Weihan Wang

Ni-based catalyst derived from Ni/Al hydrotalcite-like compounds by the urea hydrolysis method for CO methanation

The catalytic methanation of CO was investigated at atmospheric pressure over Ni-based catalysts derived from Ni/Al hydrotalcite-like compounds. The catalysts were prepared by the urea hydrolysis method and characterized by using XRD, TGA, N2 adsorption–desorption, H2-TPR, H2-TPD and TEM. The H2-TPD analysis revealed an increase in the Ni surface area, from 14.9 to 21.8 m2 g−1, as the Ni/Al molar ratio was increased from 0.5 to 2, and a nearly constant Ni surface area, of about 22.3 m2 g−1, at Ni/Al molar ratios > 2. A similar dependence on Ni/Al molar ratio was also found for CO conversion. The NA1 (Ni/Al molar ratio to 1) catalyst exhibited excellent stability at 600 °C for 1800 min on the stream. The NA1 catalyst prepared from Ni/Al hydrotalcite-like compounds exhibited higher catalytic stability due to higher Ni dispersion and stronger resistance to coke deposition than did the impregnated NA1-I catalyst.

Ni-based catalyst derived from Ni/Mg/Al hydrotalcite-like compounds and its activity in the methanation of carbon monoxide

The supported Ni-based catalyst is widely used in the methanation process. Nevertheless, the major disadvantages of this catalyst are a poor behavior in the water-gas-shift (WGS) reaction and the deactivation at higher temperatures. A new kind of catalyst, nickel-containing oxides catalyst (NiMgAl), obtained from thermal treatment of hydrotalcite-like compounds (HTlcs) was prepared using the co-precipitation method. The performance of this catalyst was systematically investigated and compared with that of the Ni/Al2O3 catalyst. It was found that the NiMgAl catalyst shows an enhanced methanation activity compared to that of the Ni/Al2O3 catalyst and the former catalyst shows a better performance for the methanation especially at temperature over 550°C. Three NiMgAl catalysts with different nickel content were prepared and tested in the methanation operated at a GHSV of 15000 h−1 and n(H2)/n(CO) of 1.5. The results indicate that with the NiMg8 catalyst a higher activity and stability could be achieved than with the NiMg5 and NiMg6 samples, the effect mainly attributed to a higher extent of Ni dispersion was confirmed by XRD results.

Mesoporous and Macroporous Alumina-Supported Nickel Adsorbents for Adsorptive Desulphurization of Commercial Diesel

High-performance X%NiOx/Al2O3 adsorbents were prepared using mesoporous and macroporous alumina for adsorptive desulphurization (ADS) of commercial diesel (total sulphur content, 150 ppmw) at atmospheric pressure. Among the synthesized adsorbents, the reduced mesoporous and macroporous 20%NiOx/Al2O3 (Re20%NiOx/Al2O3) presented the breakthrough capacity of 1.47 mg-S/g-sorbent with sulphur level of 10 ppmw. The ultra-deep desulphurization properties for two adsorbents were evaluated using simulated fuels. The adsorbent with macropores showed a superior desulphurization performance, and the existence of macropores remarkably increased its breakthrough capacity as well as improved the space steric hindrance effect. The adsorbents synthesized were characterized by nitrogen adsorption isotherms (BET), X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, temperature-programmed reduction of hydrogen, temperature-programmed desorption of ammonia and Fourier transform infrared techniques. The results showed that the synthesized adsorbents were stable, contained acid sites, especially Lewis acid sites, which played an important role in ADS. Even after three cycles of regeneration, the organic sulphur-adsorption capacity of Re20%NiOx/Al2O3 was more than 80%.

Effect of alkyl nitrite decomposition on catalytic performance of CO coupling reaction over supported palladium catalyst

The syntheses of dimethyl oxalate (DMO) and diethyl oxalate (DEO) by CO coupling reaction in gaseous phase were investigated in a fixed bed reactor over Pd-Fe/Al2O3 catalyst. The catalytic performance was characterized by CO conversion, space-time yield (STY) and selectivity of DMO (or DEO). The results showed that over Pd-Fe/Al2O3 catalyst, the STY of DMO was higher than that of DEO under the same reaction conditions. The optimum reaction temperatures for synthesizing DMO and DEO were 403 K and 393 K, respectively, at the molar ratio 1:1 of alkyl nitrite to CO. The difference in synthesizing DMO and DEO on the same catalyst was attributed to the decomposition performances of methyl nitrite (MN) and ethyl nitrite (EN), as density functional theory (DFT) calculation showed that EN decomposed more easily than MN.

Sulfur-Resistant CO Methanation to CH 4 Over MoS 2 /ZrO 2 Catalysts: Support Size Effect On Morphology and Performance of Mo Species

In this work, the effect of ZrO2 particle size on the surficial and structural properties and catalytic performance of Mo-based catalysts towards sulfur-resistant methanation was investigated. The results showed that the catalytic activity correlated closely with the particle size of ZrO2. The supports and catalysts were characterized by N2-adsorption, XRD, Raman, H2-TPR and TEM to obtain the information about their morphology and structure in order to understand the structure–activity relationship. The results evidence that smaller ZrO2 particle not only had higher surface area which was beneficial for the dispersion of surface Mo species, but also weaken the interaction between MoO3 and support. Since them, ZrO2 support with small particle size favors the formation of monolayer MoS2 with short length. Catalytic activity evaluation determined that MoS2/ZrO2 catalyst with smaller ZrO2 particle size exhibited higher catalytic activity of sulfur-resistant CO methanation due to more edge sites on MoS2.Graphical Abstract