Process for preparing MMA in high yields

Abstract

A process for preparing methyl methacrylate by direct oxidative esterification of methacrolein has elevated yields compared to known processes. Methyl methacrylate (MMA) is used in large amounts for preparing polymers and copolymers with other polymerizable compounds. In addition, methyl methacrylate is an important synthesis unit for a variety of specialty esters based on methacrylic acid (MAA), which can be produced by transesterification with the appropriate alcohol. There is consequently a great interest in very simple, economic, and environmentally friendly processes for preparing methyl methacrylate. A superior workup of the reactor output from the oxidative esterification of methacrolein allows specific by-products to be isolated and then additionally converted to alkyl methacrylates, especially to MMA.

Claims

1. A process for preparing alkyl methacrylates, comprising: preparing methacrolein in a first reaction stage in a reactor I, and oxidatively esterifying the methacrolein with an alcohol in a second reaction stage in a reactor II to give an alkyl methacrylate, wherein a. a reactor output from reactor II is separated into a first fraction containing a predominant portion of the alkyl methacrylate and a second fraction containing methacrylic acid and an alkyl alkoxyisobutyrate, and b. the second fraction is converted in a reactor III in such a way that further alkyl methacrylate is formed from the alkyl alkoxyisobutyrate and the methacrylic acid.

2. The process according to claim 1, wherein the separation in step a is effected by at least an extraction and/or a distillation.

3. The process according to claim 1, wherein the reaction in step b is conducted at a temperature equal to or higher than a temperature of the oxidative reaction in reactor II.

4. The process according to claim 1, wherein the reaction in step b is conducted with a reaction mixture comprising the alkyl alkoxyisobutyrate, the methacrylic acid, dimeric methacrolein (DIMAL) as a by-product from reactor II, one or more derivatives of dimeric methacrolein as a by-product from reactor II, water, and free alcohol, wherein the free alcohol is optionally added from a separate feed.

5. The process according to claim 1, wherein the second fraction is reacted in reactor III at a temperature of at least 90° C.

6. The process according to claim 1, wherein the second fraction is reacted in reactor III in step b in the presence of a catalyst.

7. The process according to claim 1, wherein step a comprises freeing the reactor output from reactor II of methacrolein and partly of the alcohol in a first distillation column, to obtain a stream comprising: alkyl methacrylate, water, methacrylic acid and/or an alkali metal methacrylate obtained from at least partial neutralization of methacrylic acid with an alkaline or basic auxiliary, alkyl alkoxyisobutyrate, and alcohol, wherein step a then further comprises admixing the stream with a strong acid and separating in an extraction into a hydrophobic phase comprising alkyl methacrylate, a greater fraction of methacrylic acid and alkyl alkoxyisobutyrate, and a hydrophilic phase comprising water, the alcohol, and fractions of alkyl methacrylate and methacrylic acid, and wherein step a then further comprises separation of the hydrophobic phase into the first fraction containing the predominant portion of the alkyl methacrylate and the second fraction containing the methacrylic acid and the alkyl alkoxyisobutyrate.

8. The process according to claim 1, wherein step a comprises freeing the reactor output from reactor II of methacrolein and partly of the alcohol in a first distillation column, to obtain a stream comprising: alkyl methacrylate, water, methacrylic acid and/or an alkali metal methacrylate obtained from at least partial neutralization of methacrylic acid with an alkaline or basic auxiliary, alkyl alkoxyisobutyrate, and alcohol, wherein the stream is then separated in a second distillation into a light phase comprising alkyl methacrylate and the alcohol as the first phase, and a heavy phase comprising water, alkyl alkoxyisobutyrate and methacrylic acid and/or the alkali metal methacrylate, as the second phase.

9. The process according to claim 1, wherein the alcohol is methanol, the alkyl methacrylate is methyl methacrylate and the alkyl alkoxyisobutyrate is methyl methoxyisobutyrate (MMIB).

10. The process according to claim 1, wherein the reaction in reactor III is effected at a temperature between 80 and 170° C.

11. The process according to claim 6, wherein the catalyst in reactor III is sulfuric acid.

12. The process according to claim 1, wherein the first reaction stage in reactor I is a reaction of propanal with formalin.

13. The process according to claim 1, wherein the first reaction stage in reactor I is a reaction of isobutene and/or tert-butanol with atmospheric oxygen in the presence of a heterogeneous catalyst at temperatures of 300 to 500° C. to form methacrolein, wherein the methacrolein is condensed and worked up to a purity of at least 80% and isolated in liquid form, and wherein the methacrolein is then sent to the further reaction in reactor II of oxidative esterification.

14. The process according to claim 4, wherein step a comprises freeing the reactor output from reactor II of methacrolein and partly of the alcohol in a first distillation column, to obtain a stream comprising: alkyl methacrylate, water, methacrylic acid and/or an alkali metal methacrylate obtained from at least partial neutralization of methacrylic acid with an alkaline or basic auxiliary, alkyl alkoxyisobutyrate, and alcohol, wherein the stream is then separated in a second distillation into a light phase comprising alkyl methacrylate and the alcohol as the first phase, and a heavy phase comprising water, alkyl alkoxyisobutyrate, methacrylic acid and/or the alkali metal methacrylate, dimeric methacrolein and an alkyl ester derivative of dimeric methacrolein, as the second phase.

15. The process according to claim 14, wherein dimeric methacrolein is cleaved in reactor III into methacrolein, and the alkyl ester derivative of dimeric methacrolein is cleaved into methacrolein and the alkyl methacrylate.

16. The process according to claim 15, wherein the methacrolein from reactor III is separated from the alkyl methacrylate in a later distillation stage and returned to reactor II.

17. The process according to claim 16, wherein the heavy phase further comprises terephthalic acid obtained as a by-product, and wherein the terephthalic acid is removed from a reactor output from reactor III as a high-boiling component by distillation or as a hydrophilic component by extraction.

18. The process according to claim 6, wherein the catalyst is a Brønsted acid and wherein, after the second fraction is reacted in reactor III, the catalyst is recycled into reactor III or another workup step.

19. The process according to claim 4, wherein the derivative of dimeric methacrolein is a dimeric methacrolein ester.

20. The process according to claim 6, wherein the second fraction is reacted in reactor III in the presence of a Brønsted acid.

Description

LIST OF REFERENCES FOR THE FIGURE

(1) The FIGURE is an example of a possible flow diagram of the MMA process according to the invention including a reactor for obtaining MMA from MMIB and MA. (1) Reactor I for MAL synthesis (2) Distillation column (3) Reactor II for DOE reaction (4) MAL removal (5) Intermediate column and/or extraction (6) Column for methanol removal (7) Column for MMA purification—high boilers (8) 2nd column for MMA purification—low boilers (9) 3rd column for MMA purification—purifying column (10) Purified MMA (11) Optional column for reduction in the amount of MMA from bottom stream from (7) (12) Addition of acid and MeOH for (13) (13) Reactor III for cleavage of MMIB to MMA and DIMAL ester to MAL and MMA and esterification of MAA to MMA (14) Optional column for separation of the values from high boilers & sulfuric acid (15) Wastewater (16) Recycling for methacrolein and methanol

EXPERIMENTAL

Example 1: Performance of the Reaction at Standard Pressure as a Fed Batch with Fresh Reactants, MAA and MMIB

(2) The reaction is conducted in a glass three-neck flask with attached column.

(3) The three-neck flask is equipped with a precision glass stirrer and with a 1 n-high column having a clear diameter of 40 mm; the heating is by means of an oil bath. The column is filled with Raschig rings; a reflux divider is placed at the top of the column section in order to be able to control reflux and removal. A 1 l 3-neck flask is initially charged with 2 mol of MMIB and 2 mol of methacrylic acid, and 0.2 mol of water.

(4) Added to this mixture in each case are 200 ppm of phenothiazine and 50 ppm of Tempol as stabilizers and for inhibition of any free-radical polymerization of (meth)acrylic reactants and products under the reaction conditions. The reaction mixture is heated to 150° C. by means of an oil bath; after 10 min, this temperature has been attained with the preheated oil bath; the column is switched to full reflux, such that no distillate is obtained at first. On attainment of the internal temperature of 150° C., a mixture of MMIB, MAA and MeOH, water and sulfuric acid is continuously fed into the reaction mixture via the immersed capillary at a metering rate of 150 g/h. The feed mixture is metered in by means of an HPLC pump; a second HPLC pump removes the reaction bottoms that arise through a capillary once the reaction has run to a steady state.

(5) Reactants and catalyst, alcohol and water are premixed separately and introduced into the reaction via a capillary which is guided to beneath the stirrer. Composition of the reed mixture:

(6) TABLE-US-00001 TABLE 1 Feed mixture for cleavage of MMIB to MAA with parallel esterification of MAA to MMA Mol % M Feed Feed [basis = Chemical % by wt. [g/mol] [g/h] [mol/h] MMIB] MMIB 44 118 66 0.56 100 MAA 32 86 48 0.56 100 Water 3.3 18 4.95 0.28 49 Sulfuric acid 3.7 98 5.55 0.06 10 Methanol 17 32 25.5 0.80 142

(7) Thus, the molar ratio of the C.sub.4 by-products MAA and MMIB is 1:1. The water content is 49 mol % based on MMIB and 142 mol % of MeOH based on MMIB.

(8) The oil bath is heated up to 160° C. with commencement of addition of the feed; the internal temperature in the reactor rises gradually up to about 150° C. and a mixture consisting of the azeotropic compositions of the binary MeOH and MMA/MMA and water azeotropes collects at the top of the column. As soon as the top of the column has reached a stable temperature of 69° C., a reflux ratio of 0.8 is established and distillate is removed.

(9) The reaction is operated continuously at first for 6 h, with quantification and analysis of the amount of distillate every hour. The plant is operated such that an average of about 90% of the mass of reactants supplied per hour is drawn off as distillate at the top of the column, while the reaction bottoms are likewise discharged continuously; an average of about 10% of the feed stream supplied is removed by means of an HPLC pump. On average, the fill level in the flask is thus maintained and the reaction can be considered as being steady-state in terms of volume or mass at this stage. Connected downstream of the condenser, which is operated with tap water having a cooling water temperature of about 18° C., at the top of the column is a cold trap in order to capture volatile components; the cold trap is operated with a mixture of acetone/dry ice at nearly minus 60° C.; the cold trap is filled with THF in order to absorb and qualitatively elucidate and determine volatile components.

(10) The liquid phase at first turns yellow, then light orange within 6 h; barely any rise in viscosity is perceptible.

(11) The top product from the column obtained as distillate in the steady state weighs 134.9 g/h and, by GC chromatography, has the following composition:

(12) TABLE-US-00002 TABLE 2 Distillate product of the reaction M Distillate Distillate Chemical % by wt. [g/mol] [g/h] [mol/h] MMA 79.1 100 106.7 1.06 Water 3.3 18 4.7 0.26 Methanol 17.6 32 23.7 0.74 Total distillate 100 # 134.9 2.06

(13) The bottom product obtained from the discharge in the steady state weighs 15.1 g/h and has the following composition:

(14) TABLE-US-00003 TABLE 3 Bottom product from the reaction M Bottoms Bottoms Chemical % by wt. [g/mol] [g/h] [mmol/h] MMIB 17.5 118 2.64 22.4 MAA 21.9 86 3.30 38.4 Methanol 0.1 32 0.01 0.3 Sulfuric acid 36.8 98 5.55 56.6 Water 1.7 18 0.25 13.9 High boilers 22.2 # 3.35 # Total bottoms 100 # 15.1 #

(15) In terms of the amounts of reactant supplied, this corresponds to a theoretical yield of MMA based on MMIB of 96%, based on the methacrylic acid esterified to MMA of 95% and a methanol recovery rate of 93%.

(16) In the cold trap, as well as the THF solvent used as absorbent, small amounts of dimethyl ether are detected by means of gas chromatography (boiling point −24° C.).

(17) The experiment shows that, under the conditions chosen, it is possible to use mixtures comprising MAA and MMIB, in the presence of stoichiometric amounts of sulfuric acid and in the presence of MeOH and water, to prepare crude MMA with high efficiency and at high conversion rates (based on the reactants).

Examples 2 to 9

(18) Preparation of methacrolein from propanal and formalin: methacrolein was prepared and isolated according to EP 2 998 284.

(19) A formalin solution having a formalin content of 37% by weight or 55% by weight, depending on the example, and propanal are mixed by means of a static mixer (referred to below as aldehyde solution) and the mixture is subsequently heated to the desired temperature (see Table 1) in an oil-heated heat exchanger. The exact water content of the formalin, depending on the example, plays no further role, since this completely enters the water content of the fresh feed in accordance with Table 1. A recycle stream, which adjoins the tubular reactor from the bottom of the product column, is mixed with acetic acid and dimethylamine (as 40% solution in water) and is likewise pre-heated to the desired temperature. The pre-heated aldehyde solution and the pre-heated catalyst solution are mixed in a further static mixer. This reactant mixture is then fed to an oil-heated tubular reactor. The reaction is typically carried out at pressures of about 35 to 40 bar.

(20) The product mixture at the outflow of the tubular reactor is released via a valve and enters the product column for the distillation. At the top of this column, after condensation and phase separation, a biphasic mixture of methacrolein and an aqueous phase is obtained. The aqueous phase is fed back to the column. The organic phase enters the product container. At the bottom of the column, a partial stream is fed back into the reaction as recycling. Another partial stream is removed as aqueous product into a further product container. In examples 1 to 4, a methacrolein quality having a DIMAL content of less than 0.2% by weight is obtained. The water content is about 56% by weight and the dimethylamine content, based on the water in the feed, is about 2.7% by weight. The temperature in the reactor is between 122° C. as inlet temperature and 153° C. as outlet temperature. No significant temperature spike occurs.

(21) Examples 5 to 7 show that the parameters of the reaction regime have a crucial effect on conversion and DIMAL content, since it was possible here to achieve a content of dimeric MAL below 0.4% by weight, but not below 0.2% by weight. The difference from examples 1 to 4 here is in particular the higher maximum temperature and outlet temperature, as well as a higher inlet temperature in some cases.

(22) Examples 8 and 9 show embodiments that produce a methacrolein quality having a content of dimeric MAL below 0.5% by weight. Here, the inlet temperatures and particularly the maximum temperatures were even higher. More particularly, the maximum temperatures were above the preferred maximum temperatures of 165° C. or even 170° C.

(23) TABLE-US-00004 TABLE 4 Preparation of MAL from propionaldehyde and formalin Table: Preparation of methacrolein from propanal (PA) and formalin (FO) PA:FO DMA:PA ACOH:DMA Recycle DMA:PA H.sub.2O DMA/H2O Fresh feed Reactor inlet mol/mol mol % mol/mol % mol % % % DE3213681A1 Ex. 1 1 3.7 1.08 — — 50 1.8 DE3213681A1 Ex. 2 1 3.6 1.14 — — 40 2.5 Example 1 0.99 2.50 1.09 70.5 7.8 55.6 2.74 Example 2 0.99 2.51 1.09 71.0 7.8 56.1 2.74 Example 3 0.98 2.61 1.09 71.2 8.2 54.9 2.82 Example 4 0.96 2.51 1.09 70.1 7.7 56.5 2.71 Example 5 0.99 2.51 1.09 70.5 7.8 55.7 2.75 Example 6 0.99 2.51 1.09 70.4 7.8 55.6 2.75 Example 7 0.98 2.50 1.09 70.5 7.7 56.0 2.72 Example 8 0.99 2.51 1.09 70.5 7.8 55.6 2.74 Example 9 0.99 2.52 1.08 70.4 7.8 55.6 2.76 PA Selectivity c RT T.sub.OIL T.sub.in T.sub.out conversion MAL DIMAL sec ° C. ° C. T.sub.max ° C. % % % DE3213681A1 Ex. 1 6.9 161 184 — 99.5 98.1 0.49 DE3213681A1 Ex. 2 6 162 205 — >99.4 97.2 <1 Example 1 9.30 139.5 122.5 152.6 152.2 99.37 98.75 0.18 Example 2 9.26 139.1 122.5 152.3 152.0 99.30 98.85 0.18 Example 3 9.41 139.9 122.1 152.3 152.2 99.35 98.67 0.18 Example 4 9.21 139.1 122.8 153.0 153.0 99.46 98.33 0.18 Example 5 9.26 143.9 129.9 160.2 155.5 99.75 98.19 0.34 Example 6 9.30 144.2 127.3 157.7 154.7 99.65 98.47 0.27 Example 7 9.22 139.0 122.5 156.3 154.9 99.57 98.62 0.22 Example 8 9.26 159.8 142.1 173.0 169.1 99.67 98.03 0.49 Example 9 9.26 146.4 133.8 165.4 159.7 99.77 98.34 0.45

(24) The methacrolein prepared as described above is decompressed after the reaction (optionally partly evaporated in a flash box), and guided into a distillation column. At the top of the distillation column, after condensation, a biphasic mixture is obtained (depending on the temperature, a greater or lesser water phase separates out), where the upper phase contains methacrolein quality of >97%, with a water content of 1-3 wt %. The formalin content in the methacrolein is <2000 ppm; the methanol content, depending on the methanol content of the formalin used, is between 0.1 and 1.0 wt %. According to the above examples, the methacrolein contains a DIMAL content of 0.18 wt % to <1 wt %. This quality is used in the experiments which follow for direct oxidative esterification with methanol.

Example 10: Performance of Direct Oxidative Esterification in the Liquid Phase

(25) A 20 l reactor with a sparging stirrer is charged with a reaction mixture composed of 38 percent by weight of methacrolein in methanol with a slurry density of 8 percent by weight of catalyst. The reaction mixture is brought to 5 bar while stirring at 80° C., and air is metered in such that the oxygen concentration in the tail gas downstream of the condensers is 4.0 percent by volume. The pH is adjusted to 7 by continuously introducing 4 percent by weight NaOH in methanol solution. The reaction mixture is removed continuously from the reactor in such a way that the catalyst hourly space velocity is 11 mol MAL/kg catalyst/hour. The run time is in each case 1000 hours. a) The catalyst used is a gold-cobalt oxide catalyst (WO2017084969 A1) and a conversion of 78% MAL is obtained at a selectivity of 94.1% MMA. The selectivity for MAA is 3.1% and the selectivity for MMIB 1.2%. b) The catalyst used is a gold-nickel oxide catalyst (U.S. Pat. No. 8,450,235) and a conversion of 75% MAL is obtained at a selectivity of 94.4% MMA. The selectivity for MAA is 2.5% and the selectivity for MMIB 1.2%. c) The catalyst used is a palladium-lead catalyst (U.S. Pat. No. 5,969,178), where the pH of the reaction is adjusted to 6.3, and a conversion of 60% MAL is obtained at a selectivity of 89% MMA. The selectivity for MAA is 7% and the selectivity for MMIB is below 0.1%. d) The catalyst used is a palladium-bismuth-tellurium catalyst (US20160188072) and the conditions and stoichiometries are set according to examples 2 and 3 as described in US20160188072. A conversion of 89% is obtained at a selectivity of 92% MMA. The selectivity for MAA is below 0.2% and the selectivity for MMIB is 1.2%.

Example 11: Cleavage of MMIB to MMA and Methanol with Simultaneous Esterification of MAA to MMA with Reaction Mixtures from Example 3 after Inventive Removal of Methacrolein and Methyl Methacrylate. Sulfuric Acid as Catalyst

(26) The reaction mixture obtained from Example 3a was taken after the workup:

(27) The workup is described by way of example, and the respective compositions are listed in Table 1.

(28) The output from reactor II (1000 g/hr) was guided to the MAL recovery column at plate 11 of 22. The temperature in the bottoms was 70° C. at a pressure of 930 mbar. The bottom stream was acidified to pH 2 with sulfuric acid and separated in a decanter, and the organic phase was run into the bottom of the extraction column, while the aqueous phase was introduced Into the top of the 30-plate extraction column. The bottom temperature of the extraction column was 43.9° C. at a pressure of 1013 mbar. The top stream from the extraction column was introduced to plate 6 of 10 in the high boiler column. The bottom temperature was 85.4° C. at a pressure of 235 mbar.

(29) TABLE-US-00005 TABLE 5 Composition of the reaction mixture in the different workup steps Liquid Reactor Bottoms of Tops from phase of Component output MAL recovery extraction high boilers Methanol 47.3% 28.9% 1.8% 22 ppm Water 5.6% 10.9% 6.0%  0.3% MAL 10.3% 64 ppm 1300 ppm 12 ppm MMA 32.6% 55.1% 83.4%  11.4% MMIB 0.4% 1.2% 1.4% 32.2% MAA 0.9% 0.6% 2.8% 24.6% DIMAL ester 0.1 0.3% 0.7% 12.8% Secondary 2.8% 2.1% 3.8% 19.0% components

(30) The liquid phase from the high boiler column was collected and used for the cleavage of MMIB to MMA and MeOH, and of DIMAL ester to MAL and MMA, with simultaneous esterification of MAA with MeOH to give MMA.

(31) A 500 ml three-neck flask was provided with a column and a glass thermometer. At the top of the column, 50 g of MeOH with phenothiazine (about 500 ppm) were placed in a dropping funnel in order to prevent polymerization in the column by continuous addition. The thermocouple was placed into the oil bath (T(oil)=165° C.).

(32) 300 g of feed (1 eq., 0.73 mol 3-MMib; 1.17 eq., 0.85 mol MAA; 0.34 mol MMA, 0.23 mol DIMAL ester),

(33) 2.84 g (0.04 eq., 0.029 mol) of H.sub.2SO.sub.4 and

(34) 13.42 g of H2O (1.02 eq., 0.75 mol)

(35) were initially charged in the three-neck flask which was guided into the oil bath (target temperature=165° C.).

(36) The mixture was heated to 165° C. (oil bath target temperature) for 3 h, reaching a bottom temperature of 151° C. The distillate was removed continuously and analysed by HPLC. Over the course of the reaction of 3 hours, the methanol/stabilizer solution (6.54 g/h, 0.20 mol was added.

(37) Table No. 2 below shows the amounts of sulfuric acid, water, methanol and feed sample used. Also listed is the composition of the feed sample for 3-MMib, MAA and MMA together with the molar masses.

(38) TABLE-US-00006 TABLE 6 Amount of the substances used and their molar masses Feed H.sub.2SO.sub.4 H.sub.2O MeOH Stab. [% by wt.] [% by wt.] [% by wt.] [% by wt.] [% by wt.] Total [g] Mol. mass 3-MMib 32.31 132.16 MAA 24.61 86.09 MMA 11.41 100.12 DIMAL 12.8 170.21 ester H2SO4 98.00 98.08 H2O 2.00 100.00 18.02 MeOH 100.00 32.04 S47 S71 Masses [g] 300.51 2.84 13.42 19.63 0.26 362.57

(39) Table No. 7 shows the recovery of the masses of the above-listed reactants used.

(40) TABLE-US-00007 TABLE 7 Conclusion of mass balance Amount Distillate Bottoms Dist. + bottoms Difference Mass used [g] [g] [g] [g] [g] balance 362.57 232.81 125.78 358.59 3.98 98.90%

(41) The mass balance is at a recovery rate of 98.90%. Table No. 8 shows the molar distribution of the components in distillate and bottoms.

(42) TABLE-US-00008 TABLE 8 Distribution of the components in distillate and bottoms Initial charge Dist. Bottoms Comp. [mol] [mol] [mol] Delta mol Conversion/sel. 3-MMIB 0.735 0.000 0.029 0.705 96.00% Conversion of 3-MMIB MAA 0.859 0.001 0.108 0.750 87.30% Conversion of MAA MMA 0.342 1.620 0.166 1.443 99.16% Selectivity/(MAA + 3-MMIB) MAL 0 0.019 0 0.019 8.26% Conversion of DIMAL ester to MAL and MMA MeOH(*) 0.613 0.23 — — H2O 0.753 — —

(43) The experiment was successful; there was high conversion or 3-MMIB and MAA to MMA.

(44) A conversion of 96.0% 3-MMIB to MMA and 87.3% conversion of MAA to MMA was found. Selectivity for MMA added up to 99.18% for MAA and 3-MMIB. The conversion in the thermal cleavage of DIMAL ester to MAL and MMA was 8.26%.

Example 12: Cleavage of MMIB to MMA and Methanol with Simultaneous Esterification of MAA to MMA with Reaction Mixtures from Example 3 after Inventive Removal of Methacrolein and Methyl Methacrylate. Phosphoric Acid as Catalyst

(45) The reaction was conducted analogously to Example 11 and phosphoric acid was used in place of sulfuric acid.

(46) The experiment was successful; there was high conversion of 3-MMIB and MAA to MMA.

(47) A conversion of 94.2% 3-MMIB to MMA and 86.8% conversion of MAA to MMA was found. Selectivity for MMA added up to 99.0% for MAA and 3-MMIB. The conversion in the thermal cleavage of DIMAL ester to MAL and MMA was 8.25%.

Example 13: Cleavage of MMIB to MMA and Methanol with Simultaneous Esterification of MAA to MMA with Reaction Mixtures from Example 3 after Inventive Removal of Methacrolein and Methyl Methacrylate. Methanesulfonic Acid as Catalyst

(48) The reaction was conducted analogously to Example 11 and methanesulfonic acid was used in place of sulfuric acid.

(49) The experiment was successful; there was high conversion of 3-MMIB and MAA to MMA.

(50) A conversion of 92.6% 3-MMIB to MMA and 84.7% conversion of MAA to MMA was found. Selectivity for MMA added up to 98.8% for MAA and 3-MMIB. The conversion in the thermal cleavage of DIMAL ester to MAL and MMA was 8.20%.

Example 14: Cleavage of MMIB to MMA and Methanol with Simultaneous Esterification of MAA to MMA with Reaction Mixtures from Example 3 after Inventive Removal of Methacrolein and Methyl Methacrylate. Temperature of 120° C.

(51) The reaction was conducted analogously to Example 11 at a temperature of 120° C.

(52) There was high conversion of 3-MMIB and MAA to MMA.

(53) A conversion of 60.4% 3-MMIB to MMA and 87.3% conversion of MAA to MMA was found. The conversion in the thermal cleavage of DIMAL ester to MAL and MMA was 8.20%.

Example 15: Cleavage of MMIB to MMA and Methanol with Simultaneous Esterification of MAA to MMA with Reaction Mixtures from Example 3 after Inventive Removal of Methacrolein and Methyl Methacrylate. Temperature of 90° C.

(54) The reaction was conducted analogously to Example 11 at a temperature of 90° C.

(55) Conversion of 3-MMIB to MMA was not high, but that of MAA to MMA was.

(56) A conversion of less than 1% 3-MMIB to MMA and 88.0% conversion of MAA to MMA was found.

(57) The thermal cleavage of DIMAL ester to MAL and MMA did not proceed.

Example 16: Cleavage of MMIB to MMA and Methanol with Simultaneous Esterification of MAA to MMA with Reaction Mixtures from Example 3 after Inventive Removal of Methacrolein and Methyl Methacrylate. Increased Amount of Sulfuric Acid

(58) The reaction was conducted analogously to Example 11 with an increased amount of sulfuric acid of 40 mol %.

(59) The experiment was successful; there was high conversion of 3-MMIB and MAA to MMA.

(60) A conversion of 95.9% 3-MMIB to MMA and 87.4% conversion of MAA to MMA was found. Selectivity for MMA added up to 99.14% for MAA and 3-MMIB. The conversion in the thermal cleavage of DIMAL ester to MAL and MMA was 8.16%.

Comparative Example 1: Cleavage of MMIB to MMA and Methanol with Simultaneous Esterification of MAA to MMA with Reaction Mixtures from Example 3 after Inventive Removal of Methacrolein and Methyl Methacrylate. Temperature of 23° C.

(61) The reaction was conducted analogously to Example 11 at a temperature of 23° C.

(62) Conversions of 3-MMIB to MMA and of MAA to MMA were not high.

(63) A conversion of less than 1% 3-MMIB to MMA and 20% conversion of MAA to MMA was found. The thermal cleavage of DIMAL ester to MAL and MMA did not proceed.

Comparative Example 2: Cleavage of MMIB to MMA and Methanol with Simultaneous Esterification of MAA to MMA with Reaction Mixtures from Example 3 after Inventive Removal of Methacrolein and Methyl Methacrylate. No Addition of Sulfuric Acid as Catalyst

(64) The reaction was conducted analogously to Example 11 without addition of sulfuric acid as catalyst.

(65) Conversion of 3-MMIB to MMA was high, but there was no conversion of MAA to MMA.

(66) A conversion of 94% 3-MMIB to MMA and no conversion of MAA to MMA was found. The thermal cleavage of DIMAL ester to MAL and MMA was 8.0%.

Example 17: Continuous Cleavage of MMIB to MMA and Methanol with Simultaneous Esterification of MAA to MMA with Reaction Mixtures from Example 3 after Inventive Removal of Methacrolein and Methyl Methacrylate

(67) The reaction was conducted analogously to Example 11. In addition, on attainment of the bottom temperature of 151° C., a continuous feed of feed mixture of 57 g/hr was commenced. The experiment ran for 8 hours.

(68) The experiment was successful; there was high conversion of 3-MMIB and MAA to MMA.

(69) A conversion of 95.5% 3-MMIB to MMA and 87.5% conversion of MAA to MMA was found. Selectivity for MMA added up to 98.7% for MAA and 3-MMIB. The conversion in the thermal cleavage of DIMAL ester to MAL and MMA was 8.05%.