Xiaolong Tang

Simultaneous catalytic hydrolysis of carbonyl sulfide and carbon disulfide over Al2O3-K/CAC catalyst at low temperature

Abstract In this work, a series of coal-based active carbon (CAC) catalysts loaded by Al2O3 were prepared by sol-gel method and used for the simultaneous catalytic hydrolysis of carbonyl sulfide (COS) and carbon disulfide (CS2) at relatively low temperatures of 30–70 °C. The influences of calcinations temperatures and operation conditions such as: reaction temperature, O2 concentration, gas hourly space velocity (GHSV) and relative humidity (RH) were also discussed respectively. The results showed that catalysts with 5.0 wt% Al2O3 calcined at 300 °C had superior activity for the simultaneous catalytic hydrolysis of COS and CS2. When the reaction temperature was above 50 °C, catalytic hydrolysis activity of COS could be enhanced but that of CS2 was inhibited. Too high RH could make the catalytic hydrolysis activities of COS and CS2 decrease. A small amount of O2 introduction could enhance the simultaneous catalytic hydrolysis activities of COS and CS2.

Enhancement effects of ultrasound assisted in the synthesis of NiAl hydrotalcite for carbonyl sulfide removal.

Ultrasonic effect in the synthesis of catalysts of NiAl oxides prepared starting from the coprecipitation method of a hydrotalcite structure was evaluated in this work. Removal of carbonyl sulfide (COS) at low temperature over the hydrotalcite-derived oxides was studied. The samples were characterized by X-ray Diffraction (XRD), scanning electron microscope (SEM), N2 adsorption/desorption techniques, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and CO2 temperature-programmed desorption (TPD). It is found that hydrotalcite treated with ultrasonic has smaller average crystallite size and higher particle dispersion compared to hydrotalcite without ultrasonic treatment. As a result, mixed oxides derived from hydrotalcite treated with ultrasonic show more developed pore structure which is good for the physical adsorption of gaseous pollutant. The result of desulfuration test showed that removal efficiency of COS on the NiAl mixed oxides prepared by ultrasonic method (30min) is greater than that on the catalyst prepared without the ultrasonic irradiation assistance with the same aging time. One important reason for the high activity is that when the ultrasonic is used the number of weak basic sites (OH(-) groups) and moderate basic sites (M-O) was increased, whereas the number of strong basic sites (O(2-)) was decreased. Therefore, ultrasonic treatment promoted the COS hydrolysis and suppress the poisoning of the catalyst.

Simultaneous Removal of SO2, NO, and CO2 on Metal-Modified Coconut Shell Activated Carbon

Simultaneous removal of SO2, NO, and CO2 from simulate flue gas was examined in this study. The sorbents were prepared by coconut shell activated carbon (SAC) and impregnated with metal nitrates (Cu, Ca, Mg, Zn). The adsorptive performance of sorbents was studied. The performances of these sorbents were not in agreement on adsorption of SO2, NO, and CO2. Cu-SAC seemed to be a promising sorbent through the calculation of adsorption capacity. Effect of different feed gases on adsorption activity of Cu-SAC was also studied. It indicates that CO2 impacts the adsorption of SO2 and NO but limited. O2 is the key to co-adsorption as its good oxidation capacity. The adsorbed SO2 and NO can interact with each other so as to form intermediate species under the influence of O2, which facilitates SO2 and NO oxidized to SO3 and NO2, respectively.

NO removal in the process of adsorption non-thermal plasma catalytic decomposition

The interesting process of adsorption NTP catalytic decomposition (ANCD) was used for NO removal without external heating. NO removal by NTP alone, NTP assisted catalytic decomposition (NCD) and ANCD were each studied for comparative purposes. The energy efficiency, NO removal efficiency and discharge power of these processes were investigated. Compared with the other two processes, outstanding experimental results were achieved by the ANCD process. Using this process, three different catalysts were also investigated. The results showed that the adsorption properties of the catalyst play a key role in the ANCD process. In addition, the influence of NO concentration on the conversion of NO was not appreciable. When the flow was too large, the residence time of pollutants in the catalyst decreased, resulting in a reduction in its adsorption capacity for pollutants and a decrease in the NO conversion and energy efficiency.

One-step synthesis, characterization and catalytic performance of hierarchical Zn-ZSM-11 via facile ZnO routes

Hierarchical Zn-ZSM-11 zeolite with an olive-shaped intergrowth morphology was synthesized via a novel and facile one-step hydrothermal method by using tetrabutylammonium bromide (TBABr) and zinc oxide (ZnO) as a difunctional template and zinc source, respectively. Structural characterizations (XRD, IR, TG-DTA, SEM, and N2 adsorption–desorption) were conducted to analyze the textural properties of Zn-ZSM-11 samples. Compared with the Zn containing ZSM-11 samples prepared by other methods (ZnSO4 method, ZnO-impregnated-seed method and impregnation method), the Zn-ZSM-11 prepared by ZnO method exhibited enriched mesopores as well as good catalytic activity in methanol conversion. TEM images showed that Zn species were well incorporated into the zeolite framework, while the different morphology of Zn-ZSM-11 from ZSM-11 further verified that the Zn species had been involved in the formation of the ZSM-11 framework. 27Al and 29Si MAS NMR spectra revealed that Zn species in the zeolite framework significantly impacted the coordination of Si. The XRD pattern variation of the ZnO containing gel was also tracked to illustrate the crystallization process. It was found that the ZnO would be gradually dissolved under the severely alkaline environment and subsequently incorporated into the ZSM-11 framework in the crystallization process. This facile new synthesis strategy can also be extended to prepare other Zn containing zeolites and is potentially important for practical utilization.

Novel synthesis of MeOx (Ni, Cu, La)@Nano-Co3O4 from combination of complexation and impregnation in ultrasonic intervention for low temperature oxidation of toluene under microwave radiation

Nano-metal binary oxides were prepared by the combined method of complexation and impregnation in ultrasonic intervention for low temperature catalytic oxidation of toluene under microwave radiation. Activity differences of prepared samples were evaluated using the removal rate and the mineralization rate as assessment criteria. Results show that the sample derived from the introduction of La and intervention of ultrasonic presents the best catalytic performance, which the removal rate of 80% can be obtained at 120°C and the mineralization rate of 97% can be obtained at 210°C. Compared with the worst sample at low temperature, maximum increases of removal rate and mineralization rate using the sample of La-Co (US) are 3.47 and 11.79 times respectively. Lowest values of T90 based on removal rate and mineralization rate are 140°C and 195°C, respectively. Compared with the sample that ultrasonic treatment is not applied in impregnation process, maximum increases of removal rate and mineralization rate using the sample of La-Co (US) are 17.43% and 85.19% respectively. Moreover, Diagrams of XRD, EDX and TEM indicate that metal binary oxides nano-particles are synthesized successfully. The data of SEM and XPS manifests that the sample of La-Co (US) possesses the smallest particle size distribution, the highest levels of the Co2+/Co3+ and the Olatt/Oads. In addition, significant differences of catalytic activities are not observed after three cycles indicating that the sample possesses good stability and recycling.

Behaviors and kinetics of toluene adsorption‐desorption on activated carbons with varying pore structure

This work was undertaken to investigate the behaviors and kinetics of toluene adsorption and desorption on activated carbons with varying pore structure. Five kinds of activated carbon from different raw materials were selected. Adsorption isotherms and breakthrough curves for toluene were measured. Langmuir and Freundlich equations were fitted to the equilibrium data, and the Freundlich equation was more suitable for simulating toluene adsorption. The process consisted of monolayer, multilayer and partial active site adsorption types. The effect of the pore structure of the activated carbons on toluene adsorption capacity was investigated. The quasi-first-order model was more suitable for describing the process than the quasi-second-order model. The adsorption data was also modeled by the internal particle diffusion model and it was found that the adsorption process could be divided into three stages. In the external surface adsorption process, the rate depended on the specific surface area. During the particle diffusion stage, pore structure and volume were the main factors affecting adsorption rate. In the final equilibrium stage, the rate was determined by the ratio of meso- and macro-pores to total pore volume. The rate over the whole adsorption process was dominated by the toluene concentration. The desorption behavior of toluene on activated carbons was investigated, and the process was divided into heat and mass transfer parts corresponding to emission and diffusion mechanisms, respectively. Physical adsorption played the main role during the adsorption process.

The byproduct generation analysis of the NOx conversion process in dielectric barrier discharge plasma

Abatement of NOx through non-thermal plasma (NTP) processes has been developed over the past several years. Since discharge plasma contains a large amount of highly active species during the reaction process, NOx is removed during our desired conversion reaction, as well as production of other byproducts, such as O3 and N2O. The effect of reaction conditions, such as oxygen content, discharge power, operation time, initial NO concentration and gas residence time, on generation characteristics of O3 and N2O was investigated. Results showed that, with increasing oxygen concentration and discharge power, the production of N2O and O3 increases. Additionally, O3 concentration decreases with increasing operation time; the higher input power, the higher the temperature increases, causing a greater reduction rate of O3, which also leads to a reduction of NO2 production. NO concentration and gas residence time also exert effects on the generation of byproducts.

Nitric oxide decomposition using atmospheric pressure dielectric barrier discharge reactor with different adsorbents

A cycled adsorption–desorption and decomposition process (ADD) for removing NOx was designed and performed using a dielectric barrier discharge (DBD) reactor filled with NaY zeolite or activated carbon as adsorbent at ambient temperature. Simulated flue gas was introduced into the DBD reactor for adsorption (Ta). Non-thermal plasma (NTP) was applied to detach and decompose the adsorbed NO for a specific period (Td). Some key operating conditions (adsorbent materials, discharge power, Td, and so on) were investigated to optimize the ADD process, and the effects of H2O and O2 were also studied. NO conversion, NO2 formation, and energy efficiency of different NTP-assisting DeNOx technologies were compared. The experimental results demonstrated that an NO removal rate of 99% was obtained on NaY zeolite at an energy efficiency of 99.4 g NO per kW h using the ADD process.

Simultaneous adsorption of SO2 and NO from flue gas over mesoporous alumina

Mesoporous alumina (MA) with a higher ability to simultaneously remove SO2 and NO was prepared by the evaporation-induced self-assembly process. The adsorption capacities of MA are 1.79 and 0.702 mmol/g for SO2 and NO, respectively. The Brunauer–Emmett–Teller method was used to characterize the adsorbent. Simultaneous adsorption of SO2 and NO from flue gas over MA in different operating conditions had been studied in a fixed bed reactor. The effects of temperature, oxygen concentration and water vapour were investigated. The experimental results showed that the optimum temperature for MA to simultaneously remove SO2 and NO was 90°C. The simultaneous adsorption capacities of SO2 and NO could be enhanced by increasing O2 when its concentration was below 5%. The changes of simultaneous adsorption capacities were not obvious when O2 concentration was above 5%. The increase in relative humidity results in an increase after dropping of SO2 adsorption capacity, whereas the adsorption capacity of NO showed an opposite trend. The results suggest that MA is a great adsorbent for simultaneous removal of SO2 and NO from flue gas.