The reactions of soot with gaseous and adsorbed NO2were tested over the K/MgAlO catalyst.After the reaction intermediates were identified by combination of in situ IR characterization and first-principles calculation,the different mechanisms were elucidated.It was found that the reactivity of adsorbed NO2is lower than that of the gas form.The adsorbed NO2reacts with soot in the form of nitrates,leading to the observation of two IR bands at 2,234and 2,110 cm-1,which are ascribed to the vibration frequencies of cyanates on K sites and cyanides on the MgAlO support,respectively.On the contrary,the isocyanates were confirmed as intermediates in the reaction of soot with gaseous NO2.Because the adsorbed NO2species(i.e.,nitrates)are restricted by the electrostatic field of K+,the cyanates are produced and readily cracked into cyanides,which transfer to the MgAlO support.The gaseous NO2favours the production of isocyanates due to their higher stability.The weaker reactivity of adsorbed NO2at lower temperatures can be attributed to the restriction of the electrostatic field of K+.
Octylphenols, considered as xenoestrogens, mainly exist as 4-tert-octylphenol (OP) in aquatic environments. The high stability and accumulation of OP in aquatic systems have caused endocrine disruption. The OP in surface water in Jinan, China was analyzed by gas chromatography-mass spectrometry (GC-MS) coupled with solid phase extraction (SPE). Water samples were extracted by SPE on a cartridge system containing C-18 as sorbent. To increase sensitivity and selectivity, OP was derivatized to 4-tert-octyl-phenoxy silane. With the use of phenanthrene-d10 as internal standard, the detection limit based on signal-to-noise ratio (S/N = 3) was 0.06 ng/mL. The average recovery was from 84.67% to 109.7%. The precision of the method given as the relative standard deviations (RSD) was within the range 6.24%-12.96%. In the target water samples, the concentrations of OP were as follows: 15.88-71.24 ng/L for Jinxiuchuan Reservoir, 3.850-26.68 ng/L for the city moat, 6.930-41.56 ng/L for Daming Lake, 66.03-474.2 ng/L for Xiaoqing River, 14.66-17.72 ng/L for the Yellow River, and 10.60-26.43 ng/L for Queshan Reservoir. The Xiaoqing River was seriously polluted due to the discharge of wastewater from Jinan. Jinxiuchuan Reservoir had a higher concentration of OP compared with the Yellow River and Queshan Reservoir, which is ascribed to the surrounding human activities. These data are reported for the first time, providing strong support for the control of OP pollution in Jinan.
A series of MnMgAlO samples with different amounts of Ce doping were facilely prepared using coprecipitation method and their catalytic soot combustion activity was evaluated by temperature programmed oxidation reaction(TPO).The methods of X-ray diffraction(XRD),Brumauer-Emmett-Teller(BET),H2-TPR,NO-TPO and in situ IR were used to characterize the physiochemical properties of these samples.Dopant Ce improved the soot combustion performance of MnMgAlO catalyst due to the enhanced redox ability.Introduction of NOx led to the further increase of catalytic soot oxidation activity on these samples.Over Ce-containing samples,the catalytic activity was slightly decreased as the amount of dopant Ce increased in O2.Differently,in NO+O2,a certain amount of dopant Ce was much more favorable and excess amount of Ce resulted in a sharp drop of the catalytic soot combustion activity.Both NO2 and nitrates were found to have great contributions to the effects of NOx on the soot combustion activity of Ce-doped catalysts.More NO2 was generated as dopant Ce increased.When appropriate amount of Ce was introduced,the as-formed NO2 was stored as bridging bidentate nitrate on Mn-Ce site,which was confirmed to have higher reactivity with soot than nitrite or monodentate nitrate on Mn and/or Ce sites.Overall,Mn0.5Mg2.5Ce0.1Al0.9O was considered as the most potential catalyst for soot combustion.
