Production of acrolein and / or acrylic acid from propylene and reduction of amount of high-boiling by-products

Abstract

A reactor for producing acrolein and / or acrylic acid from propylene includes an inlet for propylene 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 comprises a mixed oxide catalyst based on molybdenum and bismuth. The catalyst CAT inlet closest to the inlet of the reactor produces a lower amount of maleic anhydride relative to the total amount of acrolein and acrylic acid than the catalyst CAT outlet closest to the outlet of the reactor.

Description

Technical Field

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

[0002] Acrylic acid and its esters are important monomers for various polymers (including coatings, adhesives and superabsorbent polymers). Most of acrylic acid is produced via two-stage propylene oxidation, wherein propylene is first oxidized on a mixed oxide catalyst based on molybdenum (Mo) and bismuth (Bi) to mainly form acrolein, and acrylic acid is a minor product. Acrolein is then oxidized on a mixed oxide catalyst based on molybdenum and vanadium (V) to produce 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. These by-products can be removed via distillation, extraction, melt crystallization or their combination. However, removing these by-products increases the cost and complexity of the method.

[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. In the two 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 can reduce the amount of by-products formed in the production of acrolein and / or acrylic acid from propylene. Summary of the invention

[0005] The present invention relates to a reactor and a method for preparing acrolein and / or acrylic acid from propylene, and a reactor and a method for producing acrylic acid from acrolein.

[0006] According to one aspect of the invention, a reactor for producing acrolein and / or acrylic acid from propylene comprises an inlet for propylene to enter the reactor, an outlet for the 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 CAT closest to the inlet of the reactor 入口 The catalyst CAT closest to the outlet of the reactor 出口 In contrast, lower amounts of maleic anhydride are produced relative to the total amount of acrolein and acrylic acid.

[0007] Another aspect of the present invention includes a process for preparing acrolein and / or acrylic acid from propylene, the process comprising oxidizing propylene in a reactor, the reactor comprising an inlet for propylene to enter the reactor, an outlet for the 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 CAT closest to the inlet of the reactor 入口 The catalyst CAT closest to the outlet of the reactor 出口 In contrast, lower amounts of maleic anhydride are produced relative to the total amount of acrolein and acrylic acid. 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 expression of numerical ranges by endpoints includes all numbers subsumed within the 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 the understanding of 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.

[0010] 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.

[0011] 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 the disclosure of definitions (to the extent not inconsistent with any definitions specifically provided in this disclosure) and general knowledge in the art.

[0012] One aspect of the present invention relates to a reactor for producing acrolein and / or acrylic acid from propylene.

[0013] The reactor comprises an inlet for propylene to enter the reactor, an outlet for the 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.

[0014] As used herein, the term "reaction product" includes the desired product, including acrolein and / or acrylic acid, as well as 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.

[0015] Preferably, the mixed oxide catalyst based on molybdenum and bismuth comprises a compound of formula I:

[0016] Mo 12 Bi a X b Y c Z d O e Formula I

[0017] in:

[0018] X is at least one element selected from the group consisting of iron, cobalt and nickel;

[0019] 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;

[0020] Z is at least one element selected from the group consisting of silicon, aluminum, titanium, tin and zirconium;

[0021] a=0.1 to 2.0;

[0022] b = 1 to 12;

[0023] c = 0.01 to 3;

[0024] d = 0 to 20; and

[0025] e is based on the oxidation states of the other elements in the catalyst.

[0026] 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 propylene feed, but also affect the recovery of acrylic acid and the need to remove by-products to prepare certain grades of 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.

[0027] Without being bound by theory, it is believed that the heavy by-products are associated with 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 allylic radical which can then react with another allylic radical to form 1,5-hexadiene.

[0028] This reaction competes with the reaction of allyl radicals to form acrolein.

[0029]

[0030] In the catalyst bed of the present invention, the mixed oxide catalyst based on molybdenum and bismuth CAT closest to the inlet of the reactor is 入口 The mixed oxide catalyst CAT based on molybdenum and bismuth is located closest to the outlet of the reactor. 出口 Different. CAT 入口 With CAT 出口 Compared to producing lower amounts of maleic anhydride relative to acrolein and acrylic acid, CAT 出口 Preferably with CAT 入口 This means that when measured independently of each other, the activity of 出口 At the same propylene conversion rate, CAT 入口 A lower amount of maleic anhydride is produced compared to the total amount of acrolein and acrylic acid in the reaction product. As used herein, "comparable propylene conversion" means that CAT 入口 and CAT 出口 The difference in propylene conversion of CAT is less than 5%. 入口 and CAT 出口The difference in propylene conversion between the two reactions is less than 3%, and more preferably less than 2%. This can be quantitatively measured by setting up two identical experiments, differing in catalyst and temperature and / or contact time to achieve comparable propylene conversion, and measuring the concentrations of maleic anhydride, acrolein, and acrylic acid in the reaction products, and calculating the ratio of maleic anhydride to the total amount of acrolein and acrylic acid according to the following equation:

[0031]

[0032] In order to 入口 and CAT 出口 The reaction products achieved in different ratios of maleic anhydride to the total amount of acrolein and acrylic acid, CAT 入口 and CAT 出口 They may differ in at least one property or variable selected from composition, size, shape, method of preparation, carrier, concentration (eg, amount of diluent), and the like.

[0033] For example, the way the catalyst is prepared may result in different catalytic activities. The preparation methods may differ, for example, in the order of addition of the components (or elements), mixing temperature and time, drying method, calcination temperature and time, atmosphere, etc. Due to the difference in the preparation method, two catalysts with the same nominal composition may have different catalytic activities and / or selectivities.

[0034] The composition of the catalyst can vary based on the ratio of selected elements (eg, the molar ratio of bismuth to molybdenum), the addition or removal of elements, and the like.

[0035] The structure of the catalyst or support form can also alter the catalytic activity and / or selectivity. For example, a catalyst formed on a spherical catalyst may have a different catalytic activity / selectivity than a catalyst of similar composition formed in an annular shape.

[0036] Preferably, CAT 入口 and CAT 出口 Varies based on the composition of the catalyst.

[0037] The catalyst bed may contain a mixed oxide catalyst based on molybdenum and bismuth from CAT 入口 To CAT 出口 In the gradient composition, the catalyst closest to the inlet of the reactor (i.e., CAT 入口 ) can produce a catalyst that is closer to the reactor outlet (i.e., CAT 出口) lower ratio of maleic anhydride to the total amount of acrolein and acrylic acid. The gradient composition can vary linearly between the inlet and outlet of the reactor or can vary nonlinearly between the inlet and outlet of the reactor. Such a gradient composition can be achieved, for example, by varying the relative amounts of the components within the catalyst. For example, the molar ratio of bismuth to platinum can be kept relatively constant near the inlet of the reactor and then rapidly increased toward the outlet. Alternatively, at the CAT 入口 and CAT 出口 The gradient between is the gradient of element composition except bismuth and molybdenum.

[0038] In another embodiment, the catalyst bed may include two or more zones within the molybdenum and bismuth based mixed oxide catalyst, wherein each zone produces a different ratio of maleic anhydride compared to the total amount of acrolein and acrylic acid in the reaction product. 入口 The molar ratio of bismuth to molybdenum in the zone closest to the reactor outlet (i.e., CAT 出口 ) in a zone having a molar ratio of bismuth to molybdenum. Alternatively, each zone in the catalyst may have a different chemical formula Mo 12 Bi a X b Y c Z d O e .

[0039] The catalyst bed may comprise three or more zones within a mixed oxide catalyst based on molybdenum and bismuth, for example, CAT1 (where CAT1 = CAT 入口 ), CAT2, etc. to CAT n (CAT n =CAT 出口 and n is the number of zones), wherein each zone comprises a catalyst producing maleic anhydride in a different ratio compared to the total amount of acrolein and acrylic acid in the reaction product. When the catalyst bed comprises three or more zones in a mixed oxide catalyst based on molybdenum and bismuth, the catalyst bed closest to the inlet of the reactor (CAT1 or CAT2) is preferably a catalyst having a catalyst bed ... 入口 ) zone and the zone closest to the reactor outlet (CAT n or CAT 出口 ) in one or more zones between the zones (e.g., CAT2 to CAT n-1 ) can produce a greater ratio of maleic anhydride to the total amount of acrolein and acrylic acid than the catalyst located in the zone closest to the inlet (CAT1 or CAT 入口 ) to the total amount of acrolein and acrylic acid, and is less than that produced by the catalyst (CAT) located in the zone closest to the outlet of the reactor. n or CAT 出口) is the ratio of maleic anhydride produced to the total amount of acrolein and acrylic acid.

[0040] Preferably, the catalyst bed comprises two or more zones within the mixed oxide catalyst based on molybdenum and bismuth.

[0041] Preferably, the ratio of maleic anhydride to the total amount of acrolein and acrylic acid ranges from 250 ppm to 10,000 ppm, wherein the ratio of maleic anhydride to the total amount of acrolein and acrylic acid is calculated in parts per million (ppm) by the above formula.

[0042] Preferably, the amount of maleic anhydride and the total amount of acrolein and acrylic acid produced by the catalyst located closest to the inlet of the reactor ranges from 250 ppm to 5,000 ppm, and more preferably from 250 ppm to 4,000 ppm.

[0043] Preferably, the amount of maleic anhydride and the total amount of acrolein and acrylic acid produced by the catalyst located closest to the outlet of the reactor ranges from 2,000 ppm to 10,000 ppm, and more preferably from 2,000 ppm to 8,000 ppm.

[0044] Another aspect of the present invention relates to a process for preparing acrolein from propylene, the process comprising oxidizing propylene in a reactor, the reactor comprising an inlet for introducing propylene into the reactor, an outlet for the reaction product to leave the reactor and a catalyst bed arranged 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 CAT located closest to the inlet of the reactor 入口 The catalyst CAT located closest to the reactor outlet 出口 Compared to having a lower ratio of maleic anhydride compared to the total amount of acrolein and acrylic acid in the reaction product. The process is carried out in the gas phase in the presence of oxygen.

[0045] In a second step, 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, wherein the second mixed metal oxide catalyst has a different composition than the mixed oxide catalyst based on molybdenum and bismuth.

[0046] The second mixed metal oxide catalyst can be, for example, a solid catalyst comprising oxides of molybdenum (Mo) and vanadium (V). The second mixed metal oxide catalyst can also comprise at least one additional element selected from tungsten (W), copper (Cu), iron (Fe), antimony (Sb) and phosphorus (P). When the second mixed metal oxide catalyst comprises at least one additional element, molybdenum and vanadium are the main metal elements present. Preferably, the second mixed metal oxide catalyst comprises at least 40 weight % of molybdenum and vanadium, such as at least 50 weight %, at least 60 weight %, or at least 70 weight % of molybdenum and vanadium, based on the total weight of the metals in the second mixed metal oxide catalyst.

[0047] The second mixed metal oxide catalyst can be any commercially available mixed metal oxide catalyst for the oxidation of acrolein to acrylic acid.

[0048] In the selective oxidation reaction to form acrolein and / or acrylic acid, oxygen can be present in the form of purified oxygen, oxygen from air, or lattice oxygen of a mixed metal oxide catalyst. Preferably, the oxygen comes from air or lattice oxygen of a mixed metal oxide catalyst.

[0049] Purification of acrolein and / or acrylic acid may be achieved by one or more techniques known in the art, such as absorption using water or an organic solvent, extraction, fractional distillation, or melt crystallization.

[0050] Contemplated embodiments

[0051] The following envisioned examples illustrate the present invention but are not intended to limit the scope of the invention.

[0052] 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, wherein the first zone is about one-third of the volume of the catalyst bed and the second zone is about two-thirds of the volume of the catalyst bed. The catalysts will be provided by different sources and have different production ratios of maleic anhydride to acrolein / acrylic acid due to having different compositions and being produced by different methods. The catalyst that produces a lower production ratio of maleic anhydride to total acrolein / acrylic acid will have a ratio of about 2500 ppm. At a conversion rate similar to the first catalyst, i.e. within 2%, the catalyst that produces a higher production ratio of maleic anhydride to total acrolein / acrylic acid will have a ratio of about 4300 ppm.

[0053] In a first experiment according to the present invention, the catalyst having a lower production ratio of maleic anhydride to total acrolein / acrylic acid will be located in the first zone closest to the inlet, while the catalyst having a higher production ratio of maleic anhydride to total acrolein / acrylic acid will be located in the second zone closest to the outlet.

[0054] In a second comparative experiment, the catalyst having a higher production ratio of maleic anhydride to acrolein / acrylic acid would be located in the first zone closest to the inlet, while the catalyst having a lower production ratio of maleic anhydride to acrolein / acrylic acid would be located in the second zone closest to the outlet.

[0055] A reactant gas stream comprising 8.1 vol% propylene and 14.4 vol% oxygen was introduced into the inlet of the reactor. In order to obtain similar conversions, the temperature in the reactor was adjusted so that the overall conversions for each experiment were within 2% of each other.

[0056] The first experiment was expected to produce significantly less maleic anhydride than the second experiment.

Claims

1. A reactor for producing acrolein and / or acrylic acid from propylene, the reactor comprising an inlet for propylene to enter the reactor, an outlet for 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 CAT closest to the inlet of the reactor 入口 The catalyst CAT closest to the outlet of the reactor 出口 In contrast, lower amounts of maleic anhydride are produced compared to the total amount of acrolein and acrylic acid.

2. The reactor according to claim 1, wherein the CAT 入口 The ratio of maleic anhydride to the total amount of acrolein and acrylic acid is less than that used for CAT 出口 The ratio of maleic anhydride to the total amount of acrolein and acrylic acid.

3. A reactor according to any one of the preceding claims, wherein CAT 入口 With CAT 出口 Differing in at least one property or variable selected from composition, size, method of preparation, carrier and concentration.

4. The reactor of claim 1, wherein the catalyst bed comprises a gradient composition, wherein the composition of the catalyst ranges from CAT 入口 To CAT 出口 change.

5. The reactor of claim 1, wherein the catalyst bed comprises two or more zones, wherein the catalyst located in the first zone comprises CAT 入口 , and the catalyst in the second zone comprises CAT 出口 .

6. The reactor of claim 5, wherein the catalyst bed comprises three or more zones, wherein the ratio of maleic anhydride to the total amount of acrolein and acrylic acid produced by the catalyst in one or more zones between the zone closest to the inlet and the zone closest to the outlet is greater than that produced by the catalyst CAT in the zone closest to the inlet. 入口 The ratio of maleic anhydride produced to the total amount of acrolein and acrylic acid is less than that produced by the catalyst CAT in the zone closest to the outlet of the reactor. 出口 The ratio of maleic anhydride produced to the total amount of acrolein and acrylic acid.

7. 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; 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.

8. The reactor according to any one of the preceding claims, wherein the molybdenum and bismuth based mixed oxide catalyst produces a ratio of maleic anhydride to the total amount of acrolein and acrylic acid in the range of 250 ppm to 10,000 ppm.

9. A reactor according to any one of the preceding claims, wherein CAT 入口 The ratio of maleic anhydride produced to the total amount of acrolein and acrylic acid ranged from 250 ppm to 5,000 ppm, and CAT 出口 The ratio of maleic anhydride produced to the total amount of acrolein and acrylic acid ranged from 2,000 ppm to 10,000 ppm.

10. The reactor according to claim 9, wherein CAT 入口 The ratio of maleic anhydride produced to the total amount of acrolein and acrylic acid ranged from 250 ppm to 4,000 ppm, and CAT 出口 The ratio of maleic anhydride produced to the total amount of acrolein and acrylic acid ranged from 2,000 to 8,000.

11. A method comprising: Propylene is oxidized in a reactor according to any one of claims 1 to 10, wherein the reaction product leaving the reactor comprises acrolein.

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

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