Production of (meth) acrolein and / or (meth) acrylic acid with reduced amounts of high-boiling byproducts

Abstract

A reactor for producing (meth) acrolein and / or (meth) acrylic acid from reactants selected from the group consisting of propylene, isobutylene and tertiary butanol. The reactor includes an inlet for the reactant 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 mixed oxide catalyst based on molybdenum and bismuth. The catalyst closest to the inlet of the reactor has a molar ratio of bismuth to molybdenum lower than the catalyst closest to the outlet of the reactor has a molar ratio of bismuth to molybdenum.

Description

Technical Field

[0001] The present invention relates to a catalyst bed and a process for producing (meth)acrolein and / or (meth)acrylic acid. Background Art

[0002] (Meth) acrylic acid and its ester are important monomers for various polymers (including coatings, adhesives and superabsorbent polymers). Most of (meth) acrylic acid in (meth) acrylic acid is produced via two-stage oxidation of isobutylene, the tert-butyl alcohol or propylene, wherein olefin or the tert-butyl alcohol are first oxidized on a mixed oxide catalyst based on molybdenum (Mo) and bismuth (Bi) to mainly form (meth) acrolein, and (meth) acrylic acid is a minor product. Then (meth) acrolein is oxidized on a mixed oxide catalyst based on molybdenum and vanadium (V) and / or phosphorus (P) to produce (meth) acrylic acid. The main by-products of the method for producing acrylic acid by propylene include carbon monoxide, carbon dioxide, acetic acid, formaldehyde, acetaldehyde, propionic acid, propionic aldehyde, acetone, allyl alcohol, maleic acid (or maleic anhydride), benzaldehyde, benzoic acid, furfural and phthalic acid. Except these by-products, the methacrylic acid production method can form other by-products, such as acrolein, acrylic acid, diacetyl, isobutyraldehyde, isobutyric acid, phthalic anhydride and benzotricarboxylic acids. These by-products can be removed via distillation, extraction, melt crystallization, or a combination thereof. However, removing these by-products increases the cost and complexity of the process.

[0003] U.S. Patent No. 9,440,904 discloses a method for producing acrolein and / or acrylic acid, or methacrolein and / or methacrylic acid using two catalysts having different formulations stacked in an axial direction, wherein the productivity of (meth)acrolein is higher. In both catalysts, the component amount of bismuth relative to molybdenum decreases from the gas inlet side to the gas outlet side of the reactor, while the component 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 are able to reduce the amount of by-products formed in the production of (meth)acrolein and / or (meth)acrylic acid from olefins or tert-butyl alcohol. Summary of the invention

[0005] The present invention relates to a reactor and a method for preparing (meth)acrolein and / or (meth)acrylic acid from olefins or tert-butyl alcohol, and to producing (meth)acrylic acid from (meth)acrolein.

[0006] According to one aspect of the invention, a reactor for producing (meth) acrolein and / or (meth) acrylic acid comprises an inlet for olefins or tert-butyl alcohol to enter the reactor, an outlet for reaction products to leave the reactor, and a catalyst bed disposed between the inlet and the outlet. The catalyst bed comprises a mixed oxide catalyst based on molybdenum and bismuth. The catalyst closest to the inlet of the reactor has a molar ratio of bismuth to molybdenum that is lower than the molar ratio of bismuth to molybdenum that the catalyst closest to the outlet of the reactor has.

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

[0008] As used herein, the terms "one", "the", "at least one", and "one or more" are used interchangeably. The terms "comprising", "including", "containing" and variations thereof do not have a limiting meaning when these terms appear in the specification and claims. Thus, for example, a mixture comprising a polymerization inhibitor can be interpreted as the mixture comprising 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, reciting 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 is understood that numerical ranges are intended to include and support all possible subranges included within that range, consistent with what is understood by one of ordinary skill in the art. For example, a range of 1 to 100 is intended to express 1.1 to 100, 1 to 99.99, 1.01 to 99.99, 40 to 6, 1 to 55, etc.

[0011] As used herein, the recitation of numerical ranges and / or values, including such recitations in the claims, may be read to include the term "about." In such cases, the term "about" refers to numerical ranges and / or values ​​that are substantially the same as those recited herein.

[0012] Unless stated to the contrary, or implicit from the context, all parts and percentages are based on weight and all test methods are current as of the filing date of this application. For purposes of U.S. patent practice, the contents of any cited patent, patent application, or publication are incorporated by reference in their entirety or their equivalent U.S. versions are so incorporated by reference), particularly with respect to 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-butyl alcohol. Preferably, the olefin is selected from propylene and isobutylene.

[0014] The reactor comprises an inlet for olefin or tert-butyl alcohol to enter the reactor, an outlet for the reaction product to leave the reactor and a catalyst bed disposed between the inlet and the outlet. The catalyst bed comprises a mixed oxide catalyst based on molybdenum and bismuth.

[0015] As used herein, the term "reaction product" includes the desired product, including (meth)acrolein and / or (meth)acrylic acid, and by-products of the reaction, which by-products 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 including acrolein, acrylic acid, diacetyl, isobutyraldehyde, isobutyric acid, phthalic anhydride and benzotricarboxylic acids.

[0016] Preferably, the mixed oxide catalyst based on molybdenum and bismuth comprises a compound of formula I:

[0017] Mo 12 Bi a X b Y c Z d O e Formula I

[0018] in:

[0019] X is at least one element selected from the group consisting of iron, cobalt and nickel;

[0020] 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;

[0021] Z is at least one element selected from the group consisting of silicon, aluminum, titanium, tin and zirconium;

[0022] a=0.1 to 2.0;

[0023] b = 1 to 12;

[0024] c = 0.01 to 3;

[0025] d = 0 to 20; and

[0026] e is based on the oxidation states of the other elements in the catalyst.

[0027] One object of the present invention is to minimize the formation of by-products. The by-products of the reaction are usually removed via distillation, extraction, melt crystallization or a combination thereof. The by-products not only consume valuable reactant feeds, but also affect the recovery of (meth) acrylic acid and the need to remove by-products to prepare certain grades of (meth) acrylic acid. For example, during the distillation of crude acrylic acid to prepare overhead acrylic acid with a reduced amount of maleic anhydride or maleic acid, some acrylic acid must be left at the bottom of the tower with most of the maleic anhydride or maleic acid. For flocculant-grade glacial acrylic acid that limits the amount of furfural or benzaldehyde to less than 1 ppm, it may be necessary to add a chemical scavenger such as m-phenylenediamine to the crude acrylic acid to form a higher boiling adduct with the high boiling aldehyde removed in the additional step.

[0028] Without being bound by theory, it is believed that the heavy byproducts are associated with the formation of the intermediate 1,5-hexadiene. 1,5-hexadiene is formed as an intermediate byproduct when propylene is deprotonated to form an allyl radical, which can then react with another allyl radical to form 1,5-hexadiene. This reaction competes with the main reaction of the allyl radical to form acrolein.

[0029]

[0030] It is further believed that the formation of allyl radicals from propylene is primarily catalyzed by bismuth in a molybdenum and bismuth-based mixed oxide catalyst, and that the formation of acrolein from allyl radicals is primarily catalyzed by molybdenum. Therefore, in order to increase the likelihood of acrolein formation from allyl radicals, the molar ratio of bismuth to molybdenum in the catalyst closest to the reactor inlet is made lower than the molar ratio of bismuth to molybdenum in the catalyst closest to the reactor outlet. When the propylene concentration near the reactor outlet becomes lower, the molar ratio of bismuth to molybdenum can be increased from the inlet to the outlet of the reactor to drive the propylene conversion to 95% or more. In the catalyst, the proportions of other elements can also be different throughout the catalyst bed so that the activity of the catalyst closest to the reactor outlet is equal to or higher than the activity of the catalyst closest to the reactor inlet.

[0031] Similarly, it is believed that a combination of free radicals formed in the oxidation reaction of isobutylene or tert-butyl alcohol to form methacrolein is also responsible for by-product formation, and further, having a lower molar ratio of bismuth to molybdenum in the catalyst closest to the inlet will increase the likelihood that free radicals formed from isobutylene or tert-butyl alcohol will react with molybdenum to form methacrolein.

[0032] The mixed oxide catalyst based on molybdenum and bismuth of the catalyst bed can comprise the gradient composition of molybdenum and bismuth in the catalyst. In the gradient composition, the molar ratio of bismuth to molybdenum of the catalyst closest to the reactor inlet is lower than the molar ratio of bismuth to molybdenum of the catalyst closest to the reactor outlet. The gradient composition can change linearly between the inlet and outlet of the reactor or can change nonlinearly between the inlet and outlet of the reactor. For example, the molar ratio of bismuth to molybdenum can remain relatively constant near the inlet close to the reactor, and then increase rapidly towards the outlet.

[0033] Alternatively, the catalyst bed may comprise two or more zones within the mixed oxide catalyst based on molybdenum and bismuth, wherein each zone has 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 may be lower than the molar ratio of bismuth to molybdenum in the zone closest to the outlet of the reactor.

[0034] The catalyst bed may include three or more zones within the mixed oxide catalyst based on molybdenum and bismuth. When the catalyst bed includes three or more zones within the mixed oxide catalyst based on molybdenum and bismuth, the catalyst 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 in the zone closest to the inlet and less than the molar ratio of bismuth to molybdenum in the catalyst in the zone closest to the reactor outlet.

[0035] Preferably, the catalyst bed comprises two or more zones within the mixed oxide catalyst based on molybdenum and bismuth.

[0036] Preferably, the molar ratio of bismuth to molybdenum in the mixed oxide catalyst based on molybdenum and bismuth is in the range of 0.2:12 to 1.6:12.

[0037] Preferably, the molar ratio of bismuth to molybdenum in the catalyst located closest to 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 closest to 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 closest to 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 closest to the reactor outlet is in the range of 0.8:12 to 1.4:12.

[0038] Another aspect of the invention relates to a method for preparing (meth) acrolein from a reactant selected from an olefin (e.g., propylene or isobutylene) or tert-butyl alcohol, the method comprising oxidizing the reactant in a reactor comprising an inlet for introducing the reactant into the reactor, an outlet for the reaction product to leave the reactor, and a catalyst bed disposed between the inlet and the outlet of the reactor. The catalyst bed comprises a mixed oxide catalyst based on molybdenum and bismuth, as described above, wherein the catalyst located closest to the inlet of the reactor has a molar ratio of bismuth to molybdenum that is lower than the molar ratio of bismuth to molybdenum that the catalyst located closest to the outlet of the reactor has. The method is carried out in the gas phase in the presence of oxygen.

[0039] In a second step, (meth)acrolein in the reaction product can be selectively oxidized in the gas phase in the presence of oxygen over a second mixed metal oxide catalyst having a different composition than the mixed oxide catalyst based on molybdenum and bismuth.

[0040] The second mixed metal oxide catalyst may be, for example, a solid catalyst comprising 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), antimony (Sb). When the second mixed metal oxide catalyst contains at least one additional element, molybdenum and vanadium or phosphorus are the main elements present. Preferably, the second mixed metal oxide catalyst comprises at least 40% by weight of molybdenum and vanadium and / or phosphorus, such as, for example, at least 50% by weight, at least 60% by weight, or at least 70% by weight of molybdenum and vanadium and / or phosphorus, based on the total weight of the non-oxygen elements in the second mixed metal oxide catalyst.

[0041] The second mixed metal oxide catalyst can be any commercially available mixed metal oxide catalyst for oxidation of (meth)acrolein to (meth)acrylic acid.

[0042] 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 from air or lattice oxygen of the mixed metal oxide catalyst. Preferably, the oxygen comes from air or lattice oxygen of the mixed metal oxide catalyst.

[0043] Purification of (meth)acrolein and / or (meth)acrylic acid may be achieved by one or more techniques known in the art, such as, for example, absorption using water or an organic solvent, extraction, fractional distillation, or melt crystallization.

[0044] Contemplated embodiments

[0045] The following envisioned examples illustrate the present invention but are not intended to limit the scope of the invention.

[0046] In a tubular reactor, the catalyst bed will be placed between the inlet of the reactor and the outlet of the reactor. The catalyst bed will consist of a mixed oxide catalyst based on molybdenum and bismuth comprising two zones. The composition of the mixed oxide catalyst based on molybdenum and bismuth is the same in the two zones, except that the amount of bismuth will vary. In the first zone closest to the inlet of the reactor, the molar ratio of bismuth to molybdenum is 0.6:12; and in the second zone closest to the outlet of the reactor, the molar ratio of bismuth to molybdenum is 1.2:12.

[0047] A reactant gas stream comprising 8.1 volume % propylene and 14.4 volume % oxygen was introduced into the inlet of the reactor.

[0048] It is expected that the amount of maleic anhydride will be significantly reduced, for example, by as much as 50%, compared to commercially available catalysts for the oxidation of propylene to form acrolein.

Claims

1. A reactor for producing (meth)acrolein and / or (meth)acrylic acid from reactants selected from the group consisting of propylene, isobutylene and tert-butyl alcohol, the reactor comprising an inlet for the reactants to enter the reactor, an outlet for the reaction products to leave the reactor and a catalyst bed arranged between the inlet and the outlet, wherein the catalyst bed comprises a mixed oxide catalyst based on molybdenum and bismuth, wherein the catalyst closest to the inlet of the reactor has a molar ratio of bismuth to molybdenum that is lower than the molar ratio of bismuth to molybdenum of the catalyst closest to the outlet of the reactor.

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

3. A reactor according to claim 1, wherein the catalyst bed comprises two or more zones within the catalyst, and the catalyst has a different composition within each zone, wherein the catalyst in the zone located closest to the inlet of the reactor has a molar ratio of bismuth to molybdenum that is lower than the molar ratio of bismuth to molybdenum of the catalyst in the zone located closest to the outlet of the reactor.

4. A reactor according to claim 3, wherein the catalyst bed comprises three or more zones within the catalyst, wherein the catalyst in one or more of the zones located 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 in the zone closest to the inlet and less than the molar ratio of bismuth to molybdenum in the catalyst in the zone closest to the outlet.

5. The reactor according to any one of the preceding claims, wherein the mixed oxide catalyst based on molybdenum and bismuth comprises a compound of formula I: Mo 12 Bi a X b Y c Z d O e Formula I in: 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 to 2.0; b = 1 to 12; c = 0.01 to 3; d = 0 to 20; and e is based on the oxidation states of the other elements in the catalyst.

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

12.

7. A reactor according to any one of the preceding claims, wherein the molar ratio of bismuth to molybdenum in the catalyst located closest to the inlet of the reactor ranges from 0.2:12 to 1.0:12, and the molar ratio of bismuth to molybdenum in the catalyst located closest to the outlet of the reactor ranges from 0.6:12 to 1.6:

12.

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

12.

9. A method comprising: A reactant selected from propylene, isobutylene and tert-butyl alcohol is oxidized in a reactor according to any one of claims 1 to 8, wherein the reaction product leaving the reactor comprises (meth)acrolein.

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

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

12. The method of claim 9, wherein the reactant is selected from isobutylene and tert-butyl alcohol, and the reaction product comprises methacrolein.

13. The method of claim 12, further comprising subjecting the methacrolein to producing acrylic acid.

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