Corrigendum to Cobalt-β-diimine complexes for ethylene oligomerization

Three dendritic PNP ligands with ethylenediamine, 1,4‐butanediamine, 1,6‐diaminohexane as bridged groups are synthesized in good yields, respectively. Three dendritic PNP chromium complexes (C1 – C3) are prepared with the ligands and chromium(III) chloride tetrahydrofuran complex (CrCl3(THF)3) as materials. The dendritic PNP ligands and the synthetic chromium complexes are fully characterized by spectroscopic and analytical methods. All chromium complexes activated with methylaluminoxane (MAO) exhibited moderate activities on ethylene oligomerization (7.90 × 104 – 2.15 × 105 g (mol Cr h)−1] and had better selectivity for C6 and C8 oligomer, reaching up to 81%. The chromium complex (C1) activated with diethylaluminium chloride (Et2AlCl) has higher catalytic activity than the chromium complex C1 activated with MAO, although the chromium complex (C1) activated with Et2AlCl had lower selectivity for C6 and C8 oligomer. The effects of solvent and reaction parameters on ethylene oligomerization are also studied using the chromium complex C1 as pre‐catalyst and MAO as co‐catalyst. Under optimized conditions ([complex] = 2 μmol, Al/Cr = 500, 25 °C, 0.9 MPa ethylene, 30 min), the catalytic activity of complex C1 in toluene is 2.15 × 105 g (mol Cr h)−1 and the selectivity for C6 and C8 oligomer is 36.76%. In addition, the structure of complexes significantly affects both the catalytic activity and the selectivity on ethylene oligomerization.

Decarbonizing the chemicals industry requires net carbon negative technologies capable of displacing current greenhouse gas emitting processes. In particular, the generation of valuable monomers, such as butene, are currently produced by significant greenhouse gas emitting processes, including ethylene oligomerization and crude oil refining, which require high temperatures and pressures. Integrated, tandem solar fuels devices for the conversion of CO2 to ethylene, using solar-driven CO2 reduction (CO2R), combined with a photothermal reactor for ethylene oligomerization, offers a potential path to producing clean butene from CO2, using solar energy as the only driving force. A key challenge for the successful operation of a tandem photo-driven electrochemical-photothermal system is the co-design of the two processes, which are typically optimized under different operating conditions. Specifically, photo-driven electrochemical CO2R (pCO2R) reactors operate under ambient temperature and pressure conditions while thermally-driven ethylene oligomerization reactors prefer elevated temperatures (80-140 °C) and pressures (30-150 atm) to promote high activity as well as pure ethylene in the inlet stream. Operation of the tandem process under solar-driven conditions imposes additional constraints on the maximum power output of the pCO2R reactor and the maximum temperature which can be obtained in the photothermal reactor. Herein, we present an unassisted solar-driven tandem system coupling pCO2R with photothermal ethylene oligomerization for the conversion of CO2 to butene in a single pass. This work presents a critical advancement in the development of solar fuels technologies for larger hydrocarbon generation and identifies the co-design principles which must be considered for implementation of tandem, solar-driven electrochemical-thermal processes.

Catalytic ethylene oligomerization is important in the petrochemical industry, as it produces valuable products like linear alpha‐olefins (LAOs) for the synthesis of polymers and specialty chemicals. Catalysts, typically transition metal complexes or metal‐containing materials, play a crucial role in selective oligomerization by providing active sites for ethylene activation and controlling product distribution. Recently, defective metal‐organic frameworks (MOFs) with well‐defined structures and unsaturated active sites have emerged as potential catalysts for ethylene oligomerization. In this study, we employ density functional theory calculations to investigate the energetic selectivity of competing pathways (including dimerization, isomerization and trimerization) during ethylene oligomerization on defective HKUST‐1 supported metal hydrides (H−M–DHKUST‐1, M: Co, Ni, Ru, Rh and Pd). On all the five hydrides, ethylene dimerization is found to be more preferential than trimerization and isomerization. In the microenvironment of defective paddlewheel of HKUST‐1, isomerization is highly unfavorable compared with dimerization because of high energy required for chain walk, and 1‐butene is expected to be the major product on all the five hydrides. Analysis of NBO charges reveals a notable reduction in cationic nature at the metal site on H−Ru–DHKUST‐1, which facilitates β‐hydride elimination for dimerization. The microscopic insights from this computational study might facilitate the rational design of new MOFs and other MOF‐supported catalysts for selective ethylene oligomerization.

The functionalized dendrimers play an important role in catalytic application. A dendritic Schiff base macrocyclic compound was designed and synthesized with the 1.0 generation dendrimer polyamidoamine (1.0G PAMAM) and terephthalaldehyde for ethylene oligomerization. The role of solvent in the synthesized process of dendritic macrocyclic Schiff base ligand was studied. Surprisingly, intermolecular or intramolecular cyclization occurred and formed bicyclic Schiff base ligand ( Ligand 1 ) and polycyclic Schiff base ligand ( Ligand 2 ). And their corresponding nickel complexes ( Catalyst 1 and Catalyst 2 ) were also synthesized with NiCl 2 (DME) as material to be used for ethylene oligomerization. The effects of the reaction parameters and the chemical structure of the ligand on the catalytic behavior were investigated with methyl‐aluminoxane (MAO) as cocatalyst, and Catalyst 1 and Catalyst 2 displayed the high catalytic activity and the high selectivity for low‐carbon olefin in ethylene oligomerization. Catalyst 2 based on Ligand 2 had a higher catalytic activity of 9.12×10 4 g (mol Ni h) −1 in ethylene oligomerization because of large dendritic ring in the ligand for ethylene diffusion and mass transfer. Moreover, two synthesized nickel complexes based on dendritic macrocyclic Schiff base ligand had a higher catalytic activity compared with the corresponding dendritic salicylaldehydeimine nickel (II) catalyst.

Ethylene oligomerization on nickel catalysts on a solid acid support: From New mechanistic insights to tunable bifunctionality

Immobilization of bis(imino)pyridine iron complexes onto mesoporous molecular sieves and their catalytic performance in ethylene oligomerization

Ethene oligomerization on nickel microporous and mesoporous-supported catalysts: Investigation of the active sites

Nickel complexes based on hyperbranched salicylaldimine ligands: Synthesis, characterization, and catalytic properties for ethylene oligomerization

Highly dispersed and stable Schiff base nickel catalyst on multi-walled carbon nanotubes promote ethylene oligomerization

The effect of the nature of a chromium(III) coordination compound and various substituted pyrrole ligands on ethylene oligomerization in the presence of a Cr(III) complex–pyrrole ligand (L)/AlEt3 catalyst system (CS), where Cr(III) is Cr(EH)3, Cr(асас)3, or CrCl3(THF)3 and L is pyrrole, 2-phenylpyrrole, 2-formylpyrrole, N-methylpyrrole, or N-vinyl-2-phenylpyrrole, has been studied. It has been shown that the most significant effect on the behavior of the CS is exerted by the nature of the ligand involved in the formation of the CS. The acid–base properties of the employed ligands have been determined by quantum-chemical calculations. The data obtained have revealed that selectivity of the catalyst system depends on the ligand basicity.

Nickel-functionalized UiO-66 metal organic frameworks (MOFs) oligomerize ethylene in the absence of cocatalysts or initiators after undergoing ethylene-pressure-dependent transients and maintain stable oligomerization rates for >15 days on stream. Higher ethylene pressures shorten induction periods and engender more active sites for ethylene oligomerization; these sites exhibit invariant selectivity-conversion characteristics to justify that only one type of catalytic center is relevant for oligomerization. The number of active sites is estimated using in situ NO titration to disambiguate the effect of increased reaction rates upon exposure to increasing ethylene pressures. After accounting for augmented site densities with increasing ethylene pressures, ethylene oligomerization is first order in ethylene pressure from 100 to 1800 kPa with an activation energy of 81 kJ mol-1 at temperatures from 443-503 K on Ni/UiO-66. A representative Ni/UiO-66 cluster model that mimics high ethylene pressure process conditions is validated with ab initio thermodynamic analysis, and the Cossee-Arlman mechanism is posited based on comparisons between experimental and computed activation enthalpies from density functional theory calculations on these cluster models of Ni/UiO-66. The insights gained from experiment and theory help rationalize evolution in structure and stability for ethylene oligomerization Ni/UiO-66 MOF catalysts.

Ethylene oligomerization reaction on Ni-modified and unmodified ZSM-5 catalysts was studied at ambient pressure as a function of temperature by in situ FT-IR spectroscopy and mass spectrometry, focusing the attention on the formation of adsorbed species, which are likely to be responsible for the catalysts deactivation. The two catalysts show similar catalytic performance and selectivity, but different stability with time-on-stream, particularly in the 300–400 °C range. On both catalysts alkylated compounds and unsaturated carbocations were observed as stable adsorbed species up to 300 °C. The deactivation of the Ni-ZSM5 catalyst was related to the formation of a complex mixture of methylated polycondensed aromatic compounds (coke/coke precursors), which are not desorbed even by increasing the temperature up to 400 °C. In contrast, at 400 °C ethylene oligomerization on H-ZSM5 sample proceeds without deactivation due to the higher desorption rate of the surface species, which are mainly unsaturated carbocations with small amounts of methylated poly-condensed aromatics.

Support effect in ethylene oligomerization mediated by heterogenized nickel catalysts

A series of bispyridylamine ligands and chromium complexes designed for ethylene oligomerization have been synthesized, which was made up of both neutral organic ligand and inorganic anion. The compositions of these complexes have been fully characterized by spectroscopic and analytical methods. Catalysts (Cr1–Cr4) were evaluated in detail with methylaluminoxane (MAO) as an activator in the ethylene oligomerization. As a result, Cr1 achieved a higher catalytic activity of 2.93 × 105g/(mol(Cr) h) and a higher selectivity of 55.34% toward the valuable C8 compound using toluene as the solvent. The total selectivity to LAOs was 71.2%.

Ethylene oligomerization catalyzed by a novel iron complex containing fluoro and methyl substituents