Use of water-soluble phosphine ligands in heterogeneous hydroformylation catalysis : application to long-chain 1-alkenes

The two-phase rhodium-tri(m-sulfonatophenyl)phosphine (Rh-TPPTS) system for the hydroformylation of 1-octene, 1-decene, and 1-dodecene to the corresponding aldehydes, has been investigated. Due to the two distinct phases - the catalytic species in the aqueous phase and the products and reactants in the organic phase - the separation of the catalyst was easily facilitated. A comparison was made of the activity, selectivity towards linear aldehydes, and catalyst lifetime of two systems where i) the active catalytic species were generated in situ from rhodium trichloride (RhCl₃.3H₂O) and excess phosphine ligand (TPPTS) under mild hydroformylation conditions (5 MPa H₂/CO (1:1); 100 °C); and ii) where the rhodium(I) complex, RhH(CO)(TPPTS)₃ is used as the catalyst precursor. The former system was found to be superior in activity and selectivity to that of the latter, achieving fairly high conversions of ca. 60% for the hydroformylation of 1-octene, with n:iso ratios of up to 16:1 for a catalyst composition a Rh:P ratio of 1:30. Unfortunately low conversions of ca. 10% for the hydroformylation of 1-decene and ca. 4% for that of 1-dodecene resulted under the same conditions. While the reasons for the drastic decrease in conversion for C₁₀ and C₁₂ alkenes is not completely clear, this poor conversion is attributed to the extremely low solubility of the long-chain 1-alkenes in the aqueous phase. Under certain optimum conditions (Rh:P ≥ l :20), virtually no leeching of rhodium into the organic phase was detected. A ³¹P NMR spectroscopic study was undertaken in an attempt to ascertain the nature and distribution of rhodium tertiary-phosphine complexes in the aqueous phase before and after the mixture was subjected to standard hydroformylation conditions

Homogeneously catalyzed hydroformylation in supercritical carbon dioxide : kinetics, thermodynamics, and membrane reactor technology for continuous operation

The increased awareness for environmental issues and concomitant environmentally conscious governmental policies has prompted the chemical process industry to implement "greener" production and synthesis methods. In particular, the reduction of the emission of harmful, often organic, substances, reduction of the production of waste, and increasing the energy efficiency are three important aspects in the development of environmentally benign chemical production processes. For the chemical and chemical engineering academic community this has given rise to a new direction, where the concept of "green chemistry" is being explored. Supercritical fluids have been established as promising substitutes to organic solvents. Carbon dioxide is of particular interest as an alternative solvent as it has a low toxicity, is non-flammable and has an accessible critical temperature and pressure. In addition, catalysis is an important tool for the optimization of atom efficiency of a chemical conversion, and therefore for the reduction of waste production. Additionally, catalysis allows for reactions to take place under milder conditions, which can also contribute to an increase in energy efficiency. In particular, soluble molecular organometallic catalysts allow chemical conversions with a higher rate and a better selectivity than their heterogeneous counterparts. The difficult separation of a homogeneous catalyst from reaction products, without deactivating the catalyst, is one of the main obstacles for their application on an industrial scale. Nanofiltration using a microporous ceramic membrane has the potential to be a solution to this problem. A large enough catalyst molecule will be retained while reaction products and solvent can permeate across the membrane. In the field of separation technology membranes have emerged as an energy efficient alternative to conventional separation methods, like distillation and extraction. Ceramic membranes are seen as one of the most promising candidates to purify process streams under demanding conditions. The main objectives of this thesis are the evaluation of the possible advantages of using supercritical carbon dioxide as a solvent as an alternative for organic solvents, and the investigation into the potential of membrane technology for the retention of homogeneous catalysts. The hydroformylation of 1-octene, which is an example of a homogeneously catalyzed reaction on an industrial scale, is considered as a model reaction. To perform the hydroformylation in supercritical carbon dioxide an experimental procedure has been developed, which allows for catalyst preparation under hydroformylation conditions and for carrying out the hydroformylation reaction with a well-defined starting point. It has been demonstrated that with this experimental procedure it is possible to obtain highly reproducible results. Furthermore, a relationship between the change in pressure and the change in reaction mixture composition as a function of time has been established. Using this experimental procedure the effect of total pressure, temperature, concentration of reactants, and concentration of catalyst precursors on the reaction rate, chemoselectivity, and the regioselectivity of the hydroformylation of 1-octene has been studied. The concentration of carbon dioxide had an effect on the regioselectivity of the reaction. Therefore, the same density of solvent has been used for each experiment rather than the more common approach of applying the same total pressure for each experiment. Based on the results obtained by the variation of the reaction parameters a kinetic model has been developed. An optimization method has been applied to find the model parameter values that best describe the experimental data. The observed kinetics for the catalyst based on rhodium(I) dicarbonyl acetylacetonate and tris(3,5-bis(trifluoromethyl)phenyl)phosphine shows resemblance to that observed for the hydroformylation where bulky phosphites have been used as the ligand. For this catalyst a high activity in the order of 5×103 to 12×103 mol1-octene molRh-1 h-1 has been observed at 70 °C. Organometallic complexes based on rhodium with phosphine ligands with a varying number of trifluoromethyl groups have been screened for their activity and selectivity for the hydroformylation of 1-octene. Furthermore, the effect of the type of solvent: carbon dioxide, hexane, and toluene has been included in this study. An increase in the number of trifluoromethyl substituents on the triphenylphosphine ligand results in an increase in 1-octene conversion rate and a decrease in the overall selectivity towards aldehydes. This behaviour is observed in all three solvents. For supercritical carbon dioxide or hexane, as the solvent, the outcome of the hydroformylation reaction in terms of activity and selectivity shows great similarity. By following the hydroformylation of 1-octene in time, it was observed that during batch operation rhodium catalysts with trifluoromethyl-substituted triarylphosphines showed a higher differential regioselectivity than based on the overall regioselectivity at the end of the reaction. For the hydroformylation in carbon dioxide this effect was most pronounced. Both the mode of operation, batch or semi batch, and the type of solvent had a significant influence on this phenomenon. The transport of a supercritical fluid across a microporous alumina supported titania membrane has been investigated. The dependence of the permeation of carbon dioxide across the titania membrane on the feed pressure is similar to what has been previously observed for microporous alumina supported silica membranes. At high feed pressure viscous flow appears to be the main mechanism of mass transport across the membrane. Furthermore, the titania membrane shows a reasonable stability over a period of operation of about at least six months in varying conditions. Finally, the first continuously operated experiment has been performed, in which hydroformylation of 1-octene and separation of the catalyst have been integrated using a membrane reactor. During a 27.5 h of operation of the membrane reactor, spread over four consecutive days, a maximum conversion of 17 % and a maximum regioselectivity of 5 in terms of n:iso ratio has been observed. The conversion and the n:iso ratio, which is the ratio between the linear and branched aldehyde product, decrease as a function of the number of permeated reactor volumes indicating a loss of catalyst. Permeation of free ligand and the catalytic species through the membrane appear to be the main reasons for the decrease in activity and selectivity. A good match between membrane retention characteristics and the size of the catalyst and its precursors is not found yet. However, a number of feasible improvements can be made to improve the retention of the catalyst. Using a membrane for retention of a homogeneous catalyst in combination with the application of carbon dioxide as a solvent for the continuous hydroformylation of 1-octene has great potential. Successful application of the envisioned membrane reactor process can have implications for other homogeneously catalyzed reactions of which asymmetric hydrogenation is a commercially relevant example. As a result of the experimental methods used in this thesis the potential benefits of using carbon dioxide as an environmentally benign alternative to organic solvents could be further extended

Integrated Chemical Processes in Liquid Multiphase Systems

The essential principles of green chemistry are the use of renewable raw materials, highly efficient catalysts and green solvents linked with energy efficiency and process optimization in real-time. Experts from different fields show, how to examine all levels from the molecular elementary steps up to the design and operation of an entire plant for developing novel and efficient production processes

Hydroformylation of Higher Olefins Using Radium Phosphite Complex Catalyst

Hydroformylation of olefins with CO and Hz at total pressure of IS to 50 bar and temperature of 80 to l20°C, in presence of rhodium (Rh)-based homogeneous catalysts for production of aldehydes has demonstrated high yields and selectivity. Rh-based catalysts are expensive and the commercial viability of a process that uses such catalysts substantially depends on the efficiency of catalyst recovery and product separation. In this work, a novel temperature dependent multi-component solvent (TMS) or 'thermomorphic solvent' system has been used as the reaction medium to investigate hydroformylation of two higher olefins - 1-octene and 1-dodecene - to synthesize the corresponding aldehydes at a lower pressure of 15-25 bar and temperature of 80 to 100°C. Such a solvent mixture changes thermally from biphasic to monophasic with distribution of the products and of the catalyst in the non-polar and polar phases thus simplifying the process of separation and recycling of the catalyst. A TMS- system consisting of three components - propylene carbonate (PC), ndodecane and 1,4-dioxane was used in this study. The presence of 1,4-dioxane imparts the thermomorphic character to the solvent mixture. For a gas-liquid reaction, the solubility of the reactant gas in the liquid medium is an important parameter required for the interpretation of reaction kinetics. Therefore experimental measurement of solubility of the gaseous reactants - CO and Hz - in the individual components of the solvent as well as in their mixtures was performed up to a pressure of 1.5 MPa and temperature range of 298-343 K. The effects of solvent composition, partial pressures of the gaseous reactants - CO and Hz, reaction temperature and catalyst loading on the rate, yield and selectivity of the linear aldehydes were also investigated. At a reaction temperature of 363 K and total pressure of 1.5 MPa and 0.68 mM HRh(CO)(PPh3)3, the conversion of 1- octene and the yield of aldehyde were 97 % and 95 %, respectively. The aldehyde product was recovered in the non polar phase whereas the catalyst remained in the polar phase with low catalyst loss of 3 %. With a reaction-time of 2 h and a selectivity of 89 %, this catalytic system can be considered as highly reactive and selective. The rate was found to be first order with respect to catalyst, 1-octene and PH, . The rate vs. Pco resembled a typical case of substrate inhibited kinetics. Hydroformylation of Higher Olefins Using Radium Phosphite Complex Catalys

Systematic Selection of Green Solvents and Process Optimization for the Hydroformylation of Long-Chain Olefines

Including ecologic and environmental aspects in chemical engineering requires new methods for process design and optimization. In this work, a hydroformylation process of long-chain olefines is investigated. A thermomorphic multiphase system is employed that is homogeneous at reaction conditions and biphasic at lower temperatures for catalyst recycling. In an attempt to replace the toxic polar solvent N,N-dimethylformamide (DMF), ecologically benign alternatives are selected using a screening approach. Economic process optimization is conducted for DMF and two candidate solvents. It is found that one of the green candidates performs similarly well as the standard benchmark solvent DMF, without being toxic. Therefore, the candidate has the potential to replace it

Multiphasic aqueous hydroformylation of 1-alkenes with micelle-like polymer particles as phase transfer agents

Micelle-like polymer particles have been applied in aqueous multiphasic hydroformylation reactions of long chain alkenes. These colloids act as phase transfer agents for the nonpolar substrates and as carriers for the catalyst bearing sulfonated ligands by electrostatic attraction. The catalyst performance and the phase separation were optimized with special focus on the conversion, selectivity and catalyst recovery, as those are key points in multiphasic systems to achieve a feasible industrial process. The effect on the catalyst performance of the number of sulfonate groups and electron withdrawing trifluoromethyl groups in the ligand has been studied. The approach was successfully demonstrated for 1-alkenes from 1-hexene to 1-dodecene. For 1-octene, a TOF of more than 3000 h⁻¹ could be achieved at a substrate to catalyst ratio of 80 000, while keeping the rhodium and phosphorous leaching below 1 ppm. In repetitive batch experiments the catalyst was recycled four times, yielding an accumulated TON of more than 100 000 for 1-octene

The potential of hydroaminomethylation : directing the cascade

Amino compounds are important building blocks or end products in a broad range of durable and consumer goods in everyday life such as polymers, airbags, textiles, insecticides, and pharmaceuticals. Classical syntheses of amines often lead to large amounts of waste, mainly inorganic salts. One of the most promising new reactions for the production of amines in terms of atom-efficiency, activity, selectivity, and applicability is the hydroaminomethylation of alkenes in which water is the only side product. Especially the possibility to synthesise primary amines atom-efficiently from cheap alkene feedstocks and ammonia by hydroaminomethylation makes this an interesting reaction from an industrial point of view. Although the hydroaminomethylation has been discovered already in 1949 by Reppe at BASF, most research with respect to this reaction has been performed during the last 15 years. In Chapter 1, the most relevant and interesting literature with respect to the hydroaminomethylation reaction, is reviewed. Chapter 2 deals with catalyst recycling in a biphasic ionic liquid system. Hydroaminomethylation reactions were performed successfully in an imidazolium-based ionic liquid using a rhodium/Sulfoxantphos system by reacting piperidine with different n-alkenes, affording yields higher than 95% of the resulting amine with turnover frequencies of up to 8400 h-1, along with high regioselectivity for the linear amines with l/b ratios up to 78. Additionally, facile quantitative catalyst recovery was accomplished and recycling of the catalyst and product separation were achieved by a fast phase separation after the reaction. The product distribution was monitored in time at different temperatures both in an organic solvent and in the ionic liquid in order to investigate and compare the course of the formation of (side) products and intermediates in these reactions. Furthermore, it was shown that the nature of the Rh-precatalyst has a profound effect on the activity and selectivity. Protic organic solvents and ionic liquids containing a C-H acidic bond in the imidazolium part have a beneficial effect on the hydrogenation activity of the catalyst systems. Chapter 3 is dedicated to the very fast and selective hydroaminomethylation with a novel class of ligands. In order to increase the activity and to maintain a good selectivity in the hydroaminomethylation reaction in comparison to Rh/phosphine-catalysed systems, a new p-acidic ligand, the bis-[(dipyrrolyl)phosphino]xanthene, was synthesised. In combination with rhodium, this ligand leads to outstanding activities and selectivities with turnover frequencies of 6200 h-1 and very high l/b ratios exceeding 200. Furthermore, it was shown that the pKa value of the alcohol used in the solvent mixture has a profound effect on the performance of the catalytic systems. Acidic media enhance the activity, while less acidic media increase the regio- and chemoselectivity, as well as the degree of double bond isomerisation. Chapter 4 describes the Rh-catalysed hydroaminomethylation of internal alkenes towards linear amines is described using amino-functionalised ligands. Bulky and rigid substituents were introduced and the ligand backbone was functionalised with a (bisindolyl) phosphine moiety in order to increase the regioselectivity in this process. However, bis-[(dipyrrolyl)phosphino]xanthene, introduced in Chapter 3, again turned out to be the best performing ligand in combination with rhodium. Although the reaction is slower than in case of n-alkenes, catalyst activities are still reasonably high. The influence of catalyst preformation, reaction temperature, solvent mixture, and syngas ratio are described. Furthermore, the effect of adding a monodentate phosphorus ligand (phosphines or phosphites) to the reaction mixture was investigated. Interestingly, the regioselectivity could be increased considerably by addition of triphenylphosphine to the catalyst mixture, which can be explained by changing the isomerisation rate related to ß-hydrogen elimination in this particular way. Chapter 5 involves the coordination chemistry of the novel xanthene-based aminofunctionalised ligands, which were discussed in Chapters 3 and 4, to rhodium and platinum. In combination with rhodium, these compounds display interesting catalytic results in the hydroaminomethylation reaction. In order to clarify their structure/performance relationship, the coordination behaviour was investigated. The structural properties of the ligands were studied by NMR spectroscopy of the corresponding rhodium and platinum complexes, while the electronic properties were examined by studying the IR frequencies of the CO stretch vibrations in the particular rhodium-carbonyl complexes. For two ligands, the corresponding selenides were synthesised. The NMR coupling constant JSe-P can be used as a measure for the s-donor ability of a ligand. Furthermore, the coordination behaviour of the ligands was investigated by high pressure NMR and IR spectroscopic measurements under actual hydroformylation reaction conditions. The ligands have been compared to the diphosphine ligand Xantphos, which performs very well in regioselective hydroformylations. An X-ray crystal structure was determined for a rhodium complex with Xantphos. Although the hydroaminomethylation reaction is a promising and atom-efficient alternative for the classical production process towards amines, this reaction has not been applied on a large scale in industry to date. On the other hand, in recent (patent) literature, more and more publications concerning this interesting reaction can be found. The near absence of hydroaminomethylation in industry might be explained by the fact that most publications mention rhodium, which is a very expensive metal. Moreover, no chemo- and regioselective synthesis of linear primary amines via hydroaminomethylation with NH3 has been reported up to now. Most probably, this reaction will first be applied in fine chemical or pharmaceutical industry, since smaller product volumes and higher added value are common practice in these industries. For bulk chemical application, this reaction needs further optimisation for which intensive and challenging research is necessary. Chapter 6 deals with these possibilities and the future of hydroaminomethylation. Hydroaminomethylation with protected amines and the opportunities of primary amine protection by using ammonium carbamate as a combined substrate/dynamic protection group has been presented

Process Design Based on CO2-Expanded Liquids as Solvents

Magdeburg, Univ., Fak. für Verfahrens- und Systemtechnik, Diss., 2014von Kongmeng Y