Supported Liquid Phase 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.

Supported liquid phase extraction using wetted nanofiber discs as a simple approach for in-vial extraction of chlorophenols and insecticides from river water prior to HPLC-DAD analysis

BackgroundA novel supported liquid extraction approach using small polymeric nanofibrous discs was demonstrated and applied to the analysis of real river water. Nanofibrous discs were tested to extract model mixture of 9 common water contaminants 4-nitrophenol, various chlorophenols, bisphenol A, permethrin, and fenoxycarb featuring a wide range of log P values (1.9–6.5). Polyacrylonitrile, polyhydroxybutyrate, and polylactic acid nanofibers were selected as adsorptive materials. One-step desorption was performed directly in HPLC vials, to avoid time-consuming evaporation and reconstitution steps. The discs were allowed to sediment to the bottom of the vial before injection into the chromatographic system. ResultsVarious parameters affecting the extraction efficiency including 1-octanol volume, extraction time, ionic strength, and sample volume were investigated and optimized. Wetting the nanofiber discs with 1-octanol resulted in up to 20-fold increase in enrichment factor when compared to non-wetted polymer counterparts. The highest enrichment factors were observed for analytes with a log P range of 3.3–4.5. Our developed method showed good linearity in the range 20–200 μg/L for all analytes tested. Satisfactory repeatability with RSD <13 % were achieved covering all steps including disc preparation, wetting, extraction/elution, and chromatography analysis, and recoveries ranged from 58.93 to 121.43 %. SignificanceThis work represents novel simple supported liquid extraction approach using impregnated polymer nanofiber discs. Using only 50 μL 1-octanol, we reduced the organic solvent compared to other extraction methods. There was no need for any plastic cartridge to hold the sorbent and direct in-vial desorption reduced the unnecessary, time-consuming steps and simplified the sample preparation protocol.

A Review of Synthetic Application of Homogeneous, Heterogenised‐Homogeneous, and Microwave‐Assisted Catalytic Carbonylation of Selected Substrates

AbstractCatalytic carbonylation has gained a lot of interest over the past 20 years. It produced various pharmaceuticals, agrochemicals, and intermediates that can made through this process. The carbonylation process is the most straightforward method to insert CO into any organic substrate using a simple carbonyl source, i. e., CO gas. Apart from gaseous CO, many techniques have devised for producing CO in situ using surrogates such as HCOOH, DMF, Formic acid, Phenyl Formate, Oxalic acid, and Chloroform. Several carbonylation methods, such as aminocarbonylation, alkoxycarbonylation, double carbonylation, and oxidative carbonylation, provide viable and appealing substitutes for conventional synthetic methods on a commercial or laboratory scale. Many recent studies focus on catalyst‐product separation, catalyst recoverability, and reusability in these reactions. Therefore, advancements in using different approaches, such as supported liquid phase catalysis and biphasic catalysis, to anchor homogeneous catalysts are becoming increasingly important. These carbonylation methods are easy to use, cost‐effective, and do not require ligands. They also produce excellent yields of the products necessary. Using phosphine ligands has drawbacks, including high work‐up costs, laborious work‐up techniques, and sensitivity to air and moisture. Several phosphine‐free carbonylation pathways offer affordable and straightforward ways to accomplish these changes without phosphine ligands. This review summarizes the synthetic application of homogeneous and immobilized catalysts in producing carboxylic acid derivatives and heterocycles that have medicinal properties.

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.

Silicon Carbide Supported Liquid Phase (SLP) Hydroformylation Catalysis – Effective Reaction Kinetics from Continuous Gas‐phase Operation

AbstractThe hydroformylation reaction is one of the most important applications of homogeneous catalysis on an industrial scale with worldwide production capacities exceeding 15 Mio tons per year. Efficient catalyst immobilization becomes mandatory for such large‐scale processes. In this work, a supported liquid phase (SLP)‐type catalyst on a silicon carbide support material was applied in the continuous Rh‐bpp (bpp=biphephos) catalyzed gas‐phase hydroformylation of but‐1‐ene. A parameter variation was carried out in the pressure range from 0.5 to 3.0 bara for but‐1‐ene, 0.5 to 5 bara for H2, 0.5 to 5 bara for CO, and in the temperature range from 90 to 125 °C. Activation energies were determined for the individual reactions showing a shift in activation energy most significantly for the hydroformylation to n‐pentanal for temperatures of 110 °C and above. For all substrates the effective reaction orders were calculated and employed in a power‐law rate model giving good agreement of measured and modeled data within a ±20 % error margin. Similar results were obtained using a microkinetic model.

Cover Feature: Oxygen‐Functionalized Boron Nitride for the Oxidative Dehydrogenation of Propane – The Case for Supported Liquid Phase Catalysis (ChemCatChem 8/2022)

The Cover Feature shows a hexagonal boron nitride plane. On top of the plane are liquid diborontrioxide droplets, which catalyze the oxidative dehydrogenation of propane. In their Research Article, P. Schmatz-Engert et al. explain that these melt films can be seen as the active phase in the boron catalyzed oxidative dehydrogenation of propane to propylene. Via in situ XRD analysis the authors were able to document the transformation process of oxygen functionalized hexagonal boron nitride to a supported liquid phase. In the upcoming research field of selective alkane oxidativedehydrogenation these results offers new opportunities for an innovative catalyst design. More information can be found in the Research Article by P. Schmatz-Engert et al.

Oxygen‐Functionalized Boron Nitride for the Oxidative Dehydrogenation of Propane – The Case for Supported Liquid Phase Catalysis

AbstractBoron and boron containing materials have created a new class of catalysts for the highly selective conversion of light alkanes to building block olefins. Boron oxide species seem to play an essential role for the oxidative dehydrogenation of propane. For boron nitride they are created through an induction process under reaction conditions. It is still not obvious how different kinds of oxidative pre‐activation influences the observed activity and selectivity. Here we compare two different oxygen activation strategies of boron nitride, a classical activation by calcination at different temperatures and ball‐milling with varying rotation velocity. These treatments allow to control the amount of introduced boron oxide species from 0.2 to 17.5 wt.‐%, as quantified by alkalimetric titration. The catalytic experimental data together with the pre, post as well as in situ characterization, give insights how the catalyst's surface changes under reaction conditions. On this backdrop it can be deduced that molten boron oxide predominantly acts as catalyst under reaction conditions, and boron nitride as catalyst support.

Gas drying using [EMIM][MeSO3] supported on silica gel in fixed-bed - study on process behavior, mass transport and modeling

Gas drying experiments in fixed-bed setup using a supported ionic liquid phase (SILP) material, here the ionic liquid (IL) [EMIM][MeSO3] coated on silica gel 150, revealed a high drying performance and dew points of less than −68 °C in the dried gas stream. For modeling, the linear driving force (LDF) approach was used. The mass transfer in pure silica gel and the coatings with (about) an IL monolayer can be described similarly to conventional adsorbents. For multilayers of IL, the behavior differs as the pores get filled with an IL/H2O mixture, reducing the volume fraction for transport in vapor/gas phase. Also, the composition of the supported liquid phase changes significantly. By fitting an equation that considers a linear decrease of the mass transport coefficient with increasing degree of total pore filling, kinetic parameters with high accuracy were gained. A scale-up simulation demonstrated that the favorable SILP material is able to dry about 80% more gas volume than a conventional drying agent, corroborating the high potential of this SILP system for gas drying.

Influence of support texture and reaction conditions on the accumulation and activity in the gas-phase aldol condensation ofn-pentanal on porous silica

Aldol condensation ofn-pentanal can lead to pore blocking and hence transport limitations in supported liquid phase (SLP) catalysts. By careful texture optimization this effect can be minimized.

Immobilized Ru‐Pincer Complexes for Continuous Gas‐Phase Low‐Temperature Methanol Reforming‐Improving the Activity by a Second Ru‐Complex and Variation of Hydroxide Additives

AbstractRu‐pincer complexes were immobilized as supported liquid phase (SLP) materials to allow the methanol reforming reaction as continuous gas phase process. Under reaction conditions, the liquid phase forms from the hydroxide coating. Several hydroxides were screened and CsOH showed highest activity compared to the standard KOH coating. The well‐known Ru‐pincer complex carbonylchlorohydrido [bis(2‐di‐i‐propylphosphinoethyl)amine]ruthenium(II) is limited in catalyzing the final step of the methanol reforming. Addition of a second complex, having a methylated backbone in the pincer‐ligand, could overcome these limitations. Significant enhancement of the overall catalytic activity was observed.

Capturing spatially resolved kinetic data and coking of Ga-Pt supported catalytically active liquid metal solutions during propane dehydrogenation in situ.

Supported liquid phase catalysis has great potential to unify the advantages from both homogeneous and heterogeneous catalysis. Recently, we reported supported catalytically active liquid metal solutions (SCALMS) as a new class of liquid phase catalysts. SCALMS enable high temperature application due to the high thermal stability of liquid metals when compared to supported molten salts or ionic liquids. The highly dynamic liquid metal/gas interface of SCALMS allows for catalysis over single atoms of an active metal atom within a matrix of liquid gallium. In the present study, kinetic data is acquired along the catalyst bed in a compact profile reactor during propane dehydrogenation (PDH) over gallium-platinum SCALMS. The reactor design allows for the analysis of the temperature and gas phase composition along the catalyst bed with a high spatial resolution using a sampling capillary inside the reactor. The concentration profiles suggest enhanced deactivation of the catalyst at the end of the bed with a deactivation front moving from the end to the beginning of the catalyst bed over time on stream. Only minor amounts of side products, formed via cracking of propane, were identified, supporting previously reported high selectivity of SCALMS during alkane dehydrogenation. The acquired data is supported by in situ high-resolution thermogravimetry coupled with mass spectrometry to monitor the activity and coking behaviour of SCALMS during PDH. The results strongly suggest an enhanced formation of coke over Al2O3-supported SCALMS when compared to using SiO2 as the support material.

Continuous gas-phase hydroformylation of but-1-ene in a membrane reactor by supported liquid-phase (SLP) catalysis

The development of a supported liquid phase (SLP) gas-phase hydroformylation catalyst combined with a monolithic membrane separation layer is reported.

Supported-liquid phase extraction in combination with isotope-dilution gas chromatography triple quadrupole tandem mass spectrometry for high-throughput quantitative analysis of polycyclic aromatic hydrocarbon metabolites in urine

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants with a number of them being carcinogenic. One of the approaches to assess human exposure to PAHs is to measure their urinary metabolites, monohydroxyl polycyclic aromatic hydrocarbons (OH-PAHs), with a method allowing for high throughput and short turn-around time. We developed a method to quantify nine urinary OH-PAHs by using supported liquid phase extraction (SLE) and isotope dilution gas chromatography tandem mass spectrometry (GC-MS/MS). SLE demonstrated advantages over the traditionally used liquid-liquid extraction techniques. The target analytes with spiked deuterated and 13C-labeled internal standards were extracted from urine by SLE after enzymatic cleavage of the glucuronide and sulfate conjugates. The extracted analytes were then derivatized with N-Methyl-N-(trimethylsilyl) trifluoroacetamide (MSTFA), and analyzed by GC-MS/MS. Six solvent mixtures were evaluated as the SLE extraction solvent, and pentane:chloroform (7:3, v/v) was selected due to its best overall analytical performance. Method detection limits for the 9 analytes ranged from 2.3 to 13.8 pg/mL. Precision and accuracy were satisfactory. SLE and internal isotope labeled standard combination reduced matrix effect effectively. This new method using SLE sample preparation techniques coupled with GC-MS/MS proves applicable to urinary measurements for PAH exposure studies for general population.

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.

Immobilization of a selective Ru-pincer complex for low temperature methanol reforming–Material and process improvements

Abstract A homogeneous Ru-pincer complex was immobilized by the supported liquid phase (SLP) technique and tested in continuous gas-phase steam reforming of methanol. Variations of catalyst composition (liquid phase, base and catalyst loading) as well as process parameters (temperature, flow rate) were carried out. High activity was obtained when ionic liquids were used for catalyst immobilization. However, better stability was obtained in the absence of ionic liquids using pure KOH.

Effect of a cyclic heating process on the CO 2 /N 2 separation performance and structure of a ceramic nanoporous membrane supporting the ionic liquid 1-methyl-3-octylimidazolium tricyanomethanide

This work presents an investigation of the CO2 and N2 mixed-gas permeation rates through a supported ionic liquid membrane (SILM) developed on a ceramic composite nanofiltration substrate with a separation layer pore size of 10 nm. The ionic liquid 1-methyl-3-octylimidazolium tricyanomethanide was used as supported liquid phase. The hybrid membrane was subjected to a cyclic heating process including isothermal steps of 180 °C, under inert gas flow. In this context, the effect of temperature (over the range of 25–180 °C) and feed composition on the permeation properties and CO2/N2 separation performance was studied prior to and after completion of each heating cycle. For all heating cycles, the highest CO2/N2 selectivity values (up to 50.4) were provided at ambient temperature unlike to CO2 permeance that was favored by elevation of temperature, reaching to 2.48 · 10−9 mol·m−2·s−1·Pa−1 at 180 °C. Thermal analysis by means of DSC and TGA investigations allowed to determine the physical state and thermal stability of the immobilized IL phase, thereby providing a better understanding of the determined gas permeation properties. Confinement into the nanopores of the developed SILM substantially affected the thermal behaviour and assisted decomposition of the ionic liquid phase upon heat treatment. UV/Vis spectroscopy indicated formation of functionalized by-products during prolonged periods of heating at 180 °C that could form stable chemical complexes with CO2 molecules, thus drastically affecting both CO2 solubility and diffusivity, and CO2/N2 separation efficiency.

Development of a coupled dispersive liquid-liquid micro-extraction with supported liquid phase micro-extraction for triclosan determination in wastewater

As attention is drawn towards the monitoring of the so-called emerging pollutants, some common household chemicals are not well researched. Household antimicrobials can also present wastewater treatment challenges if not taken cognisance of. Herein we report the application of a recently reported coupled dispersive liquid-liquid micro-extraction (DLLME) with supported liquid phase micro-extraction (LPME) for the extraction of triclosan from wastewater. A univariate approach was used to investigate various parameters amenable to DLLME while no attempt was made to optimise the LPME, achieving the following optimum conditions: 25 μL of a 1:1 toluene-chloroform mixture with 10% sodium chloride into 1 mL aqueous triclosan solutions and extraction time of 15 min achieving an enrichment efficiency 167 times the reference solution prepared with distilled water, good linearity (R2 = 0.9946) with the estimated limit of detection at 0.013 μg/mL and good repeatability (%RSD ≤ 10). The method showed considerable ruggedness with a similar linearity (R2 = 0.9957) and repeatability (%RSD &lt; 10), with only the limit of detection being compromised (0.31 μg/mL) when applied to a wastewater sample using a matrix-matched standard addition approach. Although the GC-FID method detected triclosan in the wastewater sample, the results were negated by those from the GC-MS; as such it therefore could not be concluded with confidence whether the water contained any triclosan or not. However, the results demonstrated the potential of this method in determination of triclosan in water-based samples when the extraction was coupled to a more rugged system such as a GC-MS.

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.