DE2139975A1 - METHOD FOR PRODUCING ACRYLIC ACID - Google Patents

Description

knapsackaktiengesellschaft 2139975

Process for the production of acrylic acid

The invention relates to a V _e rfahren for producing acrylic acid by reacting propylene and / or acrolein with air and / or oxygen and water vapor at elevated temperatures in the presence of a supported catalyst comprising iron, bismuth, phosphorus, potassium, molybdenum, as well as Nikkei and / or Contains cobalt in oxidic form.

Such a catalyst system is already known from German Offenlegungsschriften 2,020,791 and 2,038,749. To produce the catalysts, aqueous solutions of the individual compounds, e.g. phosphoric acid, ammonium molybdate, are used there and metal nitrates, mixed, resulting in a slurry of sparingly soluble molybdates, in which Silica sol is stirred in. The catalyst mass is then dried and heated, cooled, pulverized, processed into pellets and calcined. With the catalyst prepared in this way, acrylic acid can be used in a fixed bed - in addition to acrolein as the main product - in a maximum yield of 10%, calculated on the propylene used be, it is particularly emphasized in the laid-open specifications that the process for selective oxidation from propylene to acrolein because the oxidation of propylene to acrylic acid is largely suppressed.

In the same way, according to the German Auslegeschrift 1 667 209 a similar, but potassium-free catalyst can be produced, with the help of which, according to the German Patent specification 1,268,609 starting from propylene and oxygen in addition to small amounts of acrolein at best up to

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to 46 % acrylic acid, calculated on the used and completely converted propylene can be obtained.

Surprisingly, it has now been found that even with the supported catalyst described above, which iron, Contains bismuth, phosphorus, potassium, molybdenum and nickel and / or cobalt in oxidic form, mainly according to the invention and with good conversions, yields and catalyst performances acrylic acid through one-stage oxidation of propylene and / or acrolein with oxygen in the gas phase in a single pass in the fluidized bed, so without the mostly with a method of working in a fixed bed, which is technically very complex and correspondingly costly, the recirculation unconverted starting materials, by-products and inert gases, can be obtained if the catalyst is on a previously manufactures not yet described manner.

In particular, the invention relates to a process for the production of acrylic acid by reacting propylene and / or acrolein with air and / or oxygen and water vapor at elevated temperatures in the presence of a supported catalyst, which iron, bismuth, phosphorus, potassium, molybdenum and nickel and / or Contains cobalt in oxidic form, which is characterized in that the reaction is carried out at temperatures between 300 and 450 ° C in a fluidized or fluidized bed in the presence of a support catalyst which contains the active elements in an atomic ratio of ^Ni o-12 ^Co O-12 ^Fe 0 , 5-10 ^Bi 0.5-10 ^P 0 _r 1-6 ^K 0.001-2 ^Mo 12 ° 37-118 ^contains ^^ ^where * ^e i the indices for Ni and Co are not equal to zero at the same time, and has been produced in this way that an aqueous solution of ammonium heptamolybdate and phosphoric acid was applied in one or more impregnations to a solid carrier with a grain size of 0.02 to 0.5 mm in a first stage, such a volume of solution being used which is about 1 to 2 times the previously determined pore size

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Corresponding to the volume of the carrier substance, and after each impregnation it was dried for 3 to 10 hours at 100 to 300 ° C .; ttnd that in a second stage an aqueous-nitric acid solution of the nitrates of iron, bismuth, potassium and nickel and / or cobalt was applied in one or more impregnations to this partially covered carrier material, with such a volume of solution being used that approximately the ⁰ C was 1 to 2 times the previously determined pore volume of the already partially occupied excipient corresponded to each impregnation 2 to 12 hours at 70 to 95 ⁰ C held, then for 3 to 10 hours at up to 30O dried and finally by 0.5 to 10-hour sintering of the supported catalyst at 400 to 700 ⁰ C, a BET surface area of the catalyst of 5 to 100 m / g was set; and that an oxygen concentration of less than 2% by volume is maintained in the exhaust gas of the condensed reaction products.

In addition, the method of the invention can optionally be characterized in that

a) in the production of the supported catalyst, the order of the impregnations was reversed and the solution of the nitrates of iron, bismuth, potassium and nickel and / or cobalt was applied to the solid carrier as the first stage and ^{dried at 100 to 300 °} C., and as second stage, the solution of ammonium heptamolybdate and phosphoric acid applied, maintained for 2 to 12 hours at 70 to 95 ⁰ C, to 30O C was getrocknei and finally sintered at 100 ^0;

b) in the preparation of the supported catalyst, the partially coated one, which is dried ^{at 100 to 300 ° C.}

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^{The carrier material of the first stage was sintered at 400 to 700 °} C. for 0.5 to 10 hours before being used in the second stage;

c) in the production of the supported catalyst, the carrier material is silica, aluminum oxide, Aluminum silicate, pumice stone, silicon carbide or asbestos was used.

The carrier material used is preferably present in an average particle size of 0.02 to 0.3 mm in diameter. The volume ratio of the starting gases, i.e. from propylene or acrolein to air to nitrogen to steam, can preferably be 1 to (3 to 20) to (0 to 5) to (2 to 8) range. The apparent residence time, i.e. based on the quiescent catalyst volume of the starting gases under reaction conditions is preferably between 2 and 15 seconds. The pressure is preferably between 1 and 5 ata. The composition of the source gases and the operating conditions are preferred adjusted so that the oxygen content of the exhaust gas after the condensation of the reaction gases is less than 2 volumes ^ amounts to. With the process according to the invention become essential higher yields of acrylic acid, based on the propylene or acrolein used, are obtained than after the above outlined method according to the prior art.

The supported catalysts prepared according to the invention are particularly notable for their mechanical resistance and a high abrasion resistance required for technical use in fluidized beds.

The solution volumes applied to the solid support are to be dimensioned so that the maximum liquid absorption capacity of the carrier material is not exceeded. In the pra-

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In this case, it is expedient to first determine the liquid absorption capacity of the carrier substance, which may already be partially covered, on a small sample of water. To do this, you knead into a certain amount of the dry, solid. Carrier just enough water until it appears evenly moistened, but its flowability is fully retained. ¹ If a high coverage of the carrier with active material is desired, the dissolved substances must gradually be applied several times to the carrier, with the mentioned 3 to 10-hour drying at 100 to 300 ⁰ C and between each impregnation in the first stage In the second stage, the aforementioned heat treatment at 70 to 95 ^° C. also has to be inserted. If the limit set by the liquid absorption capacity of the support is exceeded, i.e. if more than twice the determined pore volume of the support is used in solution volume, the mechanical stability of the supported catalysts decreases, which results in their reduced abrasion resistance and as a result expresses itself in a rapid drop in performance.

The supported catalyst is sintered to a BET surface area of 5 to 100 m / g, preferably 20 to 60 m / g, set. During drying and sintering, the catalyst mass should preferably be kept in constant motion in order to stick the catalyst particles together prevent. The supported catalysts prepared according to the invention can be, for example, 15 to 85% by weight, preferably 30 to 70 weight ^, contain carrier,

By carefully observing the maximum liquid absorption as well as the heat treatment, drying and sintering conditions the active ingredients are so firmly anchored in and on the porous support that abrasion

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during the test period of several months did not lead to a reduction in activity and no significant one Increase in fines can be seen in the grain spectrum,

example 1

a) Determination of fluid intake

100 g of a fresh, dried silica carrier (density: 0.4 g / cm; mean grain size: 0.02 to 0.11 mm; BET surface area 413 m / g) were kneaded in by Water brought to the optimal degree of humidity. This required 125 ml of water, i.e. the impregnation of 100 g of catalyst support can be done with 125 ml of a salt solution of varying concentration For the reasons already mentioned, the application should under no circumstances be twice this volume be crossed, be exceeded, be passed.

b) Production of a supported catalyst with a content of the active components in the atomic ratio Nig qCo-zFep ^

^M ^ ^and ^ ¹ % by weight silica as

q i812 ^ 50 5
carrier

The solution of 1200 g ammonium heptamolybdate / ^ g ^Mo 7 ^ 24 * ^ ^ 2 ° - ' ^{and 10} ° ^{g 8} ^ weight% phosphoric acid in 1100 g water was applied to 1400 g silica carrier of the quality tested under a). After 8 hours of drying at 200 ^° C., the solution of 10 g of potassium nitrate, 280 g of bismuth nitrate, 480 g of iron (III) nitrate, 500 g of cobalt nitrate and 150 g of nickel nitrate in a mixture of 550 ml of water and 60 ml of 69% by weight was carried iger nitric acid on the carrier, which is already coated with oxides of molybdenum and phosphorus. The indicated

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moistened mass was kept for 10 hours at 90 ⁰ C, then dried for 8 hours at 200 ⁰ C and finally sintered for 6 hours at 470 ⁰ C. The final catalyst had a BET surface area of 54 m / g.

1 liter of this catalyst was placed in a fluidized bed apparatus 100 cm in height and 50 mm in diameter. A gas mixture, preheated to 130 ^° C., of propylene, air and water vapor in a volume ratio of 1: 8.5: 3.5 at atmospheric pressure and 340 ^° C. was passed through the catalyst, the apparent residence time of the gas mixture based on the quiescent catalyst volume 4.6 see set. The acrylic acid formed and the acetic acid were obtained as an aqueous solution (condensate) with about 35% by weight of acrylic acid by appropriate cooling of the reaction gases or by washing out the reaction gases with the condensate that had already been obtained. The quantitative composition of the condensate and the exhaust gas were determined by gas chromatographic analysis. The oxygen content of the exhaust gas was 1.7 volume ^. The yields based on the propylene used were 65.3 % for acrylic acid, 6.2 % for acetic acid and 4.9 % for acrolein. The propylene conversion was 90.2%. The proportion of combustion (CO, CO ₂ ) was 13 %. The catalyst output was 56 g of acrylic acid per liter of catalyst per hour.

Example 2

Production of a supported catalyst with a content of the active components in the atomic ratio Ni ^ Bi ₁ P ₂ K ₀ 1Mo ₁₂ O _{52 2} and 50% by weight of silica as a support

To a solution of 1059 g of ammonium heptamolybdate in

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115 g of 85% phosphoric acid were added to 1000 ml of water. 1300 g of silica carrier of the quality defined in Example 1 were impregnated with the yellow solution obtained. After 8 hours of drying at 200 ^° C., the solution of 5.05 g of potassium nitrate, 242.5 g of bismuth nitrate, 404 g of iron nitrate, 145.5 g of cobalt nitrate and 509 g of nickel nitrate in 530 ml of 8% nitric acid was applied to the already partially occupied carrier. The wetted catalyst mass was thought to 5 hours at 80 ⁰ C, then dried for 8 hours at 200 ⁰ C and finally sintered for 6 hours at 500 ⁰ C. The final catalyst had a BET surface area of 25 m / g.

1 liter of this catalyst was placed in a fluidized bed apparatus 100 cm high and 50 mm in diameter. Was passed a gas mixture comprising acrolein, air, nitrogen and water vapor in a volume ratio of 1: 3: 3 4.5 at 33O ⁰ C and atmospheric pressure by the catalyst to give see ceased apparent residence time of the gas mixture to the fourth The condensation of the reaction gases and the recovery of the crude acrylic acid took place as in Example 1. The oxygen content of the exhaust gas was 1.8% by volume. The acrolein conversion was 92.1 %. The yields based on the acrolein used were 81.7 % for acrylic acid and 8% for acetic acid. The catalyst output was 85 g of acrylic acid per liter of catalyst per hour.

Example 3

Production of a ?, supported catalyst with a content of the active components in the atomic ratio COgFeABi ₁ P ₂ ·} Μθΐ2 ° 57 5 ^and ^ ^{0 ΟΘν1οη} * ⁸ ^ silica as a carrier

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57 g of 85% strength phosphoric acid were added to a solution of 530 g of ammonium heptamolybdate in 570 ml of water. 730 g of silica carrier of the quality defined in Example 1 were impregnated with the yellow solution obtained. After 10 hours of drying at 2OQ ⁰ C. carried the solution of 2.5 g of potassium nitrate, 404 g of iron nitrate, 436 g of cobalt nitrate and .121 g of bismuth nitrate in 26Ο ml water to which 30 ml of 69% nitric acid were added to the already partially occupied carrier. The crude catalyst mass was held for 6 hours at 80 ⁰ C, dried and subsequently sintered for 4 hours at 600 ⁰ C for 10 hours at 220 ⁰ C. The finished catalyst

Sator had a BET surface area of 36 m / g.

1 liter of this catalyst was placed in a fluidized bed apparatus 100 cm high and 50 mm in diameter. Was passed a gas mixture of propylene, air and steam in a volume ratio of 1: 9.35: 3.5 at 36O ⁰ C and atmospheric pressure through the catalyst so that an apparent residence time of 5> 0 complied see '. After condensation, the crude acrylic acid was obtained as an approximately 33% strength by weight solution. The oxygen content of the exhaust gas was 1.7 volume ^. The propylene conversion was 91.4 %. The yields based on the propylene used were 60.8 % for acrylic acid, 6.0 % for acetic acid and 5.3 % for acrolein. The catalyst output was 45 g of acrylic acid / liter of catalyst per hour.

Example 4

Production of a catalyst with a content of the active components in the atomic ratio NIgFe ^ BL ₁ PpK ₀ -1Mo ₁ - O ^ rj κ and 50 weight ^ silica as a carrier.

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The same method was used as in the example 3 using 436 g of nickel nitrate instead of cobalt nitrate. The finished catalyst had a BEI surface of 55 m / g.

1 liter of this catalyst was filled in the well-known fluidized bed apparatus "was passed a gas mixture of propylene, air and steam in a volume ratio of 1: 9.1: 3.5 at 35O ⁰ C and atmospheric pressure with the apparent residence time of 4.8 see through the catalyst During the condensation, a 33% strength by weight crude acrylic acid was obtained. The oxygen content in the exhaust gas was 1.4% by volume. The propylene conversion. was 92.4%. The yields based on the propylene used were 61.3 % for acrylic acid, 6.4 % for acetic acid and 6.8 % for acrolein. The catalyst output was 48.5 g of acrylic acid / liter of catalyst per hour.

Example 5

Production of a supported catalyst with a content of the active components in the atomic ratio Ni, -Co ^ Fe ₂ Bi ₁ PpK ₀ 2 ^Mo 12 ^0t 32 5 " ^nd ^ ⁰ % by weight of silica as a support.

801 g of silica carrier was impregnated with a solution of 6.1 g of potassium nitrate, 245 g of iron nitrate, 88 g of cobalt nitrate, 308 g of nickel nitrate and 147 g of bismuth nitrate in 350 ml of water and 40 ml of 69% nitric acid. After drying for 8 hours at 200 ^° C., a solution of 642 g of ammonium heptamolybdate and 70 g of 85% phosphoric acid in 500 ml of water was applied to this support. After 3 hours of treatment at 85 ° C for 8 hours at 220 ° C was dried and then sintered 5 hours at 55O ⁰ C.

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The finished catalyst had a BET surface area of 45 m ² / g.

1 liter of this catalyst was placed in the known fluidized bed apparatus. A gas mixture of propylene, air and steam in a volume ratio of 1: 9: 3.5 'at 350 ° C. and atmospheric pressure was passed through this catalyst while maintaining the apparent residence time of 4.5 seconds. The crude acrylic acid was obtained as an approximately 35 weight solution. The oxygen content of the exhaust gas was 1.6 volume ^. At a propylene conversion of 92.1 % , the yields based on propylene used were 64.3% for acrylic acid, 6.4 % for acetic acid and 4.9% for acrolein. The catalyst output was 54.5 g acrylic acid / liter of catalyst per hour .

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Claims (1)

• Patent claims: / i) l / learn about the production of acrylic acid by reacting ^ - • 'of propylene and / or acrolein with air and / or oxygen and water vapor at elevated temperatures in the presence of a supported catalyst, which iron, bismuth, phosphorus, potassium, molybdenum and nickel and / or contains cobalt 'in oxidic form, characterized in that the reaction is carried out at temperatures between 300 and 450 ⁰ C in a fluidized or fluidized bed in the presence of a supported catalyst which contains the active elements in the atomic ratio ^ ο-ΛΖ ^ Ο- ^ 0.5 ^ 0 ^ 0, ^ d ⁹ O ^ -6 Kq 001 -? ^ ° 12 ^^ 7-118 ^en "k ⁿ eld, whereby the indices for Ni and Co are not equal to zero at the same time, and have been produced in this way is that on a solid carrier of the grain size 0.02 to 0.5 mm in a first stage an aqueous solution of ammonium heptamolybdate and phosphoric acid was applied in one or more impregnations, such a volume of solution was used, which was about the 1 to 2 times that previously determined telten pore volume of the support material corresponded to, and after each impregnation 3 to 10 hours at 100 to 300 ⁰ C was dried; and that in a second stage an aqueous-nitric acid solution of the nitrates of iron, bismuth, potassium and nickel and / or cobalt was applied in one or more impregnations to this partially covered carrier, with such a volume of solution being used that approximately the - 1 to 2 times the previously determined pore volume of the already partially covered carrier, was kept at 70 to 95 ° C for 2 to 12 hours after each impregnation, then ^{dried for 3 to 10 hours at 100 to 300 0} C and finally by 0, Sintering the supported catalyst at 400 to 700 ^° C. for 5 to 10 hours -13-30980Ö / 1279 BET surface area of the catalyst of 5 to 100 m / g was set "and that one condensed in the exhaust gas
Reaction products an oxygen concentration of less than 2 Vol-? Ö complies with " '2) Method according to claim 1, characterized ₃ that in the production of the supported catalyst the order = sequence of the impregnations reversed and "on the solid support = material as the first stage the solution of the rate of iron, bismuth, potassium and nickel and / or cobalt was applied and ^{dried at 100 to 300 0} C, and as a second stage the solution of ammonium heptamolybdate and phosphoric acid was applied, held at 70 to 95 ⁰ C for 2 to 12 hours, at 100 to
was finally sintered, 95 ⁰ C held, dried at 100 to 300 ⁰ C and off 3) Method according to claim 1 or 2, characterized in that in the preparation of the supported catalyst
the dried at 100 to 300 ⁰ C, partially covered
Carrier of the first stage before use in the
zxveite stage 0.5 to 10 hours at 400 to 700 ⁰ C.
was sintered. 4) Method according to one of claims 1 to 3, characterized in that in the production of the supported catalyst as a carrier silica, aluminum oxide, AIu = miniumsilicate, pumice stone, silicon carbide or asbestos
was used" 309808/1279
BATH ORIGINAL