No abstract

TiO2-modified oxygen-functionalized activated carbon (TiO2@OAC)-loaded nickel-based catalysts (Ni/TiO2@OAC) were synthesized and applied in the hydrogenation of chloronitrobenzene (CNB) to chloroanilines (CANs). The characterization results indicate that introduction of TiO2 restrains nickel nanoparticles sintering and improves the stability of the catalysts by strong metal–support interaction. Additionally, the X-ray photoelectron spectroscopy results suggest that the electron donating effect of Ti3+ produces electron-rich Ni (Niδ−), which inhibits C–Cl moiety adsorption. The formed Niδ− species might induce electron-rich hydrogen (H–) generation which facilitates a nucleophilic attack on −NO2 rather than an electrophilic attack on the C–Cl bond. Furthermore, the electron-donating ability of −NH2 could be reduced because of the interaction between −OH in TiO2@OAC and −NH2 in CAN. Hence, the dechlorination is inhibited and the selectivity to m-CAN is up to 99.0%. The catalytic performance of Ni/TiO2@OAC could be maintained after five cycles.

Activated carbon supported bimetallic Ni-based catalysts were prepared and applied in the selective hydrogenation of nitrocyclohexane (NCH) to cyclohexanone oxime (CHO). The characterization results show that the introduction of the metal promoter can inhibit Ni nanoparticle agglomeration and sintering. Among these bimetallic catalysts, the Cu-Ni/AC catalyst shows the best catalytic performance. The results indicate that introduction of a suitable amount of Cu can effectively promote Ni nanoparticle dispersion, decrease NiO reduction temperature, and facilitate metal Ni exposure. Density functional theory calculation results show that the CuNi (1 1 1) crystal surface possesses higher adsorption energies of H 2 and NCH, lower adsorption energies of the active hydrogen (H*) and CHO, and lower reaction energy barriers of NCH hydrogenation to CHO than the Ni (1 1 1) crystal surface. Under the optimized conditions, 1%Cu-20%Ni/AC gives 99.6% NCH conversion and 87.8% high selectivity to CHO. Low-cost bimetallic Cu-Ni catalysts present potential application in economical commercial production of CHO from NCH.

In this work, we report the electric-field effects on ionic hydration of Cl, Na, and Pb using molecular dynamics simulations. It is found that the effect of weak fields on ionic hydration can be neglected. Strong fields greatly disturb the water orientation in the hydration shells of ions, though ion coordination number remains almost unchanged. Under strong fields, the first hydration shell of ions is significantly weakened and the ion-water interaction energy is dramatically reduced; surprisingly, the second hydration shells of Cl and Na are slightly structured because of the optimal water orientation; moreover, ionic hydration structures become asymmetrical along the field direction because of the uniformly aligned water dipoles. Compared with Na and Pb, the hydration of Cl is less disturbed by external fields, probably ascribed to the different water reorientation around anions and cations as well as the different structure-maker/breaker nature of the ions. Additionally, strong fields significantly enhance ion mobility and remarkably shorten the water residence time in the hydration shell. This work demonstrates that applying strong fields is an effective way to weaken ion hydration.

No abstract