The Catalytic Performance of Ni-Co/Beta Zeolite Catalysts in Fischer-Tropsch Synthesis

Selective Oxidation of Cyclohexene over the Mesoporous H-Beta Zeolite on Copper/Nickel Bimetal Catalyst in Continuous Reactor

The copper/nickel-metal on commercial H-Beta zeolite supports was synthesized with different wt % (Ni) of 5, 10, 15, and 20, and was used in the cyclohexene epoxidation process. The synthesized catalyst has been used in a continuous reactor for the cyclohexene epoxidation process, with mild conditions and H2O2 as an oxidant. The catalytic performance was ascertained by adjusting parameters such as the temperature, pressure, WHSV, reaction time, and solvents. The catalytic performance showed the resulting yield in both cyclohexene conversion and selectivity was more than 98.5%. The catalyst's textural attributes, morphology, chemical composition, and stability were determined using FT-IR, XRD, BET, HR-SEM, and TPD. The most active catalyst among those that were synthesized was evaluated, and the reaction parameters were selected to optimize yield and conversion. The H-Beta/Cu/Ni (15%) catalyst has the best conversion (98.5%) and selectivity (100%) for cyclohexene among the catalysts examined. Cu and Ni(15%) metals were successfully added to the H-Beta zeolite, causing little damage to the crystalline structure and resulting in good reusability over five cycles, as well as little loss of catalytic selectivity. Acetonitrile was the solvent that provided the highest conversion and selectivity among the others. These findings show that H-Beta/Cu/Ni bimetallic catalysts have the potential to be effective epoxidation catalysts. Because of their outstanding conversion and selectivity, the continuous reaction technique used in this work makes them appropriate for industrial production-level applications.

The Role of Nickel and Brønsted Sites on Ethylene Oligomerization with Ni-H-Beta Catalysts

The present work studies the adsorption of ethylene on Ni-H-Beta particles to unravel the roles of nickel and Brønsted sites in the catalytic oligomerization of ethylene. Three models (i.e., two based on the Cossee–Arlman mechanism and one based on the metallacycle mechanism) are examined in terms of the nature of the active sites and the adsorption mechanism involved in the ethylene coordination step. The results are consistent with the participation of two active sites in the formation of [Ni(II)-H]+ Cossee–Arlman centers and also suggest that ethylene dissociates upon adsorption on [Ni(II)-H]+ sites. Further characterization of Ni-H-Beta catalysts prepared at different nickel loadings and silica-to-alumina ratios reveals that highly dispersed Ni2+ exists on the catalyst surface and interacts with the catalyst’s lattice oxygen and free NiO crystals. At the same time, the kinetic results indicate that Brønsted sites may form isolated nickel-hydride ([Ni(II)-H]+) centers on the catalyst surface. In addition, the presence of residual, noncoordinated Ni2+ and Brønsted sites (not involved in the formation of [Ni(II)-H]+ sites) shows a reduced probability of the formation of nickel-hydride sites, hindering the conversion rate of ethylene. A mechanism for forming [Ni(II)-H]+ centers is proposed, involving ethylene adsorption over Ni2+ and a Brønsted site. This research has important implications for improving ethylene oligomerization processes over nickel-based heterogeneous catalysts.

Special Issue “Selected Papers from the 5nd Edition of Global Conference on Catalysis, Chemical Engineering and Technology (CAT 2019)”

The present Special Issue concerns the papers which have been presented at the fifth edition of the Global Conference on Catalysis, Chemical Engineering & Technology (CAT 2019) that promote linkage of the catalytic science, engineering and technology [...]