Preparation of Ni/bentonite catalyst and its applications in the catalytic hydrogenation of nitrobenzene to aniline

Ni supported on bentonite was prepared by the impregnation method with different nickel contents, applied to the hydrogenation of nitrobenzene to aniline in a fixed-bed reactor, and it was characterized by X-ray diffraction(XRD), H_2-temperature programmed reduction(H_2-TPR), and X-ray photoelectron spectrometry(XPS). The results showed that Ni/bentonite catalyst with 20 wt% nickel content provided a higher conversion of nitrobenzene and selectivity of aniline compared to other catalysts. Ni O was the precursor of the active component of the catalyst, and the small crystallite size as well as the highly dispersed Ni O on the Ni/bentonite-20 catalyst, contributed to the catalytic performance. The hydrogenation of nitrobenzene was carried out at 300 °C with a H_2 gaseous hourly space velocity of 4800 ml·(g cat)^(-1)·h^(-1)and a nitrobenzene liquid hourly space velocity of4.8 ml·(g cat)^(-1)·h^(-1)over Ni/bentonite-20. A 95.7% nitrobenzene conversion and 98.8% aniline selectivity were obtained. While the nitrobenzene liquid hourly space velocity was 4.8 ml·(g cat)^(-1)·h^(-1), the yield of aniline was more than 95.0% during a 10-hour reaction.

Ni/bentonite catalysts prepared by solution combustion method for CO_2 methanation

A 20 wt% Ni/bentonite catalyst was prepared by a solution combustion synthesis (SCS), which exhibited higher activity for the CO_2methanation than that of an impregnation method (IPM), and the catalyst prepared by SCS showed a CO_2 conversion of 85% and a CH4selectivity of 100% at 300 °C, atmospheric pressure, and 3600 ml·(g cat)-1·h-1, and the catalyst exhibited stable within a 110-h reaction. The results showed higher me- tallic Ni dispersion, smaller Ni particle size, larger specific surface area and lower reduction temperature in the Ni/ bentonite prepared by SCS than that of IPM. And the Ni/bentonite prepared by the SCS moderated the interaction between NiO and bentonite.

Influence of Zr, Ce, and La on Co_3O_4 catalyst for CO_2 methanation at low temperature

The Co_3O_4 and Zr-,Ce-,and La-Co_3O_4 catalysts were prepared,characterized,and applied to produce CH_4 from CO_2 catalytic hydrogenation in low temperature as 140–220°C.The results indicated that the addition of Zr,Ce,or La to the Co_3O_4 decreased the crystallite sizes of Co and the outer-shell electron density of Co^(3+),and increased the specific surface area,which would provide more active sites for the CO_2 methanation.Especially,the addition of Zr also changed the reducing state of Co_3O_4 via an obvious change in the interaction between Co_3O_4 and ZrO_2.Furthermore,Zr doped into the Co_3O_4 increased the basic intensity of the weak and medium basic sites,as well as the amount of Lewis acid sites,and Br?nsted acid sites were also found on the Zr-Co_3O_4 surface.The introduction of Zr,Ce,or La favored the production of CH_4,and the Zr-Co_3O_4catalyst exhibited the highest CO_2 conversion(58.2%)and CH_4 selectivity(100%)at 200°C,and 0.5 MPa with a gaseous hourly space velocity of 18,000 ml·g^(-1)_(cat)·h^(-1),and the catalytic activity of CO_2methanation for the Zr-,Ce-,and La-Co_3O_4 exhibited more stable than Co_3O_4 in a 20-h reaction.