Supported Liquid Phase Catalysts Research Articles

Extraction of rhodium from supported liquid-phase hydroformylation catalysts with supercritical carbon dioxide

The continuous extraction of the rhodium inventory in supported liquid-phase (SLP) catalytic materials utilized in the hydroformylation (HyFo) of 1-butene was investigated by supercritical carbon dioxide (scCO2). Optimization of extraction efficiency involved varying parameters such as temperature (90 and 120 °C), pressure (10, 20 and 30 MPa), and the addition of methanol as a polar co-feed to the extraction medium (0–20 vol%). The results underscored the critical role of methanol in facilitating extraction, as experiments employing pure scCO2 yielded no rhodium recovery. Furthermore, extraction performance demonstrated sensitivity to temperature and pressure adjustments during the process. Notably, the use of 10 vol% methanol at 120 °C and 30 MPa achieved complete rhodium extraction from the grained SLP materials, which was identified as the optimum extraction condition. This study highlights the potential for scaling up in-situ rhodium extraction processes within HyFo production plants based on SLP catalysts, emphasizing significant implications for industrial applications.

Rational solvent selection for the preparation of industrial monolithic supported liquid-phase (SLP) olefin hydroformylation catalyst

Heterogenisation of the hydroformylation (HyFo) process converting C4 olefins and syngas (CO/H2) to n-pentanal can substantially reduce its carbon footprint by simplifying downstream processing. Current upscaling efforts include constructing a pilot plant containing a Rh-diphosphite-stabilized supported liquid-phase (SLP) catalyst. The air-sensitive nature of the catalyst requires in-situ impregnation of the porous support material with the liquid phase components (Rh-precursor, ligand, stabiliser) entailing the use of large quantities of an organic solvent. Environment, health, and safety (EHS) as well as regulatory aspects prompt the search for an alternative to dichloromethane (DCM), which was used as standard solvent for lab-scale studies. To obtain alternatives to DCM, the replacement solvent methyl tert-butyl ether (MTBE) and in-silico screening of more than 5000 solvent candidates has been performed covering boiling points and solubility predictions by COSMO-RS as well as carcinogenicity- and mutagenicity predictions by quantitative structure–activity relationship (QSAR) models. The final list of solvent candidates contained unsaturated compounds (alkenes, alkynes) in addition to ether- and ester-functionalized​ solvents, which are typically recommended as DCM replacements. Sufficiently high solubilities of ligand and stabiliser to prepare the desired SLP catalyst were experimentally determined in the following solvents: methyl propionate (MP), dimethoxymethane (DMM), MTBE, tetrahydrofuran (THF) and DCM for benchmarking, and a monolithic SLP catalyst prepared with MTBE demonstrated to perform equally well in the HyFo reaction of 1-butene as the benchmark catalyst prepared using DCM solvent. Overall, the study demonstrates a practical approach for selecting solvents with a greener profile for making catalyst systems applicable for large-scale production.

Influence of Support Structure on Catalytic Performance of Supported Liquid-Phase (SLP) Catalysts in Hydroformylation of 1-Butene

Several supported liquid-phase (SLP) catalysts with immobilized Rh-biphephos complexes on monolithic supports were prepared and applied for continuous gas-phase hydroformylation (HyFo) of 1-butene. The support comprised macroporous monolithic silicon carbide (SiC) with deposited silica nanoparticles (NPs) in order to provide mesopores with enhanced capillary forces to retain the liquid-phase. Variable parameters were examined for the monolithic SiC supports, including size and loading of deposited silica NPs and intermediate calcination between silica deposition steps to obtain the most efficient support configuration for the SLP system. The SLP catalysts with larger deposited silica NPs gave higher catalytic activity (i.e. 1-butene conversion and turnover frequency) compared to the supports with smaller sized silica NPs. However, the selectivity towards the preferred linear aldehyde was higher in the SLP catalysts with supports containing less silica with small silica NPs. Importantly, the prepared SLP catalyst systems showed long-term stability in HyFo with negligible formation of high boiling aldol condensation products.

B2O3@BPO4 sandwich-like hollow spheres as metal-free supported liquid-phase catalysts

Supported liquid-phase catalysts (SLPCs) combine the advantages of homogenous liquid-phase catalysts and heterogeneous catalysis (e.g., controllability of active centers and efficient product–catalyst separation). Generally, SLPCs manifest as a liquid-phase catalyst film or droplet adsorbed onto the surface of a porous support, such as ionic liquid-phase catalysts. Here, we extend this idea and develop a solvent-free liquid-phase catalyst supported on hollow spheres. We report sandwich-like B2O3@BPO4 hollow spheres synthesized through a one-step template-free method. At reaction temperatures (>450 °C), melted B2O3 supported on the surface of BPO4 hollow spheres acts as a catalytically active species for the selective oxidative dehydrogenation of propane to propene, with an excellent productivity of 0.79 gC3H6 gcat−1 h−1 and a high stability at 550 °C. We also found a phenomenon of tertiary aggregation during the formation of this sandwich-like hollow sphere. Additionally, the kinetic experiments indicate oxygen activation on the B2O3@BPO4 surface and second-order rate dependence with respect to the partial pressure of propane. This work may open a new avenue for the design and construction of metal-free oxides used as high-temperature SLPCs.

Trimerization and tetramerization of ethylene in continuous gas-phase reaction using a Cr-based supported liquid phase catalyst

Selective tri- and tetramerization of ethylene in continuous operation was achieved by immobilization of the homogeneous chromium catalyst plus MAO co-catalyst in a thin film of high boiling hydrocarbons.

ChemInform Abstract: Unlocking the Potential of Supported Liquid Phase Catalysts with Supercritical Fluids: Low Temperature Continuous Flow Catalysis with Integrated Product Separation

AbstractReview: 198 refs.

Unlocking the potential of supported liquid phase catalysts with supercritical fluids: low temperature continuous flow catalysis with integrated product separation.

Solution-phase catalysis using molecular transition metal complexes is an extremely powerful tool for chemical synthesis and a key technology for sustainable manufacturing. However, as the reaction complexity and thermal sensitivity of the catalytic system increase, engineering challenges associated with product separation and catalyst recovery can override the value of the product. This persistent downstream issue often renders industrial exploitation of homogeneous catalysis uneconomical despite impressive batch performance of the catalyst. In this regard, continuous-flow systems that allow steady-state homogeneous turnover in a stationary liquid phase while at the same time effecting integrated product separation at mild process temperatures represent a particularly attractive scenario. While continuous-flow processing is a standard procedure for large volume manufacturing, capitalizing on its potential in the realm of the molecular complexity of organic synthesis is still an emerging area that requires innovative solutions. Here we highlight some recent developments which have succeeded in realizing such systems by the combination of near- and supercritical fluids with homogeneous catalysts in supported liquid phases. The cases discussed exemplify how all three levels of continuous-flow homogeneous catalysis (catalyst system, separation strategy, process scheme) must be matched to locate viable process conditions.

Supported Liquid Phase Catalyst coating in micro flow Mizoroki–Heck reaction

A Supported Liquid Phase Catalyst (SLPC) coating was successfully applied for the Mizoroki–Heck reaction in micro flow. Foremost, extended on stream operation was enabled and the on stream performance stability was verified. Stable catalytic activity was achieved during two consecutive runs totaling 50h, after an initial stabilization period. Further support for the catalytic stability was provided by the fact that no leached Pd was detected in the product. Highest obtained conversion was 94% at 230°C and a 26min residence time. When conversion was plotted versus residence time, the reaction was shown to fit the predictions of the kinetic model. To optimize the performance of the flow system, reaction conditions and different ligands for the catalyst were initially investigated in batch, as well as various different substrates. Ethylene glycol was found to be most effective as the solvent film, while the use of water led to degradation of the silica support.

ChemInform Abstract: Immobilized Functional Ionic Liquids: Efficient, Green, and Reusable Catalysts

AbstractReview: 205 refs.

Immobilized functional ionic liquids: efficient, green, and reusable catalysts

Ionic liquids (ILs) which are made up of cationic and anionic components can be designed to possess a definite set of properties. In this context, the term “designer solvents” has been used to demonstrate the potential of these environment-friendly ionic liquids in chemical reactions. Since these liquids are able to dissolve several transition metal complexes, they have often been employed in recent times in several catalytic reactions to enhance reaction rates and selectivities. The concept of “immobilized” liquids has been derived from supported liquid phase catalysts; the immobilization process transferring the desired catalytic properties of the liquids to solid catalysts could combine the advantages of ILs with those of heterogeneous support materials and various catalytically functional groups or active species. The immobilized functional ionic liquids (IFILs) capable to restrict many of the negative effects of the conventional ILs have successfully been used in various potent catalytic areas affording high catalytic activity. In this review, structural characteristics, properties and preparation of immobilized functional ionic liquids have been described and the results are compared with those of traditional ILs. Special emphasis has been paid to comprehend the mechanism of various catalytic processes using immobilized ionic liquids functionalized by different groups.

Developments and Applications of Supported Liquid‐Phase Catalysts

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Synthesis of cyclic carbonates from carbon dioxide and epoxides using alkali metal halide supported liquid phase catalyst

Supported liquid phase catalysts (SLPC) were prepared from high surface area porous silica, polyethylene glycol (PEG), alkali metal halides and used for the synthesis of cyclic carbonates from carbon dioxide and epoxides. These catalysts was found to be highly active and selective for the synthesis of cyclic carbonates. The catalytic activity strongly depends on the nature of the supported alkali metal halide. The amount of alkali metal salt incorporated in the catalyst is one of the most important factor governing the catalytic performance. Effect of various reaction parameters such as pressure, temperature, catalyst loading, surface area of support was also studied in detail.

A comparative study of supported aqueous- and ethylene glycol-phase catalysts in stilbene hydrogenation: Influence of the different modes of dispersion of supported liquids

Supported liquid phase catalysts (SLPC) containing water-soluble Pd complexes were used for hydrogenation of stilbene in toluene. When water is loaded on a silica gel support, the catalytic activity of SLPC increases with the amount of the water. In contrast, when ethylene glycol (EG) is used as the supported liquid, the activity does not depend on the amount of EG loaded. These results can be explained by differences in the mode of dispersion of the supported liquids over the support.

Developments and Applications of Supported Liquid Phase Catalysts

Supported liquid phase catalyst (SLPC) is one of effectively heterogenized homogeneous catalysts using organometallic complexes as active components, which are dissolved in a small quantity of liquid phase dispersed in the form of isle or film on the surface of supports. The SLPC has successfully been applied for several chemical transformations and this article will review recent results with respect to the preparation and catalytic performance, the applicability to continuous flow operations, and the capability of multifunctional catalysis. Keywords: One-pot hydrogenation, cinnamaldehyde, Heck reaction, Hydroformylation, toluene

Cyclohexene Reactivity over Palladium Acetate Supported in Liquid Phase

The competitive reactions of cyclohexene: disproportionation and dehydrogenation were studied over a supported-liquid phase catalyst (SLPC) of palladium acetate solved in a stationary phase employing two different techniques: pulsed and flow micro-reactor, where the products of reaction are analysed by gas chromatography. The effect of the liquid phase (comparing an aliphatic phase, squalane, with a polar phase, Triton), the reaction environment (comparing He, N2 and air) and the process conditions (temperature and reactant concentration) have been studied. Although continuous deactivation was observed in all the cases, the catalyst supported on the apolar phase presents better performance, whereas the disproportionation reaction only takes place at no oxidant conditions and the operation conditions only affect to the selectivity of the reaction. A kinetic model for the reaction, taking into account the catalyst deactivation has been proposed, and kinetic and deactivation constant were calculated by fitting the model to the experimental data. Arrhenius parameters were obtained from measured data at several temperatures.

Supported liquid-phase catalysts containing ruthenium complexes for selective hydrogenation of α, β-unsaturated aldehyde: importance of interfaces between liquid film, solvent, and support for the control of product selectivity

Selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) has been investigated with supported liquid-phase catalysts (SLPC), which contain Ru–TPPTS complexes in water film supported on a porous silica gel, in organic solvent (toluene). It was shown that COL can be mainly produced with small quantities of hydrocinnamaldehyde (HCAL) and hydrocinnamyl alcohol (HCOL). The influence of various reaction and catalyst preparation parameters on the overall rate of reaction and the product selectivity have been examined. In addition, liquid-phase adsorption of CAL on water-loaded silica samples has also been measured. It is believed that the hydrogenation of CAL to COL occurs at the interface between the water film and the organic solvent while that to HCAL at the interface between silica, water, and toluene. The hydrophilic nature of the CO bond of CAL is significant for the selective formation of COL at the water/toluene interface, to which polar CO bonds of CAL molecules are pointing. The product, COL, also has a polar OH group, and so it is difficult for COL to be hydrogenated to HCOL at this interface. At the other silica/water/toluene interface, CAL molecules may be adsorbed with their CC bonds as well, which enables the hydrogenation to HCAL. On recycling of SLPC, its activity and COL selectivity decrease. Both oxygen dissolved in toluene and change of active Ru complexes in the water film are responsible for the decrease of catalytic activity, and the change of the state of dispersion of the water film is significant for the decrease of COL selectivity.

Simultaneous application of two or more supported liquid-phase organometallic catalysts: heterogeneous multifunctional reaction systems

Using the form of supported liquid-phase catalysts, two or more homogeneous catalysts can simultaneously be used with retaining their own activities and taking the advantage of catalyst–product separation and catalyst recycling.

Increasing yield and operating time of SLP-catalyst processes by flow reversal and instationary operation

The paper presents a method how to avoid a drawback of supported liquid-phase catalysts (SLPC), namely the vapourisation of the solvent of the catalyst. This problem is overcome by reversal flow and adsorbing beds on both sides of the catalytic bed. Furthermore, a considerable increase in the yield of a hydroformylation reaction by means of an SLPC under instationary operation could be achieved.

Heck reaction with a silica-supported Pd-TPPTS liquid phase catalyst: effects of reaction conditions and various amines on the reaction rate

Supported liquid phase catalysts (SLPC) were prepared using a porous silica, ethylene glycol (EG), and triphenylphosphine trisulfonate sodium salt (TPPTS) and used for the Heck reaction of iodobenzene (PhI) and butyl acrylate (BA) in the presence of amine. The reaction rate depends on the concentration of Pd-TPPTS complex in the supported EG phase, not on the total quantity of Pd-TPPTS. The rate increases linearly with the PhI concentration. The reaction rate also increases linearly with the concentrations of BA and triethylamine (Et 3N) when these are low. However, a plateau and a maximum of the rate are seen with further increasing the concentrations of BA and Et 3N, respectively. As a result of the complex of these modes of the dependence, the reaction rate increases with the total concentration of PhI, BA and Et 3N in an order of two. The dependence of the reaction rate on those concentrations with a palladium-triphenylphosphine (Pd-TPP) homogeneous catalyst is quite similar to that with SLPC. The reaction rate depends also on the type of the amine used. Tributylamine (Bu 3N) gives faster reaction rates than Et 3N with both SLPC and Pd-TPP. However, such an effect of trihexylamine (Hex 3N) is seen only with Pd-TPP. In the SLPC system, Hex 3N gives almost the same rate as that with Et 3N. Promotive effect of recycle use of the SLPC sample is also affected by the type of the amine.

A novel catalyst containing a platinum complex in polyethylene glycol medium supported on silica gel for vapor-phase hydrosilylation of acetylene with trichlorosilane or trimethoxysilane.

Hydrosilylation of acetylene with trichlorosilane or trimethoxysilane was carried out using a vapor-phase flow reactor with use of tetraammineplatinum(II) chloride in polyethylene glycol medium supported on silica gel as a catalyst, which is an active and thermally stable supported liquid-phase catalyst prepared readily from easily available materials, tetraammineplatinum(II) chloride, polyethylene glycol and silica gel.