| Photocatalytic oxidation desulfurization, as a new type of oxidation desulfurization technology, has intrigued widely attention, because of its low energy consumption and pollution-free characteristics. In numerous photocatalysts, as a kind of efficient deep desulfurization catalyst, metal phthalocyanine sensitized semiconductor materials have become the research hot spot. In this article, on the basis of related research in domestic and overseas, two series of metal phthalocyanines were synthesized by the improved solid phase and liquid phase methods respectively, and then loaded them on the surface of perovskite composite oxides by impregnation method to prepare the new photocatalysts. Photocatalysts were used to oxidate dibenzothiophene in the model fuel. The relationship between the structure and catalytic activity was discussesed, and the reaction mechanism was also suggested, which provides beneficial references and enlightenment to the research of phthalocyanine sensitized semiconductor catalyst.The main comments were summarized as follows:1. Metal oxides LaNiO3and La1-xCexNiO3(x=0.1,0.2,0.1,0.2,0.8) were synthesized by sol-gel method, and charactered by the X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectrometer (XPS). Photocatalytic oxidation desulfurization tests were carried out under the irradiation of simulated sunlight, in which the solution of dibenzothiophene in octane was selected as the model diesel. The favorable burning temperature was selected by studying the influence of different calcination temperature on the oxide desulfurization activity. Compared with blank experiment, Lao.8Ceo.2Ni03was selected as the best catalyst supportor.2. Metal phthalocyanines MPc, MTAP, MPTpz, MTNPc, MTAPc and MTcPc (M=Mn(II), Fe(II), Co(II), Ni(II), Cu(II)) were synthesized by microwave-solid phase and liquid phase methods respectively, and charactered by Element analysis (EA), Infrared spectrum (IR) and Ultraviolet visible spectroscopy (UV-vis). Six series of metal phthalocyanine/La0.8Ce0.2NiO3catalysts were prepared by immersion method. XRD results show that they exist in amorphous form. According to the results of SEM, it can be concluded that the number of holes on composite metal oxides after loaded decreased significantly. Furthermore, the composition and elements valence of catalysts were determined by XPS technology. By comparing the spectra of the pure oxide and loaded oxide, it can be determined that new chemical bond were built.3. The main factors of the activity on the photocatalytic oxidation reaction were studied, and the best conditions can be concluded as follows:the amount of catalyst is3g·L-1and the ratio of hydrogen peroxide and sulphur is100:1. Under the best reaction condation, the catalytic activity of three series of metal phthalocyanines was discussed, it was demonstrated that center metal ion and N atom all infllence the activity. Among them, CoTcPc/Lao.8Ceo.2Ni03catalyst has the best photocatalytic activity, the desulfurization rate of which can reach94.9%under simulated sunlight for5h. The sulfur content remained in model diesel is49ppm, which can meet the national IV standard of desel. Finally, the reaction products were predicted through different tests, which may include CO2, SO42-, DBTO and DBTO2.4. On the basis of photocatalytic reaction, the effect of center metal ions and the substituent on photocatalytic activity was studyed. The results show that the center ion effect on catalyst activity is associated with valence electron configuration of metal ion. The metal phthalocyanines with varied valence (Fe+, Co+), have higher catalytic activity. Substituent effect on the activity of catalyst is mainly related to the nature of the substituents, electron-withdrawing groups (carboxyl, nitro) make the activity improved, and electron-donating group (amino) makes the catalyst activity decreased. In addation, the dynamics and reaction mechanism of the six series of loaded metal phthalocyanine catalysts were studied. The results showed that the reactions follow pseudo-first-order reaction kinetics equation, and CoTNPc/La0.8Ce0.2NiO3is the best photocatalyst with the half-life of74min. The catalytic reaction may be carried out in accordance with the three different paths at the same time:the mechanism of type I and type II and the mechanism of semiconductor photocatalytic reaction.5. Taking CoTcPc/La0.8Ce0.2NiO3as catalyst, the desulfurization rate of different sulfur compounds was studied. The catalytic activity order is as follows:dibenzothiophene> benzothiophene> thiophene. In addition, the stability of catalyst was also discussed. The results show that photocatalyst does not changed after five times recycles, and after ten times recycles, the catalytic activity decreases, but still maintains a certain catalytic activity, it can be concluded that the catalyst has good stability. |
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