硝基苯精制再沸器爆炸事故的探讨

分析了硝基苯精制再沸器爆炸的原因,探讨了如何防止硝基苯精制再沸器的爆炸事故,并提出硝基苯生产安全运行的预防措施。     

Photocatalytic degradation of nitrobenzene using titanium dioxide and concentrated solar radiation: chemical effects and scaleup

Photocatalytic degradation of nitrobenzene (NB) using titanium dioxide (Degussa P-25) as photocatalyst and concentrated solar radiation has been studied. The effects of various factors, such as the presence of anions common in the industrial wastewater, the initial pH and the addition of FeSO(4), were investigated. The intermediates detected were o, p,m-nitrophenols and dihhydroxy derivatives indicating that degradation proceeds via z.rad;OH radicals. Degradation of NB was studied in three reactors of different diameters to ascertain the effect of photon penetration depth on the degradation.     

再生温度对硝基苯加氢催化剂活性的影响

介绍了硝基苯加氢催化剂在使用过程中的活性变化与再生方法,通过模拟工业再生状况的实验,探讨了再生温度对该催化剂活性的影响。     

The effect of humic acids on nitrobenzene oxidation by ozonation and O3/UV processes

Three types of commercially available humic acids from different sources were used to simulate natural organic matter in water for the investigation of nitrobenzene oxidation by ozonation and O(3)/UV. Despite the structural differences among the Fluka, Aldrich and Suwanee River humic acids as reflected by the UV absorptivity, their effects on nitrobenzene removal rate was observed to be similar for the two processes. Removal rate of nitrobenzene was hindered by the addition of humic acids in ozonation as well as in O(3)/UV processes. However, the hindrance by the humic acids was more pronounced in O(3)/UV as compared to the ozonation process. The effect of humic acid in O(3)/UV was primarily a UV light screening. Addition of humic acids above a certain concentration did not cause any further retardation on nitrobenzene removal rate by ozonation and O(3)/UV.Accumulation of hydrogen peroxide as well as probable formation of peroxy radicals in the solutions might induce chain promoting reactions to produce hydroxyl radical during the nitrobenzene oxidation. For waters containing high levels of humic acid, ozonation alone might be as effective as O(3)/UV process for the removal of nitrobenzene.     

含硝基苯、苯胺工艺废水的处理方法

含硝基苯、苯胺工艺废水毒性大稳定性强、生化性差,采用普通方法很难处理,本文采用铁碳预处理加生化处理工艺方法,达到排放标准。     

Preliminary Results on Ozonation Enhancement by a Perfluorinated Bonded Alumina Phase

A preliminary study was undertaken in order to determine the efficiency of ozonation in the presence of perfluorooctylalumina (PFOA) for the removal of organic substances from aqueous solutions by ozone. PFOA was synthesized by reacting hydrated alumina with pentadecafluorooctanoic acid. A monomolecular layer of non-polar perfluorinated alkyl chains, orientated away from the surface of alumina, capable of dissolving ozone and organic molecules, was obtained. The efficiency of ozonation alone and ozonation in the presence of PFOA or Al₂O₃ was compared. PFOA was found to significantly enhance the degradation level of organic substances in comparison with ozonation alone. Al₂O₃ did not show any catalytic activity.     

Removal of Aromatic Nitro Compounds from Water by Ozonation

Experimental studies were carried out on the removal of five species of aromatic nitro hydrocarbons by ozonation. Ultraviolet spectrograms with distinct absorption peaks were plotted for each of them. It has been found that the absorbances of aqueous solutions containing the single compounds mentioned above increase to different extents at the wave lengths ranging from 200 to 230 nanometers with increase of ozone dosages. This is ascribed to the nitrite ions splitting out of the benzene rings and being further oxidized to nitrate ions by ozonation.

It has been indicated that the removal of the five species of aromatic nitro compounds by ozonation can well be expressed mathematically by first order reaction equations. Besides, the reaction constants and half-life periods for various species of the tested nitro compounds were calculated at different temperatures and pH.

An ozonation effect index (OI) was developed in the study to express the degree of degradation of substrates by ozonation, by means of which the five aromatic nitro hydrocarbons were compared with each other and finally ranked in the following order from greatest to smallest degrees of degradation:

p-nitroaniline > nitrobenzene > p-dinitrobenzene > p-nitrotoluene > m-dinitrobenzene

It has also found that the CODm/M ratio increases with ozone doses. This means that some easily degradable intermediates are produced, and increase in concentration with increase of ozone dose in the ozonation process.

The mechanisms of removing the five aromatic nitro hydrocarbons are discussed from the viewpoint of orienting effects of substituent groups on the aromatic rings.     

Heterogeneous hydrogenation of nitrobenzenes over recyclable Pd(0) nanoparticle catalysts stabilized by polyphenol-grafted collagen fibers

A novel heterogeneous palladium (Pd) nanoparticle catalyst stabilized by collagen fibers (CF) was synthesized. Epigallocatechin-3-gallate (EGCG), a typical natural polyphenol, was grafted onto the CF surface to improve the stabilization and immobilization of Pd(0) nanoparticles. The main physical and chemical properties of the catalyst were characterized by means of Scanning Electron Microscopy, Fourier Transform-Infrared Spectroscopy, X-ray Photoelectron Spectroscopy, X-ray Diffraction and Transmission Electron Microscopy. This catalyst is in an ordered fibrous state with high flexibility. The Pd(0) nanoparticles with diameters of 3–4 nm are homogeneously dispersed onto the outer surfaces of CF, and they are stabilized by the coordinative interactions between the surface Pd atoms of nanoparticle and the surrounding oxygen and nitrogen atoms of the EGCG-grafted CF. These stabilized Pd(0) nanoparticles were found to be active and selective catalysts for nitrobenzene and its derivatives, directly hydrogenating to the correspondingly reductive anilines under mild conditions. Both Pd particle size and activity of the catalyst showed a marked dependence on the grafting degree of EGCG on CF. These catalysts can be easily recovered, reused multiple times, and stored for two months in air while maintaining high catalytic efficiencies. All these facts suggest that the EGCG-grafted CF can be used as an effective stabilizer for the preparation of Pd(0) nanoparticle catalysts.     

Three-phase electrochemistry with a hanging drop of water-insoluble liquid: Precipitation of decamethylferrocenium species as a marker of ion transfer route

A recently developed new experimental setup for the three-phase voltammetry was used to detect the follow-up reaction products. Decamethylferrocene was dissolved in a nitrobenzene drop while inorganic salts with various anions were present in the aqueous phase. The third phase was represented by a Pt microcylindrical electrode. The drop was punctured by this electrode to various depths. The reported experiments show how the contribution of migration to the anion transport in the organic phase increases while the puncture depth grows. The use of the new three-phase electrode allowed easy removal of the microcylinder from the cell and optical inspection of its surface. It appeared that the oxidation of decamethylferrocene may be followed by the precipitation of its salts with the corresponding anions. The precipitate was identified by voltammetry and Raman spectroscopy. The length of the wire covered by the precipitate is relatively big in the case of perchlorate and very small (practically the deposit is located at the three-phase boundary) for the nitrate anion, which confirms that ClO₄⁻ easily enters nitrobenzene while NO₃⁻ does not. In the presence of chloride the situation was entirely different: the precipitation appeared on the part of microelectrode present in the aqueous phase. This proves that the electrooxidation of decamethylferrocene in the nitrobenzene drop leads rather to the transfer of the decamethylferrocenium cation to the aqueous phase and not to penetration of nitrobenzene by the chloride anion.     

Selective Adsorption of Phenol and Nitrobenzene by β‐Cyclodextrin‐Intercalated Layered Double Hydroxide: Equilibrium and Kinetic Study

The composite of carboxymethyl‐modified β‐cyclodextrin‐intercalated ZnAl‐layered double hydroxide (CMCD‐LDH) was investigated for selective adsorption of phenol (Ph) and nitrobenzene (NB). The Freundlich model can be used to describe satisfactorily the adsorption isotherms of Ph and NB. The adsorption capacity of CMCD‐LDH for Ph and NB increases with the increase of temperature, indicating the endothermic nature of this sorption process. CMCD‐LDH exhibits preferential adsorption for Ph over NB at pH 6.5 due to the selective recognition of the interlayer CMCD cavity. Pseudo‐first‐order and pseudo‐second‐order kinetic models were applied to simulate the kinetics of the adsorption process. The calculated q_e values based on the pseudo‐second‐order model are much closer to the experimental data q_e,exp. As a result, the pseudo‐second‐order kinetic model is more reasonable to describe the adsorption process of Ph and NB onto the CMCD‐LDH composite. CMCD‐LDH can be potentially applied in selective adsorption and separation of wastewater pollutants.