Methanol, reaction carbonylation

Halcon has developed a new non-noble metal catalyst for methanol reductive carbonylation (32). It is formed under more moderate conditions (1200 psi, 120 C) and permits a selective reaction at only 1200-1800 psi of reaction pressure. Under these conditions, the catalyst s activity is comparable with noble metal catalyzed carbonylations. The conversion rate is 1.5-3.0 mol/l.hr. and acetaldehyde selectivity is 85%. In concentrated solutions, a considerable portion of product acetaldehyde (20-40%) is converted to its acetal. The acetal can be readily hydrolyzed back to acetaldehyde at 100-150 without catalyst (33). Acetal formation is actually beneficial through prevention of undesirable acetaldehyde condensation reactions. 

Amines are converted to isocyanates in the presence of PdCl2 (61), and methanol is carbonylated to acetic acid (62) (Reaction 17). 

Carbonyl olefination.1 The reaction of 1 with benzaldehyde results in a 1 1 separable mixture of the threo- and eryfAro-adducts (2a and 2b, respectively). The adducts undergo stereospecific ypn-elimination when heated to give /i-phenyl-thiostyrene (3). The (E)-isomer (3a) is formed from 2a, and the (Z)-isomer (3b) is formed from 2b. On the other hand, anfr -elimination obtains on treatment of 2 with perchloric acid in methanol. This carbonyl olefination has one advantage over the Peterson reaction in that intermediate adducts can be isolated and converted as desired to an (E)- or a (Z)-olefin. 

Most authors consider acetaldehyde as the primary product of methanol hydro-carbonylation which, depending on the reaction conditions and catalyst system, can be hydrogenated to yield ethanol. The potential of cobalt hydrocarbonyl to reduce aldehydes to alcohols in a homogeneous process in the presence of syngas, was recognized by Wender et al, in 1950 [78]. A mechanism according to Equations (29) and (30) was proposed involving an ethoxy cobalt imermediate. 

In order to prevent hydrogenolysis of the benzylidene group, Kalra substituted methanol in place of hydrogen other workers had previously shown that, by this modification of the oxo reaction, carbonyl insertion occurs in epoxides, with the formation of esters. - When the same substrate (75) was treated with carbon monoxide and methanol at 190 , the preponderant products were those formed by methanolysis and hydrolysis, with preponderant, tmns-diaxial opening of the epoxide, to give, in 30% yield, methyl 3-O-methyl-a-D-altropyranoside (78) and, in 26 % yield, methyl 4,6-O-benzylidene-a-D-altropyranoside (79). Part of the reaction product (15%) consisted of unchanged substrate, and there was evidence (from mass-spectral studies) that a carbonyl insertion had taken place to a very negligible extent (less than 5 %). 

Acrylonitrile and related compounds displace all the carbonyl groups from nickel carbonyl to form [(RCH CHCN)2Ni], in which the nitrile bonds through the olefinic double bond 222, 418). The bis(acrylonitrile) complex catalyzes many reactions, including the conversion of acrylonitrile and acetylene to heptatrienenitrile and the polymerization of acetylene to cyclooctatetraene 418). Cobalt carbonyl gave a brown-red amorphous material with acrylonitrile, which had i cn absorptions typical of uncoordinated nitrile groups, but interestingly, the presence of C=N groups was also indicated 419). In acidic methanol, cobalt carbonyl converts a,j8-unsaturated nitriles to saturated aldehydes 459). 

It deserves mention that related palladium-catalyzed C-C coupling cascades have been combined with a carbonylation terminating step [41]. In such cases vinyl-, alkyl- or allylpalladium(II) intermediates were generated in situ and trapped by carbonylation reactions, mainly carboxylations. As an example pelar-gonic (nonanoic) acid, an industrially interesting synthetic fatty acid, has been prepared via butadiene telomerization in the presence of methanol, subsequent carbonylation of the resulting allylic ethers and hydrogenation (eqs. (13) and (14)) [42]. 

Properties Colorless liquid. Decomposed by hot water stable to cold water. D 1.23 (15C), bp 71.4C, vapor d 3.9 (air = 1), flash p54F (12.2C). Soluble in methanol alcohol, ether, and benzene. Derivation Reaction between methanol and carbonyl chloride. 

EniChem set up a project aimed at the development of a nonphosgene synthesis of DMC for large volume usage as a result, a new industrial process was established, based on a liquid-phase methanol oxidative carbonylation in the presence of copper chlorides as catalysts. This catalytic system was highly effective in DMC production the reaction was carried out by feeding at the same time methanol, carbon monoxide, and oxygen to the suspension of the catalyst in a mixture of water, methanol, and DMC and recovering DMC by distillation after the catalyst separation. Besides, the process... 

Methanol oxy-carbonylation is a redox two-step reaction. According to a simplified scheme, the reaction proceeds through CuCl oxidation by oxygen to cupric methoxychloride [reaction (3)]. ... 

When palladium salts are used for methanol oxy-carbonylation to DMC, reaction conditions are milder than using copper only however, methanol and CO selectivities are lower owing to the formation of DM0 as a by-product and to the higher ratio between CO2 and DMC production rates. Despite the large amount of work on the catalytic systems, no process based on gas-phase direct methanol oxy-carbonylation to DMC has been established. 

Reaction of Methanol with Carbonyl Compounds. - Similar to the reaction of methanol with carboxylic acid, esters, or nitriles shown in Sections 5.2 and 6.2, attempts were made to use the HCHO which is formed by dehydrogenation of methanol. Ueda et al. performed the reaction of methanol with acetone over various transition metal catalysts supported on MgO using an acetone/methanol molar ratio of 1/10. The best performances are obtained with a catalyst containing 3.1 wt% of Fe. The main products are methyl vinyl ketone, methyl ethyl ketone, and 2-propanol. The yields are 7.1, 2.8, and 2.8 mol%, respectively, based on the charged acetone at the conversion of 20.1% selec-tivities are 34.8, 13.9, and 13.9 mol%, respectively, based on acetone. The yield of methyl vinyl ketone is much lower than that achieved in the reaction with HCHO. Unfortunately, there is no information about the reaction of methanol that exists in the feed ten times greater than acetone. It is considered that methyl ethyl ketone and 2-propanol are formed by hydrogenation of methyl vinyl ketone and acetone, respectively, with methanol. 

Compared with the carbonylation of methanol, the carbonylation of Csp3-X is relatively easier. Based on the C-X bond energy, the rate of the oxidative addition of the organic halide to an electronically unsaturated metal complex decreases along the sequence C-I > C-OTf > C-Br C-Cl C-F. In addition to (het-ero)aryl halides, alkenyl-X [52-56] and steroidal [57-62] derivatives have been successfully used as reagents in carbonylation reactions as well. 

Nickel and Other Iron Group Metal Containing Catalysts. A nickel metal catalyst supported on an activated carbon (Ni/C) exhibits an excellent activity to convert most of the methanol to carbonylated products (acetic acid and methyl acetate) selectively (29). The typical reaction conditions utilized are 300°C and 11 atm. The effects of the supports on the activity are significant. Nickel on a y-alumina or a silica gel exhibit quite low activity compared to Ni/C. The order of the activity is as follows Ni/C Ni/ y-Al203 > Ni/Si02 (30) (Table 9). Iron and cobalt on activated carbon give small amounts of carbonylated products... 

The production of another important chemical and polymer intermediate, acetic acid, was revolutionized by the Wacker process that was introduced in 1960. It was a simple, high yield process for converting ethylene to acetaldehyde, which replaced the older process based on ethanol and acetylene. In the Wacker reaction, the palladium catalyst is reduced and then reoxidized. Ethylene reacts with water and palladium chloride to produce acetaldehyde and palladium metal. The palladium metal is reoxidized by reaction with cupric chloride, which is regenerated by reaction with o gen and hydrochloric acid. In 1968, BASF commercialized an acetic acid process based on the reaction of carbon monoxide and methanol, using carbonyl cobalt promoted with an iodide ion (74). Two years later, however, Monsanto scored a major success with its rhodium salt catalyst with methyl iodide promoter. Developed by James F. Roth, this new catalyst allowed operation at much milder conditions (180°C, 30-40 atm) and demonstrated high selectivity for acetic acid (75). 

Methanol is first carbonylated to methyl formate, which is then hydrogenated to form twice the amoimt of methanol. The carbonylation reaction proceeds in the liquid phase in the presence of sodium or potassium methoxide (NaOCH3 or KOCH3) as a homogeneous catalyst. This fine-timed industrial technology is used in the production of formic acid. Recently, the possibility of efficient use of heterogeneous catalysts was demonstrated. The... 

Hydroformylation and Related Carbonylation Reactions.—Reviews on the synthesis of commercially important organic intermediates via rhodium-catalysed hydroformylation reactions, carbonylations with triarylphosphine-palladium catalysts, diene carbonylations, and heterogenized rhodium catalysts for methanol carbonylation have been published. 

Low pressure methanol carbonylation transformed the market because of lower cost raw materials, gender, lower cost operating conditions, and higher yields. Reaction temperatures are 150—200°C and the reaction is conducted at 3.3—6.6 MPa (33—65 atm). The chief efficiency loss is conversion of carbon monoxide to CO2 and H2 through a water-gas shift as shown. 

About half of the wodd production comes from methanol carbonylation and about one-third from acetaldehyde oxidation. Another tenth of the wodd capacity can be attributed to butane—naphtha Hquid-phase oxidation. Appreciable quantities of acetic acid are recovered from reactions involving peracetic acid. Precise statistics on acetic acid production are compHcated by recycling of acid from cellulose acetate and poly(vinyl alcohol) production. Acetic acid that is by-product from peracetic acid [79-21-0] is normally designated as virgin acid, yet acid from hydrolysis of cellulose acetate or poly(vinyl acetate) is designated recycle acid. Indeterrninate quantities of acetic acid are coproduced with acetic anhydride from coal-based carbon monoxide and unknown amounts are bartered or exchanged between corporations as a device to lessen transport costs. 

Methyl Acetate Garbonylation. Anhydride can be made by carbonylation of methyl acetate [79-20-9] (28) in a manner analogous to methanol carbonylation to acetic acid. Methanol acetylation is an essential first step in anhydride manufacture by carbonylation. See Figure 1. The reactions are... 

The reaction mechanism and rates of methyl acetate carbonylation are not fully understood. In the nickel-cataly2ed reaction, rate constants for formation of methyl acetate from methanol, formation of dimethyl ether, and carbonylation of dimethyl ether have been reported, as well as their sensitivity to partial pressure of the reactants (32). For the rhodium chloride [10049-07-7] cataly2ed reaction, methyl acetate carbonylation is considered to go through formation of ethyUdene diacetate (33) ... 

The first anhydride plant in actual operation using methyl acetate carbonylation was at Kingsport, Tennessee (41). A general description has been given (42) indicating that about 900 tons of coal are processed daily in Texaco gasifiers. Carbon monoxide is used to make 227,000 t/yr of anhydride from 177,000 t/yr of methyl acetate 166,000 t/yr of methanol is generated. Infrared spectroscopy has been used to foUow the apparent reaction mechanism (43). 

The unit has virtually the same flow sheet (see Fig. 2) as that of methanol carbonylation to acetic acid (qv). Any water present in the methyl acetate feed is destroyed by recycle anhydride. Water impairs the catalyst. Carbonylation occurs in a sparged reactor, fitted with baffles to diminish entrainment of the catalyst-rich Hquid. Carbon monoxide is introduced at about 15—18 MPa from centrifugal, multistage compressors. Gaseous dimethyl ether from the reactor is recycled with the CO and occasional injections of methyl iodide and methyl acetate may be introduced. Near the end of the life of a catalyst charge, additional rhodium chloride, with or without a ligand, can be put into the system to increase anhydride production based on net noble metal introduced. The reaction is exothermic, thus no heat need be added and surplus heat can be recovered as low pressure steam. 

Acetic Acid and Anhydride. Synthesis of acetic acid by carbonylation of methanol is another important homogeneous catalytic reaction. The Monsanto acetic acid process developed in the late 1960s is the best known variant of the process. 

Coproductioa of ammonium sulfate is a disadvantage of the formamide route, and it has largely been supplanted by processes based on the direct hydrolysis of methyl formate. If the methanol is recycled to the carbonylation step the stoichiometry corresponds to the production of formic acid by hydration of carbon monoxide, a reaction which is too thermodynamicaHy unfavorable to be carried out directly on an iadustrial scale. 

There are two processes used commercially for DMF manufacture. A two-step process iavolves carbonylation of methanol [67-56-1] to methyl formate [107-31 -3] and reaction of the formate with dimethylamine. 

The methanol carbonylation is performed ia the presence of a basic catalyst such as sodium methoxide and the product isolated by distillation. In one continuous commercial process (6) the methyl formate and dimethylamine react at 350 kPa (3.46 atm) and from 110 to 120°C to effect a conversion of about 90%. The reaction mixture is then fed to a reactor—stripper operating at about 275 kPa (2.7 atm), where the reaction is completed and DMF and methanol are separated from the lighter by-products. The cmde material is then purified ia a separate distillation column operating at atmospheric pressure. 

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