Influence of Nickel Salt Precursors on the Hydrogenation Activity of Ni/γ-Al2O3 Catalyst

Partially Reduced Ni-NiO-TiO2 Photocatalysts for Hydrogen Production from Methanol–Water Solution

The study compares the photocatalytic behavior of TiO2, NiO-TiO2, and Ni-NiO-TiO2 photocatalysts in photocatalytic hydrogen production from methanol–water solution. TiO2 and NiO-TiO2 photocatalysts with theoretical NiO loading of 0.5, 1.0, and 3.0 wt. % of NiO were prepared by the sol–gel method. The Ni-NiO-TiO2 photocatalysts were prepared by partial reduction of NiO-TiO2 in hydrogen at 450 °C. The Ni-NiO-TiO2 photocatalysts showed significantly higher hydrogen production than the NiO-TiO2 photocatalysts. The structural, textural, redox, and optical properties of all of the prepared photocatalysts were studied by using XRD, SEM, N2- adsorption, XPS, H2-TPR, and DRS. Attention is focused on the contribution of Ni loading, the surface composition (Ni2+, the lattice O2− species, and OH groups), the distribution of Ni species (dispersed NiO species, crystalline NiO phase, and the metallic Ni0 species), oxygen vacancies, TiO2 modification, the TiO2 crystallite size, and the specific surface area.

Co and Ni Incorporated γ-Al2O3 (110) Surface: A Density Functional Theory Study

Investigation into the state and mechanisms of the active metal substitution into the γ-Al2O3 support is the basis for design of many catalysts. Periodic density functional theory (DFT) +U calculations were used to investigate the surface properties of transition metals Co3+ and Ni3+ cations substitute for the Al3+ cations of γ-Al2O3 (110) surface. It was found that the substitution energy of one Al3+ substituted by Co3+ and Ni3+ are −61 and −57 kJ/mol, respectively. The Co and Ni preferentially substitute the tetrahedral Al sites instead of the octahedral Al sites. Using thermodynamics, the Al atoms in the top layer of γ-Al2O3 (110) can be 100% substituted by Co and Ni. Ni is easier to substitute the Al atom than Co. There is no obvious structural distortion that occurs after Co and Ni substituted all the top layer Al atoms. While the band gaps of the substituted surface become narrower, resulting in the increase of surface Lewis acidity. In addition, the oxygen vacancy formation energies of the Co and Ni substituted surface are 268 and 53 kJ/mol, respectively. The results provide interface structure and physical chemistry properties of metal-doped catalysts.

Competition between reactive adsorption desulfurization and olefin hydrogenation over the NiO/ZnO–Al2O3–SiO2 adsorbent

The RADS process inhibits olefin hydrogenation by competitive adsorption, which is affected by temperature and Ni loading.

Effect of the Nickel Source on the Structure, Performance, and Carbon Deposition of the Ni/Al2O3 Catalyst for CO2-CH4 Reforming

Ni/Al₂O₃ catalysts were prepared with Ni(NO₃)₂·6H₂O, NiSO₄·6H₂O, NiCl₂·6H₂O, and NiC₄H₆O₄·4H₂O as nickel sources by the solution combustion method. The catalysts were characterized by X-ray diffraction, H₂ temperature-programmed hydrogenation, TG-DTG, TPH, and transmission electron microscopy methods, and the effect of the nickel source on performance of the Ni/Al₂O₃ catalyst was investigated via the CO₂-CH₄ reforming experiment. Results showed that Ni dispersion, Ni size, and the metal-support interaction between active component Ni and the support were influenced significantly by anion in nickel sources, resulting in that the performance of each catalyst was different. Highly dispersed Ni species, small Ni crystallite size, and strong metal-support interaction were presented in the Ni/Al₂O₃ catalysts with Ni(NO₃)₂·6H₂O and NiSO₄·6H₂O as nickel sources. Evaluation results showed that the catalyst prepared with Ni(NO₃)₂·6H₂O exhibited higher activity and stability, with CH₄ and CO₂ conversions of 31.21 and 48.97%. Carbon deposition analysis demonstrated that the catalyst prepared with NiSO₄·6H₂O contained more graphite carbon.

Ruling Factors in Cinnamaldehyde Hydrogenation: Activity and Selectivity of Pt-Mo Catalysts

To obtain selective hydrogenation catalysts with low noble metal content, two carbon-supported Mo-Pt bimetallic catalysts have been synthesized from two different molybdenum precursors, i.e., Na₂MoO₄ and (NH₄)₆Mo₇O₂₄. The results obtained by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) combined with the presence and strength of acid sites clarified the different catalytic behavior toward cinnamaldehyde hydrogenation. After impregnating the carbon support with Mo precursors, each sample was used either as is or treated at 400 °C in N₂ flow, as support for Pt nanoparticles (NPs). The heating treatment before Pt deposition had a positive effect on the catalytic performance. Indeed, TEM analyses showed very homogeneously dispersed Pt NPs only when they were deposited on the heat-treated Mo/C supports, and XPS analyses revealed an increase in both the exposure and reduction of Pt, which was probably tuned by different MoO₃/MoO₂ ratios. Moreover, the different acid properties of the catalysts resulted in different selectivity.

CO2 utilization as a soft oxidant for the synthesis of styrene from ethylbenzene over Co3O4 supported on magnesium aluminate spinel: role of spinel activation temperature

Magnesium aluminate spinel (MgAl2O4) supported Co3O4 catalysts are synthesized and tested for the oxidative dehydrogenation (ODH) of ethylbenzene using CO2 as a soft oxidant. The effect of spinel calcination temperature on the catalytic performance has been systematically investigated. With an increase in the activation temperature from 600 to 900 °C, the active presence of a single-phase MgAl2O4 spinel is observed. A catalyst series consisting of MgAl2O4 spinel with varying Co loadings (10-20 wt%) were prepared and systematically distinguished by ICP, XRD, BET, TPR, NH3-TPD, UV-Vis DRS, FT-IR, XPS, SEM, and TEM. Among the tested cobalt catalysts, 15Co/800MA sample derived by calcination of MgAl2O4 support at 800 °C exhibits the most excellent catalytic performance with the maximum ethylbenzene conversion (≥ 82%). Also, high yields of styrene (≥ 81%) could be consistently achieved on the same active catalyst. Further, the catalyst exhibited almost stable activity during 20 h time-on-stream with a slow decrease in the ethylbenzene conversion from 82 to 59%. However, the selectivity of styrene (98%) stayed almost constant during the reaction. Activation of the MgAl2O4 spinel at 800 °C facilitates a dramatic chemical homogeneity for the alignment of Co3O4 nanoparticles on the surface of the active catalyst. Moreover, the isolated Co3O4 clusters have a strong chemical/electronic interaction with the Mg2+ and Al3+ ions on the support perform a crucial role to achieve the maximum catalytic activity.

Ultra-low loading of Ni in catalysts supported on mesoporous SiO2 and their performance in hydrodeoxygenation of palmitic acid

Ni catalysts supported on KIT-5 are attractive heterogeneous catalysts for hydrodeoxygenation of biomass feedstocks.

A practical approach for ambient-pressure hydrogenations using Pd on porous glass

A Pd on porous glass catalyst system was used in the liquid-phase hydrogenation of terpenoid substrates with dihydrogen at room temperature and atmospheric pressure. A multitude of substances were hydrogenated selectively with yields of 90-100 %. In all experiments, only C--C, C--N, and N--N double bonds were hydrogenated. Studies revealed that carbonyl and aromatic double bonds are inert towards catalytic reduction with dihydrogen under the conditions employed. In some cases, hydrogenation was accompanied by isomerization, so that treatment of beta-pinene, for example, afforded isomeric alpha-pinene, which was subsequently hydrogenated to pinane.