Higher hydroformylation

The higher hydroformylation activity of the mixed-metal cluster [Co2Rh2(CO)i2] as compared to those of either the parent clusters... 

Phosphites. The modification of rhodium catalysts with triorganophos-phites generally results in higher hydroformylation activity than modification with triorganophosphines. Thus, phosphites allow the application of milder reaction conditions (269). 

The 0x0 process is employed to produce higher alcohols from linear and branched higher olefins. Using a catalyst that is highly selective for hydroformylation of linear olefins at the terminal carbon atom. Shell converts olefins from the Shell higher olefin process (SHOP) to alcohols. This results in a product that is up to 75—85% linear when a linear feedstock is employed. Other 0x0 processes, such as those employed by ICI, Exxon, and BASE (all in Europe), produce oxo-alcohols from a-olefin feedstocks such alcohols have a linearity of about 60%. Enichem, on the other hand, produces... 

The spectmm of oxo products ia Japan is far less diverse. Nearly 75% of Japan s total oxo capacity of 733,000 t is dedicated to the hydroformylation of propylene. 2-EH derived from -butyraldehyde is by far the dominant product. Other products iaclude linear alcohols and higher branched alcohols. Additionally, Japan is the world s principal source of branched heptyl alcohol. The three ptincipal Japanese oxo producers having slightly more than 70% of Japan s total oxo capacity are Mitsubishi Kasei, Kyowa Yuka, and Japan Oxocol. 

Hydroformylation, or the 0X0 process, is the reaction of olefins with CO and H9 to make aldehydes, which may subsequently be converted to higher alcohols. The catalyst base is cobalt naph-thenate, which transforms to cobalt hydrocarbonyl in place. A rhodium complex that is more stable and mnctions at a lower temperature is also used. 

Ruthenium- and cobalt-catalyzed hydroformylation of internal and terminal alkenes in molten [PBuJBr was reported by Knifton as early as in 1987 [2]. The author described a stabilization of the active ruthenium-carbonyl complex by the ionic medium. An increased catalyst lifetime at low synthesis gas pressures and higher temperatures was observed. 

Olivier-Bourbigou s group, for example, has recently shown that phosphite ligands can be used in Rh-catalyzed hydroformylation in ionic liquids as well as the well loiown phosphine systems [81]. Since phosphite ligands are usually unstable in aqueous media, this adds (apart from the much better solubility of higher olefins in... 

In the author s group, much lower-melting benzenesulfonate, tosylate, or octyl-sulfate ionic liquids have recently been obtained in combination with imidazolium ions. These systems have been successfully applied as catalyst media for the biphasic, Rh-catalyzed hydroformylation of 1-octene [14]. The catalyst activities obtained with these systems were in all cases equal to or even higher than those found with the commonly used [BMIM][PF6]. Taking into account the much lower costs of the ionic medium, the better hydrolysis stability, and the wider disposal options relating to, for example, an octylsulfate ionic liquid in comparison to [BMIM][PF6], there is no real reason to center future hydroformylation research around hexafluorophosphate ionic liquids. 

When water-miscible ionic liquids are used as solvents, and when the products are partly or totally soluble in these ionic liquids, the addition of polar solvents, such as water, in a separation step after the reaction can make the ionic liquid more hydrophilic and facilitate the separation of the products from the ionic liquid/water mixture (Table 5.3-2, case e). This concept has been developed by Union Carbide for the hydroformylation of higher alkenes catalyzed by Rh-sulfonated phosphine ligand in the N-methylpyrrolidone (NMP)/water system. Thanks to the presence of NMP, the reaction is performed in one homogeneous phase. After the reaction. 

Higher molecular primary unbranched or low-branched alcohols are used not only for the synthesis of nonionic but also of anionic surfactants, like fatty alcohol sulfates or ether sulfates. These alcohols are produced by catalytic high-pressure hydrogenation of the methyl esters of fatty acids, obtained by a transesterification reaction of fats or fatty oils with methanol or by different procedures, like hydroformylation or the Alfol process, starting from petroleum chemical raw materials. 

Hydroformylation of Higher Molecular Weight Olefins into Primary Alcohols... 

The industrially used homogeneous catalysts for the hydroformylation of higher molecular olefins into aldehydes, which are hydrogenated to the corresponding surfactant alcohols, are cobalt carbonyl [47] or cobalt carbonylItert-phosphine complexes [48]. 

FIG. 4 Hydroformylation of higher molecular weight olefins with a cobalt carbonyl catalyst (Kuhlmann process). 

If cobalt carbonylpyridine catalyst systems are used, the formation of unbranched carboxylic acids is strongly favored not only by reaction of a-olefins but also by reaction of olefins with internal double bonds ( contrathermo-dynamic double-bond isomerization) [59]. The cobalt carbonylpyridine catalyst of the hydrocarboxylation reaction resembles the cobalt carbonyl-terf-phos-phine catalysts of the hydroformylation reaction. The reactivity of the cobalt-pyridine system in the hydrocarboxylation reaction is remarkable higher than the cobalt-phosphine system in the hydroformylation reaction, especially in the case of olefins with internal double bonds. This reaction had not found an industrial application until now. 

The linear aldehyde usually is the desired product. Often, this aldehyde is converted to the corresponding alcohol. Both Co and Rh complexes are used in hydroformylation. In general, Rh catalysts are more active and produce a higher n/wo-ratio. Co catalysts have higher... 

In the hydroformylation of lower alkenes using a modified cobalt catalyst complex separation is achieved by distillation. The ligands are high-boiling so that they remain with the heavy ends when these are removed from the alcohol product. Distillation is not possible when higher alcohols or aldehydes are produced, because of decomposition of the catalyst ligands at the higher temperatures required. Rhodium complexes can usually also be removed by distillation, since these complexes are relatively stable. 

Currently, worldwide production of aldehydes exceeds 7 million tons/year (1). Higher aldehydes are important intermediates in the synthesis of industrial solvents, biodegradable detergents, surfactants, lubricants, and other plasticizers. The process, called hydroformylation or more familiarly, the Oxo process, refers to the addition of hydrogen and the formyl group, CHO, across a double bond. Two possible isomers can be formed (linear or branched) and the linear isomer is the desired product for these applications. 

Our approach is to use the inexpensive ligands that are already used industrially as well as conventional solvents. The goal of this project is to develop a thermomorphic approach to the rhodium-catalyzed hydroformylation of higher olefins (>Ce) that enhances conversion rates and ease of product recovery while minimizing catalyst degradation and loss. 

Since it is well known that the higher the olefin, the more difficult it is to hydroformylate, we tried our approach on 1-dodecene. We found that when we used 50 50 ethanol/water (R24) and CTAB only (R33) systems they showed no activity for hydroformylation of 1-dodecene whereas, the addition of surfactant to the 50 50 ethanol/water mixture (R27) dramatically increased the reaction rate, as well as the selectivity. 

We have developed a thermomorphic catalyst system for the hydroformylation of higher alkenes. We have built a bench-scale continuous reactor and have used it to determine the long-term performance of the thermomorphic catalyst system. Longterm results (>400 h) using 1-octene and 1-dodecene show that the catalyst has high selectivity and no measurable loss in activity. 

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