DE2615887B2 - Process for the production of methacrylic acid and methacrylic acid methyl ester and catalyst for carrying out the process - Google Patents

Description

/ CH ₂

P-CH ₃

(III)

O-CHj

10

15th

wherein R ^{1 has} the aforementioned meaning with formaldehyde dimethyl acetal of the formula

20th

25th

in the presence of catalysts optionally containing aluminum oxide for a reaction time of 0.1 to 100 seconds, characterized in that the catalysts used are phosphates and / or silicates of magnesium, calcium, aluminum, zirconium, thorium and / or y, titanium alone or together with oxides of magnesium, calcium, zirconium, aluminum, thorium and / or titanium and / or boric acid and / or urea in the presence of 0 to 0.5 mol of water per mol of starting material 111 used

2. Catalyst for carrying out the process according to claim 1 made from phosphates and / or silicates of magnesium, calcium, aluminum, zirconium, thorium and / or titanium alone or together with oxides of magnesium, calcium, zirconium, aluminum, thorium and / or Titanium and / or boric acid and / or urea.

The invention relates to a new process for the preparation of methacrylic acid and methacrylic acid methyl ester by reacting propionic acid and Methyl propionate with formaldehyde dimethyl acetal in the presence of aluminum, magnesium, calcium, Zirconium, thorium, titanium catalysts and optionally boric acid and / or urea, during a short dwell time.

In US-PS 30 14 958 the implementation of Formaldehyde in aqueous solution with propionic acid methyl ester in a molar ratio of 1: 1.5 to 1:20 over dehydration catalysts at 225 to 450 ° C. in the presence of at least 7 percent by weight of methyl methacrylate described. The best yield of methyl methacrylate, based on the formaldehyde used, with a molar ratio of methyl propionate / formaldehyde / water / methacrylic acid-me-

ethyl ester 10: 1: 1: 0.8 84% if a mixture of K2O MgO and Fe ₂ Oa is used as the catalyst. If calcium phosphate is used, a yield of only 43% or less is obtained, and in the case of aluminum phosphate 46%.

DE-OS 2339 243 describes the preparation of methyl methacrylate from alkyl propionate, formaldehyde, water and optionally methanol in the presence of compounds of main group 1 of the Periodic Table on a support as catalysts with a specific surface area of 350 to 1000 m ² -g- ', at temperatures between 400 and 600 ° C., a molar ratio of water: formaldehyde in the range from 0.01: 1 to 10: 1 being necessary. Inert gas is fed in in the examples to dilute the reaction mixture. In example 1, which has a good space-time yield compared to the other examples, is achieved when using

Propionic acid methyl ester / formaldehyde / water / methanol of 4.5: 1: 53: 6.7 and 67% formaldehyde conversion yields of methacrylic acid methyl ester up to 92%. Silica gels and silica earths of the aforementioned structure are preferred as carriers Examples are only described potassium hydroxide and rubidium carbonate on silica gel as a catalyst. Water is essential as a starting material; without water, there is practically no condensation to give methyl methacrylate (Example 4). Only with catalysts a specially produced, large surface area, very good yields are possible (Example 11).

DE-OS 23 49 054 describes the reaction of formaldehyde with an alkanoic acid or its ester in Presence of basic, fumed silica comprising catalysts known. Catalysts containing alkali hydroxide are preferred. A molar ratio of Alkanoic acid to formaldehyde to water to methanol in the range from 1: 1: 0.01: 0 to 1: 1: 6: 0.03 described. With a molar ratio of propionic acid / formaldehyde / water / methanol of 20: 20: 59: 1 and a maximum of 34% conversion of formaldehyde and propionic acid into methacrylic acid and methacrylic acid methyl ester, yields of 58 to 69% are achieved, based on converted formaldehyde, or 58 to 80%, based on converted propionic acid Reaction of methyl propionate with formaldehyde, water and methanol in the same molar ratio yields of 63% and 44% are achieved at 25% conversion; Potassium hydroxide is used on pyrogenic Silica as a catalyst.

Finally, it is known from GB-PS 7 85 100 lower alkyl esters of saturated monocarboxylic acids in To implement the presence of catalysts for condensation reactions with formaldehyde. The formaldehyde can be anhydrous or as a solution of p-formaldehyde in methanol or another lower one aliphatic alcohol can be used, which contains 5 to 10% water. The source of formaldehyde includes: Methylal in question. As catalysts that are on supports, such as activated alumina or activated Silica gel which can be used are, for example, manganese oxides, sodium phosphate, sodium pyrophosphate, zinc oxide, byoxide, sodium hydroxide, manganese acetate and lead acetate and are mentioned in the examples Manganese oxide and lead oxide used on activated silica gel. At no point will this GB-PS, however the reaction of methylal with methyl propionate is mentioned and neither one for this special reaction special catalyst specified another statement

made whether water should be absent during the process Attempting to react methyl propionate with dimethyl formal in the presence of sodium phosphate at 350 to 380 ° C, however, only 5 to 7% des Methylais reacted, with no methacrylic acid methyl ester in the reaction mixture by gas chromatography could be proven.

It has now been found, surprisingly, that you can methacrylic acid and methyl methacrylate formula

Formaldehyde dimethyl acetal of the formula

CH ₂

O — CH,

(Π1)

Ο — CH ₃

K)

CH ₁

CH ₂ = CC-OR ¹ O

(D

wherein R ¹ denotes a hydrogen atom or a methyl group, by reacting propionic acid or propionic acid methyl ester of the formula

CH ₃ -CH ₂ -C-OR ¹ (II)

wherein R ^{1 has} the aforementioned meaning, with in the presence of optionally aluminum oxide containing catalysts during a reaction time of 0.1 to 100 seconds is advantageous if as catalysts phosphates and / or silicates des Magnesium, calcium, aluminum, zirconium, thorium and / or titanium alone or together with oxides of magnesium, calcium, zirconium, aluminum, thorium and / or titanium and / or boric acid and / or urea in the presence of 0 to 0.5 moles of water per mole

Starting material III used

If formaldehyde dimethyl acetal and methyl propionate are used, the reaction is represented by the following equation:

CH ₁ -CH ₂ -C-OCH, + CH ₁ -O-CH ₂ -O-CH, O

CH ₃

CH ₂ = CC-OCH ₃ + 2CH ₃ OH. O

Compared to the known method, the method according to the invention provides on a simpler and more economical route methacrylic acid and methyl methacrylate in good yield and purity. Despite masking the formaldehyde in the form of dimethyl acetal, which has not previously been used as a starting material Surprisingly, there is a reaction with propionic acid or propionic acid methyl ester to give the end product I. It was also not possible with regard to the prior art the technology is suspected that the implementation with very small amounts of water and even higher Yields in the absence of water, as is the general embodiment of the invention Procedure is feasible. The ability of the starting materials according to the invention to condense with a good space-time yield is particularly surprising and selectivity also in a temperature range that is below the optimum temperatures for condensation with formaldehyde by known methods. Since water is generally neither supplied nor with the reaction according to the invention arises, one avoids hydrolysis of the esters and therefore does not require any Methanol as a starting material, energy and material are saved. Further advantages are in the easier and energy-saving work-up, easier recirculation of any unreacted formaldehyde in the form of dimethylacetals and thus in easier wastewater treatment. The method according to the invention is more environmentally friendly. Another advantage is the saving of additional diluents, e.g. B. solvent or inert gas, the use of which makes condensation and distillation of the reaction mixtures difficult; the separation of the Diluent leads to losses of the end product. For correspondingly equal conversion and yield, based on formaldehyde dimethyl acetal, surprisingly, the use of special, expensive preparable catalysts with a large specific surface area or the use of methyl methacrylate in the starting mixture can be dispensed with.

v, One gets in this way already with conventionally manufactured

Catalysts, their manufacture, durability

and regeneration comparatively fewer problems raise already high sales and selectivities.

The starting materials 11 and III are in stoichiometric

shear amount or each in excess based on the others, expediently in a ratio of 0.01 to 20, preferably from 1 to 10, in particular from 2 to 6 mol

Starting material II per mole of starting material III, implemented. The implementation is generally at a

4 ¹ J temperature from 200 to 500 ⁰ C, preferably from 250 to 450 ⁰ C, in particular from 270 to 400 ° C, without pressure or under pressure, continuously or discontinuously, in a fixed bed or a catalyst fluidized bed carried out. The reaction is preferably carried out without

^r ) 0 addition of solvents and in particular without the addition of water. Optionally, between 0 and 0.5, e.g. B. from 0.01 to 0.1 mol of water per mole of starting material Hl, use. As reaction times or residence times of the starting mixture in the reaction

• π space 0.1 to 100, preferably 0.2 to 50, in particular 0.5 to 40 seconds are possible.

The catalysts used are made of phosphates and / or silicates of magnesium, calcium, aluminum, zirconium, thorium and / or titanium alone or

bo together with oxides of magnesium, calcium, Zircon, aluminum, thorium and / or titanium and / or boric acid and / or urea. Among the metals, aluminum, titanium, and zirconium are more advantageous than magnesium, calcium, and thorium; among the compounds, phosphates are more advantageous than silicates. A combination of the metal compounds with boric acid and / or urea is particularly advantageous.

The preferred catalysts, in order of decreasing preference, are:

Aluminum phosphate, titanium dioxide, boric acid, Urea; Aluminum phosphate, zirconium dioxide, Boric acid, urea; Aluminum phosphate; Aluminum phosphate, titanium dioxide; Aluminum phosphate zirconia, boric acid; Aluminum phosphate thorium dioxide, boric acid, urea; Aluminum phosphate aluminum oxide, boric acid, urea; Aluminum phosphate titanium dioxide, urea; Aluminum phosphate thorium dioxide, boric acid; Aluminum phosphate, aluminum oxide, boric acid; Aluminum phosphate aluminum oxide, urea; Aluminum phosphate, urea, boric acid; Aluminum phosphate boric acid; Aluminum phosphate urea; Aluminum phosphate aluminum oxide; Aluminum phosphate magnesium sulfate; Aluminum phosphate aluminum silicate boric acid, 2u urea; Aluminum phosphate aluminum silicate, boric acid; Aluminum phosphate, aluminum silicate, urea; Aluminum phosphate, aluminum silicate; Aluminum phosphate magnesium phosphate; Titanium dioxide, calcium phosphate, boric acid, urea; Titanium dioxide, calcium phosphate, boric acid; Titanium dioxide, calcium phosphate urea; Titanium dioxide, magnesium silicate, boric acid, urea; Titanium dioxide, magnesium silicate, boric acid; Titanium dioxide, magnesium silicate, _{J ()}

Urea; Titanium dioxide, thorium phosphate, boric acid, urea; Titanium dioxide, Thorium phosphate boric acid; Titanium dioxide, thorium phosphate urea; Titanium dioxide, thorium phosphate; Zirconium phosphate, boric acid, r,

Urea; Zirconia, calcium phosphate, boric acid, urea; Aluminum phosphate, Calcium phosphate boric acid, urea; Aluminum phosphate, calcium phosphate, boric acid; Aluminum phosphate calcium phosphate; Calcium phosphate boric acid, urea; Calcium phosphate boric acid; Calcium phosphate, Urea; Calcium phosphate, aluminum phosphate; Calcium phosphate titanium dioxide, zirconium dioxide, Boric acid, urea; Calcium phosphate; Magnesium silicate, boric acid, urea; Magnesium silicate boric acid; Magnesium silicate urea; Magnesium silicate; Aluminum silicate, Boric acid, urea; Aluminum silicate, titanium dioxide, boric acid, urea; Aluminum silicate, titanium dioxide, Boric acid; Aluminum silicate.

Each catalyst or each catalyst combination in the above-mentioned sequence forms, at the same time, with all of the preceding catalysts in the sequence, a particularly preferred selection group compared to the other, subsequent catalysts in the sequence. Thus, aluminum phosphate, and boric acid / urea / titanium dioxide is a preferred group selected against thorium phosphate boron _b0 acid / urea / titanium dioxide and all other catalysts; Thorium phosphate, boric acid / urea / titanium dioxide is in turn a selected, preferred group over magnesium silicate and all other catalysts in the series. _fe5

The catalyst or the catalyst mixture is expediently used in an amount from 20 to 200, preferably from 40 to 160, in particular from 60 to 150 Percentage by weight based on the total amount of starting materials II and IH used. In continuous operation, it is expedient to use from 2 to 2500, preferably from 5 to 1500, in particular from 5 to 500 kilograms of total amount of starting materials II and III per kilogram of catalyst per hour. In the case of mixtures, a proportion is from 5 to 50, preferably from 8 to 40 percent by weight boric acid or from 1 to 20, preferably from 2 to 15 percent by weight of urea, based on the metal compound, or from 6 to 70, preferably from 10 to 55 percent by weight of boric acid and urea together, based on metal compound or from 250 to 500, preferably from 270 to 400 percent by weight of boric acid, based on urea, advantageous.The oxides, phosphates and silicates can be present in the catalysts as components of a mixture or a crystal lattice or in the form of mixed crystals. Are higher temperatures such. B. used above 400 ^° C., depending on the temperature, a smaller or larger part of the urea can pass into secondary products without any significant disadvantage for the activity of the catalyst.

The reaction can be carried out as follows: A mixture of starting material II and starting material III in the gas / vapor phase is over the catalyst during the aforementioned reaction time at the Reaction temperature then passed the end product from the reaction mixture in a conventional manner, for. B. by Cooling and fractional distillation, separated.

The methacrylic acid and methyl methacrylate obtainable by the process of the invention are valuable raw materials for the production of plastics, finishes, adhesives, lubricating oil additives and pesticides. Regarding the Use is made on the aforementioned publications and Ullmann's Encyclopedia of Industrial Chemistry, Volume 12, pages 392 to 396, referenced.

The parts listed in the following examples are parts by weight.

example 1

130 parts of aluminum phosphate (4 mm strands), corresponding to the composition 42 percent by weight Al2O3 and 58 percent by weight P2O5, are filled into a tubular reactor equipped with an evaporator. The reactor is heated to 300 ° C. and a mixture of 3.8 parts of formaldehyde dimethyl acetal and 44 parts of methyl propionate is passed through for 60 minutes. The residence time is 27.8 seconds. The reaction mixture is analyzed by gas chromatography and fractionally distilled. The conversion to methyl methacrylate, based on formaldehyde dimethyl acetal, is 83%, the yield (analysis) 4.2 parts (84% of theory) with a boiling point of 100 ^° C.

Example 2

The reaction is carried out as in Example 1. The reactor is charged with 88 parts of methyl propionate and 7.6 parts of formaldehyde dimethyl acetal ^{at 350 ° C. for 30 minutes.} The residence time is 6.4 seconds. The reaction mixture is analyzed by gas chromatography and fractionally distilled. The conversion to methyl methacrylate, based on formaldehyde dimethyl acetal, is 79%, the yield (analysis) 7.9 parts (81% of theory) of Kd 10O ⁰ C.

Example 3

a) Preparation of the catalyst: 300 parts of titanium dioxide (anatase), 230 parts of calcium phosphate and 75 parts of boric acid are mixed in a kneader. A solution of 25 parts of urea in 50 parts of water is then added and a paste is produced. The paste is heated for 12 hours at 120 ⁰ C dried and then at 580 ° C for 3 hours. The mixture is then ground and sieved.

b) 125 parts of catalyst (grain size 0.5 to 1 mm extrudates) are filled into the reactor, heated to 400 ^° C. and charged with 88 parts of methyl propionate and 15.2 parts of formaldehyde dimethyl acetal for 30 minutes. The residence time is 5.9 seconds. The reaction mixture is analyzed by gas chromatography and fractionally distilled. The conversion to methyl methacrylate, based on formaldehyde dimethyl acetal, is 38%, the yield (analysis) 6.1 parts (46% of theory) with a boiling point of 100 ^° C.

Example 4

a) Preparation of the catalyst: 300 parts of titanium dioxide (anatase), 230 parts of aluminum phosphate and 75 parts of boric acid are mixed in a kneader. A solution of 25 parts of urea in 50 parts of water is added and a paste is produced. The paste is dried and then heated for 3 hours at 600 ⁰ C for 12 hours at 120 ° C. The catalyst mass is then ground and sieved.

b) 130 parts of catalyst (particle size 0.5 to 1 mm) are charged into the reactor and heated to 350 ⁰ C. 88 parts of methyl propionate and 7.6 parts of formaldehyde dimethyl acetal are passed over the catalyst over a period of 30 minutes. The residence time is 6.4 seconds. The reaction mixture is analyzed by gas chromatography and fractionally distilled. The conversion to methyl methacrylate, based on formaldehyde dimethyl acetal, is 92%, the yield (analysis) 9.2 parts (95% of theory) with a boiling point of 100 ° C.

Examples 8-10

Example 5

Analogously to Example 4a illustrates a catalyst is of 300 parts of zirconium dioxide, 230 parts Aluminiumphos- phosphate ¹ S, 75 parts of boric acid and 25 parts of urea forth. 120 parts of this catalyst (grain size 0.5 to 1 mm) are filled into the reactor, heated to 300 ^° C. and charged with 88 parts of methyl propionate and 7.6 parts of formaldehyde for 30 minutes.

Ki dimethyl acetal. The residence time is 7 seconds. The reaction mixture is analyzed by gas chromatography and fractionally distilled. The transformation to methyl methacrylate, based on formaldehyde dimethyl acetal, is 88%, the yield

! -, (analysis) 8.8 parts (89% of theory) with a boiling point of 100 ° C.

Example 6

Analogously to Example 3a, a catalyst is prepared from 300 parts of thorium dioxide, 230 parts of aluminum phosphate, 100 parts of boric acid and 35 parts of urea. 140 parts of this catalyst are filled into the reactor, heated to 330 ^° C. and charged with 176 parts of methyl propionate and 30.4 parts of formaldehyde dimethyl acetal for 60 minutes. The dwell time

2j is 5.6 seconds. The reaction mixture is analyzed by gas chromatography and fractionated distilled. The conversion to methyl methacrylate, based on formaldehyde dimethyl acetal, is 80%, the yield (analysis) 16 parts (85% of theory)

jo from bp 100 ° C.

Example 7

Analogously to Example 3a, a catalyst is made from 230 parts of aluminum phosphate, 75 parts of boric acid and

Jj 25 parts of urea. 130 parts of this catalyst are filled into the reactor, heated to 400 ^° C. and charged with a mixture of 7.6 parts of formaldehyde dimethyl acetal and 88 parts of methyl propionate over the course of 30 minutes. The residence time is 5.9 seconds. The reaction mixture is analyzed by gas chromatography and fractionally distilled. The conversion to methyl methacrylate, based on formaldehyde dimethyl acetal, is 76%, the yield (analysis) is 7.6 parts (80% of theory) of 100 ° C.

Example catalyst

Temperature residence time conversion yield

in seconds% of theory

⁰ C%

AlPO ₄ , H ₃ BO ₃ *) AlPO ₄ , ThO ₂ , H ₃ BO ₃ **) aluminum silicate (45% Al ₂ O ₃ +55% SiO ₂ )

The reaction is carried out as in Example 2
The catalysts are produced analogously to Example 3a
*) (from 230 parts of AlPO ₄ and 75 parts of H ₃ BO ₃ ).
**) (from 230 parts of AlPO ₄ , 300 parts of ThO ₂ and 75 parts of H ₃ BO ₃ ). 6.1
5.9
5.9

62
66
15th

65
69
25th

_v , -,. 65 catalysts in the form of pills of one diameter

Vergieicnsversucn of 3-4 mm filled and the reactor then on the in

The temperature indicated in the table is heated in an electrically heatable glass tube

100 cm ^{3 of} the reactor indicated in the table below is then filled with a mixture every hour

ίο

88 g of methyl propionate and 7.6 g of formaldehyde dimethyl acetal (Methylal) is charged and the discharge is analyzed by gas chromatography. The receive

The results are summarized in the following table:

catalyst temperature sales Yield (mol%) space-time g / 1 hour (Mol%) Methacrylic acid yield Methylal methyl ester ( ⁰ C)

Sodium phosphate according to GB-PS 7 85 100 350

Aluminum phosphate according to Example 2350

79.0

Claims (1)

Patent claims: 1. Process for the preparation of methacrylic acid and methyl methacrylate of the formula CH ₁ CH ₂ = CC-OR ¹ O (D wherein R ^{1 represents} a hydrogen atom or a methyl group by reacting propionic acid or methyl propionate of the formula CH ₃ -CH ₂ -C-OR ¹ (H)