Shunzheng Zhao

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.

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.

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.

Removal of Toluene from Industrial Gas by Adsorption–Plasma Catalytic Process: Comparison of Closed Discharge and Ventilated Discharge

Degradation of adsorbed toluene over 13X zeolite, 5A molecular sieve and Al2O3 by non-thermal plasma was investigated. Different discharge modes, including closed and ventilated discharge were compared. The carbon balance and COx yield of 13X zeolite were increased by 17.6 and 19.4% by ventilated discharge, respectively, compared with closed discharge. But for 5A molecular sieve and Al2O3, the carbon balance and COx yield by closed discharge were greater than those by ventilated discharge. It meant that the closed discharge was more suitable for low-concentration of VOC and the residence time of reactants would be prolonged. Removal of high-concentration VOC by ventilated discharge was more appropriate because of more reactive oxygen species generated. Furthermore, the effect of discharge background gas was studied. Removal of adsorbed toluene over Co/13X by oxygen and air with different flow rate as background gas were compared. The removal efficiency was reduced as flow rate of background gas increased. The oxygen-discharge was more efficiency for toluene oxidation and inhibited the generation of nitrogen oxides.

Removal of volatile odorous organic compounds over NiAl mixed oxides at low temperature

In this paper, a series of NiAl hydrotalcite-like compounds (HTLCs) were prepared by the urea-decomposition method. Removal of carbonyl sulfide (COS) and methyl mercaptan (CH4S) over the hydrotalcite-derived oxides (HTO) at low temperature was studied. The Ni3Al-HTO exhibited higher catalytic activities than Ni3Al mixed oxides prepared by physical mixing method (Ni3Al-PM) or impregnation/calcination method (Ni3Al-IC). Based on the characterization, it was found that desulfurization activities are closely tied to the surface acid-base properties of catalysts. CO2-TPD indicates that the basic characteristic of the Ni3Al-HTO is prominent. XPS results showed that there was a strong interaction between Ni and Al element on Ni3Al-HTO. The first principle calculation based on density function theory was applied with the aim to study the change of basic sites. The results showed that Ni3Al-HTO presents a half-metallic characteristic. Electron transfer from the Al and O atom to the Ni atom was observed, which is helpful for the transfer of electrons from the surface and improves the catalytic activity. Analysis of the DRIFT spectra suggests that sulfate species was formed by the action of surface basic sites, resulting in the formation of H2O on the surface.

Novel synthesis of Pd-CeMnO 3 perovskite based on unique ultrasonic intervention from combination of Sol-Gel and impregnation method for low temperature efficient oxidation of benzene vapour

The 0.5 wt% Pd-CeMnO3 was prepared by ultrasonic intervention combination of Sol-Gel and PVA-protected N2 bubbling NaBH4 reduction impregnation method, then it was used for the catalytic oxidation of benzene vapour at low temperatures. By analyzing the removal and mineralization rate at different temperatures, it was found that 50% of benzene was degraded in 145 °C, then 90% of benzene was degraded in 186 °C, 100% of mineralization rate was 220 °C. After ultrasonic treatment, 64% removal rate and 46% mineralization rate could be increased, it proved that ultrasonic treatment can improve the performance of catalyst significantly. According to XRD spectrum, ultrasonic intervention helped to stabilize the crystalline structure of perovskite. Further, SEM pictures intuitively proved that ultrasonic treatment contributes to the formation of surface pore structure of catalyst. Moreover, diagram of H2-TPR indicates that ultrasonic intervention makes the catalyst have more cryogenic activity sites for strong low temperature catalytic activities. All these reasons are assumed to be the factors that lead to superior performance of the catalyst.

Cordierite supported metal oxide for Non-methane hydrocarbon oxidation in cooking oil fumes

ABSTRACT Cooking emission is an important reason for the air quality deterioration in the metropolitan area in China. Transition metal oxide and different loading of manganese oxide supported on cordierite were prepared by incipient wetness impregnation method and were used for non-methane hydrocarbon (NMHC) oxidation in cooking oil fumes (COFs). The effects of different calcination temperature and different Mn content were also studied. The SEM photographs and CO2 temperature-programmed desorption revealed 5 wt% Mn/cordierite had the best pore structure and the largest number of the weak and moderate basic sites so it showed the best performance for NMHC oxidation. XRD analysis exhibited 5 wt% Mn/cordierite had the best dispersion of active phase and the active phase was MnO2 when the calcination temperature was 400℃ which were good for the catalytic oxidation of NMHC. GRAPHICAL ABSTRACT

Studies on the calcium poisoning and regeneration of commercial De-NO x SCR catalyst

The poisoning effect of calcium on a commercial De-NOx SCR catalyst (V2O5–WO3/TiO2) and the regeneration process of deactivated catalysts via water or H2SO4 washing were investigated under simulated condition in laboratory. The physicochemical properties of the catalysts were characterized by SEM–EDX, XRD, BET, TPD and FT-IR measurements, and the deactivation mechanism was discussed. The poisoning of calcium was attributed to the coverage of active sites and the reduction of acid sites on the surface of catalyst. The change of V=O bonds on catalyst surface was an important reason, which plays a significant role in the catalytic cycle of SCR. Due to the suction deliquescence of CaO to Ca(OH)2, the catalytic activity of deactivated catalyst can be finitely recovered by water washing. Besides, as the result of the re-exposure of active sites by washing CaO off and the promotional effect of surface sulfation, the process of regeneration via sulfuric acid washing has a favorable effect in the experiment.