[Comparison and Analysis of PM2.5 Forecast in Key Areas Based on the Neural Network Model and Numerical Model].

The PM2.5 forecast models of 95 cities in Beijing-Tianjin-Hebei and its surrounding cities (BTH); the Fenwei Plain (FWP); the border area of Jiangsu, Anhui, Shandong, and Henan (JASH); and the Yangtze River Delta (YRD) regions were established using BP neural network models, and the forecast was carried out for the next seven days in the autumn and winter in 2020. By comparing the forecast results of the BP neural network models, numerical model, and artificial correction, the PM2.5 forecast effects of the three methods were analyzed and evaluated. The results showed:① The performance of the short-term forecast based on the BP neural network was relatively good but was reduced in the medium and long term and systematically overestimated in four regions. The numerical model effects were lower than those of the BP neural network models. ② The accuracy rates of the PM2.5 forecast concentration by the three methods were generally low in the four regions, with an average of less than 50%, and the accuracy values in order from high to low were the BP neural network models, artificial correction, and the numerical model. The accuracy rates of IAQI levels of PM2.5 were significantly improved by the three methods, and the averages were above 65% in the first four days. The effects of the BP neural network models and artificial correction were similar, which were generally higher than those of the numerical model. ③ The numerical model had good effects in the BTH, JASH, and YRD regions, whereas it was the worst when forecasting moderately and above-polluted days in the FWP region. The BP neural network model had a good performance when forecasting short-term PM2.5 in the BTH, JASH, and FWP regions, whereas it was poor in the YRD region. In general, the performance of artificial correction was relatively good when forecasting moderate-level days and was close to the BP neural network model when forecasting heavily polluted days.

Study of reaction mechanism based on further promotion of low temperature degradation of toluene using nano-CeO2/Co3O4 under microwave radiation for cleaner production in spraying processing.

Cleaner production in spraying processing was presented by advanced low temperature oxidation technology using combined methods of microwave radiation and nano-composites. Activities of samples for oxidation of toluene were estimated and the result exhibited that application of microwave radiation and nano-materials greatly promoted activities of catalysts. Moreover, the doping of Ce further enhanced catalytic activities. Samples of 5% Ce-Co showed optimal activity with conversion rate of 70% and CO2 selection of 96% at 120 ℃ and 210 ℃, respectively. The lowest Ea (33.45 kJ/mol) was obtained calculating from kinetics process under microwave radiation using 5% Ce-Co indicating that the degradation of toluene might proceed more readily. Microwave absorption properties were first used tentatively to study the effect of "hot spots" induced by microwave radiation on catalytic oxidation of VOCs. Further, physicochemical properties of samples were also showed by XRD, SEM and XPS profiles to study oxidation activities of toluene. The maximum difference of toluene oxidation between no water and in water using 5% Ce-Co at 210 ℃ was only 3.06% manifesting that effects of moisture on activities were weak under microwave radiation. A possible degradation track using microwave heating was presented by the analysis of reaction byproducts using the GC-MS.

Mn-CeOx/MeOx(Ti, Al)/cordierite preparation with ultrasound-assisted for non-methane hydrocarbon removal from cooking oil fumes.

Cooking oil fumes (COFs) which contains a variety of volatile organic compounds (VOCs) is noxious not only to the environment but also to human health. Among COFs, the Non-methane Hydrocarbon (NMHC) removal rate is an index of the removal rate of COFs in the latest COFs purification standard (DB 11/1488-2018). Ultrasonic treatment can assist the synthesis of catalysts by creating "cavitation", which can improve the surface microtopography of catalysts. The research results in this paper revealed that the NMHC conversion of catalysts with ultrasonic treatment increased significantly. Besides, the samples that coated TiO2 had a higher conversion of NMHC than that coated Al2O3 because TiO2 has better oxidation performance than Al2O3. According to the XPS, SEM, EDS and BET data, because of the enhancement of interaction of the active components of catalysts caused by ultrasonic intervention, T-UU-CTAB exhibited the best catalytic performance, which attributed to the high levels of Mn4+/Mn3+, Ce4+/Ce3+ and Oads/Olatt, more developed pore structure owing to the smaller particle size, higher dispersion of active components, larger specific surface area and larger total pore volume produced by the ultrasonic treatment. Moreover, the conversion of NMHC over T-UU-CTAB is 93.6% at 400 °C.

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

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.

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 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.

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.