Jianying Lin

Ni/SBA-15 catalysts for CO methanation: effects of V, Ce, and Zr promoters

Ni/SBA-15 catalysts with various promoters (V, Ce, and Zr) were prepared by an ultrasonic coimpregnation method and used in CO methanation. The addition of promoters played a significant role in improving the catalytic activity of the Ni/SBA-15 catalyst. This improvement could be explained by changes in the valences of the V and Ce promoter species through an oxidation–reduction shift cycle process (Mx+ ↔ My+, M = V, Ce), which could trigger electron transfer. This transfer enhanced the electron density of active Ni species and promoted CO dissociation. The Zr promoter could produce oxygen vacancies during calcination and reduction, thereby increasing the ability of CO to adsorb and dissociate. In addition, the formation of a Si–O–M bond (M = Zr, Ce, V) increased the interaction between the active species and support, which facilitated CO methanation. Under 1.0 MPa and a WHSV of 15 000 mL g−1 h−1, 10Ni–5V/SBA-15 exhibited the best catalytic performance (99.9% CO conversion; 95.5% CH4 selectivity).

Influence of Microwave Irradiation on the Structural Properties of Carbon‐Supported Hollow Copper Nanoparticles and Their Effect on the Synthesis of Dimethyl Carbonate

Novel activated carbon (AC)‐supported highly dispersed hollow Cu nanoparticles (NPs) (Cu/AC) with exposed {1 1 1} facets have been prepared by microwave irradiation for the synthesis of dimethyl carbonate (DMC). In particular, Cu NPs with a large cavity diameter of 35 nm are formed after irradiation from room temperature to 360 °C within a mere 8 min without additional irradiation, thus benefiting from the rapid heating of the microwave procedure. In this study, an Ostwald ripening mechanism is proposed. DFT calculations are consistent with the analysis of CO temperature‐programmed desorption, which found that Cu(1 1 1) facets are more favorable for the weak adsorption of CO, which supports the formation of DMC. The as‐prepared catalysts exhibit the highest DMC formation rate in terms of turnover frequency and 100 % selectivity for DMC can be achieved. The large surface area of the hollow Cu NPs and the exposed {1 1 1} crystal planes are highlighted as being responsible for the excellent catalytic rate and superior selectivity, respectively.

The growth of Nin clusters and their interaction with cubic, monoclinic, and tetragonal ZrO2 surfaces–a theoretical and experimental study

Ni/ZrO2 catalysts are widely used in many reactions such as CO/CO2 methanation and reforming of acetic acid. The kind of ZrO2 phase plays a vital role in the catalytic properties of Ni/ZrO2 catalysts that depend on the interface between zirconia and supported Ni particles. Periodic density functional theory was applied to systematically investigate the interaction of a single Ni atom and Nin (n = 2–4) clusters with cubic ZrO2 (c-ZrO2) (111), monoclinic ZrO2 (m-ZrO2) (−111), and tetragonal ZrO2 (t-ZrO2) (101) surfaces. Adsorption of the Ni atom and all Nin (n = 2–4) clusters on zirconium dioxide surfaces was kinetically and thermodynamically preferred. Adsorption of Nin clusters on the m-ZrO2(−111) surface is more stable than that on the t-ZrO2(101) surface, and the t-ZrO2(101) surface is more stable than the c-ZrO2(111) surface. The aggregation ability of Nin clusters on different ZrO2 surfaces and the isolated clusters follow the trend m-ZrO2(−111) < t-ZrO2(101) < c-ZrO2(111) < isolated cluster. Therefore, Nin clusters can have a better dispersion and can inhibit aggregation due to the support. What is more, the single-phase ZrO2 was synthesized and loaded with an equivalent content of active Ni components. The experimental results obtained by X-ray photoelectron spectroscopy analysis support the hypothesis that has been deduced.