Kuiyi You

H3PW12O40 synergized with MCM-41 for the catalytic nitration of benzene with NO2 to nitrobenzene

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.

Palladium Supported Catalysts for Nitrocyclohexane Hydrogenation to Cyclohexanone Oxime with High Selectivity

Different kinds of activated carbon‐ and carbon nanotube‐supported palladium catalysts were investigated in the selective hydrogenation of nitrocyclohexane to cyclohexanone oxime under mild conditions. Carbon nanotube‐supported palladium catalysts demonstrate better catalytic performance than activated carbon‐supported palladium catalysts in general because of their mesoporous structures, which are favorable supports for the accessibility of the reactants to the active sites and the product desorption from the catalyst. Hydrogen chemisorption, transmission electron microscopy and X‐ray photoelectron spectroscopy indicate that higher composition of Pd+ on the catalyst surface, larger palladium surface area, and better palladium dispersion contribute to an increase in the activity and selectivity toward cyclohexanone oxime. In addition, single‐wall carbon nanotube‐supported palladium catalysts give the best result of 97.7 % conversion of nitrocyclohexane and 97.4 % selectivity toward cyclohexanone oxime. On the basis of the results of GC–MS and the designed experiments, a possible reaction scheme was proposed.

One-Step Cyclohexane Nitrosation to ε-Caprolactam over Metal Substituted AlPO-5

Abstract Crystalline AlPO-5, SAPO-5, and metal substituted AlPO-5 (MeAlPOs) were prepared by the hydrothermal method and characterized by X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy, particle size distribution, inductively coupled plasma (ICP) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, NH3 temperature-programmed desorption (TPD), H2 temperature-programmed reduction, and thermogravimetric-differential thermogravimetric (TG-DTG) analysis. All the samples crystallized with the AFI structure. TPD profiles showed that stronger Bronsted acid sites appeared and the number of Lewis acid sites increased when Si or a metal was introduced into the framework of AlPO-5. ICP, FT-IR spectra, and TG-DTG curves confirmed that Si or the metals were incorporated into the framework of the AlPO-5. The catalytic properties of the samples in cyclohexane nitrosation to e-caprolactam were studied. SAPO-5 with a larger BET surface area, more Lewis acid sites, and stronger Bronsted acid sites gave better activity and selectivity than AlPO-5. Among the MeAlPOs, CrAPO-5 with the larger BET surface area, more Lewis acid sites, and stronger Bronsted acid sites gave the better result with a conversion of 8.16% and e-caprolactam selectivity of 68.17%.

Hydrophilicity Modification of MCM-41 With Zirconia and Supported Ruthenium-Lanthanum for Benzene Hydrogenation to Cyclohexene

Zirconia modified mesoporous molecular sieve MCM-41 supports were prepared by hydrothermal synthesis method, in situ synthesis method and precipitation method. Ruthenium and lanthanum supported on MCM-41 and zirconia modified MCM-41 catalysts were prepared via two solvents impregnation method. The catalysts were characterized by X-ray diffraction, transmission electron microscopy, nitrogen adsorption-desorption, and water/benzene static adsorptions techniques. It has been found that Ru-La supported on MCM-41 modified with zirconia by hydrothermal synthesis method (Ru-La/ZrO2-MCM-41-HS) leads to the biggest increase of the hydrophilicity. Ru-La/ZrO2-MCM-41-HS catalyst with the highest hydrophilicity shows the best performance in liquid phase hydrogenation of benzene to cyclohexene.

Nitrocyclohexane hydrogenation to ε-caprolactam over Pd/C and 2,4,6-trichloro-[1,3,5]-triazine in N,N-dimethylformamide

A new composite catalytic system of Pd/C, 2,4,6-trichloro-[1,3,5]-triazine and N,N-dimethylformamide was investigated in nitrocyclohexane hydrogenation to ε-caprolactam. The Pd/C catalyst was prepared by the incipient impregnation method and characterized by BET, N2 adsorption–desorption, XRD, TEM and H2 chemisorption. The results indicate that 2,4,6-trichloro-[1,3,5]-triazine plays a key role in one step synthesis of ε-caprolactam from nitrocyclohexane hydrogenation. Besides ε-caprolactam, the products include cyclohexanone oxime, cyclohexamine, cyclohexanone and cyclohexanol. A possible mechanism for nitrocyclohexane hydrogenation in 2,4,6-trichloro-[1,3,5]-triazine and N,N-dimethylformamide complex was proposed.

Sulfated SO42−/WO3 as an efficient and eco-friendly catalyst for solvent-free liquid phase nitration of toluene with NO2

With the increase in environmental awareness, developing a highly efficient and environmentally benign nitration process has very important academic and applied industrial values in the synthesis of nitro-compounds. Towards this goal, we have developed an efficient and environmentally friendly approach for solvent-free liquid phase nitration of toluene by employing NO2 as a nitrating agent and sulfated SO42−/WO3 as a catalyst replacing traditional nitric acid–sulfuric acid under mild conditions. The results indicate that SO42−/WO3 as an effective and eco-friendly catalyst exhibits excellent catalytic activity and reusability for the nitration of toluene with NO2. In addition, the possible pathway for liquid phase nitration of toluene with NO2 over sulfated SO42−/WO3 catalyst was suggested. The present method makes this nitration process safe and environmentally friendly, and has the potential to enable a sustainable production of nitro-compounds from the liquid phase nitration of aromatic hydrocarbon with NO2 in industrial applications.

Metal salts with highly electronegative cations as efficient catalysts for the liquid-phase nitration of benzene by NO 2 to nitrobenzene

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.

Influence of preparation conditions on the structure of MCM-41 and catalytic performance of Ru/MCM-41 in benzene hydrogenation

The influence of the preparation conditions on the structures of mesoporous molecular sieve MCM-41 were studied. The prepared MCM-41 samples were characterised by nitrogen physical adsorption–desorption, powder X-ray diffraction, transmission electron microscopy, FT-IR spectroscopy, thermo gravimetric analysis, differential scanning calorimetry and water/benzene static adsorption technologies. Ru/MCM-41 catalysts were then prepared by double solvent impregnation method and tested for benzene hydrogenation to cyclohexene. The structure characteristics of MCM-41 have a great effect on cyclohexene selectivity in benzene hydrogenation process. Ruthenium supported on MCM-41 with moderate surface area, larger pore size and pore volume, better long-range-order of hexagonal mesoporous shows better catalytic performance for benzene hydrogenation to cyclohexene.

One-step synthesis of ɛ-caprolactam via the liquid phase catalytic nitrosation of cyclohexane in the presence of concentrated sulfuric acid

A simple and efficient approach for the synthesis of ɛ-caprolactam via the liquid phase nitrosation of cyclohexane and nitrosyl sulfuric acid in the presence of concentrated sulfuric acid has been developed. A series of novel AlVPO composites were prepared by an impregnation method and the composites were then employed to catalyze the nitrosation reaction of cyclohexane and nitrosyl sulfuric acid. Compared to the reaction using fuming sulfuric acid, the selectivity for the desired product was significantly improved using this one-step catalytic process. This method affords a shortcut to prepare ɛ-caprolactam and its analogs from cyclohexane.