NO142747B - PROCEDURE FOR THE PREPARATION OF METHYL OR ETHYL ESTERS OF ACRYLIC OR METACRYLIC ACID - Google Patents

Description

The present invention relates to a new process for the production of methyl or ethyl esters of acrylic or methacryl

acid when converting gaseous acrolein or methacrolein, even

tually in a mixture with propene or of a gas mixture produced

prepared by catalytic oxidation of propene, with oxygen and with gaseous methanol or ethanol in the presence of a catalyst.

The esters of acrylic and methacrylic acids are valuable intermediates, especially in the production of polymers. Various methods are known for the production of acrylic esters, e.g. from ethene cyanohydrin

or acrylonitrile or by the reaction of acetylene with carbon monoxide and an alcohol in the presence of nickel carbonyl, nickel salts or nickel complexes, see Kirk-Othmer, Encyclopedia of Chemical Technology, 2nd ed., vol. 1 (1963), pp. 293-300. In a commonly used process

propene is oxidized to acrolein with oxygen or gases containing free oxygen, in the presence of an oxidation catalyst. The acrolein obtained is further oxidized to acrylic acid by catalytic oxidation. When isobutene is used, methacrolein and methacrylic acid are obtained as oxidation products. In both cases, the produced acrylic acid or methacrylic acid is then converted to the corresponding ester with a lower aliphatic alcohol in a further process step.

However, this process is complicated due to the many process steps and requires expensive cleaning steps and recirculation. Furthermore, the overall yield of acrylic or methacrylic ester obtained by this method is unsatisfactory.

It has recently been proposed to carry out the oxidation of acro-

lein or methacrolein and the subsequent esterification of acrylic

or the methacrylic acid in a one-step process using a palladium catalyst. According to DE-OS 2 025 992 forward-

esters of unsaturated carboxylic acids are thus produced in a one-step process by reacting an unsaturated aldehyde, an alcohol and molecular oxygen in the presence of metallic palladium as a catalyst

sator. According to DE-OS 2 162 826, the desired esters are obtained by reacting propene or isobutene with oxygen or a lower alcohol in the presence of a catalyst consisting of palladium metal which has been previously treated with phosphoric acid. In this case too, the obtained values for conversion and selectivity are very modest.

It has now been found according to the present invention

that it is possible to produce methyl or ethyl esters of acrylic

or methacrylic acid with high yield and selectivity when reacting acrolein or methacrolein with molecular oxygen and methanol or ethanol in gas phase with short reaction times in the presence of suitable metal oxide catalysts containing molybdenum, vanadium and/or tungsten and possibly further metallic elements.

It is surprising that acrolein or methacrolein can be converted into the desired esters with high selectivity when working under the above conditions, as it is well known that methanol and ethanol are easy to oxidize. It is actually known that catalysts containing molybdenum oxide are used for the catalytic oxidation of alcohols to the corresponding aldehydes, especially in the oxidation of methanol to formaldehyde. On the other hand, it is known that metal oxide catalysts containing molybdenum can be used for the oxidation of unsaturated aldehydes to the corresponding acids. However, the applicants have established that the catalysts used according to the present invention give very poor results when they are used to promote the esterification of acrylic or methacrylic acid at the operating conditions (temperature, pressure, residence time etc.) used according to the present invention. If one e.g. repeating the experiment in example 2 (which will be described later), but replacing the acrolein with a corresponding amount of acrylic acid, the conversion of acrylic acid was approx. 50%, and only 20% of the acrylic acid was converted into the desired ester.

This shows that the behavior of the catalysts in the process according to the invention is surprising. The reaction mechanism cannot probably be explained by the fact that acrylic acid is produced followed by a conversion of this to the ester, where both reactions are promoted by the catalysts.

It should be noted that the use of molybdenum oxide to promote the esterification of acrylic acid is described in US-PS 3 442 935. In order to achieve satisfactory conversion and selectivity, however, it is necessary here to work mainly in liquid phase with unusually long residence times, small delivery quantities and in case of overpressure. The present invention, which allows the achievement of high yields and selectivities by operation under simple and economically appropriate conditions, is thus all the more surprising.

More specifically, the method according to the invention is characterized in that the reaction is carried out in the presence of a catalyst with the general formula where Me denotes an iron, cobalt, nickel, copper, zinc, silver or cadmium atom, a has a value of 6-12, b has a value of 1-6, c has a value of 0-5, d has a value of 1-6, x has a value of 20.5-58.5, y has a value of 21 -61.5 and z has a value of

23.5-76.5, at a temperature of 180-320°C and a pressure in the range from atmospheric pressure to approx. 5 kp/cm 2 and with residence times on

0.1-40 p.

Catalysts with the formula Mo a V, b Me c 0 x are preferred.

When using the above-mentioned catalysts under the mentioned conditions

hold, it is possible to obtain methyl or ethyl esters of acrylic or methacrylic acid with high yield and good selectivity. The method according to the invention is particularly suitable for the production of methyl acrylate from acrolein.

For the production of the catalysts used in the method according to the invention, the respective metal compounds are dissolved in water, the aqueous solution is evaporated until it is dry and the residue is heated to high temperatures. According to one embodiment, the metal compounds are dissolved in an aqueous ammonia solution, possibly at temperatures above room temperature. The resulting solution is then evaporated to dryness at temperatures of up to 130°C. Water can be added to the solid residue one or more times to evaporate again. The solid residue is then heated at temperatures of 130 - 600°C for a period of at least two hours. The heating is preferably carried out in an atmosphere of nitrogen or another inert gas as protection. Metal compounds which are water-soluble and which can be converted into metal oxides under the heating conditions are preferably used in the production of the catalysts. Particular examples of such metal compounds are ammonium paramolybdate ammonium metavanadate, ammonium tungstate, tungstic acid, copper nitrate, copper acetate, zinc nitrate, ferrous nitrate and ferroxalate. Cataly-

sators containing aluminum oxide, silicon dioxide, zirconium oxide, titanium oxide or magnesium oxide which carry in an amount of up to approx. 99 parts by weight per 100 parts by weight of catalyst can be used in the method according to the invention. The preferred carrier is silicon dioxide.

When producing supported catalysts, the metal compounds can be precipitated in the presence of the support, or the support can be impregnated with a solution of the metal salts and then dried and heated to high temperatures.

The catalysts used in the method according to the invention can be used in the form of a fixed layer, a moving layer or a fluidized layer. According to the method according to the invention, a gaseous mixture of acrolein or methacrolein, oxygen or a gas containing free oxygen, and methanol or ethanol is brought into contact with the catalyst. The molar ratio between acrolein or methacrolein and oxygen in the gas mixture can be between 0.1:1 and 4:1, preferably between 0.2:1 and 2:1, and the molar ratio between acrolein or methacrolein and methanol or ethanol can be between 0, 2:1 and 2:1, preferably between 0.3:1 and 1.5:1.

If the alcohol in the method according to the invention is used

in an amount that is less than the stoichiometrically necessary amount for the formation of the acrylic or methacrylic ester, a mixture of acrylic or methacrylic acid and the methyl or ethyl ester of acrylic or methacrylic acid is obtained as a reaction product.

A gas mixture of 1-8 volume percent acrolein or methacrolein, 0.5-10 volume percent methanol or ethanol and 0.5-20 volume percent oxygen can suitably be used in the method according to the invention. The method is preferably carried out in the presence of inert gases such as e.g. nitrogen or carbon dioxide. Water vapor is preferably also added as a diluent to the gas mixture. Gas mixtures formed by catalytic oxidation of propene with added

addition of methanol or ethanol and possibly oxygen or a gas containing free oxygen can be used in the method according to the invention.

The oxygen used as an oxidizing agent can be in the form of pure oxygen or in the form of gases containing oxygen, e.g. air. The method according to the invention can suitably be carried out at temperatures in the range from ISO to 320°C. At reaction temperatures above 3 20°C side reactions take place as a result of further oxidation, while at temperatures below 180°C a markedly decreasing yield is obtained. The preferred reaction temperature lies in the range from 200 to 28 (Pc. The method according to the invention can be carried out at atmospheric pressure or at an overpressure of up to 5 kp/cm<2>. The residence time is 0.1 - 40 seconds, preferably 1-20 seconds.

Under the conditions described above, the conversion is usually

at least 90 mole percent calculated on acrolein. The selectivity for formation of e.g. methyl acrylate is at least 85 mole percent when it

applies to converted acrolein.

The methyl or ethyl esters of acrylic or methacrylic acid which are produced according to the invention can be separated from the reaction gas stream by usual methods, e.g. by lowering into water and recovery by fractional distillation.

The invention will be further illustrated by the following examples.

Example 1

8.828 g of ammonium paramolybdate (NH^) ^ 0- j^ 2A• , 2.114 g of tungstic acid I^WO^ and 1.004 g of ammonium metavanadate NH^VO^ are dissolved at 80°C

in 200 ml of an 18% by weight aqueous ammonia solution. The resulting solution is slowly evaporated to dryness. The solid residue is ground and then dried in an oven at 120°C for one hour. The resulting powder is homogeneously mixed with a solution of 6.710 g of copper nitrate Cu(NOg)2•3H20 in 50 ml of water. The resulting suspension is slowly evaporated at 95°C until dry. The solid residue is heated in an oven at 170°C for 30 minutes and then ground. The resulting powder is converted into a paste with 50 ml of water and slowly evaporated at 95°C until dry. The solid residue obtained is heated in an oven at 180°C for 30 minutes and then ground. The addition of water to the powder, the evaporation, the heating to 190-200°C and the grinding of the solid residue are repeated several times until the evolution of nitrous gases ceases. The solid residue is then heated for 30 minutes at 300°C, cooled and suspended

in 50 ml of water, evaporated to dryness, heated again for 30 minutes at 300°C, cooled again and resuspended in 50 ml of water. After the water has evaporated, the solid residue is heated in a stream of nitrogen for two hours at 300°C and for a further two hours at 380°C.

Example 2

3 cm 3 of a catalyst prepared according to example 1 and sieved through a sieve with a free mesh size of 48 - 325 mesh (Tyler) corresponding to nominal openings of 45 - 300 micrometers and with a particle size of 50 - 200 micrometers is fed into a stainless steel reactor with an internal diameter of 8 mm. A gas mixture with the following composition (in percentage by volume) is introduced at the upper end of the reactor: Acrolein 1.3%, methanol 2.5%, oxygen 2.1%, water vapor 18.0%, nitrogen 76.1%.

The process is carried out with a catalyst in a solid layer at a temperature of 228°C and atmospheric pressure. The residence time of the gas mixture is 5.6 seconds. The gas coming out of the reactor is condensed at -30°C. Gas chromatographic analysis of the gas stream and the condensate gives the following values: Conversion of acrolein 9 9.6 mole percent. Selectivity for the formation of methyl acrylate 92.3 mole percent calculated on converted acrolein and 93 mole percent calculated on converted methanol.

Example 3

84.8 g of ammonium paramolybdate, 14 g of ammonium metavanadate and 20 g of tungstic acid are dissolved in a mixture of 1000 ml of water and 450 ml of a

32% by weight aqueous ammonia solution at 60°C. The resulting clear solution is evaporated at 95°C down to a volume of 800 ml, and 300 ml of a 32% by weight aqueous ammonia solution and 300 ml

water is added to the resulting concentrate at 80°C. 145 ml of an ammonia solution of a silica sol (Ludox AS, 30% by volume SiO2)

Diluted with 350 ml of water, the resulting solution is added at this temperature. The mixture is then evaporated at 95°C to dryness, and the solid residue is ground and sieved. The particles with grain sizes of 100-150 micrometers are dried in an oven at 120°C for 2.5 hours. The resulting granules are then heated for 1.5 hours at 415°C in a stream of nitrogen, slowly cooled to 25°C and finally heated in a stream of nitrogen at 400°C for 3.5 hours.

Example 4

30 cm 3 of a catalyst prepared as indicated in example 3 and

with grain sizes of 100 - 150 micrometers are arranged in the form of a solid layer in an AISI 316 stainless steel reactor with an internal diameter of 15 mm. A gas mixture with the following composition (volume percentage) is supplied to the upper end of the reactor: Acrolein 1.5%, methanol 1.9%, air 15.0%, water vapor 20.0%, nitrogen 61.6%. The procedure is carried out at 2 4 9°C and atmospheric pressure and a residence time of 3.8 seconds. The gases emerging from the reactor contain 1.17% by volume methyl acrylate, 0.12% by volume acrylic acid, 0.02% by volume acrolein, 0.5% by volume carbon dioxide, 0.02% by volume methyl acetate, 0.11% by volume methyl formate and 0.49% by volume methanol .

Example 5

13.3 g of ammonium paramolybdate, 3.2 g of tungstic acid and 1.5 g of ammonium metavanadate are dissolved at 80°C in 400 ml of a 16% by weight aqueous ammonia solution. The resulting solution is slowly evaporated at 95°C until dry, and the residue is then heated at 120°C

for 2.5 hours and at 300°C for a further 2 hours. The obtained solid is ground into a powder with a grain size of 50 - 100 micrometres

8.9 g of iron (II) oxalate is dissolved in 120 ml of a 65% by weight nitric acid containing 5 ml of a 30% by weight aqueous hydrogen

peroxide solution. The obtained solution is slowly evaporated to dryness, 100 ml of water is added to the resulting solid residue, and the obtained powder of molybdenum oxide, vanadium oxide and tungsten oxide is added with vigorous stirring. The mixture is slowly evaporated at 95°C and with continuous stirring until dry and then heated to 180°C. The solid residue obtained is finely ground, dispersed in 100 ml and again evaporated to dryness. These steps are repeated three times in the manner indicated above. The resulting solid residue is finally slowly heated to 380°C over a period of three hours and then held at this temperature for a further three hours under nitrogen.

Example 6

6 cm 2 of a catalyst prepared as indicated in Example 5 is ground and sieved. The catalyst with grain sizes of 50~150 micrometers is fed into an AISI 316 stainless steel reactor with an internal diameter of 8 mm. A gas mixture with the following composition (in percent by volume) is introduced at the upper end of the reactor: Acrolein 4.0%, methanol 2.9%, air 29.0%, water vapor 33.0%, nitrogen 31.1%. The process is carried out with the catalyst in a solid layer at a temperature of 255°C and atmospheric pressure and a residence time of 3.2 seconds.

The gases coming out of the reactor" contain (calculated in volume percentage) 0.4% acrolein, 1.5% methyl acrylate, 1.5% acrylic acid, 1.4% carbon dioxide, 0.05% acetic acid and 0.04% methyl acetate.

Example 7

Dissolve 6.92 g of cobalt acetate Co(CH3COO)2•4H20 in 75 ml of water.

1.1 g of ammonium metavanadate, 8.9 g of ammonium paramolybdate and 2.2 g of tungstic acid are each dissolved in 200 ml of a 16% by weight aqueous ammonia solution at 80°C in a 250 ml beaker. The obtained solution is heated to the boiling point and slowly evaporated.

The solid residue is dried in an oven at 120°C for two hours. The cobalt acetate solution is added to the resulting solid residue, and the mixture is heated to the boiling point and slowly evaporated to dryness. The residue is then heated to a temperature of 170°C

and held at this temperature for 20 minutes. After cooling, the product is treated with 100 ml of water and again heated to the boiling point and evaporated to dryness. The solid residue is heated to 200°C and held at this temperature for 30 minutes. 50 ml of water is added to the solid product obtained, and the mixture is heated to the boiling point and evaporated to dryness. The residue is then heated to 200°C and

held at this temperature for an additional 30 minutes. The product is finally heated in a stream of nitrogen at 280°C for two hours and at 380°C for a further two hours.

Example 8

6 cm<3> of a catalyst prepared as indicated in Example 7 is ground, sieved to a grain size of 100-150 micrometers and introduced into an AISI 316 stainless steel reactor with an internal diameter of 8 mm. A gas mixture with the following composition (in percent by volume) is introduced at the upper end of the reactor: Acrolein 2.1%, methanol 3.0%, air 15.0%, water vapor 25.0%, nitrogen 54.9%.

The process is carried out with the catalyst in a solid layer at a temperature of 231°C and atmospheric pressure and a residence time of 4.7 seconds. Under these conditions, the acrolein conversion is 100%. The selectivities for the formation of methyl acrylate and acrylic acid calculated on converted acrolein are respectively 90.8% and 3.2%.

The selectivities for the formation of methyl acrylate, methyl formate and

dimethyl ether calculated on converted methanol is respectively 92%, 2% and 6%.

Example 9

8.83 g of ammonium paramolybdate, 1.1 g of ammonium metavanadate and 2.15 g of tungstic acid are dissolved at 80°C in 200 ml of a 16% by weight aqueous ammonia solution. The solution is evaporated at 95°C to dryness and finally dried at 200°C for 30 minutes. The product obtained is finely ground, and the resulting powder is suspended in 50 ml of water. A solution of 3.69 g of zinc carbonate (ZnCO 3 ) dissolved in 15 ml of a 65% by weight nitric acid and 35 ml of water is slowly added to the resulting aqueous suspension. The mixture is slowly evaporated at 95°C until dry, and the residue is heated to 180°C and held at this temperature for 20 minutes. The solid residue is cooled, treated with 100 ml of water, heated to 95°C and slowly evaporated to dryness. The residue is finally heated to 200°C and held at this temperature for 30 minutes. After cooling, the product is treated with 100 ml of water, heated to 95°C and slowly evaporated to dryness. The temperature is then raised to 200°C and held at this level for 30 minutes. The product is finally heated in a stream of nitrogen at 280°C for two hours and at 380°C for a further two hours.

Example 10

The catalyst obtained according to Example 9 is sieved and 6 cm 3 of a sieve portion with grain sizes of 50-150 micrometers is fed into a stainless steel reactor with an internal diameter of 8 mm. A gas mixture obtained by catalytic oxidation of propene to acrolein and enriched with methanol is introduced at the upper end of the reactor. In this oxidation, a mixture of propene and oxygen diluted with nitrogen and water vapor is brought together with the catalyst. Methanol is added to the resulting gaseous reaction products at 170°C. A gas mixture with the following composition (in percent by volume) is obtained: 0.5% propene, 3.1% acrolein, 0.2% acrylic acid, 1.2% carbon monoxide and carbon dioxide, 6.2% oxygen, 17.3% water vapor, 4 .6% methanol and 66.9% nitrogen.

The process is carried out with the catalyst in a solid layer at a temperature of 258°C and normal pressure and a residence time of 4.7 seconds. Under these conditions, a reaction gas with the following composition in volume percentage is obtained: 0.3% propene, 0.1% acrylic acid, 1.8% carbon monoxide and carbon dioxide, 1.1% methanol, 0.1% methyl acetate, 0.2% methyl formate , 3.1% methyl acrylate and 0.1% acrolein.

The acrolein conversion is thus 96.9%, and the selectivity for the formation of methyl acrylate is 80% calculated on converted acrolein and converted propene and 91.5% calculated on converted methanol.

Example 11

8.8 g of ammonium paramolybdate, 2.1 g of tungstic acid and 1.1 g of ammonium metavanadate are dissolved at 80°C in 200 ml of a 16% by weight aqueous ammonia solution. The solution is heated to the boiling point and slowly evaporated to dryness. The obtained solid residue is finely ground and dried at 120° C for one hour. The resulting fine powder is converted into a paste with a solution containing 6.7 g of copper nitrate dissolved in 50 ml of water. The resulting mixture is slowly evaporated with stirring, and the product obtained is dried at 180°C for 20 minutes. After cooling, the product is treated with 20 ml of water, again evaporated to dryness and then heated to 300°C. After cooling, the above-mentioned treatment with water, evaporation and heating is repeated two more times. The solid product is finally heated under nitrogen at 280°C for two hours and at 380°C for another two hours. 2.524 g of the product obtained is finely ground and suspended in 20 ml of water. The resulting suspension is heated to 30°C, and 2 ml of a 30% by weight aqueous silica solution (Ludox AS) is added. The mixture is slowly evaporated at 95°C to dryness and heated in an oven at 120°C for two hours. The product is then heated in a stream of nitrogen at 400°C for two hours.

Example 12

2 cm^ of the catalyst produced according to example 11 with a grain size of 50 - 150 micrometers is fed into a stainless steel reactor with an internal diameter of 8 mm. A gas mixture with the following composition (in percent by volume) is introduced at the upper end of the reactor: Acrolein 2.05%, methanol 3.3%, propene 0.1%, acrylic acid 0.1%, oxygen 4.0%, water vapor 25 .0%, carbon monoxide and carbon dioxide 1.2%. The rest consists mainly of nitrogen. The process is carried out with the catalyst in a solid layer at a temperature of 250°C and normal pressure and a residence time of 3 seconds. The resulting reaction gas contains (by volume) 1.8% methyl acrylate, 0.1% acrylic acid, 0.05% methyl acetate, 0.05% propene, 0.05% acrolein, 1.8% carbon monoxide and carbon dioxide, 0.05 % methyl formate and 1.35% methanol. The rest consists mainly of oxygen, water vapor and nitrogen.

The acrolein conversion is 97.8% and the methanol conversion 61%. The selectivity for the formation of methyl acrylate is 90.2% calculated on converted acrolein and 91% calculated on converted methanol.

Example 13

8.8 g ammonium heptamolybdate, 1.01 g ammonium metavanadate and

2.15 g of tungstic acid is dissolved at 80°C in 200 ml of a 16% by weight aqueous ammonia solution. The obtained solution is slowly dried at 95°C, and the residue is finely ground and heated at 120°C for two hours. The product is suspended in 50 ml of water and a solution of 4.72 g of silver nitrate in 100 ml of water is added. The mixture is slowly evaporated until it is dry, and the solid residue is heated to 200°C for 20 minutes. After cooling, the product is treated with 75 ml of water and slowly evaporated to dryness, after which the residue is heated to 200°C for 30 minutes. These steps are repeated three times. The product is finally heated in a stream of nitrogen at 280°C for two hours and at 410°C for a further two hours.

Example 14

6 cm<3> of the catalyst prepared according to example 13 is ground and sieved to a sieve fraction with a grain size of 100 - 150 micrometres. This fraction is fed into a stainless steel reactor with an internal diameter of 8 mm. A gas mixture with the following composition (in percent by volume) is introduced at the upper end of the reactor: 0.9% acrolein, 2.4% methanol, 2.5% oxygen, 5.0% water vapor and the remainder mainly nitrogen. The process is carried out with the catalyst in a solid layer at a temperature of 2 6 5°C and normal pressure and a residence time of three seconds. The gaseous reaction product is analyzed by gas chromatography. The following results are obtained: Acrolein conversion 80%, methanol conversion 31.8%, selectivity for the formation of methyl acrylate 93% calculated on converted acrolein and 94% calculated on converted methanol.

Example 15

8.82 g of ammonium paramolybdate, 1.01 g of ammonium metavanadate and 2.14 g of tungstic acid are dissolved at 80°C in 200 ml of a 16% by weight aqueous ammonia solution. The mixture is slowly evaporated at 95°C without stirring until dry and the residue is dried in an oven at 120°C for two hours. The solid residue is ground and suspended in 50 ml of water, and a solution of 6.9 2 g of nickel acetate Ni(CH3COO)2•4H20 in 100 ml of water is added. The mixture is heated to the boiling point and slowly evaporated with stirring until dry. The product is finally dried at 200°C and held at this temperature for 20 minutes. The product obtained is treated with 100 ml of water, evaporated again with stirring until it is dry and dried at 200°C. These steps are repeated three more times. The product is finally heated in a stream of nitrogen at 280°C

for two hours and at 400°C for a further three hours.

Example 16

6 cm<3> of the catalyst produced according to example 15 with a particle size of 100 - 150 micrometers is fed into a stainless steel reactor with a diameter of 8 mm. A gas mixture with the following composition (in percent by volume) is introduced at the upper end of the reactor: 1.7% methanol, 0.9% acrolein, 3.2% oxygen, 23.0% water vapor

and the rest mainly nitrogen. The process is carried out with the catalyst in a solid layer at a temperature of 227°C and normal pressure and a residence time of 4.5 seconds. Under these conditions, the acrolein conversion is 73%, and the selectivity for the formation of methyl acrylate is 78% calculated on converted acrolein and 83% calculated on converted methanol.

Example 17

8.8 g of ammonium paramolybdate, 1.1 g of ammonium metavanadate and 0.84 g of tungstic acid are dissolved at 80°C in 200 ml of a 16% by weight aqueous ammonia solution. The solution is evaporated slowly at 95°C, and the residue is dried in an oven at 120°C for two hours. The product is finely ground,

and the solid is suspended in 100 ml of water with stirring. The suspension is treated with a solution of 4.72 g of cadmium carbonate in 200 ml of 65 per cent nitric acid. The mixture is slowly evaporated at 95°C until dry, dried at 200°C and held at this temperature for 30 minutes. The resulting solid product is taken up in 100 ml of water

and evaporate slowly at 95°C with stirring until dry. The product is finally heated in a stream of nitrogen at 280°C for two hours and at 400°C for a further two hours.

Example 18

3 cm<3> of the catalyst produced according to example 17 with a particle size of 100 - 150 micrometers is fed into a stainless steel reactor with an internal diameter of 8 mm. A gas mixture with the following composition (in percent by volume) is introduced at the upper end of the reactor: 1.7% methanol, 0.8% acrolein, 0.1% propene, 2.6% oxygen, 0.6% carbon monoxide and carbon dioxide, 18.0% water vapor and the rest mainly nitrogen. The process is carried out with the catalyst in a solid layer at a temperature of 292°C and normal pressure and a residence time of 1.8 seconds. A gas chromatographic analysis of the reaction gas shows an acrolein conversion of 50% and a selectivity for the formation of methyl acrylate of 85% calculated on converted acrolein.

Example 19

75 ml of a 30% by weight aqueous ammonia solution and 2 ml of a 30% by weight aqueous hydrogen peroxide solution are added to 120 ml of water. 5.97 g (NH^) jqW12041 " ^H2°' 3.92 9 ammonium paramolybdate and 2.675 g ammonium vanadate are added to this solution while stirring. The solution is slowly evaporated while stirring up to a temperature

at 95°C until dry and finally dried in an oven at 120°C for two hours. The product is then finely ground and suspended in 50 ml of water, after which a solution of 5.76 g of copper nitrate in 50 ml of water is added. The mixture is slowly evaporated at 95°C until it is dry and finally heated to 200°C and kept at this temperature for 20 minutes. After cooling, the product is treated with 50 ml of water, evaporated at 95°C until dry and heated to 200°C. The solid product obtained is again cooled, taken up in 50 ml of water, evaporated at 95°C until dry and finally heated at 200°C for one hour. The product is then heated in a stream of nitrogen at 280°C for two hours and at 400°C for a further two hours.

Example 20

6 cm^ of the catalyst produced according to example 19 with a particle size of 50 - 150 micrometers is fed into a stainless steel reactor with an internal diameter of 8 mm. A gas mixture with the following composition (in percent by volume) is introduced at the upper end of the reactor: 1.8% methanol, 1.2% acrolein, 2.6% oxygen, 23.0% water vapor and the rest mainly nitrogen. The process is carried out with the catalyst in a moving bed at a temperature of 235°C and atmospheric pressure and a residence time of 4 seconds. The reaction gas is analyzed by gas chromatography. The acrolein conversion is 60%, and the selectivity for the formation of methyl acrylate is 78% calculated on converted acrolein.

Example 21

6.62 g of ammonium paramolybdate, 2.24 g of tungstic acid and 2.51 g of ammonium metavanadate are dissolved in 200 ml of a 16% by weight aqueous ammonia solution at 80°C with stirring. The solution is then slowly evaporated at 90-100°C until dry, and the solid residue is heated in an oven at 120°C for two hours. The product is then finely ground and suspended in 50 ml of water, after which a solution of 5.76 g of copper nitrate in 50 ml of water is added with stirring. The mixture is evaporated slowly at 95°C until dry, and the solid residue is heated to 200°C and held at this temperature for 20 minutes. The solid product is then treated with 50 ml of water, evaporated to dryness and heated at 200°C for 30 minutes. These steps are repeated twice. The solid product is finally heated in a stream of nitrogen at 280°C for two hours and at 380°C for a further two hours.

Example 22

6 cm<3> of the catalyst prepared according to example 21 with a grain size of 50 - 150 micrometers is fed into an AISI 316 stainless steel reactor with an internal diameter of 10 mm. A gas mixture with the following composition (in percent by volume) is introduced at the upper end of the reactor: 4.5% acrolein, 2.4% methanol, 0.2% propene, 10.3% oxygen, 1.5% carbon monoxide and carbon dioxide, 18.7% water vapor and the rest mainly nitrogen. The process is carried out with the catalyst in a solid layer at a temperature of 252°C and atmospheric pressure and a residence time of 3 seconds. Under these reaction conditions, the acrolein conversion is 99% and the methanol conversion 100%. The converted gases contain 2.4 volume percent methyl acrylate and 2.0 volume percent acrylic acid.

Example 2 3

6.62 g of ammonium paramolybdate, 5.60 g of tungstic acid and 1.01 g of ammonium metavanadate are dissolved in 200 ml of a 16% by weight aqueous ammonia solution at 80°C with stirring. The solution is then slowly evaporated to dryness and the residue is heated in an oven at 120°C for two hours. The product is finely ground and suspended in 500 ml of water, after which a solution of 5.76 g of copper nitrate in 50 ml of water is added. The mixture is slowly evaporated at 95°C until dry, and the residue is heated to 200°C and held at this temperature for 15 minutes.

The solid residue is then suspended in water, evaporated to it

is dry and heated to 200°C. This procedure is repeated three times. The product is finally heated in a stream of nitrogen

as in example 21.

Example 24

5 cm<3> of the catalyst produced according to example 23 with a grain size of 100 - 150 micrometers is fed into a stainless steel reactor with an internal diameter of 8 mm. A gas mixture with the following composition (in percent by volume) is introduced at the upper end of the reactor: 1.8% acrolein, 3.2% methanol, 3.4% oxygen, 15.5% water vapor and the remainder mainly nitrogen. The process is carried out with the catalyst in a solid layer at a temperature of 220°C and atmospheric pressure and a residence time of 4 seconds. Under these conditions, the acrolein conversion is 98.5%. The selectivity for the formation of methyl acrylate is 96% calculated on converted acrolein and 98% calculated on converted methanol.

Example 25

8.09 g of ammonium paramolybdate, 1.12 g of tungstic acid and 2.01 g of ammonium metavanadate are introduced at 80°C into 200 ml of a 16% by weight aqueous ammonia solution. The mixture is heated to 90-95°C for two hours. A clear orange solution is obtained. At a temperature of 90-95°C, a solution of 5.76 g of copper nitrate in 100 ml of a 32% by weight aqueous ammonia solution is added. The mixture is evaporated slowly until it is dry, and the solid residue is heated to 260°C and held at this temperature for 30 minutes. After cooling, the residue is heated with 100 ml of water and again slowly evaporated until it is dry. The product is finally heated in a stream of nitrogen at 280°C for two hours and at 400°C for a further two hours.

Example 26

6 cm 3 of the catalyst produced according to example 25 with a particle size of 50 - 150 micrometers is fed into an AISI 316 stainless steel reactor with an internal diameter of 8 mm. A gas mixture with the following composition (in percent by volume) is introduced at the upper end of the reactor: 3.1% acrolein, 4.3% methanol, 0.2% propene,

0.8% carbon monoxide and carbon dioxide, 15.5% water vapor, 5.2% oxygen and the rest mainly nitrogen. The process is carried out with the catalyst in a solid layer at a temperature of 260°C and a pressure of 0.5 kg/cm<2>

as well as a residence time of three seconds. Under these conditions, the acrolein conversion is 98.5% and the selectivity for the formation of methyl acrylate is 96.7% calculated on converted acrolein and 98.3% calculated on converted methanol.

Example 27

5.88 g of ammonium paramolybdate, 4.48 g of tungstic acid and 2.01 g of ammonium vanadate are dissolved at 80°C in 200 ml of a 16% by weight aqueous ammonia solution. At this temperature, a solution of 5.76 g of ammonium nitrate in 100 ml of a 32% by weight aqueous ammonia solution is added to the clear orange solution obtained. The mixture is slowly evaporated to dryness, and the residue is heated to 260°C and held at this temperature for 30 minutes. After cooling, the product is treated with 100 ml of water, re-evaporated slowly until dry and finally heated to 400°C for two hours.

. Example 28

6 cm of the catalyst produced according to example 27 with a grain size of 100-150 micrometers is placed in an AISI 316 stainless steel reactor with an internal diameter of 8 mm. A gas mixture with the following composition (in percent by volume) is introduced at the upper end of the reactor: 1.1% acrolein, 2.4% methanol, 16.2% water vapor, 2.6% oxygen and the remainder mainly nitrogen. The process is carried out with the catalyst in a solid layer at a temperature of 262°C and atmospheric pressure together with a residence time of 3.5 seconds. Under these reaction conditions, the acrolein conversion is 93% and the selectivity for the formation of methyl acrylate is 96.7% calculated on converted acrolein and 97.2% calculated on converted methanol.

Example 29

7.36 g of ammonium paramolybdate, 3.36 g of tungstic acid and 1.51 g of ammonium metavanadate are dissolved at 80°C in 200 ml of a 16% by weight aqueous ammonia solution. The mixture is heated to 90°C. A clear orange solution is finally obtained, and a solution of 5.76 g of copper nitrate in 100 ml of a 32% by weight aqueous ammonia solution is added. The mixture is heated to boiling point and slowly evaporated to dryness. The residue is heated to 260°C and held at this temperature for 30 minutes. After cooling, the residue is treated with 100 ml of water, evaporated to dryness and heated under nitrogen at 280°C

for two hours and 4 00°C for another two hours.

Example 30

6 cm<3> of the catalyst prepared according to Example 29 with a grain size of 100-150 micrometers is fed into an AISI 316 stainless steel reactor with an internal diameter of 8 mm. A gas mixture with the following composition (in percent by volume) is introduced at the upper end of the reactor: 1.2% acrolein, 2.1% methanol, 12.6% water vapor, 3.2% oxygen and the remainder mainly nitrogen. The process is carried out with the catalyst in a solid layer at a temperature of 260°C and atmospheric pressure and a residence time of 3.6 seconds. The reacted gases are analyzed by gas chromatography. The result of these shows an acrolein conversion of 95.2% and a selectivity for the formation of methyl acrylate of 92.5% calculated on converted acrolein and 98.3% calculated on converted methanol.

Example 31

8.1 g of ammonium paramolybdate, 2.1 g of ammonium metavanadate and 1.12 g of tungstic acid are dissolved at 80°C in 200 ml of a 16% by weight aqueous ammonia solution. The mixture is heated at 80°C until a clear orange solution is obtained. The solution is heated to the boiling point, 14 ml of a silica sol with a silicon dioxide content of 30% by weight (Ludox AS) is added, and a solution of 5.8 g of copper nitrate in 100 ml of a 32% by weight aqueous ammonia solution is finally added at 98°C. The mixture is slowly evaporated to dryness and finally heated at 420°C for three hours in a stream of nitrogen.

Example 32

6 cm^ of the catalyst described in example 31 with a grain size of 50-150 micrometers is fed into an AISI 316 stainless steel reactor with an internal diameter of 10 mm. A gas mixture with the following composition (in percent by volume) is introduced at the upper end of the reactor: 0.1% acrylic acid, 2.3% acrolein, 0.2% propene, 3.6% methanol, 17.6% water vapor, 0, 6% carbon monoxide and carbon dioxide, 3.6% oxygen and the rest mainly nitrogen. The process is carried out with the catalyst in a solid layer at 269°C, an overpressure of 400 ram Hg and a residence time of 1.5 seconds. Under these reaction conditions, the acrolein conversion is 99%. The selectivity for the formation of methyl acrylate is 89% calculated on converted acrolein and 93.6% calculated on converted methanol.

Example 33

10.3 g of ammonium paramolybdate and 2.3 g of tungstic acid are introduced into 200 ml of a 16% by weight aqueous ammonia solution at 80°C. The mixture is heated at 95°C until everything has dissolved. A solution of 5.8 g of copper nitrate in 100 ml of a 32% by weight aqueous ammonia solution is then added to the solution. The mixture is slowly evaporated at 95°C until dry. After cooling, the solid residue is treated with 100 ml of water and evaporated again. it is dry. The product is finally heated in a stream of nitrogen at 280°C for 2 hours and at 380°C for a further 2 hours.

Example 34

6 cm 3 of the catalyst prepared according to example 3 3

with a grain size of 50-150 micrometers is fed into an AISI 316 stainless steel reactor. A gas mixture with the following composition (in percent by volume) is introduced at the upper end of the reactor: 0.8% acrolein, 1.3% methanol, 13.0% water vapor, 3.5% oxygen and the remainder mainly nitrogen. The process is carried out with the catalyst in a solid layer at 225°C

and atmospheric pressure as well as a residence time of 3 s. Under these reaction conditions, the acrolein conversion is 70% and the selectivity for the formation of methyl acrylate 72% calculated on converted acrolein and 81% calculated on converted methanol.

Example 35

8.9 g of ammonium paramolybdate and 2.1 g of ammonium metavanadate are introduced

at 80°C into 200 ml of a 16% by weight aqueous ammonia solution. The mixture is heated at 90°C until a clear solution is obtained. 5.8 g of copper nitrate is then added and the mixture heated to boiling point and evaporated to dryness. The residue is heated in a stream of nitrogen at 280°C for 2 hours and 380°C for a further 2 hours.

Example 36

3 cm 3 of the catalyst prepared according to example 35

with a grain size of 50-150 micrometers is fed into an AISI 316 stainless steel reactor. A gas mixture with the following composition (in percentage by volume) is introduced through the upper end of the reactor: 0.8% acrolein, 1.2% methanol, 18.5% water vapour, 5.6% oxygen and the remainder mainly nitrogen. The process is carried out with the catalyst in a solid layer at 265°C and atmospheric pressure and a residence time of 2.2 s. Under these reaction conditions, the acrolein conversion is 80% and the selectivity for the formation of methyl acrylate 72% calculated on converted acrolein and 76% calculated on converted methanol.

Example 37

A number of experiments are carried out for the production of methyl methacrylate

from methacrolein, oxygen and methanol.

Different catalysts with the following composition are used in this reaction: A) A catalyst based on molybdenum, vanadium oxide, tungsten oxide and iron oxide with an atomic ratio between molybdenum and vanadium of 6:1, between molybdenum and tungsten of 6:1 and between molybdenum and iron of 3 ,4:1, B) a catalyst based on molybdenum oxide, vanadium oxide, tungsten oxide and copper oxide with an atomic ratio between molybdenum and vanadium of 1.8:1, between molybdenum and tungsten of 4.5:1 and between molybdenum and copper of 3: 1, C) a catalyst based on molybdenum oxide, vanadium oxide and tungsten oxide with an atomic ratio between molybdenum and vanadium of 4:1 and between molybdenum and tungsten of 12:1, while the catalyst also contains 30% by weight of silicon dioxide, D) a catalyst based on molybdenum oxide , tungsten oxide, vanadium oxide and copper oxide with an atomic ratio between molybdenum and tungsten of 1.8:1, between molybdenum and vanadium of 4.5:1 and between molybdenum and copper of 3:1.

The catalysts are prepared as described in the above-mentioned examples. The catalysts are fed together with a gaseous mixture of methacrolein, oxygen, water vapor and nitrogen at temperatures of 180-300°C and atmospheric pressure and a residence time of 1-10 s. A methacrolein conversion of 5-10% and a selectivity of 10-20 % for the formation of methyl methacrylate is achieved in all cases.

Example 38

A catalyst based on molybdenum oxide, vanadium oxide, tungsten oxide and iron oxide with an atomic ratio between molybdenum and iron of 3.4:1, between molybdenum and vanadium of 6:1 and between molybdenum and tungsten of

6:1 is prepared as described in the above examples.

3 cm 3 of this catalyst with a grain size of o 50-150 micrometers is fed into a stainless steel reactor with an

turning diameter of 8 mm.

A gas mixture with the following composition (in percent by volume) is introduced at the upper end of the reactor: 0.6% acrolein, 0.7% ethanol, 15.3% water vapor, 3.2% oxygen and the rest mainly nitrogen. The process is carried out with the catalyst in a solid layer at a temperature of 255°C and an overpressure of 200 mm Hg and a residence time of 2.5 s. Under these reaction conditions, the acrolein conversion is 20% and the selectivity for the formation of ethyl acrylate 15% based on converted acrolein.

Claims (2)

1. Process for the production of methyl or ethyl esters of acrylic or methacrylic acid by reacting gaseous acrolein or methacrolein, possibly in a mixture with propene or from a gas mixture produced by catalytic oxidation of propene, with oxygen and with gaseous methanol or ethanol in the presence of a catalyst, characterized in that the reaction is carried out in the presence of a catalyst of the general formula Mo V, Me 0 , Mo W,Me 0 or Mo V, W,Me 0 abc x adcy abdcz where Me denotes an iron, cobalt, nickel, copper, zinc, silver or cadmium atom, a has a value of 6-12, b has a value of 1-6, c has a value of 0-5, d has a value of 1-6, x has a value of 20.5-58.5, y has a value of 21-61.5 and z has a value of 23.5-76.5, at a temperature of 180-320°C and a pressure in the range from atmospheric pressure to 5 kp/cm 2 and with residence times of 0.1-40 s. 2. Method as stated in claim 1, characterized in that a catalyst is used which contains silicon dioxide as a carrier in an amount of up to approx. 99 parts by weight per 100 parts by weight of the catalyst.