Carbonyl process

In 1968 a new methanol carbonylation process using rhodium promoted with iodide as catalyst was introduced by a modest letter (35). This catalyst possessed remarkable activity and selectivity for conversion to acetic acid. Nearly quantitative yields based on methanol were obtained at atmospheric pressure and a plant was built and operated in 1970 at Texas City, Tex. The effect on the world market has been exceptional (36). 

Attempts have been made to develop methods for the production of aromatic isocyanates without the use of phosgene. None of these processes is currently in commercial use. Processes based on the reaction of carbon monoxide with aromatic nitro compounds have been examined extensively (23,27,76). The reductive carbonylation of 2,4-dinitrotoluene [121 -14-2] to toluene 2,4-diaLkylcarbamates is reported to occur in high yield at reaction temperatures of 140—180°C under 6900 kPa (1000 psi) of carbon monoxide. The resultant carbamate product distribution is noted to be a strong function of the alcohol used. Mitsui-Toatsu and Arco have disclosed a two-step reductive carbonylation process based on a cost effective selenium catalyst (22,23). 

Novel palladium catalysts show marked improvements in both yields and selectivities, compared to nickel carbonyl catalysts utilized in eadier commercial carbonylation processes (83,84). The palladium catalysts are also expected to be less hazardous. 

The carbonylation process is operated at mild temperatures (45—110°C) and elevated pressures (2—6 MPa = 20 60 atm), and can be carried out in MMA or in an inert solvent such as /V-methy1pyrro1idinone. Selectivities are claimed in excess of 99%, thereby requiring minimal purification to obtain high quahty product MMA. The principal by-product is methyl crotonate. 

Ca.rbonylProcess. Cmde nickel also can be refined to very pure nickel by the carbonyl process. The cmde nickel and carbon monoxide (qv) react at ca 100°C to form nickel carbonyl [13463-39-3] Ni(CO)4, which upon further heating to ca 200—300°C, decomposes to nickel metal and carbon monoxide. The process is highly selective because, under the operating conditions of temperature and atmospheric pressure, carbonyls of other elements that are present, eg, iron and cobalt, are not readily formed. 

In the carbonyl process, the Hquid is purified, vaporized, and rapidly heated to ca 300°C which results in the decomposition of the vapor to carbon monoxide and a fine high purity nickel powder of particle sizes <10 fim. This product is useflil for powder metallurgical appHcations (see Metallurgy, powder). Nickel carbonyl can also be decomposed in the presence of nickel powder, upon which the nickel is deposited. This process yields nickel pellets, typically about 0.8 cm dia and of >99.9 wt% purity. 

DiisononylPhthalate andDiisodeeylPhthalate. These primary plasticizers are produced by esterification of 0x0 alcohols of carbon chain length nine and ten. The 0x0 alcohols are produced through the carbonylation of alkenes (olefins). The carbonylation process (eq. 3) adds a carbon unit to an alkene chain by reaction with carbon monoxide and hydrogen with heat, pressure, and catalyst. In this way a Cg alkene is carbonylated to yield a alcohol a alkene is carbonylated to produce a C q alcohol. Due to the distribution of the C=C double bond ia the alkene and the varyiag effectiveness of certain catalysts, the position of the added carbon atom can vary and an isomer distribution is generally created ia such a reaction the nature of this distribution depends on the reaction conditions. Consequendy these alcohols are termed iso-alcohols and the subsequent phthalates iso-phthalates, an unfortunate designation ia view of possible confusion with esters of isophthaUc acid. 

Pure iron, when needed, is produced on a relatively small scale by the reduction of the pure oxide or hydroxide with hydrogen, or by the carbonyl process in which iron is heated with carbon monoxide under pressure and the Fe(CO)5 so formed decomposed at 250°C to give the powdered metal. However, it is not in the pure state but in the form of an enormous variety of steels that iron finds its most widespread uses, the world s annual production being over 700 million tonnes. 

The carbonyl process developed in 1899 by L. Mond is still used, though it is mainly of historic interest. In this the heated oxide is first reduced by the hydrogen in water gas (H2 + CO). At atmospheric pressure and a temperature around 50°C, the impure nickel is then reacted with the residual CO to give the volatile Ni(CO)4. This is passed over nucleating pellets of pure nickel at a temperature of 230°C when it decomposes, depositing nickel of 99.95% purity and leaving CO to be recycled. 

Figure 5-7. The Monsanto methanol carbonylation process for producing acetic acid. ...

CVD is not a new process. As stated in the pioneer work of Powell, Oxley, andBlocher, 1 its first practical use was developed in the 1880s in the production of incandescent lamps to i mprove the strength of filaments by coating them with carbon or metal. In the same decade, the carbonyl process was developed by Ludwig Mond and others for the production of pure nickel. A number of patents were issued during that period coveringthe basis of CVD.PI... 

CO insertion (as inferred from the nature of products), but in which the actual insertion or decarbonylation step has received at most peripheral attention. This particularly applies to industrial carbonylation processes such as hydroformylation. The interested reader is referred to several excellent articles on these subjects (30, 32, 62, 117, 198a, 203a, 228). 

Carbonylation of methanol to acetic acid is fully discussed in Chapter 9. Another carbonylation process using a phosphine ligand to control the course of the reaction is a highly atom efficient route to the widely used monomer methyl methacrylate (Scheme 4.19). In this process the catalyst is based on palladium acetate and the phosphine ligand, bisphenyl(6-methyl-2-pyridyl) phosphine. This catalyst is remarkably (>99.5%) selective for the 2-carbonylation of propyne under the relatively mild conditions of <100 °C and 60 bar pressure. 

Discuss the application of catalytic carbonylation processes in the development of green chemical technology. Highlight the application challenges that still need to be met and review current research in the area to meet these challenges. 

So far, the solid state type I reaction has been reliable only when followed by the irreversible loss of CO to yield alkyl-alkyl radical species (RP-B or BR-B) in a net de-carbonylation process. The type 11 reaction relies on the presence of a y-hydrogen that can be transferred to the carbonyl oxygen to generate the 1,4-hydroxy-biradical (BR C). The type-1 and type-11 reactions are generally favored in the excited triplet state and they often compete with each other and with other excited state decay pathways. While the radical species generated in these reactions generate complex product mixtures in solution, they tend to be highly selective in the crystalline state. 

A more complex carbonylation process is involved in the formation of bisbutenolides (bifurandiones) from cobalt carbonyl-catalyzed carbonylation of alkynes112 117 (Scheme 68). The trans derivative (53) is formed in good yield from acetylene,112 but yields from substituted acetylenes (e.g., propyne)... 

In reactions closely related to the carbonylation processes described above, the dimeric azoarene palladium complexes (78) can be transformed efficiently in two steps into 3-imino-2-phenylindazolines (Scheme 95).162... 

From the reasoning on the process level we get score 2 (no data or neutral) for the carbonylation process, since the found case was not specific to this process. For oxidation process we get score 5, since a major accident has taken place. 

The final score of the Safe Process Structure Subindex for the carbonylation process would be 2 based on this limited reasoning, since the final score of 1st is chosen on the basis of the worst case. Of course in practice one should do the reasoning on all the systems and subsystems in the process. This case study was given only to represent the principle of CBR. in reasoning the value of the Safe Process Structure Subindex. 

Though important results have already been obtained in the carbonylation of olefins, the field still remains open. Development of more active, efficient and stable catalysts based also on less expensive metals will make the carbonylation processes more attractive. Carbonylation of less common olefins, including functionalised ones, has to be explored in more depth. Other important targets are the efficient living copolymerisation, the multiple olefin insertion producing non-alternating copolymers and the selective synthesis of unsaturated products like acrylates and methacrylates. 

Exposure of the reaction mixture to reduced carbon monoxide pressure in the flash-tank has implications for catalyst stability. Since the metal catalyst exists principally as iodocarbonyl complexes (e.g. [Rh(CO)2l2] and [Rh(CO)2l4]" for the Rh system), loss of CO ligands and precipitation of insoluble metal species (e.g. Rhl3) can be problematic. It is found that catalyst solubility is enhanced at high water concentrations but this results in a more costly separation process to dry the product. The presence of water also results in occurrence of the water gas shift (WGS) reaction (Eq. 6), which can be catalysed by Rh and Ir iodocarbonyls, in competition with the desired carbonylation process, resulting in a lower utilisation of CO ... 

From a commercial viewpoint potential benefits can accrue from operating the methanol carbonylation process at low water concentration, provided that catalyst stability can be maintained. Strategies to achieve this include (i) addition of iodide salts to stabilise the Rh catalyst, (ii) heterogenisation of the Rh catalyst on a polymer support to restrict the catalyst to the reactor and (iii) replacement of Rh by a more robust Ir catalyst. These strategies, along with others for improving catalyst activity, will be discussed in the following sections. 

In 1996, BP Chemicals announced a new methanol carbonylation process, Cativa , based upon a promoted iridium/iodide catalyst which now operates on a number of plants worldwide [61-69]. Promoters, which enhance the catalytic activity, are key to the success of the iridium-based process. The mechanistic aspects of iridium-catalysed carbonylation and the role of promoters are discussed in the following sections. 

Considerable challenges still remain in the development of new carbonylation processes for acetic acid manufacture. For example, all of the current processes use iodide compounds, leading to corrosive HI and the need for expensive materials for plant construction. An iodide-free system could potentially impart considerable benefit. Other long term goals include the selective direct conversion of syn-gas or oxidative carbonylation of methane to acetic acid. Organometallic chemists are certain to play a crucial role if these targets are to be achieved. 

Another major problem in oxidative carbonylation is the presence in the reaction medium of water, which, as we have seen, is even formed as a co-product when oxygen is used as reoxidant for Cu(I) or for M(X-2). In fact, in the presence of water, competitive M-promoted oxidation processes, such as oxidation of CO to C02, may take place, which reduce the activity of the catalyst towards the desired carbonylation reaction. The oxidation of CO to C02 may be promoted by Ir(IV), Pt(IV, II), Rh(III), and especially by Pd(II), and can be stoichiometric (Eq. 8) or catalytic (working in the presence of an oxidant such as 02, Cu(II) or quinone, Eq. 9). In the case of particularly water-sensible oxidative carbonylation processes, a dehydrating agent has proven necessary to achieve acceptable catalytic efficiencies and/or product yields. Several systems have been envisaged to eliminate water, such as acetals, enol ethers,... 

Under appropriate conditions, alcohols and amines can undergo an oxidative double carbonylation process, with formation of oxalate esters (Eq. 34), oxamate esters (Eq. 35) or oxamides (Eq. 36). These reactions are usually catalyzed by Pd(II) species and take place trough the intermediate formation of bis(alkoxycarbonyl)palladium, (alkoxycarbonyl)(carbamoyl)palladium or bis(carbamoyl)palladium complexes, as shown in Scheme 29 (NuH, Nu H = alcohol or amine) [227,231,267,293-300]. 

In our laboratories, we have found that PdI2, in conjunction with an excess of iodide anions, constitutes an exceptionally efficient, selective and versatile catalyst for promoting a variety of oxidative carbonylation processes, leading to important acyclic as well as heterocylic carbonyl compounds. 

Preparation. High purity nickel can be produced through electrolytic process or by the carbonyl process. In the latter case carbon monoxide reacts at 50°C with impure Ni (or nickel-copper matte) to give the volatile tetracarbonyl from which the metal (99.9-99.99% purity) is obtained by decomposition at 200-230°C through the reaction ... 

Many of the syntheses we have seen within this review depend on the carbonylation of a vinylcarbene complex for the generation of the vinylketene species. The ease of this carbonylation process is controlled, to some degree, by the identity of the metal. The electronic characteristics of the metal will clearly have a great effect on the strength of the metal-carbon double bond, and as such this could be a regulating factor in the carbene-ketene transformation. It is interesting to note the comparative reactivity of a (vinylcarbene)chromium species with its iron analogue The former is a fairly stable species, whereas the latter has been shown to carbonylate readily to form the appropriate (vinylketene)iron complex. 

In SILP carbonylation we have introduced a new methanol carbonylation SILP Monsanto catalyst, which is different from present catalytic alcohol carbonylation technologies, by using an ionic liquid as reaction medium and by offering an efficient use of the dispersed ionic liquid-based rhodium-iodide complex catalyst phase. In perspective the introduced fixed-bed SILP carbonylation process design requires a smaller reactor size than existing technology in order to obtain the same productivity, which makes the SILP carbonylation concept potentially interesting for technical applications. 

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