Process for the preparation of 2-pyrrolidone

Abstract: This invention relates to an improved process for reacting butyrolactone and ammonia which comprises conducting the reaction in the vapor phase in the presence of a magnesium silicate catalyst to selectively produce 2-pyrrolidone in higher yield and purity.

Description: BACKGROUND OF THE INVENTION Current commercial processes for the preparation of 2-pyrrolidone (2-pyrol) are carried out at liquid phase, high pressure e.g. 1.3 x 10⁷ to 1.7 x 10⁷ Pascal above atmospheric (1900-2500 psig). This process results in a product yield of between 75 and 85 wt. %, about 10% of starting material being lost to the by-product residue which is primarily a dehydrated 2-pyrol dimer, 4-(N-pyrrolidonyl) butyramide, referred to herein as PBA. This liquid phase reaction, carried out at high temperature and pressure, is described by equations I and II. The formation of significant amounts of PBA impurity in current processes unavoidably occurs since the ratio of reaction rates of A and B are more or less fixed at a given concentration of HBA intermediate. Reduction of by-product in the mixture has been attempted by varying the temperature and pressure with little or no effect. High dilution of the reaction mixture may circumvent the problems; however, this remedy is not commercially attractive since significantly larger reactor capacity is required and added costs are incurred by diluent separation. Accordingly, it is an object of this invention to provide a process resulting in a materially improved yield and purity of 2-pyrol which is commercially feasible and economical. Another object of this invention is to minimize the formation of PBA as a major contaminant of the system. Still another object is to provide a process which eliminates the need for oversized reactor capacity. US-A-3136780 describes a vapour phase process in which butyrolactone and ammonia are reacted in the presence of an aluminium silicate clay catalyst. According to the present invention there is provided a process of reacting butyrolactone with ammonia in the vapour phase in the presence of a catalyst for a period sufficient to produce 2-pyrrolidone, characterised in that the butyrolactone is supplied to the reaction in admixture with water in a mole ratio of 5:1 to 1:2, and in that the reaction is carried out at a temperature in a range of from 225°C to 310°C under a pressure in a range from 3.45 x 10⁵ to 2.07 x 10⁶ Pascal in excess of atmospheric (between 50 psig and 300 psig) with a mole ratio of ammonia to butyrolactone in a range from 100:1 to 1:1, and with a magnesium silicate particulate catalyst which catalyst optionally contains between 0.01% and 5% by weight of elemental Ca, Cu, Ni, K, Ha or mixtures thereof and between 0.01% and 5% by weight of Cl, Br, F or SO₄ groups. The temperature of reaction is preferably between 230°C and 300°C, even more preferably between 250°C and 290°C. The pressure is preferably from 4.14 x 10⁵ to 1.38 x 10⁶ Pascal in excess of atmospheric (between 60 psig and 200 psig). In the reaction the mole ratio of NH₃ to BLO is desirably between 1:1 and 100:1, preferably between 1.1:1 and 10:1. The reaction is conveniently effected in fixed bed reactor packed with the magnesium silicate catalyst in granular form having a particle diameter of from 1.6 to 12.7mm (1/16 to 1/2 inch) or a particle size which permits a liquid hourly space velocity (LHSV) of reactants through the reactor at a rate of between 0.005 and 0.5, preferably a rate of between 0.01 and 0.1. The mole ratio of butyrolactone to water in the feed preferably lies in a range from 4:1 to 2:1. Desirably the aqueous butyrolactone is introduced into an initial contacting or preheating zone where it is reacted with ammonia to produce HBA. In the contacting zone the feed is suitably heated to pre-reaction temperature, e.g. between 190°C and 220°C. and equilibrium between HBA and BLO-NH₃ is established. To assure good mixing, and uniform heating, the contact zone can be packed with glass beads and/or other suitable inert packing material such as glass wool, steel wool, or other fiberous or particulate inert materials, although a mixing valve or impinging gas streams can also be employed, if desired. The resulting equilibrated reaction mixture is then passed into the reaction zone packed with the magnesium silicate catalyst particles maintained at the reaction temperature of between 225°C and 310°C. A preferred magnesium silicate catalyst comprises between 10 and 40 wt. % of magnesium oxide, between 40 and 80% silica and may additionally contain between 0.01 and 5% by weight of elemental calcium, copper, nickel, potassium or sodium or mixtures thereof and between 0.01% and 5% by weight of halogen or sulfate, i.e. Cl, Br, F or SO₄. This catalyst composition is ideally suited to the present process since it effects high selectivity to the production of the 2-pyrol product, e.g. above 90%, and minimizes PBA formation thus significantly reducing product entrainment in the undesirable by-product phase. Under the conditions of operation, the present catalyst has a long catalyst life in excess of 1,000 hours. Finally, the catalyst in the present system has high heat stability so that it can be easily regenerated in the presence of nitrogen and air to burn off contaminant coating at a temperature of between 300° and 500°C. more often at a temperature of from 350°C. to 450°C. However, conditions should be chosen to avoid catalyst structure alteration during regeneration. For best results, it is recommended that, when the selective conversion to 2-pyrol falls below about 90%, the feed of reactants is discontinued and the catalyst is reactivated by oxidation with an air in admixture with nitrogen diluent. In the reaction zone the butyrolactone and ammonia react in the gas phase with high selectivity to the 2-pyrol product such that yields and purity above 95% are achievable. The hot gaseous product mixture can then be passed through a cooling zone wherein it is cooled to a temperature in excess of the PBA condensation temperature, e.g. to between 100° and 200°C. depending on pressure which is usually maintained at from 68.9 to 689 kPascal above atmospheric (10 to 100 psig). The cooled mixture can then be passed to a receiver wherein excess ammonia and steam is removed as a vapor and the remaining liquid is subjected to distillation for separation from light and heavy ends which represent a significantly reduced amount of by-product. The cooling zone can be packed with glass beads, or other inert packing material as described above for the contacting zone to enhance more rapid and uniform decrease in temperature. Excess ammonia vapor and steam separated from the product mixture can be directly recycled to the ammonia feed, if desired. Having thus generally described the invention, references now had to the accompanying examples which illustrate preferred embodiments thereof but which are not to be construed as limiting to the scope of the invention as more broadly described above and in the appended claims. The following examples A through C are presented for comparative purposes and describe the operation of previous processes employing the conventional liquid phase reaction. EXAMPLES A TO C In a non-catalytic liquid phase high pressure process, operating at about 300°C. and 1.38 x 10⁷ Pascal above atmospheric (2,000 psig) butyrolactone and ammonia in a mole ratio of 1:1.1 are reacted. After one hour the reaction mixture is cooled and recovered as the product of the process. The product mixture contained 2-pyrol product together with low boiling materials which were distilled off at a temperature of about 105°C. at 40 mm Hg and heavy residue bottoms containing PBA dimer and other high boiling materials, e.g. polymer, together with some entrained product. Three separate runs were effected under the above conditions and the products analyzed by gas chromatography, high pressure liquid chromatography and Kugelrohr distillation. The results of these analysis are reported in following Tables I and IA. ANALYSIS OF CRUDE 2-PYROL SAMPLE % 2-PYROL % HEAVY MATERIAL % LIGHTS A 89.4 9.6 0.9 B 87.6 12.2 1.1 C 89.5 8.2 0.9 ANALYSIS OF 2-PYROL HEAVY MATERIAL SAMPLE % 2-PYROL DIMER OTHERS A 17% 41% 42% B 18% 40% 42% C 25% 36% 39% The following examples illustrate the process of the invention using a continuous vapor phase reaction in the presence of a magnesium silicate catalyst having the following composition: MgO = 15-20% by weight SiO₂ = 65-70% by weight Na = 1.5% by weight Cl = 0.05% by weight SO₄ = 1% by weight EXAMPLE D Into a stainless steel tubular reactor having an inner diameter of about 25.4 mm (1 inch) and a length of 914 mm (36 inches) was introduced 164 g. of the above catalyst particles of about 3.2 mm (1/8 inch) average diameter. The top 50.8 mm (2 inch) portion of the tube above the reactor nearest the BLO and ammonia feed inlets was packed with glass beads followed by a 25.4 mm (1 inch) packing of steel wool, which total 76.2 mm (3 inch) portion defines a contacting zone where feed was heated and intermixed to equilibrate the reactants. A 76.2 mm (3 inch) bottom portion below the tubular reactor was similarly packed to allow cooling of the reaction mixture exiting from the reaction zone. The reactor was purged with nitrogen gas and a heating mantle was placed around the outer surface of the reactor. In the continuous operation, an aqueous solution containing 50 weight % of BLO was introduced into the contacting zone using a precision metering piston pump. Ammonia gas was introduced separately and mixed with BLO/H₂O at a temperature of about 200°C. A BLO:NH₃ mole ratio of 1:1.1 was maintained by controlling the ammonia flow with a needle valve. The intermixed feed was then passed through the magnesium silicate packed column where at LHSV of 0.01 and a temperature of between 260° and 270°C. under a pressure of 5.17 x 10⁵ Pascal above atmospheric (75 psig), cyclization of HBA took place. The temperature in the reaction zone was maintained by the heating mantle surrounding the reaction tube. The reaction mixture exiting from the magnesium silicate fixed bed, was passed into a cooling zone packed with steel wool and glass beads wherein the temperature reduced to about 180°C. From the cooling zone, the reaction mixture was passed to a stainless steel receiver from which excess ammonia vapors were vented and wherein crude liquid product collected. The crude liquid product, at about room temperature, was then subjected to distillation for removal of heavy end by-products and the 2-pyrrolidone was analyzed for yield and purity. In the above operation, the conversion of BLO to 2-pyrrolidone was 96% and the product was above 97% pure with less than 2% of heavy residue. Product analysis was made by gas chromatography, high pressure liquid chromatography, and Kugelrohr distillation. EXAMPLES 1-9 Catalyst Screening The reaction of Example D was repeated for each of the following, except that the various catalysts shown in Table II were substituted for the magnesium silicate. Also, some of the runs were conducted in a reactor of 25.4 mm (1 inch) inner diameter and length of 305 mm (12 inches) at LHSV of 0.03 (reactor 1). The remaining runs were conducted in a reactor of 25.4 mm (1 inch) inner diameter and length of 914 mm (36 inches) at LHSV of 0.01 (reactor 2). Sample analyses were performed on a Perkin-Elmer Sigma I gas chromatograph equipped with 0.5 mm thick DB5 coated on 0.32 mm x 25 meter capillary column. The injection port and detector were set at 250°C. and oven temperature was programmed from 80° to 200°C. The results of these runs are as reported in following Table II. EXAMPLE 10 Catalyst Life In order to study the life of the catalyst, the magnesol catalyzed vapor phase process outlined in Example D was operated continuously for more than 700 hrs in reactor 2. under the conditions including a reaction temperature of 250°C.; a pressure of 5.17 x 10⁵ Pascal above atmospheric (75 psig).; feed weight ratio of BLO/Water/NH₃ of 1:1:2 and a LHSV of 0.01. The yields, measured by Glc (gas chromatograph) for 2-pyrol and PBA, are shown in Table III. MAGNESOL CATALYZED VAPOR PHASE 2-PYROL PROCESS - 25% BLO + 25% WATER + 50%NH₃ FEED Example # Run Time (Hrs.) 2-Pyrol (wt. %) PBA (wt. %) 10 a 18 98.8 -- 10 b 43 98.3 -- 10 c 72 98.1 -- 10 d 121 98.2 -- 10 e 188 97.5 -- 10 f 241 97.0 0.09 10 g 288 95.5 0.47 10 h 384 96.4 0.45 10 i 649 96.5 0.92 10 j 744 96.3 0.93 10 k 785 96.4 0.58 EXAMPLE 11 The process of Example 10 was repeated in the presence and absence of water. Thus, BLO reactant in Samples 1-6 were undiluted while in Samples 7-16 a 50/50 BLO-water mixture was employed. The results of these runs are as reported in following Table IV. Sample Feed Run Time, Hr. % BLO Conversion % Selectivity to Product % 2-Pyrol Yield 1 100% BLO 18.5 95 90.5 86.1 2 26.5 92 88 81.3 3 41.5 86 88 75.6 4 49 92 89 82.2 5 67 81 86 70 6 89.5 79 86 67.9 7 50% BLO/50% H₂O 93 80 87 69.5 8 " 97.5 82 92 75 9 " 125 94 96 90.8 10 " 142 96 95 91.3 11 " 168 98 96 93.8 12 " 184 97 97 93.6 13 " 191 96 97 92.8 14 " 207 96 96 92.2 15 " 215 96 96 92.4 16 " 231 97 96 93.1 The above data shows that by changing the feed from 100% BLO to a 50% aqueous BLO solution, the selectivity for 2-pyrol yield is dramatically increased. The experiment was carried out at 25O°C., 5.17 x 10⁵ Pascal above atmospheric (75 psig). with NH₃/BLO ratio of about 50 to 1. The improvements of selectivity by addition of water to the BLO feed was clearly demonstrated. It is to be understood that many alterations and modifications can be made in the above examples without departing from the scope of this invention. Any ratio of MgO to SiO₂ within the above ranges can be substituted in the examples to provide product in high yield and selectivity. Additionally, the process can be carried out in a batch or continuous manner without loss of product yield or quality.

Claims: A process of reacting butyrolactone with ammonia in the vapour phase in the presence of a catalyst for a period sufficient to produce 2-pyrrolidone, characterised in that the butyrolactone is supplied to the reaction in admixture with water in a mole ratio of 5:1 to 1:2, and in that the reaction is carried out at a temperature in a range from 225°C to 310°C under a pressure in a range from 3.45 c 10⁵ to 2.07 x 10⁶ Pascal in excess of atmospheric (between 50 psig and 300 psig) with a mole ratio of ammonia to butyrolactone in a range from 100:1 to 1:1, and with a magnesium silicate particulate catalyst which catalyst optionally contains between 0.01% and 5% by weight of elemental Ca, Cu, Ni, K, Na or mixtures thereof and between 0.01% and 5% by weight of Cl, Br, F or SO₄ groups. The process of claim 1 wherein said butyrolactone is reacted with said ammonia gas at a temperature between 250°C and 290°C under a pressure which is between 4.14 x 10⁵ and 1.38 x 10⁶ Pascal above atmospheric (between 60 psig and 200 psig). The process of claim 1 or claim 2 wherein the reaction is effected in a reactor packed with a fixed bed of said magnesium silicate particles and liquid hourly space velocity of reactants through the reactor is between 0.005 and 0.5. The process of claim 3 wherein the liquid hourly space velocity of reactants through the reactor is between 0.01 and 0.1. The process of any one of the preceding claims wherein said magnesium silicate particles have an average particle diameter of from 1.6mm to 12.7 (1/16 to 1/2 inch). The process of any one of the preceding claims wherein said butyrolactone is first contacted with said ammonia in a preheating zone operated at a temperature between 190°C and 220°C and said butyrolactone is introduced into said preheating zone as an aqueous solution wherein the mole ratio of butyrolactone to water is in said range from 5:1 to 1:2. The process of any one of the preceding claims wherein said mole ratio if butyrolactone to water is between 4:1 and 2:1. The process of any one of the preceding claims wherein the mole ratio of ammonia to butyrolactone is between 1.1:1 and 10:1. The process of any one of the preceding claims wherein said magnesium silicate catalyst contains between 10 wt. % and 40 wt. % of magnesium oxide and between 40 wt. % and 80 wt. % silicon oxide. The process of any one of the preceding claims wherein said reaction is effected in a continuous manner the catalyst is disposed as a particulate fixed bed and the reactants are continuously passed through said catalyst bed until the conversion of butyrolactone falls below 90% at which time the reaction is interrupted and the catalyst is reactivated. The process of claim 10 wherein the deactivated catalyst is regenerated with a nitrogen and air mixture at a temperature of from 300°C to 450°C. The process of any one of the preceding claims wherein the reaction mixture containing 2-pyrrolidone product from the reaction zone is passed to a cooling zone wherein it is cooled to a temperature above the condensation temperature of by-product PBA and any excess ammonia and steam gas is removed and is optionally recycled to the system and the product is recovered in the liquid phase. The process of claim 12 wherein the product is recovered from the liquid phase by distillation.

Inventors: LIU KOU-CHANG, TAYLOR PAUL, LIU, KOU-CHANG, TAYLOR, PAUL
Applicants: ISP INVESTMENTS INC, ISP INVESTMENTS INC.
Application year: 1989
Main classification: C07D207
IPC codes: C07D207, B01J27