Ethylene Hydroformylation Research Articles

Novel Rh catalytic systems based on microporous metal-organic framework MIL-53(Al) for “green” ethylene hydroformylation

Novel Rh catalytic systems based on microporous metal-organic framework MIL-53(Al) for “green” ethylene hydroformylation

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.

Sustainable Production of Propionic acid and Derivatives on Industrial Scale.

Propionic acid is, after acetic, formic and 2-ethylhexanoic acids, the fourth largest industrially produced carboxylic acid in terms of capacity. In the last decades the technology to produce propionic acid has evolved and more efficient, i. e. more sustainable processes, based on the hydroformylation of ethylene to propionaldehyde and subsequent oxidation with O2 to propionic acid are capturing the growing capacity for this product. For this reason, a perspective is given on developments in sustainable production of propionic acid and derivatives on industrial scale, which is based on a recently published chapter on the same topic in the Ullmann' Encyclopedia of Industrial Chemistry.

K-promoted Ru-based heterogeneous catalysts for ethylene hydroformylation

Hydroformylation is a prototypical C-C coupling reaction of olefins and syngas to produce valuable higher aldehydes. In this study, we investigated the promotional effect of potassium (K) on Ru-based heterogeneous ethylene hydroformylation. The propanal selectivity could reach up to 84.9% at an ethylene (C2H4) conversion of 10.7 % with the addition of K as a promoter. Furthermore, the formation of ethane and the second hydrogenation of olefins were effectively suppressed. Structural characterization results suggested that K promoter could enhance the dispersion of Ru species and increase the electronic density of Ru active sites, thus improving CO adsorption and dissociation. The synergistic effect of Ru and K created a C*-rich and H*-lean local chemical environment, facilitating the formation of aldehydes while effectively reducing the hydrogenation of olefins. This work may provide new insights for development promising Ru-based heterogeneous catalysts for hydroformylation.

Understanding the role of supported Rh atoms and clusters during hydroformylation and CO hydrogenation reactions with in situ/operando XAS and DRIFT spectroscopy.

Supported Rh single-atoms and clusters on CeO2, MgO, and ZrO2 were investigated as catalysts for hydroformylation of ethylene to propionaldehyde and CO hydrogenation to methanol/ethanol with in situ/operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and X-ray absorption spectroscopy (XAS). Under hydroformylation reaction conditions, operando spectroscopic investigations unravel the presence of both single atoms and clusters and detected at first propanal and then methanol. We find that the formation of methanol is associated with CO hydrogenation over Rh clusters which was further confirmed under CO hydrogenation conditions at elevated pressure. The activity of catalysts synthesized via a precipitation (PP) method over various supports towards the hydroformylation reaction follows the order: Rh/ZrO2 > Rh/CeO2 > Rh/MgO. Comparing Rh/CeO2 catalysts synthesized via different methods, catalysts prepared by flame spray pyrolysis (FSP) showed catalytic activity for the hydroformylation reaction at lower temperatures (413 K), whereas catalysts prepared by wet impregnation (WI) showed the highest stability. These results not only provide fundamental insights into the atomistic level of industrially relevant reactions but also pave the way for a rational design of new catalysts in the future.

The synthesis of propanol from ethylene over homogeneous Rh/amine catalytic system via auto-tandem reductive hydroformylation

Here we report our investigation on auto-tandem reductive hydroformylation of ethylene, which allows to obtain propanol in a single technological step. The effect of pressure, ligand structure, temperature, solvent type, ratio of components, and gas supply on the process was studied. It was found that ethylene could be successfully converted to propanol by reductive hydroformylation on a homogeneous Rh/NR3 catalytic system with productivity per Rh atom up to 1299 h−1 (9.0 MPa, 110 ℃). Under milder conditions, low ethylene concentrations and constant syngas supply should be applied. Noteworthy, by using atmospheric distillation as a separation procedure, the system can be used for multiple consecutive reactions without significant activity loss. Probable pathways for the formation of active species and the transformation of rhodium complexes during the distillation process are discussed.

Low-temperature hydroformylation of ethylene by phosphorous stabilized Rh sites in a one-pot synthesized Rh-(O)-P-MFI zeolite

Zeolites containing Rh single sites stabilized by phosphorous were prepared through a one-pot synthesis method and are shown to have superior activity and selectivity for ethylene hydroformylation at low temperature (50 °C). Catalytic activity is ascribed to confined Rh2O3 clusters in the zeolite which evolve under reaction conditions into single Rh3+ sites. These Rh3+ sites are effectively stabilized in a Rh-(O)-P structure by using tetraethylphosphonium hydroxide as a template, which generates in situ phosphate species after H2 activation. In contrast to Rh2O3, confined Rh0 clusters appear less active in propanal production and ultimately transform into Rh(I)(CO)2 under similar reaction conditions. As a result, we show that it is possible to reduce the temperature of ethylene hydroformylation with a solid catalyst down to 50 °C, with good activity and high selectivity, by controlling the electronic and morphological properties of Rh species and the reaction conditions.

Sulfur Poisoning and Self-Recovery of Single-Site Rh1 /Porous Organic Polymer Catalysts for Olefin Hydroformylation.

Sulfur poisoning and regeneration are global challenges for metal catalysts even at the ppm level. The sulfur poisoning of single-metal-site catalysts and their regeneration is worthy of further study. Herein, sulfur poisoning and self-recovery are first presented on an industrialized single-Rh-site catalyst (Rh1 /POPs). A decreased turnover frequency of Rh1 /POPs from 4317 h-1 to 318 h-1 was observed in a 1000 ppm H2 S co-feed for ethylene hydroformylation, but it self-recovered to 4527 h-1 after withdrawal of H2 S, whereas the rhodium nanoparticles demonstrated poor activity and self-recovery ability. H2 S reduced the charge density of the single Rh atom and lowered its Gibbs free energy with the formation of inactive (SH)Rh(CO)(PPh3 -frame)2 , which could be regenerated to active HRh(CO)(PPh3 -frame)2 after withdrawing H2 S. The mechanism and the sulfur-related structure-activity relationship were highlighted. This work provides an understanding of heterogeneous ethylene hydroformylation and sulfur-poisoned regeneration in the science of single-atom catalysts.

Sulfur Poisoning and Self‐Recovery of Single‐Site Rh1/Porous Organic Polymer Catalysts for Olefin Hydroformylation

AbstractSulfur poisoning and regeneration are global challenges for metal catalysts even at the ppm level. The sulfur poisoning of single‐metal‐site catalysts and their regeneration is worthy of further study. Herein, sulfur poisoning and self‐recovery are first presented on an industrialized single‐Rh‐site catalyst (Rh1/POPs). A decreased turnover frequency of Rh1/POPs from 4317 h−1 to 318 h−1 was observed in a 1000 ppm H2S co‐feed for ethylene hydroformylation, but it self‐recovered to 4527 h−1 after withdrawal of H2S, whereas the rhodium nanoparticles demonstrated poor activity and self‐recovery ability. H2S reduced the charge density of the single Rh atom and lowered its Gibbs free energy with the formation of inactive (SH)Rh(CO)(PPh3‐frame)2, which could be regenerated to active HRh(CO)(PPh3‐frame)2 after withdrawing H2S. The mechanism and the sulfur‐related structure–activity relationship were highlighted. This work provides an understanding of heterogeneous ethylene hydroformylation and sulfur‐poisoned regeneration in the science of single‐atom catalysts.

Correction to: The influence of triphenylphosphine trisulfonate (TPPTS) ligands on the catalytic activity of the supported ionic liquid-phase catalysts for the hydroformylation of ethylene

Correction to: The influence of triphenylphosphine trisulfonate (TPPTS) ligands on the catalytic activity of the supported ionic liquid-phase catalysts for the hydroformylation of ethylene

The influence of triphenylphosphine trisulfonate (TPPTS) ligands on the catalytic activity of the supported ionic liquid-phase catalysts for the hydroformylation of ethylene

The influence of triphenylphosphine trisulfonate (TPPTS) ligands on the catalytic activity of the supported ionic liquid-phase catalysts for the hydroformylation of ethylene

Active Site Entropy of Atomically Dispersed Rh/Al2O3 Catalysts Dictates Activity for Ethylene Hydroformylation

The interpretation of catalytic kinetics on supported metal catalysts typically assumes that catalytic cycles occur on static active site structures apart from local rearrangement in the coordination environment. It has been reported that certain atomically dispersed metal active sites (e.g., Cu/Chabazite zeolites and Rh/γ-Al2O3) may be mobile under relevant reaction conditions, suggesting that the active sites themselves have entropy that could be relevant to apparent reaction kinetics. Here, we systematically modify the mobility (degrees of freedom or entropy) of atomically dispersed Rhodium gem-dicarbonyls, Rh(CO)2, supported on γ-Al2O3 through functionalization of the support with straight-chain alkyl-phosphonic acids of different tail lengths ranging from 1 (methyl) to 16 carbons (hexadecyl). The restricted mobility of Rh(CO)2 results in up to a 120 °C decrease in the required temperature for CO desorption from Rh(CO)2 and 1000× increase in turn over frequency for propanal formation via ethylene hydroformylation [where Rh(CO)2 is the most abundant surface intermediate] as compared to unfunctionalized Rh/γ-Al2O3. Eyring analysis suggests that the promoted rates of CO desorption and hydroformylation are due primarily to changes in apparent activation entropy [ΔΔS‡ of up to 60 J/(mol·K)], where restricted mobility of Rh(CO)2 promotes the attempt frequency of CO desorption, which is a kinetically relevant step in hydroformylation. Further, the dependence of Rh(CO)2 reactivity on alkyl phosphonic acid tail length suggests that interactions between phosphonic acid tails far from the active site modify the rigidity of the self-assembled monolayers, such that longer tails better restricted the mobility of Rh(CO)2. This work suggests that active site entropy can influence reaction kinetics on heterogeneous catalysts when changes in active site mobility are coupled to reaction coordinates and further that controlling active site entropy can be an effective design approach to increase catalytic performance.

Ethene Hydroformylation Catalyzed by Rhodium Dispersed with Zinc or Cobalt in Silanol Nests of Dealuminated Zeolite Beta.

Catalysts for hydroformylation of ethene were prepared by grafting Rh into nests of ≡SiOZn-OH or ≡SiOCo-OH species prepared in dealuminated BEA zeolite. X-ray absorption spectra and infrared spectra of adsorbed CO were used to characterize the dispersion of Rh. The Rh dispersion was found to increase markedly with increasing M/Rh (M = Zn or Co) ratio; further increases in Rh dispersion occurred upon use for ethene hydroformylation catalysis. The turnover frequency for ethene hydroformylation measured for a fixed set of reaction conditions increased with the fraction of atomically dispersed Rh. The ethene hydroformylation activity is 15.5-fold higher for M = Co than for M = Zn, whereas the propanal selectivity is slightly greater for the latter catalyst. The activity of the Co-containing catalyst exceeds that of all previously reported Rh-containing bimetallic catalysts. The rates of ethene hydroformylation and ethene hydrogenation exhibit positive reaction orders in ethene and hydrogen but negative orders in carbon monoxide. In situ IR spectroscopy and the kinetics of the catalytic reactions suggest that ethene hydroformylation is mainly catalyzed by atomically dispersed Rh that is influenced by Rh-M interactions, whereas ethene hydrogenation is mainly catalyzed by Rh nanoclusters. In situ IR spectroscopy also indicates that the ethene hydroformylation is rate limited by formation of propionyl groups and by their hydrogenation, a conclusion supported by the measured H/D kinetic isotope effect. This study presents a novel method for creating highly active Rh-containing bimetallic sites for ethene hydroformylation and provides new insights into the mechanism and kinetics of this process.

Rhodium Single‐Atom Catalyst Design through Oxide Support Modulation for Selective Gas‐Phase Ethylene Hydroformylation

AbstractA frontier challenge in single‐atom (SA) catalysis is the design of fully inorganic sites capable of emulating the high reaction selectivity traditionally exclusive of organometallic counterparts in homogeneous catalysis. Modulating the direct coordination environment in SA sites, via the exploitation of the oxide support's surface chemistry, stands as a powerful albeit underexplored strategy. We report that isolated Rh atoms stabilized on oxygen‐defective SnO2 uniquely unite excellent TOF with essentially full selectivity in the gas‐phase hydroformylation of ethylene, inhibiting the thermodynamically favored olefin hydrogenation. Density Functional Theory calculations and surface characterization suggest that substantial depletion of the catalyst surface in lattice oxygen, energetically facile on SnO2, is key to unlock a high coordination pliability at the mononuclear Rh centers, leading to an exceptional performance which is on par with that of molecular catalysts in liquid media.

Rhodium Single-Atom Catalyst Design through Oxide Support Modulation for Selective Gas-Phase Ethylene Hydroformylation.

A frontier challenge in single-atom (SA) catalysis is the design of fully inorganic sites capable of emulating the high reaction selectivity traditionally exclusive of organometallic counterparts in homogeneous catalysis. Modulating the direct coordination environment in SA sites, via the exploitation of the oxide support's surface chemistry, stands as a powerful albeit underexplored strategy. We report that isolated Rh atoms stabilized on oxygen-defective SnO2 uniquely unite excellent TOF with essentially full selectivity in the gas-phase hydroformylation of ethylene, inhibiting the thermodynamically favored olefin hydrogenation. Density Functional Theory calculations and surface characterization suggest that substantial depletion of the catalyst surface in lattice oxygen, energetically facile on SnO2 , is key to unlock a high coordination pliability at the mononuclear Rh centers, leading to an exceptional performance which is on par with that of molecular catalysts in liquid media.

Bifunctional hydroformylation on heterogeneous Rh-WOx pair site catalysts.

Metal-catalysed reactions are often hypothesized to proceed on bifunctional active sites, whereby colocalized reactive species facilitate distinct elementary steps in a catalytic cycle1-8. Bifunctional active sites have been established on homogeneous binuclear organometallic catalysts9-11. Empirical evidence exists for bifunctional active sites on supported metal catalysts, for example, at metal-oxide support interfaces2,6,7,12. However, elucidating bifunctional reaction mechanisms on supported metal catalysts is challenging due to the distribution of potential active-site structures, their dynamic reconstruction and required non-mean-field kinetic descriptions7,12,13. We overcome these limitations by synthesizing supported, atomically dispersed rhodium-tungsten oxide (Rh-WOx) pair site catalysts. The relative simplicity of the pair site structure and sufficient description by mean-field modelling enable correlation of the experimental kinetics with first principles-based microkinetic simulations. The Rh-WOx pair sites catalyse ethylene hydroformylation through a bifunctional mechanism involving Rh-assisted WOx reduction, transfer of ethylene from WOx to Rh and H2 dissociation at the Rh-WOx interface. The pair sites exhibited >95% selectivity at a product formation rate of 0.1 gpropanal cm-3 h-1 in gas-phase ethylene hydroformylation. Our results demonstrate that oxide-supported pair sites can enable bifunctional reaction mechanisms with high activity and selectivity for reactions that are performed in industry using homogeneous catalysts.

Transition-Metal-Catalyzed Carbonylative Multifunctionalization of Alkynes.

Currently, the construction of new carbon-carbon bonds and value-added structures in an atom- and step economical manner has become a continuous pursuit in the synthetic chemistry community. Since the first transition-metal-catalyzed hydroformylation of ethylene was reported by Otto Roelen in the 1930s, impressive progress has been achieved in the carbonylative functionalization of unsaturated C-C bonds. In contrast to alkenes, the carbonylative functionalization of alkynes offers tremendous potential for the construction of multisubstituted carbonyl-containing derivatives because of their two independently addressable π-systems. This review provides a timely and necessary investigation of transition-metal-catalyzed carbonylative mutifunctionalization of alkynes with the exclusion of carbonylative hydrofunctionalizations. Different transition metals including palladium, rhodium, iridium, ruthenium, iron, copper, etc. were applied to the development of novel carbonylative transformation. Various C-C, C-N, C-O, C-S, C-B, C-Si, and carbon-halogen bonds were formed efficiently and give the corresponding tri- or tetrasubstituted α,β-unsaturated ketones, diesters, and heterocycles.

High‐pressure CO, H2, CO2 and Ethylene Pulses Applied in the Hydrogenation of CO to Higher Alcohols over a Bulk Co‐Cu Catalyst

AbstractThe reaction pathways of higher alcohol synthesis over a bulk Co−Cu catalyst (Co : Cu=2 : 1) were investigated by applying high‐pressure pulse experiments as a surface‐sensitive operando method at 280 °C and 60 bar. Using high‐pressure CO and H2 pulses in a syngas flow with a H2:CO ratio of 1, it was shown that the surface of the working 2CoCu catalyst is saturated with adsorbed CO, but not with adsorbed atomic hydrogen, because only the H2 pulses increased the yields of all alcohols and alkanes. The reverse water gas shift reaction (WGSR) was investigated by pulsing CO2. The CO2 pulses poisoned the formation of methanol, ethanol, and 1‐propanol, and the absence of significant CO and H2O responses indicates that the WGSR is not efficiently catalyzed by the applied 2CoCu catalyst excluding the presence of exposed Cu0 sites. A series of ethylene pulses showed that when a threshold mole fraction of ethylene of about 1 vol % is surpassed, 2CoCu is an active catalyst for the hydroformylation of ethylene to 1‐propanol pointing to the presence of highly coordinatively unsaturated Co sites.

Reduced graphene oxide supported cobalt catalysts for ethylene hydroformylation: Modified cobalt-support interaction by rhodium

The metal-support interaction (MSI) alters the geometric morphologies, electronic properties, or distribution of metal nanoparticles, which is indeed to influence the heterogenous catalytic system. Two heterogenous ethylene hydroformylation catalysts, cobalt supported on reduced graphene oxide (RGO) with or without Rhodium (5%Rh-20%Co/RGO and 20%Co/RGO), were successfully synthesized. The effect of the MSI between Co and RGO and a MSI tuning strategy by Rh on the ethylene hydroformylation (EH) were investigated. CoO nanorods was present in fresh Rh-Co/RGO, while only CoO nano-particles were formed in fresh Co/RGO. Rh enhanced the reducibility of the cobalt species. After reduction and the ethylene hydroformylation reaction, Co2C was formed in spent Rh-Co/RGO, while a mixture of Co and CoO were present in the spent Co/RGO. Co2C grew to a large flat plane structure in spent Rh-Co/RGO, while Co and CoO formed smaller nano-particles in spent Co/RGO. The changes of the geometric morphologies and the phases of the active species made by the Rh-Co-RGO interaction significantly enhance the activity of the CO and the selectivity for the production of the C3 oxygenates. A Model on how the nanoparticles distributed on the RGO were hypothesized.

Heterogeneous ethylene hydroformylation on polymer supported Rh-based catalysts: a DFT analysis of the mechanism and Rh–P effect

Heterogeneous reaction mechanism of ethylene hydroformylation.