Methyl formate from methanol

The mechanism of formation of methyl formate from methanol and carbon monoxide in the presence of DBU has been investigated (77NKK457). In the resulting equilibrium, the rate of formation of methyl formate was found to be first order with respect to the carbon monoxide pressure and to the concentrations of methanol and DBU. 

Tronconi, E., Ebni, A., Ferlazzo, N., et al. (1987). Methyl formate from methanol oxidation over CO-precipitated V-Ti-O catalysts, Ind Eng. Chem. Res., 26, pp. 1269-1275. 

Production of methyl formate from methanol also leads to the potential produetion of formic acid from methanol [87]. Formic acid is produced commercially as a side produet of the liquid-phase oxidation of w-butane to acetic acid. It has been suggested, however, that new formie acid capacity will best be obtained by hydrolysis of methyl formate because of raw material costs [87]. The methyl formate could be produeed by either the carbonylation or dehydration of methanol according to the technologies discussed previously. 

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) ... 

Even though form amide was synthesized as early as 1863 by W. A. Hoffmann from ethyl formate [109-94-4] and ammonia, it only became accessible on a large scale, and thus iadustrially important, after development of high pressure production technology. In the 1990s, form amide is mainly manufactured either by direct synthesis from carbon monoxide and ammonia, or more importandy ia a two-stage process by reaction of methyl formate (from carbon monoxide and methanol) with ammonia. 

Thus, while water is an indispensable ingredient for the organic cycle (1 and 5), a high concentration of water causes the major loss of one of the feedstocks. Water is also made in situ together with methyl acetate from methanol and acetic acid. Not only water, but also HI is the cause of by-product formation ... 

The two catalyst components are rhodium and iodide, which can be added in many forms. A large excess of iodide may be present. Rhodium is present as the anionic species RhI2(CO)2. Typically the rhodium concentration is 10 mM and the iodide concentration is 1.5 M, of which 20% occurs in the form of salts. The temperature is about 180 °C and the pressure is 50 bar. The methyl iodide formation from methanol is almost complete, which makes the reaction rate also practically independent of the methanol concentration. In other words, at any conversion level (except for very low methanol levels) the production rate is the same. For a continuous reactor this has the advantage that it can be operated at a high conversion level. As a result the required separation of methanol, methyl acetate, methyl iodide, and rhodium iodide from the product acetic acid is much easier. 

Usually, high-purity CO is manufactured on a large scale by means of costly cryogenic separation or absorption from syngas. The above approach could be attractive for small production. Also based on Equations 14 and 15, an easy source of oxogas (C0 H2 = 1 1) can be imagined. Indeed, we could demonstrate that methyl formate and methanol can be used to hydroformylate olefins in good yields and selectivities (37). 

Hanst, P. L., and E. R. Stephens, Infrared Analysis of Engine Exhausts Methyl Nitrite Formation from Methanol Fuel, Spectroscopy, 4, 33-38 (1989). 

Although the data of Herrero et al. [34] were interpreted in terms of a parallel reaction scheme model, such a model is certainly not established by their treatment, and Vielstich and Xia [36] have criticised such a model on the basis of their Differential Electrochemical Mass Spectroscopy (DEMS) data [37]. At least below a potential of 420 mV, the very sensitive DEMS technique detects no C02 evolved from a polycrystalline particulate Pt electrode surface on chemisorption of methanol indeed, the only product detected other than adsorbed CO, in very small yield (one or two orders of magnitude smaller), is methyl formate from the intermediate oxidation product HCOOH. This is graphically illustrated in Fig. 18.2 in which the clean electrode is maintained at 50 mV, a 0.2M methanol/O.lM HCIO4 electrolyte introduced, and the electrode swept at 10 mV s I anod-... 

EXAMPLE Acid-catalyzed formation of methyl benzoate from methanol and benzoic acid. Part 1 Acid-catalyzed addition of methanol to the carbonyl group. 

Methyl acetate from methanol and acetic acid General process for ester formation... 

Of great industrial interest is the direct reduction of CO by hydrogei thu giving alcohols. Feder and Rathke describe the formation of methanol and methyl formate from CO/Hj using HCo(CO)4 as catalyst (81J. They invoke -HCO as an intermediate. Fachinetti postulates (31 > as a potential intermediate )82]. 

Teder and Rathke describe ihe synthesis of methanol and methyl formate from CO/H2 using Co2(CO)4 as catalyst [5]. 

Surface-bound methoxy, CH3O, is an intermediate in a variety of surface processes in catalysis and electrocatalysis involving methanol. The chemistry of methoxy on Pt(lll) and the Sn-alloys had been elusive because of the difficulty of cleanly preparing adsorbed layers of methoxy. One approach is to use the thermal dissociation of an adsorbed precursor, methyl nitrite (CH O-NO), to produce methoxy species on such surfaces at temperatures lower than required for methoxy formation from methanol [58, 59]. The methoxy intermediate is strongly stabilized (to 300 K) against thermal decomposition on both Sn/Pt(lll) alloys, whereas on Pt(lll), dissociation occurs below 140 K. There is a high selectivity to formaldehyde, CHjO, on both alloys, i.e., methoxy disproportionates to make equal amounts of formaldehyde and methanol. The two Sn/Pt(lll) alloys do not form CO and products characteristic of methoxy decomposition on Pt(l 11). 

Although we have been able to demonstrate that methyl formate is derived directly from carbon dioxide, it is possible, employing the same metal carbonyl catalyst precursors, to catalyze the production of methyl formate from the reaction of CO and methanol (Equation 9). 

EXAMPLE Acid-catalyzed formation of methyl benzoate from methanol and benzoic acid. 

Ag-SrTiOs photocatalysts prepared by hydrothermal method showed activity in the reduction of CO2 to methyl formate in methanol under UV irradiation [50]. Further modification with niobia led to solid (AgNb03)i (SrTi03) solutions that showed a bandgap from 3.21 to 2.65 eV when x decreased from 1 to 0 [51]. 

Fig. 10.27. Differential distillation technique (SATSVA] curve for products of photolysis of poly(methyl acrylate) (a) carbon dioxide (b) formaldehyde (c) methyl formate (d) methanol (e) water and (f) short chain fragments [1450]. (Reproduced with permission from [1450] published by Elsevier Science Publishers Ltd, 1985.)...

Anhydrous, monomeric formaldehyde is not available commercially. The pure, dry gas is relatively stable at 80—100°C but slowly polymerizes at lower temperatures. Traces of polar impurities such as acids, alkahes, and water greatly accelerate the polymerization. When Hquid formaldehyde is warmed to room temperature in a sealed ampul, it polymerizes rapidly with evolution of heat (63 kj /mol or 15.05 kcal/mol). Uncatalyzed decomposition is very slow below 300°C extrapolation of kinetic data (32) to 400°C indicates that the rate of decomposition is ca 0.44%/min at 101 kPa (1 atm). The main products ate CO and H2. Metals such as platinum (33), copper (34), and chromia and alumina (35) also catalyze the formation of methanol, methyl formate, formic acid, carbon dioxide, and methane. Trace levels of formaldehyde found in urban atmospheres are readily photo-oxidized to carbon dioxide the half-life ranges from 35—50 minutes (36). 

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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