Biphasic Hydroformylation Research Articles

The role of cyclodextrins in the acceleration of the reaction rate in a biphasic hydroformylations

Water based biphasic hydroformylation assisted by cyclodextrins is known for enhanced reaction rates in comparison to the non-assisted biphasic hydroformylation. In this paper, the liquid–liquid interface of the hydroformylation of 1–octene, enhanced by randomly methylated-β cyclodextrins (RAME-β cyclodextrins), was examined for the first time using an in-situ image-based boroscopic technology. This technique enables the observation of the liquid–liquid interfacial area (aLL) during the reaction and under reaction conditions, facilitating an explicit analysis of the droplet population.In this study defined mixtures of the reaction components with RAME-β cyclodextrins increased the aLL by 84 %. A kinetic study showed that RAME-β cyclodextrins reduce the rate limiting effect of the nonanal concentration in the two phasic water/octene system on the interphase. The kinetic expression shows consequently higher reaction rates for this three-phase conversion, leading to a 387 % increase in aldehyde yield. When comparing four different amounts of RAME-β cyclodextrins (nCD:nRh(acac)(CO)2 = 0 / 12:1 / 24:1 / 50:1), we observed a decreasing dependency of the reaction rates on the conversion progress and therefore on the nonanal formation for higher cyclodextrin concentrations. A recovery test of the aqueous phase involving nonanal and 1-octene reveals a drastically increased concentration of 1029 % 1-octene (coctene = 1.08 10-3 mg mg−1) and 13676 % nonanal (cnonanal = 14.41 10–3 mg mg−1) after the addition of 0.002 mol RAME–β cyclodextrins. These findings affirm that RAME-β cyclodextrins primarily remove nonanal from the interfacial region while facilitating an increased availability of 1-octene for the surface bound reaction.

Towards more efficient hydroformylation of long‐chain alkenes in aqueous biphasic system using microbubbles

AbstractMicrobubbles were applied for the first time to enhance the aqueous biphasic hydroformylation of long‐chain alkenes. The gas–liquid–liquid multiphase hydroformylation was carried out using 1‐dodecene as model higher olefin and dihexadecyl dimethyl ammonium bromide (DDAB) as surfactant. The increasing liquid temperature resulted in the increased mean bubble size and total bubble number, but this trend became inapparent at high temperatures due to the reduced liquid viscosity. The increasing gas flow rate was favorable to increase the multiphase interfacial area, thus leading to the increasing mass transfer coefficient KLa. The conversion of 1‐dodecene reached maximum 95% in the three‐phase microemulsion system, and at a gas flow rate of 40 ml min−1. Further increasing the gas flow rate to 80 ml min−1 decreased the conversion, which was attributed to the destroyed flow field, as observed in micro‐PIV. Owing to the increased multiphase mass transfer efficiency, the application of microbubbles allowed to intensify the hydroformylation reaction with reduced reaction pressure, higher chemoselectivity, and increased turnover frequency (TOF).

Effect of Liquid–Liquid Interfacial Area on Biphasic Catalysis Exemplified by Hydroformylation

Biphasic catalysis enables the effective recycling of homogeneous catalysts by their immobilization in an additional liquid phase immiscible with the products. The introduced liquid–liquid interfacial area implies mass transfer limitations that play an important role in understanding these catalytic systems, with many rate enhancement strategies revolving around optimizing said area. In this contribution, the relationship between liquid–liquid interfacial area and catalytic activity is elucidated by applying a methodology that utilizes an image-based in situ measurement of the transient droplet size distribution. When the industrially highly relevant aqueous biphasic hydroformylation of the long-chain olefin 1-octene is taken as the model reaction, it is found that the product nonanal and the addition of the ligand increases the interfacial area by a factor of up to 5. The rate of conversion is found to depend on the stirring speed. By variation of the catalyst concentration, it is shown that an accumulation of the catalyst species at the interface is unlikely. Using a mathematical model, it is highlighted that the effect of the aqueous–organic interfacial area on the catalytic activity is not linear as was previously assumed in the literature. Instead, a change in the interfacial composition is proposed that causes a shift in the dependence of catalytic activity on said area. Thus, the dynamic physical properties of a lean gas–liquid–liquid system were linked to the catalytic performance of the system.

Monometallic and bimetallic sulfonated Rh(I) complexes: Synthesis and evaluation as recyclable hydroformylation catalysts

The synthesis of two water-soluble Rh(I) complexes, a disulfonated diimine mononuclear complex and a tetrasulfonated tetraimine binuclear complex, is reported. The reaction of the N,N-donor ligands containing the sulfonated alkyl substituents with [Rh(COD)(MeCN)2]BF4 led to the formation of the corresponding water-soluble Rh(I) complexes. The complexes were fully characterised using an array of analytical techniques such as NMR, infrared spectroscopy and mass spectrometry. The complexes were evaluated as catalyst precursors in the aqueous biphasic hydroformylation of 1-octene. Both catalyst precursors are highly active as hydroformylation precatalysts showing high conversions of 1-octene and good aldehyde chemoselectivity with no hydrogenation products (alkanes or alcohols) observed. The binuclear complex gave higher quantitative conversions compared to the mononuclear rhodium complex. Additionally, the catalysts were recovered by phase separation and reused over four catalytic runs, notably with a significant drop in conversion after each cycle.

Aqueous olefin hydroformylation using water-soluble mono- and trinuclear N,O-chelate rhodium(I)-aryl ether precatalysts

Water-soluble, sulfonated, salicylaldiminato-aryl ether mono- (7) and trimeric (8) ligands were prepared and reacted with the [Rh(μ-Cl)(η2:η2−COD)]2 dimer to yield the corresponding water-soluble mononuclear (9) and trinuclear (10) Rh(I) complexes. These rhodium complexes were evaluated and are active as catalyst precursors in the aqueous biphasic hydroformylation of 1-octene and styrene. Optimal conditions were realised, using 1-octene as a model substrate, at 85 °C and a syngas pressure of 50 bar, where the best activity and chemoselectivity for aldehydes was obtained. Catalyst recycling was successfully conducted over 5 cycles in a biphasic medium, with a gradual loss in catalytic performance for both complexes. However, the dendrimer-stabilised trinuclear precatalyst (10) showed improved recyclability during “neat”, aqueous monophasic hydroformylation experiments, while the mononuclear precatalyst (9) showed a reduced overall performance. Both precatalysts showed sustained catalytic activity (> 450 h−1) and a total bias towards aldehyde chemoselectivity during the aqueous biphasic hydroformylation of styrene.

Continuous hydroformylation of 1-decene in an aqueous biphasic system enabled by methylated cyclodextrins

Long-term applications of cyclodextrins in the aqueous biphasic hydroformylation of higher olefins with high selectivities and simultaneous catalyst recycling.

Improving Aqueous Biphasic Hydroformylation of Unsaturated Oleochemicals Using a Jet‐Loop‐Reactor

AbstractIn two case studies, the reaction performance of the aqueous biphasic hydroformylation of two industrially relevant oleochemicals, namely methyl 10‐undecenoate (case 1) and methyl oleate (case 2), is significantly improved by the use of a Jet‐Loop Reactor concept. Based on previously reported studies, only the two green and benign co‐solvents, 1‐butanol and isopropanol are applied, respectively, in the absence of any additional auxiliary. Both reactions benefit highly from using this special piece of equipment, specifically designed for improving gas–liquid–liquid mixing to create large interfacial areas with no moving internals. In case 1, the loading of the co‐solvent 1‐butanol is successfully reduced. For the first time significant yields (>40% after 1 h) are obtained in the absence of any co‐solvent, which is very beneficial, since aldehyde products and substrate form a pure product phase enabling straightforward separation. In case 2, the loading of the substrate methyl oleate is successfully increased from 6 to 30 wt% still showing satisfying productivity. At 15 wt%, the yield of the desired internal aldehydes in the jet‐loop reactor is increased by a factor of five compared to a stirred tank reactor after 3 h.Practical Applications: The production of aldehydes from hydroformylation of olefins is highly relevant for the chemical industry, since these can undergo numerous subsequent reactions, to form for instance alcohols, amines, and carboxylic acids. Generally, aldehydes from oleochemicals can serve as platform chemicals for gaining access to bifunctional molecules, which are interesting as polymer precursors. Performing hydroformylation with a water‐based solvent system enables efficient product separation from the aqueous catalyst phase for the realzation of more sustainable processes. By using the Jet‐Loop Reactor, the performance of the reaction system can be greatly improved addressing its practical relevance.

Improvement of Productivity for Aqueous Biphasic Hydroformylation of Methyl 10‐Undecenoate: A Detailed Phase Investigation

AbstractThe overall productivity of the aqueous biphasic hydroformylation of the castor oil‐derived methyl 10‐undecenoate is increased. To increase the reaction rate, the miscibility of water and the fatty compound is increased by addition of the green solvent 1‐butanol as co‐solvent. For the first time, the concentration of solvents, substrate, and product within the reaction process is experimentally examined in a biphasic system under 20 bar pressure of synthesis gas and 140 °C. A reactor to get samples of both phases is developed to determine the quarternary mixture of the reaction system presented in a four‐dimensional tetrahedron diagram. With the knowledge gained about the reaction and its drivers, it is possible to increase the efficiency of the reaction process reported so far. With simultaneously high reaction rates (turn over frequency = >5000 h−1), the space–time yield of the reaction reaches values of >120 g L−1h−1 and can be improved significantly without negatively affecting catalyst leaching.Practical Applications: Most polymers are made of petrochemicals. Here, the development of a highly efficient process for the formation of bifunctional molecules starting from technical grade methyl 10‐undecenoate made from castor oil in an aqueous biphasic reaction system is presented. By rhodium catalyzed hydroformylation, an aldehyde ester is formed which can be used to create alcohols, carboxylic acids, and amines. Subsequently, these molecules can be used as polymer precursors in polycondensation reactions.

Rhodium(I) metallacycles based on alkylated-PTA scaffolds: Synthesis and evaluation as hydroformylation catalyst precursors

A series of rhodium(I) metallacycles based on alkylated PTA complexes were synthesised and fully characterised using a range of spectroscopic and analytical techniques. These mononuclear Rh(I) complexes were evaluated in the aqueous biphasic (water-toluene) hydroformylation of 1-octene, showing chemoselectivity to aldehydes.

Utilization of deep eutectic solvents based on choline chloride in the biphasic hydroformylation of 1-decene with rhodium complexes

The hydroformylation of 1-decene was conducted in a gas-liquid-liquid system featuring a deep eutectic solvent to enable recycling of the noble metal catalyst. Operation using different phosphine-based ligands was analyzed (Biphephos, Sulfoxantphos and TPPMS) testing five deep eutectic solvents (DES) as polar phases. These were based on choline chloride (ChCl) as hydrogen bond acceptor with glycerol (Gly), ethylene glycol, glycerol carbonate, 1,2-propanediol and urea (U) as hydrogen bond donors, all of renewable origin. Screening of DESs and ligands was made reutilizing the best, being ChCl:U, ChCl:Gly and again ChCl:U the best performing media using Biphephos, Sulfoxantphos and TPPMS, respectively.

Water‐Soluble, Disulfonated alpha‐Diimine Rhodium(I) Complexes: Synthesis, Characterisation and Application as Catalyst Precursors in the Hydroformylation of 1‐Octene

The synthesis and characterisation of two new water‐soluble RhI mononuclear 1,4‐diazabutadiene (DADs) complexes of general formula: [Rh(DADs‐R)(COD)], where (DADs = sulfonated‐tagged–1,4‐diazabutadiene, COD = cyclooctadiene; and R = H or C10H8), are described. The rhodium(I) complexes were obtained via a complexation reaction of [Rh(COD)(MeCN)2]BF4 with the sulfonated α‐diimine (DAD) ligands, which were previously obtained from a Schiff base condensation reaction of 4‐aminophenol with either 1,2‐ethanedione or acenapthenequinone. All rhodium complexes and their precursor ligands were characterised using 1H NMR, 13C NMR, FT‐IR spectroscopy and mass spectrometry. Their performance as catalyst precursors in the hydroformylation of 1‐octene was assessed and compared to those of the non‐sulfonated RhI mononuclear 1,4‐diazabutadiene (DAD) complexes. Utilisation of the water soluble [Rh(DADs‐R)(COD)] lead to high conversions and regioselectivity (linear/branched aldehyde ratio) in the aqueous biphasic hydroformylation of 1‐octene. Additionally, the catalysts were recovered by phase separation and are reusable over four consecutive catalytic runs without significant loss in catalytic activity.

An Approach to Chemical Reaction Engineering and Process Intensification for the Lean Aqueous Hydroformylation Using a Jet Loop Reactor

AbstractThe biphasic hydroformylation of 1‐octene using a lean aqueous phase as solvent phase for catalyst recycling is discussed here. The gas‐liquid‐liquid reaction was homogeneously catalyzed by industrial standard catalytic system with [Rh(cod)Cl]2 as precursor and TPPTS as ligand. This work summarizes investigations addressing different aspects of the reaction, where a procedural approach was followed to gain understanding of its nature, kinetics and interphase reactivity. Finally, the application of the jet loop reactor is analyzed as a means to intensify the reaction.

Encapsulated liquid nano-droplets for efficient and selective biphasic hydroformylation of long-chain alkenes

Rh-TPPTS aqueous droplets were confined within hollow nanospheres, leading to enhancements of catalytic activity and aldehyde selectivity in hydroformylation reactions.

Aqueous biphasic hydroformylation of olefins: From classical phosphine-containing systems to emerging strategies based on water-soluble nonphosphine ligands

ABSTRACTThis review provides an overview of recent developments in the area of aqueous biphasic hydroformylation of higher olefins using metal catalysts and surfactants, cosolvents, thermoregulated ligands, cyclodextrins, and most importantly emerging water-soluble nonphosphine ligands. Water-soluble phosphine ligands have been widely explored for aqueous biphasic hydroformylation; however, phosphines are generally expensive and are prone to oxidation hence the recent interest in exploring other ligands. Various approaches have been used to introduce hydrophilicity to the ligands. The catalytic activity of monometallic and heterobimetallic systems containing nonphosphine ligands in aqueous biphasic media is emphasized in this review.

Synthesis of Rh(I) alkylated-PTA complexes as catalyst precursors in the aqueous-biphasic hydroformylation of 1-octene

A series of mono- and multivalent phosphorus-based ligands was synthesised by the lower-rim benzylation of the water-soluble ligand, 1,3,5-triaza-7-phosphaadamantane (PTA). These ligands were used to prepare mono-, bi- and trinuclear Rh(I) complexes whose catalytic activity, product selectivity and recyclability were evaluated in the aqueous biphasic hydroformylation of 1-octene.

New water-soluble Schiff base ligands based on β-cyclodextrin for aqueous biphasic hydroformylation reaction

Abstract The synthesis of water-soluble rhodium(I) salicylaldiminato and salicylhydrazonic complexes has been achieved employing two preparative routes. Schiff base condensation between 6A-deoxy-6A-amino-β-CD or 6A-deoxy-6A-hydrazino-β-CD and 5-sodiosulfonato-2-hydroxybenzaldehyde (sulfonated salicylaldehyde) (1) or 5-sodiosulfonato-3-tert-butyl-2-hydroxybenzaldehyde (sulfonated t Bu-salicylaldehyde) (2) led to the formation of the corresponding imine or hydrazone ligands (3, 4, 5 and 6). Reaction of [Rh(COD)2 +BF4 −] with these new ligands in an alkaline solution formed the corresponding rhodium complexes quantitatively. These rhodium(I) complexes could also be prepared in one-pot by mixing, in stoichiometric proportions, the modified β-CDs with the sulfonated salicylaldehyde and with the rhodium precursor in an alkaline solution at room temperature. These rhodium complexes were applied as catalysts in the aqueous biphasic hydroformylation of 1-decene as a model reaction.

Nonaqueous Biphasic Hydroformylation of Long Chain Alkenes Catalyzed by Water Soluble Phosphine Rhodium Catalyst with Polyethylene Glycol Instead of Water

The application of polyethylene glycol (donated as PEG), as an environmentally benign solvent instead of water, in rhodium catalyzed hydroformylation of long chain alkenes by using water soluble phosphine BISBIS or TPPTS (TPPTS: sodium salt of sulfonated triphenylphosphine, BISBIS: sodium salt of sulfonated 2,2′-bis(diphenylphosphinomethyl)-1,1′-biphenyl) is herein reported. The conversion of long chain alkenes in PEG-200 could reach above 95.0% after a short reaction time (15 min). In addition, an efficient phase separation and recycling of PEG-200 and catalyst were achieved. The leaching of rhodium into product phase detected by ICP-AES was less than 0.06 wt% of the initial amount.

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%.

Considerations on film reactivity in the aqueous biphasic hydroformylation

In experiments and kinetic models it was shown that the reaction rate of the biphasic aqueous hydroformylation of 1‐octene is linear dependent on the created interfacial area. This phenomenon is directly linked to the question whether the reaction takes place in the bulk phase and is mass transfer limitation or at the surface which would mean an increase of reaction space. To evaluate the place of reaction a mass transfer analysis has been carried out. No mass transfer limitation for the gaseous components carbon monoxide and hydrogen as well as the olefin 1‐octene was determined for the aqueous catalyst phase by calculating the Hatta numbers. With this observation it is possible to exclude the mass transfer as a potential influence and hence the aqueous bulk as the place of reaction. Thus the reaction is most probably surface active. This can be either explained the increase in film volume fraction where non‐polar substrate as well as polar catalyst complex is present or through an increased catalyst concentration at the surface through dipole moment fluctuations. © 2017 American Institute of Chemical Engineers AIChE J, 63: 161–171, 2018

Highly regio-selective hydroformylation of biomass derived eugenol using aqueous biphasic Rh/TPPTS/CDs as a greener and recyclable catalyst

A Rh/TPPTS catalyzed aqueous biphasic hydroformylation of eugenol was performed in an aqueous medium in the presence of different modified cyclodextrins. The internal olefin such as anethole shows high selectivity towards the branched aldehydes (78%) where as terminal alkene like eugenol shows high selectivity towards the linear aldehydes (87%). The various reaction parameters such as effect of syngas pressure, time, temperature, catalyst precursor and loading have been studied. The high activity and high selectivity towards the linear aldehydes is due to the steric crowding of methyl group present in RAME-β-cyclodextrins. The effect of ratio of Rh/TPPTS/RAME-β-CD were also studied for the hydroformylation of eugenol. Moreover, this catalytic system was recycled up to four consecutive cycles without loss in its catalytic activity and selectivity.