Catalyst for the production of maleic anhydride and method for producing maleic anhydride

Abstract

To provide a catalyst for producing maleic anhydride that is a catalyst for producing maleic anhydride by oxidizing n-butane, which has high catalytic activity and can achieve both a low reaction temperature and a high yield of maleic anhydride.SOLUTION: Provided is a catalyst for producing maleic anhydride, which is a catalyst for producing maleic anhydride by oxidizing n-butane, and contains composite oxide of vanadium and phosphorus, iron, and at least one element M selected from niobium, molybdenum, yttrium, cerium and hafnium, and in which the mole ratio M / Fe of the element M and iron is 0.05 to 0.45. A method for producing maleic anhydride in which this catalyst for producing maleic anhydride is used.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a catalyst for producing maleic anhydride by oxidizing n-butane, and to a method for producing maleic anhydride using this catalyst. [Background technology]

[0002] Conventionally, composite oxide catalysts (VPO catalysts) consisting of tetravalent vanadium and pentavalent phosphorus have been known as catalysts for selectively oxidizing carbon-4 hydrocarbons such as butane, butene, and butadiene, particularly the saturated hydrocarbon n-butane, in the gas phase to produce maleic anhydride.

[0003] Patent Document 1 describes using an iron compound as a co-catalyst in combination with a vanadium-phosphorus composite oxide catalyst to enhance its catalytic activity. Furthermore, Patent Document 2 describes using a VPO catalyst, which consists of a vanadium-phosphorus composite oxide, to oxidize n-butane to produce maleic anhydride, and then promoting the VPO catalyst with niobium, antimony, and / or bismuth. Patent Document 2 also describes a VPO catalyst promoted with Nb and Fe as a comparative catalyst, but the Nb / Fe molar ratio of this catalyst is 1.7, meaning that Nb is used in excess of Fe. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-227545 [Patent Document 2] Special Publication No. 2018-530417 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] For the production of maleic anhydride, a catalyst with high catalytic activity and the ability to produce maleic anhydride in higher yield at lower reaction temperatures is desirable. However, VPO catalysts alone have low activity, requiring high reaction temperatures and resulting in low maleic anhydride yields.

[0006] While the catalyst described in Patent Document 1, which uses Fe as a co-catalyst in a VPO catalyst, can increase the activity of the VPO catalyst and lower the reaction temperature, it suffers from the problem of low maleic anhydride yield.

[0007] The catalyst described in Patent Document 2, which combines Nb, Sb, and / or Bi with the VPO catalyst, can obtain a high yield of maleic anhydride while maintaining high activity and a low reaction temperature, but further improvements are desired. Furthermore, while Patent Document 2 describes a comparative catalyst consisting of a VPO catalyst activated with Nb and Fe, with an Nb / Fe molar ratio of 1.7, this comparative catalyst cannot achieve both the low reaction temperature and high maleic anhydride yield described in Patent Document 2.

[0008] The present invention aims to solve the problems of the prior art described above and to provide a catalyst for producing maleic anhydride by oxidizing n-butane, which has high catalytic activity and can achieve both a low reaction temperature and a high maleic anhydride yield, and a method for producing maleic anhydride using this maleic anhydride production catalyst. [Means for solving the problem]

[0009] As a result of repeated studies to solve the above problems, the inventors of the present invention have found that by using iron as the first additive element and a specific element M as the second additive element in the VPO catalyst, and by setting the molar ratio M / Fe of the second additive element M to the first additive element Fe within a predetermined range, it is possible to enhance catalytic activity in the production of maleic anhydride from n-butane and achieve both a low reaction temperature and a high maleic anhydride yield, thus completing the present invention. In other words, the gist of this invention is as follows:

[0010] [1] A catalyst for producing maleic anhydride by oxidizing n-butane, comprising a composite oxide of vanadium and phosphorus, iron, and at least one element M selected from niobium, molybdenum, yttrium, cerium, and hafnium, wherein the molar ratio M / Fe of element M to iron is 0.05 to 0.45, the catalyst for producing maleic anhydride.

[0011] [2] The catalyst for producing maleic anhydride according to [1], wherein the element M is cerium and / or hafnium.

[0012] [3] The catalyst for producing maleic anhydride according to [1] or [2], wherein the iron content is 1.3 to 3.0% by mass based on the composite oxide of vanadium and phosphorus.

[0013] [4] The catalyst for producing maleic anhydride according to any one of [1] to [3], wherein the content of element M is 0.1 to 3.0% by mass based on the composite oxide of vanadium and phosphorus.

[0014] [5] A method for producing maleic anhydride, comprising oxidizing n-butane in the presence of the catalyst for producing maleic anhydride according to any one of [1] to [4] to produce maleic anhydride. [Advantages of the Invention]

[0015] According to the present invention, in the production of maleic anhydride by oxidizing n-butane, the catalytic activity can be enhanced, and both a low reaction temperature and a high maleic anhydride yield can be achieved. That is, the catalyst for producing maleic anhydride of the present invention is excellent in catalytic activity, so that maleic anhydride can be produced at a reaction temperature lower than that of the prior art. The side reaction is suppressed by the decrease in the reaction temperature, and as a result, maleic anhydride can be obtained in a high yield. [Embodiments for Carrying Out the Invention]

[0016] The present invention will be described in detail below, but the present invention is not limited to the following description and can be modified and implemented as appropriate without departing from the spirit of the invention. In this specification, when a "~" is used to enclose numerical values ​​or physical properties, it is intended to include the values ​​before and after it.

[0017] [Catalyst for the production of maleic anhydride] The catalyst for producing maleic anhydride of the present invention is a catalyst for producing maleic anhydride by oxidizing n-butane, and is characterized by comprising a vanadium-phosphorus composite oxide (hereinafter sometimes referred to as "VPO catalyst"), iron, and at least one element M selected from niobium, molybdenum, yttrium, cerium, and hafnium, wherein the molar ratio M / Fe of element M to iron is 0.10 to 0.45. In the following, Fe and element M may be referred to as "additive elements."

[0018] In this invention, the M / Fe molar ratio corresponds to the M / Fe molar ratio of the iron compound and the compound containing element M (hereinafter sometimes referred to as "M compound") used in the production of the maleic anhydride catalyst of this invention. However, in the production of the maleic anhydride catalyst of this invention, the amount used is approximately equal to the composition ratio of the produced catalyst.

[0019] <Additional elements> The catalyst for producing maleic anhydride according to the present invention is a VPO catalyst to which Fe and element M are added as additive elements in a predetermined ratio.

[0020] In the maleic anhydride production catalyst of the present invention, the M / Fe molar ratio being in the range of 0.05 to 0.45 is an important constituent element of the present invention. If the M / Fe molar ratio is less than 0.05 or greater than 0.45, the effects of lower reaction temperature and higher maleic anhydride yield due to improved catalytic activity according to the present invention cannot be obtained. The M / Fe molar ratio is particularly preferably 0.10 to 0.40.

[0021] Element M is one or more of the following: niobium (Nb), molybdenum (Mo), yttrium (Y), cerium (Ce), and hafnium (Hf). From the viewpoint of improving catalytic activity, it is particularly preferable to use Ce and / or Hf among these.

[0022] The Fe content in the maleic anhydride production catalyst of the present invention is preferably 1.3 to 3.0% by mass, particularly 1.4 to 2.0% by mass, relative to the VPO catalyst, within the above M / Fe molar ratio range, and the element M content is preferably 0.1 to 3.0% by mass, particularly 0.3 to 2.0% by mass, relative to the VPO catalyst, within the above M / Fe molar ratio range. If the amount of element M exceeds the above range, the maleic anhydride yield decreases significantly and the reaction temperature increases significantly. Conversely, if M is absent, the maleic anhydride yield decreases. Furthermore, the above-mentioned Fe and element M content also corresponds to the mass percentage of the raw material compounds charged during the production of the maleic anhydride production catalyst of the present invention. However, in the production of the maleic anhydride production catalyst of the present invention, the amount charged is approximately equal to the composition ratio of the produced catalyst.

[0023] [Method for producing a catalyst for maleic anhydride] The maleic anhydride production catalyst of the present invention can be manufactured in the same manner as a conventional VPO catalyst, except that, in the production of the VPO catalyst, the Fe compound and the M compound are present in the reaction solution in a predetermined ratio, i.e., within the range that satisfies the aforementioned M / Fe molar ratio.

[0024] Specifically, the catalyst for producing maleic anhydride according to the present invention can be produced by preparing a mixture containing a vanadium compound, a phosphorus compound, an iron compound, an M compound, and an organic solvent, recovering a catalyst precursor from the reaction product obtained by heating this mixture under reflux at a predetermined temperature, and then drying and calcining this catalyst precursor.

[0025] <Vanadium compounds> As the vanadium compound, one or more of pentavalent vanadium compounds such as vanadium pentoxide, ammonium metavanadate, and vanadium oxyhalides (vanadium salts) can be used. However, the most common raw material is vanadium pentoxide. Vanadium pentoxide is used as it is or after being pulverized if it is a commercially available product.

[0026] <Phosphorus compound> As the phosphorus compound, phosphoric acid is used. As phosphoric acid, commercially available products can be used. For example, it is desirable to use anhydrous phosphoric acid with a purity of 98 to 100% by mass. However, phosphoric acid with a purity of 85% by mass, which is easily available and inexpensive on an industrial scale, can also be sufficiently used.

[0027] <Iron compound> Examples of the iron compound include ferrous chloride (II), ferrous acetate (II), ferrous oxalate (II), ferric phosphate (III), etc. These can be used individually or in combination of two or more.

[0028] <M compound> Examples of the M compound include oxides, hydroxides, carbonates, halides, oxalates, nitrates, acetates, formates, butyrates, benzoates, ammonium salts, sulfates, sulfides, etc. of Nb, Mo, Y, Ce, and Hf. These can be used individually or in combination of two or more.

[0029] <Organic solvent> The organic solvent used in this invention is preferably one that possesses reducing power itself, and examples of organic solvents with reducing power include those having functional groups that are easily oxidized. Typically, organic solvents having alcoholic hydroxyl groups are preferred. Among such organic solvents, aliphatic alcohols having 3 to 6 carbon atoms, such as butanol (butyl alcohol), 2-propanol, 2-methylpropanol, and hexanol, and benzyl alcohol are typical. Two or more of the above organic solvents may be used in mixture form. For example, it is preferable to use a mixture of aliphatic alcohols having 3 to 6 carbon atoms and benzyl alcohol, which has a higher reducing power. It is also possible to include reducing agents such as hydrazine or oxalic acid in the organic solvent.

[0030] Of these organic solvents, isobutyl alcohol is preferred from the viewpoint of the catalytic activity of the resulting catalyst, and a mixed solvent of isobutyl alcohol and benzyl alcohol is more preferred. In this mixed solvent, the proportion of isobutyl alcohol is preferably 85-95% by volume, and the proportion of benzyl alcohol is preferably 15-5% by volume.

[0031] The amount of organic solvent is not particularly limited, but it is preferable to use it in an amount of 70 to 90% by mass of the total amount of the final reaction system. When the amount of organic solvent is within this range, mixing is easier and the homogeneity of the mixture is higher, resulting in higher activity of the resulting catalyst.

[0032] When using a mixture of benzyl alcohol, which has high reducing power, it is preferable from the viewpoint of the catalytic activity of the resulting catalyst to use a benzyl alcohol:vanadium compound (molar ratio) of typically 0.02:1 to 2:1, and particularly 0.5:1 to 1.5:1.

[0033] <Other ingredients> The reaction mixture may contain seed crystals of the desired catalyst, if necessary. There are no particular restrictions on the amount of seed crystals used when they are present.

[0034] <Heating under reflux> The temperature and time for heating the reaction mixture under reflux are appropriately selected depending on the type of organic solvent used. Typically, the temperature is in the range of 80 to 200°C, and it is particularly preferable to heat it at a temperature near the boiling point of the organic solvent used. For example, when isobutyl alcohol is used as the main solvent, the preferred temperature for reflux heating is around 100 to 110°C. The duration of reflux heating varies depending on the reflux heating conditions, but it is usually preferable to heat for 1 to 20 hours after adding phosphoric acid to the reaction system.

[0035] This heating reflux process reduces vanadium and reacts it with phosphoric acid, an iron compound, and an M compound to obtain a reaction product containing a tetravalent vanadium and phosphorus complex oxide, as well as iron and element M.

[0036] [Recovery of catalyst precursors and production of catalysts] After the reaction is carried out as described above, the reaction system is cooled, the product is separated from the reaction solution using conventional solid-liquid separation methods, washed with a solvent such as alcohol if necessary, and then dried. The catalyst precursor obtained in this way is then mixed with a binder component or a support component, dried, and activated by heating, or the precursor is preheated and activated, then mixed with a binder component or a support component, dried, and then molded as necessary depending on the reactor configuration before being used as a catalyst.

[0037] Examples of heating activation conditions for the catalyst include heating and calcination in a nitrogen atmosphere or an atmosphere of nitrogen and air mixed in an appropriate ratio, or heating and calcination in a reaction gas atmosphere containing the raw material n-butane. By heating in such an atmosphere at around 400-700°C, the catalyst can be activated and at least a portion of the complex oxide vanadyl hydrogen phosphate 1 / 2 hydrate in the precursor can be converted into divanadyl pyrophosphate, which is the catalytically active component, and used as a catalyst.

[0038] [Method for producing maleic anhydride] The method for producing maleic anhydride using the catalyst for maleic anhydride production of the present invention can be carried out according to conventional methods.

[0039] n-butane, a raw material for maleic anhydride, can be easily obtained by separation from natural gas or from naphtha cracking products.

[0040] The oxidation reaction can take place in a fluidized bed, a fixed bed, or a transport bed. Air or a molecular oxygen-containing gas is used as the oxidizing agent. The n-butane concentration is usually 0.1 to 10% by volume, preferably 0.3 to 5% by volume, relative to the total amount of the oxygen-containing gas, and the oxygen concentration is approximately 10 to 30% by volume, relative to the total amount of n-butane and oxygen-containing gas.

[0041] The reaction temperature is usually 300-500°C, preferably 350-450°C, but by using the maleic anhydride production catalyst of the present invention, it is possible to efficiently carry out the oxidation reaction at a relatively low temperature of about 390-415°C. The reaction pressure is usually atmospheric pressure or 0.05-10 kg / cm². 2 It is performed under G-pressure. [Examples]

[0042] The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples unless it exceeds its gist. The various manufacturing conditions and evaluation result values ​​in the following examples have meaning as preferred upper or lower limits in embodiments of the present invention, and the preferred range may be defined by a combination of the aforementioned upper or lower limits and the values ​​of the following examples or the values ​​of the examples themselves.

[0043] [Example 1] <Catalyst Manufacturing> 3g vanadium pentoxide (V2O5), 0.309g ferrous oxalate hydrate (Fe(C2O4)·H2O), ammonium oxalate hydrate (NH4(NbO(C2O4)2(H2O)) n0.106 g of

[0044] [Example 2] In Example 1, ammonium oxalate hydrate (NH4(NbO(C2O4)2(H2O) n The catalyst was prepared in the same manner as in Example 1, except that the amount of added )) was changed to 0.162 g.

[0045] [Example 3] In Example 1, ammonium oxalate hydrate (NH4(NbO(C2O4)2(H2O) n The catalyst was prepared in the same manner as in Example 1, except that the amount of added )) was changed to 0.212 g.

[0046] [Example 4] In Example 1, ammonium oxalate hydrate (NH4(NbO(C2O4)2(H2O) n The catalyst was prepared in the same manner as in Example 1, except that the amount of added )) was changed to 0.265 g.

[0047] [Example 5] In Example 1, ammonium oxalate hydrate (NH4(NbO(C2O4)2(H2O) n The catalyst was prepared in the same manner as in Example 1, except that the amount of added )) was changed to 0.318 g.

[0048] [Example 6] In Example 1, the addition amount of ferrous oxalate hydrate (Fe(C2O4)·H2O) was changed to 0.275 g, and ammonium oxalate niobate(V) hydrate (NH4(NbO(C2O4)2(H2O) n )) was changed to 0.144 g, and the catalyst was produced in the same manner as in Example 1 except for this change.

[0049] [Example 7] In Example 1, the addition amount of ferrous oxalate hydrate (Fe(C2O4)·H2O) was changed to 0.343 g, and ammonium oxalate niobate(V) hydrate (NH4(NbO(C2O4)2(H2O) n )) was changed to 0.180 g, and the catalyst was produced in the same manner as in Example 1 except for this change.

[0050] [Example 8] In Example 1, instead of ammonium oxalate niobate(V) hydrate (NH4(NbO(C2O4)2(H2O) n )), 0.436 g of ammonium molybdate(IV) ((NH4)6Mo7O 24 ·4H2O) was added, and the catalyst was produced in the same manner as in Example 1 except for this change.

[0051] [Example 9] In Example 1, instead of ammonium oxalate niobate(V) hydrate (NH4(NbO(C2O4)2(H2O) n )), 0.653 g of ammonium molybdate(IV) ((NH4)6Mo7O 24 ·4H2O) was added, and the catalyst was produced in the same manner as in Example 1 except for this change.

[0052] [Example 10] In Example 1, instead of ammonium oxalate niobate(V) hydrate (NH4(NbO(C2O4)2(H2O) n )), 0.871 g of ammonium molybdate(IV) ((NH4)6Mo7O 24 ·4H2O) was added, and the catalyst was produced in the same manner as in Example 1 except for this change.

[0053] [Example 11] In Example 1, ammonium oxalate hydrate (NH4(NbO(C2O4)2(H2O) n The catalyst was prepared in the same manner as in Example 1, except that 0.112 g of yttrium nitrate (Y(NO3)3·6H2O) was added instead of ).

[0054] [Example 12] In Example 1, ammonium oxalate hydrate (NH4(NbO(C2O4)2(H2O) n The catalyst was prepared in the same manner as in Example 1, except that 0.159 g of yttrium nitrate (Y(NO3)3·6H2O) was added instead of ).

[0055] [Example 13] In Example 1, ammonium oxalate hydrate (NH4(NbO(C2O4)2(H2O) n The catalyst was prepared in the same manner as in Example 1, except that 0.0755 g of cerium oxalate (Ce2(C2O4)3·9H2O) was added instead of ).

[0056] [Example 14] In Example 1, ammonium oxalate hydrate (NH4(NbO(C2O4)2(H2O) n The catalyst was prepared in the same manner as in Example 1, except that 0.116 g of cerium oxalate (Ce2(C2O4)3·9H2O) was added instead of ).

[0057] [Example 15] In Example 1, ammonium oxalate hydrate (NH4(NbO(C2O4)2(H2O) n The catalyst was prepared in the same manner as in Example 1, except that 0.151 g of cerium oxalate (Ce2(C2O4)3·9H2O) was added instead of ).

[0058] [Example 16] In Example 1, ammonium oxalate hydrate (NH4(NbO(C2O4)2(H2O) nThe catalyst was prepared in the same manner as in Example 1, except that 0.0996 g of hafnium sulfide (Hf(SO4)2) was added instead of ).

[0059] [Example 17] In Example 1, ammonium oxalate hydrate (NH4(NbO(C2O4)2(H2O) n The catalyst was prepared in the same manner as in Example 1, except that 0.130 g of hafnium sulfide (Hf(SO4)2) was added instead of ).

[0060] [Example 18] In Example 1, ammonium oxalate hydrate (NH4(NbO(C2O4)2(H2O) n The catalyst was prepared in the same manner as in Example 1, except that 0.166 g of hafnium sulfide (Hf(SO4)2) was added instead of ).

[0061] [Example 19] In Example 1, ammonium oxalate hydrate (NH4(NbO(C2O4)2(H2O) n The catalyst was prepared in the same manner as in Example 1, except that 0.199 g of hafnium sulfide (Hf(SO4)2) was added instead of ).

[0062] [Example 20] In Example 1, the amount of ferrous oxalate hydrate (Fe(C2O4)·H2O) added was changed to 0.258 g, and ammonium oxalate hydrate (NH4(NbO(C2O4)2(H2O)) was added. n The catalyst was prepared in the same manner as in Example 1, except that 0.166 g of hafnium sulfide (Hf(SO4)2) was added instead of ).

[0063] [Comparative Example 1] In Example 1, ammonium oxalate hydrate (NH4(NbO(C2O4)2(H2O) n The catalyst was prepared in the same manner as in Example 1, except that the )) was not added.

[0064] [Comparative Example 2] In Example 1, the amount of ferrous oxalate hydrate (Fe(C2O4)·H2O) added was changed to 0.206 g, and ammonium oxalate hydrate (NH4(NbO(C2O4)2(H2O)) was added. n The catalyst was prepared in the same manner as in Example 1, except that 0.199 g of hafnium sulfide (Hf(SO4)2) was added instead of ).

[0065] [Catalytic activity: Evaluation of maleic anhydride yield] 0.9 g of the catalyst obtained in each example and comparative example was packed into a 3 / 8-inch diameter stainless steel reaction tube. A mixed gas with n-butane concentration of 0.78 vol%, oxygen concentration of 20 vol%, nitrogen concentration of 7 vol%, and helium concentration of 72.21 vol% was passed through this reaction tube at a rate of 17.0 mL / min while the tube was heated to 440°C and stabilized for 24 hours. The composition of the mixed gas was changed to n-butane concentration of 4 vol%, oxygen concentration of 20 vol%, nitrogen concentration of 7 vol%, and helium concentration of 69 vol%, and the temperature was changed from 440°C to 380°C in 15°C increments while the gas was passed through at a rate of 8.6 mL / min. After stabilizing at each temperature for 2 hours, the gas at the outlet of the reaction tube was sampled and analyzed by gas chromatography to determine the reaction temperature at which the n-butane conversion rate was 85%, and the maximum maleic anhydride yield within the measured temperature range.

[0066] These evaluation results are shown in Table 1, along with the ratio of the amount of additional elements added to the amount of added iron in each catalyst, expressed in moles (M / Fe).

[0067] [Table 1]

[0068] Table 1 shows that by using a VPO catalyst that includes iron plus an additional element M within a certain range, maleic anhydride can be produced in high yield even at low reaction temperatures.

Claims

1. A catalyst for oxidizing n-butane to produce maleic anhydride, It comprises a vanadium-phosphorus composite oxide, iron, and at least one element M selected from niobium, molybdenum, yttrium, cerium, and hafnium. The molar ratio of element M to iron, M / Fe, is between 0.05 and 0.

45. The iron content is 1.5 to 2.0% by mass relative to the vanadium-phosphorus composite oxide. A catalyst for producing maleic anhydride, wherein the content of element M is 0.4 to 1.8% by mass relative to the vanadium-phosphorus composite oxide.

2. The catalyst for producing maleic anhydride according to claim 1, wherein the element M is cerium and / or hafnium.

3. A method for producing maleic anhydride, comprising oxidizing n-butane in the presence of the maleic anhydride production catalyst described in claim 1 or 2 to produce maleic anhydride.

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