Fengyu Gao

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.

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.

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.

Using CuO-MnO x /AC-H as catalyst for simultaneous removal of Hg° and NO from coal-fired flue gas

A series of CuO-MnOx modified catalysts were prepared, and proposed for simultaneous removal of Hg° and NO from flue gas. As Mn loading value was 5%, the high value of 90% Hg and 60% NOx were removed efficiently. With gradual increasing of reaction temperature, the mercury removal efficiency (Mercury RE) first increased to 92% then decreased slightly, while NOx removal efficiency (NOx RE) exhibited a trend of continuous increase. O2 had promotional effect on the double pollutants removal, while NH3 had slightly negative effect on Hg° removal. As 5% O2 was added into system, the removal efficiency of Hg and NOx rose by 30% and 47%, respectively. Unfortunately, Mercury RE decreased to 90% in the presence of 500 ppm NH3. Overall, superior Mercury RE (>90%) and NOx RE (78%) were performed over 8%CuO-5%MnOx/AC-H at 200 °C. XRD results revealed calcination affected catalysts activity by playing a role in active components formation at different temperature. In XPS spectra, new formation of HgO and Hg° adsorption on spent catalysts revealed the possible reaction processes that the conversion of CuO and MnO2 on fresh catalyst to other species benefited HgO formation. The removal mechanism might be a combination of Langmuir-Hinshelwood and Mars-van-Krevelen mechanism.

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.