Metal salts with highly electronegative cations have been used to effectively catalyze the liquid-phase nitration of benzene by NO2 to nitrobenzene under solvent-free conditions. Several salts including FeCl3, ZrCl4, AlCl3, CuCl2, NiCl2, ZnCl2, MnCl2, Fe(NO3)3∙9H2O, Bi (NO3)3∙5H2O, Zr(NO3)4∙5H2O, Cu(NO3)2∙6H2O, Ni (NO3)2∙6H2O, Zn(NO3)2∙6H2O, Fe2(SO4)3, and CuSO4 were examined and anhydrous FeCl3 exhibited the best catalytic performance under the optimal reaction conditions. The benzene conversion and selectivity to nitrobenzene were both over 99%. In addition, it was determined that the metal counterion and the presence of water hydrates in the salt affects the catalytic activity. This method is simple and efficient and may have potential industrial application prospects.

We demonstrate VPO composites as efficient catalysts for highly selective oxidation of cyclohexane to adipic acid with NO2. In particular, the Ni–Al–VPO composite catalyst exhibits the striking conversion of cyclohexane (60.6%) and exceptionally high selectivity towards adipic acid (85.0%). Moreover, N2O is an environmentally harmful gas, and its yield in the present process is only 0.03 t/t adipic acid, which is far below that obtained using the industrial method (0.3 t/t adipic acid). This work provides a new strategy for the one-step synthesis of dicarboxylic acids from cycloalkanes.

Developing an economic and efficient approach for the production of adipic acid is a grand challenge in the chemical industry. Toward this goal, we report a simple method for selective synthesis of adipic acid from cyclohexane with NO2 by using Ni–Al–VPO/MCM-41 as catalyst. The physical-chemical properties of supported Ni–Al–VPO/MCM-4 catalysts were characterized, the reaction conditions were optimized, and the reusability of the catalyst was examined. The results showed that the supported 30%Ni–Al–VPO/MCM-41 catalyst exhibited excellent catalytic performance with 65.1% of cyclohexane conversion and 85.3% of selectivity toward adipic acid, especially, its catalytic performance was still stable after five runs. Maybe this developed method has potential industrial application prospects for production of adipic acid.

Developing a new environmentally friendly process for benzene nitration to nitrobenzene has been highly desirable for a long time. In this work, NO2 was used as a nitration agent to replace traditional nitric acid, and different mesoporous SiO2 and their supported heteropoly acid (salt) were employed to catalyze benzene nitration to nitrobenzene. Several typical catalysts were characterized using XRD, BET and FT-IR, and the acid amounts of the various catalysts were determined. The effects of various factors such as different catalysts, the molar ratio of benzene to NO2, reaction temperature, reaction time, HPW loading, the acid amounts of the catalyst and the reuse of the catalyst on the nitration reaction have also been systematically examined. The results indicate that the supported HPW/MCM-41 catalysts exhibit a remarkably synergistic catalytic performance on the nitration reaction of benzene to nitrobenzene. In particular, the 50%HPW/MCM-41 catalyst gives the best results with 73.4% benzene conversion and 98.8% selectivity to nitrobenzene under the optimal reaction conditions. Moreover, the mesoporous structure of MCM-41 was retained under the high loading of HPW. The possible reaction mechanism for the nitration reaction of benzene with NO2 over HPW/MCM-41 is suggested in the present work. This method provides a promising strategy for the preparation of nitro-aromatic compounds from a catalytic nitration reaction by using NO2 as the nitration reagent.

The nitrozation reaction of cyclohexane in one-step reaction to form ɛ-caprolactam has been studied using transition metal salt as catalysts in this work. The results indicated that the catalysts play an especially important role. This method is expected to be a novel way to synthesize other lactam by similar reaction. The possible mechanism was suggested.

N, N’-bis (salicylidene) ethylenediiminocobalt (Cosalen) was encapsulated into microporous NaY zeolite via the technique of “ship-in-bottle”. The encapsulated complex (Cosalen-NaY) was characterized by Fourier-transform infrared spectrum, ultraviolet-visible spectrum, Brunauer-Emmett-Teller surface areas, X-ray diffraction, thermogravimetry-differential thermal analysis and scanning electron microscope. The reaction of cyclohexane oxidation using oxygen was chosen to investigate the catalytic performance of Cosalen-NaY, and the effects of oxygen pressure, temperature and reaction time were also studied. The results show that Cosalen complex is encapsulated into the supercage of the zeolite and the structure of NaY zeolite remains integrity and the thermal stability of Cosalen is greatly enhanced after encapsulation. Cosalen-NaY shows the better activity in the oxidation of cyclohexane without reductant and solvent. The conversion of cyclohexane is up to 13.4% at 150 °C for 3 h under oxygen pressure of 0.85 MPa, with the higher total selectivity to cyclohexanol, cyclohexanone, cyclohexyl hydroperoxide (CHHP) and acid (79.2%) than the neat complex (55.5%). NaY zeolite carrier maybe contributes to the results. There is no obvious induction period to initiate the reaction; furthermore, the amount of CHHP among the products is small, which indicates that the Cosalen-NaY has the strong ability to accelerate the decomposition of CHHP. Recycling tests show that the hybrid material can be used repeatedly with a negligible loss of active sites.

•FeCl3 can be firmly immobilized on SiO2 by bonding of FeCl3 and silicon hydroxyl groups (SiOH).•The immobilized catalyst shows remarkable catalytic performance for benzene nitration.•FeCl3-SiO2 catalyst is proven to be stable and recyclable in the nitration reaction.•The present catalyst can be conveniently separated from the reaction media.•The developed method is environmentally friendly in manufacture of nitro aromatics.Mesoporous silica-immobilized FeCl3 (FeCl3-SiO2) as a highly efficient and reusable catalyst for the nitration of benzene with NO2 has been successfully prepared in this work. The physical-chemical properties of samples were characterized by BET, XRD, TG-DTG, NH3-TPD, FT-IR, UV–vis DRS, Raman spectra and SEM. The characterization results indicated that FeCl3 could be immobilized on the silica surface by bonding of FeCl3 and silicon hydroxyl groups (SiOH) in forming the new Lewis acid sites of SiOFeCl2. The results showed the immobilized 15%FeCl3-SiO2 catalyst exhibited excellent catalytic performance (99% of benzene conversion with 99% of selectivity to nitrobenzene) under the optimized reaction conditions. Furthermore, the durability of catalyst was remarkably improved by immobilizing. The present immobilized FeCl3-SiO2 catalyst as a solid heterogeneous and stable catalyst could be conveniently recycled from the reaction media by filtering and remained highly catalytic performance even after five runs of recycling. The possible reaction pathway for the nitration of benzene with NO2 over FeCl3-SiO2 catalyst was suggested. This method provides a promising strategy for highly efficient preparation of nitro aromatic compounds by using NO2 as nitration reagent, with the potential industrial applications.Download full-size image

•The influence of energy spectrum on drop breakage was studied.•Drop breakage should be modeled in the wide energy spectrum range.•A breakage model in terms of general energy spectrum function was presented.•This model can explain the recent experimental phenomena theoretically.This work focused on the influence of energy spectrum distribution on drop breakage in turbulent flows. An improved breakage model in terms of general energy spectrum function was presented. It can be coupled with available forms of energy spectrum and can be applied to the wider operating conditions such as the wider size range of drops. Unlike previous work that only considered the inertia subrange spectrum, this work simulated the breakage in the framework of wide energy spectrum and accounted for the necessity of considering the wide energy spectrum distribution. The improved model coupled with wide energy spectrum function can theoretically explain the recent experimental phenomena observed by Maaß and Kraume, 2012. Determination of breakage rates using single drop experiments. Chem. Eng. Sci. 70, 146–164. That is, breakage frequency increases to a maximum and then decreases with increasing parent drop size. This is because the non-monotone energy spectrum function can distinguish three spectrum ranges, i.e., containing-energy range, inertia subrange and dissipation range, and the treatment that parent drop size always falls in the inertia subrange is no longer required in this work. While when only the energy spectrum of inertia subrange is applied to the whole size range of eddies, the predicted breakage frequency monotonously increases with parent drop diameter. Therefore, the energy spectrum distribution has a crucial influence on the evolution of the breakage frequency with parent drop size.As shown in this figure, the breakage frequency predicted by the proposed model coupled with energy spectrum function SMA or SMB increases to a maximum and then decreases with increasing parent drop diameter. Furthermore, SMA or SMB showed a non-monotone distribution with wave number. However, the breakage frequency predicted by the proposed model coupled with energy spectrum function SIS monotonously increases with parent droplet diameter and the energy spectrum always increases with decreasing wave number.Download high-res image (132KB)Download full-size image

We demonstrate VPO composites as efficient catalysts for highly selective oxidation of cyclohexane to adipic acid with NO2. In particular, the Ni–Al–VPO composite catalyst exhibits the striking conversion of cyclohexane (60.6%) and exceptionally high selectivity towards adipic acid (85.0%). Moreover, N2O is an environmentally harmful gas, and its yield in the present process is only 0.03 t/t adipic acid, which is far below that obtained using the industrial method (0.3 t/t adipic acid). This work provides a new strategy for the one-step synthesis of dicarboxylic acids from cycloalkanes.