Performance In Hydroformylation Research Articles

Influence of support on Rh-Co bimetallic catalysts for ethylene hydroformylation

Bimetallic Rh- and Co-based catalysts are promising materials for the heterogenous ethylene hydroformylation reaction. Here, the influence of a mesoporous silica (SBA-15) support on Rh and Co bimetallic interactions was investigated through a comparison with silica gel and gamma-alumina supports. The bimetallic catalyst supported on mesoporous silica (RhCo3/SBA-15) showed the best C3 oxygenate yield among the three bimetallic catalysts. In-situ vibrational studies suggested moderate binding of the gem-dicarbonyl and Rh(CO)(C2H4) intermediates due to this bimetallic interaction that led to improved hydroformylation performance. Kinetic studies revealed a lower hydroformylation barrier for the bimetallic compared to a Rh monometallic catalyst, and in-situ X-ray absorption spectroscopy investigations showed clear Rh-Co alloy formation on RhCo3/SBA-15. The bimetallic enhancement effect from the interaction with the mesoporous silica support shown here can be further optimized to design olefin hydroformylation catalysts.

Boosting the Hydroformylation Activity of a Rh/CeO2 Single-Atom Catalyst by Tuning Surface Deficiencies

Controlling the interactions between atomically dispersed metal atoms and the support plays significant roles in determining the activity and selectivity of single-atom catalysts. In this report, we tuned the local coordination environment of Rh single atoms on CeO2 via calcination to construct a highly active hydroformylation catalyst. Single-atom Rh/CeO2 calcined at a high temperature exhibits more oxygen vacancies, which lead to the formation of a large amount of low-coordination Rh active species that are more active for hydroformylation. Under the optimum conditions, the best Rh/CeO2 catalyst achieved a TOF at approximately 5000 h–1 with 100% aldehyde selectivity in propylene hydroformylation to butanal. In situ FTIR spectroscopy and in situ XPS characterizations provide strong evidence that Rh on 800 °C-calcined CeO2 is easily activated to form surface HRh(CO)2 active species, favoring propylene adsorption and CO insertion. This work highlights the significance of engineering metal–support interactions in tuning the hydroformylation performance of single-atom catalysts and contributes to mechanistic insights into single-atom Rh-catalyzed hydroformylation reactions.

Hydroformylation over polyoxometalates supported single-atom Rh catalysts

Atomic dispersion of Rh on phosphotungstic acid (PTA) salts was achieved by a self-assembled precipitation method using alkali metal ions as coprecipitation reagents. During styrene hydroformylation, the supported Rh single-atom catalyst (Rh1/M-PTA, M refers to an alkali metal ion) demonstrated an optimum turnover frequency (TOF) of 1076 h^-1. With increasing ionic radius, the pore size of the catalysts increased in the following order: Rh₁/K-PTA<Rh₁/Rb-PTA<Rh₁/Cs-PTA. The catalytic activity showed the same trend, suggesting a positive correlation between pore size and hydroformylation performance. Further experimental data suggested that temperature is an important factor affecting not only the activity but also the selectivity. This study enriches the understanding of the structure and catalytic properties of PTA-supported single-atom materials. The cation-controlled synthesis of catalysts may also be applied to prepare other single-atom catalysts with tunable pore size distributions.

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.

Enhanced hydroformylation of 1‐hexene in microbubble media

AbstractTo enhance the gas–liquid mass transfer in the hydroformylation reaction, microbubbles were applied into this typical gas–liquid reaction. Compared with a commercial tube microbubble generator, a fractal microbubble distributor, which was designed based on the bionic fractal theory and manufactured via 3D printing, permitted to increase the total microbubble number and decrease the microbubble size. Moreover, the microbubbles were more uniformly distributed in the reactor by the fractal distributor. The gas holdup and the gas–liquid mass transfer were much higher in microbubble system than those with millimeter bubbles. The microbubble status played an important role on the hydroformylation performance. With a close total aldehyde yield (90%), the introduction of microbubbles could reduce the hydroformylation reaction time from 120 min of the stirred batch reactor to 60 min owing to the enhanced mass transfer. The proposed microbubble mediated system also has great potential for intensifying the other gas–liquid reactions.

Hydroformylation of the post-metathesis product 7-tetradecene using rhodium(I) Schiff base derived precatalysts

The rhodium-catalysed hydroformylation of the post-metathesis product 7-tetradecene using aryl- (1) and ferrocenyl- (2) Schiff base derived precatalyst complexes was investigated. It was found that the reaction temperature (75–115 °C), pressure (30–60 bar, CO/H2 = 0.5–2) and 7-tetradecene-to-precatalyst molar ratio (1000:1–6000:1) had a significant influence on the hydroformylation performance. Turnover numbers up to 4310 were observed and the selectivity data show a temperature and pressure-dependent conversion of 7-tetradecene to the primary branched aldehyde product 2-hexylnonanal and isomeric branched aldehydes. A cooperative effect between rhodium and ferrocene was observed as hydroformylation performance results obtained with the heterobimetallic precatalysts (2) differ from that achieved using the monometallic catalyst system (1) under mild reaction conditions. Both precatalysts performed optimally at a temperature of around 95 °C. Lifetime studies with the precatalysts were conducted and the precatalysts were found to remain active over at least three consecutive reaction cycles.

Enhancement of hydroformylation performance via increasing the phosphine ligand concentration in porous organic polymer catalysts

The development of highly efficient and stable Rh-based heterogeneous catalysts for hydroformylation of heavier olefins is of both high fundamental and industrial interest, yet there still remains a tremendous challenge. In this contribution, a series of porous organic polymers bearing various concentrations of triphenylphosphine (PPh3) moieties, a ligand of industrial choice, was synthesized and their performance in the hydroformylation of styrene, 1-ocetene, and 2-ocetene were investigated after metalation with Rh species. Both concentration of PPh3 moieties and pore structure of the polymers were found to influence the catalytic performance. The polymer-based rhodium catalysts demonstrated an increase in catalytic activity, selectivity, and stability when the concentration of PPh3 was increased and the porous polymer constructed by the functional PPh3 monomer (POL-PPh3) was found to be optimal among all the solid ligands tested. We anticipate these results will form the basis for a constructive perspective in the development of high performance heterogeneous Rh-based hydroformylation catalysts. Moreover, our observations indicate the considerable potential of porous organic polymers (POPs) as a new generation of heterogeneous catalytic platforms that may prove effective when targeting important but highly challenging reactions.

Effect of lengthening alkyl spacer on hydroformylation performance of tethered-phosphine modified Rh/SiO2 catalyst

Rh/SiO2 catalysts with tethered-phosphines with different alkyl spacer lengths have been prepared, tested and characterized. Lengthening the alkyl spacer of the tethered-phosphine improved the flexibility of tethered-phospine, promoted the formation of active species and enhanced the activity of hydroformylation over other tethered-phosphine modified Rh/SiO2 catalysts.

Characterization and hydroformylation performance of mesoporous MCM-41-supported water-soluble Rh complex dissolved in ionic liquids

The TPPTS-Rh complex [TPPTS = trisodium salt of tri-( m-sulfophenyl)-phosphine, P( m-C 6H 4SO 3Na) 3], which was dissolved in the ionic liquids 1-butyl-3-methyl-imidazolium tetrafluoroborate (BMI⋅BF 4), 1-butyl-3-methyl-imidazolium hexafluorophosphate (BMI⋅PF 6), and 1,1,3,3-tetramethylguanidinium lactate (TMGL), was immobilized on MCM-41. The resulting supported ionic liquid-phase catalysts (SILPCs) were very active for the hydroformylation of higher olefins. The SILPCs with the regular hexagonal array of MCM-41 were structurally stable before and after the catalytic reaction, as characterized by XRD, N 2 adsorption/desorption, FTIR, 31P-NMR, SEM, HRTEM, and TGA-DSC. The obtained SILPCs showed higher catalytic activity, independent of IL type, as compared with their ionic liquid–organic biphasic counterparts and the one with SiO 2 as carrier. Such SILPCs could be reused several times without significant loss of activity or selectivity.

Active Carbon Supported Rhodium Catalyst in the Hydroformylation of 1-Hexene

Hydroformylation performance of 1-hexene over rhodium solid catalyst was studied under mild reac-tion condition (H2/CO=1/1, Pressure=3.0MPa, T=403K). Its hydroformylation activities were examined systematically in various solvents. Effects of operating variables on the CO conversion, yields of products and stability of the catalysts also have been discussed in detail. It was found that the rhodium catalyst exhibited the excellent activity in the n-octane solvent, while poor activity in the alcoholic and H2O solvent. Rh/active carbon (Rh/C) catalyst presented superior catalytic performances over Rh/SiO2 catalyst in the activity, selectivity and stability. As the most important, Rh/C catalyst showed stable activity in the continuous (olefin and synthesis gas) feeding system even in the low metal loading, giving the total turn over number (TON) of 500 during 14 hs reaction.

Aqueous phosphine–Rh complexes supported on non-porous fumed-silica nanoparticles for higher olefin hydroformylation

Non-porous fumed-silica nanoparticles were used as supports for the first time to immobilize water-soluble complex HRh(CO)(P( m-C 6H 4SO 3Na) 3 ( 1) [P( m-C 6H 4SO 3Na) 3, i.e. trisodium salt of tri-( m-sulfophenyl)-phosphine, TPPTS] to obtain supported aqueous-phase catalysts (SAPC) (fumed-SiO 2-SAPC) for hydroformylation of 1-hexene. The experimental results proved that the structure of support and the support hydration were the determining factors contributing to the hydroformylation performance. The fumed-SiO 2-SAPC where the water-soluble rhodium complexes were well dispersed onto the external surface of the silica nanoparticles presented a higher hydroformylation performance over a relatively wider range of support hydration as compared to the SAPC with conventional porous granular-SiO 2 support (porous SiO 2-SAPC). A positive effect on the reaction performance was observed from the particle size and surface area of the fumed-silica nanoparticles. The hydroformylation performance with fumed-SiO 2-SAPC was promoted by an addition of basic alkali metal salts such as Na 2CO 3, K 2CO 3, and NaH 2PO 4, which depressed the oxidation of ligand TPPTS to OTPPTS [OTPPTS, i.e. trisodium salt of tri-( m-sulfophenyl)-phosphine oxide, OP( m-C 6H 4SO 3Na) 3] as evidenced by 31 P NMR observation.

Structure aspects and hydroformylation performance of water-soluble HRh(CO)[P( m-C 6H 4SO 3Na) 3] 3 complex supported on SiO 2

The solution NMR ( 31 P and 1 H ) and FTIR spectroscopies were employed to investigate the structure information of water-soluble complex HRh(CO)[P( m-C 6H 4SO 3Na) 3] 3 ( 1) [P( m-C 6H 4SO 3Na) 3: trisodium salt of tri-( m-sulfophenyl)-phosphine, TPPTS] supported on SiO 2 ( 1/SiO 2). The 31 P ( 1 H ) NMR spectra showed that a pair of new twin-peak at about 31.5, 32.1 ppm while no typical twin-peak at 44.0, 44.7 ppm for the phosphorus species ascribed to the complex 1 were observed at 1/SiO 2. However, the typical phosphorus peaks for the complex 1 appeared in the case of using TPPTS or Na 2CO 3-preimpregnated SiO 2 as supports. Moreover, the immobilization caused a considerable oxidation of the liberated TPPTS to OTPPTS (OTPPTS, i.e. OP( m-C 6H 4SO 3Na) 3: trisodium salt of tri-( m-sulfophenyl)-phosphine oxide) species as evidenced by 31 P ( 1 H ) NMR spectroscopy. The phosphorus-31 peaks at 31.5, 32.1 ppm at 1/SiO 2 were found to be unchanged before and after the propene hydroformylation. The FTIR results revealed that the CO band appeared at about 1870 cm −1 for the 1/SiO 2 catalyst, which was lower than that for the precursor complex 1. It is concluded that there exists a strong interaction between the complex 1 and the acidic support of SiO 2, resulting in the deformation of the Rh–phosphine complex containing less than three TPPTS ligands, which further transformed by dehydrogenation and dimerization under evacuation to form a species likely [Rh(CO)(TPPTS) 2] 2 as a main surface complex species at the catalyst 1/SiO 2.

Chiral diphosphites derived from D-glucose: new ligands for the asymmetric catalytic hydroformylation of vinyl arenes.

A series of novel diphosphite ligands derived from readily available D-(+)-glucose has been synthesized. These ligands have been applied to the Rh-catalyzed hydroformylation of vinyl arenes. Both excellent enantioselectivities (up to 91%) and regioselectivities (up to 98.8%) were achieved under mild conditions. The advantage of these ligands is that their modular natures allow facile, systematic variation in the configurations at the stereocenters [C(3), C(5)] at the ligand bridge and in the biphenyl substituents, enabling their effects on the stereoselectivity to be studied. Results show that the absolute configuration of the product is governed by the configuration at the stereogenic center C(3), while the level of the enantioselectivity is influenced by a cooperative effect between stereocenters C(3) and C(5). Replacement of the tert-butyl substituent by methoxy substituents at the para positions of the biphenyl moieties improved the enantioselectivities. We have characterized the rhodium complexes formed under CO/H2 by NMR techniques and in situ IR spectroscopy and have observed that there is a relationship between the structure of the [HRh(CO)2(PP)] species and their enantiodiscriminating performance in hydroformylation. Enantioselectivities were highest with ligands with a strong bis-equatorial coordination preference, while an equilibrium of species with bis-equatorial and equatorial-axial coordination modes considerably reduced the ee's.

Structure and Hydroformylation Performance of Supported Aqueous-phase Rh Catalyst

Structure and Hydroformylation Performance of Supported Aqueous-phase Rh Catalyst