The Catalytic Mechanism of Intercalated Chlorine Anions as Active Basic Sites in Mgal-layered Double Hydroxide for COS Hydrolysis

In order to make clear the role of intercalated anions in layered double hydroxides (LDHs) for catalytic hydrolysis of 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.

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

Mechanochemically prepared MgAl-LDH nanosheets with high crystallinity and large surface areas show excellent activities in COS hydrolysis and H2S oxidation.

Numerical Modeling and Performance Prediction of COS Hydrolysis Reactor in an Integrated Gasification Fuel Cell in terms of Thermo-Chemical Transport Phenomena

During the recent decades, global warming by greenhouse gas evolution has attracted worldwide attention and ever increasing strict regulations thereon have become institutionalized as international policies. In the process, more environment-friendly power generation technologies have been developed utilizing fossil fuels with a view to timely commercialization. As one such “clean coal” technology, an Integrated Gasification Fuel Cell system is a promising power generation means where a carbonyl sulfide (COS) hydrolysis reactor is installed downstream of coal syngas to remove acidic gas constituents such as H2S and COS. The most significant design parameters affecting performance of the COS hydrolysis reactor were selected to be gas hourly space velocity (GHSV), reaction temperature, and length ratio, and numerical modeling was performed considering heat and fluid flow transfer as well as chemical reaction kinetics. Effect of the selected design parameters on the variation of conversion rate and reactant gas mixture concentration were comprehensively investigated to predict performance of the COS hydrolysis reactor. Stochastic modeling of reactor performance was finally performed using Monte Carlo simulation and linear regression fitting.

Numerical Modeling and Performance Prediction of COS Hydrolysis Reactor in Integrated Gasification Fuel Cell in terms of Thermo-Chemical Transport Phenomena

During the recent decades, global warming by greenhouse gas evolution has attracted worldwide attention and evermore strict regulations thereon have become institutionalized as international policies. In the process, more environment-friendly power generation technologies have been developed utilizing fossil fuels with a view to timely commercialization. As one of such “clean coal” technology, Integrated Gasification Fuel Cell system is a promising power generation means and COS hydrolysis reactor is installed downstream of coal syngas to remove acidic gas constituents such as H2S and COS. The most significant design parameters affecting performance of the COS hydrolysis reactor were selected to be GHSV, (catalytic) reaction temperature, and length ratio and numerical modeling was performed considering heat and fluid flow transfer as well as chemical reaction kinetics. Effect of the selected design parameters on the variation of conversion rate and reactant gas mixture concentration were comprehensively investigated to predict performance of COS hydrolysis reactor. Stochastic modeling of reactor performance was finally performed using Monte Carlo simulation and linear regression fitting.

The Hydrolysis of Carbonyl Sulfide at Low Temperature: A Review

Catalytic hydrolysis technology of carbonyl sulfide (COS) at low temperature was reviewed, including the development of catalysts, reaction kinetics, and reaction mechanism of COS hydrolysis. It was indicated that the catalysts are mainly involved metal oxide and activated carbon. The active ingredients which can load on COS hydrolysis catalyst include alkali metal, alkaline earth metal, transition metal oxides, rare earth metal oxides, mixed metal oxides, and nanometal oxides. The catalytic hydrolysis of COS is a first-order reaction with respect to carbonyl sulfide, while the reaction order of water changes as the reaction conditions change. The controlling steps are also different because the reaction conditions such as concentration of carbonyl sulfide, reaction temperature, water-air ratio, and reaction atmosphere are different. The hydrolysis of carbonyl sulfide is base-catalyzed reaction, and the force of the base site has an important effect on the hydrolysis of carbonyl sulfide.