JP2000246108A - Metal oxide catalyst and production of acrylic acid using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain a high yield of acrylic acid by using a metal oxide catalyst prepared from the metallic elements Mo, V, Sb, A (A is Nb and/or Ta) and B (B is one or more elements selected from Ag, Zn, Sn, Pb, As, Cu, Tl and Se). SOLUTION: This metal oxide catalyst suitable for use in the production of acrylic acid by the vapor phase catalytic oxidation of propane contains the metallic elements Mo, V, Sb, A (A is Nb and/or Ta) and B (B is one or more elements selected from the group comprising Ag, Zn, Sn, Pb, As, Cu, Tl and Se). The preferred ratio among the metallic elements constituting the catalyst is represented by the formula MoVhSbiAjBk [where A and B have the same meanings as the above, (h) and (i) are each 0.01-1.5, i/h=0.3 to 1, (j) is 0.001-3.0 and (k) is 0.0001-0.05].

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a metal oxide catalyst used in a method for producing acrylic acid by gas phase catalytic oxidation of propane, a method for producing the same, and a method for producing acrylic acid using the metal oxide catalyst. Things.

[0002]

2. Description of the Related Art Acrylic acid is conventionally produced by a two-stage oxidation method in which propylene and oxygen are contact-oxidized to produce acrolein, and then acrolein and oxygen are contact-oxidized. On the other hand, the practical use of a one-step oxidation method that can significantly reduce the production cost as compared with the two-step oxidation method, that is, a method of producing acrylic acid by using propane as a starting material and reacting it with oxygen in a one-step reaction Research is also being conducted in various places. The study of the practical use of the one-stage propane oxidation method has been focused on the development of a catalyst that exhibits excellent conversion and selectivity in the reaction, and many proposals on such a catalyst have been made. That is, Japanese Unexamined Patent Publication No. Hei 10-45664, which relates to a method for producing acrylic acid by a one-step oxidation method of propane, discloses that Mo, V, and Sb are essential metals, and Nb, Ta, W, T
Basically, a four-component metal oxide catalyst comprising a metal selected from the metal group consisting of i, Zr, Cr, Fe and the like has been proposed, and the same applies to JP-A-9-316023. A four-component metal oxide catalyst comprising a metal is disclosed. As a catalyst having a higher conversion and selectivity in the acrylic acid synthesis reaction than the above four-component metal oxide catalyst, JP-A-10-120617 discloses a four-component catalyst disclosed in JP-A-10-45664. A basically five-component metal oxide catalyst obtained by further impregnating a metal oxide catalyst with a solution containing As, P or an alkali metal is disclosed. According to such a five-component metal oxide catalyst, a yield of about 20 to about 20 is obtained by a one-stage oxidation method of propane.
Acrylic acid can be synthesized at 25%.

[0003] Japanese Patent Application Laid-Open No. 10-28862 discloses that
It mainly relates to a catalyst for the catalytic oxidation reaction of alkane and ammonia for nitrile synthesis.
A catalyst having the same structure as the five-component metal oxide catalyst disclosed in 120617, that is, specifically, the four-component metal oxide catalyst disclosed in Japanese Patent Application Laid-Open No. H10-45664, furthermore, Mo, W, Zr, Cr, Zr, Ti, N
b, Ta, Fe, P, Si, a metal oxide catalyst impregnated with a solution containing one or more elements selected from alkali metals, alkaline earth metals, and the like, and the catalyst is propane Is also applicable to the synthesis of acrylic acid from However, Japanese Patent Laid-Open No.
0-120617 or JP-A-10-28862
At present, the reaction yield of acrylic acid has not yet reached a level sufficient for the practical use of the one-stage oxidation of propane in the catalyst proposed in the publication.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have used a novel metal which has never been studied before as the fifth component metal, and Mo and Mo. , V, Sb and a five-component composite metal oxide catalyst comprising a metal element A (where A is Nb or Ta) have been found to provide a high acrylic acid yield, and have completed the present invention. Was. That is, the present invention
Metal elements Mo, V, Sb, A (A is at least one element selected from the group consisting of Nb and Ta) and B (B is A
g, Zn, Sn, Pb, As, Cu, Tl, and Se), which is a metal oxide catalyst. The preferred ratio of each metal element constituting the catalyst is as follows. When the catalyst is represented by the following formula (I), h and i are each 0.01 to 1.5 and i / h = 0.3 to
1, j is 0.001 to 3.0, and k is 0.00
01 to 0.05. MoVhSbiAjBk (I) (wherein, A and B are the same as described above.) Hereinafter, the present invention will be described in more detail.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred methods for producing the metal oxide catalyst of the present invention include the following methods. That is, a method for producing a metal oxide catalyst comprising the following steps (1) and (2), wherein a compound containing the metal element B as a constituent element is mixed with another metal component in one of the steps. Is the way. Step (1): a step of reacting V ⁺⁵ and Sb ⁺³ at a temperature of 70 ° C. or higher in an aqueous medium in the presence of Mo ⁺⁶ Step (2): a reaction product obtained in the step (1) To
Step of adding and uniformly mixing a compound having the metal element A as a constituent element, and calcining the obtained mixture. In the step (1), Sb ⁺³ , V ⁺⁵ and Mo ⁺⁶ It has been confirmed that an oxidation-reduction reaction occurs to generate Sb ⁺⁵ . As the V ⁺⁵ compound having V ⁺⁵ as a constituent element used in the above step (1), ammonium metavanadate or vanadium pentoxide is preferable, and the Sb ⁺³ compound having Sb ⁺³ as a constituent element is preferably Antimony oxide or antimony acetate is preferable, and examples of the Mo ⁺⁶ compound having Mo ⁺⁶ as a constituent element include ammonium molybdate, molybdenum oxide, and molybdic acid. Ammonium.

Mo ⁺⁶ in the redox reaction of step (1)
The preferred proportions of the compound, V ⁺⁵ compound and Sb ⁺³ compound are Mo, V and Sb which constitute the desired catalyst.
Is a ratio such that the following composition formula (Ia) is obtained. V
⁺⁵ compound and Sb ⁺³ compound are used in an atomic ratio of S
b ^{+ 3} : V ^{+ 5} = (0.3-1): 1. If the ratio of Sb ⁺³ is less than 0.3, the selectivity for acrylic acid is low, while if it exceeds 1, the conversion of acrolein is low. When h and i in the following composition formula are less than 0.01 or more than 1.5, the conversion of acrolein and the selectivity for acrylic acid in the acrylic acid production reaction are inferior. MoVhSbi (Ia) wherein A and B are the same as above. H and i
Is 0.01 to 1.5 and i / h = 0.3 to 1 respectively. ) More preferred h and i are 0.1-1.

The above Mo ⁺⁶ compound, V ⁺⁵ compound and Sb
^{In addition to the +3} compound, a compound containing the metal element B as a constituent element (hereinafter sometimes referred to as a B compound) may be added to the aqueous medium, or the next step (2), namely, the metal element A
(Where A is at least one element selected from the group consisting of Nb and Ta) as a constituent element (hereinafter sometimes referred to as A compound) by the above Mo ⁺⁶ compound, V ⁺⁵ compound and S
In the step of mixing with the compound b ^+3,
The compounds may be mixed with them. As described above, the metal element B includes Ag, Zn, Sn, Pb, As, Cu, and Tl.
And Se, which are at least one element selected from the group consisting of Se, such compounds having B as a constituent element include silver compounds such as silver nitrate, silver acetate and silver carbonate, zinc compounds such as zinc nitrate and zinc oxide, Tin compounds such as stannous chloride and stannic chloride; lead compounds such as lead acetate and lead chloride; arsenic compounds such as arsenic trioxide and arsenic oxide; copper such as copper nitrate, cupric oxide and cuprous oxide Compounds, thallium compounds such as thallous nitrate and thallous nitrate, selenic acid, selenous acid, selenic chloride and the like. The amount of the B compound used is such that when Mo is 1, B is 0.0001 to 0.05 in terms of the atomic ratio of the metal in the obtained catalyst. The ratio of the metal element B when Mo is 1 in the catalyst is 0.000
If it is less than 1, the effect of the addition will not be exhibited, while if it exceeds 0.05, the yield of acrylic acid will decrease.

The preferred amount of the metal compound in the aqueous medium is 3 to 30 parts by weight in total of three metal compounds per 100 parts by weight of water. If the total amount of the three metal compounds exceeds 30 parts by weight, a part of the V compound or the Mo compound becomes insoluble, and the oxidation-reduction reaction tends to be incomplete. The above reaction does not proceed unless heated at 70 ° C. or higher, and the preferred reaction temperature is around the boiling point of the aqueous medium. The reaction time is preferably about 10 to 30 hours. S
In order to promote the redox reaction among the three of b ⁺³ , V ⁺⁵ and Mo ⁺⁶ , oxygen gas is blown into the reaction solution in step (1), or after the redox reaction has progressed to some extent. It is preferable to drop hydrogen peroxide into the reaction solution. Instead of oxygen gas, a gas containing oxygen gas such as air may be used. The preferred oxygen gas concentration in the oxygen gas-containing gas is 0.5 vol% or more, and more preferably 1 to 20 vol%. And particularly preferably, 2 to 15
vol% (hereinafter abbreviated as%). The preferred blowing rate (flow rate) depends on the amount of the oxidation-reduction reaction solution,
If the reaction solution volume is about 200 ml to 500 ml, 3 to 12
Liter / Hr is preferred. The time for blowing the oxygen-containing gas into the reaction solution is preferably 4 hours or more. A more preferred blowing time is 5 to 10 hours. If the blowing time of the oxygen gas-containing gas is less than 4 hours, the activity of the obtained catalyst may be low. In dropping the hydrogen peroxide, it is preferable to use a hydrogen peroxide solution having a hydrogen peroxide concentration of about 0.01 to 35% by weight, and a preferable dropping amount of the hydrogen peroxide is 1 in terms of molar ratio to 1 of Sb. , 0.2 to 1.
2. The preferred temperature of the reaction solution to be dropped at this time is 80 to 100 ° C. Further, the dropping of hydrogen peroxide may be completed within a short time, or may be performed for a long time.

The degree of progress of the reaction is determined by the pentavalent S in the reaction solution.
b is quantitatively analyzed, and can be determined by comparing the amount thereof with the amount of trivalent Sb initially charged. That is, to the obtained reaction solution, a 1N oxalic acid aqueous solution 10 times or more the amount of the solution was added, and Sb
After sedimentation and separation of only Sb, pentavalent Sb can be quantitatively analyzed by titrating the precipitate with hydroiodic acid. The valences of Mo and V in the reaction solution can be determined by measurement of an electron spin resonance spectrum or the like.

In the step (2), a Nb compound or a Ta compound is added to a dispersion containing Mo, V and Sb, which are reaction products of the above-mentioned reaction, or a dried product thereof, and uniformly mixed. An Nb compound or a Ta compound may be used in combination. Further, as described above, the B compound may be added together with the Nb compound or the Ta compound. Examples of the Nb compound or Ta compound include niobium oxide, niobic acid, tantalum oxide, and tantalic acid. The Nb compound or Ta compound may be used in a form in which these are dispersed in water, but more preferably in the form of an aqueous solution of oxalate using oxalic acid or the like. When Nb is added to the reaction product of step (1) in the form of an aqueous solution of its oxalate, it is particularly preferable that ammonium ions coexist in the aqueous solution, and the ratio of ammonium ions and oxalate ions to Nb Is a molar ratio of 1 to Nb, 2 to 7 ammonium ions and 4 to 1 oxalate ions.
2 is preferred. As the compound providing an ammonium ion, ammonia or an aqueous solution thereof is preferable. Nb
The amount of the compound or the Ta compound used (or the total amount thereof when used in combination) is such that Nb or Ta is 0.001 assuming that Mo is 1 in the atomic ratio of the metal in the obtained catalyst.
It is an amount that becomes to 3.0. If the ratio of Nb or Ta when Mo is 1 in the catalyst is less than 0.001, the catalyst will be deteriorated. On the other hand, if it exceeds 3.0, the catalyst will have low activity and the conversion of propane will be poor.

The mixture of the metal compounds obtained by the above-mentioned operation is converted into the metal oxide used as the catalyst of the present invention, if necessary, by drying it by a method such as evaporation to dryness or spray drying, followed by baking treatment. You. Such firing is preferably performed in two stages. That is,
First, in the presence of oxygen gas, for example, in air, 250 to 3
It is preferable to perform heating at 50 ° C. for 4 to 10 hours, and then perform firing at 500 to 660 ° C. for 1 to 3 hours in an inert gas. Confirmation of the content of the metal element in the metal oxide obtained by the calcination can be performed by X-ray fluorescence analysis. The acrylic acid production catalyst obtained by the above method is preferably pulverized to an appropriate particle size to increase the surface area. As the pulverization method, any of a dry pulverization method and a wet pulverization method can be used. Examples of the device include a mortar and a ball mill. The preferred particle size of the present catalyst is 20 μm or less, more preferably 5 μm or less. The present catalyst can be used in a state of no carrier, but can also be used in a state of being supported on a carrier such as silica, alumina, silica-alumina and silicon carbide having an appropriate particle size.

The propane and oxygen gas, which are the raw materials for the production of acrylic acid, may be separately introduced into the reactor and mixed in the reactor, or they may be mixed in advance and introduced into the reactor. good. Examples of the oxygen gas include pure oxygen gas or air, and a gas obtained by diluting them with nitrogen, steam, or carbon dioxide. When using propane and air, the ratio of air to propane is preferably 30 times or less by volume, more preferably 0.2 to 0.2.
20 times. The preferred reaction temperature is from 300 to 600C, more preferably from 350 to 500C. Also,
The gas space velocity (hereinafter referred to as SV) is 300 to 5
000 / hr is appropriate. Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

[0013]

Example 1 (Production of catalyst 1) 6.15 g of ammonium metavanadate was added to 130 ml of distilled water in a 300 ml glass flask, and dissolved by heating under stirring, and 5.87 g of antimony trioxide was added. 30.9 g ammonium molybdate and 82 wt% selenic acid solution.
317 g were added. The mixture composed of the above components was heated and refluxed for 16 hours in a nitrogen gas atmosphere while rotating a stirrer at a rate of 360 rpm. Then, while continuing the heating and stirring, 40 g of a 1.71% by weight aqueous hydrogen peroxide solution was dropped into the reaction solution over 5 hours. The obtained blue colloidal dispersion liquid was cooled to room temperature, and oxalic acid 8.8 was added thereto.
A room temperature aqueous solution in which 2 g, 2.33 g of niobic acid, and 3.0 g of 28% by weight ammonia water were dissolved in 75 ml of distilled water was added. After the resulting mixture was vigorously stirred for 30 minutes, the water was gradually evaporated and finally dried at 120 ° C. The solid obtained by the above operation was fired at 280 ° C. for 5 hours, and then fired at 580 ° C. for 5 hours in a nitrogen gas atmosphere. The obtained catalyst was tableted, and further 16 to 30 times.
The material pulverized into a mesh was used in the following acrylic acid production test. The ratio of the constituent metals of the obtained catalyst was Mo / V
/Sb/Nb/Se=1.0/0.3/0.23/0.
08 / 0.008.

(Acrylic acid production test 1) The above catalyst 1.5
ml was filled in a 10 mmφ quartz reaction tube. The reaction tube was heated to 390 ° C., and a mixed gas consisting of 4.5% of propane, 7.1% of oxygen gas, 25% of nitrogen gas and 63.4% of steam was added thereto at a rate of SV = 1800 / hr (contact time). (2 seconds) to synthesize acrylic acid. The conversion of propane was 58.9%, the selectivity for acrylic acid was 54.6%, and the yield of acrylic acid was 32.1%. The propane conversion, the acrylic acid yield, and the like were calculated by the following formulas (all calculated by moles).・ Propane conversion (%) = (supply propane−unreacted propane) ÷ supply propane ・ Acrylic acid selectivity (%) = formed acrylic acid 生成 (supply propane−unreacted propane) ・ Acrylic acid yield (%) = propane Conversion x Acrylic acid selectivity

[0015]

EXAMPLE 2 Copper nitrate (divalent) (trihydrate) was used in place of 0.317 g of 82% by weight selenic acid solution in Example 1.
0.127 g was used, and instead of the hydrogen peroxide solution and the method of dropping it in Example 1, 40 g of 1.54 wt% hydrogen peroxide solution was dropped in 5 minutes. Otherwise in the same manner as in Example 1, a metal oxide catalyst having a particle size of 16 to 30 mesh was obtained. The ratio of the constituent metals of the obtained catalyst was Mo / V / Sb / Nb / Cu = 1.0 / 0.3 /
0.23 / 0.08 / 0.003. Hereinafter, an acrylic acid production test was conducted in the same manner as in Example 1 using the above catalyst.

[0016]

Example 3 A catalyst was obtained in the same manner as in Example 2 except that 0.14 g of thallium nitrate (divalent) was used instead of copper nitrate in Example 2. The ratio of the constituent metals of the obtained catalyst was Mo / V / Sb / Nb / Tl = 1.0
/0.3/0.23/0.08/0.003.
Hereinafter, an acrylic acid production test was conducted in the same manner as in Example 1 using the above catalyst.

[0017]

Comparative Example 1 The fifth metal, Se, Cu or T
Except that l and the like were not used, all operations were carried out in the same manner as in the example to obtain a metal oxide catalyst having the following constitution. Mo / V / Sb / Nb = 1.0 / 0.3 / 0.23 /
0.08 Hereinafter, an acrylic acid production test was carried out using the above catalyst and in the same manner as in each of the above examples. The results of the acrylic acid production test of each of the above examples are as shown in Table 1. The unit of the numerical values in the table is%.

[0018]

[Table 1]

[0019]

The acrylic acid can be obtained in a high yield by using the metal oxide of the present invention as a catalyst in a one-stage gas phase catalytic oxidation reaction for synthesizing acrylic acid from propane.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C07C 51/21 C07C 51/21 57/055 57/055 A F term (Reference) 4G069 AA02 AA08 BC19A BC19B BC19C BC21A BC21B BC21C BC22A BC22B BC22C BC26A BC26B BC26C BC27A BC27B BC27C BC31A BC31B BC31C BC32A BC32B BC32C BC35A BC35B BC35C BC54A BC54B BC54C BC55A BC55B BC55C BC56A BC56B BC56C BC59A BC59C02B02 BC02B02 BC02B02A BA11 BA12 BA13 BA14 BA15 BA27 BA30 BA81 BC13 BC32 BE30 BS10 4H039 CA65 CC30

Claims (5)

[Claims] 1. A metal element Mo, V, Sb, A (A is Nb
And one or more elements selected from the group consisting of Ta and Ta) and B (B is Ag, Zn, Sn, Pb, As, Cu, T
one or more elements selected from the group consisting of l and Se)
A metal oxide catalyst which is essential. 2. A metal oxide catalyst wherein the proportion of the metal is a proportion represented by the following composition formula (I). MoVhSbiAjBk (I) (where A and B are the same as above. H and i
Are 0.01 to 1.5 and i / h = 0.3 to 1, j is 0.001 to 3.0, and k is 0.0001.
~ 0.05. ) 3. A method for producing acrylic acid, wherein the metal oxide catalyst according to claim 1 or 2 is used in producing acrylic acid by subjecting propane to catalytic oxidation in a gas phase. 4. A method for producing a metal oxide catalyst comprising the following steps (1) and (2), wherein a compound containing a metal element B as a constituent element is mixed with another metal component in any one of the steps. The method for producing a metal oxide catalyst according to claim 2, wherein: Step (1): a step of reacting V ⁺⁵ and Sb ⁺³ at a temperature of 70 ° C. or higher in an aqueous medium in the presence of Mo ⁺⁶ Step (2): a reaction product obtained in the step (1) To
A step of adding a compound having the metal element A as a constituent element, uniformly mixing the mixture, and firing the obtained mixture. 5. A method for producing acrylic acid, wherein a metal oxide catalyst obtained by the method according to claim 4 is used in producing acrylic acid by catalytically oxidizing propane in a gas phase.