CS271990B1 - Process for preparing 1-methoxy-2-propanol and apparatus for its implementation - Google Patents

Abstract

The solution relates to a method for preparing 1-methoxy-2-propanol by reacting propylene oxide with methanol in the presence of an alkali metal hydroxide as a basic catalyst at a temperature of 50 to 150 °C and a pressure of 0.5 to 2.0 MPa. Propylene oxide, methanol and catalyst are continuously fed in a molar ratio of 1:2 to 10:0.005 to 0.05 into a tubular reaction zone with removal of reaction heat and a retention time of 0.5 to 1.5 h. When using raw materials in a molar ratio of 1:2 to 7; 0.005 to 0.05 it is advantageous to carry out the process in two reaction zones with a retention time of 1/10 and 9/10 of the total retention time and in a device consisting of a dosing member, a coiled tube reactor with reaction heat removal, a connecting pipe, a tube reactor with heat supply, a pressure reducing valve and a reaction product removal. The solution can be used in the chemical industry.

Description

CS 271990 01

The present invention relates to a process for the preparation of 1-methoxy-2-propanol by reacting propylene oxide with methanol in the presence of a basic catalyst and an apparatus for its operation. 1-Methoxy-2-propanol is used as an intermediate for the production of metolachlor. The zerosures are known viaoer spfisoby his preparation. According to the oldest one, the reaction of propylene oxide with methanol is carried out in the presence of sulfuric acid to give a 3: 1 mixture of 1-methoxy-2-propanol and 2-methoxy-1-propanol in Bull. Soc. Chim. Belg. 39, 395, 1930. It is also possible to use sulfur dioxide (US 2 807 651) for the acid catalysis of the reaction of propylene oxide with methanol. The reaction of propylene oxide with methanol proceeds even in the absence of catalyst at elevated pressure and 200 ° C / ° C. Obšč. Chim. However, similar to the presence of acidic catalysts, SSSR / 14, 1038, 1944 has a distinct non-selective character. In view of their practical application, the preparation of methoxy-2-propanol, in which the reaction of propylene oxide with methanol is carried out in the presence of basic catalysts, is more interesting. The use of sodium methylate makes it possible to obtain 1-methoxy-2-propanol in a yield of up to 86% / 3. Am. Chem. Stfc ·. 72, 125, 1950 and 77, 2420, 1955; FROM. Obšč.Chim. However, the disadvantage of this method is the difficulty of working with methylate sodium and the need to conduct the process in an anhydrous environment. OP 15229 (1979) describes the preparation of 1-methoxy-2-propanol by reacting propylene oxide with methanol in a molar ratio of 1: 2 at 80 ° C and 0.5 MPa in the presence of a tertiary amine having a higher boiling point than the reaction. component at which 97.4% conversion and 93.5% selectivity are achieved. The disadvantage of these processes is that they are discontinuous (so that an uncontrolled course of reaction can occur when the reactants are metered in) and an explosion occurs as the reaction is strongly exothermic. CS 246 893 protects the preparation of 1-methoxy-2-propanol by reaction of propylene oxide with methanol at 40 to 140 ° C and a pressure of 0.1 to 5 MPa, catalytic by quaternary ammonium bases, which may be discontinuously or continually contact time of 10 minutes to 4 hours. The disadvantage of this continuous process is the very low yield (49%) of 1-methoxy-2-propanol, which is due to the low conversion of alboselectivity and the need to isolate the product from the resulting reaction mixture.

The above drawbacks are substantially eliminated by the preparation of 1-methoxy-2-propanol by the reaction of propylene oxide with methanol in the presence of a basic catalyst at a temperature of 50 to 150 ° C and a pressure of 0.5 to 2.0 MPa according to the invention. The present invention is based on the fact that propylene oxide, methanol and a basic catalyst, which is an alkali metal hydroxide, are continuously metered in a molar ratio of 1: 2 to 10: 0.005 to 0.05 in the tube reaction zone, which dissipates the reaction heat. The reaction time of the reaction mixture is 0.5 to 1.5 hours. The 1-methoxy-2-propanol is then continuously isolated from the reaction mixture. In view of the selectivity of the reaction and the yield of 1-methoxy-2-propanol, it is preferred that the process is carried out at a molar ratio of propylene oxide, methanol and alkali metal hydroxide of 1: 2 to 7: 0.005 to 0.05, but is essential for safety at work to ensure intensive removal of the reaction heat from the reaction zone. From this point of view, it is advantageous to continuously feed the reactants first into the first reaction zone equipped with intensive reaction heat removal, with a residence time of 1/10 of the total containment period from which the reaction mixture is continuously withdrawn into the second reaction zone with a 9/10 total containment time. . In the second reaction zone, the reaction mixture is reacted under the same reaction conditions, maintaining the reaction temperature with a heat loss compensating medium. The resulting reaction mixture is transferred to a continuous isolation of methoxy-2-propanol. This process can be carried out in a device according to the invention, which consists of a dosing member 1, a coil tube reactor 6, with the discharge of the reaction temperature 2> of the conduit 6, the tube reactor 5 with the heat inlet 6, the reducing valve and the discharge of the reaction product. J3.

The reactants are metered into the system continuously either individually or as a mixture prepared under cooling at a temperature below 5 ° C. An advantage of the process for the preparation of 1-methoxy-2-propanol. According to the invention, its high selectivity is manifested in a low proportion of isomeric 2-methoxy-1-propanol in the resulting reaction mixture, in high yield and purity of 1-methoxy-2-propanol prepared. The process is non-wasteful, recovered methanol is returned to the reaction. The dissipated reaction heat is used in the technological process eg for rectification of methanol. The advantages of the device according to the invention lie! especially in the safety of operation, simplicity, energy-saving, high yields and product quality. The flow characteristic of the first stage coil tube reactor with the intense removal of the resulting heat of reaction eliminates the possibility of local overheating of the reaction mixture and possible explosion, as well as the possibility of the formation of undesirable by-products such as 2-methoxy-1-propanol and higher oligomers.

The design of the device according to the invention is shown in the attached figure. *.>

The following examples illustrate, but do not limit the invention. Example 1

3.4 kg was continuously fed into the serpentine reactor using a dosing member. h ”1 propylene oxide, 13.2 kg. methanol and 0.47 kg. sodium hydroxide solution, corresponding to a molar ratio of 1: 7: 0.005, where the mixture was reacted at 130 ° C and 1.0 MPa with a stopping time of 6 min and with intensive reversal. the heat of reaction. The analysis revealed that at this stage, the reaction was carried out at 70-80%. Thereafter, the reaction mixture was passed through a connecting line 6 to a tubular reactor 5, where it was allowed to react at the same temperature and pressure and with a stopping time of 54 min. the losses were compensated by the supply of heat removed from the tubular reactor 2. The running of the plant resulted in continuous removal of the resulting reaction mixture to isolate 1-methoxy-2-proline. By operating the apparatus for 10 h, 165.4 kg of the reaction mixture was obtained with a content of 29.8% by weight. 1-methoxy-2-propanol, 2.2 wt. 2-methoxy-1-propanol, 0.42 wt. % water and 0.1 wt. of higher oligomers from which 1-methoxy-2-propanol was isolated in a yield of 90.2% with a purity of 99.4%. Example .2

The same equipment and working procedure as in Example 1 was used, except that 5.26 kg was continuously dosed. propylene oxide, 11.23 kg. methanol and 1.2 kg. . h "1 40% aqueous sodium hydroxide solution, corresponding to a molar ratio of 1: 4: 0.01. Operation of the apparatus for 28 h yielded 491.9 kg of the reaction mixture containing 43.4% by weight of 1-methoxy-2-propanol 2.8% by weight of 2-methoxy-1-propanol, 1.9% by weight of water and 0.2% by weight of higher oligomers from which 1-methoxy-2-propanol was isolated in 92.6% yield 99.5% purity

The same equipment as in Example 1 was used, to which 3.4 kg was dosed. h-1-propylene oxide, 18.8 kg. methanol, and 4.7 kg. 40% aqueous sodium hydroxide solution corresponding to a molar ratio of 1: 10: 0.05. The mixture was allowed to react at 50 ° C and 0.5 MPa while the hold time in the coil tube reactor 2 was 3 min. and drill reactor 5 27 min. Operation of the equipment for 10 h yielded 258.9 kg

Claims (3)

A process for the preparation of 1-methoxy-2-propanol by reacting propylene oxide with methanol in the presence of a basic catalyst at a temperature of 50 to 150 ° C and a pressure of 0.5 to 2.0 MPa, characterized in that propylene oxide, methanol and a basic catalyst which: is an alkali metal hydroxide continuously fed in a molar ratio of 1: 2 to 10: 0.005 to 0.05 into a tubular reaction zone from which the heat of reaction is removed, with a residence time of 0.5 to 1.5 h. 2. A process for the preparation of 1-methoxy-2-propanol according to claim 1, characterized in that propylene oxide, methanol and alkali metal hydroxide are continuously metered in in a molar ratio of 1: 2 to 7: 0.005 to 0.5 into the first reaction zone with time retention of 1/10 of the total retention time and with removal of the heat of reaction, from which the reaction mixture is continuously discharged to the second reaction zone with a retention time of 9/10 of the total retention time and with the supply of heat. 3. Apparatus for carrying out the process according to item 2, characterized in that it consists of a metering member (1), a coiled tubular reactor (2) with a reaction heat supply (3) and an outlet connected via a connecting line (4) to the tubular reactor ( 5 / with heat inlet / 6 / and outlet / 8 / of the reaction product, equipped with a reducing valve / 7 /.