JPH042582B2 - - Google Patents

Description

[Detailed description of the invention]

This invention produces unsaturated acids such as acrylic acid and methacrylic acid in high yield by reacting unsaturated aldehydes such as acrolein and methacrolein with molecular oxygen in the high-temperature gas phase in the presence of an improved catalyst. It's about how to do it. Conventionally unsaturated aldehydes, such as acrolein,
There are many known methods for producing corresponding unsaturated acids, such as acrylic acid and methacrylic acid, by reacting methacrolein with molecular oxygen in the presence of a catalyst in a high-temperature gas phase, and the catalysts used in this process. However, even though a catalyst has been proposed to be useful for both the production of acrylic acid and the production of methacrylic acid, there are There is a large difference in the yield of the target product, unsaturated acid, and the yield of methacrylic acid is significantly lower than that of acrylic acid. The reason why oxidizing methacrolein to produce methacrylic acid does not produce the same results as producing acrylic acid by oxidizing acrolein is that methacrolein has a highly reactive methyl group that is easily oxidized. This is partly due to the fact that it has a branched methyl group, and it is difficult to selectively oxidize only the aldehyde group while suppressing the oxidation of the methyl group of the branch. Furthermore, even if the catalyst has relatively high selectivity to methacrylic acid, when the reaction rate of methacrolein increases, the selectivity to methacrylic acid decreases, resulting in a low yield of methacrylic acid. Therefore, in recent years, there has been a strong desire to develop a catalyst that can produce unsaturated acids, particularly methacrylic acid, in high yield over a long period of time. Catalysts that have been proposed mainly for the production of methacrylic acid, such as JP-A No. 50-82013,
JP-A-50-123619, JP-A-50-135020, JP-A-51-65713, JP-A-51-115413
No. 52120, Japanese Patent Application Laid-open No. 52-52-
Molybdenum proposed in No. 57117 etc.
Catalysts containing phosphorus, alkali metals, vanadium, etc. give relatively favorable results in the production of methacrylic acid, but they also have problems such as the reaction rate of methacrolein, the selectivity and yield of methacrylic acid, the reaction temperature (optimal reaction temperature), etc. There is still room for improvement in this aspect. Therefore, the inventors first conducted Mo-P-V-
Mo-P-V-K/Cs-Ag/Te-O catalyst (Japanese Unexamined Patent Publication No. 55-31006) is used as a catalyst that can improve the K/Cs-O catalyst.
Ca-V-Cu-As-K(Cs)-Ta(B, Bi, Fe,
proposed a Sb)-O-based catalyst in which oxycarboxylic acids, glycols, and saccharides were mixed during preparation (Japanese Patent Application Laid-open No. 1983-6243). However, without being satisfied with this catalyst, we have developed a practical catalyst that can industrially produce methacrylic acid in high yield by maintaining both the methacrolein reaction rate and methacrylic acid selectivity at high values. He conducted intensive research with this aim. As a result, a heteropolyacid composition containing phosphorus, molybdenum, copper and arsenic and an arsenate and/or arsenite of an element selected from the group consisting of boron, aluminum, lead, bismuth and chromium are combined. The mixed catalyst makes it possible to achieve the above objectives, increasing both the conversion rate of methacrolein and the selectivity of methagrilic acid at low reaction temperatures.
In particular, by maintaining the selectivity of methacrylic acid at a high value,
Knowing that methacrylic acid can be produced with high yield,
I arrived at this invention. This invention relates to a method for producing an unsaturated acid by reacting an unsaturated aldehyde with molecular oxygen in the presence of a catalyst in a high-temperature gas phase. (B) an arsenate and/or arsenite of an element selected from the group consisting of boron, aluminium, lead, bismuth and chromium; It relates to a method for producing acids. In this invention, component (A) phosphorus, molybdenum,
A heteropolyacid composition containing copper and arsenic can be represented by formula (1). Mo _a P _b Cu _c As _d O _e ...(1) [In the formula, Mo is molybdenum, P is phosphorus, Cu is copper,
As represents arsenic, O represents oxygen, and subscripts a to e represent the number of atoms, where a = 12, b = 0.5 to 5, preferably 0.9 to 3, and c = 0.005 to 3, preferably 0.01.
~1, d is 0.0001 to 2, preferably 0.001 to 1,
e is a value naturally determined by the valence of each element. ] The heteropolyacid composition represented by formula (1) includes tungsten, iron, antimony, cobalt, zinc, Zirconium, calcium, tin, titanium,
palladium, tantalum, cerium, vanadium,
There is no problem even if it contains small amounts of magnesium, silver, etc. For preparing the heteropolyacid composition represented by formula (1), a conventionally known method for preparing a heteropolyacid catalyst containing phosphorus, molybdenum, copper, and arsenic is appropriately employed. An example of the preparation method is shown below. Compounds containing each component element are mixed in the presence of water and dissolved or dispersed, the resulting mixed solution or slurry is evaporated to dryness, and the dried product is dried to form the formula (1).
A heteropolyacid composition represented by: Typical compounds containing each element include molybdenum trioxide, phosphomolybdic acid, phosphoric acid, copper oxide, copper carbonate, copper nitrate, arsenic acid, arsenite, arsenic oxide, etc. be able to. There is no particular restriction on the order of mixing the compounds containing each component element. The temperature for mixing is generally 20
~100℃ is appropriate, and the mixing time is not particularly limited as long as it can be mixed uniformly, but after mixing,
Aging is recommended for ~20 hours. Dry matter is 100
1 to 1 at a temperature around ℃, generally 80 to 130℃
Drying for 20 hours is preferred. In this invention, the arsenic compounds such as arsenate and arsenite as component (B) are generally BAsO ₄ ,
AlAsO ₄ , Pb(AsO ₂ ) ₂ , BiAsO ₄ and α−
_CrAsO4 is used. Of course, a plurality of these may be used. These arsenic compounds are produced by combining an arsenic-containing compound such as arsenic acid or sodium arsenate with a compound containing boron, aluminum, copper, lead, bismuth, etc., such that an arsenic compound having the atomic ratio represented by the above chemical formula is formed. It can be easily prepared by changing the ratio of raw materials used, adding water, evaporating to dryness or filtering the resulting precipitate, and then heat-treating. For example, boron arsenate, which is expressed as BAsO ₄ with an atomic ratio of boron and arsenic of 1:1, is produced by adding water to boric acid in an equal molar amount to arsenic acid, evaporating to dryness with sufficient stirring, and then heating the mixture to about 400°C. How to fire with,
It can be prepared by heating diammonium hydrogen arsenate and boric acid at about 400°C, and the other arsenic compounds mentioned above can also be prepared by the same method. In addition, in this invention, a heteropolyacid composition containing phosphorus, molybdenum, copper and arsenic as the component (A) and an arsenic composition containing an element selected from the group consisting of boron, aluminum, lead, bismuth and chromium as the component (B). The mixing ratio with acid salt and/or arsenite is
Although it differs slightly depending on the type of arsenic compound in (B), (A)
From the viewpoint of catalytic activity, it is preferable that the amount of arsenic compound (B) be 0.5 to 0.0001 mol, preferably 0.3 to 0.001 mol, per 12 gram atoms of molybdenum. Also, (A) and (B) may be mixed in any way as long as they can be mixed uniformly, but generally, with or without adding a small amount of water, a binder, etc.
A method of mechanical mixing using a mixer such as a kneader or a crusher is adopted, and the mixture is appropriately shaped and used. In this invention, the catalyst may be used alone or together with a carrier. As the carrier, any carrier conventionally known as a carrier for catalysts for producing acrylic acid, methacrylic acid, etc. can be used, such as diatomaceous earth, alumina, silica, titanium oxide, silica sol, silicon carbide, graphite, etc. I can do it. Note that the carrier may be added at the time of catalyst production. There are no particular restrictions on the shape and size of the catalyst particles, and they may be shaped into pellets, etc. depending on the conditions of use.
It is preferable to use it by molding it into a desired size and shape, such as granules, and grading it to give it a certain mechanical strength. In this invention, the molecular oxygen used in the reaction may be pure oxygen gas, but it is not necessary to have particularly high purity, so it is generally economical and convenient to use air. It is also preferred to use a diluent gas in the reaction together with molecular oxygen and acrolein or methacrolein. As the diluent gas, any gas that does not have a negative effect on this reaction, such as nitrogen gas, carbon dioxide gas, or water vapor, can be used. Among them, water vapor not only has the effect of improving the selectivity of acrylic acid and methacrylic acid, but also improves the catalytic activity. It is best to carry out the reaction in the presence of water vapor, as this has the effect of sustaining the reaction. Further, the acrolein or methacrolein used in the reaction does not need to be of particularly high purity like molecular oxygen, and for example, those obtained by oxidation reaction of propylene or isobutylene may be used as they are. Although this invention can be carried out in any of fluidized bed, moving bed, fixed bed, etc., the catalyst used in this invention can improve the reaction rate of acrolein or methacrolein and acrylic acid or methacrylic acid at relatively low reaction temperature and short contact time. It is generally advantageous to carry out the process in a fixed bed because it has the advantage of having a high selectivity and being able to maintain catalyst activity over a long period of time. Further, in the present invention, the reaction may be carried out under normal pressure, increased pressure, reduced pressure, etc., but it is generally convenient to carry out the reaction under normal pressure. Also, the reaction temperature is 200
~400℃, preferably 250-350℃, especially 260-320
°C is preferred. Further, the appropriate contact time is 0.1 to 10 seconds, preferably 0.5 to 5 seconds. For the reaction, it is preferable to use a mixed gas of acrolein or methacrolein and molecular oxygen, generally air, further adding water vapor.The composition of the mixed gas is 1 mole of acrolein or methacrolein, 0.5 to 7 moles of oxygen, preferably 1
It is preferred that the amount of water vapor is between 0.5 and 30 mol, preferably between 1 and 10 mol. In addition, conventionally known methods such as condensation and solvent extraction can be used to recover the desired product, acrylic acid or methacrylic acid. Next, examples and comparative examples will be shown. The reaction rate (%), selectivity (%) and yield (%) in the examples follow the following definitions. Reaction rate (%) = Number of moles of acrolein or methacrolein reacted/Number of moles of acrolein or methacrolein supplied x 100 Selectivity (%) = Number of moles of acrylic acid or methacrylic acid produced/Number of moles of acrolein or methacrolein reacted Number of moles of x 100 Yield (%) = Number of moles of acrylic acid or methacrylic acid produced/Number of moles of acrolein or methacrolein supplied x 100 Example 1 Molybdenum trioxide [MoO ₃ ] 240 g, 85% phosphoric acid [ 16.0 g of H ₃ PO ₄ ], 1.1 g of copper oxide [CuO], and 19.8 g of 60% arsenic acid [H ₃ AsO ₄ ] aqueous solution were dissolved in 1.5 g of water, aged at 30°C for 20 hours, and dried in a drum dryer. After evaporation to dryness, further drying at 120℃ for 20 hours,
Composition (A) [Mo ₁₂ P ₁ Cu _0.1 As _0.6 ] (Oxygen etc. are omitted)
I got it. Further, a small amount of water was added to a 60% arsenic acid [H ₃ AsO ₄ ] aqueous solution and an equimolar amount of boric acid [H ₃ BO ₃ ], and the mixture was evaporated to dryness. The obtained solid was heat-treated (calcined) in air at 350°C for 20 hours to obtain boron arsenate [BAsO ₄ ]. Next, 100 g of composition (A) and 0.24 g of boron arsenate were mixed uniformly using a crusher, and the mixture was molded into pellets of 4 mmφ x 4 mmH to obtain a catalyst. The atomic ratio of the catalyst component elements of the catalyst thus obtained (oxygen etc. are omitted) is Mo:P:
Cu:As:B=12:1:0.1:0.63:0.03. 10 ml (14.6 g) of the catalyst prepared in this manner was filled into a glass U-shaped reaction tube with an inner diameter of 8 mm, and a mixed gas containing 5% methacrolein, 10% oxygen, 30% water vapor, and 55% nitrogen by volume 400ml/min
The contact reaction was carried out for 1 hour at a flow rate of 280°C. The results of the contact reaction are shown in Table 1. Comparative Example 1 A catalytic reaction was carried out under the same reaction conditions as in Example 1 using the same composition (A) as in Example 1 as a catalyst without mixing boron arsenate. The results of the contact reaction are shown in Table 1. Example 2 The atomic ratio of the catalyst component elements was Mo:P:Cu:As:B= 12:
A catalyst of 1:0.1:0.7:0.1 was prepared and a catalytic reaction was carried out under the same reaction conditions as in Example 1. The results of the contact reaction are shown in Table 1. Examples 3-4 Compositions listed in Table 1 in a similar manner to Example 1
(A) was prepared. In addition, a small amount of water was added to a 60% arsenic acid [H ₃ AsO ₄ ] aqueous solution and an equimolar amount of aluminum nitrate [Al( _{NO 3} ) 3.9H ₂ O], and the resulting solid was evaporated to dryness. Heat treatment (calcination) was performed in air at 230°C for 20 hours to obtain aluminum arsenate [AlAsO ₄ ]. Next, in the same manner as in Example 1, composition (A) and aluminum arsenate [AlAsO ₄ ] were mixed to prepare catalysts having the compositions shown in Table 1. Table 1 shows the results of a catalytic reaction conducted under the same reaction conditions as in Example 1. Examples 5-6 Compositions listed in Table 1 in a similar manner to Example 1
(A) was prepared. In addition, lead hydroxide carbonate [2PbCO ₃ Pb(OH) ₂ ] was added to a 60% arsenic [H ₃ AsO ₄ ] aqueous solution with some water so that the atomic ratio of arsenic and lead was 2:1. After addition and mixing, the mixture was evaporated to dryness, and the resulting solid was heat-treated (calcined) in air at 700°C for 20 hours to obtain lead arsenate [Pb(AsO ₂ ) ₂ ]. Next, in the same manner as in Example 1, composition (A) and lead arsenate [Pb(AsO ₂ ) ₂ ] were mixed to prepare a catalyst having the composition shown in Table 1. Table 1 shows the results of a catalytic reaction conducted under the same reaction conditions as in Example 1. Examples 7-8 Compositions listed in Table 1 in a similar manner to Example 1
(A) was prepared. In addition, bismuth nitrate [4BiNO ₃ (OH) ₂・BiO (OH)] was added to a 60% arsenic [H ₃ AsO ₄ ] aqueous solution with some water so that the atomic ratio of arsenic and bismuth was 1:1. After adding and mixing, evaporate to dryness,
The obtained solid was heat-treated (calcined) in air at 400°C for 20 hours to obtain bismuth arsenate [BiAsO ₄ ]. Next, in the same manner as in Example 1, composition (A) and bismuth arsenate [BiAsO ₄ ] were mixed to prepare catalysts having the compositions shown in Table 1. Table 1 shows the results of a catalytic reaction conducted under the same reaction conditions as in Example 1. Examples 9-10 The compositions listed in Table 1 were prepared in the same manner as in Example 1.
(A) was prepared. In addition, an equimolar chromium nitrate [Cr(NO ₃ ) _{3.9H 2} O] aqueous solution was added to a 60% arsenic acid [H ₃ AsO ₄ ] aqueous solution, and after evaporating to dryness, the obtained solid was heated in air at 400°C. Heat treated (baked) for 20 hours at α-
_CrAsO4 was obtained. Next, the composition was prepared in the same manner as in Example 1.
(A) and chromium arsenate [α-CrAsO ₄ ] were mixed to prepare a catalyst having the composition shown in Table 1. Table 1 shows the results of a catalytic reaction conducted under the same reaction conditions as in Example 1. Comparative Examples 2 to 7 In the same manner as the preparation method of composition (A) of Example 1,
In addition to molybdenum trioxide, phosphoric acid, copper oxide, and arsenic acid, boric acid [H ₃ BO ₃ ], aluminum nitrate [Al(NO ₃ ) ₃・9H ₂ O], and lead carbonate hydroxide [2PbCO ₃・Pb (OH) ₂ ], bismuth nitrate [4BiNO ₃
(OH) ₂・BiO(OH)] or chromium nitrate [Cr
(NO ₃ ) ₃ ·9H ₂ O] and without mixing the arsenic compound as component (B), catalysts having the compositions shown in Table 2 were prepared. Table 2 shows the results of a catalytic reaction conducted under the same reaction conditions as in Example 1.

【table】

【table】

[Table] Example 11 10 ml of the same catalyst as in Example 1 was filled into a glass U-shaped reaction tube with an inner diameter of 8 mm, and the volume was filled with 6% acrolein, 10% oxygen, 30% water vapor, and 54% nitrogen.
% mixed gas at a flow rate of 400ml/min at 280℃
The catalytic reaction was carried out at a temperature of . As a result, the reaction rate of acrolein was 96.2%, and the selectivity of acrylic acid was
The yield of acrylic acid was 93.7% and 90.1%.

Claims (1)

[Claims] 1. A method for producing an unsaturated acid by reacting an unsaturated aldehyde with molecular oxygen in the presence of a catalyst in a high-temperature gas phase, which contains (A) phosphorus, molybdenum, copper and arsenic as a catalyst; and (B) an arsenate and/or arsenite of an element selected from the group consisting of boron, aluminum, lead, bismuth and chromium. A method for producing unsaturated acids.