Deci- 30, 1958 H. T. SIEFEN ET AL " 2,866,822 LOW PRESSURE PRODUCTION OF‘ FORMAMIDES Filed ,June 27, 1956

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DISPERSION PLATE

A ca ’ INVENTORS METHYLAMINE HOWARD SIEFEN PRODUCT WILLIAM R. TRUTNA ‘2,866,822 United States Patent 0 ICC Patented Dec. 30, 1958

2 action according to the processes of the invention su?i cient pressure is employed to maintain the methylamine 2,866,822 liquid at the temperature employed. In general, a pres sure in the reaction vessel of from about 40 to 135 LOW PRESSURE PRODUCTION OF FORMAMIDES p. s. i. g. is used. More narrowly it is preferred to use Howard T. Siefen and William R. Trutna, Pasadena, Tex., from about 90 to 125 p. s. i. g. assignors to E. 1. du Pont de Nemours and Company, The carbon monoxide-methylamine reaction is speeded Wilmington, Del., a corporation of Delaware by introducing su?icient carbon monoxide into the reac tion zone to maintain in the gaseous portion of the zone Application June 27, 1956, Serial No. 594,313 10 a partial pressure of carbon monoxide of from about 25 2 Claims. (Cl. 260—561) to 100 p. s. i. g. According to processes of the invention the methyl amine is added to the body of reactants at a point near the top of the reacting body. The amount of methyl This invention relates to the production of methylform amine should be such that in the reacting body at the amides by reacting the counter-current ?ow of a methyl point of addition the concentration of methylamine is amine with carbon monoxide under a pressure of about below about 50 mol percent of the total of the methyl 40 to 135 p. s. i. g. (pounds per square inch, gauge), formamide already formed, the methylamine just added, the carbon monoxide being introduced as bubbles no and the catalysts. It is preferred that the methylamine larger than about 2 millimeters in diameter. 20 concentration should be from about 1 to 10 mol percent. A typical process and apparatus of the invention is il The mol percent of methylamine added can readily lustrated in the drawing in which there is shown semi be determined from a consideration of the re?ux rate, diagrammatically the equipment and the reactants em taking temperature into account. Alternatively the off— ployed in processes of the invention. gas can be analyzed to determine the mol percent of the In processes of the invention a methylamine corre 25 amine in the mixture near the top of the reaction body. sponding to the methylformamide desired is used as one As mentioned previously, methanol and an alkali metal reactant. Thus dimethylamine will be used to prepare di methylate are also employed in the processes of the in methylformamide and monomethylamine will be used to vention. These materials are only needed in minor produce monomethylformamide. 1n processes of the in— amounts and presumably act in the capacity of catalysts. vention there can be used any methylamine having less 30 The minimum amount of metal methylate required de than three methyl groups, in other words, mono- and di pends on the purity of the reactants since foreign matters methylamine. such as water and carbon dioxide destroy the methylate. The processes of the invention are conveniently car With pure reactants as little as 0.2% by weight of metal ried out in a vertical reaction column which is provided methylate, based on the weight of the methylamine, is at the bottom with a dispersion plate for the introduction 35 sufficient. of carbon monoxide. This plate is a conventional porous Preferably, the methanol and alkali metal methylate plate of a type made as by compressing powdered stain are used so as to provide in the reacting mass at least less steel. Instead it can be a porous carbon plate. Any 0.5% by weight of each of these materials based on the other such porous plate resistant to the reactants can be weight of the methylamine. Still more preferably, the used. 40 alkali methylate‘ is used in amounts su?icient to provide The porosity is not at all critical but the openings in the reacting mass from about 0.5% to 2% by weight should not be so large as to give bubbles of carbon based on the weight of the dimethylamine or monomethyl monoxide of greater diameter than about 2 millimeters. amine. It is preferred that the porosity be such that the bubbles _The methanol and alkali methylate are conveniently formed at the point of introduction have a diameter of 45 introduced into the reaction zone in the form of a‘ solu less than one millimeter. The smaller the bubbles the tion of the alkali metal methylate in the methanol. Thus better so long as there is no undue resistance to ?ow the total amount of methanol employed in the reaction of carbon monoxide. The equipment used must of course zone will be in the order of from about 1 to 10% .by be resistant to the reactants. ' weight based on the weight of the methylamine. Larger The processes of the invention can readily be under: 50 amounts of the methanol and methylate than mentioned stood by referring to the drawing. A methylamine is . above can be used if desired but there is no proportionate added near the top of a reaction column to a ?owing advantage in so doing. ' body of liquid which passes downwardly. The product The alkali metal methylates preferred are, of course, is withdrawn at the bottom. Carbon monoxide ?ows up the sodium and potassium methylates. Sodium methylate wardly in counter-current ?ow to the product and the 55 is most preferred for economic reasons. body of liquid reactants. Catalyst is added at an ap In carrying out this reaction, it is essential to use car~ propriate point near the top of the reactor. Off-gases bon monoxide that contains no substantial amounts of from the reaction pass out the reactor near the top and carbon dioxide and water. We have found that the intro pass through a condenser which returns re?ux to the re duction of either carbon dioxide or water into the reaction action. 60 mass decreases the reaction rate approximately in direct The processes of the invention can be readily carried proportion to the amount of these materials present. out at relatively low temperatures and pressures to give The total amount of carbon dioxide plus water that can close to theoretical yields of methylformamide. In gen be tolerated in the reaction area depends upon the amount eral, a temperature in the range of about 20° C. to 160° of alkali metal methylate present. On a mol basis, the C. can be employed. Temperatures somewhat outside 65 ratio of methylate to carbon dioxide plus water must be these ranges are operable but are less desirable. At the greater than 1. At a ratio of 1 or less, no appreciable lower temperatures, the reaction rate decreases; above reaction takes place. To carry on the reaction at a rea about 130° C. unnecessarily high pressures result re sonable rate using the preferred amount of methylate, quiring more complicated and expensive equipment. Pref namely about 0.5% to 2% based on the weight of the erably, the reaction is carried out at a temperature in the 70 methylamine, the mol ratio of methylate to carbon di range of about 60 to 130° C. oxide plus water should be at least 2, and preferably is In carrying out the carbon monoxide-methylamine re over 3. 2,866,822. 3 4 Dimethylformatnide or monomethylformamide, the de A process as just described using like amounts of mono sired products of the carbon monoxide-methylamine reac methylamine was operated to produce monomethylforma tron, are readily separated from the reaction mixture by mide. ' distillation. Flash distillation at either atmospheric or We claim: reduced pressure is a satisfactory method for separating‘ 5 1. In a process for the production of methylformamides, the product from inorganic salts in the reaction mixture. the steps comprising effecting reaction of a methylamine Ion exchange resins can also be used to separate the salts. selected from the group consisting of methylamine and The invention is further illustrated by the following dimethylamine with carbon monoxide substantially free example. ' of carbon dioxide and water and using minor amounts of Example 10 an alkali metal methylate and methanol as a catalyst, the reaction being conducted with a downwardly ?owing body A 3-inch diameter, 7 foot long, vertically-mounted of reaction product and an upward, counter-current ?ow stainless-steel tube reactor as shown in the drawing was of the carbon monoxide, the amine being added near the equipped at its lower end with a 2% inch diameter, stain top of the reaction body, the process being conducted un less-steel dispersion disc of medium porosity for intro der the following conditions: duction of carbon monoxide. Carbon monoxide is intro duced through this dispersion disc as bubbles which have Temperature, 20 to 160° C. a diameter less than 1 millimeter. An outlet for the re Pressure, 40 to 135 p. s. i. g. moval of liquid product is provided at the bottom of the Methylamine concentration at the point of addition from 1 to 50 mol percent of the total composition at the reactor. 20 At a point four feet from the bottom of the reactor a point of addition liquid dimethylamine feed point was provided and at the the carbon monoxide being added into the body as bub upper end a catalyst feed line was provided for the in bles no larger than 2 millimeters in diameter. troduction ‘of a solution of sodium methylate in methanol. 2. In a process for the production of methylformamides, An off-gas line was provided at the top and this was 25 the steps comprising effecting reaction of a methylamine equipped with a condenser and a pressure regulator set selected from the group consisting of methylamine and to hold the pressure in the reactor at 50 p. s. i. g. In ad dimethylamine with carbon monoxide substantially free dition, suitable means for heating and cooling the reactor of carbon dioxide and water and using minor amounts of were provided and a liquid level gauge was attached paral an alkali metal methylate and methanol as a catalyst, lel to the reactor for the determination of the level of o the reaction being conducted with a downwardly ?owing the reaction medium. body of reaction product and an upward, counter-current A total of 15 pounds (0.205 pound mol) of dimethyl ?ow of the carbon monoxide, the amine being added near formamide, 0.111 pound (0.00205 pound mol) of sodium the top of the reaction body, the process being conducted methylate, and 0.328 pound (0.0103 pound mol) of meth under the following conditions: anol was charged to the reactor and the contents heated 35 to 70° C. while a slow stream of carbon monoxide con Temperature, 60 to 130° C. taining 0.09 percent CO, and 0.01 percent water was Pressure, 90 to 125 p. s. i. g. added through the dispersion disc. Methylamine concentration at the point of addition 1 to When the temperature reached 70° C., the carbon 10 mol percent of the total composition at the point of monoxide feed rate was increased to 6.3 pounds per hour ‘0 addition after the addition (0.266 pound mol per hour). The dimethylamine feed the carbon monoxide being added through a. dispersion was adjusted to a rate of 9.23 pounds per hour (0.205 means which introduces it into the body as bubbles no pound mol per hour) and the catalyst solution feed was larger than 1 millimeter in diameter. started at a rate of 0.111 pound per hour of sodium methylate and 0.328 pound per hour of methanol. 45 References Cited in the ?le of this patent Immediate reaction necessitated the use of cooling water UNITED STATES PATENTS to maintain the temperature at 70° C. Liquid product was continuously removed at such a ratethat the level 1,777,777 Wietzel ______- Oct. 7, 1930 was maintained at 5 feet in the reactor. The carbon FOREIGN PATENTS monoxide and traces of inert were released through the 5° 1,029,151 France ______Mar. 4, 1953 pressure regulator which maintained a pressure of 50 p. s. i. g. in the reactor. OTHER REFERENCES After two hours of operation, samples were withdrawn Fiat Final Report 925, August 30, 1946 (page 2 relied from the reactor and it was found that less than 0.5 per cent of the dimethylamine remained unconverted. This 55 on). was con?rmed by the oft-gas rate of 0.6 pound per hour of carbon monoxide. UNITED STATES PATENT OFFICE vCERTIFICATE OF CORRECTION Patent No. 2,866,822 December 30, 1958 Howard Tn Siefen et al‘,

of theItv above is hereby numbered certified patent thatrequiri error appears in the printed specification Patent should read as corrected below.ng correction and that the said Letters

Colman 3} line 41, for "0,266" read ~~ 0.226 -

(SEAL) Attest:

KARLAttesting H, AXLINEOf?cer ROBERT C. WATSON Commissioner of Patents