(Meth)acrolein and / or (meth)acrylic acid production with reduced amounts of high-boiling by-products

Abstract

A reactor for producing (meth)acrolein and / or (meth)acrylic acid from reactants selected from propylene, isobutylene, and tert-butanol. The reactor includes an inlet for the reactants to enter the reactor, an outlet for the reaction products to exit the reactor, and a catalyst bed disposed between the inlet and the outlet. The catalyst bed includes a molybdenum and bismuth-based mixed oxide catalyst. The catalyst closest to the inlet of the reactor has a lower molar ratio of bismuth to molybdenum than the catalyst closest to the outlet of the reactor.

Description

[Technical Field]

[0001] The present invention relates to catalyst beds and processes for producing (meth)acrolein and / or (meth)acrylic acid. [Background technology]

[0002] (Meth)acrylic acid and its esters are important monomers for various polymers, including coatings, adhesives, and superabsorbent polymers. Most (meth)acrylic acid is produced by the two-stage oxidation of isobutylene, tert-butanol, or propylene, where the olefin or tert-butanol is first oxidized over a molybdenum (Mo) and bismuth (Bi)-based mixed oxide catalyst to form primarily (meth)acrolein, with (meth)acrylic acid being a minor product. (Meth)acrolein is then oxidized over a molybdenum and vanadium (V) and / or phosphorus (P)-based mixed oxide catalyst to produce (meth)acrylic acid. Major by-products of the acrylic acid production process from propylene include carbon monoxide, carbon dioxide, acetic acid, formaldehyde, acetaldehyde, propionic acid, propionaldehyde, acetone, allyl alcohol, maleic acid (or maleic anhydride), benzaldehyde, benzoic acid, furfural, and phthalic acid. In addition to these by-products, the methacrylic acid production process may form other by-products such as acrolein, acrylic acid, diacetyl, isobutyraldehyde, isobutyric acid, phthalic anhydride, and benzotricarboxylic acid. These by-products can be removed by distillation, extraction, melt crystallization, or a combination thereof. However, removing these by-products adds cost and complexity to the process.

[0003] U.S. Patent No. 9,440,904 discloses a process for producing acrolein and / or acrylic acid, or methacrolein and / or methacrylic acid, using two types of catalysts having different compositions stacked axially with higher productivity for (meth)acrolein. In the two types of catalysts, the amount of bismuth relative to molybdenum decreases from the gas inlet side to the gas outlet side of the reactor, and the amount of iron relative to molybdenum increases from the gas inlet side to the gas outlet side.

[0004] There is a need for catalyst beds and processes that can reduce the amount of by-products formed when (meth)acrolein and / or (meth)acrylic acid are produced from olefins or tert-butanol. Summary of the Invention

[0005] The present invention relates to a reactor and a process for preparing (meth)acrolein and / or (meth)acrylic acid from an olefin or tert-butanol, and further producing (meth)acrylic acid from (meth)acrolein.

[0006] According to one aspect of the present invention, a reactor for producing (meth)acrolein and / or (meth)acrylic acid includes an inlet for an olefin or tert-butanol to enter the reactor, an outlet for the reaction product to exit the reactor, and a catalyst bed disposed between the inlet and the outlet. The catalyst bed includes a molybdenum and bismuth-based mixed oxide catalyst. The catalyst closest to the reactor inlet has a lower bismuth-to-molybdenum molar ratio than the catalyst closest to the reactor outlet.

[0007] Another aspect of the present invention includes a process for preparing (meth)acrolein and / or (meth)acrylic acid from an olefin or tert-butanol, comprising oxidizing the olefin or tert-butanol in a reactor comprising an inlet for the olefin or tert-butanol to enter the reactor, an outlet for the reaction product to exit the reactor, and a catalyst bed disposed between the inlet and the outlet. The catalyst bed comprises a molybdenum and bismuth-based mixed oxide catalyst. The catalyst closest to the reactor inlet has a lower molar ratio of bismuth to molybdenum than the catalyst closest to the reactor outlet. DETAILED DESCRIPTION OF THE INVENTION

[0008] As used herein, the terms "a," "an," "the," "at least one," and "one or more" are used interchangeably. The terms "comprise," "include," "contain," and variations thereof, do not have a limiting meaning when these terms appear in the specification and claims. That is, for example, a mixture including a polymerization inhibitor can be interpreted to mean that the mixture includes at least one polymerization inhibitor.

[0009] As used herein, the term "(meth)acrolein" refers to both acrolein and methacrolein. Similarly, the term "(meth)acrylic acid" refers to both acrylic acid and methacrylic acid.

[0010] As used herein, the recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). For purposes of the present invention, it should be understood that numerical ranges are intended to include and support all possible subranges subsumed within that range, consistent with what one of ordinary skill in the art would understand. For example, a range of 1 to 100 is intended to convey 1.1 to 100, 1 to 99.99, 1.01 to 99.99, 40 to 6, 1 to 55, etc.

[0011] As used herein, recitations of numerical ranges and / or values, including such recitations in the claims, can be read as including the term "about." In such cases, the term "about" refers to a numerical range and / or value that is substantially the same as that recited herein.

[0012] Unless stated to the contrary or implicit from context, all parts and percentages are by weight and all test methods are as of the filing date of this application. For purposes of United States patent practice, the contents of any referenced patent, patent application, or patent application publication are incorporated by reference in their entirety (or the equivalent United States version thereof is so incorporated by reference), particularly with respect to the disclosure of definitions (to the extent not inconsistent with any definitions specifically provided in this disclosure) and general knowledge in the art.

[0013] One aspect of the present invention relates to a reactor for producing (meth)acrolein and / or (meth)acrylic acid from olefins or tert-butanol. Preferably, the olefins are selected from propylene and isobutylene.

[0014] The reactor includes an inlet for the olefin or tert-butanol to enter the reactor, an outlet for the reaction product to exit the reactor, and a catalyst bed disposed between the inlet and the outlet, the catalyst bed comprising a molybdenum and bismuth-based mixed oxide catalyst.

[0015] As used herein, the term "reaction product" includes the desired product, which includes (meth)acrolein and / or (meth)acrylic acid, as well as by-products of the reaction, which may include carbon monoxide, carbon dioxide, acetic acid, formaldehyde, acetaldehyde, propionic acid, propionaldehyde, acetone, allyl alcohol, maleic acid, maleic anhydride, benzaldehyde, benzoic acid, furfural, and phthalic acid, as well as methacrolein / methacrylic acid by-products, which include acrolein, acrylic acid, diacetyl, isobutyraldehyde, isobutyric acid, phthalic anhydride, and benzotricarboxylic acid.

[0016] Preferably, the molybdenum and bismuth based mixed oxide catalyst comprises a compound of formula I: Mo 12 Bi a X b Y c Z d O e Formula I During the ceremony, X is at least one element selected from the group consisting of iron, cobalt, and nickel; Y is at least one element selected from the group consisting of magnesium, calcium, strontium, barium, manganese, copper, zinc, cerium, boron, phosphorus, arsenic, tellurium, antimony, chromium, tungsten, sodium, potassium, rubidium, and cesium; Z is at least one element selected from the group consisting of silicon, aluminum, titanium, tin, and zirconium; a=0.1~2.0, b=1~12, c=0.01~3, d=0 to 20, e is based on the oxidation states of the other elements in the catalyst.

[0017] One objective of the present invention is to minimize the formation of by-products. Reaction by-products are typically removed by distillation, extraction, melt crystallization, or a combination thereof. By-products not only consume valuable reactant feed but also affect the recovery of (meth)acrylic acid and the need for by-product removal to prepare a particular grade of (meth)acrylic acid. For example, when crude acrylic acid is distilled to produce overhead acrylic acid with reduced amounts of maleic anhydride or maleic acid, some acrylic acid must be left in the bottoms along with most of the maleic anhydride or maleic acid. For flocculant-grade glacial acrylic acid, which limits the amount of furfural or benzaldehyde to less than 1 ppm, a chemical scavenger such as m-phenylenediamine may need to be added to the crude acrylic acid to form high-boiling adducts with the high-boiling aldehydes that are removed in an additional step.

[0018] Without being bound by theory, it is believed that the heavy by-products are related to the formation of the intermediate 1,5-hexadiene. 1,5-Hexadiene is formed as an intermediate by-product when propylene is deprotonated to form an allyl group, which can then react with another allyl group to form 1,5-hexadiene. This reaction competes with the main reaction of the allyl group to form acrolein.

[0019] [ka]

[0020] Furthermore, it is believed that the formation of allyl radicals from propylene is primarily catalyzed by bismuth in the molybdenum and bismuth-based mixed oxide catalyst, and the formation of acrolein from the allyl radicals is primarily catalyzed by molybdenum. Therefore, to increase the likelihood that allyl radicals will form acrolein, the molar ratio of bismuth to molybdenum is lower in the catalyst closest to the reactor inlet than in the catalyst closest to the reactor outlet. The molar ratio of bismuth to molybdenum may be increased from the reactor inlet to the reactor outlet to achieve a propylene conversion of 95% or greater when the propylene concentration is low near the reactor outlet. The ratios of other elements in the catalyst may also vary across the catalyst bed so that the activity of the catalyst closest to the reactor outlet is equal to or higher than that of the catalyst closest to the reactor inlet.

[0021] Similarly, the combination of radicals formed in the oxidation reaction of isobutylene or tert-butanol to form methacrolein also contributes to by-product formation, and furthermore, it is believed that having a lower molar ratio of bismuth to molybdenum in the catalyst closest to the inlet increases the likelihood that radicals formed from isobutylene or tert-butanol will react with the molybdenum to form methacrolein.

[0022] The molybdenum and bismuth-based mixed oxide catalyst of the catalyst bed may include a gradient composition of molybdenum and bismuth in the catalyst. In the gradient composition, the catalyst closest to the reactor inlet has a lower molar ratio of bismuth to molybdenum than the catalyst closest to the reactor outlet. The gradient composition may vary linearly between the reactor inlet and outlet, or may vary nonlinearly between the reactor inlet and outlet. For example, the molar ratio of bismuth to molybdenum may remain relatively constant near the reactor inlet and then increase rapidly toward the outlet.

[0023] Alternatively, the catalyst bed may contain two or more zones within the molybdenum and bismuth-based mixed oxide catalyst, each zone having a constant molar ratio of bismuth to molybdenum within the zone, the molar ratio of bismuth to molybdenum in the zone closest to the inlet being lower than the molar ratio of bismuth to molybdenum in the zone closest to the reactor outlet.

[0024] The catalyst bed may include three or more zones within the molybdenum and bismuth-based mixed oxide catalyst. When the catalyst bed includes three or more zones within the molybdenum and bismuth-based mixed oxide catalyst, the catalyst located in one or more zones between the zone closest to the reactor inlet and the zone closest to the reactor outlet may have a molar ratio of bismuth to molybdenum that is greater than the molar ratio of bismuth to molybdenum in the catalyst located in the zone closest to the inlet and less than the molar ratio of bismuth to molybdenum in the catalyst located in the zone closest to the reactor outlet.

[0025] Preferably, the catalyst bed comprises two or more zones within the molybdenum and bismuth based mixed oxide catalyst.

[0026] Preferably, the molar ratio of bismuth to molybdenum in the molybdenum and bismuth based mixed oxide catalyst is in the range of 0.2:12 to 1.6:12.

[0027] Preferably, the molar ratio of bismuth to molybdenum in the catalyst located nearest the reactor inlet is in the range of 0.2:12 to 1.0:12, and the molar ratio of bismuth to molybdenum in the catalyst located nearest the reactor outlet is in the range of 0.6:12 to 1.6:12. More preferably, the molar ratio of bismuth to molybdenum in the catalyst located nearest the reactor inlet is in the range of 0.3:12 to 0.8:12, and the molar ratio of bismuth to molybdenum in the catalyst located nearest the reactor outlet is in the range of 0.8:12 to 1.4:12.

[0028] Another aspect of the present invention relates to a process for preparing (meth)acrolein from a reactant selected from an olefin (e.g., propylene or isobutylene) or tert-butanol, comprising oxidizing the reactants in a reactor comprising an inlet for introducing the reactants into the reactor, an outlet for the reaction products to exit the reactor, and a catalyst bed disposed between the reactor inlet and outlet. The catalyst bed comprises a molybdenum and bismuth-based mixed oxide catalyst as described above, wherein the catalyst located closest to the reactor inlet has a lower bismuth-to-molybdenum molar ratio than the catalyst located closest to the reactor outlet. The process is conducted in the vapor phase in the presence of oxygen.

[0029] In a second step, (meth)acrolein in the reaction product may be selectively oxidized over a second mixed metal oxide catalyst in the presence of oxygen in the gas phase, the second mixed metal oxide catalyst having a different composition than the molybdenum and bismuth-based mixed oxide catalyst.

[0030] The second mixed metal oxide catalyst may be, for example, a solid catalyst containing oxides of molybdenum (Mo) and vanadium (V) and / or phosphorus (P). The second mixed metal oxide catalyst may also contain at least one additional element selected from tungsten (W), copper (Cu), iron (Fe), and antimony (Sb). When the second mixed metal oxide catalyst contains at least one additional element, molybdenum and vanadium are the major metal elements present. Preferably, the second mixed metal oxide catalyst contains at least 40 wt. % molybdenum and vanadium, for example, at least 50 wt. %, at least 60 wt. %, or at least 70 wt. % molybdenum and vanadium, based on the total weight of non-oxygen elements in the second mixed metal oxide catalyst.

[0031] The second mixed metal oxide catalyst can be any commercially available mixed metal oxide catalyst used in the oxidation of (meth)acrolein to (meth)acrylic acid.

[0032] In the selective oxidation reaction to form (meth)acrolein and / or (meth)acrylic acid, oxygen can be present in the form of purified oxygen, oxygen in air, or lattice oxygen of a mixed metal oxide catalyst. Preferably, the oxygen is from air or from the lattice oxygen of a mixed metal oxide catalyst.

[0033] Purification of the (meth)acrolein and / or (meth)acrylic acid can be achieved by one or more techniques known in the art, such as, for example, absorption with water or organic solvents, extraction, fractional distillation, or melt crystallization.

[0034] Desktop example The following prophetic examples illustrate the present invention but are not intended to limit the scope of the invention.

[0035] In a tubular reactor, a catalyst bed is positioned between the reactor inlet and the reactor outlet. The catalyst bed is composed of a molybdenum and bismuth-based mixed oxide catalyst that includes two zones. The composition of the molybdenum and bismuth-based mixed oxide catalyst is the same in both zones, except for the amount of bismuth. In the first zone, closest to the reactor inlet, the molar ratio of bismuth to molybdenum is 0.6:12, and in the second zone, closest to the reactor outlet, the molar ratio of bismuth to molybdenum is 1.2:12.

[0036] A reactant gas stream containing 8.1% by volume of propylene and 14.4% by volume of oxygen is introduced into the inlet of the reactor.

[0037] The amount of maleic anhydride is expected to be significantly reduced, eg, by as much as 50%, compared to commercially available catalysts for the oxidation of propylene to form acrolein.

Claims

1. 1. A reactor for producing (meth)acrolein and / or (meth)acrylic acid from reactants selected from propylene, isobutylene, and tert-butanol, the reactor comprising: an inlet for the reactants to enter the reactor; an outlet for reaction products to exit the reactor; and a catalyst bed disposed between the inlet and the outlet, the catalyst bed comprising a molybdenum and bismuth-based mixed oxide catalyst, the catalyst closest to the inlet of the reactor having a lower molar ratio of bismuth to molybdenum than the catalyst closest to the outlet of the reactor.

2. 10. The reactor of claim 1, wherein the catalyst bed comprises a gradient composition of molybdenum and bismuth in the catalyst, the molar ratio of bismuth to molybdenum increasing from the catalyst closest to the inlet of the reactor to the catalyst closest to the outlet of the reactor.

3. 10. The reactor of claim 1, wherein the catalyst bed comprises two or more zones within the catalyst, the catalyst having a different composition within each zone, the catalyst located in the zone closest to the inlet of the reactor having a lower molar ratio of bismuth to molybdenum than the catalyst located in the zone closest to the outlet of the reactor.

4. 4. The reactor of claim 3, wherein the catalyst bed comprises three or more zones within the catalyst, and the catalyst located in one or more zones between the zone closest to the inlet of the reactor and the zone closest to the outlet of the reactor has a molar ratio of bismuth to molybdenum that is greater than the molar ratio of bismuth to molybdenum in the catalyst located in the zone closest to the inlet and less than the molar ratio of bismuth to molybdenum in the catalyst located in the zone closest to the outlet.

5. The molybdenum and bismuth-based mixed oxide catalyst comprises a compound of formula I: Mo １２ Bi ａ X ｂ Y ｃ Z ｄ O ｅ Formula I During the ceremony, X is at least one element selected from the group consisting of iron, cobalt, and nickel; Y is at least one element selected from the group consisting of magnesium, calcium, strontium, barium, manganese, copper, zinc, cerium, boron, phosphorus, arsenic, tellurium, antimony, chromium, tungsten, sodium, potassium, rubidium, and cesium; Z is at least one element selected from the group consisting of silicon, aluminum, titanium, tin, and zirconium; a=0.1~2.0, b=1 to 12, c=0.01 to 3, d=0 to 20; 5. The reactor of claim 1, wherein e is based on the oxidation states of other elements in the catalyst.

6. A reactor according to any one of claims 1 to 5, wherein the molar ratio of bismuth to molybdenum in the catalyst bed is in the range of from 0.2:12 to 1.6:

12.

7. 7. The reactor of any one of claims 1 to 6, wherein the molar ratio of bismuth to molybdenum in the catalyst located nearest the inlet of the reactor is in the range of 0.2:12 to 1.0:12 and the molar ratio of bismuth to molybdenum in the catalyst located nearest the outlet of the reactor is in the range of 0.6:12 to 1.6:

12.

8. 8. The reactor of claim 7, wherein the molar ratio of bismuth to molybdenum in the catalyst located nearest the inlet of the reactor ranges from 0.3:12 to 0.8:12 and the molar ratio of bismuth to molybdenum in the catalyst located nearest the outlet of the reactor ranges from 0.8:12 to 1.4:

12.

9. 1. A method comprising:

9. A process comprising oxidizing a reactant selected from propylene, isobutylene, and tert-butanol in a reactor according to any one of claims 1 to 8, wherein the reaction product exiting the reactor comprises (meth)acrolein.

10. 10. The method of claim 9, wherein the reactant is propylene and the reaction product comprises acrolein.

11. 11. The method of claim 10, further comprising oxidizing the acrolein to produce acrylic acid.

12. 10. The method of claim 9, wherein the reactants are selected from isobutylene and tert-butanol, and the reaction product comprises methacrolein.

13. 13. The method of claim 12 further comprising activating said methacrolein to produce acrylic acid.

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