MnO_2陶粒臭氧氧化催化剂的制备及其性能

以凹凸棒土为载体、MnO_2为活性组分,制备了MnO_2陶粒臭氧氧化催化剂,并以草酸为模拟污染物,采用响应面法对催化剂的制备条件进行了优化。实验结果表明:各因素对草酸去除率影响的显著性顺序为MnO_2投加量>盐酸溶液质量分数>煅烧时间>煅烧温度。催化剂的最佳制备条件为:MnO_2投加量200 mg/g,盐酸溶液质量分数20%,煅烧时间2 h,煅烧温度400℃。在初始草酸质量浓度150 mg/L、溶液pH 3.11、臭氧投加量8.10 mg/min、臭氧-氧气曝气量400 m L/min的条件下,最佳条件制备的催化剂在反应30 min时的草酸去除率达66.99%。催化剂具有良好的活性稳定性,且催化过程中Mn^(2+)溶出量低。催化剂具有较大的比表面积,负载的MnO_2类型为α-MnO_2和β-MnO_2。

Promotional effect of spherical alumina loading with manganese-based bimetallic oxides on nitric-oxide deep oxidation by ozone

Nitric oxide （NO） deep oxidation to dinitrogen pentoxide （N2O5） by ozone together with wet scrub-bing has become a promising technology for nitrogen-oxide （NOx） removal in industrial boilers. Catalysts were introduced to enhance the N2O5 formation rate with less ozone injection and leakage. A series of monometallic catalysts （manganese, cobalt, cerium, iron, copper, and chromium） as pre-pared by the sol-gel method were tested. The manganese oxides achieved an almost 80% conver-sion efficiency at an ozone （O3）/NO molar ratio of 2.0 in 0.12 s. The crystalline structure and porous parameters were determined. The thermodynamic reaction threshold of NO conversion to N2O5 is oxidation with an O3/NO molar ratio of 1.5. Spherical alumina was selected as the support to achieve the threshold, which was believed to improve the catalytic activity by increasing the surface area and the gas-solid contact time. Based on the manganese oxides, cerium, iron, chromium, cop-per, and cobalt were introduced as promoters. Cerium and iron improved the deep-oxidation effi-ciency compared with manganese/spherical alumina, with less than 50 mg/m3 of outlet NO ＋ nitro-gen oxide, and less than 25 mg/m3 of residual ozone at an O3/NO molar ratio of 1.5. The other three metal oxides inhibited catalytic activity. X-ray diffraction, nitrogen adsorption, hydrogen tempera-ture-programmed reduction, and X-ray photoelectron spectroscopy results indicate that the cata-lytic activity is affected by the synergistic action of NOx oxidation and ozone decomposition.

A novel process of ozone catalytic oxidation for low concentration formaldehyde removal

To reduce energy costs,minimize secondary pollution from undecomposed ozone,and improve the efficiency of ozone use,a novel process of cycled storage‐ozone catalytic oxidation(OZCO)was employed to remove formaldehyde(HCHO)at low concentrations in air.We applied Al2O3‐supported manganese oxide(MnOx)catalysts to this process,and examined the HCHO adsorption capacity and OZCO performance over the MnOx catalysts.Owing to the high dispersion of MnOx and low oxidation state of manganese,the MnOx/Al2O3catalysts with a manganese acetate precursor and10%‐Mn loading showed good performance in both storage and OZCO stages.The presence of H2O led to a decrease of the HCHO adsorption capacity owing to competitive adsorption between moisture and HCHO at the storage stage;however,high relative humidity(RH)favored complete conversion of stored HCHO to CO2at the OZCO stage and contributed to an excellent carbonbalance.Four low concentration HCHO storage‐OZCO cycles with a long HCHO storage period and relatively short OZCO period were successfully performed over the selected MnOx/Al2O3catalyst at room temperature and a RH of50%,demonstrating that the proposed storage‐OZCO process is an economical,reliable,and promising technique for indoor air purification.

Efficiency and mechanism of degradation of alachlor in water by O_3/H_2O_2 catalyst system

Alachlor is used widely as a herbicide,but is an environmental endocrine disruptor. O 3/H 2O 2 system is used as catalyst to delve on the degradation efficiency of alachlor. The amount of the catalyst H 2O 2,the pH value of the soluble, the temperature and quality of water sample are changed to investigate the effect of these factors on the degradation of alachlor. The degradation of alachlor is qualitatively analyzed through their GS MS spectra and the possible mechanism of the degradation of alachlor is discussed as well.