Hydroformylation of 1-octene using rhodium–phosphite catalyst in a thermomorphic solvent system

The use of a liquid–liquid biphasic thermomorphic or temperature-dependent multicomponent solvent (TMS) system, in which the catalyst accumulates in one of the liquid phases and the product goes preferably to the other liquid phase, can be an enabling strategy of commercial hydroformylation processes with high selectivity, efficiency and ease of product separation and catalyst recovery. This paper describes the synthesis of n-nonanal, a commercially important fine chemical, by the hydroformylation reaction of 1-octene using a homogeneous catalyst consisting of HRh(PPh₃)₃(CO) and P(OPh)₃ in a TMS-system consisting of propylene carbonate (PC), dodecane and 1,4-dioxane. At a reaction temperature of 363 K, syngas pressure of 1.5 MPa and 0.68 mM concentration of the catalyst, HRh(CO)(PPh₃)₃, the conversion of 1-octene and the yield of total aldehyde were 97% and 95%, respectively. With a reaction time of 2 h and a selectivity of 89.3%, this catalytic system can be considered as highly reactive and selective compared to conventional ones. The resulting total turnover number was 600, while the turnover frequency was 400 h^?1. The effects of increasing the concentration of 1-octene, catalyst loading, partial pressure of CO and H₂ and temperature on the rate of reaction have been studied at 353, 363 and 373 K. The rate was found to be first order with respect to concentrations of the catalyst and 1-octene, and the partial pressure of H₂. The dependence of the reaction rate on the partial pressure of CO showed typical substrate inhibited kinetics. The kinetic behavior differs significantly from the kinetics of conventional systems employing HRh(CO)(PPh₃)₃ in organic solvents. Most notable are the lack of olefin inhibition and the absence of a critical catalyst concentration. A mechanistic rate equation has been proposed and the kinetic parameters evaluated with an average error of 5.5%. The activation energy was found to be 69.8 kJ/mol.     

Continuous Gas‐Phase Hydroformylation of 1‐Butene using Supported Ionic Liquid Phase (SILP) Catalysts

The concept of supported ionic liquid phase (SILP) catalysis has been extended to 1‐butene hydroformylation. A rhodium‐sulfoxantphos complex was dissolved in [BMIM][n‐C₈H₁₇OSO₃] and this solution was highly dispersed on silica. Continuous gas‐phase experiments in a fixed‐bed reactor revealed these SILP catalysts to be highly active, selective and long‐term stable. Kinetic data have been acquired by variation of temperature, pressure, syngas composition, substrate and catalyst concentration. A linear dependency in rhodium concentration could be established over a large concentration range giving another excellent hint for truly homogeneous catalysis in the SILP system. Compared to former studies using propene, the SILP system showed significantly higher activity and selectivity with 1‐butene as feedstock. These findings could be elucidated by solubility measurements using a magnetic microbalance.     

Kinetics and mass transfer in hydroformylation—bulk or film reaction?

The kinetics of a gas–liquid reaction, alkene hydroformylation was studied in the presence of a homogeneous catalyst in a pressurised laboratory‐scale semibatch reactor. Hydroformylation of propene to isobutyraldehyde and n‐butyraldehyde was carried out at 70–115°C and 1–15 bar pressure in 2,2,4‐trimethyl‐1,3‐pentanediol monoisobutyrate solvent with rhodium catalyst using the ligands cyclohexyl diphenylphosphine. In order to evaluate the influence of mass transfer, experiments were made using varied stirring rate from 100 to 1000 rpm at 100°C and 10 MPa syngas pressure. Only at higher stirrings rates, the reaction took place in the kinetic regime. A reactor model was developed comprising both complex kinetics and liquid‐phase mass transfer. The model was based on the theory of reactive films. The model is able to predict under which circumstances the hydroformylation process is affected by liquid‐phase diffusion of the reactants. Experimental data and model simulations are presented for the hydroformylation of propene in the presence of a homogeneous rhodium catalyst.     

Kinetics of hydroformylation of 1-octene in ionic liquid-organic biphasic media using rhodium sulfoxantphos catalyst

Biphasic hydroformylation of 1-octene was performed using rhodium sulfoxantphos catalyst dissolved in [BuPy][BF₄] ionic liquid. Preliminary experiments proved this system to retain the catalytic complex within the ionic liquid phase and to maintain a high selectivity towards the linear aldehyde (n:iso ratio of 30) over several cycles. Process parameter investigation showed a first order dependence of the initial rate with respect to the catalyst and 1-octene concentrations, but a more complex behavior with respect to hydrogen (fractional order) and carbon monoxide partial pressures (inhibition at high pressures). Different mathematical models were selected based on the trends observed and evaluated for data fitting. Also, rate models were derived from a proposed mechanism, using Christiansen matrix approach. To calculate concentrations of substrates in the catalytic phase as required by this kinetic modeling, solubility measurements were preformed for the gases (pressure drop technique), as well as for 1-octene and n-nonanal (thermogravimetry analysis).     

The Effect of Operational Parameters on the Catalytic Combustion of n-Butane/Air Mixtures on Platinum Wire

The effect of mixture composition, total pressure and catalyst temperature on the kinetics of the catalytic combustion of n-butane/air or n-butane/oxygen mixtures on isothermally heated platinum wire is reported. The catalyst temperature was changed from 680 to 1,130 K for mixtures containing n-butane between 1 and 4.5% at total pressures between 10 and 100 kPa. The measurements allowed the determination of different kinetic properties like reaction rate, turnover frequency, overall and partial reaction orders and activation energy. The pressure dependence of the reaction rate offered the possibility to make a critical analysis of the kinetic equations frequently utilized in the literature.     

Rapid bistable reactions in porous catalysts

We analyze the kinetics of rapid bistable reactions (e.g., CO or hydrogen oxidation on Pt) occurring on a nm catalyst particle located inside a mesoscopic pore. Limitations for reactant diffusion inside a single pore are shown to modify the dependence of the reaction rate on the reactant pressures outside the pore. In particular, the position of the maximum reaction rate is shifted to higher CO pressures (provided that the O₂ pressure is fixed). This effect is significant if a pore is not too short. Similar effects are possible during oscillations in CO oxidation on supported nm catalyst particles.     

Acid-catalysed dehydration of alcohols in supercritical water

At pressures exceeding its critical pressure water retains its ionic properties to temperatures of 400 °C or more. In water under these conditions trace amounts of Arrhenius acids dissociate and selectively catalyse the dehydration of alcohols, diols, and polyols. High yields of the desired dehydration product (ethene from ethanol, propene from propanol, acetaldehyde from ethylene glycol, and acrolein from glycerol) can be obtained with a residence time of less than one minute. However, for ethanol the equilibrium conversion appears to be less than predicted by ideal solution thermochemical calculations. This may be due to catalyst deactivation, or it may be an effect of hydrogen bonding between the water and the reactant alcohol. The dehydration of n-propanol proceeds by a first order reversible reaction whose equilibrium is close to that predicted by thermodynamics. Because these dehydration reactions proceed rapidly with a high degree of specificity, they appear to be good candidates for industrial exploitation.     

Catalytic behavior of silica-supported polyalumazane-Co-Ru bimetallic complex for the hydroformylation of cyclohexene

Summary The cobalt and ruthenium bimetallic complex of an inorganic polymer, polyalumazane (abbr. as Al-N-Co-Ru), was prepared. The catalytic behavior of this complex for the hydroformylation of cyclohexene was studied. The conversion percents were more than 90% in a certain reaction temperature and pressure. Both of the conversion and product composition was also affected by the Ru/Co ratio in catalyst and the CO/H₂ ratio in reactant gas. Aldehyde was firstly formed in the hydroformylation, and then it was further hydrogenated to form the corresponding alcohol. There was no any other by-product formed in the reaction. Compared with the corresponding homogeneous catalyst system, the Al-N-Co-Ru catalyst has higher catalytic activity and stability with lower Ru/Co ratio (1.86). After reused for several times, the catalyst did not lose its activity. The total turnover number was more than 2500 (based on the amount of cobalt used).     

Rhodium catalyzed hydroformylation of 1-octene in microemulsion: comparison with various catalytic systems

In this work, we describe how addition of alkylpolyglycol ether type nonionic surfactant affects the hydroformylation of 1-octene in the presence of phosphine modified rhodium catalyst. Influence of different process parameters such as ligand excess and amount of surfactant on the reaction rate and selectivity were discussed. Direct comparison of microemulsion systems with classic processes was achieved by performing the reactions under comparable homogeneous and biphasic conditions. Thus, the experiments were carried out using catalysts such as unmodified rhodium carbonyl HRh(CO)₄ and HRh(CO)(PPh₃)₃ in homogeneous system, Rh–TPPTS complex in two-phase system and in association with co-solvent.     

An Active and Stable RhH(CO)(PPh3)3-Derived SiO2-Tethered Catalyst Via a Thiol Ligand for Cyclohexene Hydroformylation

A RhH(CO)(PPh₃)₃-derived SiO₂-tethered catalyst via a thiol ligand is not only quite effective and stable for cyclohexene hydroformylation under the milder conditions of 100 °C and 28 bar of equimolar CO and H₂ but also more active than the corresponding homogeneous catalyst. This catalyst has the advantage in resistance to rhodium leaching over homologous tethered catalysts via phosphine and amine ligands.     

Highly Selective Pd‐Catalyzed Reductive Coupling of Substituted Haloarenes with Supported Phase‐Transfer Catalyst using Zn as the Reducing Agent

Highly selective reductive coupling of substituted haloarenes to biaryls is accomplished by Zn in N,N‐dimethylformamide (DMF) and in the presence of a catalytic amount of PdCl₂, PPh₃, and a carbon‐supported phase‐transfer catalyst (PTC). Selectivity as high as 100% is achieved with chlorotoluenes. It is realized that the supported PTC has a predominant role in minimizing the rate of the hydrodehalogenation reaction. The reaction is found to be selective only when homogeneous PdCl₂ is applied as the catalyst, whereas heterogeneous Pd/C‐catalyst selectively reduces chloroarenes to arenes under similar conditions. The role of PPh₃ is discussed and the effects of different process parameters such as temperature, PdCl₂ loading, PPh₃ to PdCl₂ ratio, amount of supported PTC, and solvents have been examined. A mechanism is proposed which is in good agreement with the experimental results obtained.     

Mechanistic aspects of the oxidative dehydrogenation of propane over an alumina-supported VCrMnWOx mixed oxide catalyst

Mechanistic and kinetic aspects of the catalytic oxidative dehydrogenation of propane (ODP) were studied within a wide range of temperatures (673–773 K), partial pressures of oxygen (0–20 kPa), propane (0–40 kPa) and propene (0–4 kPa) under both steady-state ambient-pressure and transient, vacuum conditions in the temporal analysis of products (TAP) reactor. A Mn_0.18V_0.3Cr_0.23W_0.26O_x–Al₂O₃ catalyst was identified as a selective catalyst for ODP by high-throughput experiments. For comprehensive catalyst characterization, XRD, BET, and in situ UV–visible techniques were applied. The results from transient experiments in combination with UV–visible tests reveal that selective and non-selective propane oxidation occurs on the same active surface sites, i.e., lattice oxygen. CO_x formation takes place almost exclusively via consecutive propene oxidation, which involves both lattice and adsorbed oxygen species, with the latter being active in CO formation. However, the adsorbed species play a minor role. CO₂ formation was found to increase in the presence of propene in the reaction feed. Optimized operating conditions for selective propane oxidation were derived and discussed based on the experimental observations with respect to the influence of temperature and partial pressures of O₂, C₃H₆ and C₃H₈ on the reaction. In co-feed mode with a propane to oxygen ratio of 2, optimal catalytic performance is achieved at low partial pressures of oxygen and high temperature. Propene selectivity can be also improved by carrying out the ODP reaction in a periodic mode; that is an alternate feed of propane and air.     

Heterogenized HRh(CO)(PPh3)3 on zeolite Y using phosphotungstic acid as tethering agent: a novel hydroformylation catalyst

Heterogenization of HRh(CO)(PPh₃)₃ tethered through phosphotungstic acid to zeolite Y support, gives a novel hydroformylation catalyst with excellent stability, reusability and even improved activity. The activity, selectivity and stability of this catalyst for hydroformylation of a variety of linear and branched olefinic substrates have been demonstrated. The heterogenized HRh(CO)(PPh₃)₃ catalyst was recycled several times without loss of any activity. The catalyst was characterized by powder XRD, SEM, XPS, and ³¹P CP MAS NMR to establish true heterogeneity and morphological characteristics.     

Support and precursor effects on the preparation of new heterogenized Pt/Sn catalysts for the selective hydroformylation of 1-pentene

New heterogenized Pt/Sn catalysts selective for the hydroformylation of 1-pentene have been synthesized. The complex cis-[PtCl₂(PPh₃)₂] and the SnCl₂.2H₂O or SnC₂O₄ precursors have been anchored on silica-, magnesia- and alumina-carriers. X-ray photoelectron spectroscopy was used to determine the surface composition and the nature of the anchored species. The hydroformylation activity was found to depend on the type of support and tin precursor used. Only the silica supported catalysts were active in the hydroformylation reaction. Samples prepared from SnCl₂-2H₂O were 200-fold more active than those prepared from SnC₂O₄. Selectivity ton-hexanal of the silica-supported catalyst prepared from SnCl₂-2H₂O was as high as 94.4% at 39.2% conversion of 1-pentene.     

Selective conversion of propane to propene by the catalytic oxidative dehydrogenation over cobalt and magnesium molybdates

Catalytic performances of various metal molybdates were tested in the oxidative dehydrogenation of propane to propene with molecular oxygen under an atmospheric pressure. Most of the molybdates tested promoted the selective oxidative conversion of propane to propene and among them cobalt and magnesium molybdates were found highest in the activity and selectivity. It was also found that their catalytic activities were highly sensitive to the catalyst composition, and it turned out that Co_0.95MoO _x and Mg_0.95MoO _x catalysts which have slightly excess molybdenum showed the highest activity in the oxidative dehydrogenation of propane. Under the optimized reaction conditions, higher reaction temperatures and lower partial pressures of oxygen, these catalysts gave 60% selectivity to propene at 20% conversion of propane. Since the molybdates having the surface enriched with molybdenum oxide tended to show high activity for the propane oxidation, surface molybdenum oxide clusters supported on metal molybdate matrix seem to be the active sites for the selective oxidative dehydrogenation of propane.     

Olefin hydroformylation and selective hydrogenation of acetaldehyde on Mo-promoted Rh/SiO2 catalysts derived from metal salt and heteronuclear cluster precursors

Molybdenum promoted Rh/SiO₂ catalysts have been prepared by using the heteronuclear cluster (C₅H₅)₃RhMo₂(CO)₅ as well as metal salt precursors. The promoting effect of molybdenum has been studied for the hydroformylation of ethene and propene and the hydrogenation of acetaldehyde. It has been found that molybdenum, especially on the cluster-derived catalyst, increases both the hydrogenation and the hydroformylation rate of the olefins. No specific influence on the CO insertion reaction could be obtained. As an explanation, the promotion of the initial step to form intermediate surface alkyl groups has been proposed as the rate determining step for ethene hydroformylation. The promotion of the alcohol formation by bimetallic centers having Rh and Mo in close vicinity has been supported by the results of the hydrogenation of acetaldehyde.     

Hydroformylation with rhodium phosphine-modified catalyst in a microemulsion: comparison of organic and aqueous systems for styrene, cyclohexene and 1,4-diacetoxy-2-butene

Use of microemulsion as a reaction media in the hydroformylation of different alkenes, namely styrene, cyclohexene and 1,2-diacetoxy-2-butene have been studied using alkylpolygylcol ether-type nonionic surfactant in the presence of phosphine-modified rhodium catalyst. The combination of the experiments under comparable homogeneous and biphasic conditions were performed in order to make direct comparison of microemulsion with classical systems. Thus, the experiments were also carried out using catalysts such as unmodified rhodium carbonyl H Rh(CO)₄ and H Rh(CO)(PPh₃)₃ in homogeneous system, Rh–TPPTS complex in two-phase system and in association with co-solvent.     

Highly efficient catalyst system for the synthesis of 2‐arylpropionic acids by carbonylation

Carbonylation of 1‐(4‐isobutylphenyl)ethanol has been studied using a homogeneous catalyst system consisting of PdCl₂(PPh₃)₂/ TsOH/ LiCl. Higher reaction rates with TOF up to 1200 h⁻¹ and ibuprofen selectivity >95% have been achieved at 388 K under a CO partial pressure of 5.4 MPa. The reaction proceeds through the formation of 4‐isobutylstyrene and 1‐(4‐isobutylphenyl)ethyl chloride as intermediates. The same catalyst system is shown to be effective for carbonylation of various α-arylethanols, vinyl aromatics and corresponding chloro derivatives. This revised version was published online in July 2006 with corrections to the Cover Date.     

Green and Simple Method for Catalytic Hydrogenation of Diene-Based Polymers

Catalytic hydrogenation of diene-based polymers is investigated in bulk form with different types of homogeneous and heterogeneous catalysts. Among these catalysts, we found that RhCl(PPh₃)₃, which could be promoted by its co-catalyst ligand (PPh₃), was able to diffuse into the bulk polymer. It was shown that a required high conversion (95?mol?%) was achieved within a few hours for the hydrogenation of acrylonitrile-butadiene rubber, styrene-butadiene rubber, and polybutadiene rubber using this catalyst. As an example, the hydrogenation of NBR in bulk form was investigated with respect to the effects of reaction temperature, pressure, and catalyst loading in an attempt to understand the hydrogenation of the bulk polymer.     

Rhodium complexes supported on nanoporous activated carbon for selective hydroformylation of olefins

Activated carbon with nanoporous structure, high surface area (2500 m²/g) and total pore volume (2.35 cm³/g) was prepared from Mango seed shell (Mangifera indica L.) via chemical activation method and used as support to impregnate active hydroformylation rhodium complexes HRhCO(PPh₃)₃ and Rh(acac)(CO)₂. The prepared catalysts were characterized by XRD, SEM, TEM, NMR, IR, TGA, and N₂ adsorption/desorption techniques. The supported catalysts have shown excellent selectivity for aldehydes (~ 99%) in the hydroformylation of olefins with good stability and recyclability up to 4 cycles.