Carbonylation process chemistry

Some Important Features of Carbonylation Process Chemistry... 

In common with many catalysed reactions, the important features of carbonylation process chemistry may be associated with different aspects of the catalytic cyde. Broadly, process activity may vary either because (i) more of the catalyst is present in the active form, (ii) the activity of the catalyst in the active form is enhanced or inhibited or, less commonly, (iii) the rate controlling step does not involve the catalyst. The process selectivity may vary because of side reactions (i) occurring through the active catalyst cycle, (ii) involving inactive catalyst, or (iii) taking place because of the organic chemistry of the systems. Examples of all these contributions to overall process effidency are found in the various commerdal carbonylation processes. 

A recent example of a product that is demanding in terms of process chemistry is a new herbicide from BASF. The seven-step synthesis requires bromination, chlorination, carbonylation, oxydation (with H2O2), hydrogenation, and a reaction with ethylene. As no fine-chemical manufacturer was in a position to offer the whole range of process technologies, the manufacture will be split between two fine-chemical companies. 

In this chapter, the recent advances in amidocarbonylations, cyclohydrocarbonylations, aminocarbonylations, cascade carbonylative cyclizations, carbonylative ring-expansion reactions, thiocarbonylations, and related reactions are reviewed and the scope and mechanisms of these reactions are discussed. It is clear that these carbonylation reactions play important roles in synthetic organic chemistry as well as organometallic chemistry. Some of the reactions have already been used in industrial processes and many others have high potential to become commercial processes in the future. The use of microwave irradiation and substitutes of carbon monoxide has made carbonylation processes suitable for combinatorial chemistry and laboratory syntheses without using carbon monoxide gas. The use of non-conventional reaction media such as SCCO2 and ionic liquids makes product separation and catalyst recovery/reuse easier. Thus, these processes can be operated in an environmentally friendly manner. Judging from the innovative developments in various carbonylations in the last decade, it is easy to anticipate that newer and creative advances will be made in the next decade in carbonylation reactions and processes. 

One of the most remarkable recent advances in metal carbonyl substitution chemistry has been the discovery by Coville and co-workers of the homogeneous and heterogeneous catalytic labilization of the metal-carbon bond in metal-carbonyl complexes (26-31). Considering that restrictions to catalysis involving metal carbonyl species can, in some instances, be related to the strength of the metal-carbon bond, these discoveries could have far-reaching implications. To exemplify these catalytic substitution processes, comparisons in the systems M(CO)6(M = Cr, Mo, W), CpMoI(CO)3, CpFeI(CO)2, Fe(CO)5, Fe(CO)4(olefin), and Ir4(CO)12 will be made. 

The utilization of rhodium-phosphine complexes in homogeneous catalysis is widespread and encompasses industrially important processes, hydroformylation see Hydroformyla-tion) being one of the most widely known rhodium-mediated conversions see Rhodium Organometallic Chemistry and Carbonylation Processes by Homogeneous Catalysis).It... 

Carbides Transition Metal Solid-state Chemistry Carbon FuUerenes Carbonyl Complexes of the Transition Metals Carbonylation Processes by Homogeneons Catalysis Cyanide Complexes of the Transition Metals Intercalation Chemistry. 

Based in part on the article Carbonylation Processes by Homogeneous Catalysis by George G. Stanley which appeared in the Encyclopedia of Inorganic Chemistry, First Edition. 

The production of carboxylic acids via carbonylation catalysis is the second most important industrial homogeneous group of processes. Reppe developed most of the basic carbonylation chemistry in the 1930s and 1940s. The first commercial carbonylation process was the stoichiometric Ni(CO)4-based hydroxycarbonylation of acetylene to give acrylic acid (see Section 3.5 for details). This discovery has since evolved into a trae Ni-catalyzed process, used mainly by BASF. The introduction of rhodium catalysts in the 1970s revolutionized carboxylic acid production, particularly for acetic acid, much in the same way that Rh/PPhs catalysts changed the importance of hydroformylation catalysis. 

The reaction of an aUcene (or aUcyne), CO, and H2O to directly produce a carboxylic acid is called Reppe carbony-lation chemistry or, more recently, hydrocarboxylation (see Reppe Reaction). An excellent review of palladium-catalyzed Reppe carbonylation systems has been published recently by Kiss, and coverage of this important material will not be repeated here. This catalytic reaction has been known for quite some time, although the stoichiometric Ni(CO)4-based carbonylation of acetylene was the first commercial carbonylation process implemented (equation 13). The extreme toxicity of Ni(CO)4, however, has limited practical applications (see Nickel Organometallic Chemistry). Co, Rh, and Pd catalysts have certainly replaced Ni(CO)4 in smaller-scale laboratory reactions, though for historical reasons a number of the fim-damental mechanisms discussed in this section are based on Ni(CO)4. 

Carbonylation Processes by Homogeneous Catalysis Coordination Chemistry History Coordination Numbers Geometries Iron Organometallic Chemistry Manganese Organometallic Chemistry Nickel Organometallic Chemistry Rhodium Organometallic Chemistry. 

Unlike the hydrogenation catalysts, most iridium catalysts studied for hydroformylation chemistry are not particularly active and are usually much less active than their rhodium counterparts see Carbonylation Processes by Homogeneous Catalysis). However, this lower activity was useful in utihzing iridium complexes to study separate steps in the hydroformylation mechanism. Using iridium complexes, several steps important in the hydroformylation cycle such as alkyl migration to carbon monoxide were studied. Another carbonylation reaction in which iridum catalysis appears to be conunercially viable is in the carbonylation of methanol. ... 

Carbonylation Processes by Homogeneous Catalysis Hydrocyanation by Homogeneous Catalysis Mechanisms of Reaction of OrganometaUic Complexes Ohgomeriza-tion Polymerization by Homogeneous Catalysis Osmium Inorganic Coordination Chemistry. 

Asymmetric Synthesis by Homogeneous Catalysis Carbonylation Processes by Homogeneous Catalysis Coordination Organometalhc Chemistry Principles Electronic Stmcture of Clusters Hydride Complexes of the Transition Metals Hydrides Sohd State Transition Metal Complexes Organic Synthesis using Transition Metal Complexes Containing 7t-Bonded Ligands Oxidation... 

Since 1979, numerous reviews have appeared on the kinetics, mechanisms, and process chemistry of the metal-catalyzed methanol carbonylation reaction [11, 14-20], especially the Monsanto rhodium-catalyzed process. In this section, the traditional process chemistry as patented by Monsanto is discussed, with emphasis on some of the significant improvements that Monsanto s licensee, Celanese Chemicals (CC) has contributed to the technology. The iridium-based methanol carbonylation process recently commercialized by BP Chemicals Ltd. (BP) will be discussed also. 

The reaction chemistry of the rhodium-catalyzed methanol carbonylation process under Monsanto conditions has been investigated extensively [6-8, 10, 12, 21, 26-29] (cf Section 2.1.2.1.1). The overall reaction kinetics are first order in both rhodium catalyst and methyl iodide promoter. The reaction is zero order in methanol and zero order in carbon monoxide partial pressure above 2 atm (eq. (6)) [27]. The kinetics agree well with the basic mechanism common to the three carbonylation reactions (see Section 2.1.2.1.1 and Tables 1 and 2). 

The process chemistry of the methanol carbonylation reaction is summarized in Scheme 1. This catalytic reaction scheme depicts the balanced relationship between the methanol carbonylation, the WGSR and the iodide cycles under both regimes of water concentration. Within the scope of methanol carbonylation in an aqueous/acetic acid medium, the overall reaction rate depends not only on the nature of the rate-determining step(s), but also on reaction conditions influencing the steady-state concentration of the active Rh species, [Rh(CO)2l2]. ... 

In the 1990s, BP re-examined the iridium-catalyzed methanol carbonylation chemistry first discovered by Paulik and Roth and later defined in more detail by Forster [20]. The thrust of this research was to identify an improved methanol carbonylation process using Ir as an alternative to Rh. This re-examination by BP led to the development of a low-water iridium-catalyzed process called Cativa [20]. Several advantages were identified in this process over the Rh-catalyzed high-water Monsanto technology. In particular, the Ir catalyst provides high carbonylation rates at low water concentrations with excellent catalyst stability (less prone to precipitation). The catalyst system does not require high levels of iodide salts to stabilize the catalyst. Fewer by-products are formed, such as propionic acid and acetaldehyde condensation products which can lead to low levels of unsaturated aldehydes and heavy alkyl iodides. Also, CO efficiency is improved. 

The concept of co-carbonylation of methanol/methyl acetate mixtures was first introduced by BASF in the early 1950s, but the reaction chemistry was not fully developed to commercial realization [75]. Not until the mid-1980s, after the development of carbonylation processes to produce acetic acid and acetic anhydride, were co-carbonylation processes patented using homogeneous rhodium/iodine catalyst systems (Table 2) [2, 56]. The basic process concept is to manufacture acetic acid and acetic anhydride from methanol and carbon monoxide as the only raw materials and to generate methyl acetate within the process. Similiarly, the suitability of dimethyl ether as a raw material for the generation of the anhydride equivalent in addition to or as a substitute for methyl acetate was revealed by Hoechst [76]. To produce a small fraction of acetic acid besides acetic anhydride as the main product, the carbonylation of methyl acetate could be conducted with small amounts of water or methanol. This variant, first demonstrated by Hoechst [56], is practiced by Eastman Kodak [2]. 

A key property of catalytic processes is selectivity. Catalysis has revolutionized process chemistry by replacement of wasteful, unselective (i.e. multiple-product-forming) reactions with efficient, selective (i.e. one-product-dominating) ones. For example, selective catalytic methanol carbonylation (practiced by BP, BASF Monsanto, Eastman) has to a large extent substituted unselective non-catalytic n-butane oxidation (Celanese, and Union Carbide processes). 

G. G. Stanley (1994) Carbonylation processes by homogeneous catalysis in Encyclopedia of Inorganic Chemistry, ed. R.B. King, Wiley, Chichester, vol. 2, p. 575 - A well-referenced overview which includes hydroformylation, Monsanto and Tennessee-Eastman processes. 

As one of the fundamental bond constructions, the carbonyl-ene reaction - between an aldehyde and an alkene bearing an allylic hydrogen - attracts considerable attention [1] from the synthetic community. Given the versatile chemistry of the product homoallylic alcohols, both the intra- and intermolecular versions of asymmetric carbonyl-ene reactions are valuable processes. [2] Within the catalytic field, [3] the continuing development of chiral Lewis acids further advances the utility and scope of carbonyl-ene chemistry. We wish to highlight a number of these developments. 

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