with exposed Al2O3(111) crystal plane were prepared by hydrothermal synthesis. The results indicated that the COS and CS2 hydrolysis activity at low temperatures of the H-K0.1Al2O3 catalyst was significantly higher than that of K0.1Al2O3. In the presence of 0.01 vol% HCl, there was no decrease in the COS conversion of H-K0.1Al2O3 after 12 h of reaction. The CS2 conversion was stable at about 65 %. Characterization results revealed that the improved hydrolysis performance was mainly related to enhanced surface alkalinity and more oxygen vacancies, which strengthened the adsorption capacity of the reactive molecules. The results of DFT calculations proved the stronger adsorption ability of the Al2O3(111) plane than the Al2O3(110) plane. The suppressed HCl adsorption contributed to the enhanced resistance to chlorine poisoning. Reaction path calculations demonstrated that the H2O molecules on the Al2O3 (111) dissociated more rapidly to produce –OH, and the intermediates -CS2OH and -HSCO were more easily generated with lower reaction energy barriers.

Revelation of HCl poisoning and enhancement mechanism on N-modified Al2O3 catalysts for COS and CS2 hydrolysis

The presence of HCl in blast furnace gas significantly inhibits hydrolytic activity and catalyst stability. The anti-chlorine capacity and poisoning mechanism of Al2O3 catalysts before and after nitrogen modification was investigated by activity evaluation, characterization analysis and theoretical calculations. In the presence of 0.01 vol% HCl, the COS and CS2 conversions of K0.1Al2O3 catalysts decreased rapidly after 4 h of reaction, which was amended by N doping. The N0.1K0.1Al2O3 catalyst maintained 48.23 % COS conversion and 45.41 % CS2 conversion, respectively, after 16 h reaction. The deteriorated reactivity was mainly associated with the decreased specific surface area, reduced chemisorbed oxygen, disrupted basicity and COS and CS2 adsorption ability. Sulfate and HCl on the surface of the unmodified catalyst mainly destroyed the Al sites and led to catalyst deactivation. N doping reinforced the tendency of toxic molecules to adsorb at the K site (K2SO4 and KCl) and thus protected the Al active site. DFT calculation results demonstrated the inhibition of HCl adsorption at the Al site by N modification, while the trapping of HCl by both K and N sites efficiently protected the Al site from acidification. The reaction pathway calculations certified that N doping increased the energy barrier of the HCl dissociation reaction, which inhibited the acidification and deactivation of Al2O3 to some extent.

COS and H2S simultaneous removal from blast furnace gas over a tailored Cu/Zr co-doped K@TiO2 bifunctional catalyst under low temperature

The lengthy processes and cumbersome operations for the separate removal of COS and H2S have severely limited the development of blast furnace gas recycling process. CuO exhibits excellent H2S oxidation performance, but weak COS hydrolysis performance; in contrast, ZrO2 shows the opposite trend. However, the functional combination of CuO and ZrO2 has never been used for simultaneous removal of COS and H2S. In this study, a Cu/Zr co-doped K@TiO2 bifunctional catalyst was tailored to simultaneously remove COS and H2S. The combined COS and H2S capacity of this catalyst reaches 340.5 mg/g at a low temperature of 60 °C, which is much higher than those of other reported bifunctional catalysts. The microcrystal structure formed by Cu/Zr co-doping increases the specific surface area of the catalyst and promotes the adsorption of COS/H2S. Specifically, Zr doping increases the content of moderate basic sites and significantly improves the hydrolysis efficiency of COS. Moreover, Cu doping induces lattice distortion of TiO2, while CuO captures 4 s valence electrons of K to form Cu2O. These two processes lead to the release of lattice oxygen from TiO2 and CuO, generating oxygen vacancies and ·O2−, which promotes H2S oxidation. By proposing a simple route for the bifunctionalization of a desulfurization catalyst, this study drives innovation in both the theory and application of simultaneous removal of COS and H2S.

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.

Oxygen vacancy-engineered titanium-based perovskite for boosting H2O activation and lower-temperature hydrolysis of organic sulfur

Modulation of water activation is crucial to water-involved chemical reactions in heterogeneous catalysis. Organic sulfur (COS and CS2) hydrolysis is such a typical reaction involving water (H2O) molecule as a reactant. However, limited by the strong O-H bond in H2O, satisfactory CS2 hydrolysis performance is attained at high temperature above 310°C, which is at the sacrifice of the Claus conversion, strongly hindering sulfur recovery efficiency improvement and pollution emissions control of the Claus process. Herein, we report a facile oxygen vacancy (VO) engineering on titanium-based perovskite to motivate H2O activation for enhanced COS and CS2 hydrolysis at lower temperature. Increased amount of VO contributed to improved degree of H2O dissociation to generate more active -OH, due to lower energy barrier for H2O dissociation over surface rich in VO, particularly VO clusters. Besides, low-coordinated Ti ions adjacent to VO were active sites for H2O activation. Consequently, complete conversion of COS and CS2 was achieved over SrTiO3 after H2 reduction treatment at 225°C, a favorable temperature for the Claus conversion, at which both satisfying COS and CS2 hydrolysis performance and improved sulfur recovery efficiency can be obtained simultaneously. Additionally, the origin of enhanced hydrolysis activity from boosted H2O activation by VO was revealed via in-depth mechanism study. This provides more explicit direction for further design of efficacious catalysts for H2O-involved reactions.

A study on the catalytic performance of the ZrO2@γ-Al2O3 hollow sphere catalyst for COS hydrolysis

A nanoscale hollow sphere hydrolysis catalyst with low catalytic energy consumption, long catalytic lifetime and high conversion COS efficiency.

Enhanced performance and DFT study of sulfur poisoning mechanism of modified Al2O3 catalyst in COS hydrolysis

The sulfur poisoning mechanism of Al2O3 catalysts in COS hydrolysis is still controversial. The modified K0.1Al2O3-PA catalyst exhibited enhanced anti-poisoning performance, which maintained 100 % conversion and 85 % H2S selectivity after 150 h of reaction. The results illustrated that the decrease of activity was related to the reduced specific surface area, basicity, oxygen vacancies and weakened adsorption ability of COS. The sulfur species on the Al2O3 and Al2O3-PA catalyst was Al2(SO4)3 and elemental S, respectively. After adding K, the sulfur species existed stably in the form of K2SO4. The DFT calculation results suggest that the trapping of H2S by K weakens the adsorption of H2S on Al, which protects the Al sites. The results suggested that COS and H2S are difficult to be oxidized by lattice oxygen, especially after adding K. In the presence of O2, H2S is more easily oxidized to generate S and OH– through a two-step dehydrogenation reaction.

Experimental and theoretical research on pore-modified and K-doped Al2O3 catalysts for COS hydrolysis: The role of oxygen vacancies and basicity

The high activation temperature and poor stability of COS hydrolysis catalysts greatly hinder its application in the field of blast furnace gas desulfurization. Various organic additives were applied to modulate the pore structure of the catalyst. Combined with the loading of K, the catalytic performance, H2S selectivity and enhanced mechanism of the modified catalysts were deeply explored. The preferred catalyst exhibited an improved low-temperature activity of 97.2 % and H2S selectivity of 91 % at 75 ℃. The COS conversion of the preferred catalyst remained above 95 % after 50 h reaction. The characterization results revealed that the addition of pore modifiers and basic components resulted in a wider pore size distribution and increased specific surface area. More oxygen vacancies and enhanced surface alkalinity were also certified to contribute to the catalysis properties. In-situ DRIFTS results exhibited that the COS adsorption ability was significantly strengthened due to enhanced alkalinity, while more intermediate active species such as HCO3– and HSCO2- were produced. DFT calculation results indicates that the modified catalyst displays larger adsorption energy of reaction gas molecules·H2O molecular promotes the adsorption of COS and H2S, while H2S inhibits the adsorption of COS. The presence of oxygen vacancies promoted the adsorption of COS and weakened the competitive adsorption of COS and H2S. The adsorbed COS reacts with OH– or H species to form the key intermediate HSCO2-, which is further hydrogenated and decomposed into H2S and CO2. The lower energy barrier and shorter reaction steps for the formation of HSCO2- species are the key incentives for the improved activity of the K-modified catalyst.

Boosting COS catalytic hydrolysis performance over Zn-Al oxide derived from ZnAl hydrotalcite-like compound modified via the dopant of rare earth metals and the replacement of precipitation base

In this work, a series of Zn-Al oxides calcined from ZnAl hydrotalcite-like catalysts were prepared using the co-precipitation method and then applied to remove COS. The effects of the content of Sm and the species of rare earth metal on the catalytic activities of COS hydrolysis are investigated. Experimental results show that the prepared catalyst doped with 20 wt% Sm performs better catalytically. Based on the optimization of Sm dopant, the effect of the precipitation base in the ZnAl hydrotalcite-like compounds on the catalytic activities of the catalysts is further investigated. The results show that the prepared catalyst using KOH and K2CO3 as the precipitation base exhibits the best catalytic performance. The characterization results show that the doping of rare earth metals can weaken the crystallinity and the introduction of an appropriate amount of Sm ions can significantly enhance the proportion of adsorbed oxygen species. Moreover, the results show that the synergistic effect of the doping of Sm and the replacement of precipitating alkali contribute to the enhancement of the number of basic sites, especially weak and medium basic sites. Furthermore, combined with in-situ DRIFTS, the catalytic mechanism of COS hydrolysis on ZnAl-20Sm-Na MMO is proposed.

Deactivation Mechanism of COS Hydrolysis over Potassium Modified Alumina

Deactivation Mechanism of COS Hydrolysis over Potassium Modified Alumina

Oxygen vacancy defects engineering on Cu-doped Co3O4 for promoting effective COS hydrolysis

The activation of H2O is a key step of the COS hydrolysis, which may be tuned by oxygen vacancy defects in the catalysts. Herein, we have introduced Cu into Co3O4 to regulate the oxygen vacancy defect content of the catalysts. In situ DRIFTS and XPS spectra reveal that COS and H2O are adsorbed and activated by oxygen vacancy. The 10 at% Cu doped Co3O4 sample (10CuCo3O4) exhibits the optimal activity, 100% of COS conversion at 70 °C. The improved oxygen vacancies of CuCo3O4 accelerate the activation of H2O to form active OH. COS binds with hydroxyl to form the intermediate HSCO2−, and then the activated –OH on the oxygen vacancy reacts with HSCO2− to form HCO3−. Meanwhile, the catalyst exhibits high catalytic stability because copper species (Cu+/Cu2+) redox cycle mitigate the sulfation of Co3O4 (Co2+/Co3+). Our work offers a promising approach for the rational design of cobalt-related catalysts in the highly efficient hydrolysis COS process.

Inhibition of CO in Blast Furnace Flue Gas on Poisoning and Deactivation of a Ni/Activated Carbon Catalyst in COS Hydrolysis

A new method for delaying or avoiding catalyst poisoning in COS catalytic hydrolysis was found by using one of the existing gas components in blast furnace flue gas: CO. In this work, wood-based ac...

Transient H2S content rise in the effluent of a natural gas treating unit: Role of COS hydrolysis and heat stable amine salts

In response to expanding requests towards natural gas usage as a key energy source and vital feedstock, revamping current gas refineries to provide additional capacity and meet the sustainability limitations is considered a crucial essence. In this work, the behavior of a gas refinery after switching its amine solution from diethanolamine to methyldiethanolamine was evaluated. The plant's main goals by this change, i.e., increase sweetening capacity and lowering energy consumption intensity was fulfilled. However, after some overhaul services, the hydrogen sulfide content of final treated gas raised from permissible limit, i.e., 3 ppm at least for three initial months of operation, and then progressively reduced to around 2 ppm. Systematic investigation of plant data shows that carbonyl sulfide hydrolysis in the dehumidification section as downstream of the sweetening section would increase the hydrogen sulfide content of the treated stream. Meanwhile, the gradual formation of heat stable amine salts in amine solution promotes its absorption capacity, which can counterpoise the effect of further hydrogen sulfide generation due to carbonyl sulfide hydrolysis in the subsequent section. Monitoring heat stable amine salts concentration in amine solution suggests that there should be a minimum level of 0.25 wt.% of these compounds to achieve suitable hydrogen sulfide content in final treated gas.

Influence of upgrading natural gas quality standard on purification plant

GB17820-2018 has been formally implemented, which puts forward higher requirements for the quality index of natural gas entering the long-distance pipeline network. It is required that the H2S in the first type of natural gas should be less than 6mg/m3 and the total sulfur should be less than 20mg/m3. Because of the high content of organic sulfur in feed gas, MDEA desulfurization can not meet the standard requirements in some purification plants. At present, sulfolamine solvent desulfurization, COS hydrolysis process and molecular sieve desulfurization process are often used to remove organic sulfur. The purification plant can meet the requirements of GB 17820-2018 through solvent upgrading and new process technology. However, each of the three technologies has its own advantages and disadvantages, which should be reasonably selected according to the feed gas situation of the purification plant.

Illuminating and alleviating cellular oxidative stress with an ROS-activated, H2S-donating theranostic

This paper is dedicated to Prof. Dale L. Boger on the occasion of his receipt of the 2020 Tetrahedron Prize for Creativity. Hydrogen sulfide (H2S) is an endogenous signaling molecule that has been shown to provide impressive antioxidative and cytoprotective effects. To further gauge its physiological and pathophysiological properties, small molecule donors with precise control over their H2S delivery within a biological setting are needed. Herein, we describe a novel, self-reporting H2S donor that is selectively activated by reactive oxygen species (ROS). Within our design, we append an ROS-responsive aryl boronate ester to 7-hydroxy-4-methylcoumarin via an S-alkyl thiocarbonate linkage—a key feature which provides the efficient release of both H2S (via COS hydrolysis) and a fluorescent reporter in response to elevated levels of ROS. Thus, this design was found to provide a useful bifunctional tool given its rare ability to simultaneously image and neutralize hydrogen peroxide within live cells.

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.

Syngas cleaning for coal to methanol demo plant – H2S and COS removal

Syngas cleaning, especially the removal of COS and H2S, is a crucial step in the production of valuable chemicals from coal. As a part of the Tuncbilek Coal to Methanol project, a gas cleaning demo plant has been built. The aim of this paper is to disseminate the experience gained from these demo plant experiments concerning the performance of the gasifier and syngas cleaning demo-plant, especially about the removal of sulfur compounds. Additionally, some practical recommendations regarding the design and operation of such demo plants are given. The design-basis for the demo plant was a gas stream of 450 m3/h (at STP) containing 4,000 ppmv H2S and 2,000 ppmv COS. The performance target was to reduce H2S and COS concentrations to less than one ppmv each. The gas cleaning process consisted of a particulate filter, COS hydrolysis reactors, caustic scrubbers, H2S guard beds and heat exchangers. Two demo plant runs were conducted, and Tuncbilek lignite was gasified in the 6 ton/day (coal feeding capacity) entrained flow gasifier. The gasifier produced syngases with lower heating values of 7.64 and 8.86 MJ/m3 (at STP), and cold gas efficiencies of 71 and 81% were achieved. The H2S and COS content of the successful run were 3,300 ppmv and 550 ppmv, respectively. At the exit of the gas cleaning demo plant, a concentration of 0.12 ppmv for H2S and 0.72 ppmv for COS were measured. Consequently, it was concluded that the performance of the gas cleaning demo plant was satisfactory for methanol production.

Mechanochemically synthesized MgAl layered double hydroxide nanosheets for efficient catalytic removal of carbonyl sulfide and H2S.

A solid-state mechanochemical route for rapid synthesis of MgAl layered double hydroxide (LDH) nanosheets large in surface area and decorated with abundant hydroxyl groups was developed for catalytic elimination of carbonyl sulfide and H2S, showing activity superior to those of commercial LDHs and porous metal oxides.