SU1004352A1 - Process for producing methyl methacrylate - Google Patents

Description

The result is a method for producing methyl methacrylate by alcoholizing methacrylamide with methanol at 150–200 and a pressure of 1–5 MPa in the presence of lead-containing compounds as a catalyst. The process is carried out with the continuous removal of ammonia formed in the process by passing nitrogen through the reactor. The yield of the target product is 44-65% of the starting material and 86-91% of the reacted methacrylamide 4. A disadvantage of the known method is ;; 1 The selectivity of the formation of the target product is low. The aim of the invention is to increase the selectivity of the process. The goal is achieved by the method of producing methyl methacrylate by methacrylamide alcoholism with methanol at 150-200 ° C in the presence of lead-containing compounds, after the alcoholysis ammonia, methyl methacrylate and methanol are distilled off, and then re-alcoholization is added to the bottom residue methacrylate amide in an amount equivalent to; the methyl methacrylate removed and the initial amount of methanol. It was established that simultaneously with the main resection of alcoholysis, a side reaction of the addition of the double bond of the starting methacrylamide and the methyl methacrylate formed to the formation of amines takes place during the reaction of ammonia. In this case, initially, double connection is added to the introduction of ammonia in the main reaction. Primary amines are formed. They, in turn, also join along the double bonds of the starting methacrylamide and methacrylate to form secondary gallins. Removal of ammonia by purging the reaction mixture with nitrogen, used in a known method for. Improving the selectivity of the conversion of methacrylamides to methyl methacrylate cannot completely prevent the addition of ammonia via double bonds. The selectivity is not high enough to exceed 91%, achieved in the known method illustrates this fact. At the same time, it appears that if the process is carried out in the presence of already formed C1min methacrylamide is completely converted into methyl methacrylate. TaKigit way, the goal is achieved by the fact that methacrylamide alcoholysis with methanol is carried out in the presence of previously obtained amines. For this purpose, the alcoholysis is distilled ammonia, and then unreacted methanol and the resulting methyl methacrylate, forming an azeotropic mixture. The residue in the cube is unreacted methacrylamide and a mixture of amines, which is a by-product of the reaction. Methacrylamide is added to this residue in an amount equivalent to the methyl methacrylate removed, and the required amount of methanol. Methyl methacrylate is again synthesized and ammonia, methanol and methyl methacrylate obtained are again distilled. The introduction of these quantities of reagents is due to the fact that when adding larger amounts of methacrylamide than methylmethacrylate distilled (in mol), the equilibrium in the system is disturbed, the yield of methyl methacrylate is reduced. A part of the added methacrylamide is in this case converted into amines until a new equilibrium is reached. By adding smaller amounts of retacrylamide, the productivity of the process is reduced compared to the optimum. At steady state, the same amount of methacrylamide is added in each operation. Methanol is added in the same amount after each distillation to maintain steady-state equilibrium between the amide and ester groups in the reaction mixture (Examples 1-3). Methanolysis of methacrylamide in the presence of metal compounds with the formation of methyl methacrylate can practically be carried out in the temperature range of 150-200s. Lower speed1 | The process is very small. Above are the processes of thermal decomposition of methacrylamide. The catalyst for the metamolysis of methacrylamide can be oxides and salts of various metals, such as Pb, Cd, Mn, Co, etc. Lead-containing compounds are most effective. It should be noted that while in the known method for carrying out a new operation it is necessary to add a new portion of j | catalyzing the process, in the proposed method, this is not necessary, since the catalyst together with amines goes from the operation of coperration. The interaction of methacrylamide with methanol is carried out by heating their mixture with catalytic amounts of lead-containing compounds in an open reactor (250 ml). EXAMPLE 1: 8.51 g (0.1 mol) of methacrylamide, 32.04 g (1 mol) of metaiol, 0.33 g (0.001 mol) of acetate; pigment (P); for 3 h at 200 ° C. In the reaction mixture, after cooling, 2.04 g (0.024 mol) of methacrylschide and 4.90 g (0.049 mol) of methyl methacrylate (MMA) were detected by chromatography. The yield of methyl methacrylate is 49% of the initial and 65% of the reacted methacrylamide. Reactionary

The mixture is heated first in a water bath, and at the end in an oil bath at a temperature not higher. Stripping is continued for 2 hours. After removal of ammonia (0.51 g), 34.9 g of a mixture of methanol and methyl methacrylate (14.0% by weight of MMA, 4.9 g) are obtained, b.p. (azeotropic mixture) 64 ,, p 1.3440. Example2. To the residue of the reaction mixture obtained in Example 1 after distillation of methyl methacrylate with a meta-NOL containing 0.024 mol of methacrylamide, 0.027 mol of gshins (in terms of methacrylate residues), resulting from the addition of hyimiacs over double: Cm. methacrylamide and methyl methacrylate, and 0.001 mol of lead salt, was added 4.17 g (0.049 mol) of methacrylamide and 32.04 g (1 mol) of methanol. The mixture is heated for 3 hours at and analyzed as in Example 1. 2.10 g (0.025 mol) of methacrylamide and 4.82 g (0.048 mol) of methyl methacrylate were found. The yield of methyl methacrylate is 66% of the total methacrylamide present, 98% of the added methacrylamide and 99% of the reacted. The distillation, which is no longer than 3 hours, is carried out as in Example 1. After removal of ammonia (0.81 g), 35.3 g of an azeotropic mixture of methanol and methyl methacrylate (13.6% by weight of MMA, 4.8 g) are obtained, 3436.

Example To the residue of the reaction mixture from example 2, containing methacrylhydride, amines and lead salt 0.025; 0.027 and 0.001 mol, respectively, 4.10 g (0.048 mol3 of methacrylamide and 32.04 g (1 mol) of methanol are added. The mixture is heated for 3 hours at 200 and analyzed as in Example 1. Found 2.27 g (0-, 027 mol) methacrylamide; a and 4.64 g (0.046 mol) of methyl methacrylate. The yield of methyl methacrylate is 63% of the total methacrylamide present, 96% of the added methacrylamide and 100% of the reacted. Distillation after removal of ammonia (0.78 g) is obtained 35.2 g of a mixture of methanol and methyl methacrylate (13.2 wt.% MAA, 4.6 g), 1.3431.

PRI me R 4, (comparative). Adding to the product obtained in the same manner as in Example 1, 5.04 g (0.059 mol) of methacrylamide (instead of 4.17 g (0.049 mol) added in Example 2), and carrying out the experiment under the conditions of Example 2, it was found in the reaction mixture, 2.64 g (0.031 mol) of methacrylamide and 4.91 g (0.049 mol) of methyl methacrylate, which accounts for 59% of the presence of edema, 83% of the added and 94% of the reacted.

Example 5 (comparative). Adding to the product obtained under the conditions of example 1, 3.32 g (0.039 mol) of methacrylamide and carrying out the reaction under the conditions of example 2 results in a total of 4 22 g (0.042 mol) of methyl methacrylate.

Primarib-8. Synthesis of pro-. water as in example 1, but at other temperatures: 150, 170 and 225С. The yield of methyl methacrylate relative to the starting (and reacted) methacrylamide (MAA) is 33 (71), 40 (68) and 50 (63)%, respectively. After the distillation of ammonia, methanol, and methyl methacrylate, in each case, is added to the residue of the mixture. in example 2, the calculated amount of methacrylamide and methanol, equivalent to the amounts of distilled methyl methacrylate and methanol, is heated for 3 hours at the indicated temperatures. To the obtained after distillation, carried out as in Example 2, the mixture is once again added to the calculated amount of methacrylamide and methanol and heated for 3 hours. The outputs of methyl methacrylate after the two recycles are shown in Table. one.

Primers 9-12. Syntheses are carried out as in Example 1, but in the presence of other catalysts: lead oxide (P); Kadali, manganese, and cobalt acetates, taken in equal amounts (per mole).

The yield of methyl methacrylate with respect to the initial (and the reacted methacrylamide is 48 (65), 41 (63), 38 (64) and 35 (65)%, respectively. After two recycles, as in examples 2 and 3), the results are are listed in Table 2.

Using the proposed method for producing methyl methacrylate provides the following advantages: carrying out methanolysis of methacrylamide in the presence of an equilibrium concentration of amines makes it possible to completely convert methacrylamide to methyl methacrylate in a practically quantitative yield based on the reacted amide} the methanolysis of methacrylamide compared to the prototype simplifies the process of removing the amylase of methacrylamide compared to the prototype, as it removes the need to remove amolamide methanolysis of methacrylamide compared to the prototype, as it removes the need to remove amolamide. methyl methacrylate synthesis.

Claims (1)

The claims of the method of obtaining methyl methacrylate! 50 methacrylamide alcoholysis with methanol at 150-200 ° С in the presence of lead-containing compounds, which is due to the fact that, in order to increase the selectivity of the process, ammonia, methyl methacrylate and methanol are distilled off after alcoholysis, and then alcoholysis is repeated, adding to the vat residue of methacrylamide in an amount equivalent to the removed methyl methacrylate, and the initial amount of methanol. VNIIIPI. Order 1788/29