Hydroformylation Of 1-hexene Research Articles

Effective hollow Rh@H-S-1 catalyst for hydroformylation of 1-hexene

A hollow zeolite encapsulated Rh catalyst Rh@H-S-1 with an “eggshell” structure was prepared using the method of organic alkali treatment and recrystallization. Compared with catalysts with directly encapsulated Rh@S-1 and surface impregnated Rh/S-1, this catalyst exhibited both superior activity and a higher TOF value in hydroformylation of 1-hexene due to the high dispersion of Rh and high diffusion. The Rh element did not need to be reduced in the preparation, and it was in situ reduced by the syngas. The content of lower valence Rhδ+ gradually increased with the reaction procedure and played as an active center. The low oxidized state Rh+ or Rhδ+ in the form of Rh(CO)2 are proposed as active sites in hydroformylation, which were generated under the synergistic effect between CO and H2. Importantly, the hollow encapsulated catalyst effectively decreased Rh leaching to 0.1 ppm and showed better stability compared with the impregnated Rh/S-1 catalyst.

Constructing Co@C nanoparticles with chainmail-structure for highly efficient hydroformylation of 1-hexene

Constructing highly active noble-metal-free heterogeneous catalysts is the crux for the hydroformylation of long-chain α-olefins. Herein, novel chainmail-structured cobalt oxide nanoparticles (CoO@C|SBA-15) are fabricated by the channel confinement strategy, which display excellent activity for the 1-hexene hydroformylation. Specifically, the obtained catalyst shows 100% 1-hexene conversion and 94% heptanal selectivity, as well as up to 2.0 linear to branch (l/b) ratio, outperforming most of heterogeneous noble metal catalysts. Remarkably, in-situ DRIFT spectra combined with density functional theory calculations disclosed the metallic Co derived from in-situ reconstruction of CoO is the key active site for 1-hexene hydroformylation. Specifically, the reconstructed Co site is responsible for the adsorption of 1-hexene, and the graphite carbon layer promotes the adsorption of H2 and CO by interacting with the reconstructed Co. Moreover, the graphite carbon layer provides a strong protective effect on the internal cobalt active sites and thus enhances the catalytic stability during the harsh condition. This work provides a new method for designing the low-cost heterogeneous catalyst and emphasizes the intrinsic active sites for 1-hexene hydroformylation reaction.

Grafting EDTA in UiO-66 to modulate the microenvironment of Rh for 1-hexene Hydroformylation

Oriented designing the microenvironment of catalytic sites is essential for understanding catalytic processes. In this work, EDTA was first grafted in UiO-66 and then chelated Rh to obtain an efficient catalyst for 1-hexene hydroformylation reaction. EDTA not only served as a chelation site for Rh immobilization in UiO-66, but also markedly influenced the structure and properties of Rh/UiO-66. The incorporation of EDTA reduced the micropore content and suppressed the formation of heavy products. Moreover, the grafted EDTA regulated the electronic state of Rh effectively to improve the CO and propene adsorption, thus constructing an appropriate microenvironment for hydroformylation. Therefore, EDTA-modified Rh/U-E catalyst exhibited higher aldehydes yield, TOF and stability than Rh/U without EDTA. The dual role of EDTA in anchoring Rh sites and modulating the microenvironment for hydroformylation provides more prospects for designing customized MOFs-based catalysts.

Heterogeneous Phosphine-Containing Hydroformylation Catalysts Based on Modified Porous Organic Framework

A series of heterogeneous phosphine-containing rhodium hydroformylation catalysts based on porous aromatic frameworks (PAFs) were prepared. The catalysts PAF30-MDEA-TPPTS-Rh (TPPTS is trisodium triphenylphosphine-3,3',3''-trisulfonate, MDEA is methyldiethanolamine fragment) and PAF-30-Im-TPPTS-Rh (Im is imidazole fragment) showed the highest stability in repeated use in 1-hexene hydroformylation. The catalyst PAF-30-MDEA-TPPTS-Rh before and after use in hydroformylation was characterized by elemental C,N,H,S analysis, inductively coupled plasma atomic absorption spectroscopy, low-temperature nitrogen adsorption–desorption, transmission electron microscopy, IR spectroscopy, and X-ray photoelectron spectroscopy. The effect of temperature, pressure, and solvent on the course of hydroformylation in the presence of PAF-30-MDEA-TPPTS-Rh was studied. The catalyst is active in hydroformylation of a series of unsaturated compounds, including functionalized substrates and olefins with internal double bond.

Construction of Rh-N4 single atoms and Rh clusters dual-active sites for synergistic heterogeneous hydroformylation of olefins with ultra-high turnover frequency

The design and construction of Rh-based heterogeneous catalysts with excellent catalytic activity and high atom utilization for hydroformylation of olefins is extremely important but still challenging. Herein, we report a robust dual-active sites coupling catalyst containing triphenyl phosphine-coordinated Rh clusters and Rh-N4 single atomic sites (PPh3-RhAC-SA/N-C) for hydroformylation of olefins. The PPh3-RhAC-SA/N-C exhibits ultra-high activity to the hydroformylation of 1-hexene among the reported Rh-based catalysts, achieving the turnover frequency value of 6599 h−1, which is 13-fold higher than that of conventional Wilkinson’s catalyst (508 h−1). Density functional theory calculations reveal that PPh3-coordinated Rh clusters can facilitate the adsorption and activation of olefins and H2. The adjacent Rh-N4 provides a more favorable adsorption site for CO, enabling the easy addition of CO to carbon chain. The incorporated PPh3 increases the electron cloud density of Rh clusters, reduces the energy barriers of hydrogenation step on Rh clusters, and thereby enhancing the activity of catalyst for hydroformylation. Furthermore, PPh3-RhAC-SA/N-C can be applied as a recyclable catalyst without obvious deactivation. This work provides a novel design concept for the construction of dual sites coupling catalyst from the atomic scale for synergistic heterogeneous hydroformylation.

Tandem Hydroformylation-Aldol Condensation Reaction Enabled by Zn-MOF-74.

The tandem hydroformylation-aldol condensation (tandem HF-AC) reaction offers an efficient synthetic route to the synthesis of industrially relevant products. The addition of Zn-MOF-74 to the cobalt-catalyzed hydroformylation of 1-hexene enables tandem HF-AC under milder pressure and temperature conditions than the aldox process, where zinc salts are added to cobalt-catalyzed hydroformylation reactions to promote aldol condensation. The yield of the aldol condensation products increases by up to 17 times that of the homogeneous reaction without MOF and up to 5 times compared to the aldox catalytic system. Both Co2(CO)8 and Zn-MOF-74 are required to significantly enhance the activity of the catalytic system. Density functional theory simulations and Fourier-transform infrared experiments show that heptanal, the product of hydroformylation, adsorbs on the open metal site (OMS) of Zn-MOF-74, thereby increasing the electrophilic character of the carbonyl carbon atom and facilitating the condensation.

Repair of missing linker defects in UiO-66 by a "molecular patch" boosting the 1-hexene hydroformylation reaction.

Fabrication of MOFs with missing linker defects has become a common means to improve catalytic performances. However, the stability of the defects deserves to be investigated first. In this work, we found that 3-phenylpropionaldehyde (3-PPA) could coordinate with the missing linker defects of UiO-66, which highlighted the instability of the missing linker defects. 3-PPA acted as a molecular patch for the modification of the Rh/UiO-66 catalyst, which repaired the open Zr6 sites and resulted in a remarkable improvement of aldehyde selectivity (from 50.0% to 89.6%) in 1-hexene hydroformylation.

Multi-phase CFD modelling for hydroformylation of 1-hexene with microbubbles

Based on the micro-bubbling process as an intensification method, an experimental study on hydroformylation of 1-hexene was carried out. Effects of different total pressures, temperatures, partial pressures and substrate concentrations on the conversion rate of olefin and normal-to-iso ratio were investigated and the reaction kinetic coefficients were determined by fitting the experimental data with the model. Using the Euler two-fluid and standard k-ε turbulence model, a computational fluid dynamics model was established to describe the multi-phase flow mass transfer and reaction of olefin hydroformylation. The simulation results were in good agreement with the experimental results. Furthermore, the effects of microbubble sizes and internal components on the overall gas holdup, mass transfer rate, turbulent mixing and reaction efficiency of the multi-phase 1-hexene hydroformylation reaction system were studied, which could be applied to the process intensification and scale-up of the various multi-phase gas-liquid hydroformylation reactions.

Silicalite-1 encapsulated rhodium nanoparticles for hydroformylation of 1-hexene

Hydroformylation has been applied in the chemical industry for decades to produce n-aldehydes from 1-olefins and syngas (a mixture of CO and H2). However, the difficulty of catalyst separation and harsh operating conditions of conventional homogeneous hydroformylation reactions have prompted researchers to explore heterogeneous catalytic strategies. In this work, a novel core-shell structured catalyst comprised of Rhodium nanoparticles (Rh NPs) homogeneously encapsulated in a silicalite-1 zeolite (Rh@S-1) is designed to realize a high activity in 1-hexene hydroformylation. The conversion of 1-hexene over the Rh@S-1 catalyst exhibits as high as 85.8%, and the ratio of n-heptanal to iso-heptanal reaches up to 2.5 at 90 °C. Multiple studies demonstrate that the outstanding catalytic activity over this core-shell structured catalyst can be explained by the highly active homogeneously dispersed Rh NPs and the distinguishable mass transfer effect of the unique and orderly micropores structure of silicalite-1 zeolite. Furthermore, by changing templating agent concentrations during the hydrothermal method, the size of the zeolite crystals can be easily controlled and is proven to be an essential factor affecting the hydroformylation performance.

Multi-nuclear, high-pressure, operando FlowNMR spectroscopic study of Rh/PPh3 - catalysed hydroformylation of 1-hexene.

The hydroformylation of 1-hexene with 12 bar of 1 : 1 H2/CO in the presence of the catalytic system [Rh(acac)(CO)2]/PPh3 was successfully studied by real-time multinuclear high-resolution FlowNMR spectroscopy at 50 °C. Quantitative reaction progress curves that yield rates as well as chemo- and regioselectivities have been obtained with varying P/Rh loadings. Dissolved H2 can be monitored in solution to ensure true operando conditions without gas limitation. 31P{1H} and selective excitation 1H pulse sequences have been periodically interleaved with 1H FlowNMR measurements to detect Rh-phosphine intermediates during the catalysis. Stopped-flow experiments in combination with diffusion measurements and 2D heteronuclear correlation experiments showed the known tris-phosphine complex [RhH(CO)(PPh3)3] to generate rapidly exchanging isomers of the bis-phosphine complex [Rh(CO)2(PPh3)2] under CO pressure that directly enter the catalytic cycle. A new mono-phosphine acyl complex has been identified as an in-cycle reaction intermediate.

A Novel Strategy of Homogeneous Catalysis and Highly Efficient Recycling of Aqueous Catalyst for the Hydroformylation of Higher Olefins Based on a Simple Methanol/Water Mixed Solvent

This paper describes the homogeneous catalysis and highly efficient recycling of aqueous catalyst for the hydroformylation of higher olefins in the methanol/water mixed solvent for the first time. When sufficient methanol is added into aqueous HRh(CO)(TPPTS)3/TPPTS solution and 1-hexene, the reaction mixture becomes a single phase at reaction temperature (TPPTS: Trisodium triphenylphosphine-3,3′,3″-trisulfonate), which makes the 1-hexene hydroformylation proceed homogeneously. The turnover number (TON) is 11880 during an hour, and TON is up to 10428 during half an hour at a substrate to catalyst ratio of 12000. After the reaction, the methanol with low boiling point can be readily recovered by distilling the product mixture at the reaction temperature. And then, what's left is the aqueous organic two-phase mixture. The aqueous catalyst solution can be separated from the products by a simple decantation. The recovered aqueous catalyst solution as well as methanol can be recycled for seven runs without significant loss of activity and selectivity for aldehydes. Moreover, the average rhodium leaching in products is less than 0.09 wt%.

Enhanced Hydroformylation in a Continuous Flow Microreactor System

A microreactor system consisting of a honeycomb microreactor and microtubing was proposed to enhance the Rh-biphephos catalyzed hydroformylation of 1-hexene. The effects of various reaction paramet...

Porous Organic Polymer Supported Rhodium as a Reusable Heterogeneous Catalyst for Hydroformylation of Olefins.

A new porous organic polymer has been prepared via copolymerization of divinyl-functionalized phosphoramidite ligand and tris(4-vinylphenyl)phosphine. The porous polymer was loaded with Rh(acac)CO2 to yield a supported Rh catalyst, which demonstrated good regioselectivity ( l/ b = 6.7-52.8) and high catalytic activity (TON up to 45.3 × 104) in hydroformylation of terminal and internal olefins. Remarkably, the heterogeneous catalyst can be reused at least 10 cycles without losing activity and selectivity in hydroformylation of 1-hexene.

Aqueous-biphasic hydroformylation of 1-hexene catalyzed by the complex HCo(CO)[P(o-C6H4SO3Na)

The water soluble cobalt complex HCo(CO)[P(o-C6H4SO-3Na)]3 was used as catalyst precursor for the biphasic aqueous hydroformylation of 1-hexene. The complex was synthesized by reductive carbonylation of CoCl2.6H2O in the presence of o-TPPTS ([P(o-C6H4SO3Na)]3) under nitrogen atmosphere and characterized by FTIR, 1H NMR and 31P {1H} NMR, 13C NMR, DEPT – 135, COSY, HSQC, MS (ESI). The catalytic activity of the complex in the biphasic hydroformylation reaction of 1-hexene was evaluated under moderate reaction conditions. The pressure and temperature were varied from 4137 – 7584 kPa (600-1100 psi) of syngas and from 353 – 383 K (80 – 110 °C), respectively. The 1-hexene concentration was varied from 0.021-0,11M and the catalyst from 4x10-4 - 1.1x10-3 M. The best conversion at 363 K and 7584 kPa and 7.5 h was 62% with selectivity towards aldehydes (heptanal and 2-methyl-hexanal) of 66% to with l/b ratio of 2.6. The recycling of the catalytic precursor after four successive times, did not show any loss on the activity, having selectivity towards aldehyde up to 60%.

Oxygenates Synthesis by Hydroformylation of 1-hexene over Co Nanoparticle Catalyst

Oxygenates Synthesis by Hydroformylation of 1-hexene over Co Nanoparticle Catalyst

MECHANISTIC STUDY OF A RUTHENIUM HYDRIDE COMPLEX OF TYPE [RuH(CO)(N-N)(PR3)2]+ AS CATALYST PRECURSOR FOR THE HYDROFORMYLATION REACTION OF 1-HEXENE

The catalytic activity of systems of type [RuH(CO)(N-N)(PR3)2]+ was evaluated in the hydroformylation reaction of 1-hexene. The observed activity is ex­plained through a reaction mechanism on the basis of the quantum theory. The mechanism included total energy calculations for each of the intermediaries of the elemental steps considered in the catalytic cycle. The deactivation of the catalyst precursors takes place via dissociation of the polypyridine ligand and the subse­quent formation of thermodynamically stable species, such as RuH(CO)3(PPh3)2 and RuH3(CO)(PPh3)2, which interrupt the catalytic cycle. In addition, the theoreti­cal study allows to explain the observed regioselectivity which is defined in two steps: (a) the hydride migration reaction with an anti-Markovnikov orientation to produce the alkyl-linear-complex ( 3.1a ), which is more stable by 19.4 kJ/mol than the Markovnikov orientation (alkyl-branched-complex) ( 3.1b ); (b) the carbon monoxide insertion step generates the carbonyl alkyl-linear specie ( 4.1a ) which is more stable by 9.5 kJ/mol than the alternative species ( 4.1b ), determining the preferred formation of heptanal in the hydroformylation of 1-hexene.

A Fine Dispersed Cobalt Catalyst with Macro-Pore for Hydroformylation of 1-Hexene

A highly dispersed cobalt catalyst for hydroformylation of 1-hexene was developed using macroporous silica (pore diameter 83.7 nm) as support. The effects of support pretreatment on the properties and catalytic activities of the obtained catalysts were investigated. The results indicated that slurry impregnation (SI) method could significantly enhance the interaction between support and cobalt precursors, leading to the formation of small cobalt particles. Moreover, this interaction would increase with the pretreating temperature or the number of hydroxyl groups in pretreating solvent. Due to the small cobalt particles and high diffusion rate of reactants and products in the macropore, the highly dispersed Co/Q-100 (PTO, SI-333) catalyst exhibited 11 times higher heptanal yield and much higher n/i ratio than the conventional Co/SiO2 (EG) catalyst which was prepared on mesoporous silica which contained similar cobalt particle size.

Enhancing catalytic performance of activated carbon supported Rh catalyst on heterogeneous hydroformylation of 1-hexene via introducing surface oxygen-containing groups

Activated carbon supported rhodium (Rh/AC) catalysts with different amounts of oxygen-containing functional groups were prepared by nitric acid (HNO3) treatment at varied temperatures. Thermal analyses of Rh/AC catalysts with or without this acidic treatment were characterized by thermogravimetric analysis (TGA) and temperature programmed desorption (TPD). The change of surface oxygen-containing functional groups was characterized by Fourier transform infrared spectrometry (FTIR) and X-ray photoelectron spectroscopy (XPS). These characterization results indicated that the amount of oxygen-containing functional groups increased with the treatment temperature. The influence of these oxygen-containing functional groups on the products selectivities in heterogeneous hydroformylation reaction was investigated in detail. These abundant functional groups were benefited to improve the selectivity of n-heptanal, resulting in higher n/i (normal to iso) ratio of heptanal. The Rh/AC catalyst being treated at 80°C had the highest n/i ratio of 2.3, due to the maximum amount of oxygen-containing functional groups, which was almost double to that of raw Rh/AC catalyst. Moreover, abundant functional groups on catalyst suppressed hydrogenation of hexene, decreasing the selectivity of hexane from 4.9% of raw Rh/AC to 0.2%. These findings disclosed that these oxygen-containing functional groups on catalysts played an extremely important role in improving the catalytic performance of heterogeneous hydroformylation reaction, providing a new viewpoint for the studies on heterogeneous hydroformylation.

Kinetics and mechanisms of homogeneous catalytic reactions. Part 14. Hydroformylation of 1-hexene with formaldehyde catalyzed by a cationic bis(diphosphine)rhodium complex

Complex [Rh(κ2-P,P-dppe)2]acac ([1a]acac, dppe: 1,2-bis(diphenylphosphino)ethane) showed to be a highly efficient precatalyst for the hydroformylation of 1-hexene with formaldehyde under relatively mild reaction conditions (353–403K) in 1,4-dioxane as the solvent; the corresponding C7 aldehydes were obtained in linear to branched ratios (l/b) close to 2. A kinetic study for this reaction lead to the experimentally determined rate law: ri={K1k2/(1+K1[CH2O])}[Rh][C6H12][CH2O] [K1=(1.47±0.04)M−1 and k2=(0.47±0.01)M−1s−1 at 373K). The experimental activation parameters for the overall reaction were also calculated [Ea=(20.1±0.9)kcalmol−1, ΔH≠=(19.5±0.9)kcalmol−1, ΔS≠=(−9.3±0.5)calK−1mol−1 and ΔG≠=(22±2)kcalmol−1]. The kinetic study together with results on coordination chemistry performed with 1a and with the BF4 salt of its iridium analogue, [Ir(κ2-P,P-dppe)2]BF4 ([1b]BF4), as well as theoretical DFT-calculations allowed us to propose a mechanism for this reaction. The catalytic cycle involves the reversible oxidative addition of formaldehyde to 1a to yield [Rh(H)(CHO)(κ2-P,P-dppe)2]+, followed by the insertion of the olefin into the Rh-H bond to generate [Rh(alkyl)(CHO)(κ2-P,P-dppe)2]+, which is considered as the rds of the process [Ea2=(23.9±0.8) kcalmol−1]; the cycle is completed by the reductive elimination of the aldehydes to regenerate 1a and restart the cycle.

Biphase hydroformylation catalyzed by rhodium in combination with a water-soluble pyridyl-triazole ligand

[RhCl(COD)]2 in combination with a water soluble sulphonated pyridyl-triazolyl N,N-bidentate ligand efficiently catalyzes styrene and 1-hexene hydroformylation in water/organic solvent biphasic systems. The catalyst displays a good activity affording mixtures of linear and branched aldehydes with complete chemoselectivity. The aqueous catalytic phase may be recycled four times giving complete substrate conversion by 18h. Mercury-poisoning experiments and transmission electron microscopy indicate that, after the first catalytic run, rhodium is present in the aqueous phase in nanoparticle form.