DIMETHYLACETAMIDE FROM CARBONYLATION OF TRIMETHYLAMINE

Abstract: A process for producing dimethylacetamide from trimethylamine and carbon monoxide using as catalyst cobalt octacarbonyl associated with from 0.5-2.0 and prefer­ ably 0.5-1.5 moles of water per mole of cobalt octacarbonyl The reaction is carried out at 175-275°C and a pressure of from 400-4000 psi.

Description: TITLE DIMETHYLACETAMIDE FROM CARBONYLATION OF TRIMETHYLAMINE BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to reacting trimethylamine with carbon monoxide to form dimethylacetamide. Prior Art U.S. Patent 3,412,151 discloses reacting trimethylamine with carbon monoxide to form dimethylformamide at elevated pressure and temperature in the presence an amount of water about equimolar to the trimethylamine reactant using dicobalt octacarbonyl as the catalyst. Japanese Patent Publication No. 1971-43,526 discloses reacting trimethylamine with carbon monoxide to form dimethylacetamide using dicobalt carbonyl as the catalyst. Summary of the Invention The present invention relates to the discovery that when reacting trimethylamine with carbon monoxide using dicobalt octacarbonyl as the catalyst that the reaction can be effectively promoted with a hydrogen donor, such as water, while suppressing the formation of dimethylformamide by using from 0.5-2.0 moles of hydrogen donor per mole of dicobalt octacarbonyl. Detailed Description The present invention relates to the production of dimethylacetamide from trimethylamine and carbon monoxide. In accordance with the present invention from 0.5-2.0 and preferably 0.5-1.5 moles of a hydrogen donor per mole of Co2 (CO)8 is present to form the active catalyst species. Thus, when using water as the hydrogen donor, the reaction is as follows: EMI2.1 Thus CH3Co(CO)4 is the active catalyst species. This reaction has been found to depend on catalyst concentration and not CO concentration for its rate. Thus moderate pressures of as low as 400 psi (2.7 X106 pascals) can be used. While high pressures such as 4000 psi (27.5 X 106 pascals) can be used, doing so is uneconomical. The preferred pressure range is from 600-2000 psi (4.1 X 106 to 13.8 X 106 pascals). Generally the temperature used will be from 175-2750C with from 220-2500C being the preferred range. Generally the process of the present invention produces less than 4% dimethylformamide and in its preferred mode less than 2% dimethylformamide. The product dimethylacetamide is widely used as a solvent and for most of these uses the presence of more than a few percent of dimethylformamide cannot be tolerated. Thus the process of the present invention provides a process for converting trimethylamine, which normally is a waste stream generated in the production of dimethylamine, into a useful product. The process of the present invention can be performed as either a batch process or continuously. The process can be carried out neat or using a solvent. Dimethylacetamide is the preferred solvent. In a preferred aspect of the invention from 0.005-0.10 mole of a lower alkyl halide per mole of trimethyl amine is present in the reaction mixture. The preferred lower alkyl halide is methyl iodide used in a molar ratio of 0.5-2.0 moles of methyl iodide per mole of cobalt carbonyl. EXAMPLES Example 1 To a 200 ml reactor was charged 20 grams dimethylacetamide and 5 grams dicobalt octacarbonyl and 0.25 gram water in an atmosphere of nitrogen. The molar ratio of water to catalyst in this example was 0.95. The reactor was cooled to -800C, evacuated and 50 grams trimethylamine was then added. The reactor was warmed to room temperature and pressured to 1000 psi (6.9 X 106 Pa) with carbon monoxide. The vessel and contents were heated and maintained at 2500C for 6 hours. On reaching reaction temperature, carbon monoxide was added to bring the pressure to 2500 psig (17.2 X 106 Pa). After the pressure dropped to about 2300 psig (15.8 X 106 Pa) it was repressured to 2500 psig (17.2 X 106 Pa). The total amount of repressuring amounted to 2230 psig (15.4 X106 Pa). After 5 hours, CO absorption stopped. At the conclusion of the run, the reactor was cooled to room temperature and unreacted trimethylamine was vented into a cold trap maintained at -800C. Unreacted trimethylamine amounted to 4.1 grams. The remaining product was then recovered and analyzed. The liquid product amounted to 74.9 grams. Dimethylacetamide amounted to 67.6 grams for a net conversion of trimethylamine to dimethylacetamide of 92%. Dimethylformamide represented 1% of the product. This example shows the beneficial effect of water. Example 2 Example 1 was repeated but with 0.8 gram of water added to 5 grams dicobalt octacarbonyl. The molar ratio of water to catalyst in this example was 3.0. The reactor was also charged with 20 grams dimethylacetamide and 40 grams trimethylamine. The reactor was pressured to 1500 psig (10.3 X 106 Pa) with carbon monoxide at room temperature. The reaction was run at 2400C and 3500 psig (24 X 106 Pa) pressure for 2 hours. After the pressure dropped significantly the reaction was repressured to 3500 psig (24 X 106 Pa). This was done repeatedly until the total amount of repressuring amounted to 4580 psig (31.6 X 106 Pa). The product was recovered as before. Unreacted trimethylamine amounted to 5.1 grams. The liquid product amounted to 86.7 grams. Dimethylacetamide amounted to 71.5 grams for a net conversion of trimethylamine to dimethylacetamide of 85%. Dimethylformamide represented 9% of the product. This example shows the beneficial effect of a higher water/catalyst ratio on productivity but with more byproduct dimethylformamide. Example 3 Example 1 was repeated but with only 0.07 gram water added to 5 grams dicobalt octacarbonyl. The molar ratio of water to catalyst in this example was 0.3. As before, the reactor was charged with 20 grams dimethylacetamide and 40 grams trimethylamine. The reactor was pressured to 1500 psig (10.3 X 106 Pa) with CO at room temperature. The reaction was 6 run at 2500C and 3000 psig (24 X 106 Pa) pressure for 8 hours. CO absorption was complete in 4 hours. After the pressure dropped significantly, the reactor was repressured to 3000 psig (20.7 X 106 Pa). This was done repeatedly until the total amount of repressuring amounted to 2860 psig (19.7 X 106 Pa). The product was recovered as before. Unreacted trimethylamine amounted to 3.2 grams. The liquid product amounted to 69.4 grams. Dimethylacetamide amounted to 60.3 grams for a net conversion of trimethylamine to dimethylacetamide of 88%. Dimethylformamide represented 3% of the product. This example shows both lower productivity and higher byproduct formation at low water/catalyst ratios. Example 4 Example 1 was repeated but with no water added to the 5 grams of dicobalt octacarbonyl. The reactor was charged with 20 grams dimethylacetamide and 40 grams trimethylamine. The reactor was pressured to 500 psig (3.45 X 106 Pa) with CO at room temperature The reaction was run at 2500C and 2000 psig (13.8 X 106 Pa) pressure for 8 hours. After the pressure dropped significantly, the reactor was repressured to 2000 psig (18.3 X 106 Pa). This was done repeatedly until the total amount of repressuring amounted to 1450 psig (10 X 106 Pa) and was complete in 7 hours. The product was recovered as before. Unreacted trimethylamine amounted to 9.0 grams. The liquid product weighed 55.9 grams. Dimethylacetamide amounted to 44.6 grams for a net conversion of trimethylamine to dimethylacetamide of 93%. Dimethylformamide represented 3% of the product. This example shows low activity of the catalyst in the absence of water. Example 5 Example 1 was repeated with 0.3 gram of water added to 5 grams dicobalt octacarbonyl. The molar ratio of water/catalyst was 1.3. The reactor was charged with 20 grams dimethylacetamide and 40 grams trimethylamine. The reactor was pressured to 1500 psig (10.3 X 106 Pa) with CO at room temperature. The reaction was run at 2500C and an initial CO pressure of 3800 psig (26.2 X 106 Pa). There was ra n rishment of CO. Rather, in this example the pressure was allowed to decrease as CO was absorbed. After 4 hours CO absorption was complete and the final pressure was 450 psig (3.1 X 106 Pa). CO absorption totaled 3350 psig (23.1 X 106 Pa). The product was recovered as before. Unreacted trimethylamine amounted to 1.5 grams. The liquid product totaled 76.9 grams. Dimethylacetamide amounted to 70.3 grams for a net conversion of trimethylamine to dimethylacetamide of 94%. Dimethylformamide represented 2% of the product. This example shows the beneficial effect of water on productivity and yield over a range of reactor pressure. Example 6 In this example dimethylacetamide containing 50 g/gal (0.13 Kg/m2) dicobalt octacarbonyl and 2 g/gal (0.005 Kg/m2) water was fed to a 2 liter reactor at the rate of 2.4 liters/hour continuously over a 10 hour period. Trimethylamine was also fed at the rate of 1.3 lbs/hour (0.59 Kg/hour). The reactor was stirred and maintained at 2500C and 1000 psig (6.9 X 106 Pa) with carbon monoxide. Product was removed continuously through a low pressure separator. During this time, 5720 grams of trimethylamine was fed. Unreacted trimethylamine amounted to 2932 grams. The liquid product weighed 11,335 grams. Dimethylacetamide amounted to 10,219 grams for a net production of 2205 grams. Productivity was 0.73 lbs dimethylacetamide/gal/hour (53 Kg/m2/hr). Conversion of trimethylamine to dimethylacetamide was 28%. The product contained 1.8% dimethylformamide. This example shows the beneficial effect of water for a continuous reaction. Example 7 Example 1 was repeated but with some alkyl halide added with water to the catalyst. Methyl iodide (2.0 grams) was added to 0.5 gram water and 5.0 grams dicobalt octacarbonyl. The molar ratio of water/catalyst was 1.9. As before, the reactor was charged with 20 grams dimethylacetamide and 40 grams trimethylamine. The reactor was pressured to 2000 psig (13.8 X 106 Pa) with carbon monoxide at room temperature. The reaction was run at 2500C and 5000 psig (34.5 X 106 Pa) for 2 hours. CO absorption was complete after 68 minutes. After the pressure dropped significantly, the reactor was repressured to 2000 psig (13.8 X 106 Pa). This was done repeatedly until the total amount of repressuring amounted to 5640 psig (38.9 X 106 Pa) . Unreacted trimethylamine amounted to 3.7 grams. Liquid product totaled 90.5 grams. Dimethylacetamide amounted to 81.4 grams and represents a 93% conversion of trimethylamine to dimethylacetamide. Dimethylformamide represented 4% of the product. This example shows the further improvement in reaction rate resulting from methyl iodide addition with water.

Claims: CLAIMS 1. A process of producing dimethylacetamide coraining less than 4% by weight dimethylformamide by intimately contacting a reaction mixture comprising trimethylamine, carbon monoxide in the presence of a catalytic amount of dicobalt octacarbonyl and water the molar ratio of water:dicobalt octacarbonyl being from 0.5-2.0:1 at a temperature of from about 1750C to about 2750C and a pressure of from 400-4000 psig. 2. The process of Claim 1 wherein the reaction mixture further contains an alkyl halide is Iso added in a molar ratio of 0.005-0.10 alkyl halide to trimeLhylamine. 3. The process of Claim 2 wherein the alkyl halide is methyl iodide. 4. The process of Claim 3 wherein the methyl iodide is present in a molar ratio of 0.5-2.0 methyl iodide to cobalt carbonyl. 5. The process of claim 1 wherein the molar ratio of water:dicobalt octacarbonyl is from 0.5-1.5:1. 6. The process of Claim 5 wherein the temperature is from 220-250 C. 7. The process of Claim 6 wherein the pressure is 600-2000 psi.

Inventors: BELLIS, HAROLD EDWARD
Applicants: E.I. DU PONT DE NEMOURS AND COMPANY
Application year: 1984
Main classification: C07C103
IPC codes: C07B61, B01J31, C07C231, C07C67, C07C233