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The regio- and enantioselective functionalization of 1,3-dienes has become a powerful tool for the synthesis of allylic compounds, yet it remains a challenge for aliphatic dienes. Herein, we report...

This work investigated the influence of the catalytic support precursor on the activity of nickel catalysts 20%Ni/5%La2O3–95%Al2O3 in the mixed methane reforming process. The activity tests were carried out at a temperature of 750 °C. The research showed that the catalyst prepared from the precursor containing chloride exhibited very low conversions of methane and carbon dioxide. The poisoned catalyst system before and after the calcination process was subjected to Temperature Programmed Surface Reaction tests to determine whether the thermal treatment causes a decrease in the amount of chlorine in the system. To determine the decomposition temperature of the LaCl3 precursor and the nickel chloride NiCl2 compound, the samples were analyzed by Thermogravimetry. Finally, the catalytic samples were tested by Time-of-Flight Secondary Ion Mass Spectrometry analysis to confirm the presence of nickel–chlorine bonds on the surface of the catalytic system.

The structure of Ni active sites supported on amorphous silica-alumina supports with different contents of Al2O3 loadings in relation to their activities in ethylene oligomerization were investigated. Two kinds of Ni sites were detected by in situ FTIR-CO and H2-TPR experiments, that are Ni2+ cations as grafted on weak acidic silanols and Ni2+ cations at ion-exchange positions. The ethylene oligomerization activities of these Ni/ASA catalysts were found an ascending tendency as the Al2O3 loading decreased, which could be attributed to the enriched concentration of Ni2+ species on acidic silanols with a weaker interaction with the amorphous silica-alumina support. These Ni2+ species were more easily to be evolved into Ni+ species, which has been identified to be the active sites of ethylene oligomerization. Thus, it seems reasonable to conclude that Ni2+ species grafted on acidic silanols were the precursors of active sites.

Funding for this work was provided by King Abdullah University of Science and Technology (KAUST). The authors wish to thank and acknowledge to Dr. Serhii Vasylevskyi from KAUST-Core labs for his support during the Raman spectroscopy measurements, Dr. Natalia Morlanes for her assistance for the flow-reactor configuration, and Sandra Ramirez for the art work.

Alkylbenzenes coupled with isocyanates at the benzylic position upon irradiation with visible light in the presence of an iridium photoredox catalyst, a bromide anion, and a nickel catalyst, produc...

Tar formation is a significant issue during biomass gasification. Catalytic removal of tars with the use of nickel catalyst allows to obtain high conversion rate but coke formation on catalysts surface lead to its deactivation. Toluene decomposition as a tar imitator was studied in gliding discharge plasma-catalytic system with the use of 5%, 10% and 15% by weight Ni and NiO catalyst on Al2O3 (α-Al2O3) and Peshiney (γ-Al2O3) carrier in gas composition similar to the gas after biomass pyrolysis. The optimal concentration of nickel was identified to be 10% by weight on Al2O3. It was stable in all studied initial toluene concentrations, discharge power while C7H8 conversion rate remained high – up to 82%. During the process, nickel catalysts were deactivated by sooth formation on the surface. On catalysts surface, toluene decomposition products were identified including benzyl alcohol and 3-hexen-2-one.

It is of great importance and is highly desired in the olefin polymerization catalysis that a simple catalyst derived from cheap starting materials and short synthetic pathways exhibits superior catalytic property towards a polymerization reaction. In this contribution, starting from commercially available and cheap materials, by using a short and simple three-step reaction route we report a readily available neutral phenoxy-imine nickel catalyst, which significantly enables the formation of linear ultrahigh molecular weight polyethylene (~5 brs/1000C, Mn = 1531 kDa) in a living polymerization (PDI = 1.08–1.11). An enhancement of 77 times on the polymer molecular weight occurs compared to the classical 2,6-diisopropyl substituted phenoxy-imine nickel catalyst. This avoids a tedious synthetic procedure and the use of an excess aluminum reagent as the activator and the scavenger.

[EN] The performance of nickel supported on lanthana-modified hydroxyapatite (HAP) catalysts is investigated in the CO2 methanation. The addition of La (1-6.6 wt%) leads to a surface enrichment following a sequential multilayer deposition model. Moreover, La addition systematically improves the dispersion of Ni particles and their reducibility, which in turn increases spectacularly the amounts of basic sites and their thermal stability. Such physicochemical changes impact positively on the activity of the catalysts in CO2 methanation. The estimated turnover frequency (TOF) suggest that the small Ni particles are the most efficient. The latter seem to provide a large density of very active defects on Ni-La2O3 interface. The optimized catalyst proves to be highly resistant to deactivation during 100 h time-on-stream (TOS). The samples were also assayed as dual function materials (DFMs) for CO2 adsorption and methanation. A scheme is proposed to describe the different steps involved in a CO2 adsorption/hydrogenation cycle. The financial support from the Science and Innovation Spanish Ministry (PID2019-105960RB-C21) and the Basque Government (IT1297-19) is acknowledged. The authors also acknowledge the technical support provided by SGIker (UPV/EHU Advanced Research Facilities/ERDF, EU) .

In this work, a reliable kinetic reaction mechanism was revised to accurately reproduce the detailed reaction paths of steam reforming of methane over a Ni/Al2O3 catalyst. A steady-state fixed-bed reactor experiment and a 1D reactor catalyst model were utilized for this task. The distinctive feature of this experiment is the possibility to measure the axially resolved temperature profile of the catalyst bed, which makes the reaction kinetics inside the reactor visible. This allows for understanding the actual influence of the reaction kinetics on the system; while pure gas concentration measurements at the catalytic reactor outlet show near-equilibrium conditions, the inhere presented temperature profile shows that it is insufficient to base a reaction mechanism development on close equilibrium data. The new experimental data allow for achieving much higher quality in the modeling efforts. Additionally, by carefully controlling the available active surface via dilution in the experiment, it was possible to slow down the catalyst conversion rate, which helped during the adjustment of the reaction kinetics. To assess the accuracy of the revised mechanism, a monolith experiment from the literature was simulated. The results show that the fitted reaction mechanism was able to accurately predict the experimental outcomes for various inlet mass flows, temperatures, and steam-to-carbon ratios.

The effect of Ti and Al incorporation to FSM-16 framework as the support of Ni catalysts on their catalytic performance in the reaction of dry reforming of methane (DRM) was investigated. A series of Ni/M-FSM-16 (M = Al, Ti) with M/Si molar ratio = 100, 50, 20 were synthesized via double-solvent impregnation of Nickel. Fresh catalysts were characterized using N2 adsorption/desorption, XRD, FTIR, FE-SEM, H2-TPR analyses. The prepared catalyst went through DRM reaction at 750, 800, and 850 °C. The spent catalysts of best catalytic performance, i.e. Ni/Al50-FSM-16 and Ni/Ti100-FSM-16, were analyzed by FT-IR and O2-TPO to characterized carbonaceous deposits. Based on TPR results, the promotion of DRM performances was related to the strength of Ni interaction with supports to which Ti or Al was incorporated. Conversion of CH4 and CO2, and H2/CO ratio of the products via Ni/Al50-FSM-16 catalyst were promoted by 95%, 83%, 25% with respect to Ni/FSM-16 at 850 °C, respectively.

Nickel-catalyzed reductive homocoupling of aryl ethers has been achieved with Mg(anthracene)(thf)3 as a readily available low-cost reductant. DFT calculations provided a rationale for the specific efficiency of the diorganomagnesium-type two-electron reducing agent. The calculations show that the dianionic anthracene-9,10-diyl ligand reduces the two aryl ether substrates, resulting in the homocoupling reaction through supply of electrons to the Ni-Mg bimetallic system to form organomagnesium nickel(0)-ate complexes, which cause two sequential C–O bond cleavage reactions. The calculations also showed cooperative actions of Lewis acidic magnesium atoms and electron-rich nickel atoms in the C–O cleavage reactions.

Asymmetric hydrocarbofunctionalization of alkenes has emerged as an efficient strategy for synthesizing optically active molecules through a carbon–carbon bond-forming process from readily available alkenes and carboelectrophiles. Here, we present a summary of our efforts to control the regio- and enantioselectivity of hydrocarbofunctionalizations of electron-deficient alkenes with a nickel catalyst and a chiral bisoxazolidine ligand. The reaction permits electron-reversed hydrocarbofunctionalizations of acrylamides with excellent enantioselectivity. This operationally simple protocol permits the asymmetric hydroalkylation, hydrobenzylation, or hydropropargylation of acrylamides. This reaction is useful for preparing a wide range of α-branched chiral amides with broad functional-group tolerance.

The effect of the conditions for carrying out the reaction of liquid-phase hydrogenation of the nitro group on a bulk nickel catalyst in a binary water–alcohol solution has been studied. It is shown that each stage of the catalytic process leads to a change in the structure of the active nickel surface. The influence of hydrogen adsorption, adsorption of catalytic poison, and chemical effects on the catalyst surface, as well as the hydrodynamic conditions of the process on the catalyst particle size, structure, and surface morphology, was studied. It has been experimentally proven that the resulting adsorption–catalytic deformation leads to an increase in the rates of reduction of compounds containing a nitro group at low degrees of conversion.

Effect of divalent metals was studied in the cross-coupling polymerization of thiophenes leading to head-to-tail-type poly-3-hexyl­thiophene. Deprotonation of the C–H bond at the 5-position of 2-halo-3-hexylthiophene by LDA followed by metal exchange was carried out in one pot and following addition of nickel catalyst underwent polymerization. One-shot reaction involving deprotonation/transmetalation/ cross coupling polymerization was also examined with manganese(II) chloride and nickel(II) catalyst.

A highly efficient regioselective method for allene hydroboration has been developed, with the regioselectivity governed primarily by the appropriate choice of the metal. Boryl addition to internal or external carbon–carbon bonds of the allene unit was achieved when nickel and cobalt bearing easily available phosphorus ligands were respectively employed. The complementary methods allow either regioisomeric products to be obtained with exceptional regiocontrol. It is worth mentioning that the nickel catalyst is for the first time reported to be used in allene hydroboration.

The conversion of levulinic acid (LA) to γ-valerolactone (GVL) is one of the most important reactions from biomass-derived platform chemicals to value-added chemicals. In this work, nitrogen-doped carbon was introduced into a Ni/Al2O3 catalyst and was employed for the hydrogenation of LA to GVL with a full conversion and equivalent yield under mild conditions, at as low as ambient hydrogen pressure and 130 °C for 6 h. The doping of nitrogen introduced NiNx species and the imperfection of modified nitrogen-doped carbon were beneficial for the selective hydrogenation of carbonyl groups. This catalyst showed excellent activity and selectivity in various solvents and could be recycled for at least 6 runs with little deactivation. In addition to LA, various substrates with both carbonyl and carboxyl groups could also be selectively hydrogenated to the corresponding lactones. This study offers both theoretical foundation and practical instructions for the high-efficiency conversion of LA to GVL over non-noble metal catalysts under mild conditions, especially ambient H2 pressure.

An effective shielding of both apical positions of a neutral NiII active site is achieved by dibenzosuberyl groups, both attached via the same donors’ N‐aryl group in a C s‐type arrangement. The key aniline building block is accessible in a single step from commercially available dibenzosuberol. This shielding approach suppresses chain transfer and branch formation to such an extent that ultrahigh molecular weight polyethylenes (5×106 g mol−1) are accessible, with a strictly linear microstructure (, The β‐H elimination event that brings about chain transfer and branch formation in neutral nickel‐catalyzed olefin insertion polymerization is now fully addressed by a C s‐type shielding of both apical positions of a neutral NiII catalyst. Thus, strictly linear (

Readily available aryldimethylsulfonium triflates react with zinc powder under nickel catalysis via the selective cleavage of the sp2-hybridized carbon–sulfur bond to produce salt-free arylzinc triflates under mild conditions. This zincation displays superb chemoselectivity and thus represents a protocol that is complementary or orthogonal to existing methods. The generated arylzinc reagents show both high reactivity and chemoselectivity in palladium-catalyzed and copper-mediated cross-coupling reactions.

The effect of reaction conditions on ethanolysis of enzymatic hydrolysis lignin (EHL) with an unsupported nickel catalyst, that is, Ni(220H), was investigated. The two-dimensional heteronuclear single quantum coherence-nuclear magnetic resonance (2D-HSQC NMR) analysis of liquid products revealed that both the ether and C-C linkages in EHL were cleaved during the reaction and the ether linkages were completely cleaved under mild reaction conditions, while the cleavage of C-C linkages needed harsh reaction conditions. At 280 °C under 2 MPa H2 within 6 h, the highest aromatic monomer yield of 28.5 wt % was achieved. Further increasing the reaction temperature to 300 °C or decreasing the initial hydrogen pressure to 0 MPa was conducive to the repolymerization reaction. The ortho-alkyl phenol monomers originated from the alkyl free radicals produced from ethanol. Under 0 MPa H2, the hydrogenation of -HCCH- in side chains was inefficient, and hence, the decarboxylation and alkenyl elimination reactions of side chains were favorable.

A stable, reusable, and insoluble poly(4-vinylpyridine) nickel catalyst (P4VP-NiCl2) was prepared through the molecular convolution of poly(4-vinylpyridine) (P4VP) and nickel chloride. We proposed ...

The propane conversion in a membrane reactor with NIAP–03-01 commercial Ni catalyst at temperatures of 673, 723, 773, and 823 K, feed space velocities of 1800 and 3600 h–1, and steam/propane ratios of 5 and 7 was studied. The Н2 removal through the membrane leads to an increase in the conversion of the feed to Н2 and СО2 formed by the water-gas shift reaction. The conversion in this reaction increases when the rate of the Н2 recovery through the membrane is increased by the permeate evacuation. In the temperature interval 773–823 K, the feed conversion is 100%, and about 90% of high-purity Н2 is recovered from the reaction mixture. An increase in the feed/catalyst contact time leads to a decrease in the feed conversion to the target products and to an increase in the rate of carbon deposit formation. The regularities of the steam conversion of propane in a membrane reactor are similar to those found previously for n-butane with the same catalyst and under the same conditions.

The carboxylation of propargylic alcohols containing a silyl group at the terminal position was conducted in a CO2 atmosphere at atmospheric pressure in the presence of a nickel catalyst and diethy...

Enantioselective difunctionalization of alkenes constitutes an efficient strategy to assemble complex chiral molecules from simple racemic or achiral starting materials. Here we present an intermolecular nickel-catalysed enantioselective 1,1-arylboration of unactivated terminal alkenes. The high regio- and enantioselectivities of the reactions arise from a judicious choice of the nickel catalyst rather than the incorporation of a directing group. Moreover, excellent regioselectivities can also be obtained from the reactions of allylbenzenes. We also conducted a series of stereospecific downstream transformations for the enantioenriched secondary boronic esters. These examples represent an efficient catalyst-controlled enantioselective 1,1-difunctionalization of unactivated alkenes. Difunctionalization of alkenes can afford useful building blocks from readily available starting materials, but these reactions often show limitations in olefin scope. This work presents a catalyst-controlled enantioselective 1,1-arylboration of unactivated alkenes that is independent of directing groups.

In this study, nickel-based catalyst supported on multi-walled carbon nanotube (Ni/MWCNT) was synthesized and used in NO2 removal from polluted air. Scanning Electron Microscopy (SEM) and Energy Di...

Both catalytic activity and polymer molecular weight are two crucial parameters in olefin polymerization catalysis. Differed from the superior feature of early transition metal catalysts, late transition metal nickel catalysts are usually more challenging to approach both of them at an ultrahigh level. In this contribution, by use of a concerted double-layer steric strategy a new conceptual α-diimine nickel catalyst was prepared to address the issues. The nickel catalyst featured highly thermally robust (0–150 °C), was ultra-highly active (a new level of 1.03 × 109 g mol−1 h−1) toward ethylene polymerization, and simultaneously produced ultrahigh molecular weight polyethylene product (UHMWPE, Mw = 4.2 × 106 g mol−1). Additionally, these obtained polyethylenes featured linear (2/1000C) to lightly branched (32/1000C) and could also be incorporated with a small amount of methyl 10-undecenoate.

The aim of this research was to study the recycling process and the feasibility to smelt the spent nickel catalyst for the production of nickel alloy or ferronickel. The smelting process was carried out in a laboratory induction furnace. The effects of SiO2/CaO for slag forming on metal recovery and smelting time were investigated. Petroleum coke was used as reductant. Mill scale was used as an iron resource for ferro-alloy production, while CaO was used as slag forming agent. The raw materials were mixed together and put into a graphite crucible, which was then placed in the induction furnace. After the melt was completed, the melt was poured into a mold to solidify. The chemical composition of the product was analyzed by XRF and XRD. It was found that the smelting time was decreased with increasing SiO2/CaO from 1.0 to 2.3. For nickel alloy production, increasing of SiO2/CaO increased the weight of metal product. For the ferronickel production, however, the weight of metal product was found not to vary with different ratio of SiO2/CaO.

A PEG1000-modified nickel-based catalyst (Ni-PEG1000/FC3R) supported on an activated fluid catalytic cracking catalyst residue (FC3R) was synthesized and applied to C9 petroleum resin (C9PR) hydrogenation. The results of the Brunauer–Emmett–Teller method, X-ray diffraction, H2 temperature-programmed reduction, and scanning electron microscopy–energy-dispersive X-ray spectroscopy show that the Ni-PEG1000/FC3R catalyst had a smaller crystallite size and higher Ni dispersion than those of a Ni/FC3R catalyst. The prepared Ni-PEG1000/FC3R catalyst was applied in a hydrogenation of C9PR at 270 °C and 6 MPa H2 pressure for 3 h. Under these conditions, the bromine value of C9PR was decreased from 46.1 g Br/100 g (Gardner color grade no. 11) to 0.72 g Br/100 g (Gardner color grade no. 1), and the sulfur content was reduced from 25.7 to 1.66 mg kg–1. Experimental results show that the Ni-PEG1000/FC3R catalyst exhibited high activity and stability for C9PR hydrogenation.

Solid supports play an indispensable role in heterogeneous catalysis, as they can directly affect the catalytic activity and selectivity of supported catalysts. However, the specific roles of such ...

Objectives. This study is devoted to developing new-generation nickel (Ni) catalysts for the purification of a nitrogen–hydrogen mixture from carbon oxides, which should encompass the best qualities of the NIAP-07-series solid catalysts. Methods. This study used derivatographic and radiographic methods; temperature-programmed recovery, decomposition, and joint temperature-programmed decomposition and recovery; and low-temperature nitrogen adsorption (specific surface determination). The mechanical strength of catalysts was determined using an MP-2C device by crushing granules with an applied load on the end face. The chemical composition and catalytic activity were determined by the methods of TU 2178-003-00209510 Technical Conditions. Results. Many studies regarding Ni–aluminum (Al)–calcium (Ca) methanation catalyst at all stages of its preparation have been conducted. It is demonstrated that Ni hydrocarboxyaluminate, a precursor of the active component of the catalyst, is formed when Ni hydroxocarbonate is mixed with active alumina in the presence of an aqueous solution of ammonia, and its chemical formula is established. Moreover, it was found that the mechanical strength of the catalyst is determined by the amount of industrial Ca aluminate added to the Ni–Al composition. The compositions of catalysts with different contents of the active component have been optimized. Conclusions. The developed catalyst has a low activation temperature and high catalytic activity, thermal stability, and mechanical strength and is resistant to organic and alkaline carbon dioxide absorbers. The catalyst can be produced in the form of a ring, cylindrical tablets, and extrudates of various geometric sizes. The methanation unit at Stavrolen (Budennovsk, Stavropol krai, Russia) has begun commercially operating the catalyst.